Aerobic and Anaerobic Degradation of Aldicarb in Asceptically Collected Soils

Abstract

AbstractDegradation and metabolism of [14C] aldicarb [2‐methyl‐2‐(methylthio)propionaldehyde O‐(methylcarbamoy) oxime] in soils under aerobic and strictly anaerobic conditions were investigated. Soils were collected aseptically from a 6‐ha tract in Dougherty Plains, GA. Under aerobic conditions, aldicarb (A) rapidly disappeared and aldicarb sulfoxide (ASO) was rapidly formed. The latter in turn was slowly oxidized to aldicarb sulfone (ASO2). Disappearance of A and formation of ASO and ASO2 were generally more rapid in surface soils and shallow subsurface soils than in deeper subsurface soils. A number of additional metabolites were detected, including thin layer chromatography (TLC)‐polar products, ASO oxime, ASO nitrile, and A acid. Half‐lives for total toxic residue (TTR) in 24 surface and subsurface soils ranged from 29 to 78 d, with an average of 52 d. Aldicarb sulfoxide was the principal metabolite in soils under strictly anaerobic conditions; ASO2, ASO oxime, and ASO acid in small quantities were detected in some soils; and TLC‐polar products were also detected in most soils. Half‐lives for TTR in three deep subsurface soils under strictly anaerobic conditions were shorter than in three shallow subsurface soils. Although A persisted considerably longer in anaerobic soils, anaerobic half‐lives for TTR in subsurface soils were significantly shorter than under aerobic conditions.