ing of soils during compound sequestration reduced its recoverability and bacterial mineralization. (Environ. Toxicol. Chem. .197, ,6[10), 2040-45)
BIODEGRADATION Predicting biodegradation If the biodegradability of chemicals can be modeled, then they can be designed with structures that are simultaneously optimized for intended use and disposal objectives. G. Klopman and M. Tu developed an expert system that predicts aerobic biodegradation products of organic chemical compounds. They linked the system to an artificial intelligence program, identifying molecular parent-compound substructures that may cause or inhibit degradation. Using the linked programs to successfully predict the biodegradability of 34 test compounds the authors confirmed predictions by comparing them with reported data Limitations of the method and data requirements are discussed The authors urge caution in using model predictions and stress the need to validate applications (Environ Toxicol Chem 1997 16(9) 1829-35)
BIOREMEDIATION Carbon tetrachloride cleanup There is growing interest in using indigenous bacterial populations to degrade hazardous compounds at contaminated sites. G. Jin and A. J. Englande, Jr., investigated the degradation kinetics of carbon tetrachloride by Pseudomonas cepacia in sediment samples under laboratory conditions that replicated typical environmental contamination. The oxidation-reduction potential, believed to be an important factor in controlling reaction progress was varied. The authors found that significant carbon tetrachloride decomposition occurred under negative oxidation-reduction potential conditions but biodegradation was negligible under positive conditions Results suggest that under favorable reaction conditions the compound can be partly converted to nonhalo-
Online water pollution biomonitor Biomonitors can be used to perform continuous in situ monitoring of river water quality during point source pollution events, but it has been difficult to obtain satisfactory performance. A. Gerhardt and co-workers tested a new online biomonitor for detecting copper pollution episodes in a flowing river. The system uses a quadruple impedance conversion technique that provides data about changes in behavior of Gammarus pulex when exposed to copper pollution peaks. Changes in the behavior patterns of chambered organisms in the presence of Cu2* correlated with the impedance recorded across each chamber of the monitor. The system may provide early warning about changes in water quality. The authors recommend the use of local native test organisms to minimize false alarms caused by inappropriate use of oversensitive species. (Environ. Sci. Technol..,his iisue, ,p. .50-56)
genated products. (Water Environ. Res. 1997, 69(6), 1094-99)
Trichloroethylene cleanup Trichloroethylene, a toxic compound frequently found in contaminated soils and groundwater, can be degraded by cometabolic processes involving the use of methanotrophic bacteria and a bacterial growth substrate, such as methane. If reaction conditions are unfavorable, toxic metabolites can be produced that inactivate the bacterial degradation process. In laboratory experiments, G. A. Walter and colleagues varied reactor designs and operating conditions in an attempt to optimize trichloroethylene degradation. Reactor design operating mode and tant feed rates were found to influence the extent of trichloroethylene contaminant degradation and bacterial inactivation by toxic metabolites (Water Environ Res 1997 69(6) 1066-74)
DRINKING WATER Cryptosporidium
testing
The ability of drinking water treatment plants to remove Cryptosporidium oocysts and protect public health depends critically on reliable test methods and data validation. P. Klonicki and co-workers reviewed 200 publications about Cryptosporidium analyses and found that none provided sufficient information on oocyst quality and quantity to allow the work to be reproduced by other investigators. They also showed that three different oocyst enumeration techniques hemacytometer, cellulose-acetate membrane collection
and well slide—gave widely varying results when applied to analysis of the same batch of oocysts. These issues raise questions about the utility of reported findings. Guidelines are suggested for documenting oocyst quality and specifying enumeration methods used. (J. Am. Water Works Assoc. .997, 89(9), ,7-103)
HEALTH Infant mortality-PM 10 link Although the relationship between infant mortality and particulate air pollution has been characterized in other countries, it has not been studied in the United States. T. J. Woodruff and co-workers evaluated the relationship between infant mortality and particulate air pollution among approximately 4 million infants living in 86 U.S. metropolitan areas with populations greater than 100,000. Statistically significant results indicate that risks of sudden infant death syndrome and respiratory mortality during the first two months of life greater for children born in metropolitan areas with high particulate concentrations than for those born in with low particulate concentrations (Environ Health Persvect 1997 105(6) 608-12)
LANDFILL Preventing liner leaks Leaks in geomembrane liners occur at hazardous and municipal solid waste landfills and surface impoundments and are difficult and costly to repair. At laboratory scale,
4 8 A • JAN. 1, 1998 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
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