air6

‚§√ß°“√»÷°…“¡≈¿“«–∑“ßÕ“°“»Õ—π‡π◊ËÕß¡“®“° “√‚æ≈’‰´§≈‘°Õ–‚√¡“µ‘°‰Œ‚¥√§“√å∫Õπ (PAH) „π∫√√¬“°“»‡¢µ°√ÿß‡∑æ¡À“π§√1. °“√®”·π°·≈–ª√‘¡“≥«‘‡§√“–ÀåAirborne Polycyclic Aromatic Hydrocarbon (PAH) In Bangkok Urban AirI. Characterization and Quantification

Hathairatana Garivait*, Wanna Laowagul*

Phaka Sukasem*, Sunthorn Ngod-Ngam*

Chongrak Polprasert**, Lars Baetz Reutergardh**

∫∑§—¥¬àÕæƒµ‘°√√¡¢Õß “√‚æ≈’‰´§≈‘°Õ–‚√¡“µ‘°

‰Œ‚¥√§“√å∫Õπ (PAH) „π∫√√¬“°“»¢÷Èπ°—∫§ÿ≥ ¡∫—µ‘

∑“ß¥â“πøî ‘° å·≈–‡§¡’¢Õß “√¥—ß°≈à“« ¥—ßπ—Èπ°“√

°√–®“¬µ—«·≈–°“√‡°‘¥ªØ‘°‘√‘¬“¢Õß “√ PAH „π

∫√√¬“°“»„π‡¢µ√âÕπ®÷ßπà“®–·µ°µà“ß®“°∑’Ë‡°‘¥¢÷Èπ

„π∫√√¬“°“»‡¢µÀπ“« ·µàÕ¬à“ß‰√°Áµ“¡°“√»÷°…“

æƒµ‘°√√¡¢Õß “√ PAH „π∫√√¬“°“»‡¢µ√âÕπ¬—ß¡’

Õ¬ŸàπâÕ¬¡“°„πªí®®ÿ∫—π

°“√»÷°…“§√—Èßπ’È ‰¥â∑”°“√ ”√«®≈—°…≥–

‡©æ“–¢Õß°“√°√–®“¬µ—«¢Õß “√ PAH „π∫√√¬“°“»

‡¢µ‡¡◊Õß¢Õß°√ÿß‡∑æ¡À“π§√ ‚¥¬§”π÷ß∂÷ß°“√

°√–®“¬µ—«¢Õß “√ PAH „π√Ÿª¢Õß°ä“´·≈–„π

*»Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ °√¡ àß‡ √‘¡§ÿ≥¿“æ ‘Ëß·«¥≈âÕ¡ ‡∑§‚π∏“π’ µ.§≈ÕßÀâ“ Õ.§≈ÕßÀ≈«ß ®.ª∑ÿ¡∏“π’ 12120 ‚∑√. 0-2577-1136 ‚∑√ “√. 0-2577-1138Environmental Research and Training Center, Department of Environmental Quality Promotion. Technopolis. Klong 5 Klong Luang, Pathumthani 12120 e-mail: [email protected]**Asian Institute of Technology, Pathumthani, Thailand

High Performance Liquid Chromatograph

Incinerator

√Ÿª¢ÕßΩÿÉπ≈–ÕÕß µ≈Õ¥®π°“√°√–®“¬µ—«„π√Ÿª¢Õß

ΩÿÉπ≈–ÕÕß·∫∫·¬°¢π“¥ °“√‡°Á∫µ—«Õ¬à“ß∑”‚¥¬°“√

„™â ‡§√◊ËÕß‡°Á∫µ—«Õ¬à“ßΩÿÉπ≈–ÕÕß·∫∫·¬°¢π“¥

(Andersen çlow volumeé Sampler) µàÕ‡¢â“°—∫

À≈Õ¥‡°Á∫°ä“´ ∑’Ë∫√√®ÿ¥â«¬ XAD-2 “√ PAH 9

™π‘¥ ∑’Ë∑”°“√»÷°…“‡ªìπ “√∑’Ë¡’§ÿ≥ ¡∫—µ‘‡ªìπ “√

°àÕ¡–‡√Áß·≈–‡ªìπ “√√à«¡°àÕ¡–‡√Áß ‰¥â·°à Pyrene

(PYR), Benz(a) Anthraecene (BaA), Benzo(e)

