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FORMATION AND ENANTIOSELECTIVE BIODEGRADATION OF THE ENANTIOMERS OF BROMOCHLOROACETIC ACID
Citation:
Wong, C S., A W. Garrison, W J. Jones, L. Howell, AND J Avants. FORMATION AND ENANTIOSELECTIVE BIODEGRADATION OF THE ENANTIOMERS OF BROMOCHLOROACETIC ACID. Presented at 21st Annual Society of Environmental Toxicology and Chemistry Meeting, Nashville, TN, November 12-16, 2000.
Impact/Purpose:
Elucidate and model the underlying processes (physical, chemical, enzymatic, biological, and geochemical) that describe the species-specific transformation and transport of organic contaminants and nutrients in environmental and biological systems. Develop and integrate chemical behavior parameterization models (e.g., SPARC), chemical-process models, and ecosystem-characterization models into reactive-transport models.
Description:
Bromochloroacetic acid (BCAA) is formed by chlorination of drinking waters containing naturally occurring bromide. This haloacetic acid is a concern to public health because of suspected carcinogenicity and toxicity, and is a potential target of disinfectant byproduct regulations. BCAA is chiral, and its enantiomers may have different biological and toxicological properties from each other. The formation and biodegradation of BCAA in natural waters were studied to determine if these processes are enantioselective. Racemic quantities of BCAA were produced in drinking waters treated by chlorination and ozonation in a pilot drinking water plant, and in chlorinated laboratory waters containing humic acids (e.g., Aldrich, Suwannee) and bromide ions. This result implies that the chiral centers that may be present in humic substances are not involved in the formation of haloacetic acids. The biodegradation of BCAA was studied in laboratory incubations of natural waters from 5 rivers in northeast Georgia, as well as wastewater treatment plant effluent from the city of Athens, GA. BCAA degraded enantioselectively in all natural waters, with the same enantiomer degrading faster in all cases, over times ranging from weeks to several months. The fastest degradation rates were observed in the wastewater effluent. Enantioselective degradation is proof positive of biotransformation; in addition, our results indicate that microbial communities in natural waters have a common
enantioselectivity for the degradation of BCAA.