Dechlorinating chloroacetanilide herbicides by dithionite-treated aquifer sediment and surface soil

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31 Scopus citations

Abstract

The prevalent use of chloroacetanilide herbicides has resulted in nonpoint contamination of some groundwater and surface water. We determined the efficacy of dithionite-treated sediment and soils to transform chloroacetanilides. When used alone, dithionite rapidly dechlorinates chloroacetanilides in water, with the following order of reactivity: propachlor > alachlor > acetochlor > metolachlor. Stoichiometric release of chloride occurs during reaction with dithionite. and thiosulfate herbicide derivatives are produced. Treating aquifer sediment with dithionite reduces native Fe(III), creating a redox barrier of Fe(II)-bearing minerals and surface-bound Fe(II). Washing the reduced sediment (buffered with citrate-bicarbonate) with oxygen-free water removed Fe(II) and excess dithionite and no alachlor transformation was observed. In contrast, a dithionite-treated surface soil, rich in clay and iron, effectively dechlorinated alachlor after washing. Exposing alachlor to aquifer sediment treated with dithionite in potassium carbonate buffer (pH 8.5-9.0) produced dechlorinated alachlor as the major degradation product. Our results provide proof-of-concept that dechlorination of chloroacetanilide herbicides by dithionite and dithionite-treated aquifer sediment and soil is a remediation option in natural environments where iron-bearing minerals are abundant.

Original languageEnglish (US)
Pages (from-to)3043-3049
Number of pages7
JournalEnvironmental Science and Technology
Volume40
Issue number9
DOIs
StatePublished - May 1 2006

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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