Physical and chemical factors that influence the anaerobic degradation of methyl parathion in sediment systems

摘要

AbstractThe 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