Monitoring organochlorine pollutants A new method to quickly and efficiently measure organochlorine compounds in solids has been demonstrated. B. Strandberg and colleagues used a semipermeable membrane device, essentially a thin film of lipid enclosed in a polymeric membrane, to analyze organochlorine compounds in compost and surrounding air. Several devices were buried in or suspended above active compost heaps. After a four-week sampling period, total accumulations of PCBs and pesticides in the lipids were determined. Amounts detected were proportional to quantities found in the compost by more time-consuming, conventional measurement methods. This novel approach provides a simple way to semiquantitatively sample these compounds and can be used in screening studies and analysis of pollutant volatilization. {Environ. Sci. Technol., this issue, pp. 2960-65)
Statistical methodology The Clean Air Act Amendments of 1990 require human health risk assessments posed by acute or chronic exposures to hazardous air pollutants. However, it is difficult to make such assessments when available response data are uncertain or lack clarity. D. J. Guth and colleagues describe a stratified, categorical regression technique that provides a way to address this issue. The procedure combines inhalation exposure studies and analyzes response data expressed as ordinal severity categories (e.g., no effect, adverse effect, severe effect). They illustrated the method by analyzing prior studies of tetrachloroethylene's acute effects in rats, mice, and humans and developed an exposure response function for acute exposures, which resulted in setting human exposure limits. {Risk Analysis 1997, 17, 321-32)
WASTEWATER Metals biosorption Biosorption of heavy metals by biological materials is a potentially attractive method for treatment of industrial wastewaters. However, in
complex mixtures of contaminants, the presence of other metals can interfere with the uptake of targeted heavy metals and can affect the efficiency of the cleanup process. M. M. Figueira and co-workers studied the interference of iron with the uptake of cadmium by Sargassum seaweed, which can bind more than 10% of its dry weight in cadmium ions. The interference effect on the sorption behavior of the biomass was analyzed by deriving three-dimensional equilibrium sorption isotherms for the two-metal system. The authors demonstrate how equilibrium metal uptake studies can elucidate biosorption mechanisms and optimize system applications. [Biotechnol. Bioeng. 1997, 54, 344-50)
Nickel removal Industrial discharges of nickel, known for its toxicity to higher organisms, have increased dramatically, and more effective wastewater treatment methods are needed. G. Basnakova and L. E. Macaskie used columns loaded with polycrystalline hydrogen uranyl phosphate bound to immobilized cells of Citrobacter sp. for quantitative nickel removal and recovery from aqueous solutions. The influence of pH, temperature, and flow rate on column nickel ion uptake efficiency and the selective recovery of nickel using citrate or tartrate were studied. The columns functioned effectively through five cycles of uptake and regeneration without any significant decrease in removal capacity. The novel method enables continuous removal of Ni2+ from aqueous wastes and metal recovery from concentrated solutions. {Biotechnol. Bioeng. 1997, 54, 319-28)
Novel nitrogen removal An anaerobic ammonium oxidation (Anammox) process for converting ammonium in wastewater to nitrogen gas under anaerobic conditions has recently been discovered. M. Strous and co-workers report that the treatment process uses nitrite as the electron acceptor. Complete removal of ammonium from wastewater requires conversion of some of the ammonium to nitrite before application of the Anammox process. Results show that, although the Anammox process is inhibited by the presence of oxygen, the effect is reversible. Moreover, aerobic nitrifiers do not play an important role in the
Arsenic biogeochemistry analyzed The toxicity and biogeochemistry of arsenic in lake ecosystems is strongly influenced by its chemical form. Y. Sohrin and colleagues studied how prevailing conditions in Lake Biwa, a eutrophic lake in Japan, affect arsenic speciation. Seasonal variations in concentrations of arsenic species in the mesotrophic northern and eutrophic southern basins of the lake were observed. Within the euphotic zone, arsenite increased in spring and fall, dimethylarsinic acid became dominant in the summer, and, although always only present as minor fractions, measurable concentrations of monomethylarsonic acid, monomethylarsonous acid, and dimethylarsinous acid were observed. The total arsenic concentration in the euphotic zones remained constant yearround but increased significantly during the summer in the southern basin. Taken together with other observations, these results indicate that arsenic speciation is strongly influenced by phytoplankton metabolism, bacterial decomposition of organic matter, microbial reduction of iron and manganese oxides in sediments, and other biological processes. Eutrophication had a significant effect on the concentration and speciation of arsenic in lake water and may increase arsenic toxicity and its consequent impact on ecosystems. {Environ. Sci. Technol., this issue, pp. 2712-20)
process. Such information aids in the design of single-reactor ammonium removal systems and demonstrates the potential of the Anammox process for low-cost removal of ammonium from wastewater. [Appl. Environ. Microbiol. 1997, 63, 2446-48) Contributors: Michael Brauer, University of British Columbia, Vancouver; Brian Eitzer, Connecticut Agricultural Experiment Station, New Haven; Stephen Geiger, Remediation Technologies, Inc., King of Prussia, Pa.; Vincent Hand, Miami University, Institute of Environmental Sciences, Oxford, Ohio; Louis Kovach, Ecolife Associates, Wilmington, Del; Geoffrey Nobes, McGill University, Montreal; Raewyn Town, Queen's University of Belfast, Northern Ireland; and Margaret Whittaker, NSF International, Ann Arbor, Mich.
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