Photodegradation of Pesticides on Plant and Soil …. Environmental Factors Affecting Soil...

Rev Environ Contam Toxicol 182:1–195 Springer-Verlag 2004

Photodegradation of Pesticideson Plant and Soil Surfaces

Toshiyuki Katagi

Contents

I. Introduction ....................................................................................................... 2II. Photophysical and Photochemical Processes ................................................... 3

A. Photophysical Processes .............................................................................. 3B. Photochemical Processes ............................................................................. 5

III. Factors Controlling Photolysis on Plant Surfaces ........................................... 10A. Environmental Factors ................................................................................. 10B. Illumination Conditions ............................................................................... 10C. Effect of Formulation .................................................................................. 12D. Anatomy of the Leaf ................................................................................... 13E. Wax Chemistry ............................................................................................. 14F. Photoinduced Reactions ............................................................................... 15

IV. Factors Controlling Photolysis on Soil Surfaces ............................................. 17A. Soil Components .......................................................................................... 17B. Environmental Factors Affecting Soil Properties ....................................... 19C. Mass Transport in Soil ................................................................................. 19D. Photic Depth in Soil .................................................................................... 21E. Effects of Soil Properties on Photolysis ...................................................... 22F. Photophysical and Photochemical Processes of Soil Components ............. 23

V. Atmospheric Oxygen Species .......................................................................... 29VI. Experimental Design and Kinetic Analysis ..................................................... 31

A. Light Source ................................................................................................. 31B. Photolysis Chambers .................................................................................... 32C. Kinetic Analysis ........................................................................................... 34

VII. Photodegradation of Pesticides in Model Systems .......................................... 35A. Soil Surface Models .................................................................................... 35B. Plant Surface Models ................................................................................... 36C. Photodegradation of Pesticides on Glass and Silica Gel Surfaces ............. 36D. Photodegradation of Pesticides in Organic Solvents and

Plant Model Systems ............................................................................... 47VIII. Photodegradation of Pesticides on Soil and Clay Surfaces ............................ 56

IX. Photodegradation of Pesticides on Plants ........................................................ 69Summary .................................................................................................................... 77

Communicated by George W. Ware

T. KatagiSumitomo Chemical Co., Ltd., Environmental Health Science Laboratory, 2-1 Takatsukasa4-Chome, Takarazuka, Hyogo 665-8555, Japan.

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Table Listing .............................................................................................................. 79Appendices ................................................................................................................. 129Directory of Pesticide Chemical Structures .............................................................. 130References .................................................................................................................. 157

I. Introduction

Sunlight photodegradation is one of the most destructive pathways for pesticidesafter their release into the environment. Plant surfaces, especially leaf surfaces,are the first reaction environment for a pesticide molecule after application, andspray drift would indirectly present a similar situation. Photolysis on soil sur-faces becomes important when a pesticide is directly applied to soil or not sig-nificantly intercepted by plants, providing that the leaf cover does not shade theground from sunlight. Because the foliar interception of pesticides depends onplant species and usually increases with their growth stage (Linders et al. 2000),the importance of soil photolysis is considered to be lessened when plants be-come mature. Spray drift after pesticide application or washoff from plants byrain is the indirect route by which a pesticide reaches the soil.

To elucidate the photodegradation profiles of pesticide in the environment,many investigators have focused on solution photolysis in organic solvents orin a dilute aqueous solution. The heterogeneity of soil and plant surfaces to-gether with the capricious transmission of sunlight onto these media also makesphotolysis on them more difficult to understand. Although there are many excel-lent reviews on photolysis of pesticides (Roof 1982; Miller and Zepp 1983;Choudhry and Webster 1985; Marcheterre et al. 1988; Parlar 1990; Wolfe et al.1990; Cessna and Muir 1991; Meallier 1999; Floesser-Mueller and Schwack2001; Burrows et al. 2002), photolysis on soil is still only partially understoodbecause of the limited number of investigations, whereas that on plants is mostlyspeculation derived from plant metabolism studies. Under these circumstances,photodegradation on soil and plant surfaces requires more examination, not onlyexperimentally but also theoretically, to reveal the mechanisms controlling pho-tophysical and photochemical processes in pesticides on solid phases and toapply such knowledge to better understand the dissipation profiles of pesticidesin the field.

This review first considers the background and basis of photophysics andphotochemistry relevant to the photodegradation of pesticides. Molecular excita-tion and deactivation processes together with subsequent chemical processes arediscussed, and reactivity toward active oxygen species is briefly summarized.Second, constituents of soil and plant surfaces are reviewed from the point ofview of the factors controlling photodegradation, together with meteorologicalfactors. After reviewing the experimental design of photodegradation on thesesurfaces, the analysis of experimental data in consideration of the photodegrada-tion mechanism is discussed briefly. Based on the literature survey, both modelsystems and the actual photodegradation in soil and plant systems are reviewed

Photodegradation of Pesticides 3

for every chemical class of pesticide. The chemical structure of each pesticide1

appearing in this review, together with a corresponding number in bold type, isprovided in the Appendices.

II. Photophysical and Photochemical ProcessesA. Photophysical Processes

The extent of sunlight photolysis is highly dependent on UV absorption profilesof the pesticide, the surrounding medium, and the emission spectrum of sunlight.Because the energy to break chemical bonds in pesticide molecules usuallyranges from 70 to 120 kcal mol−1, corresponding to light at wavelengths of250–400 nm (Watkins 1974), spectral irradiance of sunlight detected near theground becomes important in determining the photodegradation profiles of pes-ticide. By passing through the atmosphere, sunlight intensity significantly de-creases to about 10% in the troposphere, and no light is transmitted at wave-lengths from <290 to 295 nm, mainly due to absorption by ozone (Zepp andCline 1977; Parlar 1990). As a result, sunlight near the ground exhibits a maxi-mum at around 440–460 nm, and its intensity at the UV region responsiblefor photodegradation of pesticide becomes approximately 5%–6% of the totalintensity. There are many photophysical pathways of sunlight absorption (Fig.1) (Turro 1978; Roof 1982; Parlar 1990). When a photon passes close to apesticide molecule, molecular excitation occurs via interaction between the elec-tric field of a pesticide molecule and that of light at a time scale of femtosecondswithout a change of molecular geometry (Franck–Condon principle). Each pho-ton can activate only one molecule in the ground state (S0) with a certain proba-bility to the excited singlet state (Stark–Einstein rule), and usually the lowestexcited state (S1) is involved in further photoprocesses. Generally, pesticide mol-ecules exhibiting a UV-vis absorption spectrum at >290 nm have a substitutedaromatic moiety, sometimes being conjugated with the lone-pair electrons or theunsaturated bonds such as carbonyl or carbamoyl group, and hence π → π* orn → π* transition takes place upon irradiation.

There are three possible photophysical pathways from the S1 state: nonradia-tive internal conversion, emission of fluorescence, and intersystem crossing tothe excited triplet state (T1) (see Fig. 1). The first pathway means the relaxationfrom higher vibrational levels (�1012 sec−1) in the S1 state followed by decay toa lower electronic state with the same multiplicity (106–1012 sec−1). The secondone is a radiative deactivation process. The fluorescence spectrum is usuallyclose to a mirror image of that of absorption due to the Franck–Condon princi-ple but shifted to the red. The lifetime of fluorescence is very short (nanosec-

1All pesticides are identified by their common name and parenthetical identification number, andtheir structures are illustrated in the Appendices. Preceding the Appendices is a Directory of Pesti-cide Chemical Structures listing all pesticides in alphabetical order to aid the reader in locatingspecific structures.

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Fig. 1. Energy state diagram.

onds to microseconds) due to the transition between states with the same multi-plicity. The last pathway is a spin-forbidden process (S1 → T1), followed byslow radiationless deactivation or emission of phosphorescence. The T1 → S0

process is also spin-forbidden, and hence the lifetime of phosphorescence usu-ally becomes an order of milliseconds to 102 sec. The profiles of fluorescenceand phosphorescence spectra of pesticides, based on the literature survey, aresummarized in Table 1 (see table on page 80). Although there are many chemi-cal classes and either a solvent system or temperature difference in measuringspectra, their maximum wavelengths are located in the range of 280–450 and380–530 nm, respectively. Based on the following equation of conversion whereE and λ are the energy level and the emission wavelength, respectively (Gould1989b), the energy levels of the excited singlet (Es) and triplet (ET) states can beestimated to be 64–102 and 54–75 kcal mol−1 for these pesticides, respectively.

E (kcal mol−1) = 2.864 × 104/λ (nm)

Because intersystem crossing is facilitated by the presence of heavy atoms in amolecule, the fluorescence spectrum of a pesticide is usually difficult to measureat room temperature, but in such cases phosphorescence can be efficiently de-tected instead.

The foregoing consideration can also be applied to pesticide molecules in thesolid phase, but adsorption onto these media is most likely to affect the photo-physical processes. Molecular motion would be highly restricted, and interac-tions with these heterogeneous surfaces result in modification of their electronicstates. In this case, the reflectance spectrum of a pesticide gives more usefulinformation than an absorption spectrum, and this is described by the relation-


ship of Schuster and Kubelka-Munk (Parlar 1984) instead of the Beer–Lambertlaw.

F(R∞) = (1 − R∞)2/2R∞ = K/S

The diffuse reflectance, F(R∞), represents the radiation penetrating into the pow-der and resembles the usual transmission spectrum. R∞ is the ratio of reflectanceof a sample to that of a standard and thus the relative diffuse reflectance of aninfinitely thick layer compared to a nonabsorbing standard such as magnesiumoxide; K and S are the absorption and scattering coefficients, respectively. Ad-sorption can produce unequal displacement of the ground- and excited-state po-tential curves, which would result in a different vibronic band shape. Thus,spectral changes by adsorption are characterized by a spectral shift, changes ofextinction coefficient, broadening of absorption bands, and appearance of newbands (Wendlandt and Hecht 1966; Nicholls and Leermakers 1971; Parlar1984). Examples of spectral changes by adsorption of organic molecules includ-ing pesticides to silica gel and clays, listed in Table 2 (see table on page 85),are based on the literature survey. Both bathochromic (red) and hypsochromic(blue) shifts on adsorption have been reported, which are considered to dependon the type of an electronic transition. It is known that a blue shift almost alwaysoccurs with n → π* transition and often a red shift with π → π* transitions(Nicholls and Leermakers 1971). In the case of the former transitions, thechange of a nonpolar environment to polar causes more stabilization of theground state via hydrogen-bonding and dipole–dipole interactions than the ex-cited state, resulting in a blue shift. For π → π* transitions, the excited state ismore stabilized by polarization in the polar environment, resulting in a red shift.The alteration of emission spectrum by adsorption is likely, but the correspond-ing information is limited. Villemure et al. (1986) have reported the significantincrease of fluorescence intensity of paraquat (225) when adsorbed onto clays.Fluorescence with an emission maximum of 345 nm was very weak in aqueoussolution, but adsorption resulted in the increase of its intensity with a blue shiftby �20 nm. The increase of intensity is most likely to stem from an inhibitionof radiationless quenching by counteranion Cl− by intercalation of molecules of(225) into the interlayer of clays.

B. Photochemical Processes

Unless the energy of an excited-state molecule is lost as heat or emission oflight, it causes various types of chemical reactions in the excited molecule.There are two types of photochemical reactions, well known as “direct” and“indirect” photolysis (Roof 1982; Miller and Zepp 1983). Direct photolysismeans the photoreaction proceeds by absorbing light energy, whereas indirectphotolysis is defined as reaction of a ground-state molecule with the other ex-cited molecule or photochemically produced reactive species. The former indi-rect photolysis is called photosensitization or quenching, and the latter is a pho-toinduced reaction with a reactive oxygen species. The average rate of direct

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photolysis in a well-mixed system can be estimated by using the GCSOLARprogram based on spectral irradiance of sunlight, absorption profiles, and quan-tum yield of pesticide (Leifer 1988). In contrast, when pesticide molecules existas deposits on soil and plant surfaces, the heterogeneous microenvironmentmakes such estimation difficult. For example, many researchers have reportedthe quantum yield for pesticides in solution photolysis, but the information isvery limited on solid-phase photolysis (Krieger et al. 2000; Samsonov and Pok-rovskii 2001). In the case of soil photolysis, Balmer et al. (2000) introduced amodel function of light attenuation in soil with diffusion of a pesticide moleculeto better describe the dissipation profiles.

The molecule in the S1 or T1 state undergoes various chemical reactions.Typical reactions observed in photolysis on soil and plant surfaces are summa-rized in Fig. 2. One of the most important photoreactions is initiated by carbonyln → π*excitation. The photoinduced cleavage of a C−C bond generates theketyl radical (Norrish type I), or the carbonyl carbon in the excited state ab-stracts hydrogen from a neighboring alkyl group (Norrish type II) or a solventmolecule. The electronic excitation also occurs at the C=C bond or aromaticmoiety, which results in cis/trans (or E/Z) geometric isomerization or R/S opticalone. The photoinduced homolytic bond cleavage is also a main reaction pathwayin photolysis. When it occurs at an ester or ketone moiety, decarboxylation ordecarbonylation proceeds in addition to the apparent photoinduced hydrolysis,and its extent depends on solvent structure in relation to stabilization of pro-duced radicals. The C-halogen (Cl, Br, and I) bond is known to also undergophotoinduced cleavage. Dealkylation via oxidation with O2 or reactive oxygenspecies such as the hydroxyl radical (OH�) is also known. Oxidation at eithercarbon or sulfur is one of the most important routes of photodegradation. Themost familiar rearrangement is thiono-thiolo for O-aryl phosphorothioate insec-ticides whose O-alkyl group (typically a methyl group) shifts to the P=S sulfuratom (reaction 9a). The other is a photo-Fries rearrangement for amides andcarbamates where the ketyl radical generated via cleavage of an N−C(=O) bondmostly migrates to the o- or p-position of the phenyl ring (reaction 9b). Theformation of a new bond is typically observed for intramolecular cyclization fororganochlorine cyclodiene insecticides (reaction 10a).

Incidentally, an energy transfer can proceed between the excited donor (D*)and acceptor (A) molecules. The spectral overlap between the emission spec-trum of D* and absorption spectrum of A is prerequisite (Fig. 3), and energytransfer proceeds efficiently when the process is spin-allowed and exothermic(Turro 1978; Roof 1982). There are two mechanisms known for energy transfer,coulombic and exchange interactions. The former mechanism involves the in-duction of a dipole oscillation in A by D* via a magnetic field and does notrequire physical contact of the interacting D* and A. Forester theory indicatesthat the rate of energy transfer according to this mechanism is proportional tothe spectral overlap and inversely proportional to intermolecular distance be-tween D* and A to the sixth power. Therefore, the energy transfer efficiency isgreatly reduced as the distance increases up to approximately 50 A and thus is


Fig. 2. Types of photoreactions.

sensitive to diffusion of D* and A. In contrast, the exchange interaction involvesa double electron substitution, that is, jump of an electron from D* to the unoc-cupied orbital of A and the simultaneous jump of an electron from A to thehalf-occupied orbital of D* via overlap of electron clouds, which requires physi-cal contact (collision) between D* and A. Singlet energy transfer is spin-allowedfor both long-range coulombic and short-range exchange mechanisms. However,

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Fig. 2. Continued.

because an acceptor molecule is in the S0 state, the triplet energy transfer isbasically spin-forbidden and only proceeds via a short-range exchange mecha-nism. The interatomic distance expected for the triplet energy transfer is esti-mated to be 10–15 A. The longer a molecule remains in an excited state thegreater the probability that it will transfer energy to a suitable neighboring mole-cule. Therefore, the triplet energy transfer is the most common and most impor-tant type of energy transfer involved in photolysis of pesticides.

Fig. 3. Schematic description of the spectral overlap.


When photolysis on soil and plant surfaces is considered, diffusion of pesti-cide molecules is likely to be limited by adsorption and very high viscosity ofthe medium. These situations may imply less possibility of energy transfer ex-cept for the case where pesticide molecules are located in the neighborhood ofD* or A. There are many candidates in the environment playing a role as D* orA, and some of them are listed in Table 3 (see table on page 86) together withsynthetic chemicals. Because flavonoids and long-chain alkyl ketones are someof the wax components in plant foliage (see Section III.E), photosensitizationby these components may be possible by taking account of the ET values ofpesticides (54–75 kcal mol−1). In the case of soil surface, either photosensitiza-tion or quenching by humic substances with the ET value of 60–62 kcal mol−1

is considered to proceed. Although concrete demonstrations by measurement arelimited, the importance of spectral overlap between pesticide and synthetic dyescoadsorbed on clay surfaces has been reported in relation to stabilization ofphotolabile pesticides (Margulies et al. 1988; El-Nahhal et al. 2001).

Among natural products, molecular oxygen (O2), whose ground state is atriplet, is the most effective quencher. The very low lying singlet states withapproximate energy levels of 23 and 38 kcal mol−1 can easily react with theexcited states of pesticides and natural products, resulting in the formation ofsinglet oxygen (1O2). In addition, the other active species such as OH� and ozone(O3) are deeply involved in photoinduced reactions. It is not easy to identifyactive oxygen species in photolysis on soil and plant surfaces, but the basicreactivity of some pesticides is known (Table 4 [see table on page 88]). Sulfuroxidation is one of the characteristic reactions. Concrete evidence on theinvolvement of 1O2 was given for fenitrothion (138)2 by Verma et al. (1991),who showed the significant decrease of oxon formation when the 1O2 scavengerwas added. Formation of peroxide at the isobutenyl moiety of pyrethroid (Fig.2, reaction 7) was found sensitive to 1O2 scavenger (Ruzo et al. 1980, 1982) andwas greatly reduced by introduction of halogen atoms instead of the geminalmethyl groups (Holmstead et al. 1978a; Ruzo 1983). Hirahara et al. (2003)confirmed the photoinduced formation of 1O2 in the phosphate buffer solutionof fenthion (143) without any dye by ESR (electron spin resonance) using thespin trap reagent and supposed that (143) is a photosensitizer for O2. Severalmethods, including Fenton’s reagent and illumination in the presence of hydro-gen peroxide (H2O2), O3, Fe3+, humic substances, or a semiconductor, have beenutilized to generate OH�. The oxidative desulfuration and N-dealkylation to-gether with hydroxylation proceeded via reactions with OH�. The involvementof OH� in photolysis of atrazine (185) was demonstrated by retardation of thereaction in the presence of mannitol as a radical scavenger, and the attack at theα-position of the N-ethyl moiety was evidenced by formation of the N-acetylderivative. Concerning O3, aqueous ozonization has been extensively investi-gated (Reynolds et al. 1989) but the reaction on solid surfaces seems to be

2See footnote 1, p. 3.

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limited. Spencer et al. (1980) reported the desulfuration of parathion (135) onsoil dusts and clay minerals in the presence of O3, which was recently confirmedby Kromer et al. (1999). The sulfur atom was finally oxidized to sulfate ion(Gunther et al. 1970). In the case of pyrethroids, ozonization of the isobutenylmoiety was found to proceed to give the corresponding aldehyde derivatives(Ruzo et al. 1982).

III. Factors Controlling Photolysis on Plant SurfacesA. Environmental Factors

A number of factors such as meteorological conditions, formulation type,sprayer characteristics, and affinity of plant surface to formulation are consid-ered to determine the amount of pesticide attached to the surface as well asground cover and canopy thickness of plants (Willis and McDowell 1987).Zongmao and Haibin (1997) extensively investigated factors controlling dissipa-tion from tea plant surfaces for 16 pesticides. Photodegradation was found to beone of the most important factors in dissipation process except for evaporation,rainfall elution, and growth dilution. Both photolysis and rainfall elution werefound to play a great role in the dissipation of diflubenzuron (159) in a coniferforest (Rodriguez et al. 2001). Garau et al. (2002) examined the extent of pesti-cide loss from a cellulose membrane due to evaporation and codistillation inthe presence or absence of underlying water. Evaporation, codistillation, andphotolysis all contributed to dissipation of pyrimethanil (209) and cyprodinil(210) but with each varying to some extent, while only photolysis was the con-trolling factor for azoxystrobin (244) and fludioxinil (208). The existence oftomato fruit wax mostly retarded evaporation and codistillation of pesticides andexhibited a screening effect against sunlight. For a pesticide with higher vaporpressure and less photoreactivity, volatilization loss became predominant in dis-sipation as observed for chloropyrifos (145) (Meikle et al. 1983). Through aglass wind tunnel study for 14C-fenpropimorph (227) individually applied tobean, sugar beet, and radish, the importance of reactive species (OH� and/or O3)in air was demonstrated (Ophoff et al. 1999). Furthermore, either soil dusts orclay minerals enhanced oxidation of parathion (135) to its oxon in the presenceof O3 (Spencer et al. 1980). In addition to these factors, penetration of pesticideinto cuticle and biotic metabolism therein are also considered important (Bent-son 1990; Katagi and Mikami 2000).

B. Illumination Conditions

Spectral irradiance of sunlight at the plant surface is most important to under-stand the effect of photolysis (Fig. 4). Because the window glass used in ordi-nary greenhouses absorbs a considerable amount of light in the UV-B region

1All pesticides are identified by their common name and parenthetical identification number, andtheir structures are illustrated in the Appendices. Preceding the Appendices is a Directory of Pesti-cide Chemical Structures listing all pesticides in alphabetical order to aid the reader in locatingspecific structures.


Fig. 4. Photodegradation of pesticide on plant: (a) precipitation, (b) wind, (c) volatiliza-tion, (d) sunlight outdoors, (e) sunlight in the borosilicate glass greenhouse.

(280–320 nm), this filtering effect is likely to reduce the overlap between thesolar emission spectrum and the near-UV absorption spectrum of many pesti-cides (Kleier 1994). Photodegradation was measurably reduced by covering thePetri dish as a model of the greenhouse window (Garau et al. 2002). Fukushimaet al. (2003) examined the photolysis of 14C-fenitrothion (138) on tomato fruitin a greenhouse with a ceiling made of quartz or borosilicate glass. The intensityof sunlight at <360 nm was significantly reduced in the borosilicate glass green-house, and neither the corresponding oxon nor the S-isomer generated by photol-ysis in the quartz greenhouse was detected. Furthermore, transmission throughthe greenhouse window is also known to be reduced by glass pollution, and itsextent was larger in the shorter wavelength region (Van Koot and Dijkhuizen1968). The structure of greenhouse changing the intensity and spectral irradianceof the transmitted sunlight gave an insignificant effect on dissipation of chlor-pyrifos (145). Type of crop and season were the most relevant factors (MartınezVidal et al. 1998). Similar results were obtained for fenpropathrin (24) (MartınezGalera et al. 1997), while degradation of methomyl (70) was found to dependon the type of greenhouse (Gil Garcia et al. 1997).

Degradation of pesticides in the greenhouse or outdoors was compared toexamine the controlling factors in foliar dissipation. The application of pirimi-

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carb (78) to lettuce was conducted both in greenhouse and field (151; Cabras etal. 1990). No significant differences occurred in half-lives of total carbamates,but greater formation of these degradates was observed in the field. The compar-ative degradation study of parathion (135) using a growth chamber, greenhouse,and open field with and without motorized covering exhibited more formationof the oxon and S-isomer in the field (Joiner and Baetcke 1973). Based on theseresults, the experimental conditions of growing plants should be monitored andcompared with the real environment as much as possible to investigate the mostrealistic pesticide photodegradation process.

C. Effect of Formulation

Pesticide formulation is composed of an active ingredient, carrier such as clay,surfactants as wetting and spreading agents, nonevaporating viscous stickers,humectants, and penetrating agents such as crop oils (Hazen 2000). These addi-tives having hydrophobic and hydrophilic parts in a molecule provided a verycomplex medium for photolysis of pesticides, and their aromatic moiety becomesa possible photosensitizer or quencher (Nutahara and Murai 1984; Thomas andHarrison 1990). Baker et al. (1983) investigated extensively the changing natureof epicuticular waxes on the impact of several formulations containing 14C-labeled pesticide using scanning electron microscopy, X-ray analysis, and mi-croautoradiography. Oil formulations were found to immediately spread throughcrystalline wax whereas aqueous solutions distributed most readily over smoothsurfaces. Lipophilic pesticides are partitioned favorably into the organic phase,separating as a zone at the outer edge of the droplet residue, but hydrophilicpesticides are concentrated in the central region. Furthermore, the fluidity ofepicuticular waxes is known to change with hydrophobicity and lipophilicitybalance of the surfactant (Hess and Foy 2000). In addition, surfactants in formu-lations are considered to affect either uptake of pesticide molecules across thecuticle to plant tissues or photodegradation profiles on plant surfaces. The for-mer phenomenon by monodispersing alcohol ethoxylates has been demonstratedfor several pesticides on barley leaves. Larger effects on diffusion coefficientwere observed for the larger-size molecule (Burghardt et al. 1998). The lattereffect was first pointed out in aqueous solution by Tanaka et al. (1979, 1981).Instead of formation of 4-OH and N-CHO derivatives, monuron (52) in aqueoussolutions of surfactants Tergitol TMN-6 or Triton X-100 underwent dechlorina-tion followed by dimerization and N-demethylation. Furthermore, photodegrada-tion of 17 herbicides was found to be accelerated by the presence of thesesurfactants.

Based on these results, pesticide molecules were thought to be partitioned tohydrophobic cores of micelles where photolysis such as that in an organic sol-vent proceeded favorably and surfactants such as Triton X-100 having an aro-matic moiety could act as a photosensitizer. Such photosensitization was alsoreported when oxysorbic or plant oil concentrate was used as the surfactant(Harrison and Wax 1985). In contrast, it is supposed that some surfactants hav-


ing a lower triplet excited energy than that of the pesticide can act as a quencher,which has been demonstrated for TMN-6 and nonaethoxylated p-(1,1,3,3-tetra-methylbutyl)phenol (Tanaka et al. 1986, 1991). The other possible effect bysurfactants would be stabilization of photoproduced radicals in a cage. In thecase of 2,4-D (1), a few products formed via Norrish type II or photo-Friesmechanism were detected through photolysis in aqueous solution containing sur-factant (Que Hee et al. 1979). There was no significant effect of Tween 80 orTrion X-100 on photolysis of metsulfuron (97) and chlorimuron (101) on glasssurfaces (Thomas and Harrison 1990), whereas in the other study acceleratedphotolysis was observed (Harrison and Thomas 1990). On corn leaves, similaracceleration was observed for (97) but with no clear effect for (101). In pyre-throids, reduced photolysis on glass surfaces was reported when surfactantswhere included (Megahed et al. 1987).

D. Anatomy of the Leaf

As shown in Fig. 5, leaves are covered with protective cuticles that function bydecreasing water loss and protecting the plant from infection by various patho-gens. The cuticle is a complex structure consisting of a pectin layer that bindsthe cutin to the epidermal cell walls and a layer of epicuticular wax on theoutside, this structure is known to depend on plant species (McFarlane 1995;Bianchi 1995). When the stomata are open, gas molecules can diffuse in andout and interact with a large hydrophilic area of water-covered mesophyll cells.Most pesticides are hydrophobic molecules, and thus the large lipid-coveredsurface of leaves (cuticles) forms an ideal sink for accumulation of pesticides.The fine structure of the wax layer greatly differs between plant species and ismorphologically classified by using light microscopy into four main forms: nee-dles, rods, granular layers and films (Baker 1982). Use of the electron micro-scope has revealed that the aerial surfaces of all higher plants carry a partial orcontinuous coverage of amorphous wax and that formation of crystalline wax is

Fig. 5. Transverse view of the typical surface structure of plant foliage: (a,d) epidermalcell, (b) stoma, (c) mesophyll, (e) pectin, (f) cutin and embedded waxes, (g) epicuticularwaxes.

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frequently superimposed on amorphous layers. Penetration through these waxregions and the underlying cutin layer has been extensively studied, for exam-ple, by using the diffusion cell method (Schonherr and Riederer 1989).

Radiant energy of sunlight is considered to interact with the leaf structure byabsorption and scattering. As shown in Fig. 5, most leaves have a distinct layerof long palisade parenchyma cells in the upper part of the mesophyll and moreirregularly shaped spongy parenchyma cells in the lower part. Sunlight is re-flected and scattered by hairs, leaf pubescence, and the glaucous leaf surface,and a portion of the light enters into the leaf (Robberecht and Caldwell 1980;Holmes and Keiller 2002). This light is critically reflected internally at the cellwalls in the intercellular space as a result of the difference of refractive indexbetween air and water in tissues (Gates et al. 1965). Pesticides by foliar applica-tion are considered to distribute mainly on the epicuticular wax layer, but aportion may enter into the plant directly through stomata or diffusion; thus,depth and spectral distribution of penetrated sunlight would be important whenphotodegradation is considered. Many studies have been conducted to investi-gate this using a fiberoptic probe (Vogelmann and Bjorn 1984). About 90% ofthe penetrating monochromatic light (310 nm) was attenuated within the initialone third of the leaf (100–150 µm) of Brassica napus L., mostly at the epider-mal cells; polychromatic radiation (280–320 nm) exhibited a relatively uniformspectral distribution within the leaf (Bornman and Vogelmann 1991; Cen andBornman 1993). UV-B radiation was found to reach the epidermis and meso-phyll in other measurements for this leaf (Alenius et al. 1995). Day et al. (1994)measured UV absorption spectra and the epidermal transmittance spectra at280–350 nm of foliage from 42 plant species and demonstrated that some flavo-noids act as a UV-absorbing agent. These observations imply that pesticide mol-ecules in the leaf can absorb some part of the radiation energy of sunlight irre-spective of their location, and not only the anatomy of the leaf but alsochromophores in leaf tissue can greatly affect their photodegradation.

E. Wax Chemistry

Epicuticular waxes are basically aliphatic compounds and are readily solubilizedby organic solvents with minimal contamination by lipids from the inner cuticu-lar layers. A mixture of chloroform and diethyl ether (1 : 1, v/v) was found tobe efficient to isolate waxes containing cyclic compounds (Baker 1982). Leavesof many herbaceous plants carry delicate membranes with only sparse wax de-posits (5–10 µg cm−2) and many weed species also have thin wax layers. Waxdeposits on rapidly expanding leaves of leek and Brassica spp. are heavier(30–60 µg cm−2), similar to those on leaves of many fruit crops. Wax layers onfruits are invariably much thicker than those on the corresponding leaves (50–400 µg cm−2), and thick deposits were also found for pistachio and olive (60–300 µg cm−2). As a result, the average thickness of the cuticle varies with plantspecies from 3 to 15 µm (Lendzian and Kerstiens 1991). Wax chemistry, espe-cially of epicuticular waxes, has been systematically investigated for many plant


species, sometimes with different growth stages, first by thin-layer chromatogra-phy (TLC) and gas chromatography (GC) of the derivatized extracts and later bygas chromatography-mass spectrometry (GC-MS), nuclear magnetic resonance(NMR), and infrared (IR) (Baker 1982; Walton 1990; Bianchi 1995). Waxes arebasically classified into even- and odd-carbon-numbered straight chain homo-logues and cyclic compounds (Baker 1982; Bianchi 1995). The first class con-sists dominantly of acids (C12–C18 and C20–C32), aldehydes (C22–C32), primaryalcohols (C22–C32), and alkyl esters (C36–C72). The odd-numbered homologuesare hydrocarbons (C17–C35), secondary alcohols (C21–C33), ketones (C23–C33),β-diketones (C29–C33), and hydroxy-β-diketones (C29–C33). The last class con-sists of triterpenoid acids such as ursolic and oleanolic acids, triterpenols suchas α- and β-amyrin, triterpenoid esters, and ketones. Among them, the followingchemicals are known to be common major constituents of epicuticular waxes:nonacosane and hentriacontane for hydrocarbons: hexacosanol, octacosanol, andtriacontanol for primary alcohols; nonacosan-10-ol for secondary alcohols; hen-triacontane-14,16-dione and tritriacontane-16,18-dione for β-diketones; and ur-solic acid for triterpenoids.

Typical wax constituents with major homologues for representative plants,fruits, and leaves are briefly summarized in Table 5 (see table on page 89). Inthe case of leaf waxes, composition was found to vary with not only growthstage but also the parts of the leaf, that is adaxial and abaxial surfaces (Bukovacet al. 1979; Baker and Hunt 1981; Riederer and Schneider 1990). Unique com-ponents such as anthraquinone in the leaf waxes of perennial rye grass (Alleboneet al. 1971), a long-chain 1,4-benzoquinone in a wide variety of leaves (Kofleret al. 1959), and novel fatty acid esters of E- and Z-p-coumaryl alcohols in cv.Gala apples (Whitaker et al. 2001) have been reported.

F. Photoinduced Reactions

There has been no systematic investigation on the contribution of these waxcomponents to photolysis of pesticides. Pirisi et al. (1998) have measured UVabsorption spectra of epicuticular waxes of nectarines, oranges, and mandarinoranges extracted by chloroform and/or methanol. These waxes basically exhib-ited featureless absorption at 290–400 nm with small shoulders around 320 nm,but no clear correlation with photolysis rates of pirimicarb (78) could be de-tected. The wax of annual spruce needles also showed the featureless spectrumbut with significant absorption at 300–400 nm (Niu et al. 2003). Furthermore,although no absorption maximum was observed for leaf waxes of caster bean,UV absorption at about 300 nm was observed for Scotch pine, cabbage, andCarnauba waxes (Wuhrmann-Meyer and Wuhrmann-Meyer 1941). Concerningeach chemical class of waxes, the theory of UV absorption indicates no absorp-tion by simple hydrocarbons, but many chemicals containing a carbonyl moietycan absorb UV light at >290 nm (Jaffe and Orchin 1962). n-Hentriacontane, themajor component of green tobacco leaf, was shown to be transparent to the UVregion (Carruthers and Johnstone 1959). As β-diketones and α,β-unsaturated

16 T. Katagi

ketones (aldehydes) show UV absorption maxima around 270 nm and 320–370nm (Cookson and Dandegaonker 1955; Horn and Lamberton 1962), these com-ponents as well as anthraquinone and 1,4-benzoquinone already described aremost likely to be involved in photolysis of pesticides on plant foliage.

Triterpenoid derivatives are detected as major to dominant components ofleaf waxes, but their UV absorption maxima are usually located at 200–210 nmin hexane (Wheeler and Mateos 1956; Weizmann and Mazur 1958; Turner1959), which may indicate less importance in photolysis of pesticides. Phenyl-propanoids including flavones, flavonols, and cinnamoyl esters in higher plantsare known to exhibit UV screening effect (Cockell and Knowland 1999; Kolbet al. 2001). These flavonoids are also known to show an antioxidant activity(McPhail et al. 2003) similar to β-diketones (Osawa 1994). Because the complexmixture of wax components is the primary reaction medium for pesticides, itshould be kept in mind whether these components simply act as highly viscousorganic solvents or are involved in photochemistry of pesticides as photosensi-tizer or quencher. As an example of wax effects on photolysis, either enhance-ment or retardation of photolysis was reported for 14C-fenarimol (239) spreadon glass surface with extracted waxes from barley, rape, strawberry, and appleleaves (Watkins 1987). On the bean leaf, more S-oxidation of carboxin (42)proceeded as compared with that on a glass surface (Buchenauer 1975). Acceler-ated photolysis was also reported for 2,4-D (1) on Zea mays leaves (Venkateshand Harrison 1999).

When 14C-dieldrin (123) was applied to bean foliage with flavone, formationof photodieldrin (124) was enhanced by a factor of 5–7 via triplet photosensiti-zation (Ivie and Casida 1971b). Rotenone exhibited the strongest sensitizationand effect of 15 pesticides tested, but anthraquinone had an insignificant effect.The chromanone moiety of rotenone common to flavone was found essential toshow its activity (Ivie and Casida 1970). Accelerated photodegradation in thepresence of flavone, triplet sensitizers, and extracts from plant was also reportedfor pyridafenthion (150), naproanilide (41), and flutolanil (39), all of whichwere resistant to photolysis by themselves (Tsao et al. 1989; Tsao and Eto1990a, 1991). Chlorophyll and furanocoumarins are also possible sensitizers inplants, affecting photodegradation profiles of pesticides (Dodge and Knox 1986;Dixon and Wells 1987). Although a reactive species has not been identified inmost cases, either possible hydrogen abstraction from wax components by thephotoproduced radicals originating from the pesticide or formation of a covalentbond with the unsaturated bond of waxes via a radical reaction was demon-strated by using model waxes such as cyclohexene and methyl oleate (Draperand Casida 1985; Schwack 1988; Schynowski and Schwack 1996; Breithauptand Schwack 2000). Nutahara and Murai (1984) have reported the enhancedphotodegradation of many pesticides by oleic and linoleic acids, possibly viasimilar mechanisms as above. Because the unsaturated alkyl chain of these com-pounds is known to undergo oxidation by reaction with 1O2, giving the corre-sponding monohydroperoxide (Nakajima and Hidaka 1993), this peroxide or itsphotodegradates may alter photodegradation of pesticides.


Formation of possible photosensitizers on foliage has also been reported. 6-Methyl-5-hepten-2-one (6-MHO) has been detected in significant amounts onfoliage of orange, oak, and pine trees together with 4-oxopentanal, geranylace-tone, and acetone, whose origin is considered to be unsaturated wax componentssuch as sesquiterpenes and triterpenes (Fruekilde et al. 1998). By using epicutic-ular waxes extracted from these leaves, oxidation by O3 produced these carbonylcompounds, possibly acting as an efficient photosensitizer on foliage. Beren-baum and Larson (1988) have reported the formation of 1O2 (�4 × 1012 1O2

molecules cm−2 sec−1) by illuminating intact leaves of wild parsnip and pricklyash. The reaction of ascorbic acid in plant cell walls with O3 was also found togenerate 1O2, and a similar reaction was found for gluthathione, methionine, anduric acid (Chameides 1989). Kanofsky and Sima (2000) utilized chemilumines-cence at 1270 nm due to 1O2 to monitor its formation under O3 from illuminatedtissue fluids prepared by vacuum infiltration technique or intact leaf of whitestonecrop. Emission of 1O2 with consumption of O3 was clearly demonstrated,and its retardation in the presence of ascorbate oxidase showed involvement ofascorbic acid in this reaction. Because O3 is a very familiar component of airover vegetation, the photochemical and/or chemical generation of 1O2 may playa substantial role in the degradation of some pesticides on foliage.

IV. Factors Controlling Photolysis on Soil SurfacesA. Soil Components

Soil is a variable mixture of minerals, organic matter, and water, capable ofsupporting plant life on the earth’s surface (Manahan 1994). The solid fractionof a typical productive soil is approximately 5% organic matter, originatingfrom plant debris in various stages of decay, and 95% inorganic matter. Soilusually contains air spaces and generally has a loose texture. The majority ofinorganic components (>90%) are crystalline and noncrystalline amorphousminerals including primary and secondary minerals; the former includes quartzand micas and the latter phyllosilicates (clay minerals), allophanes, and metaloxides. Quartz and micas are simple SiO2 minerals whereas clay minerals arebasically aluminosilicates. Therefore, their surface property and photoreactivitymay be estimated from those of silica gel as a surrogate surface. There are threetypes of hydroxyl groups existing on silica gel with a different acidity: geminalsilanol (Si(OH)2), nongeminal (SiOH), and hydrated silanol (SiOH��OH2), asdemonstrated by 19Si- and H-NMR and fluorescence analysis (Thomas 1993).Clay minerals possess layered structures consisting of silica tetrahedral and alu-mina octahedral sheets with a ratio of 1 : 1 or 2 : 1 (Takagi and Shichi 2000).Kaolinite is the typical clay in the former type and pylophyllite, smectite, andvermiculite groups constitute the latter. The isomorphous substitution of centralatoms in tetrahedral and octahedral structures with another of a lower valencyresulted in a net negative charge for clay sheets and electrostatic force via count-ercations, making them loosely bound to each other (Caine et al. 1999). Thepresence of interlayer space thus gives a sterically constrained reaction environ-

18 T. Katagi

ment for pesticide molecules when intercalated. Iron is one of the most abundanttransition metals in soil and is considered to play a large role in photoinducedredox reactions generating active oxygen species such as OH�. Sherman (1989)demonstrated by Mossbauer spectroscopy that most Fe3+ and Fe2+ ions werefound to occupy the octahedral sites and that some ions might occur as aninterlayer species such as a Fe2+-aquo complex in the 2 : 1 clay minerals. Insteadof the Fe3+-aquo complex, Fe(OH)2(H2O)4 would condense to form ferric hy-droxy polymers.

