Accumulation and Elimination Kinetics of Butachlor, Thiobencarb and Chlomethoxyfen by Aristichthys nobilis

Kuo-Hsiung Lin, Jui-Hung Yen & Yei-Shung Wang*

Laboratory of Pesticide Chemistry, Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan

Abstract: Bioconcentration kinetics of three major paddy-field herbicides, butachlor [N-(butoxymethyl)-2-chloro-N-(2,6-diethylphenyl) acetamide], thiobencarb [S-[(4-chlorophenyl)methyl] diethylcarbamothioate] and chlo-methoxyfen [2,4-dichlorophenyl-3¢-methoxy-4¢-nitrophenyl ether] were investigated in accumulation and elimination experiments in a laboratory with black silver carp (Aristichthys nobilis).   The biological half-lives of the three herbicides at large and small-exposure doses 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 short term of 14-day expiry experiment were used to estimate the parameters of two kinds of models with nonlinear regression analysis, and the bioconcentration factors (BCF) in the steady state were calculated from those parameters. The BCF in a steady state have the descending order thiobencarb > chlomethoxyfen > butachlor at large concentration, but butachlor > thiobencarb > chlomethoxyfen at small concentration.    Both models serve to predict the BCF in prolonged exposure to three herbicides.   It seemed useful for assessment of the influence of chemical pollutants in aquatic organisms.