Kinetics of uptake and depuration of synthetic pyrethroid insecticides in manila clam (Ruditapes philippinarum)

Abstract

Synthetic pyrethroid insecticides (SPIs) are frequently detected in water bodies and sediments, and they show high toxicity to aquatic organisms, but their toxicity kinetics remain unknown. In this work, the kinetics of uptake and depuration of three SPIs, fenpropathrin (FP), cypermethrin (CM) and deltamethrin (DM) were evaluated in manila clams (Ruditapes philippinarum) for the first time through a bioconcentration-semi-static test. Clams were exposed to three SPIs of different concentrations (2 ng/mL and 20 ng/mL) for 4 days, followed by a 10-day depuration stage. The results indicated that adult manila clams could absorb SPIs rapidly, and the bioconcentration factor (BCF) values of SPIs were different at high and low concentrations of contaminants. The depuration rate constants (k₂) of SPIs in adult manila clams ranged from 0.024 h^-1 to 0.037 h^-1. The bioaccumulation factors ranged from 319.41 to 574.38. And the half-lives (t_1/2) were in the range of 18.49 to 29.22 h. These results showed that manila clams have a high bioconcentration capacity, and SPIs have a high cumulative risk for bivalves. Moreover, after 10 days of elimination, SPIs can still be detected in manila clams at all concentrations, indicating that the complete elimination of SPIs required a longer time.

Keywords: Bioconcentration factor (BCF); Depuration; Manila clams; Synthetic pyrethroid insecticides (SPIs); Uptake.