Pyrene (BeP), Dibenz(a,c)Anthracene (DBacA),

Benzo(k)Fluoranthene (BkF), Benzo(a) Pyrcne

(BaP), Dibenz(a,h) Anthracene (DBahA),

Benzo(ghi) Perylene (BghiP) ·≈– Trimethyl-

cholanthrene (3MC) ‚¥¬„™â°“√ °—¥·∫∫Õ—≈µ√â“

‚´π‘° ·≈–„™â‡∑§π‘§ High Pressure Liquid

Chromatography (HPLC) „π°“√®”·π° “√∑—Èß 9

™π‘¥ ·≈–°“√»÷°…“æ∫«à“‡∑§π‘§„π°“√‡°Á∫µ—«Õ¬à“ß∑’Ë

‰¥âÕÕ°·∫∫¢÷Èπ„π°“√»÷°…“§√—Èßπ’È‡À¡“– ¡„π°“√

”√«® “√ PAH ∑’Ë¡’πÈ”Àπ—°‚¡‡≈°ÿ≈µ—Èß·µà 202

¢÷Èπ‰ª „π∫√√¬“°“»‡¢µ√âÕπ ‡π◊ËÕß®“°‰¡à¡’ “√ PAH

„¥Ê „π 9 ™π‘¥ π’Èª√“°Ø„π™—Èπ∑’Ë 2 ¢Õßµ—«¥Ÿ¥´—∫

°ä“´ (XAD-2) ∑’Ë∫√√®ÿ„πÀ≈Õ¥‡°Á∫°ä“´ ∂÷ß·¡â«à“

Õÿ≥À¿Ÿ¡‘„π∫√√¬“°“»®– Ÿß∂÷ß 35 Õß»“‡´≈‡´’¬

ABSTRACTThe behavior of airborne PAH is

related to their physical and chemical

proper t ies. Thus, in a tropical urban

environment, they are expected to have

phase distributions and reactivities which are

quite different from those established for

temperate areas. Nevertheless, such studies

are still scarce in the tropics.

In this study, the characteristics of

PAH in Bangkok urban air were investigated

with respect to gas-particle partitioning and

dependency on particle size. A sampling

system which consisted of an 8 stage size

fractionating cascade impactor (Andersen

çlow volumeé Sampler) and a downstream

XAD-2 adsorbent tube was used for sample

collection. Nine PAH, classified as carcinogenic

and co-carcinogenic compounds - Pyrene

(PYR), Benz (a) Anthracene (BaA), Benzo (e)

Pyrene (BeP), Dibenz(a,c)Anthracene (DBacA),

Benzo(k)Fluoranthene (BkF) , Benzo(a)

Pyrene (BaP) , D ibenz (a ,h )Anth racene

(DBahA), Benzo(ghi)Perylene (BghiP) and

Trimethylcholanthrene (3MC) - were quantified

by ultrasonic extraction and HPLC with

fluorescence detection. The quantitative and

qualitative compositions of these nine PAH

samples are described. It was concluded

that1 the sampling system designed in this

study is suitable for the investigation of

airborne PAH (with molecular weights of 202

and above) in the tropical climate since even

at sampling temperatures of ~ 35 ÌC, none of

the listed PAH was traceable in the second

layer of the XAD-2 adsorbent tube.

1. IntroductionPolycyclic Aromatic Hydrocarbons

(PAH) in the environment are almost

exclusively generated from combustion

sources. They were one of the first atmospheric

pollutants to be identified as being carcinogenic

and mutagenic.1-3 Due to their moderate

volatilities, PAH are found in the atmosphere

in two forms; adsorbed on suspended

par ticles and in the gas phase.4-6 The

association of PAH with the respirable fraction

of airborne particulate matter and their

corresponding gas phase are of particular

importance in terms of their human health

effects.7-9 Furthermore, ambient urban air

levels of PAH are of concern because they

are produced from the combustion of fossil

fuels. In deed, they are present in emissions

from many stationary and mobile combustion

sources, including those from refuse

incineration10 and combustion of gasoline

and diesel by vehicles.11-13 In this study, an

investigation on airborne PAH was carried

out in the Bangkok area where air pollution is

of significant concern.

Being the capital of Thailand, Bangkok

is the largest city with a population of 8

millions and a population density of 4,615

§-46 »Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ °√¡ àß‡ √‘¡§ÿ≥¿“æ ‘Ëß·«¥≈âÕ¡

inhabitants/km2. Given current growth patterns,

the city will be a megacity in the year 2000.

