Anaerobic abiotic reduction of dichloroacetamide safeners: effects of manganese oxides and agrochemical co-formulants

Abstract

Safeners are added to herbicide formulations to protect crops from toxic effects of active herbicides. Evidence suggests that as dichloroacetamide safeners transform, they can become more biologically active. Dichloroacetamide safeners can transform via reductive dechlorination in anaerobic abiotic systems containing iron oxy-hydroxide minerals. Manganese oxides are important redox-active species that frequently co-occur with iron oxides. This study examines the anaerobic reduction of three dichloroacetamide safeners in the presence of agrochemical co-formulants, in changing pH buffer and ionic strength conditions, and in Fe(II)-amended, abiotic mixed-mineral systems. The safener dichlormid did not transform appreciably over the sampling period (up to 6 hours). Transformation of the safeners benoxacor and furilazole was not appreciably affected by the presence of co-formulants, pH buffer, or changes in ionic strength. The molar ratio of Fe(II)-to-Mn(IV) oxide had an appreciable effect on the transformation rate of benoxacor and furilazole.