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Indexed by:期刊论文

Date of Publication:2014-10-07

Journal:ENVIRONMENTAL SCIENCE & TECHNOLOGY

Included Journals:SCIE、EI、PubMed、PKU、ISTIC、Scopus

Volume:48

Issue:19

Page Number:11277-11285

ISSN No.:0013-936X

Abstract:Successive sulfoxidation is widely recognized as a general characteristic of the metabolism of chiral or prochiral thioethers, producing sulfoxides, and sulfones. However, information related to the stereochemistry of this process in soils is rare. In this study, the biotic tranformation of the insecticide fenamiphos (a model thioether) was followed over two months in three soils, through separate incubations with fenamiphos parent, the sulfoxide intermediate (FSO), the sulfone intermediate (FSO2), and their respective stereoisomers. The results showed that the successive sulfoxidation involved oxidaton of fenamiphos to FSO and subsequently to FSO2 as well as diastereromerization/enantiomerization of FSO, all of which were primarily biotic and stereoselective. The concomitant hydrolysis of fenamiphos, FSO, and FSO2 to phenols that occurred at lower rates was biotically favorable, but not stereoselective. The sterochemistry of this successive sulfoxidation transferred principally through two parallel systems, R(+)-fenamiphos --> SRPR(+)-/SSPR(-)-FSO --> R(+)-FSO2 and S(-)-fenamiphos --> SRPS(+)-/SSPS(-)-FSO --> S(-)-FSO2, between which unidirectional intersystem crossing occurred at FSO via isomeric conversions and created a system of S(-)-fenamiphos --> SRPR(+)-/SSPR(-)-FSO --> R(+)-FSO2. This pattern acocunts fo rhte enrichment of the intermediates SSPR(-)-/SSPS(-)-FSO and R(+)-FSO2 that are toxicologically close to the highly toxic S(-)-fenamiphos, associated with soil application of fenamiphos. Selective formation/depletion of these intermediate stereoisomers leads to dramatic variations in the ecotoxicological effects of the thioether insecticide.