The city lies in the monsoon zone in which

seasonal monsoon winds and sea breezes

prevail. The city is now facing serious air

pollution problems, since it has been the center

of rapid development in the country during

the past 5 decade. Particulate matter pollution

for particles equal to or less than 10 µm

in diameter (PM10) often exceeds the U.S.

24 hours standard of 150 mg/m3 for days

and weeks at a time. The major origins of

particulate matter pollution could be attributed

to construction activities and motor vehicle

traffic.14

At present, progress in the control of

atmospheric particulate matter in Thailand is

evaluated by calculating the total weight of

material collected by using a standard high

volume technique. This technique has been

applied to both total suspended particulate

matter (since 1981) and PM10 (since 1995).

The PM10 levels in Bangkok urban areas

generally exceeded the Thai ambient air

quality standard value of 120 mg/m3 over a

24 hours period. This severe situation may

reflect the fact that the air pollution control

techniques and/or technologies we have been

using in this area may not be very effective

for the particles in the respirable size range

(< 5 µm). Various issues have recently been

investigated to mitigate the air pollution

in Bangkok, e.g. Air Quality Management

Planning (1991); A Review of Current Air

Quality Standard (1993); Characterization of

ambient Suspended Particulate Matter (SPM)

in the Bangkok Metropolitan Region, BMR

(1996). These studies only emphasized the

quantity and elemental composition of SPM.

Those focus on the carcinogenic substances

such as PAH in airborne particulate matter are

still scarce in this country, even though

statistics on cancer in Thailand from 1988

to 1991 have shown that lung cancer is

the most common form of cancer in both

sexes in areas where the air pollution levels

are considered dangerous.15

On the other hand, many studiesaddressing carcinogenic substances inairborne particulate matter were performedworldwide over 20 years ago. However, mostof them were conducted in temperateenvironments. Although the concentrationsof PAH in urban environments have beenextensively studied, there are very few reportsfrom tropical areas and there is a notablepaucity of data from the Association ofSoutheast Asian Nations (ASEAN) region. Thelevels and distributions of airborne PAH ina tropical environment are expected to bedifferent from those obtained in the temperateones due to differences in type and scale ofemission sources as well as air temperature

In Thailand, the first study of thistype was done by Matsushita et al. (1987).16

Carcinogenic PAHs in airborne particulatein Bangkok, Chiang Mai and Tokyo werecompared. At that time, only total suspendedpar ticulate matter was considered. Theinfluences of the particle size and of thecorresponding gas phase on the PAHcomposition were not documented. Theobjective of this study is to implement anappropriate sampling and analytical techniqueto investigate the amount of airborne PAHwith respect to their particle size dependencyand phase distribution in Bangkok. This aimsto provide an understanding of the environ-mental fate and the extent of human exposureto these substances in a tropical environment.

2. Methods and Materials

2.1 Sampling LocationsTo measure PAH and to characterize

PAH composition with respect to their

gas-particle partitioning and size dependency

in the Bangkok urban area, an urban

residential site, the Office of Environmental

»Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ °√¡ àß‡ √‘¡§ÿ≥¿“æ ‘Ëß·«¥≈âÕ¡ §-47

Policy and Planning (OEPP), was selected

from the National Air Quality Monitoring

Network in Bangkok. It is located in the urban

center and is surrounded by commercial

buildings, government offices, houses, roads

and expressways. Moreover, there are few

industries within a 10 km radius of the

sampling site. The sampler was placed about

20 meters from the ground on the top of a

7-story building.

2.2 Sampling SystemTo invest igate the gas-par t ic le

distribution and particle size dependency of

PAH, a combination of an Andersen low

volume cascade impactor (SIBATA model

AN-200) followed by a glass tube containing

XAD-2 polymer beads was used (Figure 1).