Humic substances account for 60%–70% of soil organic matter, consistingof a series of highly acidic, yellow to black, high molecular weight polyelectro-lytes and characterized by their high content of oxygen-containing functionalgroups such as COOH, phenolic, aliphatic, and enolic OH and C=O, togetherwith amino, heterocyclic amino, imino, and sulfhydryl groups (Stevenson 1976;Ruggiero 1999). The higher total acidity of fulvic acid (FA, �10 mEq g−1) thanhumic acid (HA, �7 meq g−1) can be accounted for by the higher content of aCOOH group in FA. The typical content of each functional group was reportedto be 3.6–8.2 mEq g−1 (COOH), 3.0–3.9 mEq g−1 (phenolic OH), 2.6–6.1 mEqg−1 (alcoholic OH), 2.7–2.9 meq g−1 (quinoid and ketonic C=O), and 0.6–0.8mEq g−1 (OCH3) (Choudhry 1984b). Similar results have been confirmed bySenesi et al. (1989) by using several soil humic substances and Suwannee Riversoil. The clay surface is usually covered with these humic substances, probablyvia formation of clay–metal–organic complexes. Through adsorption study ofatrazine (185), the contribution of clay surface on adsorption was proposed tobe important when organic matter content was less than �6% (Stevenson 1976).Based on their nature, interactions with HA and FA should be primarily consid-ered in soil photolysis of pesticides. As an adsorption isotherm, Freundlich,Langmuir, and Rothmund–Kornfeld equations are well known and the shape ofthe related isotherm would shed light on the adsorption mechanism. Proposedmechanisms of interactions are ionic bonding via cation exchange, hydrogenbonding, charge-transfer interaction with a quinoid moiety embedded in a humicstructure, cation-bridged ligand exchange with humic carboxyl moiety, covalentbinding, hydrophobic adsorption, and partitioning via dipole–dipole and/or vander Waals interaction (Stevenson 1976; Senesi and Testini 1984; Senesi andMiano 1995).

Another unique feature characteristic of soil humic substances is the presenceof stable radical species detected by ESR. Senesi and Schnitzer (1977) havereported the ESR signal at g = 2.0032–2.0050 without a hyperfine splitting forFA whose intensity increased with either chemical reduction under more acidicconditions or UV irradiation. They proposed semiquinones or its ions as themost likely partial structure of stable radical species. Further investigation onvarious soil HAs and FAs has shown the presence of two types of ESR signalsoriginating from a quinhydron-type structure and a phenoxide ion (Choudhry1981). These stable radicals would be involved in photoinduced transformationof pesticides as well as formation of active oxygen species, especially when atransition metal or its oxide coexists (Ruggiero 1999).


B. Environmental Factors Affecting Soil Properties

Many soil photolysis studies have not strictly controlled and monitored basicsoil properties, especially such as moisture, until the recent development by theChib’s group (Misra et al. 1997; Frank et al. 2002). As stated later, the penetra-tion depth of light into soil is known to be very limited, approximately to thetop 0.5 cm of soil surface, and so its influence is considered to be very differentfrom that in the bulk soil (Fig. 6). In this region, solid, solution, and vaporphases are all in close proximity to the soil–atmosphere interface under sunlightirradiation. Miller et al. (1989) concisely reviewed the effect of sunlight onsoil properties. They introduced a simulation on a typical diurnal variation oftemperature near the soil surface (0–2 cm) where the temperature increased upto near 40 °C at midday with a difference of about 20° during a day. A tempera-ture gradient even at this shallow depth can be suspected and, in fact, the mea-sured temperature at the irradiated surface, interior, and bottom of a soil thinlayer (0.5–1 mm thickness) attached to a cooling bath was reported to be 31°,29.9°, and 25.6 °C, respectively (Moore et al. 1989). This diurnal fluctuation oftemperature results in variation of soil moisture, that is, drying of soil duringdaytime and rewetting during nighttime. These variations together with sunlightirradiation would cause some effects on microbial activity, but its details arenot known for shallow soil. Recently, Reichman et al. (2000a,b) developed aone-dimensional nonisothermal model to examine the dynamic behaviour of asurface-applied pesticide under outdoor conditions. By using the diurnal varia-tion of meteorological data such as wind speed, air temperature and relativehumidity and sunlight irradiation, they have simulated changes of depth-depen-dent soil temperature and moisture.

C. Mass Transport in Soil

Diffusion of a pesticide molecule is considered to be basically described byFick’s law; however, the heterogeneous character of soil results in a more com-

Fig. 6. Structure of soil surface.

20 T. Katagi

plex description of a diffusion constant (D) than that in water (Graham-Bryce1969). Do is the diffusion coefficient in free solution and λ is the tortuosityfactor:

D = Do λθv/(Kd ρd + θv)

where θv is the volumetric water content, Kd is the linear partition coefficient,and ρd is the bulk density of soil. The tortuosity factor is a diffusion ratio ofpathlength in soil to that in aqueous solution (Scott and Phillips 1973). Graham-Bryce (1969) has developed diffusion cylinder methods to determine the diffu-sion constants of pesticides. Information on the diffusion constant of a pesticidein soil is very limited, but it seems to range from 0.05 to 50 mm2 d−1 (Table 6[see table on page 92]). When pesticide molecules are homogeneously distrib-uted in uniform soil, the mean movement after time t is given by (2Dt)1/2. There-fore, it would take about 2.4 hr and 1–2.5 d for parathion (135) and trifluralin(232) to move through the 1-mm-thick soil thin layer. The foregoing consider-ation shows the importance of mass movement in photodegradation on soil sur-faces, but many other factors would operate in the field. Walker and Crawford(1970) have demonstrated that diffusion constant was inversely proportional tosoil adsorption coefficient. Smaller diffusion with a higher water content wasreported for dinitroaniline herbicides (Jacques and Harvey 1979), whereas theopposite relationship was observed for triazines (Scott and Phillips 1972). Ehlerset al. (1969a,b) have reported the contribution to diffusion from vapor- andnonvapor-phase mechanisms. In contrast to soil, several investigators have re-ported diffusion of pesticides in plant waxes and intact cuticles using the diffu-sion cell method (Schonherr and Riederer 1989; Lendzian and Kerstiens 1991;Bauer and Schonherr 1992; Schreiber and Schonherr 1993), but their diffusionseemed much slower than in soil.

Balmer et al. (2000) conducted the photolysis of trifluralin (232) and p-nitro-anisole on kaolinite thin layers under constant temperature and humidity usingUV light at 300–800 nm. By kinetic analysis, assuming first-order direct photol-ysis and diffusion following Fick’s law, greater contribution of diffusion wasdemonstrated for (232) than p-nitroanisole. For niclosamide (40), photodegrada-tion in/on air-dried soil was greatly reduced in proportion to thickness of soilthin layer, whereas a very slight increase of photolytic half-life was observedfor the moisture-maintained soil (Frank et al. 2002). Because the photic depthof soil is usually less than 1 mm, as described in Section IV.D, migration of(40) to the photic zone with the aid of soil moisture was considered most likelyto account for the observation. The importance of vapor-phase transport in air-dried sandy loam soil was briefly examined for aryl ketones undergoing Norrishtype II photoelimination (Kieatiwong and Miller 1992). The existence of surfac-tant seemed to affect the migration of pesticides in soil. Gong et al. (2001)showed that the faster photodegradation of atrazine (185) in the soil thin layerwith sodium dodecylbenzene sulfonate and proposed that solubilization of (185)results in greater availability for photodegradation. A similar effect by hexade-


cane in soil photolysis was reported for 2,3,7,8-TCDD (129) (Kieatiwong et al.1990).

In addition, other factors such as the depth of the water table may have someinfluence on pesticide movement. The upward movement of chlorsulfuron (96)and triasulfuron (100) in a packed soil column was clearly demonstrated whenaddition of water to soil surface and drying in a growth chamber were cycledor the bottom of the column was dipped into water (Mahnken and Weber 1988).Capillary movement of pesticide, similar to the latter case, was also reportedfor norflurazon (214) and found to contribute to volatilization loss (Hubbs andLavy 1990). The effect of this type of upward movement on photolysis has beenconfirmed for 14C-napropamide (47) in soil under sunlight at the different watertable levels (Donaldson and Miller 1996).

D. Photic Depth in Soil

Soils are highly heterogeneous and unmixed as compared with solution, andillumination produces a light field difficult to define accurately (Wolfe et al.1990; Senesi and Loffredo 1997). The depth of light penetration (photic depth)in soil cannot be precisely defined but has been estimated by direct measurementof transmitted fraction of light or using probe molecules selectively undergoingdirect or indirect photolysis. Transmission of xenon arc light through soil thinlayers with 0.17-mm thickness was measured and UV light was found to bemore than 90% attenuated (Herbert and Miller 1990). Frank et al. (2002) exam-ined transmittance of UV light by varying the soil layer thickness from 0.5 to 4mm. Even a 0.5-mm-thick soil layer was enough to block about 95% of theincident light, but very slight light penetrated soil depths of 1.5 mm or greater.There was no significant difference of transmission at three wavelengths (280,365, and 440 nm). When soil thickness was less than 1.5 mm, more transmissionof light by a factor of 4–5 was observed for dry soil as compared with moistsoil, which may be accounted for by the difference in soil packing. As anotherapproach, Hebert and Miller (1990) utilized disulfoton (163) and flumetralin(233) as chemical probes to estimate the photic depth in soil. Flumetralin (233)absorbing light at wavelengths of 300–500 nm undergoes direct photolysis,whereas (163) has no UV absorption at >290 nm and only indirect photolysistakes place, that is, oxidation to the corresponding sulfoxide via reaction with1O2. By using these pesticides as probes, mean photic depths were estimated tobe 0.23 and 0.28 mm for direct and indirect photolysis, respectively, in thelaboratory, with larger values obtained for the outdoor study, 0.32 and 0.62 mm,respectively. The larger values for either indirect photolysis or outdoor studymay show contribution from diffusion of 1O2 to a deeper region of soil thanexpected for light penetration and that from convective and evapotranspirativetransport of pesticide by thermal heating at the soil–air interface. It is unclearif light reduction originates from bulk attenuation or as an inner filter phenome-non by soil. If an adsorbing substrate is relatively porous and highly colored, itwould be possible for an adsorbed pesticide to be “filtered” from the incident

22 T. Katagi

light. Yokley et al. (1986) investigated photodegradation of pyrene and benzo-[a]pyrene on silica gel, alumina, controlled pore glass (100 A on average),graphite, and various coal ashes by using a xenon arc lamp and reported theimportance of both adsorption to pores and UV screening. The UV screeningeffect by soil was also reported for photodegradation of polyaromatics whereslower degradation was observed for soil with lower reflectance (Moore et al.1989). Similar reduction of light has also been reported for sediments suspendedin aqueous solutions of pesticides (Miller and Zepp 1979; Oliver et al. 1979;Zepp and Schlotzhauer 1981).

E. Effects of Soil Properties on Photolysis

Konstantinou et al. (2001) have shown the possible involvement of photosensiti-zation based on faster photodegradation of herbicides in soil with higher organicmatter. In contrast, soil organic matter reduced the photodegradation of chlorim-uron ethyl (102) (Choudhury and Dureja 1997a), triasulfuron (100) and thifen-sulfuron-methyl (105) (Albanis et al. 2002), and fipronil (220) (Bobe et al.1998b), indicating involvement of either quenching or a shielding effect. Forniclosamide (40), modification of soil by addition of 3% HA was found toreduce photodegradation (Graebing et al. 2002). An insignificant effect of or-ganic matter on photolysis was observed for mecoprop (4) but its retardation bysoil amendment with 10% peat was detected under dry conditions, also implyingthe quenching effect (Romero et al. 1998). Clay is the other important soilcomponent and may affect the photodegradation profiles of pesticides. Sukuland Spiteller (2001) reported the linear relationship between photolytic half-lifeof metalaxyl (37) and clay percentage in soil. Because (37) does not have anysignificant UV absorption at >290 nm, photolysis was considered via indirectphotolysis, and the lower rate in soil with a higher clay percentage was likelyto originate from more intercalation of (37) into the intralattice structure of claywhere the incident light was screened.

Surface pH was an important factor, and such a pH effect would be operativefor acid-labile pesticides such as sulfonylurea herbicides (Schroeder 1997). Oneof the other important factors to control photolysis would be soil moisture con-tent. Faster photodegradation was detected in moistened than air-dried soils foralachlor (34) (Fang 1977), imidazolinone herbicides (Curran et al. 1992), andflorasulam (48) (Krieger et al. 2000), and photoinduced hydrolysis and/or migra-tion of pesticides to the photic zone of the soil thin layer might operate in thesecases. Enhancement of photolysis with soil moisture was observed for mecoprop(4), but at higher moisture the photodegradation rates decreased (Romero et al.1998). The significant decrease of photolysis rates in moistened soil was re-ported for fenpropathrin (24), which originated mainly from the increase ofsurface pH on soil with moisture (Katagi 1993b). As clearly seen from theseexamples, there are different mechanisms affecting photolysis with change ofsoil moisture, and thus it is not easy to estimate its effect a priori.


F. Photophysical and Photochemical Processes of Soil Components

Soil is a heterogeneous system where clay minerals are coated with humic sub-stances and metal (hydr)oxides and the various photochemical reactions such asphotosensitization, quenching, and photoinduced reaction proceed (Fig. 7).

Humic Substances and Intact Soils There are many excellent reviews on pho-toprocesses of soil and aquatic humic substances (Zepp et al. 1981; Choudhry1984a; Zepp 1988, 1991; Hoigne et al. 1989; Cooper 1989; Frimmel 1994).UV-vis spectra of various HA and FA exhibited mostly featureless absorptionwith their tail extending up to 500–600 nm. The primary photoprocess is excita-tion to the short-lived (�1 nsec) singlet states (Fig. 8). These excited states canreact with a pesticide molecule via a diffusional or static bimolecular process,and the latter would play a greater role on soil surfaces. Zepp et al. (1985)estimated the triplet energy of most humic substances to be around 60 kcal mol−1

(250 kJ mole−1) by using photoisomerization of 1,3-pentadiene as an index. Itdepends on the energy level of triplet states of humic substances as comparedwith that of a pesticide molecule which process predominates, sensitization orquenching. Many pesticides are known to undergo photosensitized degradationby humic substances (Jensen-Korte et al. 1987), whereas aqueous photodegrada-tion of imazapyr (229) was slowed in the presence of HA due to the UV screen-ing effect (Elazzouzi et al. 1999). In the photoinduced E/Z isomerization of fouralkyl cinnamates having a different association ability toward Fluka HA, only2-fold increase in the rate of isomerization was observed for the cinnamate

Fig. 7. Photoreactions on soil surface: (A) sensitization, (B) quenching, (C) photoinducedreaction, (D) adsorption/desorption, (E) spectral change, (F) inner-filter effect. P: pesti-cide; D: degradate(s); HS: humic substances; M: metal (oxides: hydroxides etc.).

24 T. Katagi

Fig. 8. Photophysical and photochemical processes of humic substances. HS: humic sub-stances; RH: substrate.

having a 40-fold-higher affinity to HA (Van Noort et al. 1988), indicating thatthe associated form was hardly available for triplet energy transfer.

The presence of reactive excited triplet states has been suggested for humicsubstances through investigation of photoinduced degradation of cumene andbenzene (Kotzias et al. 1986). Because diffusion of pesticide molecules is con-sidered to be restricted on soil surfaces, the possible reactions of a pesticidemolecule with an excited triplet of humic substances are transfer of electron orhydrogen instead of direct energy transfer. These processes have been demon-strated for aqueous humic substances in photodegradation of the several methyland methoxy phenols (Canonica et al. 1995; Aguer and Richard 1996a). Theyproposed an aromatic ketone moiety as a reactive site model in humic sub-stances that underwent electron or hydrogen transfer via its excited n-π* state.Their contribution as well as energy transfer has been examined by using ureaherbicides including fenuron (51) and monuron (52) (Aguer and Richard 1996b;Richard et al. 1997; Aguer and Richard 1999; Gerecke et al. 2001). Aguer et al.(2001) showed the higher reactivity of HA fractions with a smaller molecularsize in photolysis of (51). They also demonstrated that soil FA having a smallerspecific absorption coefficient shows a higher activity, but that no meaningfulcorrelation is detected for HAs (Aguer et al. 2002). The weak photoinductiveefficiency of highly absorbing humic substances implied that the majority ofabsorbing components had no photoinductive effect. There may be various smallorganic molecules existing except for humic substances, and therefore they maybe involved in photolytic processes on soil. Kieber and Blough (1990) showedthe possible photoinduced formation of various carbon-centered radicals thatmay react with pesticides under some photolytic conditions on soil surfaces.

Humic substances are known to react with O2 via energy or electron transferprocess to generate the very reactive 1O2, OH�, superoxide anion (O2

−), and


peroxide radical species (see Fig. 7). The contribution of each process wasroughly estimated for dissolved organic matter on an excited singlet state basis(Zepp 1991). Thermal deactivation was a dominant process (97%–99%), andonly 1%–3% of energy would be transferred to an excited triplet state, most ofwhich was involved in formation of 1O2. In an aqueous solution of HA, Taka-hashi et al. (1988) confirmed the formation of OH�, O2H�, and 1O2 in the pres-ence of O2 by ESR measurements using spin-trapping reagents. Nanosecondlaser spectroscopic methods were applied, and two short-lived transients fromfour illuminated natural waters were estimated to be an excited triplet state of aquinoid structure of humic substances and hydrated electron (e−

aq) (Fischer et al.1985, 1987; Power et al. 1987; Zepp et al. 1987). Photoinduced generation ofe−

aq from natural waters also has been confirmed by its conversion to OH� withN2O (Thomas-Smith and Blough 2001), and the steady-state concentration ofe−

aq was estimated to be approximately 1.1 × 10−17 M (Breugem et al. 1986).Because e−

aq quickly reacts with water molecules to give O−2 and O2H� if gener-

ated (Hoigne et al. 1989), its importance would be greatly lessened, especiallyon soil surfaces.

The steady-state concentration of 1O2 in natural water has been estimated tobe 10−14–10−12 M (Zepp et al. 1977; Wolfe et al. 1981; Haag and Hoigne 1986).The quantum yield of the photoinduced generation of 1O2 from aqueous solu-tions of soil HA and FA was estimated by both ESR and chemical analysisusing furoin (1,2-dimethyl-2-hydroxyethanone) to be 0.39–5.5 × 10−3 (Aguer etal. 1997). On soil surfaces, Gohre and Miller (1983) first demonstrated photoin-duced formation of 1O2 by using tetramethylethylene and 2,5-dimethylfuran aschemical probes. Gohre and Miller (1985) demonstrated that nontransition metaloxide powders such as silica gel, aluminum oxide, and magnesium oxide cata-lyze the formation of 1O2. They proposed the reaction of an exciton bound to adefect on a solid surface with adsorbed oxygen via transfer of electronic energy,and no correlation between 1O2 generation and the content of soil organic matterwas reported (Gohre et al. 1986). The existence of 1O2 was supported by obser-vation of chemiluminescence at 615–650 nm possibly due to 1O2 dimoles, butrecently a direct spectrophotometric method for the very weak chemilumines-cence at 1270 nm (1O2 → 3O2, spin-forbidden process) has been developed(Rodgers 1987; Kanofsky 2000).

The reaction types of photosensitized oxidation via 1O2 can be classified intoformation of endo-peroxide, ‘ene’ reaction giving allyl hydroperoxide, and for-mation of 1,2-dioxetane (Foote 1968a,b; Wilkinson and Brummer 1981). Thethioether-containing pesticides on soil were found to be transformed to the cor-responding sulfoxide by sunlight exposure most likely via reaction with 1O2

(Gohre and Miller 1986). The other example was photoinduced degradation ofbioresmethrin, 1R-trans isomer of (15), whose degradation was clearly reducedin the presence of β-carotene as an efficient 1O2 quencher (Clements and Wells1992). The enhanced degradation of 2-dimethylamino-5,6-dimethylpyrimidin-4-ol in D2O inhibited by sodium azide also showed involvement of 1O2 in itsdegradation, possibly attacking the 5,6-double bond (Dixon and Wells 1983).

26 T. Katagi

Under exposure to sunlight, OH� is photochemically generated via (1) reac-tion of humic substances in the excited triplet with water, (2) dissociation ofnitrate ion followed by protonation, and (3) degradation of H2O2 formed byreaction of e−

aq with water (Hoigne et al. 1989; Zepp 1991); in addition, coexis-tence of metal cations such as ferric ion with humic substances was consideredto play a great role in generating OH� via (4) the photo-Fenton reaction. Thesecond mechanism is considered to be predominant in the aquatic environment,but investigation has demonstrated that about half of OH� is generated viaphoto-Fenton reaction, and an O2-independent pathway also exists (Vaughamand Blough 1998). Among these four mechanisms, the first and last proceduresare considered to be more important to soil photodegradation. Photoinducedformation of OH� was confirmed in photolysis of 2,6-dimethoxyphenol with soilextracts by ESR (Suflita et al. 1981). Many investigations on OH�-generatingability of metal–humate complex through the Fenton or Haber–Weiss mecha-nism have been reported. Paciolla et al. (1999) demonstrated the intrinsic abilityof Fe3+– or Cu2+–HA complexes to generate OH� from H2O2 in darkness. Moss-bauer spectroscopy of this complex showed that about 5% of iron ion was pres-ent as Fe2+, indicating involvement of the above mechanisms.

Fukushima and Tatsumi (1999) studied the photocatalytic activity of theFe3+–soil humate complex giving OH� and H2O2 at >370 nm. Photoinduced one-electron transfer from HA to O2 followed by protonation was considered to yieldO2H�, which was then disproportioned into H2O2 and O2. They demonstratedthat the majority of Fe3+ was complexed with the HA fraction in a higher molec-ular weight and that the substrates were incorporated into the molecular skeletonof HA through photolysis (Fukushima et al. 2000, 2001; Fukushima and Tat-sumi 2001). Similar photo-Fenton reactions can be considered for small organicmolecules (Zepp et al. 1992; Balmer and Sulzberger 1999). Because soil compo-nents such as humic substances and silicate surface can trap a peroxy radical(Pohlman and Mill 1983), contribution from the aforementioned processes maybe lessened on soil surfaces.

As described, H2O2 is an another important reactive oxygen species in theenvironment whose generated humic substances are known to be deeply in-volved, and its steady-state concentration in an aquatic environment is estimatedto be 10−5–10−7 M (Draper and Crosby 1983; Cooper 1989). H2O2 on soil sur-faces would be degraded by various interactions with soil components or reactwith a pesticide molecule under sunlight irradiation. Petigara et al. (2002) inves-tigated the degradation processes of H2O2 in soils and revealed the possibleinvolvement of three pathways: a metal-catalyzed Harber–Weiss reaction, two-electron process achieved by catalase, and a peroxidic-type reaction. OH� wasfluorometrically determined using spin-trapping reagent and fluorescamine(Vaugham and Blough 1998). Retarded loss of H2O2 by autoclaving or additionof sodium azide or formaldehyde showed that 65%–75% of loss was due toabiotic processes on soil particles. Among minerals, goethite was found morereactive in generation of OH� than hematite. The photoinduced reaction of H2O2

with pesticide was not reported on soil surfaces, but aqueous photolysis of the


several pesticides in the presence of H2O2 clearly showed involvement of photo-generated OH� as evidenced by product analysis (Draper and Crosby 1981,1984).

Clays The flat organosilicate sheets with reactive edges give a unique reactionenvironment on clay. Furthermore, a geometric constraint by pore or sheet struc-tures in clay may alter the photochemistry of pesticides (Thomas 1993). A claysurface may exhibit a cage effect for radicals generated via photoinduced homo-lytic cleavage of a bond similarly observed for benzyl derivatives on silica gel(Avnir et al. 1981). As one of the basic properties on clay surfaces, it should benoted that the sites possessing a high Brønsted acidity may show catalysis onsome pesticides (Caine et al. 1999). Using these properties, Takagi and Shichi(2000) reviewed organic photochemistry in/on the clay surface. The efficienttransfer of electron or excited energy occurs between molecules adsorbed onclay surfaces, and ferric ion as an impurity in clay may act as an efficientquencher. Spectral shift by adsorption, steric constraint, and hydrogen bondingare known to result in the different profiles for photoinduced isomerization ofstyrene derivatives, Norrish type I and II reactions of aromatic ketones, andphoto-Fries rearrangement of carbamates.

One-electron transfer from an adsorbed chemical to clay is known for thian-threne on laponite, as evidenced by ESR (Mao and Thomas 1993). A similarphotoinduced electron transfer to laponite, silica gel, and silica-alumina wasreported for pyrene (Liu et al. 1994). Extent of a cation radical formation wasfound to gradually decrease at above 340 nm, indicating the existence of vari-able active sites having a different capacity of accepting electrons. There is alsoevidence that ferric ion included in montmorillonite clay as an impurity acts asan electron mediator between excited 10-methylacridinium hexafluorophosphateand iodide as an acceptor (Theng et al. 1997). The other type of electron transferis directed from clay surface to adsorbed species such as O2 and transition metalions in clay is considered to be deeply involved, as already described.

Various kinds of energy transfer on clay have been investigated. Detailedanalysis of difference IR spectra implied the possible interaction of bioresme-thrin, 1R-trans isomer of (15), with methyl green (MG) on clay surfaces, andphotostabilization of bioresmethrin by MG could be accounted for by an effi-cient energy transfer (Margulies et al. 1985, 1987, 1993). Margulies et al. (1988)have reported the red shift of absorption spectrum when NMH (242) was ad-sorbed on montmorillonite. Its photostablity was improved by coadsorption ofthioflavin (TFT) or MG and its extent was greater in the former dye. The UV-vis absorption maximum of TFT (410 nm) was closer to that of (242) comparedto MG (630 nm), implying more efficient energy transfer from (242) to TFT.The interaction of (242) with clay surface was considered to take place at thecyclic enamine moiety of (242) as estimated by difference IR spectrum. Further-more, the direct energy transfer to clay surface was also reported for (242)(Rosen and Margulies 1991). Less photostabilization of (242) adsorbed to non-tronite than hectorite and montmorillonite could be accounted for by the differ-

28 T. Katagi

ent contents of Fe3+ (29.46%, 0.26%, and 3.72% as Fe2O3, respectively), whichacted as a quencher via a charge-transfer mechanism. Efficient overlap of theemission with the absorption spectrum is indispensable for this energy transfer,which has been well established for norflurazon (214) coadsorbed with TFT onmontmorillonite (Undabeytia et al. 2000). They also proposed the photoinducedgeneration of OH� by montmorillonite accelerating its degradation. The involve-ment of reactive oxygen species in photodegradation of pesticides on clay sur-faces has been reported for tolclofos-methyl (142), esfenvalerate (28), and PB-acid (243) (Katagi 1990, 1991, 1992). A simple organic cation such asbenzyltrimethyl-ammonium has been demonstrated to modify adsorption ofalachlor (34) to a clay surface, leading to its protection against photolysis (El-Nahhal et al. 1999). The IR spectral shift of carbonyl and C(aromatic)-N bondsto lower and higher wave numbers, respectively, indicated the possible interac-tion of carbonyl oxygen with an exchangeable countercation on the clay surfacethrough a water bridge (Nir et al. 2000). The red shift of the UV absorptionspectrum (π-π*) of phenyltrimethylammonium was observed when coadsorbedto montmorillonite, indicating the interaction between the phenyl rings of (34)and the organic cation.

In addition, clay surfaces also give a steric constraint on an adsorbed pesti-cide molecule (Margulies et al. 1993; El-Nahhal et al. 2001). Photostabilizationof trifluralin (232) was realized by adsorption to montmorillonite, but the addi-tion of TFT did not give further improvement (Margulies et al. 1992). Differ-ence IR spectra clearly demonstrated interaction of one nitro group of (232)with the clay interface. It is known that (232) undergoes photo-induced cycliza-tion between nitro nitrogen and the C1 carbon of the N-propyl moiety to givebenzimidazole derivatives (see Fig. 2, reaction 10b). Because the intramolecularcyclization requires a conformational change of the N-propyl moiety, which isrestricted by adsorption to the clay, the observed photostabilization is mostlikely to be accounted for by imposition of a steric constraint on (232).

Metal Oxides and Hydroxides Transition metals such as iron and manganeseexist in the environment as their oxides, hydroxides, and sulfides or impuritiesin clay being substituted with aluminum ions. These compounds can becomequenchers of an excited energy and catalytic sites by acting as an electron medi-ator. It has been reported on silica gel that dye-sensitized photooxidation ofbromacil (198) by 1O2 is significantly reduced by addition of FeO, Fe2O3, Fe3O4,or FeO(OH), which can be accounted for by an electron transfer from the ex-cited dyes or energy transfer from 1O2 (Riter et al. 1990). In addition, as repre-sented by titanium dioxide, some materials also can act as semiconductors wherethe photoexcited valence band electron reduces an organic chemical and theaccompaning hole oxidizes (Balkaya 2003). Irradiation at >340 nm accelerateddegradation of (185) in the presence of typical semiconductors TiO2, ZnO, andWO3 to give N-dealkylated derivatives possibly via oxidation by OH�, whereasα-Fe2O3 and Al2O3 did not show any photocatalytic action (Pelizzetti et al.1993). Further examination was conducted by Lackhoff and Niessner (2002) to


estimate such a photocatalytic activity for environmental particles. Both TiO2

and ZnO exhibited a significant acceleration of degradation by a factor of 30–300, but much less activity was detected only for the other oxides such asSrTiO3, Fe2O3, and FeTiO3. Fine particles from natural sand, soot, and ash didnot show any meaningful acceleration compared with direct photolysis, whichwould be due to less occurrence of photocatalytic Ti (<1%) in these materials.Only very weak photocatalytic activity was observed for three soils when (185)was irradiated at >340 nm in aqueous suspension (Pelizzetti et al. 1993).

Similar trends of photocatalysis were briefly reported for dicarboximide fun-gicides (Hustert and Moza 1997) and azo dyes (Hustert and Moza 1994). Incontrast, the direct reaction with a positive hole was proposed for photolysis of2,6-dimethylphenol in aqueous suspension of goethite (α-FeOOH) (Mazellierand Bolte 2000). Not only the surfaces of these metal (hydro)oxides but alsospecies dissolved from the surface are considered to show catalytic acitivity ingenerating active oxygen species. Voelker et al. (1997) demonstrated this in themixture of lepidocrocite (γ-FeOOH) and FA, and Fenton-like degradation ofH2O2 has also been reported for goethite (Chen and Watts 2000). Many ironspecies are considered to exist in an aqueous phase after dissolution, andFe(OH)2+ species have been found most efficient in generating OH� under irradi-ation (Feng and Nansheng 2000). When H2O2 is enzymatically or abioticallyformed in soil, OH� is likely to be produced via Fenton-like reaction as demon-strated by ESR (Huling et al. 1998). These reactions may occur in real soil andcontribute, at least in part, to photodegradation of pesticides. In contrast to ironspecies, manganese oxides seem to show much less photocatalytic activity (Ber-tino and Zepp 1991; Lee and Huang 1995).

V. Atmospheric Oxygen Species

Reaction with oxygen species in air at a solid–air interface is considered to beanother important degradation pathway for pesticides deposited on soil and plantsurfaces. In the troposphere, O2 is the most abundant reactive species from itsbiradical structure in the ground state and is involved in either autooxidation orcoupling with radical species to give the corresponding peroxy species. Theother important species are O3 and OH� because of their high reactivity (Crosby1983; Marcheterre et al. 1988). In fact, their possible contribution to degradationof pesticides has been demonstrated on plant foliage (Spear et al. 1978; Ophoffet al. 1999) and soil surfaces (Spencer et al. 1980; Kromer et al. 1999). 1O2 isalso the other candidate, but its contribution may be limited to its specific reac-tivity toward a thiol moiety and C=C double bonds (Wilkinson and Brummer1981; Larson and Marley 1999). The formation and decline processes of thesereactive species in air are known to be very complex (Prinn 1994). O3 in thetroposphere originates from that in the stratosphere formed by direct photolysisof O2 or reaction between O2 and singlet oxygen atom O(1D) and dissipates viaUV photolysis to O(1D) or reaction with NO. OH� is mainly generated via reac-tion between O(1D) and H2O and deactivated by reaction with air pollutants

30 T. Katagi

such as CH4, SO2, and CO. The lifetime of O3 and OH� in air is estimated to be3 × 105 sec and 2.7 sec, respectively.

Concentrations of O3 and OH� are significantly low and known to vary withmany factors such as climate, geographical features, vegetation, and pollutionby human activities. The monthly mean value of troposheric O3 was 35–50ppb in the western North Atlantic (Oltmans and Levy 1992). The yearly meanconcentration at 13 stations in the United States was about 30 ppb with a sea-sonal variation, the maximum value (80–90 ppb) being detected in spring (Singhet al. 1978). The diurnal variation was also reported, and the maximum concen-tration was observed in the morning due to low photochemical destruction (Olt-mans 1981). Logan (1999) found that rural sites downwind of urban areas mighthave particularly high values of O3 in the middle of the day; 40–70 ppb insummer and 20–30 ppb in winter. The steady-state concentration of OH� wasestimated to be 5–6 × 105 molecules cm−3 (Crutzen 1982). Direct measurementshave been conducted by using laser long-path absorption or laser-induced fluo-rescence method based on the X2Π (ν″ = 0) → A2Σ+ (ν′ = 0) transition of OH�.The former method gave the OH� concentration of 4.3 (±0.4) × 106 moleculescm−3 in a sunny period but less in the nighttime (<1.5 × 106 molecules cm−3)(Dorn et al. 1995). The latter method showed similar values (3.4–6 × 106 mole-cules cm−3) in May and June (Holland et al. 1995). As laser irradiation alsoproduces OH� from the coexisting O3 as an artifact, ion-assisted mass spectrom-etry using 34SO2 has been applied (Crosley 1995). Estimated values in Coloradowere 2–4 × 106 molecules cm−3 smaller than expected from a photochemicalmodel, which could be accounted for by the presence of a quencher such asisoprene (2 ppb) in air. In other places, 1–10 × 106 molecules cm−3 was correctlyestimated.

O3 and gaseous pollutants in air are considered to be sorbed to plants andsoil surfaces, and such deposition is one of the important factors controllingtheir air concentrations. In the case of plant foliage, not only the direct interac-tion of O3 and OH� via sorption or reaction with epicuticular waxes but alsoreaction with epidermal and mesophyll cells and substomatal cavities after pas-sage through stomata is considered to play a role (Runeckles 1992; Cape 1997).The soil surface also acted as a sink of O3 (Turner et al. 1974; Fontan et al.1992; Cieslik and Labatut 1997). The uptake of O3 by plants was considered tobe mainly through stomata, and its flux over the vegetation was monitored (East-man et al. 1981). As a result, the deposition velocity over maize (max., 0.84 cmsec−1) was found to be about twice as large as that over grass, suggesting thatthe size of the stomatal aperture may be the predominant mechanism in O3

uptake. Wet and dry O3 deposition via stomatal or nonstomatal mechanismshave been studied in conjunction with aerodynamics over vegetation (Fowleret al. 2001; Zhang et al. 2002). Kerstiens and Lendzion (1989) examined non-stomatal deposition of O3 using isolated cuticle from various plant leaves anddemonstrated that its permeance via leaf is highly dependent on plant speciesand that either dust or hairs on leaf surface provides more degradation sites forO3. Based on these considerations, atmospheric conditions, especially for the


concentration of O3 and OH�, should also be taken into account when photodeg-radation pathways of pesticides on plant and soil surfaces are examined.

VI. Experimental Design and Kinetic AnalysisA. Light Source

Many kinds of conventional light sources with different spectral irradiance(Gould 1989a) have been utilized especially for photolysis studies of pesticides(Guth 1981; Roof 1982; Miller and Zepp 1983; Parlar 1990). The spectral com-parison of artificial light with natural sunlight indicates great differences (Fig.9) (Hirt et al. 1960). The most suitable light source is a xenon arc lamp; as itemits at <290 nm, an appropriate UV filter should be used. The glass and solu-tion filters commonly used in photolysis studies are each characterized by trans-mission of light at a specific wavelength range (Gould 1989a), and glass hasbeen preferred because of its simplicity. The most popular filter is Pyrex (orDuran) glass and its thickness (�4 mm) is also important for effective cutoff ofthe undesired shorter wavelengths (Zepp 1982). Cellulose acetate sheet is some-times unfavorable due to its solarization. If an appropriate glass and/or solutionfilter is used, the wavelength dependency of photolysis can be convenientlyestimated for better understanding of the photolytic mechanism (Schwack and

Fig. 9. Spectral irradiance of typical light sources used in photolysis studies. Graph isbased on data from Hirt et al. (1960).

32 T. Katagi

Kopf 1993; Schwack et al. 1995c). Even if natural sunlight is used, it should bekept in mind that a reaction vessel or the glass of the greenhouse can partiallyabsorb sunlight.

B. Photolysis Chambers

Ebing and Schuphan (1979) introduced a closed cultivating system made ofPyrex or Duran glass (3-mm thickness) and equipped with volatile traps underirradiation by fluorescent tubes to examine degradation profiles of dichlofluanid(205) with a good 14C recovery (96%–99%) in soil–plant (spinach, potato, andcress) systems. A volatilization chamber elaborately designed to simulate wellreal environmental conditions was developed to evaluate the dissipation profilesof methyl parathion (136) applied to French beans (Muller et al. 1995). Thechamber was connected with an air-conditioning unit to obtain the desired tem-perature, humidity, and flow rate of air that passes over the plants into volatiletraps, and the ceiling of the chamber was made of a special glass transmittimglight from a metal-halogenide lamp to simulate exposure to natural sunlight. Asimilar wind tunnel apparatus was successfully introduced to estimate volatiliza-tion and degradation profiles of fenpropimorph (227) on dwarf beans, sugarbeet, and radish (Ophoff et al. 1999). However, these apparati are not readilyavailable and their maintenance is difficult; therefore, photodegradation of pesti-cides on plants has been mostly examined with metabolism studies.

Many researchers have developed an apparatus for soil photolysis that canbe classified as a rotatory reaction vessel made of glass or thin-layer plate in achamber (Guth 1981; Choudhry and Webster 1985; Parlar 1990). The formersystem was introduced to examine the mineralization of pesticides on a silicagel surface (Parlar 1990), and its concept has been used to examine photolysisof diuron (53) adsorbed on sand, clays, and iron oxide (Jirkovsky et al. 1997).The latter system has been widely utilized, and its common design is illustratedin Fig. 10, based on the literature (Klehr et al. 1983; Katagi 1990; Misra et al.1997; Kromer et al. 1999; Balmer et al. 2000). The soil thin layer (thickness <2mm) prepared on a plate or vessel made of glass or stainless steel is attached tothe controlled temperature water bath, and sometimes a thermocouple buried inthe soil is utilized to monitor and control the soil temperature. Light intensityand its spectral distribution are monitored by a spectroradiometer. Because ei-ther diffusion of a pesticide molecule or photodegradation profiles in or on soilis very sensitive to soil temperature and humidity, some investigators (Misra etal. 1997; Kromer et al. 1999; Graebing et al. 2003) have also introduced arelative humidity sensor to the chamber equipped with a water spray nozzle andestablished a computerized system to automatically control humidity.

