Abstract |
Using 2,4-dichlorophenoxyacetic acid methyl ester (2,4-DME) as a benchmark chemical, the authors determined relative pseudo-first-order rate coefficients for butoxyethyl ester of 2,4-dichlorophenoxyacetic acid (2,4-DBE), methyl parathion, and methyl-3-chlorobenzoate in a diversity of microbial samples, including water, sediment, biofilm, and floating microbial mats collected from a laboratory mesocosm as well as from streams, lakes, and wetlands in Georgia and Florida. The decreasing order of reactivity for relative microbial transformation rates was 2,4-DBE>2,4-DME>methyl-3-chlorobenzene>methyl parathion. Half-lives of the chemicals varied about 60-fold depending on the chemical and microbial sample. Relative rate coefficients, however, typically varied only about threefold for field-collected samples. Relative rate coefficients determined with samples from a laboratory mesocosm were consistently low compared with the field sample data. Overall, the data indicated that microbial transformation rates of a chemical can be satisfactorily inferred for a wide variety of microbial habitats--such as water, biofilm, or a sediment--on the basis of its transformation rate relative to that of an appropriate benchmark chemical by using a single type of microbial sample. (Copyright (c) 1990, American Society for Microbiology.) |