The selection was made after considering

the advantage of impactor sampling which

provides minimal contact of col lected

particulate matter with the air stream so that

the particle blow-off effect can be kept toa minimum. Furthermore, cascade impactorsample provides particles over the inhalablesize range. T60A20 Teflon-coated glass fiberfilters were used to collect particles on eachof the impactor stages as well as particlesthat were too small to be collected by theimpactor. T60A20 appears to have superiorfiltering qualities because of its reducedsurface activity.17 This may contribute to areduced degradation of collected PAH duringsampling and storage. XAD-2 (Styrene-divinylbenzene polymer beads) was usedto adsorb gas-phase constituents. XAD-2adsorbent has several advantages in terms ofcollection ef f iciency, good recovery ofadsorbed compounds and minimal degra-dation during storage.18 In order to insurethe proper aerodynamic cut-off diameter for50% collection efficiency, it is necessary tooperate the sampling system at a flow rateof 28.3 L/min. Under these conditions, the

Figure 1 Sampling system used in this study.


equivalent aerodynamic cut-off diameters

at 50% collection efficiency for each stage of

the impactor are given in Table 1. The XAD-2

adsorbent tube was designed in this study by

referring to the level of pressure drop across

the sampler in order to maintain constant flow

rate during the sampling period. The design of

the XAD-2 adsorbent tube is illustrated in

Figure 1. The sampling system was calibrated

according to the procedure described in the

SIBATA model AN-200 Corporationûs manual.

2.3 MaterialsTeflon coated glass f iber f i l ters

(T60A20) with a diameter of 80 mm were

purchased from the Pallflex Corp. SIBATA,

Japan. The purity of the filters was checked

before use by carrying out the same extraction

and analysis procedure as that for the

samples. The blank values of the target

compounds in the extracts from these filters

were generally below their detection limits, and

therefore, no pre-treatment of the filters was

necessary. The filters were conditioned at con-

stant relative humidity (50 ± 2%) and

temperature (24 ± 2 ÌC) in a dark desiccator

for 24 hours prior to weighing. They were

then wrapped with clean Aluminum foil and

kept in a capped plastic bag until sampling.

XAD-2 was purchased from theORGANO Company, Japan. Each XAD-2 wascleaned by first soaking in methanol followedby two Soxhlet extractions with a mixtureof dichloromethane : acetonitrile (1:1, v/v) for16 hours. It was then heated at 70 ÌC todryness in a clean oven for about 30 min.The cleaned XAD-2 was placed in a cleanpolyethylene bottle with a screw cap. XAD-2blanks were evaluated by the same analysisused for target gaseous samples. The cleaningprocedure of XAD-2 was repeated until lowblank values were obtained (each selectedPAH < 10ng/12g XAD-2). The packing of theXAD-2 adsorbent tube was done in thelaboratory. The two ends of the tube wereclosed with Teflon tape and polyethylenecaps. The tube was, then, wrapped withAluminum foil to protect it from light and keptin a capped plastic bag until sampling.

All solvents were chromatographicgrade (MERCK, Germany). Individual PAHstandard reagents were purchased from WakoPure Chemical Industries (Osaka, Japan) andStandard Reference Material (Urban Dust,SRM 1649c) was obtained from the NationalInstitute of Standards and Technology (NIST),USA. The cleaning procedure for glasswarewas done according to the guideline ofU.S.EPA method TO-13.19

Stage number Equivalent aerodynamic cut-off

diameters at 50% efficiency (µm.)

0 > 11

1 7.0 - 11

2 4.7 - 7.0

3 3.3 - 4.7

4 2.1 - 3.3

5 1.1 - 2.1

6 0.65 - 1.1

7 0.43 - 0.65

backup < 0.43

Table 1 SIBATA, AN-200 low volume cascade impactor characteristics.


2.4 Sample Collection and AnalysisTo avoid wet removal of airborne

PAH20, the study was done during the dry

season when SPM pollution in Bangkok is

the most serious.

Sample collection was performed by

drawing air at flow rate of 28.3 L/min. through

the sampling unit. The particulate phase

was defined as that trapped on the filters for

all eight stages of the impactor and the

backup filter in the particle size separation

unit. The corresponding gas phase was

defined as that associated with the two layers

of XAD-2 packed in the adsorbent tube. PAH

were sampled for 24 hours during 23-29

May 1996, resulting in 7 sets of samples.

The exposed filters were folded in half and

wrapped separately in Aluminum foil; then

the set was kept together in a capped plastic

bag, while the exposed XAD-2 adsorbent

tube was capped and put into a capped

plastic bag to reduce contamination. After

collection, the samples were transferred

back to the laboratory where the filters were

dried in a dark desiccator for 24 hours and

weighed 3 times on a 5 decimal place

gram analytical balance. Weight differences

were used to determine the particulate matter

concentration in each particle size range. All

samples were stored at -85 ÌC in the dark

until extraction.