Good material balance is indispensable for precisely evaluating the photolyticprofiles of pesticides and thus the selection of appropriate traps is very impor-tant. Not only do volatile pesticides have a higher vapor pressure, most volatilesconsist mainly of CO2 and organic degradates with a small molecular size. Airflow under reduced pressure conditions was obtained using a suitable pump to


Fig. 10. Soil photolysis chamber. 1, soil thin layer (<2-mm thickness); 2, thermocouple;3, thermometer; 4, photoprobe connected by glass fiber; 5, spectroradiometer; 6, glassfilter (Pyrex); 7, thermostat-controlled water bath; 8, circulator; 9, xenon arc lamp; 10,power supply; 11, CO2-free humidified air; 12, traps.

avoid undesirable leakage from glass joints or seals instead of the pressurizedsystem. One of the traps is a liquid type, represented by aqueous alkaline solu-tion and organic solvents and the other is a solid type, for example, ascarite,charcoal, and porous polymers (Lewis 1976). CO2 is usually collected by using0.1–0.5 M KOH or NaOH in a gas-washing bottle and quantified by precipita-tion as BaCO3. Monoethanolamine is also used as a trapping medium (Yamaokaet al. 1988; Tanaka et al. 1991), and its efficiency can be improved by addingmethanol and a scintillation cocktail (Abbott et al. 1992). Ascarite has beenconveniently used to trap CO2 generated during photolysis of florasulam (48)(Krieger et al. 2000). When CO is generated, it can be catalytically convertedto CO2 using a combustion furnace (CuO at 650° C) followed by trapping asabove (Tanaka et al. 1991) or chemically trapping as cuprous complex using anacidic CuCl solution (Busch and Franklin 1979). Small organic volatiles areusually collected by using nonvolatile ethylene glycol, and its low solubilizingability toward organic molecules can be improved, for example, by addition ofa small volume of xylene. Evaporation of an organic solvent usually causesdifficulty in its use as a trapping medium, especially for longer periods, butcooling of the medium can improve its utility (Koshy et al. 1983). The cryogenictechnique using a dry ice–acetone mixture at −78° C can also be effective(Lewis 1976). As a solid trapping medium, acetone-washed polyurethane foam(Kromer et al. 1999) and porous polymeric sorbent such as Amberlite XADresins, Chromosorb, and Tenax (Lewis 1976; Smith et al. 1995; Ophoff et al.

34 T. Katagi

1999) have been used effectively. If organic volatiles can undergo fast and spe-cific chemical reaction in a trapping medium, it can become a useful trappingmethod. Tanaka et al. (1991) used dimedone (5,5-dimethylcyclohexane-1,3-dione) with a trace amount of pyridine to trap formaldehyde. For formic acidand acetic acid, Yamaoka et al. (1988) derivatized these using p-bromophenacylbromide in the presence of 18-crown-6.

C. Kinetic Analysis

When the reaction environment of a pesticide varies with its movement andadsorption, a simple first-order kinetics cannot be applied. In the foliar dissipa-tion of pesticides, the decline curve sometimes follows a two- or three-phasekinetics, each of which consists of a single exponential decline (first order).These are considered to correspond to the compartment models where move-ment of a pesticide between each compartment can be neglected. Gunther (1969)demonstrated the involvement of two dissipation processes for pesticides ap-plied to citrus fruit and found that the first faster dissipation stems from surfacedeposits in epicuticular waxes and the slower process from metabolism in therind. Similar approaches are utilized for many studies. Figure 11 shows the dif-ferences in decline profiles among simple first-order (single-phase), two- andthree-phase kinetics as examples. By considering a weight of vaporization lossfrom plant surfaces in the early stage after application, Stamper et al. (1979)analyzed crop residue data by ln-ln plots and statistically obtained the betterrelationship; R = a*t−3/2 (R, residue; t, days after application; a, constant). WhenFick’s second law of diffusion is applied, the dissipation of a pesticide can beapproximated by y0/(4πDt)3/2 (y0, initial deposit; D, diffusion constant), whichis in accordance with the statistical analysis. This information indicates the im-portance of controlling factors such as volatilization besides basic degradationmechanisms, and such an approach has been undertaken to account for dissipa-tion of pesticides from tea plants (Zongmao and Haibin 1997). The quantumchemical parameters were also introduced to examine photodegradation of poly-chlorodibenzodioxins on laurel cherry (Chen et al. 2001), and such an approachmay be useful.

In the case of soil photolysis studies, the decline of a pesticide usually doesnot follow the first-order kinetics and slows down with time, possibly due toeither adsorption to soil or movement out of a photic zone. Many investigatorshave applied the single- to three-phase models, but in some cases the second-order rate constant or Hoerl function [a * exp (b*t) * tc], where a, b, and c areconstants and t is an incubation period, has been proposed as a better relation-ship (Emmelin et al. 1993; Romero et al. 1998). The simpler equation based ona meaningful physicochemical assumption is desirable in the usual analysis ofexperimental data. Gustafson and Holden (1990) have focused on a spatial vari-ability in factors affecting dissipation rate in soil such as microbial population,light intensity, temperature, and soil properties. They assumed an infinite com-partment model where each compartment with a different dissipation rate is


distributed with some probability and introduced the concept that the rate con-stants follow the Γ distribution. The simple equation, y = (1 + b*t)−a, can bederived with a half-life of (0.5−(1/a) − 1)/b (y, % of the applied dose; t, time; a, b,constants); the dissipation curve is shown in Fig. 11. Data analysis using theseapproaches helps to understand not only persistence of a pesticide but also thedissipation mechanisms involved.

VII. Photodegradation of Pesticides in Model SystemsA. Soil Surface Models

Glass, silica gel, or clay have been utilized as simple models by consideringheterogeneity and variability of soil affecting photodegradation profiles of pesti-cides (Hulpke et al. 1983). However, the adsorptive nature of soil cannot betaken into account on glass. This effect may be partly realized in silica gel orclay, but the higher reactivity of their surface originating from many types ofsilanol groups and adsorbed water would give different reaction environments.Furthermore, more tightly packing may reduce the depth of light penetrationcompared with soil. Although the contribution of soil humic substances actingas a photosensitizer, quencher, or solubilizing medium is completely neglectedin either of these models, their easier handling makes them the first useful ap-proach to evaluate soil photolysis of pesticides. Treatment of silica gel or clay

Fig. 11. Typical decline curves. When period and percent (%) of the applied dose are“t” and “y,” respectively, each curve can be defined as follows: single-phase, y =exp(−a*t), a = 0.139; two-phase, y = a*exp(−b*t) + c*exp(−d*t), a = 0.6, b = 0.139,c = 0.4, d = 0.0139; three-phase, y = a*exp(−b*t) + c*exp(−d*t) + e*exp(−f*t), a = 0.4,b = 0.139, c = 0.3, d = 0.0139, e = 0.3, f = 0.00693; Gustafson, y = (1 + b*t)−a, a = 1.5,b = 0.117.

36 T. Katagi

with humic substances can be alternatively considered, but such approaches arevery limited (Schafmeier et al. 1998). The most frequently reported system isthe aqueous soil suspension (Pelizzetti et al. 1990; Mansour et al. 1997; Hustertet al. 1999), but the excess amount of water may alter the reaction environmentor unexpectedly increase the contribution either from direct or indirect photoly-sis in an aqueous phase containing dissolved humic substances. Furthermore,the filter effect by suspended matters may reduce the rate of photolysis (Zeppand Schlotzhauer 1981), and the adsorption to soil may be underestimated forpartially water-soluble pesticides. Furthermore, even if the soil thin layer with1- to 2-mm thickness is used, diurnal variation of soil temperature and moistureis difficult to determine (Miller et al. 1989; Reichman et al. 2000b). Thesedifferences would change the extent of vaporization loss of pesticide from soilsurface and misstate the rate of photoinduced dissipation by neglecting transportof pesticide or reactive oxygen species via diffusion along with the movementof water or air in soil (Ehlers et al. 1969b; Hubbs and Lavy 1990; Donaldsonand Miller 1996; Balmer et al. 2000). The few approaches elaborately control-ling these factors have been carefully developed (Misra et al. 1997; Kromer etal. 1999; Frank et al. 2002).

B. Plant Surface Models

The simplest model is the glass surface, but the reaction environment is verydifferent from the cuticular surface. From this point of view, Peacock et al.(1994) have briefly examined an inactive polytetrafluoroethylene plate. Consid-ering the wax chemistry described in Section III.E, many researchers have con-veniently examined photodegradation of a pesticide in simple organic solventsas surrogates of waxes, but their significantly different fluidity and simple struc-tures should be kept in mind together with easier photoaddition of a solventmolecule. Schwack (1988, Schwack et al. 1994) used methyl oleate and 12-hydroxystearate as more elaborate models of epicuticular wax. Photolysis of2,4-D (1) has been reported to be enhanced on Zea mays leaves and thus a morerealistic model has been considered (Venkatesch and Harrison 1999). Photodeg-radation of carbamate and organophosphate pesticides was examined in thinfilm of epicuticular waxes extracted from a variety of citrus fruits (Cabras et al.1997b; Pirisi et al. 1998, 2001). Schuler et al. (1998) examined photodegrada-tion of dibenzo-p-dioxins including (129) on glass coated with waxes of laurelcherry leaves. The photolysis rate of fenarimol (239) was dependent on plantspecies (Watkins 1987). Because plant cuticles can be isolated from intact leavesby treatment with pectinase and cellulase, Schynowski and Schwack (1996) con-ducted photodegradation of parathion (135) on enzymatically isolated cuticles.

C. Photodegradation of Pesticides on Glass and Silica Gel Surfaces

Glass plates (Chukwudebe et al. 1989) and silica gel (Hirayama et al. 1998)were utilized to examine the comparative photoreactivity of various pesticides.Any significant relationship between the photolysis rate on glass at λmax = 300


nm and the extinction coefficient of each pesticide at 295–305 nm could not beidentified, but the slower degradation was observed for the thicker layer ofpesticide on glass (Chen et al. 1984). Photolysis rates were greatly reduced atthe concentration of 3.3 µg cm−2, corresponding to the thin-layer thickness of�100 A. Since Kitchener (1946) reported that most of light passing through acrystal is absorbed along the pathlength of �100 A, this reduction was likely tooriginate from light attenuation. Furthermore, the different profiles of UV ab-sorption in the solid state from those in solution (Gab et al. 1975b; Leermakerset al. 1966) may account, at least in part, for this insignificant relationship. Incontrast, Calumpang et al. (1984) found a good correlation between maximummolar absorptivity in solution and photolysis rate for eight organophosphateinsecticides on silica gel. On these solid surfaces, the photoinduced homolyticcleavage of a bond to produce radicals is considered to be one of the mostimportant degradation pathways. Johnston et al. (1984) studied photodegrada-tion of azobis(isobutyronitrile) on dry silica gel by using UV light and demon-strated that some portion of radicals could escape from their original partnersby a translational motion. Avnir et al. (1981) also examined the reaction profilesof radicals by using benzyl phenylacetate and dibenzyl ketone. By comparingthe amount of dibenzyl formed in potassium dodecanoate micelles via recombi-nation of radicals, they concluded that radical pairs separated more easily onsilica gel surface by a translational motion. Furthermore, this trend was moreemphasized for dibenzyl ketone generating radicals via the triplet state com-pared with benzyl phenylacetate via the singlet state. Therefore, if the pesticidemolecule deposited on silica gel surface undergoes photoinduced homolyticcleavage of some bond, the recombination process may be less important. Thephotodegradation profiles of pesticides on glass and silica gel are summarizedin Table 7 (see table on page 94) from a survey of the existing literature.

Organochlorines Photoinduced dechlorination of pentachlorophenol (121)gave the π-radical and successively the phenoxide (Piccinini et al. 1998). Thephotolytic half-life was dependent on the solvent used to prepare a thin film onglass, and a residual amount of water was found to increase the photolysis rate.Aldrin (122) on glass underwent epoxidation to dieldrin (123) followed by fur-ther isomerization to photodieldrin (124) (Rosen and Sutherland 1967). In thecase of endosulfan (125), the ring opening to form the diol derivative via releaseof SO was a major pathway but without S-oxidation (Dureja and Mukerjee1982). The other cyclodienes, including chlordane (128), were found to formthe corresponding cage structure derivatives (Benson et al. 1971). More epoxi-dation and hydroxylation of (128) on silica gel implied involvement of reactiveoxygen species on the surface formed by irradiation (Gab et al. 1975a). DDT(130) on glass primarily underwent photoinduced homolytic cleavage of theC−Cl bond at the trichloromethyl group to form DDD (132) by exposure to UVlight at 254 nm (Mosier et al. 1969). The radical mechanism was also supportedby comparative photolysis of eight 3H-diethoxy analogues of (130) on glass(Coats et al. 1979). Relative photostability decreased by substituting the CCl3

38 T. Katagi

moiety with other groups as follows: CCl3 (130) >> CHCl2 (132) > CHCl2CH3

>> CCl(CH3)2. This order was in agreement with the stability of radical speciesformed via C–Cl cleavage.

Organophosphorus Esters Photoinduced oxidation of the P=S moiety was ob-served for parathion (135) and its methyl analogue (136) on glass (El-Refai andHopkins 1966; Calumpang et al. 1984), together with formation of S-isomers(Chukwudebe et al. 1989). Fenitrothion (138) on silica gel underwent oxidationat the aryl methyl group to COOH and/or P=S moiety to the oxon together withan ester cleavage giving the corresponding phenol (Ohkawa et al. 1974b). O-Demethylation was observed for the rapid photodegradation of cyanophos (137)on silica gel in addition to oxon formation and cleavage of the P−O aryl bond(Mikami et al. 1976). The photoinduced S-oxidation of the methylthio group tosulfoxide was the primary reaction on glass for fenthion (143) (Cabras et al.1997b). Hirahara et al. (2001) examined comparative photodegradation of (143)using UV-A (320–400 nm), UV-B (280–320 nm), and UV-C (250–260 nm)light. Because (143) has a UV absorption at the UV-B–UV-C region, the easeof photodegradation was UV-C > UV-B > UV-A. Photoinduced dehalogenationwas additionally observed for iodofenphos (141) on glass (Walia et al. 1989b).Similar photodegradation profiles of chlorpyrifos (145) were more quantitativelyinvestigated (Walia et al. 1988; Racke 1993). Although the degradation productswere not identified, Meikle et al. (1983) utilized Whatman No. 1 filter paper asa leaf model and examined rates of either photolysis or volatilization in thepresence of carruba wax. When the aryl moiety is transformed from simplephenyl rings to heterocycles, similar phototransformation is basically observed.Oxidation of the P=S moiety concomitant with the P-Oaryl ester cleavage pro-ceeded on glass for quinalophos (148) (Dureja et al. 1988) and pyridafenthion(150) (Tsao et al. 1989). Although dioxabenzofos (183) possesses a unique cy-clic structure, the photoreactions on silica gel obeyed similar mechanisms (Mi-kami et al. 1977b). Phoxim (152) gave the same photoproducts on glass andtomato leaf but their chemical identification was not extensively conducted(Makary et al. 1981).

When 14C- or 32P-phenthoate (168) on glass was exposed to sunlight, about90% was lost by volatilization after 40 hr, and 20%–35% of the residual radio-activity was due to its oxon. The volatilization loss was greatly reduced on silicagel, with the main product being the oxon (Mikami et al. 1977b). 14C-Sulprofos(161) was oxidized to the sulfoxide and sulfone similarly as (143) (Ivie and Bull1976). The basic photochemistry was almost the same for propaphos (159) ei-ther on glass or silica gel and was characterized by the significant formation ofthe S-oxidized derivatives (Fujii et al. 1979). Direct photolysis is consideredmost unlikely for dimethoate (165), malathion (167), phorate (162), and disulfo-ton (163) not having chromophores in the molecules. The hydrolysis productswith a trace amount of the oxon were detected only for sunlight photolysis of32P-(165) (Dauterman et al. 1960). Loss of (167) from the glass surface wasmainly due to thermal vaporization (Awad et al. 1967; El-Refai and Hopkins


1972). Phorate (162) was only photodecomposed to the oxon at 254 nm andthus sunlight photolysis was considered unlikely (Sharma and Gupta 1994). In-significant involvement of direct photolysis for (163) was clearly demonstratedby degradation only at 250–260 nm by Hirahara et al. (2001). UV irradiationof phosalone (170) on glass resulted in dechlorination and cleavage of eachbond at the PSCH2N linkage but without any P=S oxidation (Walia et al.1989a). Edifenphos (173) exhibited slow degradation under UV irradiation (Ishi-zuka et al. 1973).

Stereospecific oxidation of the P=S moiety to the oxon was reported for 3H-S-2571 (176) on silica gel using UV light (Mikami et al. 1977a). Katagi (1993a)proposed, in photolysis of butamifos (177), the N-sec-butyl analogue of (176),the photoinduced intramolecular oxidation of the P=S moiety by the adjacentnitro group attached to the o-position of the phenyl ring, which may account forthis stereospecificity. Dureja et al. (1989) reported photoinduced oxidation ofthe P=S moiety and ester cleavage for isofenphos (175) on glass. 32P-Leptophos(181) on silica gel was photodegraded with formation of oxon, O-demethylatedand debrominated derivatives, and O-methyl phenyl thiophosphonic acid thatwere finally degraded to phenyl phosphonic acid (Zayed et al. 1978). Both oxi-dation of the P=S moiety and ester cleavage were the main pathways for (181)on glass (Riskallah et al. 1979) and for cyanofenphos (180) on silica gel (Mi-kami et al. 1976) under sunlight. These results show the insignificant differencesin photochemistry among phosphorothioates, phosphoramidothioates, and phos-phonothioates. Monocrotophos (156) (Dureja 1989; Lindquist and Bull 1967),phosphamidon (158) (Bull et al. 1967), dichlorvos (153), and trichlorfon (179)(Derek et al. 1979) do not have any chromophore to absorb sunlight and thusdirect photolysis was most unlikely.

Pyrethroids Chen and Casida (1969) studied photodegradation of the 14C-labels of pyrethrin I (9) and allethrin (10) on glass and identified three possibleoxidation pathways. One of these was the successive oxidation of the trans-methyl group of the 2-methylprop-1-enyl moiety via CH2OH and CHO andfinally to the COOH derivative; the other two pathways were formation of trans-caronic acid derivative, possibly via ozonide and oxidation at 1-position of the2-methylprop-1-enyl moiety. Involvement of oxygen species was separatelydemonstrated by the increased stability in the presence of an antioxidant suchas dibutylhydroxytoluene (Abe et al. 1972). Isobe et al. (1984) reported thephotoinduced opening of the cyclopropyl ring of (10) followed by either sigma-tropic rearrangement to the acrylate or oxidadtive destruction to the mixtures ofglyoxylates. Ruzo et al. (1980) detected the di-π-methane rearrangement of the2-(prop-2-enyl)cyclopent-2-enone moiety of S-bioallethrin (12) on glass to formthe cyclopropyl derivatives, but the cis/trans isomerization was minimal. 14C-Resmethrin (15) on silica gel, glass, or filter paper underwent either epoxidationof the 2-methylprop-1-enyl moiety or ester cleavage similarly as (10) (Ueda etal. 1974). These unique reactions were initiated by oxidation of the furan ring,possibly to give a cyclic ozonide-type peroxide intermediate (Fig. 12). Reduc-

40 T. Katagi

Fig. 12. Photooxidative rearrangement of resmethrin (15).

tion of this intermediate to the diol followed by rearrangement resulted in forma-tion of the cyclopentenolone derivative, especially on silica gel. Migration ofproton or hydrogen radical from the position symmetrical to the benzyl groupor that of the benzyl cation or radical gave the hydroxylactone and benzyloxy-lactone derivatives, respectively.

Samsonov and Makarov (1996) examined the photostability of (15) on glassunder sunlight and found that the oxidative degradation by O2 was insensitiveto thickness of thin film and likely to be controlled by a filter effect of thinfilm. Tetramethrin (23) underwent successive photooxidation at the acid moietysimilar to (10) (Chen and Casida 1969). Ruzo et al. (1982) investigated thephotodegradation of phenothrin (13) and (23) on glass and demonstratedinvolvement of oxygen species such as 3O2,

1O2, and O3. The ene reaction of 1O2

(see Fig. 2, reaction 7) was confirmed by formation of 2-methyl-1-hydroperoxy-prop-2-ene-1-yl and 2-methyl-1-hydroxyprop-2-ene-1-yl derivatives. For (23),hydroxylation at the 3-position of the 3,4,5,6-tetrahydrophthaloyl moiety oc-curred but to a lesser extent. Although the degradation products were not re-ported, the very rapid photodegradation of cyphenothrin (14) was observed onsilica gel possibly via photoreactions similar to (13) (Dureja et al. 1984). Inaddition to the usual photoinduced isomerization in the acid moiety togetherwith epoxidation, kadethrin (16) underwent opening of the 2-oxo-3-thiacyclo-pentylidene ring on glass (Ohsawa and Casida 1979). Trace amounts of benzy-loxylactone derivatives were detected similarly to (15) but without formation ofthe hydroxycyclopentenolone.

Photoinduced cis/trans isomerization mainly proceeded for deltamethrin (22)on glass under sunlight, and neither photooxidation nor debromination was de-tected (Ruzo et al. 1977). Maguire (1990) reported the isomerization of 1R-cis-isomer to 1S-cis-, 1R-trans-, and 1S-trans forms by chiral HPLC analysis. The


other reactions were ester cleavage to form the corresponding acid, α-cyano-3-phenoxybenzyl alcohol, and 3-phenoxybenzaldehyde together with decarboxyl-ation (see Fig. 2, reaction 4). The dimethylacrylate derivative was also detectedat a trace amount similar to (10). Cyhalothrin (21) exhibited the similar photore-actions to (22) on glass (Ruzo et al. 1987). Tralomethrin (25) and tralocythrin(26) were mainly phototransformed to (22) and cypermethrin (19) with theirtrans-isomers, respectively (Ruzo and Casida 1981). The 1′-bromo derivativeswere also formed possibly via intramolecular abstraction of hydrogen at the 1′-position by bromine homolytically being photodissociated. Many pyrethroidshave the 3-phenoxybenzyl or α-cyano-3-phenoxybenzyl moiety, and the intro-duction of the cyano group has been demonstrated not to significantly affectphotoreactivity either in solution or on glass (Ruzo and Casida 1982). Holm-stead et al. (1978b) reported that the main photo-reaction of fenvalerate (27) onglass is decarboxylation. Homolytic cleavage of either (C=O)O−CH orC(=O)−OCH bond has been evidenced by detection of many relevant photo-products. By exposure to sunlight, flucythrinate (29) was photodegraded onglass via almost the same pathways as (27) (Chattopadhyaya and Dureja 1991).Although the NH linkage was additionally introduced to the acid moiety, almostthe same photoreactions were reported for fluvalinate (30) (Quinstad and Staiger1984). Sunlight exposure resulted in formation of formanilide, probably due toreaction of haloanilide with photochemically produced formaldehyde, but nodecarboxylated derivative of (30) was detected on glass. Acrinathrin (31) onglass was photodegraded to the corresponding acid and alcohol moieties viaester cleavage (Samsonov and Pokrovskii 2001). The predominant photodegra-dation process of etofenprox (32) on glass was the photooxidation of the benzylmoiety to benzoyl, whereas the unique product formed by loss of the CH2Omoiety in solution photochemistry was not detected (Fig. 13). The benzyl radical

Fig. 13. Photodegradation of etofenprox (32).

42 T. Katagi

would be possibly formed by hydrogen abstraction, which reacted with O2 tothe hydroperoxy derivative followed by its dehydration to the benzoyl derivative(Class et al. 1989; Tsao and Eto 1990b).

Carbamates Substituted phenyl N-methylcarbamates are commonly photode-graded via successive oxidation of the N-methyl group on glass or silica gel(see Fig. 2, reaction 6) (Abdel-Wahab et al. 1966). Aminocarb (66) or mexacar-bate (67) were photodegraded on silica gel at 254 nm to more than 10 photo-products including the N(CH3)CHO and NHCHO derivatives (Abdel-Wahab andCasida 1967). Because the same products were detected in photolysis of (66)on glass at >290 nm, the oxidation process was likely to occur in the environ-ment (Pirisi et al. 2001). This oxidation was also reported for pirimicarb (78)on glass and cellulose plates, and involvement of OH� was assumed (Pirisi etal. 1996, 1998). Methiocarb (68) underwent photoinduced oxidation of the meth-ylthio group on wax-coated glass to form the corresponding sulfoxide and sul-fone, while it was degraded to unknowns on glass (Pirisi et al. 2001). In thecase of benfuracarb (89) on glass, the photocleavage of carbamate linkage atthe N−C(=O) bond gave carbofuran (72), which was further photodegradedto the corresponding phenol (Dureja et al. 1990). At the same time, eitherN(CH3)−C or N(CH3)−S bond was cleaved by irradiation to form N-(2-ethoxy-carbonylethyl)-N-isopropylsulfenamine and its derivative (Fig. 14). Photodegra-dation of benthiocarb (86) gave mainly 4-chlorobenzoic acid via the correspond-ing alcohol and aldehyde with insignificant S-oxidation (Ishikawa et al. 1977).Either N-deethylation or hydroxylation at the 2-position of the phenyl ring wasa minor pathway, the latter of which was characteristic of photolysis on glass.These photoreactions were also observed on silica gel but with a slower photo-degradation rate (Cheng and Hwang 1996). Photoinduced homolytic cleavage

Fig. 14. Photodegradation of benfuracarb (89).


of the carbonyl C−S bond gave the benzyl thiol and its dimer (Ruzo and Casida1985). The radicals produced via cleavage of the benzylic C−S bond reactedwith O2 to form the series of alcohol-to-acid derivatives or gave benzyl N,N-diethyl carbamate or benzylamine via release of either sulfur or O=C=S, fol-lowed by recombination with the 4-chlorobenzyl radical. N-Methylcarbonyl-N-ethyl derivative was also detected as a major product on glass, and involvementof OH� was proposed. Cartap (91) was thought to undergo photocleavage of thethiocarbamate S−C(=O) bond to give the radical, followed by intramolecularcyclization to nereistoxin on either glass or silica gel (Tsao and Eto 1989). Thephotoinduced homolytic cleavage of the carbamate C(=O)−O linkage was mostlikely for phenmedipham (84) on silica gel by detection of N,N′-ditolylurea fromthe reactive isocyanate (Emmelin et al. 1998). Schafmeier et al. (1998) reportedthat the photolysis of (84) on silica gel was highly dependent on coexistinghumic substances. In the case of fenothiocarb (85), photoinduced oxidation atsulfur mainly proceeded on silica gel, followed by cleavage of the carbamatelinkage to the very reactive intermediate sulfenic acid that was readily decom-posed to 4-phenoxybutylsulfonic acid (Unai and Tomizawa 1986). Thiophanatemethyl (92) was rapidly photodegraded on glass via conversion of the C−Sgroup to ketone and via intramolecular cyclization to MBC (93) (Soeda et al.1972). MBC (93) was found rather stable on silica gel, but its photodegradationwas accelerated by a sensitizer such as riboflavin (Fleeker and Lacy 1977).

Amides, Anilides, and Dicarboximides Alachlor (34) underwent photoinducedcleavage of either the N−CH2 or N−C(=O) bond on glass finally to the corre-sponding aniline, together with dechlorination and intramolecular cyclizationto the indoline derivative (Fang 1977). Similar photodegradation profiles werereported for butachlor (36) when irradiated at 254 nm, together with the photo-substitution of Cl with OH followed by intramolecular cyclization to N-2′,6′-diethylphenyl-2,5-dihydrooxazol-4-one (Chen and Chen 1978). These herbicidespossess insignificant absorption at >290 nm and thus the direct photolysis wasconsidered unlikely in the environment. Either N−C(=O) or N-aryl bond ofmepronil (38) was slowly cleaved on silica gel by sunlight to form benzamideand benzoic acid, followed by stepwise oxidation of the o-methyl group togetherwith p-hydroxylation at the aniline moiety, but only as a trace amount (Yumitaand Yamamoto 1982). Although photodegradation was found insignificant at 254nm, flutolanil (39) underwent O-deisopropylation and photo-Fries rearrangement(see Fig. 2, reaction 9b) to give 2-aminobenzophenone derivative on either silicagel or glass (Tsao and Eto 1991). The photo-Fries rearrangement of amides at254 nm has been reported on dry silica gel by Abdal-Malik and de Mayo (1984),and radical pairs formed were considered not to separate on the surface. Thephotolysis mechanism on silica gel was investigated for analogues of (38) hav-ing different o-substituents (Yumita et al. 1984). They proposed involvement oftwo pathways: one is the N−C(=O) bond cleavage with the formed anilinebeing polymerized and the other is the hydroxylation at p-position of the anilinemoiety followed by cleavage of the N-aryl bond. Carboxin (42) exhibited rapid

44 T. Katagi

photodegradation on glass, probably via oxidation at the oxathiine sulfur to sulf-oxide and sulfone (Buchenauer 1975). Niclosamide (40) underwent extensivephotodegradation either on glass or silica gel to chlorosalicylic acid via cleavageof the N−C(=O) bond (Schultz and Harman 1978). In contrast, naproanilide(41) exhibited homolytic cleavage of the CH−O bond or photooxidation at themethine carbon to form 2-hydroxypropananilide at >254 nm on glass (Tsao andEto 1990a). Unique photoreactions were observed for isoxaben (46) on silicagel (Mamouni et al. 1992). The N-O bond in the isoxazole ring was first photo-cleaved and recyclized to the three-membered azirine derivative whose ring wasagain opened at the C-C bond to form the oxazole derivative (Fig. 15). It wasconsidered that these compounds converted to each other under irradiation, andthe azirine and oxazole derivatives were photodegraded to 2,6-dimethoxyben-zamide followed by reduction to the corresponding benzonitrile. Concerningimide pesticides, Sumida et al. (1973) examined the photolysis of experimentalfungicide DDOD (113) on glass but without detailed information on degradates.

Ureas Diflubenzuron (59) was photodegraded on glass or silica gel to 4-chlo-rophenyl isocyanate and 2,6-dichlorobenzamide, indicating involvement of pho-toinduced cleavage of the central C-N bond via NH hydrogen abstraction by theexcited-state carbonyl oxygen in the six-membered ring transition state (Ruzoet al. 1974). Almost half of 14C-(59) was lost from silica gel during 28 d withtrace formation of unknowns (Bull and Ivie 1976). Diafenthiuron (57) was rap-idly photodegraded on Teflon sheets to give the corresponding urea throughcarbodiimide by reaction with 1O2 (Drabek et al. 1992). Chlorsulfuron (96) on

Fig. 15. Photoinduced rearrangement of isoxaben (46).


silica gel exhibited slow photodegradation to give the corresponding aminotri-azine and benzenesulfonamide derivatives via cleavage of the sulfonylureabridge (Herrmann et al. 1985). UV spectrum of (96) in methanol did not showany absorbance at >290 nm and no bathochromic shift was observed by adsorp-tion onto silica gel, implying involvement of indirect photolysis such as thereaction with OH�. Very insignificant photodegradation on glass was reportedfor the few sulfonylurea herbicides, and the presence of surfactants in formula-tion may play a great role in its indirect photolysis in the real environment(Thomas and Harrison 1990; Harrison and Thomas 1990). Photoinduced cleav-age of either bond at the NH−C(=O)−N(CH3)-triazine moiety or contractionof the sulfonylurea bridge was reported for tribenuron-methyl (99) on glass(Bhattacharjee and Dureja 2002).

Azoles and Triazines Rapid photodegradation of triadimefon (188) was ob-served on glass, and the cleavage either of O-CH or CH−C(=O) bond gave thecorresponding 1N-substituted 1,2,4-traizole derivatives (Nag and Dureja 1996).Especially under UV light, 1-(4-chlorophenoxy)-1-(1H-1,2,4-triazol-1-yl)-2,2-dimethylpropane was identified as a main photoproduct, suggesting that a con-certed process involving simultaneous combination with loss of CO might pro-ceed rather than simple coupling of the discrete free radicals after loss of theCO moiety. Triadimenol (189) underwent dechlorination and cleavage of eitherCH-Oaryl or C-N bond when irradiated on glass (Clark and Watkins 1986).Diniconazole-M (190) showed photoinduced E/Z isomerization followed by in-tramolecular cyclization between 5-positions of the 2,4-dichlorophenyl and1,2,4-triazolyl rings (Sharma and Chibber 1997). The secondary alcohol moietyof this cyclized product was oxidized to the corresponding ketone, and succes-sive opening of the hetero ring gave the isoquinoline derivative (Fig. 16). Photo-induced cleavage of the C-triazole bond eliminating 1,2,4-triazole was observedfor propiconazole (191) on glass (Dureja et al. 1987a). Fluotrimazole (195) ex-

Fig. 16. Photoinduced isomerization of diniconazole-M (190) followed by cyclization.

46 T. Katagi

hibited the similar homolytic cleavage of the C-triazole bond on glass followedby reaction with water to give the corresponding triphenylmethanol (Clark et al.1983). The photolytic stability of triazine herbicides on glass was briefly studiedin comparison with their solution photolysis (Chen et al. 1984).

Miscellaneous Direct photolysis was found to be of minor importance for 2,4-D (1) in accordance with its insignificant UV absorption at >300 nm (Venkateshand Harrison 1999). In contrast, the dimethylamino derivative of MCPA (3) wasphotochemically produced from the countercation N,N-dimethylamine (Crosbyand Bowers 1985). In the presence of trace water, (3) was considered to bephotodegraded via dechlorination, decarboxylation, and oxidation to many smallmolecules. Significant photodegradation of trifluralin (232) by exposure to sun-light was demonstrated by reduced herbicidal activity, but no information onthe degradation pathway was given (Wright and Warren 1965). 14C-Fluchloralin(236) on silica gel and glass was photodegraded via either release of the chloro-ethyl group or intramolecular cyclization between the nitro group and 1-positionof the N-propyl moiety to give benzimidazole derivatives together with the un-usual formation of the quinoxaline derivative (Nilles and Zabik 1974). Thistype of reductive cyclization seems common to dinitroaniline herbicides, as alsodemonstrated by photodegradation of pendimethalin (238) on glass (Dureja andWalia 1989). Rapid photodegradation of isoprothiolane (204) on silica gel in-volved a dithiolane ring cleavage, ester hydrolysis, decarboxylation, heterocy-cles formation such as dithietane and trithiolane and sulfur liberation, and finallythe accumulation of S8 was observed (Chou et al. 1980). 14C-Methoprene (246)quickly dissipated on glass by photolysis and volatilization (Quinstad et al.1975). The main photoreaction was E/Z isomerization at 2-ene position to give50 : 50 mixture of (2E,4E) and (2Z,4E) isomers. 7-Methoxycitronellal was iden-tified as one of the main volatiles and considered to be formed via oxidation at5-position. Sethoxydim (223) was found very unstable, and N-deethoxylatedwas the only derivative identified (Campbell and Penner 1985a). Soeda et al.(1979) investigated the photodegradation of 14C-alloxydim (224) on silica geland found that the main pathway was N-deallyloxylation similar to (223), and(224) also underwent Beckmann rearrangement to give two types of oxo-tetra-hydrobenzoxazole derivatives but in lesser amounts.

Bentazone (200) possessing fairly strong absorption at around 300 nm under-goes direct photolysis (Nilles and Zabik 1975). 14C-(200) was lost from a silicagel surface mainly due to volatilization, whereas photoinduced oxidation of theNH moiety proceeded on glass followed by elimination of SO2 to give N-isopro-pyl-o-nitrosobenzoylamine and the successive oxidation to the nitro derivative.For buprofezin (222) on glass, the few types of ring opening were caused bysunlight, resulting in formation of ureas and thioureas (Datta and Walia 1997).Thiabendazole (212) showed very slow sunlight photodegradation on glass viaopening of the thiazole ring to benzimidazole-2-carboxamide and benzimidazole(Jacob et al. 1975). Photooxidative breakdown of one phenyl ring was observedfor diquat (226) on silica gel, leading to formation of 1,2,3,4-tetrahydro-1-oxo-


pyrido[1,2-a]-5-pyradinium salt and picolinamide (Smith and Grove 1969). Thephotodegradation of fipronil (220) on silica gel, glass, and paper gave the desul-finyl derivative with trace amounts of sulfone and sulfide derivatives, possiblyvia photoinduced oxidation and reduction (Hainzl and Casida 1996). The desul-finylation was assumed to occur from the hydrogen-bonded six-membered inter-mediate formed between NH2 and SOCF3 groups (Fig. 17). Perfluidone (206),having sufficient UV absorption at 330 nm, underwent direct photolysis proba-bly via photochemical breakdown of the CF3SO2NH moiety (Ketchersid andMerkle 1975). The hydrolytic degradation of 14C-chlordimeform (207) to N-formyl-4-chloro-o-toluidine was accelerated by sunlight exposure on silica gel(Knowles and Sen Gupta 1969). 14C-Guazatine (245) gave a very odd photo-product on glass having a carbonyl moiety with a molecular weight greater by28 than (245) (Sato et al. 1985b). The degradate was considered to be formedby photooxidation of the methylene group at 4-position to the central NH moi-ety, followed by methylation at the adjacent methylene carbon. Stepwise de-phenylation was observed for fentin acetate (241) on silica gel when exposed toUV light, finally to an inorganic tin (Barnes et al. 1973). Photooxidation to thebenzoyl derivative was the predominant photodegradation pathway of cinmethy-lin (249) (Grayson et al. 1987). Imazaquin (230) and imazethapyr (231) photo-decomposed on glass and silica gel, probably via decarboxylation or ring de-composition through stepwise oxidation (Basham and Lavy 1987; Goetz et al.1990; Schroeder 1997).

Azadirachtin-A (253) underwent rapid photoisomerization at the (E)-2-meth-ylbut-2-enoate moiety to the Z-isomer on glass (Dureja and Johnson 2000). Atleast 10 primary degradates were formed from avermectin B1a (250) on glassthrough sunlight irradiation, but direct photolysis was unlikely due to lack ofUV absorption at >290 nm (Crouch et al. 1991). The main pathway was inser-tion of oxygen at the 14- or 15-position of the macrocycle with accompanyingdouble-bond shift, probably via formation of an allylic hydroperoxide from 1O2

by the ene-type reaction. Oxidation at the 8α-position, possibly by reaction withO2 to form the intermediate hydroperoxide, was also observed. For avermectinB1a analogue MAB1a (251), photolysis on glass was slightly accelerated com-pared to (250), but no oxidation at the most photosensitive 14- and 15-positionswas observed (Feely et al. 1992). Alternatively, photoinduced isomerization at8- and 9-positions, oxidative N-dealkylation, and cleavage of the ether linkagein the sugar region were observed.

D. Photodegradation of Pesticides in Organic Solventsand Plant Model Systems

Photodegradation profiles of pesticides in organic solvents and thin films offatty acids as plant surface models are summarized in Table 8 (see table on page101). Examples of photodegradation in more complex media such as thin filmsprepared from the extracted epicuticular waxes or enzymatically isolated cuticlesare listed in Table 9 (see table on page 104).

48 T. Katagi

Fig.

17.

Var

ious

phot

odeg

rada

tion

path

way

sof

fipr

onil

(220

).


Organochlorines Photolysis of DDT (130) and methoxychlor (134) was con-ducted in methyl oleate as a representative of octadecanoic acids in plant cuti-cles (Schwack 1988). The radicals produced via homolytic dechlorination re-acted at the C=C double bond of methyl oleate as well as a chlorine radical toform stearic acid derivatives and also abstracted hydrogen from methyl oleateto form the corresponding dichloromethyl derivatives. Dechlorination also oc-curs at the aryl moiety of anilazine (211) in cyclohexene with irradiation, andthe radicals produced reacted with either solvent molecules or methyl oleate(Breithaupt and Schwack 2000). Jahn et al. (1999) confirmed the bound forma-tion of chlorothalonil (117) on the enzymatically isolated tomato cuticles underirradiation by using enzyme-linked immunosorbent assay. Dioxin, 2,3,7,8-TCDD(129), underwent either dechlorination at 8-position by exposure to UV light orrearrangement to biphenyl derivative in isooctane (Kieatiwong et al. 1990).Schuler et al. (1998) reported the photoinduced dechlorination of (129) in a thinwax film of laurel cherry leaves. Photoinduced homolytic dechlorination fol-lowed by reaction with unsaturated C=C bonds was most likely to occur onplant cuticles. Endosulfan (125) exhibited photoinduced isomerization in hexanefrom the α-isomer to the β-isomer but with loss of two chlorine atoms at thebridged carbon (Dureja and Mukerjee 1982). Heptachlor (127) gave 1-exo-hydroxychlordene via substitution of Cl with a hydroxyl group, which under-went either (2π + 2π) cycloaddition to the full-cage isomer or intramolecularene-reaction, finally forming the cyclic ketone (Parlar et al. 1978).

