RESEARCH WATCH
ASSESSMENTS Biological inventories Few studies have evaluated the use of biological inventories and computer databases in environmental assessments (EA). Luis A. BojorquezTapia and co-workers evaluated an EA covering two states. Data in existing biological inventories were biased with respect to species and locations, and a quarter of the records had missing or unusable location information. Taxonomic data and georeferenced collection site are the two essential fields in any database. Other information is often useless, especially when the EA objective is to highlight likely sites of conflict between conservation and development. {Environ. Manage. 1994, 18(5), 775-85)
BIOREMEDIATlON PCB degradation The ability to predict the degradation of polychlorinated biphenyls (PCBs) by indigenous microorganisms under natural conditions can provide critical information for assessing remediation potential within an ecosystem. Kenneth M. Fish and Jan M. Principe developed a method to study the fate of Aroclor 1242 in a simulated Hudson River ecosystem. Test tube microcosms of upper Hudson River sediments were spiked with Aroclor 1242. No nutrients were added. Distinct aerobic and anaerobic compartments developed within 2 to 4 weeks. Aerobic degradation as well as anaerobic reductive dechlorination occurred, resulting in extensive PCB biodégradation within 140 days, compared to autoclaved controls. The results demonstrate that natural environments have the potential to degrade PCBs at relatively rapid rates, and they provide a unique system to study the fate of contaminants in river sediments. (Appl. Environ. Microbiol. 1994, 60(12), 4289-96)
Declining biodegradability Some field studies suggest that biodegradability decreases as the time a chemical is in soil increases. Paul B. Hatzinger and Martin Alexander confirm this in a laboratory study. When phenanthrene or 4-nitrophenol was aged in loam or muck for long periods—up to 315 days—biodégradation rate and extent decreased with amount of time aged. The chemicals also became more resistant to extraction using mild solvent during that time. The results suggest that the effectiveness of bioremediation of chemicals in soils may decrease with aging. {Environ. Sci. Technol. 1995, 29{2), 537-45).
CONTAMlNANTS Telephone pole PAHs Utility and telecommunications poles are generally pressure treated with pentachlorophenol prior to installation. In 10-15-year cycles these poles are treated in situ with a mixture of creosote and chlorophenols by a variety of techniques. Michael Wan conducted a study of surface water and sediment contamination of polycyclic aromatic hydrocarbons (PAH) in ditches adjacent to these poles. Average concentrations of total PAH were measured upstream, adjacent to, and downstream of the poles. Average concentrations 4 m upstream were 2.68 pg/L for surface water and 1.33 mg/kg for sediment, concentrations adjacent to the poles were 551.7 pg/L for surface water and 15.0 mg/kg for sediments, and concentrations 4 m downstream were 23.2 pg/L for surface water and 3.27 mg/kg for sediments. These concentrations most likely do not represent an acute toxicity to fresh water and marine aquatic vertebrates and salmonids; however, there is little information available on the chronic impact of the detected PAH to these species. {]. Environ. Qual. 1994, 23, 1297-1304)
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GEOCHEMlSTRY Swamp methane How does oxidation influence stable carbon isotopic compositions (e.g., delta 13C) of methane emitted from swamps? Happell, Chanton, and Showers investigate this question in two seasonally flooded Florida swamps (St. Marks National Wildlife Refuge and Everglades Cypress Dome). Their results indicate that 13 C, is enriched in methane emitted from swamps relative to sedimentary methane. The observed enrichment is hypothesized to result from the oxidation of methane as it diffuses from the sediment to the atmosphere. To test their theory, the authors devised laboratory experiments to evaluate carbon isotope fractionation during methane oxidation and transport. Experimentally determined carbon isotope fractionation factors average 1.020. The results support their hypothesis of 13C enrichment in methane gas during diffusion and oxidation in sediment as observed in the Florida swamps. {Geochim. Cosmochim. Acta 1994, 58, 4377-89)
LAW CAAA shortcomings Technology-based standards are inflexible and stifle innovation; residual risk standards ignore risks other than cancer and are based on an imprecise science, concludes Bradford C. Mank in discussing the 1990 Clean Air Act Amendments. The Clean Air Act Amendment's sections 112(d) and 112(f) direct EPA to regulate 189 hazardous air pollutants. Specifically, they require technologybased emissions standards for categories and subcategories of industries that are major sources of air pollutants. Residual risk emission standards also are mandated in areas where technology-based stan-
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