Accumulation and elimination kinetics of herbicides butachlor, thiobencarb and chlomethoxyfen by Aristichthys nobilis

Abstract

Bioconcentration kinetics of three major paddy-field herbicides, butachlor, thiobencarb and chlomethoxyfen were investigated by accumulation and elimination measurements in laboratory experiments with black silver carp (Aristichthys nobilis). The biological half-lives of the three herbicides on exposure at high and low concentrations were 11.6 and 23.1 days for butachlor, 13.9 and 17.3 days for thiobencarb and 5.6 and 4.5 h for chlomethoxyfen, respectively. One- and two-compartment models were used to elucidate the bioconcentration kinetics. Data from a short-term, 14-day expiry experiment were used to estimate the parameters in the models by non-linear regression analysis, and the bioconcentration factors (BCF) in the steady state were calculated from those parameters. The BCF in the steady state have the descending order thiobencarb > chlomethoxyfen > butachlor at high concentration, and butachlor > thiobencarb > chlomethoxyfen at low concentration. One-compartment model for butachlor and thiobencarb and a two-compartment model for chlomethoxyfen are useful to predict the BCF on prolonged exposure and, further, to assess the influence of these pollutants.