Organophosphorus Esters Photochemistry of this chemical class has been ex-tensively reviewed by Floßer-Muller and Schwack (2001). Schwack (1987) andSchwack et al. (1994) examined the effect of a reaction medium on photodegra-dation profiles of parathion (135). UV irradiation of (135) in cyclohexenecaused reduction of the nitro group followed by addition of cyclohexene to thenitroso group via ene-type reaction. Detection of azo and azoxy dimers of (135)indicated involvement of stepwise photoreduction of the nitro group to aminovia nitroso and hydroxyamino groups (Fig. 18). The main product in 2-propanolwas the azoxy dimer, part of which rearranged to the 2-hydroxyazo derivativewith no detection of the azo dimer. The amounts of these dimers greatly de-creased in cyclohexane containing methyl 12-hydroxystearate (ester of a cutinacid) with predominant formation of the oxon. These findings imply that thereaction medium is one of the most important factors controlling the photopro-cess of (135), and the proton-donating ability of the solvent molecule may playa large role. These processes were confirmed by Schynowski and Schwack(1996) on the enzymatically isolated fruit cuticle of tomato, paprika, apple, andgrape. In the early stage of photolysis, the unstable nitroso derivative of (135)was dominant, but the 2-hydroxyazo derivative finally gradually accumulated.The oxon derivative and 4-nitrophenol were minor products. Dissipation ratesof (135) increased with iodine number of the fruit cuticle, showing that theolefinic portion of cuticles plays an important role in the reaction. In contrast,oxidation to give sulfoxide and sulfone proceeded for fenthion (143) (Leuch and

50 T. Katagi

Fig.

18.

Succ

essi

veph

otor

educ

tion

ofpa

rath

ion

(135

)fo

llow

edby

dim

eriz

atio

n.


Bowman 1968; Minelli et al. 1996). In the thin film of fruit wax from orange,nectarine, and olive, (143) gave the sulfoxide under sunlight with a trace amountof the sulfone (Cabras et al. 1997b; Pirisi et al. 2001). With an increase of waxthickness, dissipation rates slightly increased for orange and nectarine, whereasthe thickest olive wax gave the slowest degradation. These results suggest thatthe component rather than the amount of wax film is one of the important factorscontrolling the photodegradation. Fenitrothion (138) mainly underwent photoox-idation at the aryl methyl group and the P=S moiety in methanol, hexane, andacetone (Ohkawa et al. 1974b; Greenhalgh and Marshall 1976). Thiono-thiolorearrangement (see Fig. 2, reaction 9a) and denitration were minor pathways.The difference in reaction profiles between (135) and (138) most likely origi-nates from the adjacent orientation of nitro and methyl groups in (138) that areknown to take an aci-nitro structure via photoexcitation (Katagi 1989). Thehomolytic cleavage of a C-I or C-Cl bond together with formation of the oxonand cleavage of a P-Oaryl or P-S bond was reported for iodofenphos (141)(Walia et al. 1989b), chlorpyrifos (145) (Walia et al. 1988), and phosalone (170)(Walia et al. 1989a). The cis/trans isomerization could be detected for tetrach-lovinphos (154) in hexane by exposure to UV light (Dureja et al. 1987b). Isofen-phos (175) having a different coordination at phosphorus similarly underwentP=S oxidation to the oxon by UV irradiation in hexane (Dureja et al. 1989).

Pyrethroids Regarding the photolabile chrysanthemic acid moiety, Ruzo andCasida (1980) examined the excited states involved by using methyl esters ofdichloro- and dibromo-vinyl derivatives. The main reactions in methanol werecis/trans isomerization via homolytic cleavage of C1−C3 bond of the cyclopro-pane ring to give a biradical followed by recombination together with the reduc-tive dehalogenation in the vinyl moiety. The isomerization is considered to arisefrom carbonyl excitation to the excited triplet state, as explained by molecularorbital calculations (Katagi et al. 1988). By energy transfer experiments usingvarious sensitizers, the triplet state energy for these chrysanthemates was esti-mated to be �60 kcal mol−1. Insignificant reduction of debromination in thepresence of triplet quenchers (ET = 50–53 kcal mol−1) showed no involvementof the triplet state in this process. They also examined the effect of the alcoholmoiety on photochemistry in benzene at 300 nm under sunlight by using severalpyrethroids possessing a 3-phenoxybenzyl, 3-phenylbenzyl, or 3-benzoylbenzylgroup. Intramolecular energy transfer causing enhanced cis/trans isomerizationwas likely to be involved (Ruzo and Casida 1982). Photoinduced cis/trans iso-merization via triplet excited state was observed for permethrin (17) in organicsolvents, finally giving the cis/trans ratio of �30/70 (Holmstead et al. 1978a).This type of pyrethroid usually exhibits weak UV absorption around 275 nm,essentially in n-π* character, resulting from the combined transition of the car-bonyl system and the lower energy band of the aromatic rings. The ester cleavagewas also the major process forming 3-phenoxybenzyl alcohol and the dichlor-ovinyl chrysanthemic acid. In addition to the efficient cis/trans isomerization,cypermethrin (19) in alcohols or aqueous acetonitrile underwent photoinduced

52 T. Katagi

decarboxylation (Ruzo 1983). The cis-isomer in an argon atmosphere simplygave the corresponding acid and benzyl cyanide while the presence of O2 signifi-cantly gave the ketolactone derivative (50%–60%; in the case of the trans-isomer, the caronic acid instead (Fig. 19). Because Rose Bengal in methanolcould not sensitize this oxidative reaction, O3 was likely to participate insteadof 1O2. The profiles of isomerization of deltamethrin (22) was examined in hex-ane by Maguire (1990), and detailed analysis of the photoproducts in organicsolvents was reported by Ruzo et al. (1977). The higher photoreactivity in meth-anol than (17) and (19) was considered to stem from more efficient intersystemcrossing by the heavy atom effect of bromine. Photoinduced homolytic cleavageof the ester linkage was found to occur at either the C(=O)−O or O−C(CN)bond. Epimerization at the benzyl carbon occurred in alcohols as a dark reactionvia proton exchange with a solvent molecule. Tralomethrin (25) and tralocythrin(26) in organic solvents showed similar photodegradation profiles to those onglass (Ruzo and Casida 1981). Z-cis-Cyhalothrin (21) underwent both E/Z andcis/trans isomerizations in hexane (Ruzo et al. 1987). The decarboxylated deriv-ative and the corresponding acid and alcohol moieties were the primary productsdetected in addition to hexadienes derived from opening of the cyclopropyl ring.In the case of allethrin (10), di-π-methane rearrangement via triplet state in thealcohol moiety (Bullivant and Pattenden 1973, 1976) and epoxidation and ω-oxidation in the acid moiety (Ruzo et al. 1980) proceeded more favorably thanthe usual ester cleavage.

Photochemistry of fenvalerate (27) is characterized by a higher efficiency ofdecarboxylation (Holmstead et al. 1978b). Mikami et al. (1985a) applied thespin-trap method in ESR and demonstrated involvement of the two radical spe-cies originating from acid and alcohol moieties of (27). For photodegradationin hexane, no energy transfer from isobutyrophenone and quenching by 1,3-cyclohexadiene showed involvement of the long-lived excited singlet state. Al-most identical photodegradation profiles have been reported for flucythrinate(29) in methanol or hexane with maximum degradation at 271 nm, indicatingthe involvement of n-π* excitation (Chattopadhyaya and Dureja 1991). Etofen-prox (32) underwent either photooxidation at the benzyl carbon or photoinducedhomolytic cleavage of the central ether linkage followed by radical recombina-tion to give the derivative with loss of CH2O from (32) (Class et al. 1989; Tsaoand Eto 1990b).

Carbamates The main photodegradation products of xylylcarb (63) and tri-methacarb (64) were phenols via cleavage of the O−C(=O) bond in ethanoland cyclohexane (Addison et al. 1974; Kumar et al. 1974). In the case of (63),the photo-Fries reaction proceeded only in ethanol under irradiation at >265 nmtogether with a trace cleavage at the C(aryl)-O bond leading to formation ofxylene. For propoxur (65), photoinduced cleavage of the C(aryl)-O bond oc-curred in 2-propanol, cyclohexane, and cyclohexene without photo-Fries re-arrangement. Contribution from the O−C(=O) bond cleavage was less than 1%.The main product of ethiofencarb (69) in cyclohexane and 2-propanol was the


Fig.

19.

Phot

odeg

rada

tion

ofcy

perm

ethr

in(1

9).

54 T. Katagi

corresponding sulfoxide with a trace amount of the sulfone (in 2-propanol) (Kopfand Schwack 1995). A unique reaction, but as a minor pathway, was oxidationof the benzyl carbon followed by nucleophilic substitution of the thionyl moietyby the carbamate nitrogen to form 3,4-dihydro-3-methyl-1,3-benzoxazine-2,4-dione. Although the simple photoinduced cleavage of the O−C(=O) bond wasobserved for aminocarb (66) in organic solvents (Addison et al. 1974; Kumaret al. 1974), oxidative N-demthylation via the N-CHO intermediate proceededon glass. However, this oxidation product disappeared in the presence of waxfrom nectarine fruits, showing that some wax components may act as scavengersof radicals (Pirisi et al. 2001). Similar photoreactions were detected for pirimi-carb (78) at >280 nm (Schwack and Kopf 1993). In cyclohexane, the intermedi-ate N-CHO derivative of (78) underwent either decarbonylation to the N-de-methylated derivative or oxidation of the aryl methyl group at the 6-position.Stepwise oxidation at the two aryl methyl groups at 5- and 6-positions gave theunique 5,7-dihydro-5-oxo-furo[3,4-d]pyrimidinyl ring in cyclohexane. Nectarine(N) and orange (Or) waxes were found to retard the photodegradation of (78)while the mandarin orange (M) wax accelerated the reaction (Pirisi et al. 1998).The rate of photolysis could not be correlated with UV absorbance of waxes orto their amounts, and thus it was considered dependent on the nature of wax.Because OH� would be the promotor of formylation and N-demethylation,waxes from N and Or should play the role of radical scavengers. In contrast,the component of M wax was considered to act as a sensitizer. Similar to fen-thion (143), the S-methyl sulfur was stepwise oxidized to the correspondingsulfoxide and sulfone in the thin wax film from nectarine (Pirisi et al. 2001).These results indicate that wax chemistry is very important in understanding thephotolytic behavior of pesticides after foliar application.

Dicarboximides Direct photolysis is likely to proceed for this class of fungi-cides having a weak shoulder of UV absorption at >290 nm due to n-π* transi-tions. The most probable reaction is hydrogen abstraction intramolecularly (Nor-rish type II) or from a solvent molecule by the excited carbonyl oxygen. Theformer case is known for N-phthaloylvaline methyl ester (Griesbeck and Gorner1999) but not for dicarboximide fungicides. The latter reaction has been reportedfor photolysis of folpet (107) in cyclohexene (Schwack 1990). The main reac-tion was the allylic addition of cyclohexene to one of the carbonyl groups toform the corresponding carbinol with an oxetane formation via the Paterno–Buchi reaction as a minor pathway. As a unique photoreaction, the (4π + 2π)-1,4-cycloadition at the phenyl moiety to form the benzazepindione derivativewas detected. These reactions with the olefinic carbons indicate photoreactivityin plant cuticles when (107) is foliarly applied. However, captan (106) exhibiteda different photoreactivity, that is, homolytic cleavage of a C-Cl bond followedby release of the SCHCl2 group to tetrahydrophthalimide (Schwack and Floßer-Muller 1990). Procymidone (108), iprodione (109), and vinclozolin (110) com-monly underwent photoinduced cleavage of a C-Cl bond. Successive dechlorina-tion of (109) proceeded in 2-propanol (Schwack et al. 1995a). The addition of


a solvent molecule was predominant in cyclohexene whereas mono-dechlorina-tion was the major change in cyclohexane. Procymidone (108) exhibited almostthe same photolytic profiles as (109) (Schwack et al. 1995b). In (110), solventaddition mainly occurred at the vinyl side chain and successive dechlorinationwas observed (Schwack et al. 1995c). This evidence from photodegradation inorganic solvents suggests the possible photoaddition of this class of fungicidesto wax components of plant cuticles.

Azoles Da Silva et al. (2001) revealed through flash photolysis of triadimefon(188) in cyclohexane, together with analysis of emission spectra, that the firstexcited state is n-π* localized at the carbonyl group via fast conversion from π-π* state at the 4-chlorophenoxy moiety and detected a 4-chlorophenoxy radicalat 25 nsec after a laser pulse. Product analysis showed involvement of threemain photoreactions (Nag and Dureja 1997). First was cleavage of the PhO-Cbond to give 4-chlorophenol and the corresponding triazole derivative. Eithercleavage of CH−C(=O) or C-triazole bond was also observed. The third wasphotoreduction of the carbonyl group to form triadimenol (189). Similar profilesthrough photolysis in methanol were reported by Clark et al. (1978). Triadim-enol (189) having a π-π* character in the first excited state also underwentdechlorination and cleavage of CH-C(OH) or C-triazole bond (Clark and Wat-kins 1986). Although not detected in solution photolysis of (188), the diazirinderivative via release of the N-CH moiety from 1,2,4-triazolyl ring was formedfrom propiconazole (191) in hexane by UV irradiation (Dureja et al. 1987a).Hexaconazole (192), fluotrimazole (195), and penconazole (193), not having thecarbonyl group are considered to undergo photolysis via π-π* transition at thearomatic moieties. Photoliability of (192) was demonstrated in hexane and ace-tonitrile but without detailed information on degradation (Santoro et al. 2000).Photoinduced cleavage of the C-triazole bond followed by addition of methanolmolecule was reported for (195) (Clark et al. 1983). Penconazole (193) under-went photocyclization in 2-propanol or cyclohexane between o-position of the4-chlorophenyl ring and 5-position of the 1,2,4-triazolyl ring to form the 5H,6H-(1,2,4-triazole)-[5,1a]-isoquinoline derivative (Schwack and Hartmann 1994).Similar photocyclization of diniconazole-M (190) was reported by Sharma andChibber (1997). Katagi (2002a) examined this photoprocess for the racemicmixtures of (190) by NMR and molecular orbital calculations and demonstratedthat the reaction proceeds via excited singlet state in a similar manner as re-ported for cis-stilbene.

Ureas In addition to the usual photoinduced cleavage of an N−C(=O) bondvia carbonyl excitation to form the corresponding aniline, oxidative N-demethyl-ation successively proceeded for isoproturon (56) in organic solvents with re-lease of formaldehyde (Kulshrestha and Mukerjee 1986). UV irradiation ofdiflubenzuron (59) in methanol caused the cleavage of the central C(=O)−NHC(=O) bond, mainly leading to formation of N-phenyl methylcarbamate and2,6-difluorobenzamide (Ruzo et al. 1974). Chlorsulfuron (96) and metsulfuron-

56 T. Katagi

methyl (98), which have insignificant UV absorption at >290 nm, are consideredunlikely to undergo direct photolysis in the environment (Yang et al. 1999). Incontrast, chlorimuron-ethyl (102), with UV absorption at 275 nm, was rapidlyphotodegraded in methanol and hexane via cleavage of either the N-C ureic orS-N bond (Choudhury and Dureja 1997b). Contraction of the sulfonylurea bridgewas considered to follow a concerted elimination of SO2 with formation of inter-mediate radicals being recombined (Fig. 20). In contrast, photolysis in benzenedid not produce this derivative (Choudhury and Dureja 1997c), showing the im-portance of solvent polarity. Bhattacharjee and Dureja (1999) reported UV photol-ysis of tribenuron-methyl (99) in organic solvents proceeding via bond cleavagearound the sulfonylurea bridge including its contraction, similar to (102).

Miscellaneous Sunlight photodegradation of pendimethalin (238) was studiedin several organic solvents (Halder et al. 1989). Dureja and Walia (1989) inves-tigated its sunlight photolysis in methanol and found 2,6-dinitro- and 2-amino-6-nitro-3,4-xylidene as principal products via N-dealkylation and photoreduc-tion, but no benzimidazole derivatives formed in aqueous photolysis could bedetected. The effect of unsaturated fatty acids and surfactants coexisting in for-mulation on photolysis of chinomethionat (228) was studied on glass (Nutaharaand Murai 1984). Oleic acid is one of the major fatty acids in leaf extracts ofeggplant and cucumber and accelerated photolysis of (228) as with its self-decomposition. Similar photoacceleration was observed by addition of the vari-ous unsaturated fatty acids or polyoxylene sorbitan oleates (Tween 60, 80, 85).Because oleic acid by itself was stable under irradiation, some photoreactionbetween (228) and the C=C bond of oleic acid similar to the responses of (130),(134), and (211) might account for these results. Draper and Casida (1985)reported the ene-reaction of the nitroso derivative photochemically formed inthin films from nitrofen (216) and CNP (217). The nitroso derivatives reactedwith the C=C bond of various chemicals including methyl oleate to form thecorresponding nitroxides via alkenylarylhydroxyamines being detected by ESR.The weak ESR signal was observed for beet leaves when treated with (216) inan extremely high level, showing the ambiguity of this reaction occurring in theenvironment. The ESR signal was detected for irradiated methyl oleate filmcontaining (135) but not for (138), which coincides with dominant formation ofnitroso and its related derivatives from (135) but major detection of the oxidizedderivatives of (138) instead. As a model cuticle instead of organic solvents orthin film on glass, Caboni et al. (2002) utilized cellulose membrane coated withepicuticular waxes from olives to evaluate the extent of evaporation, codistilla-tion, and thermodegradation of azadirachtin. In the absence of waxes, codistilla-tion with water proceeded but dissipation of azadirachtin from wax-treated cel-lulose was not detected.

VIII. Photodegradation of Pesticides on Soil and Clay Surfaces

The photodegradation profiles of pesticides in/on soil and clay, based on the re-sults of the literature survey, are summarized in Table 10 (see table on page 105).


Fig.

20.

Phot

oind

uced

rear

rang

emen

t(b

ridg

eco

ntra

ctio

n)of

chlo

rim

uron

-eth

yl(1

02).

58 T. Katagi

Organochlorines Dichlobenil (116) and chlorothalonil (117) were reported toundergo photoinduced substitution of Cl with OH or hydration of cyano groupsin aqueous phase although they were rather resistant to photolysis in or onsoils (EPA OPPTS 1998c, 1999c). In contrast, some photodegradation has beenobserved for dicamba (118) and chloramben (119). Misra et al. (1997) examinedphotodegradation of 14C-(119) by varying conditions of loam soil and found that3,5-dihydroxy- and 3-chloro-6-hydroxy-benzoic acids are detected in the intactsoil at 75% field moisture while only the deaminated derivative is formed onair-dried soil. Moisture content might affect the extent of reactive speciesformed such as OH�, resulting in different product profiles. When (118) coatedon synthetic clay laponite was irradiated with UV light, decarboxylation pro-ceeded in addition to dechlorination and hydroxylation (Aguer et al. 2000). Thephotoinduced charge transfer from (118) to clay via interaction of the carbonylgroup with the clay surface was proposed as the reaction mechanism, and resid-ual water molecules on clay were considered to play a role in inducing dechlori-nation and hydroxylation by polarizing either the O-CH3 or C-Cl bond. Penta-chlorophenol (121) rapidly dissipated on soil thin layer by UV irradiation toform octachlorodibenzo-p-dioxin (Liu et al. 2002). Because detailed examina-tion of photoproducts from (121) as solution or solid has revealed that the photo-induced dechlorination primarily results in formation of free radicals whose suc-cessive reactions give dioxins (Piccinini et al. 1998), a similar radical processewould also operate on irradiated soil surfaces. This mechanism may be ac-counted for with less formation of dioxins by addition of fulvic acids to soilsthat can act as a scavenger of radicals. When 2,3,7,8-TCDD (129) applied tosoils was exposed to sunlight, the degradation, possibly via dechlorination, ap-peared only in the first 5 days but the coexistence of 1%–5% hexadecane main-tained constant photodegradation up to 15 d (Kieatiwong et al. 1990). Theseresults coincided with possible photodegradation near the soil surface and im-plied that hexadecane might act as a hydrocarbon film allowing solubilizationand migration of (129) from the deeper region of soil to the irradiated surface.Detection of a trace amount of photodieldrin (124) by soil application of 14C-aldrin (122) showed a possible contribution of photodegradation on the soilsurface (Klein et al. 1973). Involvement of photolysis in field dissipation oforganochlorine pesticides including (122) and (123) was demonstrated by moni-toring studies in 99 fields (Suzuki and Yamato 1974). DDT (130) in/on soil wasphotodegraded under sunlight to DDE (131) via dechlorination (Zayed et al.1994). Less photoreactivity of dicofol (133) was briefly reported on soil (EPAOPPTS 1998d).

Organophosphorus Esters Hautala (1978) reported that the apparent quantumyield of parathion (135) was reduced on soils compared to a solution phase andthat no factors except the amount of soil appeared to correlate with the photoly-sis rate, indicating the importance of the screening effect by soil. As a mainproduct of parathion methyl (136), 4-nitrophenol was reported in an outdoorsunlight photodegradation study (EPA OPPTS 1999e). UV irradiation alone was


ineffective for conversion of (135) to the oxon on soil dusts and clays, but theexistence of O3 at 50–300 ppb increased its rate by a factor of 2–3 (Spencer etal. 1980). Greater formation of the oxon on soil dusts having less organic matterclearly demonstrated that the catalytic activity of clay played a large role inphotooxidation. These reaction profiles have been recently confirmed on soilfor 14C-(136) by Kromer et al. (1999). Cyanophos (137) and fenitrothion (138)were photodegraded on soil thin layers mainly to 4-cyano- or 3-methyl-4-nitro-phenol via cleavage of the P-O aryl bond, respectively (Mikami et al. 1976,1985b). Either the corresponding oxon or O-demethylated derivative was a mi-nor photoproduct from (137) and only the former product was identified for(138). Fenthion (143) was photodegraded on soil thin layers to 40%–80% after4 days, and insignificant degradation was observed on glass (Gohre and Miller1986). No information on degradates was available, but product analysis ondisulfoton (163) and methiocarb (68) suggested formation of the correspondingsulfoxide, most likely via reaction with 1O2 produced on soil surfaces by irradia-tion. The fastest photodegradation in the soil with the least organic matter con-tent might imply the involvement of clay surface.

Degradation of bromophos (140) and iodofenphos (141) on soil was slightlyenhanced by sunlight irradiation via cleavage of the P-O aryl bonds (Allmaierand Schmid 1985; Allmaier et al. 1984). Walia et al. (1989b) reported oxidationof the P=S moiety to oxon and stepwise dehalogenation for (141). 14C-Tol-clofos-methyl (142) was photodegraded on soil via either photoinduced oxida-tion of the P=S moiety to the oxon followed by O-demethylation or cleavageof the P-O aryl bond to give 2,6-dichloro-4-methylphenol (Mikami et al. 1984b).More of the oxon was detected for soils with lesser organic matter content,showing contribution of clay surfaces in oxidation as similarily reported for(135) and (136). From this aspect, Katagi (1990) investigated the photoinducedoxidation of (142) in/on clay surfaces. The UV reflectance spectrum of (142)on kaolinite film exhibited almost the same pattern as that in 10% acetonitrilewith no reflectance above 300 nm. UV light exposure at 320 nm resulted inrapid degradation of (142) especially for the kaolinite surface where significantamounts of oxon were formed, clearly demonstrating involvement of indirectphotolysis. Less formation of the oxon was observed when clay was air-driedor the study was conducted under nitrogen. MS analysis of the oxon formed inkaolinite treated with H2

18O showed about 40% incorporation of 18O into theP=O moiety. Formation of H2O2 was confirmed spectrophotometrically, but thelack of detection of trans-diacetylacetylene from 2,5-dimethylfuran by HPLCanalysis showed the absence of 1O2 on the irradiated clays. Based on these obser-vations, formation of the oxon could be well explained by reaction with OH�that was produced from the successive reaction with residual water molecules,with the superoxide anion radical formed probably via photoinduced electrontransfer from clay to O2.

Photodegradation of chlorpyrifos (145) on soil at 254 nm gave the oxon and3,5,6-trichloropyridinol as main degradates with lesser amounts of dechlorinatedderivatives (Walia et al. 1988). Burkhard and Guth (1979) have shown that

60 T. Katagi

diazinon (144) undergoes photoinduced cleavage of the P-O aryl bond on soil.Similar results have been reported for sunlight photolysis on sandy loam soil(EPA OPPTS 2000). Because the aqueous photolysis was of insignificant contri-bution in its dissipation, some kind of indirect photolysis would operate onthe soil surface. Sunlight photodegradation of quinalphos (148) on soil gavediquinoxalin-2-thiol, diquinoxalin-2-yl sulfide, and disulfide in addition to quin-oxalin-2-ol formed via the usual photoinduced cleavage of the P-O aryl bondwithout formation of the oxon (Dureja et al. 1988). The photoinduced thiono-thiolo rearrangement of (148) followed by cleavage of the P-S aryl bond wasmost probable, as reported for photodegradation on clays (Banerjee and Dureja1999). The photolytic profiles of 14C-dioxabenzofos (183) on soil were found tobe common to other phosphorothioates (Mikami et al. 1977b). Photodegradationof profenofos (160) on soil gave 4-bromo-2-chlorophenol and O-(4-bromo-2-chlorophenyl) O-ethyl O-hydrogen phosphate (Burkhard and Guth 1979). Thelatter compound was most likely to be formed by photoinduced hydrolysis, incontrast to the O-dealkylation of other phosphorothioates.

Qualitatively, the extent of photodegradation of 14C-azinphos-methyl (169)on soil was found to be reduced with an increase of soil depth and organicmatter (Liang and Lichtenstein 1976). Phosalone (170) mainly underwent cleav-age of the SCH2-N bond and was either dechlorinated or oxon derivatives weredetected in trace amounts (Walia et al. 1989a). A similar SCH2-N bond cleavagewas reported for methidathion (171) at >290 nm but at trace amounts (Burkhardand Guth 1979). On exposure to sunlight, 14C-phenthoate (168) was photode-graded via oxidation, cleavage of P-S or S-C bond, and hydrolysis of carboxylicester with formation of the α-carboxybenzyl thiol (Mikami et al. 1977b). O,O,S-Trialkyl derivatives not possessing a chromophore are considered to be degradedby indirect mechanism if photolysis occurs. Phorate (162) was rapidly degradedin the field to give its sulfoxide and sulfone (Lichtenstein et al. 1973). Disulfo-ton (163) showed rapid photodegradation on soil with formation of the corre-sponding sulfoxide (Gohre and Miller 1986). Based on no effect by sterilization,reactions of (162) and (163) with 1O2 being formed by sunlight irradiation onsoil were considered most likely. Formation of the corresponding sulfone wasreported for (163) under sunlight (EPA OPPTS 1999d). The photoinduced oxi-dation of the P=S moiety to the oxon was observed only for ethion (184) (EPAOPPTS 1995c).

Bensulide (164) exhibited simple photoinduced oxidation of the P=S moietyby UV irradiation (EPA OPPTS 1999a). Monocrotophos (156) and dicrotophos(157) are unlikely to undergo photochemical reactions on soil due to lack ofchromophores in their molecules (Lee et al. 1989, 1990). Tetrachlovinphos(154) was expected to undergo E/Z isomerization, but the main reactions wereO-demthylation and cleavage of the P-O vinyl linkage (Beynon and Wright1969; Dureja et al. 1987b). Isofenphos (175) underwent photoinduced P=S oxi-dation to the oxon with cleavage of the P-O aryl bond, but no effect on the P-N linkage was observed (Dureja et al. 1989). The same degradation profiles asaerobic soil metabolism but with a much faster rate were reported on soil (EPA


OPPTS 1998f). Allmaier et al. (1984) reported via soil photolysis of ditalimfos(178) that the main product was O,O-diethyl phosphoramidothioate, probablyby stepwise hydrolysis of the imide ring, but photoinduced cleavage of the P-Nbond as observed in aqueous photolysis was not detected. The P-C bond ofcyanofenphos (180) remained unaffected by irradiation (Mikami et al. 1976).Although examples are limited, either the P-N or P-C bond is considered to beresistant to photolysis on soil.

Phenoxyalkanoates and Esters The apparent quantum yield of methyl ester of2,4-D (1) on soil was found to be 30 times lower than that in aqueous solution,which might be accounted for by screening and/or quenching effects of soil(Hautala 1978). The coarser the soil, the faster the sunlight photodegradation ofmecoprop (4) and its 2,4-dichlorophenyl derivative, which suggests that thedeeper penetration of light into soil facilitated their degradation (Romero et al.1998). Their declines followed the Hoerl function (y = aebxxc) rather than theusual first-order kinetics, and increase in moisture content enhanced the photo-degradation. Therefore, the transport of these pesticides to the photic zone alongwith water movement may control their photodegradation profiles. Norris et al.(1987) reported that triclopyr (7) was degraded in pastures to give 2-methoxy-3,5,6-trichloropyridine and 3,5,6-trichloropyridin-2-ol via successive decarbox-ylation and O-demethylation.

Pyrethroids Photoinduced isomerization was a minor pathway for soil photol-ysis of cis- or trans-permethrin (17) (Holmstead et al. 1978a). Sunlight irradia-tion had no effect on ester cleavage for both isomers, and either dechlorinationor cleavage of the cyclopropyl ring to give dimethylacrylate derivative was alsoa minor pathway. Photoinduced isomerization of trans- and cis-cypermethrin(19) was also found insignificant on soil (Takahashi et al. 1985a). The mainreaction was stepwise hydration of the α-cyano group to CONH2 and COOHand was clearly accelerated by sunlight irradiation, although this hydration wasnot affected by irradiation in the other study (EPA FIFRA 1999). Photodegrada-tion of deltamethrin (22) was briefly reported with slight contribution of photol-ysis on soil, and the main degradation product was the corresponding dibromo-vinyl chrysanthemic acid (EPA FIFRA 1999). Sunlight photodegradation wasfound to be also of less importance for Z-cis-cyhalothrin (21) on soil (Ruzo etal. 1987). In another 14C study using artificial light, formation of the α-CONH2

derivative was reported (EPA FIFRA 1999). In the case of cis-tefluthrin (18),cis/trans isomerization was reported on soil by UV irradiation although its pho-todegradation was rather slow (EPA FIFRA 1999). Rapid sunlight photodeg-radation was reported for 14C-cyfluthrin (20) with formation of 4-fluoro-3-phenoxybenzaldehyde via ester hydrolysis and release of cyanide ion from thecorresponding cyanohydrin (EPA FIFRA 1999). Similar to (19), hydration ofthe α-cyano group to CONH2 predominantly occurred for 14C-fenpropathrin (24)with more formation under sunlight on soil (Takahashi et al. 1985b).

62 T. Katagi

To clarify the reaction mechanism of photoinduced hydration common tothese pyrethroids, Katagi (1993b) examined effects of moisture content and clayon photolysis of 14C-(24) using UV light at >290 nm. The degradation rate of(24) was found to be highly dependent on soil moisture, and UV irradiationonly slightly enhanced the hydration. The amount of α-CONH2 derivative sig-nificantly increased with decreasing soil moisture, and this reaction was en-hanced when clay was used. The shift of C=O vibration in IR spectra to ahigher wavenumber in soil and clay as compared with that in KBr implied someinteraction of the cyano group but not the carbonyl oxygen with these surfaces.Because clay surface is known to exhibit an extremely high acidity when dried,the observed hydration of the α-cyano group was considered most likely to beacid catalyzed on clay surfaces. The inconsistency observed for the amount ofα-CONH2 derivative of (19) between laboratory and outdoor studies can beelucidated by the difference of soil moisture; less moisture in soil thin layerskept outdoors would enhance the hydration.

Fenvalerate (27) dominantly underwent hydration of the α-cyano group onsoil with a trace formation of decarboxylated derivative (Mikami et al. 1980).Katagi (1991) reported hydration of the α-cyano group and O-dephenylation of14C-esfenvalerate (28) on soil and clays, which was enhanced on exposure toUV light at >300 nm. It was demonstrated by MS analysis that about half of18O was incorporated into the O-dephenylated derivative when photolysis wasconducted on clay prepared from H2

18O suspension. Because Fenton’s reagentwas found to give the O-dephenylated derivative of (28), OH� photochemicallyproduced on clay surfaces was most likely to directly react with (28). Further-more, kaolinite clay was found to catalyze hydration of (28) in the presence ofH2O2, acting as a nucleophile against the cyano carbon to finally give the α-CONH2 derivative. Flucythrinate (29) and fluvalinate (30) similarly underwenthydration of the α-cyano group and cleavage of the ester (Quinstad and Staiger1984; Dureja and Chattopadhyay 1995). Most of these pyrethroids have the 3-phenoxybenzyl moiety, which is usually released through photodegradation asPBacid (243). The significant red shift in reflectance spectrum of (243) on ka-olinite clay showed possible interaction with the surface. The insignificant spec-tral overlap the artificial light (>300 nm) implied indirect photolysis; the mainphotodegradate on soil and clay was 3-hydroxybenzoic acid (3-HB). The pho-tonucleophilic reaction by OH− was unlikely because there was no reaction withmore nucleophilic cyanide ion in aqueous photolysis, and 18O incorporation into3-HB was demonstrated by MS analysis when aqueous photolysis was carriedout in 50% H2

18O. Incidentally, Fenton’s reagent gave 3-HB as a main degradate.These results indicated that OH� photochemically produced on these surfacesattacked the 3-position of (243) and this ipso substitution resulted in formationof 3-HB.

Carbamates Contribution of photolysis in dissipation of propoxur (65) on soilwas considered less than that from binding to soil and volatilization (EPA OP-PTS 1997b). Methiocarb (68) has a 4-methylthio moiety reactive to 1O2, and the


main photodegradation product was the sulfoxide on soils under sunlight (Gohreand Miller 1986). UV irradiation of carbaryl (71) at >290 nm on soil showedless photoreactivity than aqueous photolysis (Hautala 1978). The disappearanceof fluorescence of (71) on soil implied the efficient quenching by soil constit-uents, which at least in part accounted for reduction of photolysis. The photoly-sis profiles of carbofuran (72) were briefly examined on field plots as a maindegradate of carbosulfan (88) (Nigg et al. 1984). After an outdoor application,(88) quickly dissipated on soil to give (72), which was rapidly degraded to givea trace amount of the 3-keto derivative. Benfuracarb (89) was reported to besimilarly converted to (72) via cleavage of the N(CH3)-S bond on soil by UVirradiation (Dureja et al. 1990). When 14C-benthiocarb (86) was exposed to sun-light on soil taken from a rice-growing area, the photoinduced S-oxidation togive the sulfoxide and sulfone was observed similarly as (68) possibly via reac-tion with 1O2 (Cheng and Hwang 1996). A similar photooxidation of sulfur bysunlight was reported for butyrate (87) on soil (EPA OPPTS 1993). Molinate(90) is considered to undergo S-oxidation on soil, but faster degradation undersunlight was reported without any information on degradation products (Kons-tantinou et al. 2001). The usual cleavage of carbamate linkage proceeded forasulam (82) to give sulfanilamide as a main photodegradate on soil (EPA OP-PTS 1995a). Desmedipham (83) and phenmedipham (84) have two carbamatelinkages in molecules but the C(=O)−O aryl bond was found to be primarilycleaved. The main pathway of 14C-(83) on soil was formation of ethyl (3-hydrox-yphenyl)carbamate, and degradates via photo-Fries rearrangement in aqueousphotolysis could not be detected (EPA OPPTS 1996b). Maneb (94) was quicklydegraded to ETU (95) on soil (Rhodes 1977). After application of 14C-(94) and14C-(95) to the ground, the recovered radioactivity from soil rapidly decreasedto form ethyleneurea via S-oxidation of (95). Thiophanate-methyl (92) showeda similar S-oxidation at one of two C=S moieties on soil exposed to sunlighttogether with formation of MBC (93) (EPA OPPTS 2001). Almost quantitaiveformation of (93) was reported for benomyl (81) on soil with 2-aminobenzimid-azole as a minor degradate (EPA OPPTS 2001).

Amides, Anilides, and Dicarboximides Soil organic matter was found to accel-erate photolysis of propachlor (33) by sunlight irradiation (Konstantinou et al.2001). For alachlor (34), the rate of photodegradation was enhanced by low soilorganic matter, low pH, or high water content (Fang 1977; Chesters et al. 1989).Alachlor (34) underwent cleavage of either the N−CH2 or N−C(=O) bond fol-lowed by further degradation to 2,6-diethylaniline and reductive dechlorination(Fig. 21). As a unique reaction, the intramolecular cyclization occurred betweennitrogen and o-ethyl group to give N-chloroacetyl-7-ethylindoline. Somich et al.(1988) examined the effect of photolytic ozonation on dissipation of 14C-(34) insoil and found that O3 caused release of more carbon dioxide from the irradiatedsoil. Photolysis of metolachlor (35) on soil by artificial sunlight gave N-chloro-acetyl-N-(hydroxyprop-1-en-2-yl)-2-ethyl-6-methylaniline as a main degradate(see Fig. 21) (Chesters et al. 1989). This product was considered to be formed

64 T. Katagi

Fig.

21.

Com

para

tive

phot

odeg

rada

tion

path

way

sof

alac

hlor

(34)

and

met

olac

hlor

(35)

.


via photoinduced cleavage of the O-CH3 bond. Metalaxyl (37) was slowly pho-todegraded on soil, but its degradation was found to be also controlled by eithermicrobial degradation or abiotic factors other than light (Sukul and Spiteller2001). The slower rate of degradation was observed for soil having a larger claycontent, and light screening by adsorption of (37) into the interlayer of claymight reduce the effect of irradiation. On air-dried soil, (37) was reported toundergo cleavage of either the CH2-OCH3 or N−C(=O) bond (Saha and Sukul1997). Under simulated sunlight, carboxin (42) was photodegraded to give thecorresponding sulfoxide, and increased moisture content accelerated photolysis(Murthy et al. 1998). Because insignificant photodegradation of oxycarboxin(43) was observed under the same conditions, the main degradation pathway of(42) was most likely to be photoinduced S-oxidation. Further photodegradationof the sulfoxide was examined in soil suspension, and oxanilic and malonicacids were additionally identified (Hustert et al. 1999).

Effects of soil properties such as moisture content and soil depth have beeninvestigated in conjunction with photolytic profiles of 14C-nicloamide (40)(Frank et al. 2002; Graebing et al. 2002). The reactive site of (40) was the 4-nitro group, which was either reduced to an amino group or substituted withOH, and these products were finally degraded to 3-chloro-6-hydroxybenzoicacid. NO−

3 added as a fertilizer, iron oxide, or humic acid was found to causeinsignificant effects on photodegradation of (40) in moistened soil, but reduceddegradation was observed in air-dried soil. Although the photodegradation path-way was not available, the importance of pesticide transport to soil surface hasbeen extensively studied for napropamide (47) (Miller and Donaldson 1994;Donaldson and Miller 1996). The main metabolic pathway of florasulam (48)in soil was O-demethylation, whose formation was accelerated by sunlight expo-sure, and this product was further photodegraded via stepwise opening of thetriazolopyrimidine ring (Krieger et al. 2000). Microbial degradation of 14C-(48)was considered to dominate its dissipation in soil, but one product ASTP (8-fluoro-5-methoxy[1,2,4]triazolo-[1,5c]pyrimidine-2-sulfonamide) characteristicof soil photolysis was formed via cleavage of the NH-aryl bond. Degradationof captan (106) was slightly enhanced by sunlight exposure on moist soil withmajor degradates identified as tetrahydrophthalimide and cyclohex-4-ene-2-cyano-1-carboxylic acid (EPA OPPTS 1999b). The former product was consid-ered to be formed via cleavage of the N-S bond, whereas opening of the imidering followed by reduction of the amide moiety would also proceed in soil. 14C-Iprodione (109) exhibited a slightly rapid degradation on soil with formation of3,5-dichloroaniline and 3-(3,5-dichlorophenyl)-2,4-dioxaimidazolinone (Fig. 22)(EPA OPPTS 1999b). As a unique degradate, 3-(1-methyl-ethyl)-N-(3,5-dichlo-rophenyl)-2,4-dioxo-1-imidazolidinecarboxamide was identified, and photoin-duced cleavage of the amide linkage in the ring followed by recombination ofthe carbonyl radical with the N-isopropyl nitrogen was most likely to be in-volved. The photochemistry of famoxadone (111) on soil was briefly reportedbut the characteristic reaction induced by light exposure was not clarified (Jern-berg and Lee 1999).

