Relative persistence of hexachlorocyclohexane, methyl parathion and carbofuran in an alluvial soil under flooded and non-flooded conditions

Abstract

The relative persistence of the γ-isomer of hexachlorocyclohexane (γ-HCH, organochlorine), methyl parathion (O-O-dimethyl O-p-nitrophenyl phosphorothioate, organophosphate) and carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl N-methylcarbamate, carbamate) in an alluvial soil was studied under flooded and non-flooded conditions. Under flooded conditions, γ-HCH was the least persistent of the three insecticides followed by methyl parathion and carbofuran, but under non-flooded conditions, γ-HCH was the most stable followed by carbofuran and methyl parathion. A major portion of the ¹⁴C in γ-HCH and methyl parathion was not accounted for, especially under flooded conditions, possibly due to the formation of volatile products. Formation of soil-bound residues from γ-HCH and methyl parathion was negligible. However, during metabolism of carbofuran, its hydrolysis product, carbofuran phenol, and bound residues accumulated in the soil in substantial quantities. The data generated from these concurrently incubated studies demonstrate that the relative persistence of insecticides with different functional groups in the soil is governed by the moisture regime.