Bioconcentration of cypermethrin, deltamethrin, fenvalerate and permethrin by Chironomus tentans larvae in sediment and water

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Abstract
The bioconcentration of four synthetic pyrethroid insecticides (cis‐ and trans‐cypermethrin, deltamethrin, fenvalerate and cis‐ and trans‐permethrin) by larvae of the midge Chironomus tentans was studied in sand, silt and clay sediments and water (sediment/water ratio, 1:5). Larvae were exposed for 24 h in sediment and for 48 h in water above sediment that contained 12 to 640 ng/g 14C‐labeled cypermethrin and 5 and 50 ng/g of the other compounds. Depuration of radioactivity following transfer to clean sand/water systems was monitored for 96 h. Bioconcentration factors for larvae held in sand ranged from 135 for trans‐permethrin to 316 for deltamethrin. Larvae in water above sand accumulated 5‐ to 15‐fold greater concentrations of each pyrethroid than did larvae held in water above silt or clay sediments. The lower bioavailability of each compound to larvae in water above silt and clay was attributed to greater sorption to suspended particulates and to dissolved organic carbon in these systems than in relatively particulate‐free sand/water systems. The accumulation of pyrethroids by larvae in silt and clay sediments was best accounted for by the uptake of the dissolved portion of each compound in pore water. Depuration of the four pyrethroids by Chironomus larvae was rapid, with an overall half‐life for radioactivity of 27 ± 8 h. Exposure for 24 h in sediments containing 5 ng/g concentrations of each pyrethroid had little effect on the behavior of the larvae, but at higher concentrations the animals were immobilized, although many survived following transfer to depuration experiments.

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