66 T. Katagi

Fig. 22. Photoinduced rearrangement of iprodione (109).

Ureas Jirkovsky et al. (1997) reported that diuron (53) was photodegraded onsand via N-demethylation and oxidation to the N-formyl-N-methyl derivativewith a trace formation of monuron (52). As N-demethylation of (53) was dem-onstrated not to require O2, it was considered that the photoinduced rearrange-ment of an N-methyl group to carbonyl oxygen gave the corresponding isoureaderivative, which was further hydrolyzed to the NHCH3 derivative. For the N-formyl-N-methyl derivative, the excited carbonyl group was likely to initiatehydrogen abstraction from the N-methyl group followed by reaction with O2.Photodegradation of linuron (54) on soil gave NHOCH3, NH2 derivatives, and3,4-dichloroaniline (EPA OPPTS 1995d). By comparing the results in aerobicsoil metabolism, photolysis was likely to be of minor importance for (54). Inthe case of isoproturon (56), the same photoreactions as (53) were observed butwith a slower degradation rate (Kulshrestha and Mukerjee 1986). The photoin-duced ring rearrangement was reported for 14C-thidiazuron (58) on soil thinlayer, leading to formation of 1-phenyl-3-(1,2,5-thiadiazol-3-yl)urea (Klehr etal. 1983). Information on benzoylurea pesticides is very limited, but the resultsfor photodegradation of diflubenzuron (59) on soil showed an insignificant con-tribution of photolysis (EPA OPPTS 1997a). Chlorsulfuron (96) was slowlyphotodegraded on soil via either O-demethylation or cleavage of the sulfonyl-urea linkage, but acetylbiuret was not detected (Strek 1998). Similar photodegra-dation under sunlight was reported for chlorimuron-ethyl (102) together withunique contraction of the sulfonylurea bridge (see Fig. 20) (Choudhury andDureja 1997a). Tribenuron-methyl (99) was photodegraded under sunlight viaN-demethylation with cleavage of either the S-N bond or urea moiety, but anydegradates via bridge contraction were not detected (Bhattacharjee and Dureja2002). In contrast, photodegradation of 14C-rimsulfuron (103) on soil gave twomajor degradates via bridge contraction but no acceleration of degradation by


sunlight exposure was observed (Schneiders et al. 1993). One of the degradateswas N-(pyrimidin-2-yl)-N-(pyridin-2-yl)urea derivative, which was consideredto be degraded to the second by release of the carbamoyl group. Involvementof direct photolysis on sterilized soil was confirmed for triasulfuron (100) andthifensulfuron-methyl (105) (Albanis et al. 2002).

Azoles and Triazines Triadimefon (188) underwent photoinduced cleavage ofeither O-CH or CH−C(=O) bond and reduction of the carbonyl group on soilunder sunlight with the decarbonylated derivative as a minor product (Nag andDureja 1996). Judging from its UV absorption, direct photolysis was likely toproceed and the increase of soil moisture enhanced photodegradation (Murthyet al. 1998). Propiconazole (191) was photodegraded on soil via cleavage of theC-triazole bond, liberating 1,2,4-triazole. The unique ring opening was reportedfor photodegradation of 14C-prochloraz (240) in both laboratory and field studies(Hollrigl-Rosta et al. 1999). Prochloraz (240) was gradually photodegraded onsoil to give primarily the formylurea derivative of (240) followed by deformyla-tion (Fig. 23). Atrazine (185) was found resistant to photolysis on air-driedsoils (Curran et al. 1992), although slight sunlight photodegradation of an extentproportional to the content of soil organic matter was reported (Konstantinou etal. 2001). Gong et al. (2001) showed that in coarser soil where light can pene-trate more deeply, or upon addition of humic acid, or in moistened soil wheremovement of the pesticide molecule is facilitated, an increased rate of photodeg-radation can occur.

Miscellaneous Photolysis seems to be of minor importance for dinitroanilineherbicides relative to volatilization loss and thermal degradation (Wright andWarren 1965; Parochetti and Hein 1973; Parochetti and Dec 1978). Although adetailed photodegradation pathway on soil was not available, photolysis of tri-fluralin (232) on kaolinite clay was conducted to theoretically investigate theimportance of photic depth in clay and its transport within the layer (Balmer etal. 2000). On exposure to UV light, (232) on clay was slowly decomposed withformation of two benzimidazole derivatives. Either photoinduced cyclization be-tween nitro nitrogen and the 1-position of an N-propyl group to give the benzim-idazole or N-depropylation was most likely to occur. Cyclization was precededby photoinduced reduction of the nitro group to a nitroso derivative whose ex-cited state extracted hydrogen from the C1 position of the N-alkyl group. Photo-degradation of fluchloralin (236) on soil gave three benzimidazole derivativesvia similar reactions observed for (232) (Nilles and Zabik 1974). The releaseof the chloroethyl moiety was observed with a unique formation of 5-nitro-7-trifluoromethyl-1,4-quinoxaline. In photodegradation of ethalfluralin (237), 1H-benzimidazole-3-oxide was additionally detected (EPA OPPTS 1995b). The ex-istence of this product supported a reaction mechanism where the photoexcitednitro group extracted hydrogen at the C1 position of the N-alkyl group and radi-cal recombination followed by release of hydroxide resulted in benzimidazole-N-oxide. Insignificant degradation by exposure to sunlight was observed for

68 T. Katagi

Fig.

23.

Phot

oind

uced

ring

open

ing

ofpr

ochl

oraz

(240

).


butralin (234) on soil (EPA OPPTS 1998b). Halder et al. (1989) reported thephotoinduced N-deethylation of pendimethalin (238) on sunlight-exposed soil;other reactions such as photoreduction were predominant when exposed to UVlight (Dureja and Walia 1989). In contrast to these dinitroaniline herbicides,oryzalin (235) was found to be photolabile on soil, forming many unknowns,and bound 14C via cleavage of the C-N(C3H7)2 bond, hydrolysis of sulfonamide,and formation of the benzimidazole derivative (EPA OPPTS 1994).

Amitrole (196) was moderately resistant to sunlight photolysis on soil butunderwent C-N bond cleavage to give 1,2,4-triazole (EPA OPPTS 1996a). An-other type of photoinduced deamination via cleavage of the N-N bond was re-ported for metribuzin (201) in an outdoor photolysis study on soil (EPA OPPTS1998g). Terbacil (197) underwent cleavage of the N-C(CH3)3 bond to give 5-chloro-6-methyluracil (EPA OPPTS 1998h). Bentazon (200) underwent oxida-tive opening of the thiadiazinone ring to give N-isopropyl-2-nitrosobenzamide,followed by oxidation to the corresponding nitro derivative (Nilles and Zabik1975). The primary photoprocess was considered to be hydrogen abstraction atthe NH moiety to form the radical whose center would also be located at the 5-and 7-position of the benzothiadiazinone ring (o- and p-position toward thecarbonyl moiety) via resonance. Norflurazon (214) showed moderate sunlightphotolysis on soil with N-demethylation being the dominant process (SchroederKvien and Banks 1985). Fipronil (220) exhibited a unique photoreaction to givethe desulfinyl derivative (Bobe et al. 1998b), and the sulfone derivative wasalso detected in two field dissipation studies (Bobe et al. 1998a; Fenet et al.2001). 14C-DTP (221), the herbicidal entity of pyrazolate, mainly underwentoxidative N-demethylation on paddy soils (Yamaoka et al. 1988).

IX. Photodegradation of Pesticides on Plants

Photodegradation profiles of pesticides on plant surfaces were reviewed basedon surface-wash analysis in plant metabolism studies, unless described other-wise, to distinguish the photochemical conversion from biotic processes. Theplant species and some experimental conditions are summarized in Table 11(see table on page 120) for each pesticide with its half-life.

Organochlorines Each formulation of DDT (130), aldrin (122), dieldrin (123),and endrin (126) was sprayed on apple trees in the field and the hexane rinsatesof leaves were analyzed (Harrison et al. 1967). DDT was photodegraded toDDD (132) and 4,4′-dichlorobenzophenone. Aldrin was degraded with concomi-tant formation of (123). The cage-type ketone and aldehyde derived from reac-tions at the bridged carbons were detected for (126). When (122), (123), and(126) were applied to leaves of young bean plant or glass plates under sunlight,similar photodegradation profiles were identified (Ivie and Casida 1971b; Ivieet al. 1972). In the same study using apple trees, the β-isomer of endosulfan(125) was found to be a little more persistent than the α-isomer with formationof its sulfate. After application to cotton leaves in the field, the α-isomer mainly

70 T. Katagi

underwent dechlorination at the bridge carbon with trace amounts of β-isomerand ring-opening products, whereas the β-isomer only gave the latter (Durejaand Mukerjee 1982). These results agreed with those seen with solution photoly-sis in hexane. Similar solution photochemistry was also reported for chlordane(128) applied to cabbage leaves (Parlar et al. 1978). As shown in Fig. 24, N-(α-trichloromethyl-p-methoxybenzyl)-p-methoxyaniline principally underwentphotoinduced rearrangement on lettuce and bean leaves to N-phenyl-α-hydroxy-benzylamide, which was the common photoproduct in water and on glass orsilica gel (Miller et al. 1974). Direct absorption of light caused a charge transferfrom nitrogen to the CCl3 moiety, followed by the successive release of chlorideion and recombination to the unstable three-membered intermediate, which washydrolyzed to the corresponding amide.

Organophosphorus Esters This class of pesticides undergoes various transfor-mations in plant metabolism, as reviewed by Katagi and Mikami (2000). El-Refai and Hopkins (1966) compared dissipation of parathion (135) topicallyapplied to garden beans or glass plates. The biphasic decay in contrast to thesimple first-order dissipation on glass implied penetration of (135) into cuticleand tissue. A similar biphasic foliar decay was observed in residue trials inorange groves with concomitant formation of the oxon (Popendorf and Leffing-well 1978). Formation and decay of the oxon was found to strongly correlatewith dry and stable weather, and effects of foliar dust and airborne oxidantswere suspected. Spear et al. (1978) conducted residue trials of (135) on dwarfEureka lemon trees in the presence or absence of O3 and soil dusts (<50 µm).They showed that the a photoinduced dust-catalyzed process is one of the mostimportant routes for the foliar P=S oxidation of (135). However, the presenceof soil dust on foliage might retard the decay of the oxon by its stronger adsorp-tion to dust (Adams et al. 1977). Joiner and Baetcke (1973) scrutinized thedegradates from 14C-(135) on cotton. Although the degradates were extracted byhomogenization, the S-ethyl isomer was detected with a trace amount of the S-phenyl isomer, indicating the contribution of photolysis.

Plant metabolism studies using 14C- or 32P-labeled fenitrothion (138) in rice(Miyamoto and Sato 1965), sugar beet, (Ohkawa et al. 1974b), and apples (Ho-sokawa and Miyamoto 1974) have been reported. 32P-(138) rapidly penetratedinto tissues of rice plants but information on degradation was not provided.Analysis of methanol rinses of bean leaves showed that (138) was rapidly de-graded via similar pathways as (135), but oxidation of the aryl methyl group toCOOH was characteristically detected. In the case of apple fruits, the oxon and3-methyl-4-nitrophenol were identified as major degradates in the acetone wash,the former of which was not detected in the homogenates. In the rinsate, thecorresponding S-isomer was also confirmed. Therefore, both oxon and S-isomerwere most likely to be photochemically produced on the surface of apple fruits,as was also demonstrated by Fukushima et al. (2003) on tomato fruits. For 14C-cyanophos (137) on bean plants, photolysis was of minor importance (Chiba etal. 1976). The degradation of bromophos (140) on tomato leaves was also found


Fig.

24.

Phot

odeg

rada

tion

ofN

-(α-

tric

hlor

omet

hyl-

p-m

etho

xybe

nzyl

)-p-

met

hoxy

anili

ne.

72 T. Katagi

to be less important than metabolism in tissues (Stiasni et al. 1969). In contrast,fenthion (143) was very rapidly degraded on coastal bermudagrass or cornplants with successive oxidation of the S-methyl sulfur to form the correspond-ing sulfoxide and sulfone (Leuch and Bowman 1968). Residue analysis of (143)and its degradates was conducted for a citrus grove, and both sulfoxide andsulfone were detected only in the orange peel, showing that these oxidations aresurface reactions on fruits (Minelli et al. 1996). Dechlorination of chlorpyrifos(145) was confirmed by a trace amount through its photodegradation on thedorsal leaves of soft shield fern by irradiation, but the main degradates were3,5,6-trichloropyridinol and the oxon (Walia et al. 1988). Formation of the oxonfrom isoxathion (151) on foliage was found insignificant, as demonstrated inmetabolism of 14C-(151) (Ando et al. 1975) and residue trials (Endo et al. 1985).When phoxim (152) was applied outdoors to tomato plants, the surface rinse ofleaves with acetone was found to contain two unknown photoproducts morepolar than (152) (Makary et al. 1981). The corresponding oxon was confirmedby GC analysis of corn forage treated with emulsifiable concentrate formulationof (152) but its route of formation was ambiguous due to the harsh Soxhletextraction (Bowman and Leuck 1971). Ivie and Bull (1976) conducted photo-degradation studies of 14C-sulprofos (161) on cotton leaves and confirmed thepredominant formation of sulfoxide and sulfone in the methanol rinse. Metabo-lism of 14C- and 32P-phenthoate (168) in Valencia orange leaves and fruit showedthat the main degradation pathways on the surface were P=S oxidation to theoxon, stepwise hydrolysis at the S-C bond and carboxylate moiety to mandelicacid, and hydrolysis of the P-S bond followed by formation of disulfide (Takadeet al. 1976). The other minor reaction, O-demethylation, was detected mostly onorange tree leaves. Similar degradation profiles were observed for 14C-azinphos-methyl (169) in corn and bean metabolism. Extraction by homogenization onlymade a site of conversion difficult to identify, but similar profiles on glass underirradiation showed possible photodegradation on plant surfaces (Liang and Kich-tenstein 1976).

32P- and 14C-Dimethoate (165) was gradually degraded on leaves via P=Soxidation followed by conversion of the amide moiety finally to the carboxylderivative of the oxon, including oxidative N-dealkylation (Dauterman et al.1960; Lucier and Menzer 1968). Due to lack of a chromophore in (165), indirectphotolysis may account for a part of these conversions. Formothion (166) under-went rapid conversion to (165) on bean leaves but contribution of photolysis isunclear (Sauer 1972). Malathion (167) is considered to be also resistant to directphotolysis, and only hydrolysis of ester linkages is a dominant pathway (Awadet al. 1967; El-Refai and Hopkins 1972; Mostafa et al. 1974). 14C-Edifenphos(173) was slowly degraded on rice leaves, presumably via hydrolysis, and thusthe contribution of photolysis also was unlikely (Ishizuka et al. 1973). Photoin-duced cis/trans isomerization was expected for mevinphos (155), but its highvolatility made it difficult to confirm this possibility (Casida et al. 1956). Hydrol-ysis of monocrotophos (156) and dicrotophos (157) was found only predominanton plant surfaces without any contribution from photolysis (Lindquist and Bull


1967; Beynon and Wright 1972; Bull and Lindquist 1964). Bull et al. (1967)conducted a metabolism study in cotton using the cis- and trans-isomers of 14C-and 32P-phosphamidon (158) and reported faster degradation of the cis-isomeron foliage, which would be due to its easier hydrolysis. In contrast, photoin-duced E/Z isomerization was observed for 14C-tetrachlorovinphos (154) onleaves of cabbage, apple, bean, and rice (Beynon and Wright 1969; Dureja etal. 1987b). Acephate (174), cyanofenphos (180), leptophos (181), and butonate(182), having P-C and P-N bonds in their molecules, underwent either O-deal-kylation or ester hydrolysis, and photolysis on plant surfaces seemed to be ofminor importance (Chiba et al. 1976; Zayed et al. 1978; Bull 1979: Derek et al.1979).

Pyrethroids The trans- and cis-isomers of 14C-phenothrin (13) were rapidlydegraded on kidney bean and rice plants via unique ozonization of the isobu-tenyl side chain successively to the corresponding aldehyde and carboxylic acid(Nambu et al. 1980); this seems to be a typical example of reaction of pesticideswith active oxygen species in air. Measurable isomerization was observed forthe aldehyde and carboxylic acid derivatives, at least in part showing involve-ment of photoprocess. Instead of oxidation, the cis-isomer of 14C-cypermethrin(19) predominantly underwent cis/trans isomerization on cotton and bean leavesgrown outdoors (Cole et al. 1982). A similar phototransformation was observedfor deltamethrin (22) (Ruzo and Casida 1979; Maguire 1990). Rapid conversionof tralomethrin (25) and tralocythrin (26) to (22) and (19) followed by isomer-ization to the trans-isomers was observed together with a slight epimerizationat the benzyl carbon, possibly as a dark reaction (Cole et al. 1982). Dissipationof fenpropathrin (24) on leaves of mandarin orange was mostly due to penetra-tion into leaf tissues (Takahashi et al. 1985b). The insignificant contribution byphotolysis was accounted for by the very slight differences in half-lives when(24) was applied to green beans and tomatoes in winter and spring when sun-light intensity to (24) was different (Martinez Galera et al. 1997). Decarboxyl-ation proceeded for fenvalerate (27) on cotton (Holmstead et al. 1978b) andbean leaves (Ohkawa et al. 1980). Similar profiles have been separately reportedfor metabolism in spring wheat, and the analysis of hexane rinse of leavesclearly demonstrated that decarboxylation is a photoreaction (Lee et al. 1988).Similar photoinduced decarboxylation via radical processes was detected forflucythrinate (29) on French bean leaves with degradates formed via cleavageat the O-CH bond (Chattopadhyaya and Dureja 1991).

Carbamates Metolcarb (61), xylylcarb (63), and trimethacarb (64) likely dissi-pated from plant foliage mainly by volatilization, with photochemical reactionsplaying a minor role (Slade and Casida 1970; Ohkawa et al. 1974a). Althoughthe hydroxylated derivative at the methylene carbon of the isobutyl group wasconfirmed for 14C-fenobucarb (62) applied to rice leaves, the trace amount de-tected implied that photolysis was of minor importance (Ogawa et al. 1976).For propoxur (65), Abdel-Wahab et al. (1966) reported that its foliar application

74 T. Katagi

to garden snapbean resulted in rapid dissipation, but the degradation profileswere not clear. They also showed stepwise sulfur oxidation at the thiomethylgroup of methiocarb (68) to its sulfoxide and sulfone. On the leaves treated withaminocarb (66) and mexacarbate (67), the stepwise oxidation proceeded out-doors at the N,N-dimethylamino moiety, evidenced by analysis of chloroformrinsates (Abdel-Wahab and Casida 1967). Because similar reactions were identi-fied when silica gel was used, the oxidation reactions were likely to be photoin-duced processes. Carbaryl (71) underwent hydroxylation at the 4- or 5-positionof the naphthyl moiety and N-methyl group by stem injection (Mumma et al.1971), but its photolytic behavior on plant surfaces was unclear (Abdel-Wahabet al. 1966). The contribution of photodegradation was not clear for carbofuran(72), but either hydrolysis of the carbamate linkage or stepwise oxidation atthe 3-position of the 2,3-dihydrobenzofuranyl moiety proceeded on strawberry(Archer et al. 1977). When 14C-benfuracarb (89) was applied to leaves of bushbean, cotton, and corn, (89) was gradually degraded to (72) on leaf surfaces viacleavage of the N(CH3)-SNRR′ bond (Tanaka et al. 1985). Cleavage was consid-ered to also occur at the N(CH3)S-NRR′ bond, resulting in formation of thedimer derivatives of (72) possessing Sn (n > 1) or derivatives having the chemi-cal structure of (89) but with Sn (n > 1) linkage. Because these products weredetected predominantly on the leaf surface, photodegradation most likely ac-counted for this conversion. From 14C-carbosulfan (88), similar derivatives hav-ing the Sn linkage were detected only in surface rinse of leaves and fruits ofValencia orange trees (Clay and Fukuto 1984). In addition, S-oxidation to formthe sulfone derivative of (88) occurred mainly on leaf surfaces.

Hydrolysis was the main degradation pathway in plants for oxamyl (74), andno clear explanation about the extent of photodegradation was given (Harvey etal. 1978). In contrast, pirimicarb (78) was known to rapidly dissipate from let-tuce leaves, not only by volatilization but also by stepwise oxidation of theN,N-dimethyl group of the pyrimidyl ring, but the extent of the photochemicalcontribution was not clear (Cabras et al. 1990). Similar oxidation of the N-methyl group was reported for fenothiocarb (85) on mandarin orange trees to-gether with S-oxidation to the sulfoxide (Unai et al. 1986). Benomyl (81) andthiophanate-methyl (92) are known to give the same degradate, MBC (93). MBC(93) was only formed from (81) on leaves of several plants via release of theN-butylcarbamoyl group (Baude et al. 1973). 14C-(92) on leaves of apple andgrape trees gave (93) as a main degradate together with the degaradate wherethe two C=S groups were oxidized to carbonyls (Soeda et al. 1972). Buchenaueret al. (1973) examined the photoreactivity of (92) in solid and aqueous phasesusing UV light and found that (92) was stable as a solid but rapidly degradedto (93) in water. Therefore, the photodegradation of (92) on plant foliage seemsto proceed in an aqueous microenvironment, probably originating from morningdew. MBC (93) was found to be mostly photostable but degradable in the pres-ence of a photosensitizer such as riboflavin (Fleeker and Lacy 1977). Maneb(94) was rapidly degraded to ETU (95) on leaves of tomato and snapbean plants,followed by further transformation to either ethyleneurea via C=S oxidation to


C=O or dimerization to Jaffe’s base (1-(2-imidazoline-2-yl)-2-imidazolinethi-one) (Rhodes 1977). Similar degradates were identified in aqueous photolysis,showing that these reactions were likely to proceed via photolysis.

Amides, Imides, and Ureas Flutolanil (39) showed slow dissipation on cucum-ber leaves via deisopropylation at the phenyl ring followed by methylation orhydroxylation at the 4-position of the aniline ring (Uchida et al. 1983). Conver-sion on plant surfaces was minimum for carboxin (42) (Buchenauer 1975). Pro-pyzamide (45) was cyclized via reaction between carbonyl oxygen and ethynylcarbon to form the oxazoline ring followed by its opening to N-(1,1-dimethyla-cetonyl)benzamide (Yih and Swithenbank 1971). Because this conversion isknown in its hydrolysis (Katagi 2002b), contribution of photolysis was question-able. Opening of its imide ring was observed for procymidone (108) on cucum-ber leaves but only in trace amounts (Mikami et al. 1984a). Methazole (112)underwent either opening of the 1,2,4-oxadiazoline-3,5-dione ring to the 3-methyl-1-phenylurea derivative or decarboxylation to the 2-oxo-benzimidazolederivative, with greater amounts detected on the surface of cotton leaves (Do-rough et al. 1973). The latter degradate at least was considered to be formed byphotoreaction because it was also detected in aqueous photolysis. Photoreactionscarcely proceeded for lenacil (199) on sugar beet (Zhang et al. 1999). Diflube-nzuron (59) on cotton leaves was resistant to photolysis with insignificant trans-location (Bull and Ivie 1976; Mansager et al. 1979). Rodriguez et al. (2001)identified 2,6-difluorobenzamide as a sole degradate through residue trials onpine needles. As cumulative solar irradiation was found to correlate highly withdissipation of (59), and 4-chloroaniline formed via hydrolysis was not detected,photodegradation forming the corresponding benzamide and isocyanate wasconsidered most likely. The lack of detection of the latter degradate may beaccounted for by its high volatility. In contrast, diafenthiuron (57) exhibitedrapid photodegradation on cotton leaves (Drabek et al. 1992) and Chinese cab-bage (Keum et al. 2002) via reaction of the thiourea moiety with 1O2 to carbodii-mide. Tribenuron methyl (99) underwent cleavage of each bond in the sulfonyl-urea bridge with its contraction on wheat leaves. These processes were mostlikely photoreactions because similar degradates were identified on glass platesexposed to sunlight (Bhattacharjee and Dureja 2002). In contrast, most of 14C-thifensulfuron (104) remained unchanged in the surface rinse of soybean plants,with trace amounts of thiophene-2-methoxycarbonyl-3-sulfonamide and the 2-amino-1,3,5-triazine derivative (Brown et al. 1993).

Azoles On the leaves of marrow plants, triadimefon (188) was converted totwo diastereomers of triadimenol (189) via reduction of carbonyl group toCHOH, but the contribution of photolysis was unclear (Clark et al. 1978). Deg-radation of (189) was briefly investigated on apple leaves with 1-(4-chlorophen-oxy)-3,3-dimethylbutan-2-one being detected as the sole metabolite (Clark andWatkins 1986). Because the same degradate was identified through photolysisin methanol, its formation on foliage was likely to be a photoprocess. Although

76 T. Katagi

dissipation profiles of the other azole fungicides on grape have been investi-gated, their degradation pathways are not available (Cabras et al. 1997a, 1998;Peacock et al. 1994). For fluotrimazole (195), the substitution of the 1,2,4-trai-zole moiety with the hydroxyl group was confirmed on leaves of barley, withthe photo-induced cleavage of C-N bond being proposed (Clark et al. 1983).

Miscellaneous Although 2,4-D (1) does not possess UV absorption >290 nm,more of (1) was lost from Zea mays leaves by exposure to UV light >290 nmthan the dark control, and thus the possible photosensitization of either somecomponents in epicuticular waxes or a coexisting oxysorbic surfactant mightoccur (Venkatesh and Harrison 1999). The degradation pathway was not clearbut may be estimated by the results of residue trials for triclopyr (7). When (7)was sprayed on grasses, it was rapidly degraded to give 3,5,6-trichloro-2-pyridi-nol with a trace amount of 2-methoxy-3,5,6-trichloropyridine (Norris et al.1987); this suggests the possible cleavage of O-CH2 and the following decarbox-ylation are involved in degradation. The photostability of 2,3,7,8-TCDD (129)was examined on excised leaves of rubber plant under sunlight (Crosby andWong 1976). TCDD (129) was degraded possibly via direct photolysis becauseits UV absorption maximum was at �300 nm. Although its degradation pathwaywas not available, dechlorination was most probable based on the latter photo-degradation studies (Schuler et al. 1998). Both dinoseb (202) and dinobuton(203) were rapidly degraded to several unknown compounds on garden snap-bean seedlings, and 5%–6% of (203) was found to be converted to (202) (Mat-suo and Casida 1970). In the presence of a photosensitizer such as rotenone,these pesticides were more rapidly decomposed via oxidation, ester cleavage,and reduction of the nitro group (Bandal and Casida 1972).

Sethoxydim (223) was degraded on grasses to eight unknown products andthe O-deethylated derivative, which were also detected in photolytic and thermaltransformation (Campbell and Penner 1985b). For alloxidim (224), the contribu-tion of photolysis to its dissipation on sugar beet leaves was examined by Soedaet al. (1979). Alloxidim was degraded via cleavage of the N-O bond to formthe amine derivative and Beckmann rearrangement to the two cyclized deriva-tives. The former main degradate was also formed either by UV photolysis onsilica gel or by catalytic reduction of (224) with 10% Pd/C in a hydrogen atmo-sphere, indicating photoinduced reductive dissociation was most probable on theleaf surface. 14C-Imidacloprid (215) on tomato leaves dissipated under sunlightvia oxidation of the imidazolidinimine ring and stepwise loss of the nitroiminogroup to finally form the imidazolidin-2-one derivative (Scholz and Reinhard1999). As the dark control resulted in minimum degradation, these degradatesoriginated from photolysis. For fipronil (220), photochemical conversion of thetrifluoromethylsulfinyl moiety via homolytic cleavage of the S-CF3 or S-C(pyr-azolyl) bond was confirmed on leaves of corn, sweet pea, and pear (Hainzl andCasida 1996). In contrast, the main degradate in field residue trials was thesulfone derivative with a trace of the desulfinyl derivative (Fenet et al. 2001).The well-aerated leaf surface with higher levels of water under tropical condi-


tions might result in favorable photoinduced S-oxidation. Thiabendazole (212)was photodecomposed on sugar beet, possibly via oxidation to benzimidazole-2-carboxamide and benzimidazole, but only in trace amounts (Jacob et al. 1975).Photoinduced oxidation of an alkyl chain was reported for guazatine (245) ondwarf apple trees (Sato et al. 1985a). Oxidation to ketone at the 4-position tothe NH moiety followed by methylation at the 3- or 5-position was proposedto proceed via reaction with the hydroxyl radical or some sensitizer in waxcomponents.

Moye et al. (1990) investigated the degradation of 3H-, 14C-avermectin B1a

(250) in celery seedlings. By HPLC analysis of homogenization acetone ex-tracts, the ∆8,9 isomer formed via photoinduced geometric isomerization at 8-and 9-positions of the macrocycle was detected as a main degradate. Analysisof methanol rinsates from cabbage plant treated with 14C-4″-(epi-methylamino)-4′-deoxyavermectin B1a benzoate [MAB; (251)] showed that surface degradationwas mainly due to photolysis; isomerization of the 8,9-double bond, stepwiseoxidation of the N-methyl group via N-formyl to the amino group, hydroxylationat the 8α-position, and loss of the outer sugar by cleavage of the ether bond(Wrzesinski et al. 1996). The other example is Spinosad consisting of spinosynA and D. Saunders and Bret (1997) utilized 14C-spinosyn A (252) for foliar ortopical application to cotton, turnip, cabbage, and apple fruits. Although noinformation on the degradation pathway is available, by analogy with (251),oxidation at double bonds, N-demthylation, and ether cleavage may occur.

Summary

Photodegradation is an abiotic process in the dissipation of pesticides wheremolecular excitation by absorption of light energy results in various organicreactions, or reactive oxygen species such as OH�, O3, and 1O2 specifically ornonspecifically oxidize the functional groups in a pesticide molecule. In the caseof soil photolysis, the heterogeneity of soil together with soil properties varyingwith meteorological conditions makes photolytic processes difficult to under-stand. In contrast to solution photolysis, where light is attenuated by solid parti-cles, both absorption and emission profiles of a pesticide are modified throughinteraction with soil components such as adsorption to clay minerals or solu-bilization to humic substances. Diffusion of a pesticide molecule results in het-erogeneous concentration in soil, and either steric constraint or photoinducedgeneration of reactive species under the limited mobility sometimes modifiesdegradation mechanisms. Extensive investigations of meteorological effects onsoil moisture and temperature as well as development of an elaborate testingchamber controlling these factors seems to provide better conditions for re-searchers to examine the photodegradation of pesticides on soil under conditionssimilar to the real environment. However, the mechanistic analysis of photodeg-radation has just begun, and there still remain many issues to be clarified. Forexample, how photoprocesses affect the electronic states of pesticide moleculeson soil or how the reactive oxygen species are generated on soil via interaction

78 T. Katagi

with clay minerals and humic substances should be investigated in greater detail.From this standpoint, the application of diffuse reflectance spectroscopy andusage or development of various probes to trap intermediate species is highlydesired. Furthermore, only limited information is yet available on the reactionsof pesticides on soil with atmospheric chemical species. For photodegradationon plants, the importance of an emission spectrum of the light source near itssurface was clarified. Most photochemical information comes from photolysisin organic solvents or on glass surfaces and/or plant metabolism studies. Epicu-ticular waxes may be approximated by long-chain hydrocarbons as a very vis-cous liquid or solid, but the existing form of pesticide molecules in waxes isstill obscure. Either coexistence of formulation agents or steric constraint in therigid medium would cause a change of molecular excitation, deactivation, andphotodegradation mechanisms, which should be further investigated to under-stand the dissipation profiles of a pesticide in or on crops in the field. A thin-layer system with a coat of epicuticular waxes extracted from leaves or isolatedcuticles has been utilized as a model, but its application has been very limited.There appear to be gaps in our knowledge about the surface chemistry andphotochemistry of pesticides in both rigid media and plant metabolism. Photo-degradation studies, for example, by using these models to eliminate contribu-tion from metabolic conversion as much as possible, should be extensively con-ducted in conjunction with wax chemistry, with the controlling factors beingclarified. As with soil surfaces, the effects of atmospheric oxidants should alsobe investigated. Based on this knowledge, new methods of kinetic analysis or adevice simulating the fate of pesticides on these surfaces could be more ratio-nally developed. Concerning soil photolysis, detailed mechanistic analysis ofthe mobility and fate of pesticides together with volatilization from soil surfaceshas been initiated and its spatial distribution with time has been simulated withreasonable precision on a laboratory scale. Although mechanistic analyses havebeen conducted on penetration of pesticides through cuticular waxes, its combi-nation with photodegradation to simulate the real environment is awaiting fur-ther investigation.


Table Listing

Table 1. ............................................................................................................ 80–84Table 2. ............................................................................................................ 85Table 3. ............................................................................................................ 86–87Table 4. ............................................................................................................ 88Table 5. ............................................................................................................ 89–91Table 6. ............................................................................................................ 92–93Table 7. ............................................................................................................ 94–100Table 8. ............................................................................................................ 101–103Table 9. ............................................................................................................ 104Table 10. ............................................................................................................ 105–119Table 11. ............................................................................................................ 120–128

80 T. Katagi

Tab

le1.

Wav

elen

gth

offl

uore

scen

cean

dph

osph

ores

cenc

esp

ectr

aof

pest

icid

es.

Fluo

resc

ence

Phos

phor

esce

nce

No.

Pest

icid

eE

m.

Ex.

Sola

τbT

cE

m.

Ex.

Sol

τT

Ref

eren

ce

12,

4-D

——

510

280

EPA

LSo

glie

roet

al.

1985

495

290

E<0

.2s

LM

oye

and

Win

efor

dner

1965

22,

4,5-

T48

030

0E

<0.2

sL

Moy

ean

dW

inef

ordn

er19

653

MC

PA30

923

0A

rM

uelle

ret

al.

1992

6Fl

uazi

fopb

utyl

450

267

Ar

Mue

ller

etal

.19

929

Pyre

thru

m-I

338

292

E25

431

279

EL

Bow

man

and

Ber

oza

1967

a10

Alle

thri

n33

229

2E

2543

728

2E

LB

owm

anan

dB

eroz

a19

67a

19C

yper

met

hrin

321

296

EPA

L48

127

3E

PAL

Tak

ahas

hiet

al.

1985

a28

Esf

enva

lera

te42

527

7A

LK

atag

i19

9134

Ala

chlo

r34

925

5A

rM

uelle

ret

al.

1992

35M

etol

achl

or34

525

0A

rM

uelle

ret

al.

1992

42C

arbo

xin

462

311

EW

LA

aron

etal

.19

7944

Nap

tala

m42

732

8A

Wr

Kra

use

1983

515

300

SSW

Van

nelli

and

Schu

lman

1984

47N

apro

pam

ide

340

282

Sr

528

282

S0.

2m

sr

Mur

illo

Pulg

arin

and

Gar

cıa

Ber

mej

o20

0233

529

3M

rA

rgau

er19

8034

229

6A

Wr

Kra

use

1983

520

310

SSW

Van

nelli

and

Schu

lman

1984

53D

iuro

n31

625

5E

PAL

498

255

EPA

LSo

glie

roet

al.

1985

55Fl

umet

uron

329

294

Ar

Mue

ller

etal

.19

9260

Phen

mec

283

261

EPA

r37

526

1E

PA2.

7s

LA

ddis

onet

al.

1977

61M

etol

carb

283

264

EPA

r37

926

4E

PA3.

4s

LA

ddis

onet

al.

1977

64T

rim

etha

carb

287

268

EPA

r39

326

8E

PA2.

9s

LA

ddis

onet

al.

1977

65Pr

opox

ur32

427

6E

2540

028

0E

0.8

sL

Bow

man

and

Ber

oza

1967

b


Tab

le1.

(Con

tinue

d).

Fluo

resc

ence

Phos

phor

esce

nce

No.

Pest

icid

eE

m.

Ex.

Sola

τbT

cE

m.

Ex.

Sol

τT

Ref

eren

ce

66A

min

ocar

b37

526

2E

2546

025

3E

0.6

sL

Bow

man

and

Ber

oza

1967

b35

824

8E

PAr

459

248

EPA

1.2

sL

Add

ison

etal

.19

7746

029

0E

0.6

sL

Moy

ean

dW

inef

ordn

er19

6567

Mex

acar

bate

373

272

E25

430

267

E0.

6s

LB

owm

anan

dB

eroz

a19

67b

360

262

EPA

r42

326

2E

PA0.

7s

LA

ddis

onet

al.

1977

440

285

E0.

5s

LM

oye

and

Win

efor

dner

1965

68M

ethi

ocar

b—

—E

2543

027

0E

0.2

sL

Bow

man

and

Ber

oza

1967

b43

527

5E

<0.2

sL

Moy

ean

dW

inef

ordn

er19

6571

Car

bary

l34

028

5E

2551

828

8E

2.1

sL

Bow

man

and

Ber

oza

1967

b32

628

1E

PAr

467,

503

281

EPA

2.2

sL

Add

ison

etal

.19

7733

228

0M

rA

rgau

er19

8033

828

6A

Wr

Kra

use

1983

334

285

EPA

LSo

glie

roet

al.

1985

495,

530

295

SSW

rV

anne

llian

dSc

hulm

an19

8448

5,51

030

0E

2.0

sL

Moy

ean

dW

inef

ordn

er19

6572

Car

bofu

ran

325

281

E25

400

282

E1.

7s

LB

owm

anan

dB

eroz

a19

67b

304

280

Mr

Arg

auer

1980

306

278

AW

rK

raus

e19

8340

028

5E

1.6

sL

Moy

ean

dW

inef

ordn

er19

6573

Mob

am32

026

6A

Wr

Kra

use

1983

460

290

SSW

rV

anne

llian

dSc

hulm

an19

8475

Dim

etila

n37

530

4E

2542

224

3E

0.6

sL

Bow

man

and

Ber

oza

1967

b76

Pyro

lan

400

266

E25

400

257

E1.

6s

LB

owm

anan

dB

eroz

a19

67b

77Is

olan

365

270

E25

421

260

E0.

7s

LB

owm

anan

dB

eroz

a19

67b

82 T. Katagi

Tab

le1.

(Con

tinue

d).

Fluo

resc

ence

Phos

phor

esce

nce

No.

Pest

icid

eE

m.

Ex.

Sola

τbT

cE

m.

Ex.

Sol

τT

Ref

eren

ce

78Pi

rim

icar

b38

031

0M

rA

rgau

er19

8079

Prop

ham

306

242

AW

rK

raus

e19

8380

Chl

orpr

opha

m—

—E

2540

024

7E

0.3

sL

Bow

man

and

Ber

oza

1967

b81

Ben

omyl

300

286

Mr

Arg

auer

1980

402

295

SSW

rV

anne

llian

dSc

hulm

an19

8438

628

6E

W2.

6s

LA

aron

etal

.19

7948

030

8SS

S25

Aar

onet

al.

1979

107

Folp

et44

030

5E

WL

Aar

onet

al.

1979

489

306

SSS

25A

aron

etal

.19

7911

6D

ichl

orob

enil

313

285

EPA

L41

228

5E

PAL

Sogl

iero

etal

.19

8511

9C

hlor

ambe

n40

532

5A

rM

uelle

ret

al.

1992

120

Picl

oram

425

320

Ar

450

320

EPA

40m

sL

Gla

ss19

7513

0D

DT

420

270

E0.