2.5 Chemical Analysis2.5.1 Particle-bound PAH

A very sensitive analytical method

(Matsushita et al., 1994)21 was referred to

determine particulate-PAH concentrations in

this study. This method was developed to

survey indoor PAH pollution. It was appropriate

for this study because sample collection was

performed with an Andersen low volume air

sampler for only 24 hours, hence requiring

high sensitivity. The description of analytical

procedure is outlined as follows:

Two or four circular samples, each of 25 mm

diameter, were punched out from each stage of

the Andersen sampler and cut into small pieces

with ceramic scissors. All pieces were put into

a screw cap centrifuge tube (20 mL) with a

Teflon liner. 15 mL of dichloromethane was

added to the tube. The tube was sealed and

placed in an ultrasonic bath (38 Hz, 250 W)

and sonicated twice for 20 min at 10 ÌC. The

tube was then centrifuged at 3000 rpm for 10

min. 10 ml of supernatant was transferred to

a small test tube, and 30 µL of DMSO

(dimethylsulfoxide) was added to retain PAH.

The test tube was then set in a dry thermostat

unit (Taitec, Model DTU-1B) at about 30 ÌC

and the dichloromethane was evaporated

under a gentle nitrogen stream. The residue

in the test tube was dissolved with 970 mL

of acetonitrile. Finally, the extracted samples

were filtered prior to separation analysis using

a CAMEO II, filter assembly with a 0.22 µm

pore Nylon filter.

2.5.2 Gas phase PAH

Each exposed XAD-2 adsorbent (i.e.

12 g and 5 g) was extracted separately twice

with a 100ml mixture of acetonitrile and

dichloromethane 1:1 (v/v) in an ultrasonic bath

for 20 min at 10 ÌC. The crude extracts were

treated identically to the aerosol extracts.

2.6 Determination of PAHSeparation analysis was performed

on a Shimadzu LC9A High Performance

Liquid Chromatograph (HPLC) with fluores-

cence detection. Excitation and emission

wavelengths were 295 nm and 405 nm,

respectively. A wide bore Octadecyl column

(C18, 5 mm., Wakosil) 4.6 x 250 mm and an

identical pre-column of 50 mm were used.

The mobile phase flow was 1mL/min and

the gradient conditions were: 50% acetonitrile

in water (5 min) followed by, 50% to 85% (20

min, linear), 85% to 100% (20 min, linear),

100% (20 min). The temperature of the columns


was maintained at 40 ÌC and a 50 mL

injection volume was used. The two eluents, ac-

etonitrile and water, were filtered through

0.22 µm filters before use. The nine PAH,

classified as carcinogenic and co-carcino-

genic compounds - Pyrene (PYR), Benz(a)

Anthracene (BaA), Benzo(e)Pyrene (BeP),

Dibenz(a,c)Anthracene (DBacA), Benzo(k)

Fluoranthene (BkF), Benzo(a)Pyrene (BaP),

Dibenz(a,h)Anthracene (DBahA), Benzo(ghi)

Perylene (BghiP) and Trimethylcholanthrene

(3MC) - were identified and their concentrations

determined by comparison with a mixture of

authentic standards.

3. Results and Discussion

3.1 Reliability of PAH AnalysisIn the study, nine PAH compounds

were selected as indicators of atmospheric

carcinogenicity and/or mutagenicity. Before the

sampling program, the recovery of PAH on XAD-

2 and on the filters was determined. This

involved spiking six separate XAD-2 adsorbent

(12 grams) and six filters with a working

standard containing all the PAH compounds.Generally, reasonable recovery was obtainedfor the selected PAHs as shown in Table 2.The minimum detectable concentration of

PAH in ng/m3 represented a value equivalentto a 40 m3 air sample and 50 µL HPLCinjection, the normal operating conditions inthis study. Table 3 indicates the detectionlimits of the PAH ranging from 0.01 to 0.04 ng/m3. The relative standard deviations were less than 15%. The minimum detectable con-centrations in the vapor phase were slightlyhigher than those in the particulate phase.This is probably due to the blank quality ofthe XAD-2: the extract from the blank XAD-2presented high background peaks of differentPAH of interest, especially BeP. Each PAHcompound was quantified against a series ofcalibration standards made up from the stocksolution. In order to verify the calibration, aconfirmation working standard was run eachtime after 10 sample injections. For qualityassurance, Standard Reference Material (SRM)1649c Urban Dust was run for the selectedPAH. The resulting values were in goodagreement with certified values given for thismaterial (see Table 4). Typical chromatogramsof particulate and gaseous phase PAH are

shown in Figure 2. The result showed that

the target PAH in particulate and gas phase

samples could be analyzed without any major

interference from other coexisting PAH.

