Toxaphene in Great Lakes sediments Cost-effective management, regulation, and remediation of the Great Lakes require knowledge of the relative magnitude of atmospheric and nonatmospheric toxic chemical inputs. R. Pearson and colleagues analyzed concentrations of toxaphene, a broad-spectrum pesticide, in dated sediment cores taken from three of the Great Lakes and from inland control lakes that receive inputs only from atmospheric sources. Results suggest that the dominant source of toxaphene to the Great Lakes is atmospheric input. Lake Michigan currently receives 30-50% of input from nonatmospheric sources. In the past, Lake Ontario and Lake Superior may have received nonatmospheric toxaphene source inputs. The authors estimated that the half-life degradation rate of toxaphene in sediment cores is about 50 years. (Environ. Sci. Technol., ,his iisue, pp. 3523-299
SEDIMENTS Pollutant remobilization Bottom-dwelling macrofauna, such as molluscs and crustaceans, influence the fate and transport of hydrophobic organic pollutants. L. Schaffner and co-workers did laboratory experiments to investigate bioturbation effects of macrobenthos on PAHs and PCBs. Upward and downward compound mobility increased in the presence of macrofauna. Pollutant fate and transport depended on compound-specific, physicochemical properties and the time of occurrence and duration of biota-contaminant interactions. Particle resuspension exposed pollutants to desorption and microbial degradation, whereas benthic mobilization of compounds to greater sediment depths exposed them to more intense reducing conditions. Results indicate that bioturbation strongly influences contaminant fate and that sediment-bound contaminants can be remobilized by biological activity1 {Environ Sci Technol. 1997, 31, 3120-25)
TOXICITY Toxic potential evaluated It is difficult to use single-species, laboratory-based toxicity test data to reliably predict toxic impacts associated with the presence of multiple contaminants in actual ecosystem field environments. L. E. Twerdok and colleagues used an integrated environmental assessment approach, with traditional and nontraditional assays, to evaluate the toxic potential of groundwater, contaminated with several probable carcinogenic heavy metals and halogenated
solvents and taken from a surficial aquifer in Maryland. The negative assay test results of the nine-month hazard assessment study—the Ames test and several other tests of mutagenicity were negative—suggest that potential hazards posed by low concentrations of a complex mixture of chemicals may not be manifested at environmentally relevant concentrations. {Environ. Toxicol. Chem. 1997, 16(9), 1816-20)
WASTEWATER Residue oxidation method Wastewaters from fisheries have high nitrogen, organic matter, and salinity contents, and they cause serious environmental problems when these residues are not treated before disposal. C. Antileo and colleagues studied the use of pure oxygen in conjunction with a combined anaerobic and aerobic bacterial treatment method to process fisheries wastewater, which was high in ammonium and organic matter. Growth rates of nitrifying bacteria and bacteria that degrade organic matter were measured. During a one-week period organic matter content was reduced by 75% but oxidation of ammonium to nitrate and nitrite was only 20% complete Within an initial 30-hour period nitrifying bacteria significantly decreased in concentration an indication that high concentrations of ammonium may lyse bacteria or limit bacterial nutrition (Biotechnol lett 1997 29(3) 241-44)
Selenium cleanup Waterfowl have been deformed or killed by selenium-contaminated agricultural drainage water in the San Joaquin Valley in California. Se-
5 4 6 A • VOL. 31, NO. 12, 1997 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
lenium is present as soluble oxyanions, selenate, and selenite, which bioaccumulate and are toxic at low levels. M. E. Losi and W. T. Frankenberger, Jr., studied the use of Enterobacter cloacae for bioremediation of seleniferous waters. Results of laboratory experiments with the bacterium demonstrated removal of 61.5-94.5% of soluble selenate at contaminant concentrations of 13-1266 pM. Concomitantly, selenite and nitrate oxyanion levels were reduced. The authors suggest that development of cin efficient and costeffective a. biolocficcil flow reactor thcit uses E cloacae a.s a. bioremediciis compatible with placement of drainage water flow systems through wetland cells (Avvl Environ Microbiol 1997 63(81 3079-84)
Wetland performance The use of natural and constructed wetlands for treatment of wastewater has been documented and, in view of low capital, maintenance, and energy costs, is becoming more popular. J. Stober and colleagues evaluated the wastewater treatment performance of an evolved wetland that received treated sanitary wastewater originating from the nonnuclear portions of a nuclear power plant. Organic loading during the study was low. Removal of biochemical and chemical oxygen demand, total suspended solids, ammonium, nitrate, phosphate, and sulfate was monitored. The wetland provided excellent denitrification and removal of phosphate and sulfate. Moderate changes in biochemical and chemical oxygen demand, total suspended solids and ammonia WPT*e observed. These results further demonstrate the potential use of wetlands for control of nonpoint source runoff (Water Environ. Res 1199 66 991-681
Contributors: Michael Brauer, University of British Columbia, Vancouver; Brian Eiizer, Connecticut Agricultural Experiment Station, New Haven, Conn.; 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 Margaree Whittaker, NSF International, Ann Arbor, Mich.