2s

LM

oye

and

Win

efor

dner

1965

131

DD

E42

527

0E

0.2

sL

Moy

ean

dW

inef

ordn

er19

6513

2D

DD

298

245

EPA

L42

624

5E

PAL

Sogl

iero

etal

.19

8541

526

5E

0.2

sL

Moy

ean

dW

inef

ordn

er19

6513

3D

icof

ol51

528

5E

0.2

sL

Moy

ean

dW

inef

ordn

er19

6513

4M

etho

xych

lor

386

270

EPA

LSo

glie

roet

al.

1985

380

275

E0.

7s

LM

oye

and

Win

efor

dner

1965

135

Para

thio

n51

536

0E

<0.2

sL

Moy

ean

dW

inef

ordn

er19

6513

9Fe

nchl

orph

os47

530

0E

<0.1

sL

Moy

ean

dW

inef

ordn

er19

6514

4D

iazi

non

395

275

E5.

0s

LM

oye

and

Win

efor

dner

1965

145

Chl

orpy

rifo

s—

—48

428

0E

PAL

Sogl

iero

etal

.19

85


Tab

le1.

(Con

tinue

d).

Fluo

resc

ence

Phos

phor

esce

nce

No.

Pest

icid

eE

m.

Ex.

Sola

τbT

cE

m.

Ex.

Sol

τT

Ref

eren

ce

147

Cou

map

hos

380

320

Mr

Arg

auer

1980

380

320

AW

rK

raus

e19

8335

932

0E

PAL

Sogl

iero

etal

.19

8551

532

5SS

WV

anne

llian

dSc

hulm

an19

8451

033

5E

<0.2

sL

Moy

ean

dW

inef

ordn

er19

6514

9Py

razo

phos

420

252

Mr

Arg

auer

1980

169

Azi

npho

smet

hyl

340

290

Mr

Arg

auer

1980

457

280

EPA

LSo

glie

roet

al.

1985

420

325

E0.

6s

LM

oye

and

Win

efor

dner

1965

170

Phos

alon

e31

028

2M

rA

rgau

er19

8032

028

7A

Wr

Kra

use

1983

172

Phos

met

440

305

E0.

8s

LM

oye

and

Win

efor

dner

1965

188

Tri

adim

efon

420

310

C0.

3ps

21D

aSi

lva

etal

.20

0118

9T

riad

imen

ol32

028

5C

0.7p

s21

Da

Silv

aet

al.

2001

200

Ben

tazo

ne45

034

0M

rA

rgau

er19

8043

326

0A

rM

uelle

ret

al.

1992

212

Thi

aben

dazo

le34

031

0M

rA

rgau

er19

8021

4N

orfl

uraz

on39

829

4A

rM

uelle

ret

al.

1992

218

Oxy

fluo

rfen

350

323

A18

nsr

411

330

EPA

LSc

rano

etal

.19

9921

9E

thox

yqui

n44

036

0M

rA

rgau

er19

8044

635

8A

Wr

Kra

use

1983

225

Para

quat

360

282

Ar

Mue

ller

etal

.19

9234

528

5A

rV

illem

ure

etal

.19

8622

6D

iqua

t34

531

0A

rM

uelle

ret

al.

1992

84 T. Katagi

Tab

le1.

(Con

tinue

d).

Fluo

resc

ence

Phos

phor

esce

nce

No.

Pest

icid

eE

m.

Ex.

Sola

τbT

cE

m.

Ex.

Sol

τT

Ref

eren

ce

228

Qui

nom

ethi

onat

e38

036

0M

rA

rgau

er19

8039

536

2A

Wr

Kra

use

1983

535

360

SSW

rV

anne

llian

dSc

hulm

an19

8423

0Im

azaq

uin

453

259

Ar

Mue

ller

etal

.19

9223

9Fe

nari

mol

360

295

E0.

2ns

2541

829

5D

LC

once

icao

etal

.19

9724

7N

AA

324

290

Mr

Arg

auer

1980

248

War

fari

ne39

031

0M

rA

rgau

er19

8047

532

0SS

Wr

Van

nelli

and

Schu

lman

1984

Em

.&

Ex.

,em

issi

onan

dex

cita

tion

wav

elen

gths

innm

.—

,N

otde

tect

ed.

a Solv

ent:

A(a

ceto

nitr

ile),

AW

(ace

toni

trile

-wat

er,

1/1)

,C

(cyc

lohe

xane

),D

(die

thyl

ethe

r),

E(e

than

ol),

EW

(eth

anol

-wat

er,

1/9)

,H

(hex

ane)

,M

(met

hano

l),

S(s

odiu

mdo

decy

lsu

lfat

em

icel

le),

EPA

(die

thyl

ethe

r-pe

ntan

e-et

hyl

alco

hol,

5/5/

2),

SSW

(sol

idst

ate,

Wha

tman

No.

42pa

per)

,SS

S(s

olid

stat

e,S&

S904

filte

rpa

per)

.b τ,

lifet

ime.

c Tem

pera

ture

:r:

room

tem

pera

ture

;L

:77

K;

valu

esin

°C.


Tab

le2.

Max

imum

wav

elen

gths

ofab

sorp

tion

orre

flec

tanc

esp

ectr

aof

chem

ical

sin

clud

ing

pest

icid

es.

Abs

orpt

ion

Ref

lect

ion

No.

Pest

icid

eSo

lven

tλ m

ax(n

m)

Med

ium

λ max

(nm

)R

efer

ence

12,

4-D

N.R

.24

0Si

lica

gel

282

Parl

ar19

9024

Fenp

ropa

thri

nA

ceto

nitr

ile27

8T

hree

Japa

nese

soils

280

Kat

agi

1993

b28

Esf

enva

lera

teA

q.ac

eton

itrile

277

Kao

linite

276

Kat

agi

1991

115

Hex

achl

orob

enze

neH

exan

e21

8,23

1(s

h)Si

lica

gel

241,

255,

288

Gab

etal

.19

75b

121

Pent

achl

orop

heno

lH

exan

e21

8,23

1(s

h),

305

(br)

Silic

age

l/ads

orbe

d24

7,31

0G

abet

al.

1975

b12

4Ph

oto-

diel

drin

Hex

ane

193

Silic

age

l/ads

orbe

d26

4Pa

rlar

1980

130

DD

TH

exan

e23

5,26

5(b

r)Si

lica

gel/a

dsor

bed

240,

270

(br)

Parl

ar19

8013

5Pa

rath

ion

N.R

.26

6Si

lica

gel

291

Parl

ar19

9014

2T

olcl

ofos

-met

hyl

Aq.

acet

onitr

ile27

5,28

2K

aolin

ite27

5,28

3K

atag

i19

9018

5A

traz

ine

Met

hano

l22

6,26

8Si

lica

gel

233,

268

Frei

and

Nom

ura

1968

225

Para

quat

Aqu

eous

255

5%N

a-he

ctri

tesu

spen

sion

263

Bai

ley

and

Kar

ickh

off

1973

242

NM

HA

queo

us34

6N

a-m

ontm

orill

onite

Swy-

136

0M

argu

lies

etal

.19

8824

3PB

acid

pH2

&7

buff

er29

2;27

9Si

lica

gel

orka

olin

ite29

0;30

5K

atag

i19

92—

Nitr

oben

zene

Cyc

lohe

xane

257

+Si

lica

gel/s

lurr

y27

3L

eerm

aker

set

al.

1966

—N

,N-D

imet

hyla

nilin

eC

yclo

hexa

ne25

7,29

7+

Silic

age

l/slu

rry

238,

276

Lee

rmak

ers

etal

.19

66—

Eth

ylpy

ruva

teC

yclo

hexa

ne33

8+

Silic

age

l/slu

rry

323

Lee

rmak

ers

etal

.19

66—

PBB

Hex

ane

253

Silic

age

l28

5,32

58s

h9P

ere

etal

.20

01—

Thi

athr

ene

Cyc

lohe

xane

275

Na-

lapo

nite

265,

290

(sh)

,M

aoan

dT

hom

as19

9345

0–60

0(b

r)—

Cry

stal

viol

etA

queo

us59

5N

a-be

nton

ite54

5–54

7G

hosa

lan

dM

ukhe

rjee

1972

N.R

.:no

tre

port

ed;

sh:

shou

lder

;br

:br

oad;

PBB

:N

-pro

pyl

p-be

nzoy

lben

zam

ide.

86 T. Katagi

Table 3. Emission profiles of photosensitizers.

Sensitizer λmax ES ET ΦISC Reference

Acetone 300 85 78.9 0.90 � 0.98 Carmichael and Hug1989; Tsao andEto 1994

Acetophenone 330 79 73.9 1.00 Carmichael and Hug1989; Tsao andEto 1994

Xanthone 610 77.6 73.9 1.00 Carmichael and Hug1989; Ivie andCasida 1971a

Tsao and Eto 1994

Rotenone 290, 340 63 65 — Mallet and Surette1974; Rau andHormann 1981;Ke et al. 1940

Tryptophan 460 88 64.4 � 65.8 — Carmichael and Hug1989; Segura-Carretero et al.2000; Nag-Chaudhuri andAugenstein 1964

Anthraquinone 390 — 62.4 0.90 Carmichael and Hug1989; Ivie andCasida 1971a

Humic substances — — 60 � 62 — Zepp 1985; VanNoort et al. 1988

TOP-9EO 53 � 54 Tanaka et al. 1991

Riboflavin 440, 470 57.8 50 — Tsao and Eto 1994;Nag-Chaudhuriand Augenstein1964; Chambersand Kearns 1969

Eosin 580 — 45.4 0.43 Carmichael and Hug1989

Eosin Y 520 52.5 45.5 — Chambers andKearns 1969

Rose bengal — — 44.6 0.8 Tsao and Eto 1994

Rhodamine 6G 620 — 43.0 0.002 Carmichael and Hug1989

Rhodamine B 560 49.3 43.0 — Chambers andKearns 1969

Methylene blue 420 — 33.0 0.52 Carmichael and Hug1989


Table 3. (Continued).

Sensitizer λmax ES ET ΦISC Reference

Chlorophyll b 316, 450 — 31.1 0.81 Carmichael and Hug1989

Chlorophyll a 460 — 29.4 0.53 Carmichael and Hug1989

λmax: absorption maximum in nm; ES & ET: energies of excited singlet and triplet states in kcalmole−1; ΦISC: quantum yield of intersystem crossing; —: not applicable; TOP-9EO: nonaethoxy-lated p-(1,1,3,3-tetramethylbutyl)phenol.

88 T. Katagi

Table 4. Reactions of pesticides with active oxygen species.

Source ofNo. Pesticide active oxygen species Reference

Singlet oxygen,1O212 S-Bioallethrin Bengal red B in ethanol, O2, at Ruzo et al. 1980

360 nm

13 Phenothrin Rose bengal in acetonitrile, O2, Ruzo et al. 1982with sunlamp

17 Permethrin Rose bengal in methanol, O2, with Holmstead et al. 1978a40 W GE lamp Ruzo 1983

23 Tetramethrin Rose bengal in acetonitrile, O2, Ruzo et al. 1982with sunlamp

49 Chlorthiamid Riboflavin or methylene blue in Rajasekharan Pillai 1977methanol with sunlight

86 Benthiocarb Eosin in methanol with F40BL Draper and Crosby 1981fluorescent lamp

145 Chlorpyrifos Rose bengal in methanol, air with Walia et al. 1988600 W tungsten lamp

138 Fenitrothion Methylene blue in methanol with Verma et al. 1991200 W tungsten lamp

141 Iodofenphos Rose bengal in methanol, air with Walia et al. 1989b600 W tungsten lamp

146 Potasan Methylene blue in methanol at Abdou et al. 1988>313 nm

Hydroxyl radical, HO�51 Fenuron Aqueous humic acid suspension at Aguer and Richard 1996b

253.7 nm

86 Benthiocarb Aqueous H2O2 at >285 nm or Fen- Draper and Crosby 1981ton’s reagent Draper and Crosby 1984

90 Molinate Aqueous H2O2 at >285 nm Draper and Crosby 1984

122 Aldrin Aqueous H2O2 at >285 nm Draper and Crosby 1984

136 Parathion-methyl O3 (85–200 ppb) at >290 nm Kromer et al. 1999

142 Tolclofos-methyl Clay aqueous suspension at >320 Katagi 1990nm

185 Atrazine Aqueous H2O2 at >290 nm Sanlaville et al. 1996Aqueous Fe(ClO4)3 with sunlight Larson et al. 1991Aqueous semiconductor suspen- Pelizzetti et al. 1993

sion at >340 nm

243 PBacid Fenton’s reagent, N2 Katagi 1992

Ozone, O313 Phenothrin Electric discharge, hexane Ruzo et al. 1982

23 Tetramethrin Electric discharge, hexane Ruzo et al. 1982

135 Parathion Laboratory ozonizer (30–300 ppb) Spencer et al. 1980

Micro-ozonizer Gunther et al. 1970

136 Parathion-methyl Laboratory ozonizer (85–200 ppb) Kromer et al. 1999


Tab

le5.

Com

posi

tion

ofso

lubl

ecu

ticul

arw

axes

offr

uits

and

leav

es.

Com

posi

tion

(%of

wax

)(m

ajor

hom

olog

ue)

Plan

tsp

ecie

sQ

uant

itya /

Ext

ract

bH

CA

LC

AL

DA

CE

SO

ther

sR

efer

ence

<Fru

its>

Mar

shgr

apef

ruit

McD

onal

det

al.

1993

-/C

HC

l 318

.23.

234

.7—

—43

.9(t

erpe

noid

)

App

leB

eldi

nget

al.

1998

989/

CH

Cl 3

18.9

10.2

—69

.8—

0.8

(ket

ones

)[C

29]

[C28

][u

rsol

ic]

Ora

nge

Bak

eret

al.

1975

30�

50/C

HC

l 340

.112

.028

.519

.3—

—[C

27,2

9,31

][C

24,2

6,28

][C

24,2

6,28

][C

26,2

8,30

,32]

Lem

onB

aker

etal

.19

7520�

40/C

HC

l 322

.915

.043

.418

.7—

—[C

29,3

1][C

24,2

6,28

][C

24,2

6,28

,30]

[C24

,28,

30,3

2]

Gra

peR

adle

ran

dH

orn

1965

N.R

./lig

ht1

4012

718

—pe

trol

eum

[C25

,27,

29,3

1][C

24,2

6,28

][C

24,2

6,28

][C

20,2

4,26

][C

46]

Tom

ato

Bak

eret

al.

1982

16�

21/C

HC

l 330

–50

——

<0.5

—30�

50(a

myr

in)

[C29

,31]

5�

30(n

arin

geni

n)

Egg

plan

tB

aker

etal

.19

75N

.R.

53—

—47

——

90 T. Katagi

Tab

le5.

(Con

tinue

d).

Com

posi

tion

(%of

wax

)(m

ajor

hom

olog

ue)

Plan

tsp

ecie

sQ

uant

itya /

Ext

ract

bH

CA

LC

AL

DA

CE

SO

ther

sR

efer

ence

<Lea

ves>

Bitt

eror

ange

Haa

san

dSc

honh

err

1979

9.8/

CH

Cl 3

6�

2731�

55—

18�

3113�

35—

[C29

,31,

33]

[C26

,32,

34]

[C16

,18]

[C40

,42]

Peac

hB

ukov

acet

al.

1979

40�

69/C

HC

l 3�

10�

20—

�20

20�

3010�

20(s

tero

l)B

aker

etal

.19

79[C

25,2

7,29

,31]

[C26

,28,

30,3

2][u

rsol

ic]

[C48

,50,

52]

Tea

crab

appl

eB

aker

and

Hun

t19

8138

/CH

Cl 3−

�30

�20

—�

30�

5�

10(β

-am

yrin

)et

her

(1/1

)[C

29,3

1][C

26,2

8,30

][u

rsol

ic]

[C40

,42,

44]

Che

rry

Bak

eran

dH

unt

1981

24/C

HC

l 3−�

5�

10—

�70

<5—

ethe

r(1

/1)

[C29

,31]

[C26

,28]

[urs

olic

][C

42,4

4,46

]

Gra

peB

aker

and

Hun

t19

8112

/CH

Cl 3−

�10

�80

—<5

�5

Tra

ceet

her

(1/1

)[C

29,3

1][C

26,2

8][C

16,1

8][C

42,4

4,46

,48,

50]

(C29

,31

keto

nes)

Ric

eO

’Too

leet

al.

1979

0.42

6/C

HC

l 3�

60—

——

——

[C33

]

Oat

Ben

gsto

net

al.

1978

9�

21/C

HC

l 30.

3�

6.6

39�

65—

2.9�

4.9

——

[C26

]

Bar

ley

Lar

sson

and

Sven

ning

s-16

.1/C

HC

l 31.

082

7.0

1.7

6.1

�7

son

1986

[C29

,31,

33]

[C26

][C

26]

[C16

,18,

26]

[C42

,44,

46,4

8](β

-dik

eton

es)

Sven

ning

sson

1988


Tab

le5.

(Con

tinue

d).

Com

posi

tion

(%of

wax

)(m

ajor

hom

olog

ue)

Plan

tsp

ecie

sQ

uant

itya /

Ext

ract

bH

CA

LC

AL

DA

CE

SO

ther

sR

efer

ence

Cor

nB

arta

and

Kom

ives

1984

N.R

./CH

Cl 3

3.5

59.4

19.5

4.8

12.8

—[C

31]

[C32

][C

32]

[C24

][C

56]

Mai

zeA

vato

etal

.19

90N

.R./C

HC

l 317

149

1442

4(s

tero

ls)

[C29

,31,

33]

[C26

,28,

30,3

2][C

28,3

0,32

][C

26,2

8,30

][C

44,4

6]

Dw

arf

bean

Bak

eran

dH

unt

1981

0.9/

CH

Cl 3−

�5

�80

—<5

�10

Tra

ceet

her

(1/1

)[C

29,3

1,33

][C

26]

[C16

][C

44,5

0](t

rite

rpen

oids

)

Suga

rbe

etB

aker

and

Hun

t19

813.

9/C

HC

l 3−<5

�70

——

�10

�5

ethe

r(1

/1)

[C29

,31,

33]

[C22

,24,

26]

[C38

,40,

42,4

4](β

-sito

ster

ols)

Spin

ach

Bak

er19

825�

10/N

.R.

—>6

0—

——

—

Pota

toSe

n19

875.

4/C

HC

l 339

.024

.58.

62.

219

.65.

9(C

23,2

5ke

tone

s)[C

27,2

9,31

][C

18–3

4][C

22–2

8][C

18–3

4][C

42,4

4]

Whi

tecl

over

Bak

eran

dH

unt

1981

16/C

HC

l 3−�

5�

50�

5<5

�20

—et

her

(1/1

)[C

29,3

1][C

30]

[C26

,28,

30]

[C42

,44,

46,4

8]

ain

µgcm

−2.

b Org

anic

solv

ent

used

for

extr

actio

n.“—

”or

N.R

.:no

tre

port

ed.

Com

posi

tion:

HC

:hy

droc

arbo

n;A

LC

:al

coho

l;A

LD

:al

dehy

de;

AC

:ac

id;

ES:

este

r.

92 T. Katagi

Table 6. Diffusion coefficients.

No. Chemicals Mediuma MCb pH OMb °C Db Reference

Soil and clay1 2,4-D Silt loam 32.5 6.4 7.1 23 6.33 Scott and Phillips

(3/69/28) 1973

33 Propachlor Silt loam 23 7.3 2 27 2.28 Ritter et al. 1973(15/70/15)

50 Diphenamid Silt loam 38 6.4 7.1 24 2.59 Scott and Phillips(3/69/28) 1972

55 Flumeturon Silt loam 32.5 6.4 7.1 23 2.17 Scott and Phillips(3/69/28) 1973

80 Chlorpropham Silt loam 25 6.4 7.1 24 6.22 Scott and Phillips(3/69/28) 1972

114 Lindane Silt loam 10 — 0.58 30 1.57 Ehlers et al. 1969a(–/–/18)

123 Dieldrin Clay loam 53RH 7.8 0.2 20 0.051 Farmer and Jensen(14/19/67) 1970

135 Parathion Silt loam — — 0.5 25 0.6–2.9 Gerstl et al. 1979(–/–/20)

144 Diazinon Silt loam 23 7.3 2 27 0.48 Ritter et al. 1973(15/70/15)

163 Disulfoton Silt loam 32.8 7.8 2.7* 20 0.13 Graham-Bryce(–/–/18) 1969

165 Dimethoate Silt loam 32.8 7.8 2.7* 20 4.94 Graham-Bryce(–/–/18) 1969

185 Atrazine Silt loam 23 7.3 2 27 1.37 Ritter et al. 1973(15/70/15)

Silt loam 38 6.4 7.1 24 3.70 Scott and Phillips(3/69/28) 1972

186 Simazine Silt loam 38 6.4 7.1 24 3.28 Scott and Phillips(3/69/28) 1972

187 Prometone Silt loam 38 6.4 7.1 24 7.69 Scott and Phillips(3/69/28) 1972

194 Triticonazole Loam clay — 8.2 1.0 22 3.0 Beigel et al. 1997(15/54/29)

232 Trifluralin Silt loam 30.4 6.7 4.8 22 0.20 Jacques and(17/66/17) Harvey 1979

Silt loam 38 6.4 7.1 24 0.52 Scott and Phillips(3/69/28) 1972

Kaolinite clay 28 0.003 Balmer et al. 2000

235 Oryzalin Silt loam 30.4 6.7 4.8 22 0.05 Jacques and(17/66/17) Harvey 1979

— Urea (9–41/16– 7–27 — — 25 0.8–7 Sadeghi et al.67/10–51) 1989



No. Chemicals Mediuma MCb pH OMb °C Db Reference

— PEG4000 Sandy loam 30–50 — 2.5 25 0.3–1.6 Barraclough and(38/47/15) Nye 1979

— p-Nitroanisole Kaolinite 28 0.0069 Balmer et al. 2000

Waxes and cuticles1 2,4-D Barley waxes 25 1 × 10−6 Schreiber and

Schonherr 1993Isolated citrus 3 × 10−4 Schonherr and

cuticles Riederer 1989

121 Pentachloro- Barley waxes 25 2 × 10−6 Schreiber andpenol Schonherr 1993

185 Atrazine Isolated citrus 9 × 10−5 Schonherr andcuticles Riederer 1989

189 Triadimenol Barley waxes 25 4 × 10−7 Schreiber andSchonherr 1993

Water— Eight Water 23 51.8 Scott and Phillips

pesticides 1973

aMedium: values in the parentheses are weight % of sand, silt, and clay in soil.bMC: soil moisture content in %; RH: relative humidity; OM: soil organic matter content in % (*,soil organic carbon content); D: apparent diffusion coefficient in mm2 day−1.

94 T. Katagi

Table 7. Photodegradation of pesticides on glass and silica gel surfaces.

Carrier (Label), Light sourceApp DT50 (wavelength or

No. Pesticide (light/dark) season, filter) Reference

1 2,4-D GL(14C) UV fluorescent lamp Venkatesh andN.R. (max. 356 nm) Harrison 1999

3 MCPA GL, 6 × 103 Sunlight (summer) Crosby and Bow-2.5 d/N.R. ers 1985

10 Allethrin GL (14C), 2.6 275W G.E. sunlamp Chen and Casida<5 hr/>32 hr 1969GL, 300 RPR 3500 UV lamp Kimmel et al. 1982N.R. (> 290 nm, Pyrex

glass)GL, 4 × 103 15W Fluorescence Isobe et al. 1984N.R. lamp

13 Phenothrin GL, 100–300 Sunlight (Sept.) Ruzo et al. 1982N.R.GL (10EC), 30– Sunlight (summer) Samsonov and

1000 Makarov 1996�3 hr/N.R.

14 Cyphenothrin SG (14C) RPR 3500A UV lamp Dureja et al. 1984�2 hr/N.R. (max. 360 nm)

15 Resmethrin SG (14C), 10–17 Sunlight Ueda et al. 1974N.R.

16 Kadethrin GL (14C), 35 Sunlight Ohsawa andN.R. Casida 1979

22 Deltamethrin GL (14C), 40 Sunlight Ruzo et al. 1977N.R.

23 Tetramethrin GL (14C), 2.6 275W G.E. sunlamp Chen and Casida<5 hr/>32 hr 1969GL, 100–300 Sunlight (Sept.) Ruzo et al. 1982N.R.

25 Tralomethrin GL (14C), 100 Sunlight Ruzo and CasidaN.R. 1981

26 Tralocythrin GL (14C), 100 Sunlight Ruzo and CasidaN.R. 1981

27 Fenvalerate GL, 127 Sunlight (July–Aug., Holmstead et al.4 d Pyrex glass) 1978b

29 Flucythrinate GL UV light in a Rayonet Chattopadhyaya11.8 hr/N.R. reactor and Dureja 1991

30 Fulvalinate GL (14C), 2–4 Sunlight, outdoors Quinstad and1 d/N.R. Staiger 1984





31 Acrinathrin GL, 0.3–10 500 W high-pressure Samsonov andHg lamp Pokrovskii 2001

2.7 hr/N.R. (313 nm, glass filter)

32 Etofenprox GL, 1–4 RPR 3000 UV lamp Class et al. 19891.7 d (290–320 nm, Pyrex

glass)GL, 140 GL10 UV lamp (254 Tsao and Eto1.94 hr nm) 1990b

34 Alachlor GL Sunlight (Mar.–Apr.) Fang 19776 hr/N.R.

36 Butachlor GL Germicidal lamp (254 Chen and Chen1.5 hr/N.R. nm) 1978

38 Mepronil SG (14C) Sunlight (Sept.–Dec.) Yumita and Yama-36 d/N.R. moto 1982SG, 25 400W high-pressure Yumita et al. 1984N.R. Hg lamp (max. 365

nm)

39 Flutolanil GL, 2.5 × 103 Germicidal UV lamp Tsao and Eto 1991N.R. (254 nm)

40 Niclosamide SG (14C) Long-wave lamp Schultz and Har-20.5 hr/>7 d (290–405 nm) man 1978

41 Naproanilide GL UV germicidal GL10 Tsao and EtoN.R. lamp (>254 nm) 1990a

42 Carboxin GL Sunlight Buchenauer 1975�10 hr/N.R.

46 Isoxaben SG Xenon lamp (Hereaus Mamouni et al.N.R. Suntest) 1992

57 Diafenthiuron TF UV light Drabek et al. 19921 hr/N.R.

59 Diflubenzuron GL, SG RUL 3000 lamp (max. Ruzo et al. 1974N.R. 300 nm)SG(14C), 4.0 Sunlight (summer) Bull and Ivie 1976�4 wk/N.R.

66 Aminocarb SG (14C), 400 UV light at 253.7 nm Abdel-Wahab andN.R. Casida 1967

67 Mexacarbate SG (14C, 3H), 400 UV light at 253.7 nm Abdel-Wahab andN.R. Casida 1967

96 T. Katagi




78 Pirimicarb GL 125W high-pressure Pirisi et al. 199664 min Hg lamp (> 290

nm, Pyrex glass)CE, 0.03 Sunlight (Feb.), out-19 min doors

84 Phenmedi- SG UV light from Xe Schafmeier et al.pham 15 d/144 d lamp (Heraeus sun- 1998

test)

85 Fenothiocarb SG (14C) Sunlight (Sept.–Oct.) Unai and Tomi-45 hr/N.R. zawa 1986

86 Benthiocarb GL (14C) High-pressure Hg Ishikawa et al.1.7 hr/N.R. lamp (max. 365 1977

nm)GL (14C), 1 × 104 Sunlight (3.5–4.5 mW Cheng and HwangN.R. cm−2) 1996

89 Benfuracarb GL Low-pressure Hg Dureja et al. 1990N.R. lamp (254 nm)

91 Cartap GL, 12.7 Germicidal lamp (373 Tsao and Eto 1989N.R. nm)

92 Thiophanate- GL (14C), 33 Sunlight (May–Aug.), Soeda et al. 1972methyl 2.8 d/N.R. outdoors

93 MBC SG (3T,14C), 5.5 Sunlight (July) Fleeker and LacyN.R. 1977

96 Chlorsulfuron SG 125W high-pressure Herrmann et al.60 hr/N.R. Hg lamp (>290 nm, 1985

borosilicate glass)

99 Tribenuron- GL Sunlight (May) or UV Bhattacharjee andmethyl 7 d or 11 hr/N.R. light (max. 254 nm) Dureja 2002

113 DDOD GL (14C), 6.6 500 W Xenon arc Sumida et al. 1973lamp

8 d/>20 d

121 Pentachloro- GL, 1 × 103 125 W high-pressure Piccinini et al.phenol N.R. Hg lamp (>290 nm, 1998

water filter)

122 Aldrin GL Sunlight (June–July) Rosen and Suther-N.R. land 1967SG 125 W high-pressure Gab et al. 1975aN.R. Hg lamp (>290 nm,

Pyrex glass)





123 Dieldrin GL GE G30T8 germicidal Benson 19711 hr/N.R. lamp

125 Endosulfan GL Sunlight (Mar.) Dureja and Muker-N.R. jee 1982

128 Chlordane GL, 890 Sunlight (summer) Benson et al. 1971N.R.SG 125 W high-pressure Gab et al. 1975aN.R. Hg lamp (>290 nm,

Pyrex glass)

130 DDT GL (14C) 15W germicidal lamp Mosier et al. 1969N.R. (254 nm)

136 Parathion- GL (14C), 0.84 Xe lamp in Suntest Kromer et al. 1999methyl �1 d/>1 d CPS+ (>290 nm,

volatility chamber)

137 Cyanophos SG (14C) Sunlight (Sept.–Oct.), Mikami et al. 19764 d/N.R. outdoors

138 Fenitrothion SG (14C) 172.5 W high-pressure Ohkawa et al.15 min–6 d/N.R. Hg lamp or sunlight 1974b

(Nov.)

141 Iodofenphos GL 1 kW metal halide Walia et al. 1989bN.R. lamp (Applied Pho-

tophysics 9500)

143 Fenthion GL Fluorescent lamp Hirahara et al.0.02–1.34 hr/N.R. (380–750 nm), UV 2001

light (UV-A, UV-B,UV-C)

145 Chlorpyrifos GL Low-pressure Hg Walia et al. 198818.7 d/N.R. lamp (254 nm)FP (14C), 1.18 UV light (Pyrex glass) Meikle et al. 19833.2 d/N.R.

148 Quinalphos GL Low-pressure UV Dureja et al. 1988N.R. lamp (254 nm)

150 Pyridafenthion GL, 6.4 Black light fluores- Tsao et al. 1989N.R. cence lamp (>300

nm)

152 Phoxim GL UV light (254 nm & Makary et al. 19814–19 hr/N.R. 350 nm, uncovered

Petri dish)

98 T. Katagi




156 Monocroto- GL (32P) Sunlight in a green- Lindquist and Bullphos 5.5 d/N.R. house. 1967

GL, 1.6 15W germicidal lamp Dureja 1989N.R. (253.7 nm) or sun-

light (Apr.–May)

159 Propaphos SG, GL (14C) Sunlight (Apr.–Aug.) Fujii et al. 19791.2 hr/>72 hr

161 Sulprofos GL (14C), 53 Sunlight (summer) Ivie and Bull 19761.1 d/N.R.

162 Phorate GL Germicidal lamp (254 Sharma and Gupta5 hr/>13 hr nm) 1994

163 Disulfoton GL Fluorescent lamp Hirahara et al.0.41–43.3 hr/N.R. (380–750 nm), UV 2001

light (UV-A, UV-B,UV-C)

165 Dimethoate GL (32P) Sunlight in a green- Dauterman et al.N.R. house. 1960

167 Malathion GL (F) UV (253.7 nm) or Awad et al. 1967N.R. fluorescent (366

nm) light

168 Phenthoate GL (14C,32P) Sunlight (Mar. & Takade et al. 1976<3 d/N.R. Sept.)SG (14C) Sunlight (Sept.–Oct.), Mikami et al.4 d/>8 d outdoors 1977b

170 Phosalone GL 1 kW high-pressure Walia et al. 1989a8.5 d/>15 d metal-halide lamp

(>300 nm)

173 Edifenphos GL (32P), 5.0 UV light Ishizuka et al.�10 d/N.R. 1973

175 Isofenphos GL Low-pressure Hg Dureja et al. 1989N.R. lamp

176 S-2571 SG (3T), 300 172.5W high-pressure Mikami et al.N.R. Hg lamp 1977a

180 Cyanofenphos SG (14C) Sunlight (Sept.–Oct.), Mikami et al.19762 d/N.R. outdoors

181 Leptophos SG (32P) UV light (310 nm) Zayed et al. 19783.4 d/N.R.GL, 100 Sunlight Riskallah et al.20 d/N.R. 1979





183 Dioxaben- SG (14C) Sunlight (Sept.–Oct.), Mikami et al.zofos 2 d/>8 d outdoors 1977b

188 Triadimefon GL, 32 UV light (254 nm) or Nag and Dureja1.3–2.8 hr/N.R. sunlight (Sept.) 1996

189 Triadimenol GL, 51 400 W medium-pres- Clark and WatkinsN.R. sure Hg lamp (boro- 1986

silicate glass)

190 Diniconazole- GL, 50 Sunlight (June) Sharma and Chib-M N.R. ber 1997

191 Propiconazole GL, 147 Sunlight Dureja et al. 1987aN.R.

195 Fluotrimazole GL, 13-50 100 W medium-pres- Clark et al. 1983N.R. sure Hg lamp (boro-

silicate) or summersunlight

200 Bentazone GL (14C) UV lamps (300 & 350 Nilles and Zabik>5 d/N.R. nm) 1975

204 Isoprothiolane SG 10 W germicidal lamp Chou et al. 19803 hr/N.R. (254 nm)

206 Perfluidone GL, 33.6 UV light (254 or 365 Ketchersid and3–6 wk/N.R. nm) Merkle 1975

207 Chlordime- SG (14C) Sunlight Knowles and Senform N.R. Gupta 1969

212 Thiabendazole GL (14C), 19 Sunlight in a green- Jacob et al. 1975>4 mon/N.R. house

220 Fipronil SG, GL, FP Sunlight Hainzl and CasidaN.R. 1996

222 Buprofezin GL Sunlight (Feb.–Mar.) Datta and Walia15 d/N.R. 1997

223 Sethoxydim GL (14C) Sunlight in a green- Campbell and Pen-<1 hr/N.R. house (350 µE m−2 ner 1985a

sec−1)

224 Alloxydim SG (14C) 12W UV light (253.7 Soeda et al. 19790.7, 4.4 hr/ N.R. or 365 nm)

226 Diquat SG (14C) Sunlight (May –June), Smith and GroveN.R. outdoors 1969

232 Trifluralin GL Sunlight (June–July) Wright and WarrenN.R. 1965

100 T. Katagi




236 Fluchloralin GL (14C) RPR UV light (300 & Nilles and Zabik48 hr/N.R. 350 nm, Pyrex 1974

glass)

SG (14C) Sunlight (Aug.–Oct.)N.R.

238 Pendimethalin GL Low-pressure Hg Dureja and WaliaN.R. lamp (254 nm) 1989

241 Fentin acetate SG (14C) 125W high-pressure Barns et al. 1973N.R. Hg lamp (max. 365

nm)

245 Guazatine GL (14C), 0.5 Sunlight lamp (950 Sato et al. 1985b36 hr/N.R. µE m−2 sec−1)

246 Methoprene GL (14C), 11 Sunlight (Oct.) Quinstad et al.6 hr/N.R. 1975

249 Cinmethylin GL, 2 × 103 1 kW Xe lamp (Oriel Grayson et al.N.R. solar simulator, 1987

AM1 filter)

250 Avermectin GL, 0.7 Sunlight Crouch et al. 1991B1a 2–3 hr/N.R.

251 MAB1a GL, 0.7 275 W Suntanner RS Feely et al. 19926.2 hr/N.R. bulb (60–70 mW

cm−2 h−1)

253 Azadirachtin- GL UV light (254 nm) Dureja and John-A 48 min/N.R. son 2000

Medium: Thin film of a pesticide is basically prepared from its organic solution followed by vapor-ization of solvent. When unspecified, nonradiolabeled pesticide was used.“F,” formulation. Materials of carrier are glass (GL), silica gel (SG), filter paper (FP), cellulosesheet (CE), and Teflon sheet (TF). Label, radiolabel; App, application rate in µg cm−2 if describedin the literature; N.R., not reported.


Table 8. Photodegradation of pesticides in organic solvent as model plant cuticles.

Light sourceMedium (wavelength or

No. Pesticide DT50 season, UV filter) Reference

17 Permethrin Methanol RPR 3000 lamp Holmstead et al.1–1.5 hr (290–320 nm) 1978a

21 Cyhalothrin Cyclohexane RPR 3000 UV lamp Ruzo et al. 1987N.R. (290–320 nm,

Pyrex glass)

22 Deltamethrin Hexane Summer sunlight Maguire 1990�2 days (Pyrex glass, out-

doors)Hexane Sunlight Ruzo et al. 1977N.R.

27 Fenvalerate Hexane RPR 3000 UV lamp Holmstead et al.18 min (290–320 nm, 1978b

Pyrex glass)

32 Etofenprox Methanol RPR 3000 UV lamp Class et al. 19895.8 days (290–320 nm,

Pyrex glass)

59 Diflubenzuron Methanol RUL 3000 lamp Ruzo et al. 1974N.R. (>285 nm, borosili-

cate glass)

63 Xylylcarb Ethanol UV light (>265 nm) Kumar et al. 197422.6 hr

64 Trimethacarb Cyclohexane 1 kW Xe-Hg lamp Addison et al.N.R. (>300 nm, Corning 1974

0-54 filter)

65 Propoxur Organic solvents 150 W Hg lamp Schwack and Kopf12–39 hr (>280 nm, WG295 1992

filter)

66 Aminocarb Cyclohexane 1 kW Xe-Hg lamp Addison et al.N.R. (>300 nm, Corning 1974

0-54 filter)Ethanol UV light (>265 nm) Kumar et al. 197416.4 hr

69 Ethiofencarb Organic solvents 150 W Hg lamp Kopf and Schwack1.3–5.5 hr (>280 nm, WG295 1995

filter)

78 Pirimicarb Organic solvents 150 W Hg lamp Schwack and Kopf60–140 min (>280 nm, WG295 1993

filter)

96 Chlorsulfuron Methanol 20W low-pressure Yang et al. 19996.3 hr Hg lamp

102 T. Katagi




98 Metsulfuron Methanol 20W low-pressure Yang et al. 1999methyl 1.8 hr Hg lamp

99 Tribenuron 2-Propanol 125W medium- Bhattacharjee andmethyl 1.7 hr pressure Hg lamp Dureja 1999

102 Chlorimuron- Hexane 125W Medium- Choudhury andethyl 55.8 min pressure Hg lamp Dureja 1997b

(Pyrex glass)

106 Captan Organic solvents 150W Hg lamp Schwack and37–420 min (>280nm, WG295 Floßer-Muller

filter) 1990

107 Folpet Cyclohexene 150W Hg lamp Schwack 1990N.R. (WG295, 305, 320,

335 & 345 filters)

108 Procymidone Organic solvents 150W Hg lamp Schwack et al.N.R. (>280nm, WG295 1995b

filter)

109 Iprodione Organic solvents 150W Hg lamp Schwack et al.N.R. (>280nm, WG295 1995a

filter)

110 Vinclozolin Organic solvents 150W Hg lamp Schwack et al.N.R. (>280nm, WG295 1995c

filter)

125 Endosulfan Hexane High-pressure Hg Dureja and Muker-N.R. lamp (>300 nm) jee 1982

130 DDT Methyl oleate 150W Hg lamp Schwack 1988N.R. (>280 nm)

134 Methoxychlor Methyl oleate 150W Hg lamp Schwack 1988N.R. (>280 nm)

135 Parathion 12-Hydroxy- UV-B Fluorescent Schwack et al.stearate/TL sunlamp (max, 315 1994

N.R. nm)2-Propanol 1kW Tungsten-N.R. halogen lamp

(>280 nm)Cyclohexene 150W Hg lamp Schwack 1987N.R. (>280 nm, WG295

filter)

138 Fenitrothion Hexane Low-pressure u.v. Greenhalgh and85 min Pen Ray lamp Marshall 1976

(253.7 nm)





Methanol Low-pressure u.v.120 min Pen Ray lamp

(253.7 nm)

141 Iodofenphos Hexane 1 kW Metal halide Walia et al. 1989bN.R. lamp (Applied

Photophysics9500)

145 Chlorpyrifos Hexane High-pressure Hg Walia et al. 1988N.R. lamp

154 Tetrachlovinphos Hexane Medium-pressure Hg Dureja et al. 1987b4.5 hr lamp

170 Phosalone Hexane 125 W High-pressure Walia et al. 1989aN.R. Hg lamp (254–360

nm)

188 Triadimefon Methanol 400 W Medium- Clark et al. 1978N.R. pressure Hg lamp

(borosilicate glass)Hexane, methanol 125 W medium- Nag and Dureja2.5–2.8 hr pressure Hg lamp 1997

192 Hexaconazole Hexane 125 W Hg lamp, Santoro et al. 200023.1 hr Pyrex

193 Penconazole Organic solvents Tungsten halogen Schwack and Hart-5–23 hr lamp (WG305 or mann 1994

WG320 filter)

195 Fluotrimazole Methanol 100 W medium- Clark et al. 1983N.R. pressure Hg lamp

(borosilicate glass)

211 Anilazine Methyl oleate Metal halogen lamp Breithaupt andN.R. (WG295 filter) Schwack 2000Cyclohexene Metal halogen lamp8.0 or 15.0 min (WG295 or WG

320 filter)

220 Fipronil Methanol UV light (max. 300 Hainzl and CasidaN.R. nm, cutoff of 280– 1996

290 nm)

228 Chinomethionat Unsat. fatty acids/ Fluorescent black Nutahara andTL light Murai 1984

N.R.

