Abstract |
The kinetics of disappearance of methyl parathion (0,0-dimethyl-0-p-nitrophenyl phosphorothioate) were studied in anaerobic sediment samples in the laboratory as a function of methyl parathion concentration, pH, and Eh. The disappearance of methyl parathion is described by first-order kinetics and amino methyl parathion (0,0-dimethyl-0-p-aminophenyl phosphorothioate) was identified as a reduction product. In the strongly reducing sediments, the half-lives were on the order of a few minutes. In water isolated from the sediment, no reaction could be detected over the period of a week. Also, there is no apparent correlation between the first-order disappearance rate constants and the pH of the sediment samples. In heat-sterilized sediments, the disappearance rate constants are retarded about two orders of magnitude relative to nonsterile sediments. In chemically treated sediments, first-order disappearance rate constants are comparable to those in the nonsterile system. (Copyright (c) Pergamon Journals Ltd., 1986.) |