ing of soils during compound sequestration reduced its recoverability and bacterial mineralization. (Environ. Toxicol. Chem. .997, ,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 quadruplle 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.. this 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 reactant 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 were greater for children born in metropolitan areas with high particulate concentrations than for those born in areas with low particulate concentrations. (Environ. Health Perspect. t199,105(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
CIRCLE 1 ON READER SERVICE CARD
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A novel immunoassay monitor Inexpensive monitoring devices are needed to confirm compliance with EPA-mandated heavy-metal contaminant loading reductions in aqueous waters. M. Khosraviani and colleagues developed a novel selective immunoassay for cadmium. The rapid assay is based on a monoclonal antibody that recognizes Cd2*-EDTA complexes but not free EDTA and can detect Cd2* at concentrations ranging from 7 to 500 ppb. The assay is not affected by interference from commonly encountered cations such as Ca2* Na* and K*. Other metals likely to be present in natural waters including Fe3\ Pb2t Zn2* Ni 2 \ In3* Mn2* and Mg2\ do not create Cd2* measurement problems at relevant
difficult to perform. D. Chambers and co-workers developed an ionstore, time-of-flight mass spectrometer that preconcentrates samples and is designed for real-time monitoring of trace-level changes of VOCs and semivolatile compound concentrations in large-volume air samples. Favorable measurements of trace concentrations of several aromatic and chlorinated compounds were performed. The system has analytical detection limits typically in the low parts-per-billion volume rflflSC 3.0.(1 a 2000-m/Am mass resolution. Results are shown for analysis of several trace aromatic and chlorinated compounds and demonstrate tvoical system capabilities (Anal Chem 1997 69(18) 3780-90)
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response at concentrations greater II Id 11 1 U IVI. \ C / ' V11 \Ji I. iJL/1. I CL/111 i\Jt.,
this issue, pp. 137—42)
A. T. Yeung and colleagues evaluated the potential use of electrophoresis of clay particles for plugging liner leaks without prior removal of impoundment contents. They found that an imposed direct-current electric field caused clay particles to migrate toward leaks and form a seal. Effects of clay type, particle concentration in suspension, leak size, and electric-field strength on leak closure success were evaluated. The feasibility for use and limitations of the method at full scale are discussed. The authors suggest that even if sealing efficiency in field applications is poor the method could still be used in an economical manner for locating leaks in subsurface liners (J Environ Ens (NY) )997 723(10] 993-1001)
MEASUREMENTS
Rapid screening methods are needed for heavy metals in groundwater. A proof-of-concept field evaluation made it possible for J. Herdan and co-workers to evaluate the performance of an electrochemical probe for in situ detection of copper, cadmium, lead, and zinc in groundwater. The novel probe, consisting of a micrographically fabricated iridium ultramicroelectrode array sensor, a custom-built miniaturized potentiostat, and a microcontroller, detected the metal contaminants at part-per-billion levels in a proof-ofconcept field demonstration at a metals-contaminated landfill site The authors concluded that the method is aooropriate for initial rapid fieldbaspri scrppning of rnntaminated
contaminant concentrations How2
Groundwater metals probe
wcic t p r h n i n u o c (En\/imn
EDTA metal solubilization When present as a contaminant, ethylenediaminetetraacetic acid (EDTA) may solubilize metals in river sediments. S. J. Gonsior and colleagues developed a statistically significant, no-observed-effect-level (NOEL) standard for EDTA solubilization of nickel, cobalt, copper, zinc, cadmium, iron, and lead in simulated river-sediment microcosms. If EDTA concentration is below the corresponding NOEL standard for each metal observable metal solubilization does not occur. Concentrations of EDTA present as a contaminant in actual river-sediment samples were found to be below NOEL levels leading the authors to conclude that metal solubilization by EDTA complexation was unlikelv to be significant in tested river waters The method can be aDDlied to other water systems (J Environ Qual 1997 26 957-66)
WASTEWATER
VOC detection method
Sludge denitrification
The Clean Air Act requires detection of VOCs, often in trace amounts in complex sample matrices. Real-time measurement of trace-level chemical species concentrations in these environments has been particularly
Nitrate ion, often found in industrial wastewater discharges, is a soluble and easily transportable primary drinking water contaminant that must be removed. Activated sludge removes nitrate, but denitrification
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can be inhibited by formation of nitrite ion, a reaction intermediate. In laboratory-scale experiments, C. Glass and co-workers evaluated the influence of initial nitrite concentration, pH, and suspended solids on the sludge denitrification process. Results indicate that extensive denitrification with little inhibition occurs at pH levels of 8 or higher, but the process is inhibited at lower pH levels, even when nitrite concentrations are low. Suspended solids in industrial wastewater discharges did not appear to affect nitrite inhibition of denitrification for conditions studied (Water Environ Res 1997 69(6) 1086-93) Contributors: Michael Brauer, University of British Columbia, Vancouver; Brian Eitzer, 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, Canada; Raeuryy Town, Queen's University yf Belfast, Northern Ireland; and Margaret Whittaker, NSF International, Ann Arbor, Mich.
JAN. 1, 1998/ENVIRONMENTAL SCIENCE & TECHNOLOGY/ NEWS • 4 9 A