N.R.: not reported; TL, as a thin layer.

104 T. Katagi

Table 9. Photodegradation of pesticides in plant waxes and cuticles.

Wax (W),Cuticle (C) Light source

No. Pesticide DT50 (wavelength, filter) Reference

66 Aminocarb Nectarine fruits W. 125 W Hg lamp (>290 Pirisi et al. 200159 min nm, borosilicate glass)

68 Methiocarb Nectarine fruits W. 125 W Hg lamp (>290 Pirisi et al. 2001436 min nm, borosilicate glass)

78 Primicarb Nectarine fruits W. 125 W Hg lamp (>290 Pirisi et al. 2001222 min nm, borosilicate glass)Fruits W. 125 W Hg lamp (>290 Pirisi et al. 199835–449 min nm, borosilicate glass)Fruits W. Sunlight15–331 min (May–June, 39 °N)

117 Chlorothalonil Tomato fruits C. Simulated sunlight Jahn et al. 1999N.R. (Suntest CPS+)

129 2,3,7,8-TCDD Laurel cherry W. Sunlight and 300 W Schuler et al.4–9 hr high-pressure Hg 1998

lamps

135 Parathion Fruits C. UV-fluorescent sunlamp Schynowski and2.1–13.5 hr (max, 315 nm) Schwack 1996

143 Fenthion Nectarine fruits W. 125 W Hg lamp (>290 Pirisi et al. 2001204 min nm, borosilicate glass)

Fruits W. Sunlight Cabras et al.2.4–11.9 hr 1997b

N.R., not reported.


Tab

le10

.Ph

otod

egra

datio

nof

pest

icid

esin

and

onso

il(c

lay)

thin

-lay

ersu

rfac

es.

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

12,

4-D

Fou

rso

ils(-

/4.4�

7.6/

-),3

0�

m,3

3�

gcm

−2H

auta

la19

78A

ceto

neso

ln.

450W

Med

ium

-pre

ssur

e3.

3�

7.8

d/N

.R.

Hg

lam

p(P

yrex

glas

s)

4M

ecop

rop

Thr

eeso

ils(1

.4�

2.1/

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,1m

m,0

.125�

gcm

−2R

omer

oet

al.

1998

Met

hano

lso

ln.

Sunl

ight

(Oct

.),

outd

oors

10�

15d/

N.R

.

7T

ricl

opyr

Silt

ycl

aylo

amso

ils,f

ield

(1�

5/-/

-),-

,34�

gcm

−2N

orri

set

al.

1987

Form

ulat

ion

Sunl

ight

75�

81d/

N.R

.

17Pe

rmet

hrin

Dun

kirk

silt

loam

soil

(2.6

/6.0

/-),

0.25

mm

,0.0

2�

gcm

−2H

olm

stea

det

al.

1978

a14

C,

N.R

.Su

nlig

htN

.R.

18T

eflu

thri

nL

oam

soil

(5.0

/6.5

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0g

ha−1

EPA

FIFR

A19

9914

C,

N.R

.X

ela

mp

(4.5

hrd−1

)>3

1d/

N.R

.25

°C19

Cyp

erm

ethr

inT

hree

Japa

nese

soils

(2�

15/5�

6/1�

12),

0.5m

m,1

.1�

gcm

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akah

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85a

14C

,di

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nlig

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106 T. Katagi

Tab

le10

.(C

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.

Soil

prop

erti

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dap

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med

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ide

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ight

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(°C

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ence

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thri

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ndy

loam

soil

(2.2

/5.4

/-),

-,-

EPA

FIFR

A19

9914

C,

N.R

.Su

nlig

ht5.

3d/

97.9

d

21C

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ichv

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MSF

and

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(N.R

.),-

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etal

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87H

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ln.

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(Jun

.)N

.R.

Loa

mso

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C,

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.A

rtif

icia

llig

ht,

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>166

hr/N

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22D

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N.R

.E

PAFI

FRA

1999

14C

,N

.R.

Xe

lam

p,co

ntin

uous

�9

d/10�

11d

24Fe

npro

path

rin

Kod

aira

light

clay

soil

(15/

5.5/

11),

0.5

mm

,1.1�

gcm

−2T

akah

ashi

etal

.19

85b

14C

,di

ethy

let

her

soln

.Su

nlig

ht(S

ept.)

,ou

tdoo

rs1

d/>2

wk

Thr

eeJa

pane

seso

ils(2�

8/5.

7�

6.6/

4�

17),

1m

m,1

0pp

mK

atag

i19

93b

14C

,ac

eton

itrile

soln

.50

0WX

ela

mp

(>29

0nm

,3�

51d/

4�

160

dPy

rex

glas

s),

25°C

27Fe

nval

erat

eT

hree

Japa

nese

soils

(2�

15/5�

6/4�

12),

0.5m

m,0

.6�

gcm

−2M

ikam

iet

al.

1980

14C

,di

ethy

let

her

Sunl

ight

(Sep

t.),

outd

oors

1.8�

18d/

>20

d

28E

sfen

vale

rate

Noi

chi

sand

ycl

aylo

amso

il(1

.4/5

.7/3

.7),

2m

m,1

0pp

mK

atag

i19

9114

C,

1,2-

dich

loro

etha

ne50

0WX

ela

mp

(>30

0nm

,10

0d/

138

dPy

rex

glas

s),

25°C


Tab

le10

.(C

ontin

ued)

.

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

29Fl

ucyt

hrin

ate

Fou

rso

ils(0

.3�

0.5/

6�

8.4/

-),5

mm

,7m

gcm

−2D

urej

aan

dC

hatto

padh

yay

1995

Die

thyl

ethe

rso

ln.

Sunl

ight

(at

300�

400

nm,

1�

2d/

>5d

1.6m

W)

30Fl

uval

inat

eSt

erili

zed

sand

ylo

amso

il(N

.R.)

,3�

5m

m,1

.3�

gcm

−2Q

uins

tad

and

Stai

ger

1984

14C

,N

.R.

Sunl

ight

,ou

tdoo

rs1

d/N

.R.

33Pr

opac

hlor

Thr

eeso

ils(0

.9�

3.5/

7.0�

7.5/

-),1

mm

,5�

20pp

mK

onst

antin

ouet

al.

2001

Met

hano

lso

ln.

Sunl

ight

(Jul

.)14�

32d/

N.R

.

34A

lach

lor

Thr

eeT

aiw

anso

ils(1

.5�

2.6/

5.0�

6.4/

-),-

,100

ppm

Fang

1977

Ace

tone

soln

.Su

nlig

ht(M

ar.�

Apr

.),

>8hr

/N.R

.30�

35°C

35M

etol

achl

orSi

ltlo

amso

il(N

.R.)

,-,5

.15

hgha

−1C

hest

ers

etal

.19

89N

.R.

Sunl

ight

,50�

55°C

8d/

N.R

.

37M

etal

axyl

Fou

rso

ils(0

.2�

4.6/

5�

7/60

%M

WH

C),

5m

m,0

.5�

gcm

−2Su

kul

and

Spite

ller

2001

Aqu

eous

soln

.X

enon

lam

p(>

285

nm)

,25°

C8�

21d/

36�

73d

Tw

oso

ils(0

.86�

1.0/

6.1�

7.4/

-),-

,500

ppm

Saha

and

Suku

l19

97N

.R.

Sunl

ight

7.7

d/N

.R.

40N

iclo

sam

ide

Loa

my

sand

soil

(-/5

.4/d

ryor

75%

FM

C),

2mm

,2.5

ppm

Fran

ket

al.

2002

14C

,ac

eton

itrile

soln

.X

ela

mp

(>29

0nm

,G

raeb

ing

etal

.20

027�

14d/

18d

Her

aeus

sunt

est)

,25

°C

108 T. Katagi

Tab

le10

.(C

ontin

ued)

.

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

42C

arbo

xin

Sche

yern

soil

(N.R

.),2

mm

,5pp

mM

urth

yet

al.

1998

N.R

.X

ela

mp

(>29

0nm

,29

hr/N

.R.

Her

aeus

sunt

est)

,18°

C

47N

apro

pam

ide

Tw

oso

ils(0

.3�

1.7/

7.3�

7.9/

-),-

,-D

onal

dson

and

Mill

er19

96C

H2C

l 2so

ln.

Sunl

ight

3�

7d/

N.R

.

48Fl

oras

ulam

Cal

tin

silt

loam

soil

(2.9

/6.8

/dry

),-,

0.13�

0.32

ppm

Kri

eger

etal

.20

0014

C,

N.R

.Su

nlig

ht(M

ay�

Jun.

)30

d/79

d

52M

onur

onSa

nd/m

ontm

orill

onit

ean

dka

olin

ite

clay

s,-,

-Ji

rkov

sky

etal

.19

97D

ieth

ylet

her

soln

.G

L20

fluo

resc

ent

lam

pN

.R.

(>30

0nm

,gl

ass

filte

r)

53D

iuro

nSa

nd/m

ontm

orill

onit

ean

dka

olin

ite

clay

s,-,

-Ji

rkov

sky

etal

.19

97D

ieth

ylet

her

soln

.G

L20

fluo

resc

ent

lam

p20�

100

hr/N

.R.

(>30

0nm

,gl

ass

filte

r)

54L

inur

onSi

ltlo

amso

il(N

.R.)

,-,-

EPA

OPP

TS

1995

d14

C,

N.R

.X

ela

mp

(Pyr

exgl

ass)

,>1

5d/

N.R

.25

°C56

Isop

rotu

ron

Sand

ylo

amso

il(0

.35/

7.2/

-),-

,2.5

mg/

gof

soil

Kul

shre

stha

and

Muk

erje

e19

86N

.R.

Low

-pre

ssur

eH

gla

mp

N.R

.

58T

hidi

azur

onSp

eyer

soil

2.3

(1.2

/5.5

/1.5

),0.

5m

m,1

.5�

gcm

−2K

lehr

etal

.19

8314

C,

met

hano

lso

ln.

2.5k

WX

ela

mp

(>29

0nm

,0.

5hr

/51

hrW

G29

5+D

uran

filte

r),

<30°

C


Tab

le10

.(C

ontin

ued)

.

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

59D

iflu

benz

uron

N.R

.E

PAO

PPT

S19

97a

14C

,N

.R.

Art

ific

ial

light

11.3

d/3.

7d

65Pr

opox

urT

wo

soils

(1.0�

1.5/

5.3�

7.1/

-),-

,0.4�

0.6

ppm

EPA

OPP

TS

1997

b14

C,

met

hano

lM

ediu

m-p

ress

ure

Hg

lam

p>1

d/�

200d

(>29

0nm

,T

Q15

0fi

lter)

68M

ethi

ocar

bF

our

soils

(4.5�

7.5/

5.8�

6.3/

dry)

,-,-

Goh

rean

dM

iller

1986

CH

2Cl 2

soln

.Su

nlig

ht(J

un.�

Aug

.,7�

14d/

N.R

.K

imax

glas

s),

outd

oors

72C

arbo

fura

nO

rang

egl

ove

soil

(N.R

.),-

,44.

8�

gcm

−2N

igg

etal

.19

842.

5EC

as(4

9)Su

nlig

htN

.R.

81B

enom

ylSi

ltlo

amso

il(N

.R.)

,-,1

lbac

re−1

EPA

OPP

TS

2001

14C

,N

.R.

Sunl

ight

at25

°C<

4d/

N.R

.

82A

sula

mSa

ndy

loam

soil

(N.R

.),-

,-E

PAO

PPT

S19

95a

14C

,N

.R.

Xe

lam

p,25

�28

°C.

1.5

hr/8

3hr

83D

esm

edip

ham

Sand

ylo

amso

il(N

.R.)

,-,-

EPA

OPP

TS

1996

b14

C,

N.R

.X

ela

mp

(3-f

old

irra

diat

ion

110�

160

hr/>

500

hrof

sum

mer

noon

sunl

ight

)

84Ph

enm

edip

ham

Met

apun

toso

il(4

.8/7

.4/-

),-,

-Sc

hafm

eier

etal

.19

98A

ceto

nitr

ileso

ln.

Xe

lam

p12

d/15

d(H

erae

ussu

ntes

t)

110 T. Katagi

Tab

le10

.(C

ontin

ued)

.

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

86B

enth

ioca

rbR

ice-

grow

ing

area

clay

soil

(1.9

5/4.

6/-)

,-,-

Che

ngan

dH

wan

g19

9614

C,

acet

one

soln

.Su

nlig

htN

.R.

(3.5�

4.5

mW

cm−2

)

87B

utyr

ate

Loa

mso

il(N

.R.)

,-,-

EPA

OPP

TS

1993

14C

,N

.R.

Sunl

ight

,ou

tdoo

rs,

25°C

N.R

.

88C

arbo

sulf

anO

rang

egl

ove

soil

(N.R

.),-

,44.

8�

gcm

−2N

igg

etal

.19

842.

5E

CSu

nlig

ht5.

9d/

N.R

89B

enfu

raca

rbSa

ndy

loam

soil

(N.R

.),-

,125�

gcm

−2D

urej

aet

al.

1990

N.R

.L

ow-p

ress

ure

Hg

lam

pN

.R.

(254

nm)

90M

olin

ate

Thr

eeso

ils(0

.9�

3.5/

7.0�

7.5/

-),1

mm

,5�

20pp

mK

onst

antin

ouet

al.

2001

Met

hano

lso

ln.

Sunl

ight

(Jul

.)13�

34d/

N.R

.

92T

hiop

hana

te-

Sand

ylo

amso

il(1

.7/7

.4/-

),-,

-E

PAO

PPT

S20

01m

ethy

l14

C,

N.R

.Su

nlig

ht2.

9�

5.5

d/10�

19d

94M

aneb

Del

awar

eso

il(N

.R.)

,-,2

2.4�

gcm

−2R

hode

s19

7714

C,

aque

ous

soln

.Su

nlig

ht(s

prin

g)<1

wk/

N.R

.

96C

hlor

sulf

uron

Nor

asi

lty

clay

loam

soil

(2/8

.0/-

),1

mm

,1.7�

gcm

−2St

rek

1998

14C

,pH

7bu

ffer

soln

.X

ela

mp

(>29

0nm

),25

°C50

d/13

0d


Tab

le10

.(C

ontin

ued)

.

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

99T

ribe

nuro

n-A

lluvi

al(1

.2/7

.5/-

),2

mm

,-B

hatta

char

jee

and

Dur

eja

2002

met

hyl

14C

,ac

eton

eso

ln.

Sunl

ight

(May

)or

u.v.

11d

or11

hr/N

.R.

light

(max

.25

4nm

)

100

Tri

asul

furo

nT

wo

soils

(0.9�

2.3/

7.0�

7.1/

dry)

,1m

m,6�

7pp

mA

lban

iset

al.

2002

Met

hano

lso

ln.

1.1k

WX

ela

mp

(Sun

test

6�

15hr

/26�

198

hrC

PS+,

>300

nm),

20°C

102

Chl

orim

uron

-T

hree

soils

(0.7�

1.2/

6.2�

8.1/

-),2

mm

,50

ppm

Cho

udhu

ryan

dD

urej

a199

7aet

hyl

N.R

.Su

nlig

ht(A

pr.�

May

),11�

21d/

N.R

.30�

35°C

103

Rim

sulf

uron

Sass

afra

ssa

ndy

loam

soil

(1.0

/6.3

/-),

1mm

,0.5�

gcm

−2Sc

hnei

ders

etal

.19

9314

C,

acet

onitr

ileso

ln.

Sunl

ight

(Jun

.�

Jul.)

,25

°C11

d/11

d

105

Thi

fens

ulfu

ron-

Tw

oso

ils(0

.9�

2.3/

7.0�

7.1/

dry)

,1m

m,6�

7pp

mA

lban

iset

al.

2002

met

hyl

Met

hano

lso

ln.

1.1k

WX

ela

mp

(Sun

test

�7

hr/2

4�

34hr

CPS

+,>3

00nm

),20

°C10

6C

apta

nSa

ndy

loam

soil

(-/-

/moi

st),

-,-

EPA

OPP

TS

1999

b14

C,

N.R

.Su

nlig

ht5�

15d/

10�

21d

109

Ipro

dion

eSa

ndy

loam

soil

(N.R

.),-

,-E

PAO

PPT

S19

98e

14C

,N

.R.

Xe

lam

p7�

14d/

14�

21d

111

Fam

oxad

one

N.R

.Je

rnbe

rgan

dL

ee19

99N

.R.

N.R

.12

d/28

d

112 T. Katagi

Tab

le10

.(C

ontin

ued)

.

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

118

Dic

amba

Lap

onit

e,-,

-A

guer

etal

.20

00N

.R.

125W

high

-pre

ssur

eH

gla

mp

N.R

.(>

290

nm,

2.2-

cmw

ater

filte

r)

119

Chl

oram

ben

Pen

nsyl

vani

alo

amso

il(2

.0/5

–6/-

),2

mm

,3pp

mM

isra

etal

.19

9714

C,

acet

onitr

ileX

enon

lam

p(H

erae

us29�

109d

/2�

500d

Sunt

est

CPS

),25

°C12

1Pe

ntac

hlor

o-T

hree

soils

(0.3�

1.5/

4.4�

7.7/

dry)

,0.0

8m

m,1

000

ppm

Liu

etal

.20

02ph

enol

Hex

ane

soln

.30

0Wm

ediu

m-p

ress

ure

20�

60m

in/N

.R.

Hg

lam

p(w

ater

filte

r)

122

Ald

rin

UK

and

Ger

man

soils

(2�

3.5/

7.4�

8.1/

-),-

,�

30�

gcm

−2K

lein

etal

.19

7314

C,

EC

form

ulat

ion

Sunl

ight

(Apr

il),

outd

oors

N.R

.

123

Die

ldri

nJa

pane

seso

ils(N

.R.)

,-,-

Suzu

kian

dY

amam

oto

1974

Form

ulat

ion

Sunl

ight

,fi

led

N.R

.

130

DD

TC

lay

loam

soil

(2.5

/7.5

/fie

ld),

-,-

Zay

edet

al.

1994

14C

,N

.R.

Sunl

ight

,ou

tdoo

rs55

d/N

.R.

133

Dic

ofol

Silt

loam

soil

(N.R

.),-

,-E

PAO

PPT

S19

98d

14C

,N

.R.

Art

ific

ial

light

21�

30d/

N.R

.


Tab

le10

.(C

ontin

ued)

.

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

136

Para

thio

n-O

rthi

cliv

isol

(1.9

/7.2

/-),

0.1

mm

,-K

rom

eret

al.

1999

met

hyl

Met

hano

lso

ln.

Xe

lam

pin

Sunt

est

CPS

+�

1d/

>1d

20.5

°CSa

ndy

loam

soil

(N.R

.),-

,>14�

gcm

−2E

PAO

PPT

S19

99e

14C

,N

.R.

Sunl

ight

(Jul

y),

outd

oors

61d/

106

dca

.25

°C13

7C

yano

phos

Tw

oJa

pane

seso

ils(3�

19/5

.2�

6.4/

5�

12),

0.5

mm

,-M

ikam

iet

al.

1976

14C

,N

.R.

Sunl

ight

(Sep

t.�

Oct

.),

2d/

>12

dou

tdoo

rs

138

Feni

trot

hion

Tw

oJa

pane

seso

ils(2

.5�

19/-

/5�

12),

50�

m,1

0�

gcm

−2M

ikam

iet

al.

1985

b14

C,

CH

Cl 3

soln

.Su

nlig

ht(J

un.)

,ou

tdoo

rs�

1d/

>12

d

140

Bro

mop

hos

Spey

erst

anda

rdso

il2.

2(2

.6/5

.8/1

2),-

,180

ppm

Allm

aier

etal

.19

84M

etha

nol

soln

.D

aylig

ht+

UV

-A&

-Bla

mps

Allm

aier

and

Schm

id19

8548

d/80

d(>

290

nm),

25°C

141

Iodo

fenp

hos

Fin

ely

pow

dere

dso

il(N

.R.)

,-,-

Wal

iaet

al.

1989

bA

ceto

neso

ln.

1kW

met

alha

lide

lam

pA

llmai

eran

dSc

hmid

1985

N.R

.(A

pplie

dPh

otop

hysi

cs95

00)

Spey

erst

anda

rdso

il2.

22(2

.6/5

.8/1

2),-

,180

ppm

Allm

aier

etal

.19

84M

etha

nol

soln

.D

aylig

ht+

UV

-A&

-Bla

mps

71d/

85d

(>29

0nm

),25

°C14

2T

olcl

ofos

-F

our

Japa

nese

soils

(3�

15/5�

7/5�

16)

,50�

m,7�

gcm

−2M

ikam

iet

al.

1984

bm

ethy

l14

C,

CH

Cl 3

soln

.Su

nlig

ht(M

ay�

Jun.

),1�

2d/

2�

>15

dou

tdoo

rs

114 T. Katagi

Tab

le10

.(C

ontin

ued)

.

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

143

Fent

hion

Fiv

eU

.S.s

oils

(0.8�

6.3/

4.5�

7.5/

-),-

,50�

200

ppm

Goh

rean

dM

iller

1986

CH

2Cl 2

soln

.Su

nlig

ht(M

ay�

Aug

.),

N.R

.ou

tdoo

rs

144

Dia

zino

nSw

itze

rlan

dsi

lty

loam

(3.6

/6.1

/dry

or12

%),

-,10

ppm

Bur

khar

dan

dG

uth

1979

14C

,N

.R.

Xe

lam

p(>

290

nm,

u.v.

filte

r<1

d/<1

d+

IRre

flec

ting

glas

s),�

45°C

Sand

ylo

amso

il(N

.R.)

,-,-

EPA

OPP

TS

2000

14C

,N

.R.

Sunl

ight

20hr

/14

.7d

145

Chl

orpy

rifo

sF

inel

ypo

wde

red

soil

(N.R

.),2

mm

,-W

alia

etal

.19

880.

5%ac

eton

eso

ln.

Low

-pre

ssur

eH

gla

mp

17.3

d/N

.R.

(254

nm)

148

Qui

nalp

hos

Fou

rIn

dian

soils

(-/5

.6�

8.4/

-),5

0�

m,7�

gcm

−2D

urej

aet

al.

1988

Chl

orof

orm

soln

.Su

nlig

ht(M

ay�

Jun.

)2�

5d/

14�

>25

d

154

Tet

rach

lo-

Eas

tA

nglia

med

ium

loam

(-/8

.0/1

9),-

,13

ppm

Bey

non

and

Wri

ght

1969

vinp

hos

14C

,ac

eton

eso

ln.

Subd

ued

dayl

ight

4�

5d/

N.R

.Sa

ndy

loam

soil

(0.3

5/7.

2/-)

,-,2

.5m

g/g

ofso

ilD

urej

aet

al.

1987

bN

.R.

Med

ium

-pre

ssur

eH

gla

mp

N.R

./>10

d

156

Mon

ocro

toph

osSt

erili

zed

sand

ylo

am(1

.3/6

.4/-

)so

il,<1

mm

,5pp

mL

eeet

al.

1989

14C

,m

etha

nol

soln

.Su

nlig

ht(J

ul.�

Aug

.)3

d/30

d


Tab

le10

.(C

ontin

ued)

.

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

157

Dic

roto

phos

Fou

rU

.S.s

oils

(-/5

.7�

6.7/

-),<

1m

m,2

5pp

mL

eeet

al.

1989

14C

,ac

eton

eso

ln.

Fluo

resc

ent

lam

psN

.R.

(GE

P40B

L,

BL

B),

35°C

160

Prof

enof

osSw

itze

rlan

dsi

lty

loam

(3.6

/6.1

/dry

or12

%),

-,10

ppm

Bur

khar

dan

dG

uth

1979

14C

,N

.R.

Xe

lam

p(>

290

nm,

u.v.

filte

r<1

d/�

1d

+IR

refl

ectin

ggl

ass)

,�

45°C

162

Phor

ate

Pla

nosi

ltlo

amso

il(N

.R.)

,fie

ld,1

12�

gcm

−2L

icht

enst

ein

etal

.19

73Fo

rmul

atio

nSu

nlig

ht(M

ay),

fiel

d<1

wk/

N.R

.

163

Dis

ulfo

ton

Sand

ylo

amso

il(N

.R.)

,-,-

EPA

OPP

TS

1999

d14

C,

N.R

.Su

nlig

ht2.

4d/

N.R

.F

our

soils

(4.5�

7.5/

0.8�

6.3/

dry)

,-,-

Goh

rean

dM

iller

1986

Dic

hlor

omet

hane

soln

.Su

nlig

ht(A

ug.

orO

ct.,

�3

d/>5

dK

imax

glas

s),

outd

oors

164

Ben

sulid

eSo

rent

olo

amso

il(N

.R.)

,-,-

EPA

OPP

TS

1999

a14

C,

N.R

.X

ela

mp

90d/

N.R

.

168

Phen

thoa

teT

wo

Japa

nese

soils

(3�

19/5�

6/5�

12),

0.5

mm

,10�

gcm

−2M

ikam

iet

al.

1977

b14

C,

diet

hyl

ethe

rso

ln.

Sunl

ight

(Sep

t.�

Oct

.),

3d/

>6d

outd

oors

169

Azi

npho

s-Sa

ndy

loam

soil

(-/5

.1/-

),-,

-E

PAO

PPT

S19

98a

met

hyl

14C

,N

.R.

Sunl

ight

(Apr

il)18

0d/

N.R

.

116 T. Katagi

Tab

le10

.(C

ontin

ued)

.

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

170

Phos

alon

eF

inel

ypo

wde

red

soil

(N.R

.),-

,-W

alia

etal

.19

89a

Ace

tone

soln

.1k

Whi

gh-p

ress

ure

met

al-

5d/

>15

dha

lide

lam

p(>

300

nm)

171

Met

hida

thio

nSw

itze

rlan

dsi

lty

loam

(3.6

/6.1

/dry

or12

%),

-,10

ppm

Bur

khar

dan

dG

uth

1979

14C

,N

.R.

Xe

lam

p(>

290

nm,

u.v.

filte

r<1

d/<1

d+

IRre

flec

ting

glas

s),�

45°C

175

Isof

enph

osSa

ndy

loam

soil

(0.3

5/7.

2/-)

,-,1

25�

gcm

−2D

urej

aet

al.

1989

N.R

.L

ow-p

ress

ure

Hg

lam

pN

.R.

178

Dita

limfo

sSp

eyer

stan

dard

soil

2.2

(2.6

/5.8

/12)

,-,3

10pp

mA

llmai

eret

al.

1984

Met

hano

lso

ln.

Day

light

+U

V-A

&-B

�18

d/N

.R.

lam

ps(>

290

nm),

25°C

180

Cya

nofe

npho

sT

wo

Japa

nese

soils

(3�

19/5

.2�

6.4/

5�

12),

0.5

mm

,-M

ikam

iet

al.

1976

14C

,N

.R.

Sunl

ight

(Sep

t.�

Oct

.),

2d/

>12

dou

tdoo

rs

183

Dio

xabe

nzof

osT

wo

Japa

nese

soils

(3�

19/5�

6/5�

12),

0.5

mm

,10�

gcm

−2M

ikam

iet

al.

1977

b14

C,

diet

hyl

ethe

rso

ln.

Sunl

ight

(Sep

t.�

Oct

.),

<1d/

>6d

outd

oors

184

Eth

ion

Ster

ilize

dsa

ndy

loam

soil

(N.R

.),-

,8.6

ppm

EPA

OPP

TS

1995

c14

C,

N.R

.Su

nlig

ht61

.6d/

175.

9d

185

Atr

azin

eE

ight

soils

(0.9�

1.6/

7.8�

8.0/

vari

ous)

,0.2�

0.5

mm

,-G

ong

etal

.20

01M

etha

nol

soln

.1k

Wm

ediu

m-p

ress

ure

4�

8m

in/N

.R.

Hg

lam

p


Tab

le10

.(C

ontin

ued)

.

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

188

Tri

adim

efon

Tw

oso

ils(0

.4�

0.8/

5.3�

7.4/

-),2

mm

,31.

8�

gcm

−2N

agan

dD

urej

a19

96A

ceto

neso

ln.

u.v.

light

(254

nm)

or9.

5�

22hr

/N.R

.su

nlig

ht(S

ept.)

Sche

yern

soil

(N.R

.),2

mm

,5pp

mM

urth

yet

al.

1998

N.R

.X

ela

mp

(>29

0nm

,16

6hr

/N.R

.H

erae

ussu

ntes

t),

18°C

191

Prop

icon

azol

eSa

ndy

loam

soil

(N.R

.),3

.5m

m,0

.3�

gcm

−2D

urej

aet

al.

1987

aA

ceto

neso

ln.

Sunl

ight

12d/

>26

d

196

Am

itrol

eSa

ndy

loam

soil

(N.R

.),-

,-E

PAO

PPT

S19

96a

14C

,N

.R.

Xe

lam

p,25

°C<7

3d/

N.R

.

197

Ter

baci

lD

rum

mer

silt

ycl

aylo

amso

il(N

.R.)

,-,1

.2lb

acre

−1E

PAO

PPT

S19

98h

14C

,N

.R.

Xe

lam

p,25

°C61

d/N

.R.

200

Ben

tazo

nM

ontc

alm

sand

ylo

amso

il(N

.R.)

,0.5

mm

,100�

gcm

−2N

illes

and

Zab

ik19

7514

C,

CH

2Cl 2

soln

.R

PRu.

v.lig

ht(3

00&

>5d/

N.R

.35

0nm

)

201

Met

ribu

zin

Sand

ylo

amso

il(N

.R.)

,-,-

EPA

OPP

TS

1998

g14

C,

N.R

.Su

nlig

ht,

outd

oors

,31

°C2.

5d/

N./R

.

118 T. Katagi

Tab

le10

.(C

ontin

ued)

.

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

214

Nor

flur

azon

Rom

elo

amso

il(2

.0/6

.2/-

),-,

0.6�

gcm

−2Sc

hroe

der

Kvi

enan

dB

anks

1985

N.R

.Su

nlig

ht,

outd

oors

,25�

70°C

8d/

N.R

.

220

Fipr

onil

Nor

ther

nSe

nega

lso

il(0

.3/7

.6/-

),fi

eld,

0.05�

0.1�

gcm

−2Fe

net

etal

.20

01Fo

rmul

atio

nSu

nlig

ht,

fiel

d4–

5d/

N.R

.T

wo

Nig

erso

ils(0

.1�

0.3/

5.3�

5.8/

-),-

,0.0

8�

gcm

−2B

obe

etal

.19

98a

Form

ulat

ion

Sunl

ight

(Sep

t.�

Oct

.),

fiel

d1.

5d/

N.R

.B

aniz

oum

bou

soil

(6.5

/8.3

/dry

)so

ils,-

,2.5

ppm

Bob

eet

al.

1998

bM

etha

nol

soln

.1.

8kW

Xe

lam

p(S

unte

st,

6–9

d/N

.R.

>290

nm,

u.v.

filte

r)

221

DT

PT

wo

Japa

nese

soils

(3�

9/5.

6�

5.8/

-),0

.5m

m,3

.8�

gcm

−2Y

amao

kaet

al.

1988

14C

,aq

ueou

sso

ln.

Sunl

ight

(May�

Jun.

)31�

34d/

N.R

.

232

Tri

flur

alin

Sand

ylo

amso

il(N

.R.)

,-,-

EPA

OPP

TS

1996

c14

C,

N.R

.N

.R.

41d/

66d

234

But

ralin

Sand

ylo

amso

il(N

.R.)

,-,3

74pp

mE

PAO

PPT

S19

98b

14C

,N

.R.

Sunl

ight

99.6

d/11

2.7

d

235

Ory

zalin

Sand

ylo

amso

il(N

.R.)

,-,-

EPA

OPP

TS

1994

14C

,N

.R.

Xe

lam

p22

.4hr

/N.R

.


Table10.(Continued).

Soil

prop

erti

esan

dap

plic

atio

nra

tea)

App

licat

ion

med

ium

b)L

ight

sour

ce(w

avel

engt

hor

#Pe

stic

ide

DT

50(l

ight

/dar

k)se

ason

,fi

lter)

,te

mp

(°C

)R

efer

ence

236

Fluc

hlor

alin

Mon

tcal

msa

ndy

loam

soil

(N.R

.),0

.5m

m,1

00�

gcm

−2N

illes

and

Zab

ik19

7414

C,

CH

2Cl 2

soln

.R

PRu.

v.lig

ht(3

00&

N.R

.35

0nm

)

237

Eth

alfl

ural

inSa

ndy

loam

soil

(N.R

.),-

,-E

PAO

PPT

S19

95b

14C

,N

.R.

N.R

.14

.2d/

N.R

.

238

Pend

imet

halin

Kal

yani

allu

vial

soil

(1.7

/7.2

/dry

),2m

m,2

8�g/

gof

soil

Had

ler

etal

.19

89H

exan

eso

ln.

Sunl

ight

N.R

.N

ewD

elhi

sand

ylo

amso

il(3

.6/6

.1/-

),50�

m,7�

gcm

−2D

urej

aan

dW

alia

1989

Met

hano

lso

ln.

Low

-pre

ssur

eH

gla

mp

N.R

.(2

54nm

)

240

Proc

hlor

azT

wo

soils

(1.0�

1.5/

5.3�

7.1/

-),-

,0.4�

0.6

ppm

Hol

lrig

l-R

osta

etal

.19

9914

C,

met

hano

lM

ediu

m-p

ress

ure

Hg

lam

p>1

d/�

200d

(>29

0nm

,T

Q15

0fi

lter)

a Soil

prop

ertie

san

dap

plic

atio

nra

tear

elis

ted

inth

efo

llow

ing

orde

ras

bold

face

:soi

lnam

e(o

rgan

icm

atte

rco

nten

t%/p

H/m

oist

ure

cont

ent%

),so

illa

yer

thic

knes

s,ap

plic

atio

nra

te.

b Non

radi

olab

eled

pest

icid

ew

hen

unsp

ecif

ied.

“-”

orN

.R.:

not

repo

rted

.M

HW

C,

max

imum

wat

erho

ldin

gca

paci

ty;

FMC

,fi

eld

moi

stur

eco

nten

t

120 T. Katagi

Tab

le11

.Su

rfac

ede

grad

atio

nof

pest

icid

esin

folia

ror

topi

cal

appl

icat

ion.

Plan

tsp

ecie

sA

pplic

atio

nm

ediu

mN

o.Pe

stic

ide

DT

50L

ight

sour

ce(s

easo

n),

cond

ition

sR

efer

ence

s

12,

4-D

Cor

nle

af14

C,

0.25

%ox

ysor

bic

surf

acta

ntV

enka

tesh

and

Har

riso

n19

9914

.6hr

Fluo

resc

ent

lam

ps

13Ph

enot

hrin

Bea

n&

rice

leaf

14C

,m

etha

nol

soln

.N

ambu

etal

.19

80<1

dSu

nlig

ht(N

ov.)

,gr

eenh

ouse

19C

yper

met

hrin

Cot

ton

&be

anle

af14

C,

diet

hyl

ethe

rso

ln.

Col

eet

al.

1982

2–4

dSu

nlig

ht(J

uly–

Sept

.),

outd

oors

22D

elta

met

hrin

Cot

ton

leaf

14C

,di

ethy

let

her

soln

.R

uzo

and

Cas

ida

1979

1.1

wk

Sunl

ight

,gr

eenh

ouse

Bea

nle

af14

C,

diet

hyl

ethe

rso

ln.

Col

eet

al.

1982

�4

dSu

nlig

ht(J

uly–

Sept

.),

outd

oors

Pota

tole

af2.

5%E

CM

agui

re19

901–

2d

Sunl

ight

(sum

mer

),fi

eld

24Fe

npro

path

rin

Man

dari

nor

ange

leaf

14C

,m

etha

nol

soln

.T

akah

ashi

etal

.19

85b

4d

Sunl

ight

(Sep

t.),

gree

nhou

se

27Fe

nval

erat

eK

idne

ybe

anle

af14

C,

met

hano

lso

ln.

Ohk

awa

etal

.19

8014

dSu

nlig

ht(O

ct.)

,gr

eenh

ouse

Spri

ngw

heat

leaf

14C

,0.

1%E

CL

eeet

al.

1988

2–4

dSu

nlig

ht(S

ept.

–Dec

.),

outd

oors

Cot

ton

leaf

2.4

lb/g

alE

Cfo

rmul

atio

nH

olm

stea

det

al.

1978

b8

dSu

nlig

ht(m

id-J

uly)

29Fl

ucyt

hrin

ate

Fren

chbe

anle

afM

etha

nol

soln

.C

hatto

padh

yaya

and

Dur

eja

1991

3d

Sunl

ight

(Apr

.),

gree

nhou

se


Tab

le11

.(C

ontin

ued)

.

Plan

tsp

ecie

sA

pplic

atio

nm

ediu

mN

o.Pe

stic

ide

DT

50L

ight

sour

ce(s

easo

n),

cond

ition

sR

efer

ence

s

39Fl

utol

anil

Cuc

umbe

rle

af14

C,

diet

hyl

ethe

rso

ln.

Uch

ida

etal

.19

8329

.3d

Sunl

ight

,gr

eenh

ouse

42C

arbo

xin

Bea

nle

afSu

spen

sion

Buc

hena

uer

1975

<10

hrSu

nlig

ht

45Pr

opyz

amid

eA

lfal

fale

af14

C,

acet

one

soln

.Y

ihan

dSw

ithen

bank

1971

63.8

dSu

nlig

ht,

fiel

d

57D

iafe

nthi

uron

Chi

nese

cabb

age

leaf

25E

CK

eum

etal

.20

024

dSu

nlig

ht,

fiel

dC

otto

nle

afSC

400

form

ulat

ion

Dra

bek

etal

.19

92<3

hrSu

nlig

ht,

fiel

d

59D

iflu

benz

uron

Cot

ton

leaf

14C

,25

%W

PB

ull

and

Ivie

1976

31.9

dSu

nlig

ht(s

umm

er),

outd

oors

Con

ifer

pine

need

le45

%oi

lfo

rmul

atio

nR

odri

guez

etal

.20

012–

3w

kSu

nlig

ht(A

ug.–

Oct

.),

fiel

d

61M

etol

carb

Bea

nle

af14

C,

met

hano

lso

ln.

Ohk

awa

etal

.19

74a

<1d

Sunl

ight

,gr

eenh

ouse

62Fe

nobu

carb

Ric

ele

af14

C,

met

hano

l-w

ater

(1/3

)so

ln.

Oga

wa

etal

.19

76N

.R.

Sunl

ight

,gr

eenh

ouse

63X

ylyl

carb

Bea

nle

af14

C,

met

hano

lso

ln.

