RESEARCH WATCH

ASSESSmEnT Bounding analyses Bounding analyses can be useful as simplified, conservative, quantitative analyses of environmental impacts, but when should they be used? R. E. Saylor and L. N. McCold considered whether such analyses impede or advance the purposes of the Na­tional Environmental Policy Act (ΝΕΡΑ). They reviewed four uses of bounding analyses: (1) insignificant impacts, (2) generic environmental documents, (3) programmatic ΝΕΡΑ documents, and (4) accidents. Be­cause bounding analyses require less detail, the researchers found that such analyses can be used earlier in planning, consistent with ΝΕΡΑ re­quirements. Bounding analyses should be used more widely and are preferable to vague, qualitative fore­casts that do not advance the pur­poses of ΝΕΡΑ, they conclude. (Envi­ron. Prof. 1994, 16, 285-91)

BIODEGRADATIOn Biofilm on plastics Biodégradation techniques that treat groundwater contaminated with low concentrations of benzene, toluene, ethylbenzene, and xylene (BTEX) are important for effective bioremedia-tion of gasoline and fuel spill sites. R. D. Neufeld and colleagues devel­oped a biofilm on plastic surfaces, using activated sludge inoculum and high nutrient conditions to address this need. Bioreactors consisted of cylindrical polymethylacrylate tubes with polypropylene packing. During a four-month period, the researchers biodegraded target organics—tolu­ene introduced in 10-20 mg/L con­centrations—in a continuous flow system. The study demonstrated the system's capability to degrade low levels of toluene and indicated that this capability can be extended to other BTEX compounds. [Water En­viron. Res. 1994, 66(7), 899-904)

SFE used to determine PCBs in fish tissue Supercritical fluid extraction (SFE) is replacing soxhlet extraction because it reduces solvent use, generates less waste, and increases through­put. R. Hale and M. Gaylor developed a method to apply SFE to the deter­mination of polychlorinated biphenyls (PCBs) in fish tissue. Lyophilized fish tissue is packed in the extraction vessel and a plug of neutral alumina is added. The PCBs are extracted from the matrix with unmodified C02

at 150 °C and 350 atmosphere, and the solid phase is trapped. The alu­mina in the extraction vessel retains the lipids so the solvent rinse of the trap can be directly analyzed by gas chromatography with electron cap­ture detection. The results show no significant differences compared to analyses using soxhlet extraction and gel permeation cleanup tech­niques. (Environ. Sci. Technol., this issue, 1042-47)

Improving solubility Biodégradation of hydrophobic hy­drocarbons in soils and sediments often is limited by compound solu­bility and lack of transport to the active metabolism site. Previous studies indicate that surfactants can help increase degradation by in­creasing aqueous-phase concentra­tions through either solubilization or desorption from soil or sediment surfaces. S. A. Churchill and col­leagues studied the addition of an oleophilic fertilizer (Inipol ΕΑΡ 22) or a rhamnolipid biosurfactant to buffered solutions of pure bacterial cultures and sparingly soluble hy­drocarbons. The oleophilic fertilizer also introduces nitrogen and phos­phorus. Both surfactants increased dispersion, emulsification, and min­eralization of hexadecane and octa-decane. In all cases, the oleophilic fertilizer was more effective than the rhamnolipid. Less mineralization occurred with aromatic hydrocar­bons (toluene and 2-methylnaphtha-

lene); again the oleophilic fertilizer was more effective. (/. Environ. Qual. 1995, 24, 19-28)

mEASUREmEnTS Trace organics Methods for on-site monitoring of trace levels of volatile organic com­pounds (VOCs) in water and wastewa­ter are needed to comply with envi­ronmental regulations. S. Bauer and D. Solyom report on a membrane in­troduction mass spectrometry (MIMS) system that should prove useful for such monitoring. Their system cou­ples a direct insertion capillary mem­brane to an ion trap mass spectrome­ter. For the VOCs listed in EPA method 524.2 (purge and trap GC/MS), detec­tion limits with 1 inL of sample were <1 ppb. An analysis for total triha-lomethanes could be conducted every six minutes with detection limits of 100 pptr. {Anal. Chem. 1994, 66(24), 4422-31)

Solid-phase microextraction Solid-phase microextraction (SPME), a useful new technique in environ­mental analysis, has been improved to allow for the quantitative transfer of volatile organic compounds from the sample matrix to the polymeric coated capillary. Z. Zhang and J. Pawliszyn describe an SPME device in which the polymeric coating is cooled by liquid carbon dioxide while the sample matrix is heated. The heated matrix enhances analyte volatilization, whereas the tempera­ture difference between the matrix and coating greatly magnifies the partition coefficient. This procedure allows quantitative transfer of the analyte, which, in turn, allows for lower detection limits in the subse­quent thermal desorption GC/MS analysis of the coated capillary. Re­sults are shown in which benzene, toluene, ethylbenzene, and xylene (BTEX) are completely recovered from 2 grams of clay or sand in 5