Table 2 Recovery of the selected PAH from the XAD-2 and the filter substrate

PAH% recovery (RSD)*, average of 6 runs.

XAD-2 Filters

PYR 75.3 (4.8) 95.1 (2.3)

BaA 89.4 (4.3) 93.4 (4.1)

BeP 78.5 (6.3) 89.3 (8.0)

DBacA 83.3 (13) 76.8 (6.7)

BkF 91.7 (4.3) 90.5 (5.6)

BaP 89.6 (5.9) 90.6 (5.0)

DBahA 72.8 (18) 85.3 (9.1)

BghiP 93.6 (8.0) 88.5 (7.0)

3MC 92.7 (6.7) 89.5 (6.3)

* RSD = Relative Standard Deviation.


Table 3 Minimum detectable concentration of the PAH in the particulate and vapor phases.

PAH

Minimum detectableconc. of PAH, ng/m3

Particulate phase Vapor phase

PYR 0.04 0.05BaA 0.01 0.03BeP 0.02 0.05

DBacA 0.01 0.03BkF 0.02 0.03BaP 0.02 0.05

DBahA 0.02 0.03BghiP 0.03 0.033MC 0.03 0.03

Table 4 Mean concentrations of PAH analyzed in Reference Urban Dust (SRM 1649c), average in 7 runs.

PAH mg/g (SD) Certified Value

PYR 7.08 (0.12) 6.3 ± 0.4BaA 2.60 (0.16) 2.8 ± 0.3BeP 4.30 (0.30) -

DbacA 0.32 (0.04) -BkF 2.00 (0.10) 2.0 ± 0.1BaP 2.50 (0.10) 2.6 ± 0.4

DbahA 0.65 (0.02) -BghiP 3.81 (0.18) 3.9 ± 0.83MC nd. -

SD = Standard Deviation, nd = not detected

PAH Andersen stage number Filter XAD-2* Total**

0 1 2 3 4 5 6 7 Backup (P-PAH) (G-PAH) conc.

PYR 0.040 0.143 0.146 0.070 0.062 0.051 0.175 0.221 0.352 1.30 12.70 14.00BaA 0.038 0.047 0.054 0.041 0.037 0.032 0.050 0.070 0.136 0.50 0.16 0.65BeP 0.022 0.042 0.083 0.06 0.06 0.104 0.141 0.151 0.357 1.02 0.27 1.29DBacA nd nd nd nd nd nd 0.016b nd 0.044b 0.06 nd 0.06BkF nd nd nd nd nd 0.024 0.059 0.067 0.248 0.40 nd 0.43BaP nd nd nd nd nd 0.034 0.083 0.137 0.413 0.67 nd 0.67DBahA nd nd nd nd nd nd 0.026a nd 0.039d 0.07 nd 0.67BghiP nd nd nd 0.030 0.042 0.111 0.28 0.363 1.281 2.11 nd 2.113MC nd nd nd nd nd nd nd nd 0.05c 0.05 nd 0.05

* Experiments with two XAD-2 layers inseries; none of the listed PAHs were traceable in the second layer.** Total conc. = Particulate phase + Gaseous phase PAH.a,b,c,d Indicate the average value of n =1, n = 2, n = 3, n = 5, respecively. n = number of observations.P-PAH = particle bound PAH.G-PAH = gaseous PAH.

Table 5 Average PAH concentrations (ng/m3) of air samples collected at OEPP, number of

observation; n = 7


Figure 3 Relative proportion of airborne PAHs in gas and particulate phases at OEPP sampling site.

Figure 2 Typical chromatograms of airborne PAHs extract and PAH standard solution.


