RESEARCH WATCH
AIR QUALITY Oxygenated fuels EPA mandated oxygenated fuel use for areas that did not meet the national standard for the ambient level of carbon monoxide. D. M. Mannino and R. A. Etzel evaluated the mandate's effectiveness by comparing changes in CO levels in 11 western states between 1986 and 1992. They compared areas that used oxygenated fuel in wintertime with areas that did not. All areas showed decreases in CO concentration during winter, but the areas that used oxygenated fuel showed a statistically significant greater decrease (21% average reduction vs. 10%). All areas had CO concentration decreases in summer, when no oxygenated fuel was used, but no significant differences were noted. The summertime results support the hypothesis that the observed wintertime differences are likely the result of oxygenated fuel use. (/. Air Waste Manage. Assoc. 1996, 46, 20-24)
Effects of load reduction on bioaccumulation T. P. Traas and coworkers developed an integrated fate and bioaccumulation model for tributyltin (TBT) for a freshwater lake. They studied the effects of a load reduction scenario following the 1990 Dutch restriction on the use of antifouling paints containing TBT. They conducted a comprehensive field sampling program that incorporated mechanisms for TBT accumulation in sediments and biota and for food chain transfer into the model. The model predicted a rapid decrease in TBT levels in water, suspended matter, and zebra mussel populations following decreased loading. A much slower reduction was predicted for sediment, chironomids, amphipods, and benthivorous fish. Although insufficient reliable data contributed to high uncertainty in some predictions, the authors calculated a high risk of TBT bioaccumulation for fish and zooplankton in marinas even during load reduction. {Environ. Sci. Technol. this issue, 1227-37)
GREEN CHEMISTRY Plastic blends Designing polymers Considerable effort has gone into Polyesters are attractive for the design of biodegradable polymers because they can be biodegraded, and many of the monomers used to form them can be obtained from renewable resources. U. Witt and colleagues synthesized copolyesters by the polycondensation of 1,2-ethanediol, 1,3propanediol, 1,4-butanediol, sebacic acid, adipic acid, and terephthalic acid. They were able to synthesize copolyesters containing aliphatic and aromatic acids that combined microbial degradability and favorable physical properties. The authors also found that at 60 °C, biological degradation was accompanied by chemical hydrolysis, but at room temperature, degradation was caused solely by microbes. (J. Environ. Polym. Degrad. 1995, 3(4), 215-23)
engineering plastic blends that combine renewable materials with useful processing properties. S. H. Imam and co-workers prepared injectionmolded composites of poly(|3-hydroxybutyrate - co - pV hydroxyvalerate) (PHBV) with native cornstarch and starch coated with poly(polyethylene oxide) (PEO). They tested the biodegradability of these composites in municipal activated sludge. Although all composites degraded, the samples without PEO all degraded similarly: Tensile strength and elongation deteriorated quickly. The relative rates of mechanical property loss were highest for PHBV followed by starchPHBV and PEO-coated starch-PHBV. Composition changes were measured by FT-IR spectroscopy. {]. Environ. Polym. Degrad. 1995, 3(4), 205-13)
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Developing biodegradables M. van der Zee and co-workers studied the biodegradability of oxidized starch and inulin in relationship to the degree of oxidation to dialdehyde derivatives. Biodegradation was measured by oxygen consumption and mineralization to carbon dioxide. The authors found that a higher degree of oxidation of dialdehyde starch and dialdehyde inulin derivatives resulted in a lower rate of biodegradation. A more pronounced biodegradation rate decrease was seen in the case of inulin. The authors attributed this to changes in the polymer structure, the result of intra- and intermolecular acetal formation. The polymers adopted different conformations and were less susceptible to microbial attack. (/. Environ. Polym. Degrad. 1995, 3(4), 23542)
GROUNDWATER Water table management Nitrate movement into groundwater beneath agricultural fields can be controlled by increasing the height of the water table, which enhances denitrification. However, denitrification releases nitrous oxides, which are greenhouse gases. B. A. Kliewer and J. W. Gilliam studied water table management on the Atlantic Coastal Plain of North Carolina. They concluded that increasing the height of the water table by 30 cm significantly increased denitrification, decreased nitrate impact on groundwater, and only slightly increased nitrous oxide emission. {Soil Sci. Soc. Am. J. 1995,59, 1694-701)
HEAVY METALS Arsenic bioavailability Superfund risk assessment guidelines for cleanup of mining-related arsenic contamination are predicated on soluble arsenic in drinking
0013-936X/96/0930-U6AS12.00/0 © 1996 American Chemical Society