Ohk

awa

etal

.19

74a

<1d

Sunl

ight

,gr

eenh

ouse

64T

rim

etha

carb

Pint

obe

anle

af14

C,

etha

nol

soln

.Sl

ade

and

Cas

ida

1970

N.R

.Su

nlig

ht(J

une–

July

),ou

tdoo

rs

122 T. Katagi

Tab

le11

.(C

ontin

ued)

.

Plan

tsp

ecie

sA

pplic

atio

nm

ediu

mN

o.Pe

stic

ide

DT

50L

ight

sour

ce(s

easo

n),

cond

ition

sR

efer

ence

s

65Pr

opox

urG

arde

nsn

apbe

anle

af14

C,

etha

nol

soln

.A

bdel

-Wah

abet

al.

1966

8hr

Sunl

ight

(Aug

.–Se

pt.)

,ou

tdoo

rs

66A

min

ocar

bG

arde

nsn

apbe

anle

af14

C,

etha

nol

soln

.A

bdel

-Wah

aban

dC

asid

a19

674

hrSu

nlig

ht(A

ug.–

Sept

.),

outd

oors

67M

exac

arba

teG

arde

nsn

apbe

anle

af3 H

,14

C;

etha

nol

soln

.A

bdel

-Wah

aban

dC

asid

a19

672–

3hr

Sunl

ight

(Aug

.–Se

pt.)

,ou

tdoo

rs

68M

ethi

ocar

bG

arde

nsn

apbe

anle

af14

C,

etha

nol

soln

.A

bdel

-Wah

abet

al.

1966

>3d

Sunl

ight

(Aug

.–Se

pt.)

,ou

tdoo

rs

71C

arba

ryl

Gar

den

snap

bean

leaf

14C

,et

hano

lso

ln.

Abd

el-W

ahab

etal

.19

662.

8d

Sunl

ight

(Aug

.–Se

pt.)

,ou

tdoo

rs

72C

arbo

fura

nSt

raw

berr

y43

.8%

FLA

rche

ret

al.

1977

1–3

dSu

nlig

ht,

fiel

d

74O

xam

ylT

obac

cole

af14

C,

0.2%

Tw

een

20aq

ueou

sso

ln.

Har

vey

etal

.19

78�

15d

Plan

tgr

owth

cham

ber

78Pi

rim

icar

bL

ettu

cele

af25

%liq

uid

form

ulat

ion

Cab

ras

etal

.19

90�

2d

Sunl

ight

(May

),fi

eld

81B

enom

ylPi

nto

bean

leaf

14C

,52

%W

PB

aude

etal

.19

73N

.R.

Sunl

ight

,gr

eenh

ouse

85Fe

noth

ioca

rbM

anda

rin

oran

ge14

C,

30%

EC

Una

iet

al.

1986

1.6–

12d

Sunl

ight

(Sep

t.),

gree

nhou

se

88C

arbo

sulf

anV

alen

cia

oran

ge14

C,

EC

Cla

yan

dFu

kuto

1984

3–6

dSu

nlig

ht(s

umm

er),

fiel

d


Tab

le11

.(C

ontin

ued)

.

Plan

tsp

ecie

sA

pplic

atio

nm

ediu

mN

o.Pe

stic

ide

DT

50L

ight

sour

ce(s

easo

n),

cond

ition

sR

efer

ence

s

89B

enfu

raca

rbC

otto

nle

af14

C,

acet

one-

wat

er(1

/1)

Tan

aka

etal

.19

85N

.R.

Sunl

ight

,gr

eenh

ouse

92T

hiop

hana

te-m

ethy

lC

otto

nle

af70

%W

PB

uche

naue

ret

al.

1973

N.R

.Su

nlig

ht,

outd

oors

App

letr

eele

af14

C,

70%

WP

Soed

aet

al.

1972

15d

Sunl

ight

(May

–Aug

.)

93M

BC

Cor

nle

af3 H

,14

C;

10m

MH

Cl

in50

%et

hano

l.Fl

eeke

ran

dL

acy

1977

N.R

.Su

nlig

ht(J

uly)

,ou

tdoo

rs

95E

TU

Tom

ato

leaf

14C

,80

%W

PR

hode

s19

772.

1d

Sunl

ight

,ou

tdoo

rs

99T

ribe

nuro

nm

ethy

lW

heat

leaf

Ace

tone

soln

.B

hatta

char

jee

and

Dur

eja

2002

N.R

.Su

nlig

ht,

gree

nhou

se

104

Thi

fen-

sulf

uron

Soyb

ean

leaf

14C

,aq

ueou

sso

ln.±

surf

acta

ntB

row

net

al.

1993

4–20

dSu

nlig

ht,

gree

nhou

se

108

Proc

ymid

one

Bea

n&

cucu

mbe

rle

af14

C,

diet

hyl

ethe

rso

ln.

Mik

ami

etal

.19

84a

2–3

wk

Sunl

ight

,gr

eenh

ouse

112

Met

hazo

leC

otto

nle

af14

C,

aque

ous

soln

.D

orou

ghet

al.

1973

<1d

Sunl

ight

(Jun

e),

outd

oors

122

Ald

rin

App

letr

eele

afA

ldre

x30

Har

riso

net

al.

1967

<1w

kSu

nlig

ht(J

une)

,fi

eld

123

Die

ldri

nA

pple

tree

leaf

50%

disp

ersi

ble

pow

der

Har

riso

net

al.

1967

<1w

kSu

nlig

ht(J

une)

,fi

eld

124 T. Katagi

Tab

le11

.(C

ontin

ued)

.

Plan

tsp

ecie

sA

pplic

atio

nm

ediu

mN

o.Pe

stic

ide

DT

50L

ight

sour

ce(s

easo

n),

cond

ition

sR

efer

ence

s

125

End

osul

fan

App

letr

eele

af20

%co

ncen

trat

eH

arri

son

etal

.19

67<1

wk

Sunl

ight

(Jun

e),

fiel

dC

otto

nle

af0.

1%he

xane

soln

.D

urej

aan

dM

uker

jee

1982

N.R

.Su

nlig

ht(J

une)

126

End

rin

App

letr

eele

afE

ndre

x20

Har

riso

net

al.

1967

<1w

kSu

nlig

ht(J

une)

,fi

eld

130

DD

TA

pple

tree

leaf

25%

EC

or50

%di

sper

sibl

epo

wde

rH

arri

son

etal

.19

67<1

–2w

kSu

nlig

ht(J

une)

,fi

eld

135

Para

thio

nG

arde

nbe

anle

af0.

2%T

rito

nX

-155

+B

-195

6(1/

1)E

l-R

efai

and

Hop

kins

1966

�1

dFl

uore

scen

tla

mps

,gr

eenh

ouse

Cot

ton

leaf

14C

,m

etha

nol

soln

.Jo

iner

and

Bae

tcke

1973

N.R

.Su

nlig

ht,

fiel

d

137

Cya

noph

osK

idne

ybe

anle

af14

C,

benz

ene-

hexa

ne(4

/1)

+su

rfac

tant

Chi

baet

al.

1976

0.54

dSu

nlig

ht,

gree

nhou

se

138

Feni

trot

hion

App

letr

eele

af0.

5%em

ulsi

onH

osok

awa

and

Miy

amot

o19

741.

2d

Sunl

ight

(Oct

.–N

ov.)

Bea

nle

af14

C,

etha

nol

soln

.O

hkaw

aet

al.

1974

b<1

dSu

nlig

ht(N

ov.)

,ou

tdoo

rs

140

Bro

mop

hos

Tom

ato

leaf

32P

&3 T

,em

ulsi

onSt

iasn

iet

al.

1969

<8

hr40

0W

dayl

ight

lam

psin

cham

ber

143

Fent

hion

Ora

nge

frui

t,pe

elC

omm

erci

alfo

rmul

atio

n(2

4.2%

a.i.)

Min

elli

etal

.19

963.

9–4.

8d

Sunl

ight

(Apr

.),

outd

oors

Cor

nle

af50

%E

CL

euch

and

Bow

man

1968

�1

dSu

nlig

ht,

fiel

d


Tab

le11

.(C

ontin

ued)

.

Plan

tsp

ecie

sA

pplic

atio

nm

ediu

mN

o.Pe

stic

ide

DT

50L

ight

sour

ce(s

easo

n),

cond

ition

sR

efer

ence

s

145

Chl

orpy

rifo

sSo

ftsh

ield

fern

leaf

14C

,0.

1%ac

eton

eso

ln.

Wal

iaet

al.

1988

54.3

dSo

lar

sim

ulat

or(1

kWm

etal

-hal

ide

lam

p)

151

Isox

athi

onC

abba

gele

af14

C,

0.03

%T

wee

n20

aque

ous

soln

.A

ndo

etal

.19

752–

3d

Sunl

ight

,gr

eenh

ouse

152

Phox

imT

omat

ole

af5%

form

ulat

ion

Mak

ary

etal

.19

81�

1d

Sunl

ight

,fi

eld

Cor

nle

afE

CB

owm

anan

dL

euck

1971

<1d

Sunl

ight

,fi

eld

154

Tet

rach

lo-v

inph

osA

pple

tree

leaf

14C

,ac

eton

eso

ln.

Bey

non

and

Wri

ght

1969

�2

dSu

nlig

ht,

gree

nhou

seB

ean

leaf

Ace

tone

soln

.D

urej

aet

al.

1987

b6

dSu

nlig

ht

156

Mon

ocro

to-p

hos

Cot

ton

leaf

32P,

aque

ous

soln

.L

indq

uist

and

Bul

l19

67<2

dSu

nlig

ht,

gree

nhou

seB

ush

appl

efr

uit

14C

,ac

eton

eso

ln.

Bey

non

and

Wri

ght

1972

N.R

.Su

nlig

ht,

gree

nhou

se

157

Dic

roto

phos

Cot

ton

leaf

32P,

aque

ous

soln

.B

ull

and

Lin

dqui

st19

64<1

dL

abor

ator

y

158

Phos

pham

i-do

nC

otto

nle

af32

P,aq

ueou

sso

ln.

Bul

let

al.

1967

<1d

Sunl

ight

,gr

eenh

ouse

161

Sulp

rofo

sC

otto

nle

af14

C,

50%

EC

Ivie

and

Bul

l19

761

dSu

nlig

ht(A

ug.)

,ou

tdoo

rs

126 T. Katagi

Tab

le11

.(C

ontin

ued)

.

Plan

tsp

ecie

sA

pplic

atio

nm

ediu

mN

o.Pe

stic

ide

DT

50L

ight

sour

ce(s

easo

n),

cond

ition

sR

efer

ence

s

165

Dim

etho

ate

Cor

nle

af32

P,em

ulsi

onD

aute

rman

etal

.19

60N

.R.

Sunl

ight

,gr

eenh

ouse

Bea

nle

af14

C&

32P,

aque

ous

soln

.L

ucie

ran

dM

enze

r19

68�

4d

Sunl

ight

(Apr

.),

gree

nhou

seB

ean

leaf

14C

,aq

ueou

sso

ln.

Luc

ier

and

Men

zer

1970

1.7

dSu

nlig

ht,

gree

nhou

se

166

Form

othi

onB

ean

leaf

14C

,20

%E

CSa

uer

1972

1.2

dA

rtif

icia

llig

ht,

gree

nhou

se

167

Mal

athi

onB

road

bean

leaf

32P,

acet

one

soln

.M

osta

faet

al.

1974

N.R

.Su

nlig

ht,

fiel

dB

ean

leaf

Em

ulsi

onE

l-R

efai

and

Hop

kins

1972

2d

Sunl

ight

,fi

eld

Cot

ton

leaf

14C

,U

LV

or57

%E

CA

wad

etal

.19

671.

2–3.

8d

Sunl

ight

,gr

eenh

ouse

168

Phen

thoa

teV

alen

cia

oran

ge32

P&

14C

,0.

06%

emul

sion

Tak

ade

etal

.19

763–

7d

Sunl

ight

(Mar

.&

Sept

.)

169

Azi

npho

s-m

ethy

lB

ean

&co

rnle

af14

C,

acet

one

soln

.L

iang

and

Lic

hten

stei

n19

76�

1d

Sunl

ight

(Jun

e–A

ug.)

173

Edi

fenp

hos

Ric

ele

af32

P,em

ulsi

onIs

hizu

kaet

al.

1973

�5

dSu

nlig

ht,

gree

nhou

se

174

Ace

phat

eC

otto

nle

af14

C,

0.1%

Tri

ton

X-1

00B

ull

1979

5.9

hrSu

nlig

ht,

fiel

dT

obac

cole

af50

%W

PY

amaz

aki

etal

.19

825–

8d

Sunl

ight

,gr

eenh

ouse


Tab

le11

.(C

ontin

ued)

.

Plan

tsp

ecie

sA

pplic

atio

nm

ediu

mN

o.Pe

stic

ide

DT

50L

ight

sour

ce(s

easo

n),

cond

ition

sR

efer

ence

s

180

Cya

nofe

npho

sK

idne

ybe

anle

af14

C,

benz

ene-

hexa

ne(4

/1)

+su

rfac

tant

Chi

baet

al.

1976

2.25

wk

Sunl

ight

,gr

eenh

ouse

181

Lep

toph

osC

otto

nle

af32

P,50

%aq

ueou

sac

eton

eZ

ayed

etal

.19

78N

.R.

Sunl

ight

182

But

onat

eB

ean

leaf

32P,

aque

ous

soln

.D

erek

etal

.19

798.

3hr

Sunl

ight

188

Tri

adim

efon

Mar

row

,1s

ttr

uele

af1

mM

,W

PC

lark

etal

.19

78N

.R.

Sunl

ight

,gr

eenh

ouse

189

Tri

adim

enol

App

letr

eele

afA

ceto

ne-w

ater

(3/7

)so

ln.

Cla

rkan

dW

atki

ns19

86N

.R.

Sunl

ight

(Jul

y),

outd

oors

195

Fluo

trim

azol

eB

arle

yle

afA

ceto

ne-w

ater

(1/1

)so

ln.

Cla

rket

al.

1983

N.R

.40

0WH

gla

mp,

gree

nhou

se

199

Len

acil

Suga

rbe

etle

af14

C,

50%

WP

Zha

nget

al.

1999

N.R

.Su

nlig

ht,

gree

nhou

se

202

Din

oseb

Gar

den

snap

bean

leaf

14C

,et

hano

lso

ln.

Mat

suo

and

Cas

ida

1970

0.9

hrSu

nlig

ht(A

ug.)

,gr

eenh

ouse

203

Din

obut

onG

arde

nsn

apbe

anle

af14

C,

etha

nol

soln

.B

anda

lan

dC

asid

a19

720.

3hr

Sunl

ight

(Aug

.),

gree

nhou

se

215

Imid

aclo

prid

Tom

ato

leaf

14C

+20

SLfo

rmul

atio

nSc

holz

and

Rei

nhar

d19

990.

7–1.

4d

Sunl

ight

(51

°N),

gree

nhou

se

220

Fipr

onil

Cor

nle

afA

ceto

neso

ln.

Hai

nzl

and

Cas

ida

1996

�20

hrSu

nlig

ht(N

ov.)

Fene

tet

al.

2001

128 T. Katagi

Tab

le11

.(C

ontin

ued)

.

Plan

tsp

ecie

sA

pplic

atio

nm

ediu

mN

o.Pe

stic

ide

DT

50L

ight

sour

ce(s

easo

n),

cond

ition

sR

efer

ence

s

223

Seth

oxyd

imN

avy

bean

leaf

14C

,aq

ueou

sem

ulsi

on.

Cam

pbel

lan

dPe

nner

1985

b�

1hr

Fluo

resc

ence

light

,gr

eenh

ouse

224

Allo

xydi

mSu

gar

beet

leaf

14C

,aq

ueou

sem

ulsi

onSo

eda

etal

.19

793

dSu

nlig

ht(J

an.–

Mar

.),

outd

oors

245

Gua

zatin

eD

war

fap

ple

leaf

14C

,+

200

ppm

noni

onic

surf

acta

ntSa

toet

al.

1985

a67

wk

Sunl

amps

,gr

owth

cham

ber

250

Ave

rmec

tinB

1aC

eler

y14

C&

3 H,

EC

form

ulat

ion

Moy

eet

al.

1990

5–9

dSu

nlig

ht(J

une–

Mar

.),

outd

oors

251

MA

B1a

Cab

bage

leaf

14C

,E

CW

rzes

insk

iet

al.

1996

N.R

.Su

nlig

ht,

fiel

d

252

Spin

osyn

A4

plan

tsp

ecie

sC

omm

erci

alfo

rmul

atio

nSa

unde

rsan

dB

ret

1997

1.6–

16d

Sunl

ight

N.R

.:no

tre

port

ed.

Form

ulat

ion:

UL

V:

ultr

a-lo

w-v

olum

efo

rmul

atio

n;E

C:

emul

sifi

able

conc

entr

ate;

WP:

wet

tabl

epo

wde

r;FL

:fl

owab

le.


Appendices Listing

Appendix Number Page1 ................................................................................................................................ 1362 ................................................................................................................................ 1373 ................................................................................................................................ 1394 ................................................................................................................................ 1405 ................................................................................................................................ 1416 ................................................................................................................................ 1447 ................................................................................................................................ 1458 ................................................................................................................................ 1469 ................................................................................................................................ 148

10 ................................................................................................................................ 15111 ................................................................................................................................ 152

130 T. Katagi

Directory of pesticide chemical structures.

Pesticide Identification number Appendix number

Acephate 174 9Acrinathrin 31 2Alachlor 34 3Aldrin 122 8Allethrin 10 2Alloxydim 224 11Aminocarb 66 5Amitrole 196 11Anilazine 211 11Asulam 82 5Atrazine 185 10Avermectin B1a 250 11Azadirachtin-A 253 11Azinphos-methyl 169 9Azoxystrobin 244 11Benfuracarb 89 5Benomyl 81 5Bensulide 164 9Bentazone 200 11Benthiocarb 86 5Bioallethrin 11 2Bromacil 198 11Bromophos 140 9Buprofezine 222 11Butachlor 36 3Butamifos 177 9Butonate 182 9Butralin 234 11Butylate 87 5Captan 106 7Carbaryl 71 5Carbofuran 72 5Carbosulfan 88 5Carboxin 42 3Cartap 91 5Chinomethionat 228 11Chloramben 119 8Chlordane 128 8Chlordimeform 207 11Chlorimuron 101 6Chlorimuron ethyl 102 6Chlorothalonil 117 8Chlorpropham 80 5Chlorpyrifos 145 9


Directory of pesticide chemical structures (Continued).


Chlorsulfuron 96 6Chlorthiamid 49 3Cinmethylin 249 11CNP (Chlornitrofen) 217 11Coumaphos 147 9Cyanofenphos 180 9Cyanophos 137 9Cyfluthrin 20 2Cyhalothrin 21 2Cypermethrin 19 2Cyphenothrin 14 2Cyprodinil 210 112,4-D 1 1DDD 132 8DDE 131 8DDOD 113 7DDT 130 8DTP 221 11Deltamethrin 22 2Desmedipham 83 5Diafenthiuron 57 4Diazinon 144 9Dicamba 118 8Dichlobenil 116 8Dichlofluanid 205 11Dichlorvos 153 9Diclofop-methyl 5 1Dicofol 133 8Dicrotophos 157 9Dieldrin 123 8Diflubenzuron 59 4Dimethoate 165 9Dimetilam 75 5Diniconazole-M 190 10Dinobuton 203 11Dinoseb 202 11Dioxabenzofos 183 9Diphenamid 50 3Diquat 226 11Disulfoton 163 9Ditalimfos 178 9Diuron 53 4ETU 95 5Edifenphos 173 9Endosulfan 125 8

132 T. Katagi



Endrin 126 8Esfenvalerate 28 2Ethalfluralin 237 11Ethiofencarb 69 5Ethion 184 9Ethirimol 213 11Ethoxyquin 219 11Etofenprox 32 2Famoxadone 111 7Fenarimol 239 11Fenchlorphos 139 9Fenitrothion 138 9Fenobucarb 62 5Fenothiocarb 85 5Fenpropathrin 24 2Fenpropimorph 227 11Fenthion 143 9Fentin acetate 241 11Fenuron 51 4Fenvalerate 27 2Fipronil 220 11Florasulam 48 3Fluazifop-butyl 6 1Fluchloralin 236 11Flucythrinate 29 2Fludioxinil 208 11Flumetralin 233 11Flumeturon 55 4Fluotrimazole 195 10Flutolanil 39 3Fluvalinate 30 2Folpet 107 7Formothion 166 9Guazatine 245 11Haloxyfop 8 1Heptachlor 127 8Hexachlorobenzene 115 8Hexaconazole 192 10Imazapyr 229 11Imazaquin 230 11Imazethapyr 231 11Imidacloprid 215 11Iodofenphos 141 9Iprodione 109 7Isofenphos 175 9




Isolan 77 5Isoprothiolane 204 11Isoproturon 56 4Isoxaben 46 3Isoxathion 151 9Kadethrin 16 2Lenacil 199 11Leptophos 181 9Lindane 114 8Linuron 54 4MAB1a 251 11MBC 93 5MCPA 3 1Malathion 167 9Maneb 94 5Mecoprop 4 1Mepronil 38 3Metalaxyl 37 3Methazole 112 7Methidathion 171 9Methiocarb 68 5Methomyl 70 5Methoprene 246 11Methoxychlor 134 8Metolachlor 35 3Metolcarb 61 5Metribuzin 201 11Metsulfuron 97 6Metsulfuron methyl 98 6Mevinphos 155 9Mexacarbate 67 5Mobam 73 5Molinate 90 5Monocrotophos 156 9Monuron 52 4NAA 247 11NMH 242 11Naproanilide 41 3Napropamide 47 3Naptalam 44 3Niclosamide 40 3Nitrofen 216 11Norflurazon 214 11Oryzalin 235 11Oxamyl 74 5

134 T. Katagi



Oxycarboxin 43 3Oxyfluorfen 218 11PBacid 243 11Paraquat 225 11Parathion 135 9Parathion-methyl 136 9Penconazole 193 10Pendimethalin 238 11Pentachlorophenol 121 8Perfluidone 206 11Permethrin 17 2Phenmec 60 5Phenmedipham 84 5Phenothrin 13 2Phenthoate 168 9Phorate 162 9Phosalone 170 9Phosmet 172 9Phosphamidon 158 9Photo-dieldrin 124 8Phoxim 152 9Picloram 120 8Pirimicarb 78 5Potasan 146 9Prochloraz 240 11Procymidone 108 7Profenofos 160 9Prometone 187 10Propachlor 33 3Propaphos 159 9Propham 79 5Propiconazole 191 10Propoxur 65 5Propyzamide 45 3Pyrazophos 149 9Pyrethrin-I 9 2Pyridaphenthion 150 9Pyrimethanil 209 11Pyrolan 76 5Quinalophos 148 9Resmethrin 15 2Rimsulfuron 103 6S-2571 176 9S-Bioallethrin 12 2Sethoxydim 223 11




Simazine 186 10Spinosyn A 252 11Sulprofos 161 92,4,5-T 2 12,3,7,8-TCDD 129 8Tefluthrin 18 2Terbacil 197 11Tetrachlovinphos 154 9Tetramethrin 23 2Thiabendazole 212 11Thiadiazuron 58 4Thifensulfuron 104 6Thifensulfuron methyl 105 6Thiophanate-methyl 92 5Tolclofos-methyl 142 9Tralocythrin 26 2Tralomethrin 25 2Triadimefon 188 10Triadimenol 189 10Triasulfuron 100 6Tribenuron methyl 99 6Trichlorfon 179 9Triclopyr 7 1Trifluralin 232 11Trimethacarb 64 5Triticonazole 194 10Vinclozoline 110 7Warfarine 248 11Xylylcarb 63 5

136 T. Katagi

App

endi

x1.

Che

mic

alst

ruct

ures

ofar

ylox

yalk

anoa

tes.

No.

Pest

icid

eX

R1

R2

R3

12,

4-D

C2,

4-C

l 2H

H2

2,4,

5-T

C2,

4,5-

Cl 3

HH

3M

CPA

C4-

Cl-

2-C

H3

HH

4M

ecop

rop

C4-

Cl-

2-C

H3

CH

3H

5D

iclo

fop-

met

hyl

C4-

(2,4

-Cl 2-

Phen

oxy)

CH

3C

H3

6Fl

uazi

fop-

buty

lC

5-C

F 3-2

-Pyr

idyl

oxy

CH

3n-

C4H

9

7T

ricl

opyr

2-N

3,5,

6-C

l 3H

H8

Hal

oxyf

opC

3-C

l-5-

CF 3

-2-P

yrid

ylox

yC

H3

H


App

endi

x2.

Che

mic

alst

ruct

ures

ofpy

reth

roid

s.

No.

Inse

ctic

ide

R1

XY

Con

figu

ratio

nR

2Z

Con

figu

ratio

nR

3

9Py

reth

rin-

IA

1C

H3

CH

31R

-tra

nsB

1—

Z-S

CH=C

H2

10A

lleth

rin

A1

CH

3C

H3

1RS-

cis,

tran

sB

1—

RS

H11

Bio

alle

thri

nA

1C

H3

CH

31R

-tra

nsB

1—

RS

H12

S-B

ioal

leth

rin

A1

CH

3C

H3

1R-t

rans

B1

—S

H13

Phen

othr

inA

1C

H3

CH

31R

S-ci

s,tr

ans

B2

H—

3-Ph

enox

y14

Cyp

heno

thri

nA

1C

H3

CH

31R

S-ci

s,tr

ans

B2

CN

RS

3-Ph

enox

y15

Res

met

hrin

A1

CH

3C

H3

1RS-

cis,

tran

sB

3—

——

16K

adet

hrin

A2

——

E-1

R-c

isB

3—

——

17Pe

rmet

hrin

A1

Cl

Cl

1RS-

cis,

tran

sB

2H

—3-

Phen

oxy

18T

eflu

thri

nA

1C

lC

F 3Z

-1R

S-ci

sB

2H

—2,

3,5,

6-T

etra

fluo

ro-4

-met

hyl

19C

yper

met

hrin

A1

Cl

Cl

1RS-

cis,

tran

sB

2C

NR

S3-

Phen

oxy

20C

yflu

thri

nA

1C

lC

l1R

S-ci

s,tr

ans

B2

CN

RS

4-Fl

uoro

-3-p

heno

xy21

Cyh

alot

hrin

A1

Cl

CF 3

Z-1

RS-

cis

B2

CN

RS

3-Ph

enox

y22

Del

tam

ethr

inA

1B

rB

r1R

-cis

B2

CN

S3-

Phen

oxy

23T

etra

met

hrin

A1

CH

3C

H3

1RS-

cis,

tran

sB

4—

——

138 T. Katagi

App

endi

x2.

(Con

tinue

d).

No.

Inse

ctic

ide

R1

XY

Con

figu

ratio

nR

2Z

Con

figu

ratio

nR

3

24Fe

npro

path

rin

A3

——

—B

2C

NR

S3-

Phen

oxy

25T

ralo

met

hrin

A4

Br

—1R

-cis

B2

CN

S3-

Phen

oxy

26T

ralo

cyth

rin

A4

Cl

—1R

-cis

B2

CN

S3-

Phen

oxy

(28)

/27

(Es)

fenv

aler

ate

A5

—4-

Cl

(2S)

2RS

B2

CN

(S)

RS

3-Ph

enox

y29

Fluc

ythr

inat

eA

5—

4-O

CH

F 22S

B2

CN

RS

3-Ph

enox

y30

Fluv

alin

ate

A5

NH

2-C

l-4-

CF 3

2RB

2C

NR

S3-

Phen

oxy

31A

crin

athr

inA

1H

CO

OC

H(C

F 3) 2

Z-1

R-c

isB

2C

NS

3-Ph

enox

y


App

endi

x3.

Che

mic

alst

ruct

ures

ofan

ilide

san

dam

ides

.

No.

Pest

icid

eR

1R

2R

3

33Pr

opac

hlor

HC

H2C

lC

H(C

H3)

2

34A

lach

lor

2,6-

(C2H

5)2

CH

2Cl

CH

2OC

H3

35M

etol

achl

or2-

C2H

5-6-

CH

3C

H2C

lC

H(C

H3)

CH

2OC

H3

36B

utac

hlor

2,6-

(C2H

5)2

CH

2Cl

CH

2O(C

H2)

3CH

3

37M

etal

axyl

2,6-

(CH

3)2

CH

2OC

H3

CH

(CH

3)C

OO

CH

3

38M

epro

nil

3-O

-iso

-C3H

72-

CH

3Ph

H39

Flut

olan

il3-

O-i

so-C

3H7

2-C

F 3Ph

H40

Nic

losa

mid

e2-

Cl-

4-N

O2

3-C

l-6-

OH

PhH

41N

apro

anili

deH

CH

(CH

3)O

-2-N

apht

hyl

H42

Car

boxi

nH

A1

H43

Oxy

carb

oxin

HA

2H

140 T. Katagi

App

endi

x4.

Che

mic

alst

ruct

ures

ofur

eas

and

benz

oylu

reas

.

No.

Pest

icid

eX

R1

R2

R3

51Fe

nuro

nO

HC

H3

CH

3

52M

onur

onO

4-C

lC

H3

CH

3

53D

iuro

nO

3,4-

Cl 2

CH

3C

H3

54L

inur

onO

3,4-

Cl 2

OC

H3

CH

3

55Fl

umet

uron

O3-

CF 3

CH

3C

H3

56Is

opro

turo

nO

4-is

o-C

3H7

CH

3C

H3

57D

iafe

nthi

uron

S2,

6-(i

so-C

3H7)

2-4-

OPh

tert

-C4H

9H


App

endi

x5.

Che

mic

alst

ruct

ures

ofca

rbam

ates

.

No.

Pest

icid

eR

1R

2R

3X

Y

60Ph

enm

ecC

H3

HPh

OO

61M

etol

carb

CH

3H

3-C

H3P

hO

O62

Feno

buca

rbC

H3

H2-

sec-

C4H

9Ph

OO

63X

ylyl

carb

CH

3H

3,4-

(CH

3)2P

hO

O64

Tri

met

haca

rbC

H3

H3,

4,5

(or

2,3,

5)-(

CH

3)3P

hO

O65

Prop

oxur

CH

3H

2-O

-iso

-C3H

7Ph

OO

66A

min

ocar

bC

H3

H3-

CH

3-4-

N(C

H3)

2Ph

OO

67M

exac

arba

teC

H3

H3,

5-(C

H3)

2-4-

N(C

H3)

2Ph

OO

68M

ethi

ocar

bC

H3

H3,

5-(C

H3)

2-4-

SCH

3Ph

OO

69E

thio

fenc

arb

CH

3H

2-C

H2S

C2H

5-Ph

OO

70M

etho

myl

CH

3H

N=C

(CH

3)SC

H3

OO

71C

arba

ryl

CH

3H

Nap

hth-

1-yl

OO

72C

arbo

fura

nC

H3

HA

1O

O73

Mob

amC

H3

HA

2O

O74

Oxa

myl

CH

3H

N=C

(SC

H3)

C(O

)N(C

H3)

2O

O75

Dim

etila

mC

H3

CH

3A

3O

O76

Pyro

lan

CH

3C

H3

A4

OO

77Is

olan

CH

3C

H3

A5

OO

78Pi

rim

icar

bC

H3

CH

3A

6O

O79

Prop

ham

PhH

iso-

C3H

7O

O80

Chl

orpr

opha

m3-

ClP

hH

iso-

C3H

7O

O81

Ben

omyl

A7

HC

H3

OO

82A

sula

mA

8H

CH

3O

O83

Des

med

ipha

mPh

H3-

NH

CO

2C2H

5Ph

OO

84Ph

enm

edip

ham

3-C

H3P

hH

3-N

HC

O2C

H3P

hO

O

142 T. Katagi

App

endi

x5.

(Con

tinue

d).

No.

Pest

icid

eR

1R

2R

3X

Y

85Fe

noth

ioca

rbC

H3

CH

3(C

H2)

4OPh

OS

86B

enth

ioca

rbC

2H5

C2H

5C

H2-

4-C

lPh

OS

87B

utyl

ate

(CH

3)2C

HC

H2

(CH

3)2C

HC

H2

C2H

5O

S


App

endi

x5.

(Con

tinue

d).

144 T. Katagi

App

endi

x6.

Che

mic

alst

ruct

ures

ofsu

lfon

ylur

eas.

Ary

l

No.

Her

bici

deX

YR

1R

2Z

R3

R4

R5

96C

hlor

sulf

uron

CC

—C

lN

HO

CH

3C

H3

97M

etsu

lfur

onC

C—

CO

OH

NH

OC

H3

CH

3

98M

etsu

lfur

onm

ethy

lC

C—

CO

OC

H3

NH

OC

H3

CH

3

99T

ribe

nuro

nm

ethy

lC

C—

CO

OC

H3

NC

H3

OC

H3

CH

3

100

Tri

asul

furo

nC

C—

OC

H2C

H2C

lN

HO

CH

3C

H3

101

Chl

orim

uron

CC

—C

OO

HC

HC

lO

CH

3

102

Chl

orim

uron

ethy

lC

C—

CO

OC

2H5

CH

Cl

OC

H3

103

Rim

sulf

uron

CN

—SO

2C2H

5C

HO

CH

3O

CH

3

104

Thi

fens

ulfu

ron

A1

——

NH

OC

H3

CH

3

105

Thi

fens

ulfu

ron

met

hyl

A2

——

NH

OC

H3

CH

3


App

endi

x7.

Che

mic

alst

ruct

ures

ofcy

clic

dica

rbox

imid

esan

dre

late

dpe

stic

ides

.

146 T. Katagi

App

endi

x8.

Che

mic

alst

ruct

ures

ofor

gano

chlo

rine

pest

icid

es.


App

endi

x8.

(Con

tinue

d).

148 T. Katagi

App

endi

x9.

Che

mic

alst

ruct

ures

ofor

gano

phos

phor

uspe

stic

ides

.

No.

Pest

icid

eR

1R

2R

3X

135

Para

thio

nO

C2H

5O

C2H

5O

(4-N

O2P

h)S

136

Para

thio

n-m

ethy

lO

CH

3O

CH

3O

(4-N

O2P

h)S

137

Cya

noph

osO

CH

3O

CH

3O

(4-C

NPh

)S

138

Feni

trot

hion

OC

H3

OC

H3

O(3

-CH

3-4-

NO

2Ph)

S13

9Fe

nchl

orph

osO

CH

3O

CH

3O

(2,4

,5-C

l 3Ph)

S14

0B

rom

opho

sO

CH

3O

CH

3O

(2,5

-Cl 2-

4-B

rPh)

S14

1Io

dofe

npho

sO

CH

3O

CH

3O

(2,5

-Cl 2-

4-IP

h)S

142

Tol

clof

os-m

ethy

lO

CH

3O

CH

3O

(2,6

-Cl 2-

4-C

H3P

h)S

143

Fent

hion

OC

H3

OC

H3

O(3

-CH

3-4-

SCH

3Ph)

S14

4D

iazi

non

OC

2H5

OC

2H5

A1

S14

5C

hlor

pyri

fos

OC

2H5

OC

2H5

O(3

,5,6

-Cl 3-

pyri

din-

2-yl

)S

146

Pota

san

OC

2H5

OC

2H5

A2

S14

7C

oum

apho

sO

C2H

5O

C2H

5A

3S

148

Qui

nalo

phos

OC

2H5

OC

2H5

A4

S14

9Py

razo

phos

OC

2H5

OC

2H5

A5

S15

0Py

rida

phen

thio

nO

C2H

5O

C2H

5A

6S

151

Isox

athi

onO

C2H

5O

C2H

5A

7S

152

Phox

imO

C2H

5O

C2H

5O

N=C

(CN

)Ph

S15

3D

ichl

orvo

sO

CH

3O

CH

3O

CH=C

Cl 2

O15

4T

etra

chlo

vinp

hos

OC

H3

OC

H3

OC

(=C

HC

l)(2

,4,5

-Cl 3P

h)O

155

Mev

inph

osO

CH

3O

CH

3O

C(C

H3)=C

HC

OO

CH

3O

156

Mon

ocro

toph

osO

CH

3O

CH

3O

C(C

H3)=C

HC

(O)N

HC

H3

O15

7D

icro

toph

osO

CH

3O

CH

3O

C(C

H3)=C

HC

(O)N

(CH

3)2

O15

8Ph

osph

amid

onO

CH

3O

CH

3O

C(C

H3)=C

ClC

(O)N

(C2H

5)2

O15

9Pr

opap

hos

O-n

C3H

7O

-nC

3H7

O(4

-SC

H3P

h)O


App

endi

x9.

(Con

tinue

d).

No.

Pest

icid

eR

1R

2R

3X

160

Prof

enof

osO

C2H

5S-

nC3H

7O

(4-B

r-2-

ClP

h)O

161

Sulp

rofo

sO

C2H

5S-

nC3H

7O

(4-S

CH

3)Ph

S16

2Ph

orat

eO

C2H

5O

C2H

5SC

H2S

C2H

5S

163

Dis

ulfo

ton

OC

2H5

OC

2H5

SCH

2CH

2SC

2H5

S16

4B

ensu

lide

O-i

so-C

3H7

O-i

so-C

3H7

SCH

2CH

2NH

S(O

) 2Ph

S16

5D

imet

hoat

eO

CH

3O

CH

3SC

H2C

(O)N

HC

H3

S16

6Fo

rmot

hion

OC

H3

OC

H3

SCH

2C(O

)N(C

HO

)CH

3S

167

Mal

athi

onO

CH

3O

CH

3SC

H(C

OO

C2H

5)C

H2C

OO

C2H

5S

168

Phen

thoa

teO

CH

3O

CH

3SC

H(C

OO

C2H

5)Ph

S16

9A

zinp

hos-

met

hyl

OC

H3

OC

H3

A8

S17

0Ph

osal

one

OC

2H5

OC

2H5

A9

S17

1M

ethi

dath

ion

OC

H3

OC

H3

A10

S17

2Ph

osm

etO

CH

3O

CH

3A

11S

173

Edi

fenp

hos

OC

2H5

SPh

SPh

O17

4A

ceph

ate

OC

H3

NH

C(O

)CH

3SC

H3

O17

5Is

ofen

phos

OC

2H5

NH

-iso

-C3H

7O

(2-C

(O)O

-iso

-C3H

7Ph)

S17

6S-

2571

OC

2H5

NH

-iso

-C3H

7O

(3-C

H3-

6-N

O2P

h)S

177

But

amif

osO

C2H

5N

H-s

ec-C

4H9

O(3

-CH

3-6-

NO

2Ph)

S17

8D

italim

fos

OC

2H5

OC

2H5

A12

S17

9T

rich

lorf

onO

CH

3O

CH

3C

H(O

H)C

Cl 3

O18

0C

yano

fenp

hos

OC

2H5

O(4

-CN

Ph)

PhS

181

Lep

toph

osO

CH

3O

(2,5

-Cl 2-

4-B

rPh)

PhS

182

But

onat

eO

CH

3O

CH

3C

H(C

Cl 3)

OC

(=O

)C3H

7O

150 T. Katagi

App

endi

x9.

(Con

tinue

d).


App

endi

x10

.C

hem

ical

stru

ctur

esof

tria

zine

san

daz

oles

.

No.

Pest

icid

eR

1R

2R

3

185

Atr

azin

eC

lC

H(C

H3)

2C

H2C

H3

186

Sim

azin

eC

lC

H2C

H3

CH

2CH

3

187

Prom

eton

eO

CH

3C

H(C

H3)

2C

H(C

H3)

2

152 T. Katagi

App

endi

x11

.C

hem

ical

stru

ctur

esof

mis

cella

neou

spe

stic

ides

.


App

endi

x11

.(C

ontin

ued)

.

154 T. Katagi

App

endi

x11

.(C

ontin

ued)

.


App

endi

x11

.(C

ontin

ued)

.

156 T. Katagi

App

endi

x11

.(C

ontin

ued)

.


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Manuscript received September 20, accepted October 20, 2003.

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Photodegradation of Pesticides on Plant and Soil …. Environmental Factors Affecting Soil...

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