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Title: DEHALOGENATION OF CHLOROACETANILIDE HERBICIDES BY THIOSULFATE SALTS

Author
item GAN, JIANYING - UC RIVERSIDE, CA
item WANG, QIQUAN - UC RIVERSIDE, CA
item Yates, Scott
item Koskinen, William
item JURY, WILLIAM - UC RIVERSIDE, CA

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2002
Publication Date: 4/16/2002
Citation: Gan, J., Wang, Q., Yates, S.R., Koskinen, W.C. and Jury, W.A. Dehalogenation of Chloroacetanilide Herbicides by Thiosulfate Salts. Proceedings of National Academy of Sciences of The United States of America 99:5189-5194. 2002.

Interpretive Summary: Pesticide use has been blamed for contaminating soil, water and air resources. Many pesticides remain active (i.e., toxic) for long time periods after application. This can be useful for controlling pests that affect crop production which benefits society by assisting in the production of an abundant and nutritious food supply. However, when pesticides leave the root zone, they become troublesome and methods are needed to minimize deleterious effects from the use of pesticides. Water contaminated with pesticides can pollute environmentally sensitive areas, or become a significant health risk to persons that rely on water for drinking purposes. The research described in this paper provides a method to quickly destroy certain pesticides (i.e., alachlor, and related) without the production of toxic byproducts. In a laboratory column experiment, adding ammonium thiosulfate to the inlet water removed alachlor from the soil water system. At the effluent end of the column, nearly 100% of the alachlor was removed from the soil water.

Technical Abstract: Halogenated organic compounds (HOCs) are among the most widely used synthetic chemicals. Many HOCs are recalcitrant to natural degradation and have become prominent environmental contaminants. One group of such HOCs are the heavily used chloroacetanilide herbicides. We have found for the first time that chloroacetanilide herbicides are rapidly dechlorinated in water, sand, and soil by thiosulfate salts. Structural and kinetics analysis suggests that the reaction occurred by SN2 nucleophilic substitution, in which the chlorine was replaced by thiosulfate and the herbicide was biologically deactivated. Laboratory studies showed that this reaction could be used for removing residues of chloroacetanilide herbicides in water, soil and sand. Our findings on these and other HOCs clearly suggest that many HOCs may be subject to this reaction. Since common thiosulfate salts are innocuous products (e.g., fertilizers) and the reaction selectively detoxifies HOCs, this discovery may lead to a new way for safe and effective decontamination of HOCs in the environment.