3.2 PAH Concentrations

Field sampling was conducted at

the OEPP sampling site, a Bangkok urban-

residential area, during 7 days of the dry

season (May 1996). The ambient temperatures

ranged from 27 to 30 ÌC and relative humidity

ranged from 73 to 85%. At this site, the

prevailing wind direction during sampling was

S/SE or S/SW and wind speeds ranging

from 1.7 to 2.3 m/s. The concentration data

of PAH in the different particle sizes and their

distribution in vapor phase are shown in

Table 5 and Figure 3. It is obvious that,

PYR, BaA, BeP, BkF, BaP and BghiP were

predominant in this area. Results showed that

the fraction in the gas phase increased

with increasing volatility. Pyrene was almost

entirely in the gas phase, BaA and BeP were

about 25% and 21% in the gas phase,

respectively. All the other compounds had

negligible gas-phase concentrations. Parti-

culate-PAH were found mostly on particles

less than 2.1 µm in size. These results

were consistent with other studies22-24 with

the exception of BaA and BeP. Their relative

proportion in the gas phase (25% and 21%,

respectively) seemed to be lower than in

other studies. This may due to the fact that

PAH of four rings or less exist mainly in the

gas phase under typical ambient conditions,

enabling them to undergo atmospheric

reactions with any one of several reactive

substances such as hydroxyl radicals, ozone

and nitrate radicals, which are present at low

concentrations in the troposphere.25-27 Besides,

sunlight intensity has the strongest influence

on PAH decay.28 These reactions would thus

result in relatively short atmospheric lifetimes

for the gas-phase PAH. The strong sunlight

in the tropical climate, poor air quality in

Bangkok, and the significant time scales

required to re-establish equilibrium after

gas-phase photolysis and reaction with the

pollutants29 may thus explain the lower

proportion of BaA and BeP in gas phase.

It should be noted that in the temperate

environment, the amount and range of PAH

in the urban areas exhibit seasonal fluctuations.

In most cases, higher levels are apparent in

winter compared to summer. The reasons

are not only due to changes in the contributions

of the possible sources like residential heating

and automobiles to the PAH levels, but they

are also the results of a higher atmospheric

react iv i ty of PAH during the summer

months.26,28,30 The total concentrations of the

individual PAH obtained in an urban residential

area (Table 5) was generally consistent with

summertime results in temperate environments

reported by other authors using similar

sampling techniques (Filter with adsorbent

backup)22,24,31 when domestic heating was not

in use, although higher atmospheric reactivity

would be expected in the Bangkok urban air.

Although 16 PAH species have

recently been identified as hazardous air

pollutants in the Title III of the U.S. Clean Air

Act Amendments of 1990, there are still no air

quality standards set for PAH. Only BaP, the

most carcinogenic of the PAH, has been widely

studied. According to WHO (World Health

Organization) Guideline 1987, the estimated

lung cancer risk, connected with exposure to

1 ng/m3 of BaP for a lifetime, would be

9 x 10-5. The level of BaP obtained in this

study, 0.67 ng/m3, was still within the WHO

Guideline. However, more investigations

are needed in terms of concentration and

distribution of airborne PAH in this area.

4. ConclusionThe results obtained in this study

have shown that the experimental setting

adapted from the literature is appropriate for

investigating the characteristics and quantity of

PAH content in Bangkok urban air. It is worth

noting that the concept of an Andersen

cascade low volume impactor in combination


with XAD-2 adsorbent tube represent a suitable

alternative of obtaining results that takes into

account the phase distribution and the particle

size dependency of airborne PAH. The

collection of the gas phase PAH by the XAD-2

adsorbent tube, specially designed in this

study, was found to be a well-adapted tool for

sampling in tropical climates where sunlight

and temperature conditions are expected to

strongly influence the gas-particle partitioning

of certain PAH. In deed, we noted in this study

that even at the sampling temperatures of

~ 35 ÌC during daytime, none of the listed

PAH (with molecular weights of 202 and

above) was detected in the backup layer of

the XAD-2 adsorbent tube.

5. AcknowledgementsWe gratefully acknowledge Environ-

mental Research and Training Center, Thailand

for the support of this study. The very helpful

advices of Professor H. Matsushita and Dr.

T. Amagai, University of Shizuoka, Japan for

the establishment of the analytical method

are greatly appreciated. We are extremely

grateful to Professor R.M. Kamens and Dr. M. R.

Strommen, University of North Carolina at

Chapel Hill USA, for their very helpful comments.

We also deeply appreciate Pollution Control

Department, Thailand for the support of air

quality monitoring data in Bangkok.

6. References1. International Agency for Research in

Cancer, (1983), IARC Monographs on the

Evaluation of the Carcinogenic Risk of

Chemicals to Humans : Polynuclear Aromatic

Compounds, Part 1., Volume 32, IARC,

Lyon, France.

2. W. R. Gala and J. P. Giesy, (1994), Environ.

Toxico. Chem., 13, pp. 831.

3. R. Van Der Oost, F. Van Schooten, F. Ariese,

H. Heida, K. Satumalay and N. P. E.

Vermerlen, (1994), Environ. Toxico. Chem.,

13, pp. 859.

