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
water, which presumes that soil bioavailability is identical to that of arsenic in drinking water. Noting that the equal-availability assumption of arsenic may not be valid, A. Davis and colleagues evaluated mineralogic controls on the bioavailability of arsenic in smelter-impacted soils. They proposed that the lower bioavailability of arsenic in soils near Anaconda, Mont., smelters may be related to arsenic's location in lesssoluble mineral phases. Specific examples include arsenic oxide-metal and phosphate phases. The authors attributed the site's low bioavailability of arsenic in soil to the lower solubility of these arsenic-bearing phases, inaccessibility of included arsenic, and kinetics of dissolution. {Environ. Sci. Technol. 1996, 30(2), 392-99)
Lead bioaccumulation Organolead compounds such as alkylleads from gasoline combustion have concentrated in mussel populations along the eastern Adriatic Coast. N. Mikac and colleagues evaluated the alkyllead levels and the relative bioconcentration of specific alkyllead species in mussels. They found organolead compounds occurred at levels between 0.1 and 45 ppb (wet weight). Tetraalkyl, trialkyl, and cKalkyl species occurred at maximum levels of 45, 32, and 9 ppb, respectively. They conclude that organic lead levels are better indicators of pollution than total lead given the number of other potential lead sources in the environment. Results show that the bioconcentration rate of organolead species from seawater was lower than that of total lead, which suggests that mussels are not as efficient bioaccumulators of organic lead relative to total lead. {Environ. Sci. Technol. 1996, 30(2), 499-508)
Tracking dioxins in an English pasture Atmospheric transport and deposition are considered important mechanisms in the dispersal of polychlorinated dibenzodioxins and dibenzofurans (PCDD/F) throughout the environment. L-0. Kjeller and colleagues studied the historical data on vegetation, which they used to infer changes in atmospheric deposition of PCDD/F from 1861 through 1993. Vegetation samples from an undisturbed pasture in southeast England have been collected and archived since 1861. Five-year composite samples were prepared and analyzed for PCDD/F. Concentrations of these compounds in the vegetation remained constant until 1945, rose to a peak in the mid-1960s, declined, then reached a lower peak in the late 1970s, and finally declined through the last sampling period in 1993. The authors infer that the peaks may be the result of byproducts of the production of chloro-aromatic compounds, superimposed on a background of dioxins from combustion sources. {Environ. Sci. Technol., this issue, 1398-1403)
Lead dissolution in the stomach decreased significantly as pH rose from 1.3 to 2.5, and arsenic solubility also decreased but not as dramatically. Lead was preferentially adsorbed and precipitated relative to arsenic in the near-neutral conditions of the small intestines. The method also can estimate lead and arsenic bioavailability in soils for risk assessments. The authors note that the test is designed to evaluate lead and arsenic bioavailability in the absence of animal study results. {Environ. Sci. Technol. 1996, 30(2), 422-30)
Lead bioavailability The form and solubility of lead and site-specific soil conditions are believed to affect lead bioavailability. M. V. Ruby and colleagues tested lead and arsenic for bioavailability using an in vitro, physiologically based, extraction-designed representative of human gastrointestinal parameters. Their results for lead correlated significantly with results from a Sprague-Dawley rat model. They predicted arsenic bioavailability that was comparable to results from rabbit and primate models.
MEASUREMENTS Analyzing VOCs in blood Standard methods for analyzing volatile organic compounds (VOCs) in aqueous systems do not work well for analyzing VOCs in small volumes of blood. F. St. Germain and colleagues developed an inertial spray extraction interface that allows VOC analysis in blood without sample pretreatment. The aqueous sample is sprayed downward through a nozzle
generating an aerosol, which allows the VOCs to equilibrate rapidly between gas and liquid phases. Gasphase VOCs are swept by a countercurrent flow of helium through an off-axis port and into a jet separator. This leads to an ion trap mass spectrometer for detection and quantification. Detection limits following injection of 1 mL of aqueous sample were
