Fate of seven pesticides in an aerobic aquifer studied in column experiments

The fate of selected pesticides (bentazone, isoproturon, DNOC, MCPP, dichlo rprop and 2,4-D) and a metabolite (2,6-dichlorobenzamide (BAM)) was investi gated under aerobic conditions in column experiments using aquifer material and low concentrations of pesticides (approximately 25 mu g/l). A solute t ransport model accounting for kinetic sorption and degradation was used to estimate sorption and degradation parameters. Isoproturon and DNOC were sig nificantly retarded by sorption, whereas the retardation of the phenoxy aci ds (MCPP, 2,4-D and dichlorprop), BAM and bentazone was very low. After lag periods of 16-33 days for the phenoxy acids and 80 days for DNOC, these pe sticides were degraded quickly with 0-order rate constants of 1.3-2.6 mu g/ l/day. None of the most probable degradation products were detected. (C) 20 00 Elsevier Science Ltd. All rights reserved.