title: Initial test of the benchmark chemical approach for predicting microbial transformation rates in aquatic environments.
abstract: Using 2,4-dichlorophenoxyacetic acid methyl ester (2,4-DME) as a benchmark chemical, we determined relative pseudo-first-order rate coefficients for the 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-chlorobenzoate > 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.
authors.affiliation: Technology Applications, Inc., and Environmental Research Laboratory, U.S. Environmental Protection Agency, Athens, Georgia 30613, and Department of Microbiology and Institute of Ecology, University of Georgia, Athens, Georgia 30602.
authors.forename: T D
authors.initials: TD
authors.lastname: Newton
authors.forename: D K
authors.initials: DK
authors.lastname: Gattie
authors.forename: D L
authors.initials: DL
authors.lastname: Lewis