title: Dechlorinating chloroacetanilide herbicides by dithionite-treated aquifer sediment and surface soil.
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(lII), creating a redox barrier of Fe(ll)-bearing minerals and surface-bound Fe(ll). Washing the reduced sediment (buffered with citrate-bicarbonate) with oxygen-free water removed Fe(ll) 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.
authors.affiliation: School of Natural Resources, University of Nebraska-Lincoln, Lincoln, Nebraska 68583-0915, USA.
authors.forename: Hardiljeet K
authors.initials: HK
authors.lastname: Boparai
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Shea
authors.forename: Steve D
authors.initials: SD
authors.lastname: Comfort
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Snow
mesh_terms: D000081:Acetamides / Q000032:analysis / Q000737:chemistry*; D000327:Adsorption; D002021:Buffers; D002254:Carbonates / Q000737:chemistry; D002713:Chlorine / Q000737:chemistry; D004227:Dithionite / Q000494:pharmacology*; D006540:Herbicides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D010084:Oxidation-Reduction; D011188:Potassium / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis*; D014873:Water Pollutants
chemical_list: D000081:Acetamides; D002021:Buffers; D002254:Carbonates; D006540:Herbicides; D012989:Soil Pollutants; D014873:Water Pollutants; D004227:Dithionite; C000188:alachlor; D002713:Chlorine; C078188:2-chloro-N-(ethoxymethyl)-N-(2-methyl-6-(trifluoromethyl)phenyl)acetamide; C037593:potassium carbonate; D011188:Potassium