An environmental fate study of methoxychlor using water-sediment model system.
Agricultural waste water containing pesticides can reach the sea via rivers and estuaries, including brackish lakes. We studied the metabolic fate of methoxychlor [MXC; 1,1,1-trichloro-2,2-bis(4-methoxyphenyl)ethane] in a model system consisting of sediment and associated water collected from two sampling sites: a brackish lake and a freshwater river. MXC degraded rapidly and was finally mineralized in both sediment systems. The first step of degradation was dechlorination to yield 1,1-dichloro-2,2-bis(4-methoxyphenyl)ethane [de-Cl-MXC] or CN-replacement to yield 2,2-bis(4-methoxyphenyl)acetonitrile [MXC-CN], followed by O-demethylation. Although the metabolites were common to the two sediments, the dynamics of the metabolites over time were clearly distinct. In the brackish lake sediment, de-Cl-MXC accumulated transiently, whereas in the river sediment, it was rapidly converted to its demethylated metabolite. We also found that dechlorination and CN-replacement proceeded in autoclave-sterilized river sediment. In the river sediment, the abiotic reaction mediated by abundant humic acid and low oxygen level also appeared to contribute to the overall MXC metabolism.
Laboratory of Metabolism, Chemistry Division, The Institute of Environmental Toxicology, Joso, Ibaraki, Japan. masuda@iet.or.jp
Minoru
M
Masuda
Koji
K
Satsuma
Kiyoshi
K
Sato
D001673:Biodegradation, Environmental; D004777:Environment; D019015:Geologic Sediments / Q000382:microbiology; D007306:Insecticides / Q000378:metabolism*; D007700:Kinetics; D008731:Methoxychlor / Q000378:metabolism*; D014867:Water; D014871:Water Microbiology
D007306:Insecticides; D014867:Water; D008731:Methoxychlor