4. S. O. Baek, R. A. Field, M. E. Goldstone,

P. W. Kirk, J. N. Lester and R. Perry, (1991),

Water, Air and soil Pollution, 60, pp. 279.

5. J. F. Pankow, (1987), Atmos. Environ., 21,

pp. 2275.

6. H. Yamasaki, K. Kuwata and H. Miyamoto,

(1982), Environ. Sci. Technol., 16, pp. 189.

7. R-H. Lin, C-R. Wang and C-S. Li, (1994),

Environment International, 20, pp. 161.

8. K. Nikolaou, P. Masclet and G. Mouvier,

(1984), Sci. Total Environ., 32, pp. 103.

9. D. Grosjean, (1983), Atmos. Environ., 17, pp.

2565.

10. Y. Mamane, (1990), Atmos. Environ., 24A,

pp. 127.

11. T. Nielsen, (1996), Atmos. Environ., 30, pp.

3481.

12. R. Westerholm, U. Stenberg and T. Alsberg,

(1988), Atmos. Environ.,22, pp. 1005.

13. P.S. Pedersen, J. Ingwersen, T. Nielsen

and E. Larsen, (1980), Am.Chem. Soc., 14,

pp. 71.

14. Pollution Control Department, (1998),

Particulate matter abatement strategy for

the Bangkok Metropolitan Area report,

Volume I, Pollution Control Department,

Ministry of Science, Technology, and

Environment. Thailand.

15. International Agency for Research in

Cancer, (1993), IARC Technical Report on

Cancer in Thailand 1988-1991, IARC, 16,

Lyon , France.

16. H. Matsushita, K. Ching-Tang, M. Tabucanon

and S. Kootatep, (1987), Proceedings of

the third Joint Conference of Air Pollution

Studies in Asian Areas, Tokyo, pp. 304.

17. C. S. Davis, P. Fellin and R. Otson, (1987),

JAPCA., 37, pp. 1397.

18. J.C. Chuang, S.W. Hannan and N.K.Wilson,

(1987), Environ. Sci.Technol., 21, pp. 798.

19. US. Environmental Protection Agency, (1988),


The determination of Benzo(a)pyrene

(BaP) and other Polynuclear Aromatic

Hydrocarbons (PAHs) in ambient air using

Gas Chromatographic (GC) and High

Performance Liquid Chromatographic

(HPLC) Analysis, US. Environmental

Protection Agency, US. EPA. Method

TO-13.

20. D. L. Poster and J. E. Baker, (1996), Environ.

Sci. Technol., 30, pp. 341.

21. H. Matsushita, Y. Takahashi, S. Azuma, H.

Hiroi and T. Amagai, (1994)Proceeding of

the International Conference on Indoor Air

Quality, International Association for Indoor

Air Quality, Rothenfluh, Switzerland, pp. 236.

22. R. Niehaus, B. Scheulen and H. W. Durbeck,

(1990), Sci. Total Environ., 99, pp. 163.

23. S.O. Baek, M.E. Goldstone, P.W.W. Kirk, J.N.

Lester and R. Perry, (1991), Chemosphere,

22, pp. 503.

24. R.M. Harrison, D.J.T. Smith and L. Luhana,

(1996), Environ. Sci. Technol., 30, pp.825.

25. N. J. Bunce and H. G. Dryfhout, (1992),

Can. J. Chem., 70, pp. 1966.

26. R.M. Kamens, H. Karam, J. Guo, J.M. Perry

and L. Stockburger, (1989), Environ. Sci.

Technol., 23, pp. 801.

27. M. Jang and S. R. McDow, (1997), Environ.

Sci. Technol, 31, pp.1046.

28. R.M. Kamens, Z. Guo, J.N. Fulcher and

D.A. Bell, (1988), Environ. Sci. Technol., 22,

pp. 103.

29. M.R. Strommen and R.M. Kamens, (1997),

Environ. Sci. Technol., 31, pp. 2983.

30. P. Masclet, G. Mouvier and K. Nikolaou,

(1986), Atmos. Environ., 20, pp. 439.

31. C. J. Halsall, P. J. Coleman, B. J. Davis,

V. Burnett, K. S. Waterhouse P. Harding-

Jones and K. C. Jones, (1994), Environ.

Sci. Technol., 28, pp. 2380.


air6

Documents

Transcript of air6