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minutes. Limits of detection for BTEX in clay with cooled SPME and ion trap GC/MS were <0.3 pptr. {Anal. Chem. 1995, 67(1), 34-43)

m o D E L I n G

Fate prediction The ability to predict the fate of contaminants in lakes allows the development of strategies for con­trolling those chemicals and miti­gating their impact. These predic­tions are best performed by mass balance models, which establish several compartments and model the transfer of contaminants among those compartments. D. Mackay and colleagues have developed one such model, which describes the transfer of chemicals among the atmosphere, land-based discharges, the water column, sediments, and biota. The model is applied to a specific case of PCBs in Lake On­tario, showing the time response of sediment and water column con­centrations to reduced loading sce­narios. (]. Great Lakes Res. 1994, 20(4), 625-42)

Soil lead near a battery recycling site Determining soil lead (Pb) sources in urban areas is difficult because of the number of, and long-term expo­sure of the environment to, anthropo­genic Pb sources. M. J. Small and colleagues employ a statistical method to distinguish Pb concentra­tions from a former automotive bat­tery recycling facility from urban background concentrations. Despite many assumptions that are built into the atmospheric model, such as fa­cility and background Pb are inde­pendent and log-normally distributed, each assumption is well-founded and supported with historical data in the region. Soil variables also may have an impact on Pb concentrations in soil. The results, an estimation of Pb concentration and distribution in soils near the battery recycling facility, agree with the observed distribu­tions. Geographic limits of sampling in residential areas are defined and cleanup responsibilities are deter­mined from the data. {Environ. Sci. Technol., this issue, 883-95)

POLICY Environmental justice Environmental justice and industrial redevelopment must be reconciled in order to promote urban economic and public health. D. A. McWilliams presents urban redevelopment as of­ten harming urban dwellers by demol­ishing affordable housing and increas­ing industrial pollution. But these negative impacts can be offset by cre­ating new jobs and remediating long-abandoned sites. Environmental jus­tice advocates and developers must establish a cooperative working rela­tionship to minimize costly, time-con­suming litigation and maximize in­dustrial redevelopment that benefits all members of the community. Ex­pected changes in Superfund will ne­cessitate further initiatives by those involved in urban redevelopment. (Ecol. Law Q. 1994, 21(3), 705-83)

R I S K Value of uncertainty The "How clean is clean?" argument vexes remediation efforts at many hazardous waste sites, and the inevi­table uncertainty of key parameters further complicates the question. M. E. Dakins, J. E. Toll, and M. J. Small couple Monte Carlo and value-of-information analyses to address these issues. A New Bedford Harbor, MA, Superfund site illustrates the value of including uncertainty in de­cision making. This method could save millions of dollars as compared with decision making based on a point estimate. (Environ. Toxicol. Chem. 1994, 13(12), 1907-15)

Perception differences Race and gender may play a role in determining perception of risk from possible environmental hazards. J. Flynn, P. Slovic, and C. K. Mertz gauged the effect of gender and race on perceiving environmental risk. A random sample of 1512 people were interviewed and asked to rate the public health risks associated with 25 hazards (such as nuclear power, cigarette smoking, and ozone deple­tion). Previous studies documented differences in risk perception between men and women, but Slovic's article identifies differences among races. Among the 25 hazards rated, non-whites judge all as being higher risk

Organic pollutant sorption on humic matter Coal combustion produces large, highly contaminated waste streams that can lead to sorption of pollutants onto sediment. But theoretical de­scriptions of the sorption processes are not well established. F-D. Ko-pinke, J. Porschmann, and U. Stott-meister investigated anthropogenic and natural humic materials from a coal wastewater pond and river sedi­ment as sorbents of hydrophobic solutes in aqueous media. Results indicate that differences between partition coefficients of coal and river sediment are small; the largest variations are observed for aniline because coal sediments have more strongly acidic centers or reactive carbonyl groups than do river sedi­ments. The work's major contribution is the development of a revised solu­bility parameter model that allows the estimation of sorption coeffi­cients for nonpolar solutes using octanol-water partition coefficients and the solubility parameter of the sorbent. (Environ. Sci. Technol., this issue, 941-50)

than do whites (especially white males), even when income, education, and political orientation are con­trolled. The authors contend that risk management and communication must consider these perceptions and equally serve people of color. (Risk Anal. 1994, 14(6), 1101-08)

Assessment software Risk assessment software often is expensive. The user inputs doses and responses, and the software churns out a slope factor that pre­dicts carcinogenicity or some other endpoint. C. N. Haas has developed a less expensive Excel spreadsheet package to develop dose-response models for experimental data. He uses carcinogenicity data from a chloroform study to create a multi­stage model and provides a graphic of a completed Excel spreadsheet. (Risk Anal. 1994, 14(6), 1097-1100)

WASTEWATER Algae removal Cost-effective technologies for re­moving algae from lagoon effluent

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