Bioaccumulation and elimination of avermectin B1a in the earthworms (Eisenia fetida)

The acute toxicity, bioaccumulation, and elimination of avermectin B-1a (AVM B-1a) in earthworm (Eisenia fetida) were investigated in different exposure systems. The LC50 of AVM B-1a on earthworms were 24.1 mg/kg and 17.1 mg/kg, respectively, for 7 and 14 days in artificial soil. The LC50 tested by the filter paper for 2 days was 4.63 mu g/cm(2). The earthworms were cultivated in artificial soil containing 0.6 mg/kg and 3.0 mg/kg AVM B-1a, respectively for bioaccumulation experiments. The AVM B-1a residues in earthworms were determined with HPLC-fluorescence method. The results showed that AVM B-1a was taken up from the concentrated artificial soil by the earthworms and the steady-state levels were reached after 9-18 days of exposure. On the 18th day, the final concentrations of AVM B-1a in the earthworms treated with two different dosages were 107 ng/g and 165 ng/g, respectively; there were not significantly accumulation. About 80.0% and 94.8% of the accumulated AVM B-1a. were eliminated respectively in two groups within I day after they were exposed to AVM B-1a-free soil, but a trace amount of AVM B-1a was found for a relative long time in earthworms. (c) 2005 Elsevier Ltd. All rights reserved.