BIOCONCENTRATION AND DEPURATION OF AVERMECTIN B_(1a) IN THE BLUEGILL SUNFISH

摘要

A dynamic 42-d study was conducted to evaluate the bioconcentration of [~3H]avermectin B_(1a) in the bluegill sunfish (Lepomis macrochirus). A mean water concentration of 0.099 μg/L was maintained for a 28-d exposure period. Radioassay throughout the exposure period indicated a gradual uptake of radioactivity that reached steady state at about 10 to 14 d; the day 28 tissue residue values were 6.8, 3.0, and 11 μg/kg, in whole fish, fillet, and viscera, respectively. Following this 28-d uptake period, fish were placed in control water for 14 d to permit monitoring of elimination of radioactivity. Radioassay indicated 91 to 95% clearance, with the tissue residues dropping by day 14 of the depuration period to 0.32, 0.27, and 0.53 μg/kg, respectively. A one-compartment kinetic model was used for analysis of the uptake-depuration data and yielded for whole fish an uptake rate constant of 12 L kg~(-1) d~(-1), a depuration rate constant of 0.21 d~(-1) (t_(1/2) of 3.3 d), and a steady-state residue concentration of 5.5 μg/ kg. The corresponding bioconcentration factor (BCF) for whole fish was 56 L/kg. Uptake and depuration rate data for fillet and viscera were not significantly different (α = 0.05) than the values for whole fish. The BCF values for fillet and viscera were 28 and 84 L/kg, respectively. The data are consistent with rapid depletion of abamectin (and the structurally related anthelmintic ivermectin) from the tissues of other animals (rats, sheep, cattle). Abamectin does not strongly, bioconcentrate in aquatic organisms and would not be expected to biomagnify.