longer extraction times or greater microwave power. The authors reported detection limits of 1 ng/g for a 1-g sediment sample. Analysis of certified reference material agrees with reported values. {Anal. Chem. 1995, 67(23), 4250-54)
POLICY
contain multiple hazards such as landfills, hazardous waste sites, and chemicals plants. They tested the hypothesis with two data sources: the Department of Commerce's American Housing Survey and surveys conducted by the authors in 20 stressed environments. Analysis of these data sets revealed no gender differences in risk perception. (Risk Analysis 1995, 15(4), 503-11)
ISO standards N. Roht-Arriaza studied the effect of private laws such as the International Organization for Standards' ISO 9000 standard on the environment, tracing the development of the current ISO standard-setting effort. She found private law is more efficient and protects the environment to a greater degree than do treaties. Private environmental standards shift the cost of regulation to producers and promote transboundary environmental compliance, and must assume a role in international and regulatory settings, she asserts. (Ecology Law Quarterly 1995, 22, 479-539)
Discounting the future Conventional economic discounting for long-term projects minimizes future environmental risks because the net present value of total costs diminishes exponentially with project lifetime. For instance, the Waste Isolation Pilot Project (WIPP) in New Mexico is expected to store high-level radioactive waste for a million years and will cause as many as 5000 deaths in that time. Nevertheless, estimated health costs are very low, because most of the deaths occur in future generations. E. Kula describes a social discounting method for evaluating future costs that discounts project health costs equally for each generation. The method predicts health costs for WIPP 100,000 times higher than does conventional discounting. (.Environ. Management 1996, 20(1), 81-87)
RISK Gender perceptions M. R. Greenberg and D. F. Schneider tested the hypothesis that no differences in risk perception exist among males and females living in stressed neighborhoods, which are areas that
SEDIMENTS Toxicity testing C. E. Schlekat and colleagues developed standardized 10-day toxicity tests for estuarine and marine sediments that evaluate the sediment quality with a range of contaminants and concentrations. Three species of amphipods were chosen for these tests: Ampelisca abdita, Eohaustorius estuarius, and Leptocheirus plumulosus. The study was designed to observe test results from several laboratories. They established an effective method among the laboratories to discriminate between control and moderate- to high-contaminant concentrations. However, results were more variable for low contaminant levels in the sediments. (Environ. Toxicol. Chem. 1995, 74(12), 2163-74)
Whole-sediment toxicity Studies have shown that two species, an amphipod (Hyalella azteca) and a midge (Chironomus tentans), are efficient indicators of whole-sediment toxicity. D. S. Becker and colleagues evaluated the relative performance of these two species in assessing fresh-water sediment toxicity. The lethal endpoint, biomass, and body length were assessed when the two species were used to evaluate the same sediments. Even though there were substantial differences between species, they were able to discriminate between relative toxicity of the sediments. (Environ. Toxicol. Chem. 1995, 74(12), 2089-94)
WASTEWATER Cadmium effects on sludge Heavy metals in municipal wastewater are toxic to activated sludge treatment systems, and migration of these metals to anaerobic sludge di-
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gestion systems can prevent proper reduction of secondary and primary sludge. S. K. Bhattacharya and colleagues investigated the effects of bioavailable cadmium on anaerobic systems to determine the relationship between cadmium concentration and sludge activity. Anaerobic acetate enrichment stock cultures were fed various concentrations of cadmium and incubated. The authors measured total suspended solids, free dissolved cadmium, total soluble cadmium, and gas production. Results indicated a correlation between free dissolved cadmium and inhibition of gas production, although total soluble cadmium did not correlate well with inhibition of gas production. Increased total suspended solids appeared to overcome cadmium's inhibitory effects. (Water Environ. Res. 1995, 67(7), 1092-94)
Nitrogenous BOD removal As effluent standards for nitrogen and ammonia become increasingly tightened, removal of nitrogenous biochemical oxygen demand (BOD) from municipal wastewater becomes more important. Numerous treatment systems currently are used to remove nitrogenous BOD. D. Parker and colleagues evaluated a trickling filter as a nitrification step in the tertiary treatment system for rernoving nitrogenous BOD. A two-year study was done in Sweden to determine the effect of operating variables on nitrification rates. Results indicated that two-stage, alternatingfilter operation provided higher nitrification rates and lower effluent ammonia. The authors attribute this primarily to enhanced maintenance of nitrifying biofilm from a more uniform exposure to high influent ammonia concentrations. The twostage operation also mitigated the effect of influent suspended solids on the suppression of nitrification rates. (Water Environ. Res. 1995, 67(7), 1111-18) Contributors to Research Watch are Brian Eitzer, Connecticut Agricultural Experiment Station, New Haven, CT; Stephen Geiger, Remediation Technologies, Inc., King of Prussia, PA; Vincent Hand, Miami University, Institute of Environmental Sciences, Oxford, OH; Richard Hurst, CHEMPET Research Corp., Moorpark, CA; Louis Kovach, Ecolife Associates, Wilmington, DE; and Margaret Whittaker, NSF International, Ann Arbor, MI.
