Estimation of the uptake of organochlorines by the mayfly Hexagenia limbata (Ephemeroptera: Ephemeridae)

Uptake rate coefficients (k(s)) and biota-sediment- accumulation-factors (BSAFs) for 17 hydrophobic chemicals with octanol-water partition coefficients (log K-ow) ranging from 5.4 to 7.4 were determined for mayfly nymphs (Hexagenia limbata) exposed to contaminated sediments collected from the Detroit River. Nymphs obtained 95% of steady state conditions within a 32 day exposure period for all chemicals of study. Using two different exposure strategies, estimates of uptake rate coefficients ranged from 0.27 to 11.38 g(sediment). g(lipid)(-1) . h(-1) and became independent of K-ow for chemicals of log K-ow > 5.9. Biota Sediment Accumulation Factors ranged from 1.2 to 9.4, and followed similar trends as observed for k(s) estimates. The results support the conclusion that bioaccumulation occurred as a result of ingestion of contaminant sorbed to sediment organic carbon, and that sediment was the primary chemical exposure route for hydrophobic organic chemicals with log K-ow > 5.9.