ESTIMATION OF THE UPTAKE OF ORGANOCHLORINES BY THE MAYFLY HEXAGENIA-LIMBATA (EPHEMEROPTERA, EPHEMERIDAE)

Uptake rate coefficients (k(s)) and biota-sediment- accumulation-facto rs (BSAFs) for 17 hydrophobic chemicals with octanol-water partition c oefficients (log K-ow) ranging from 5.4 to 7.4 were determined for may fly nymphs (Hexagenia limbata) exposed to contaminated sediments colle cted from the Detroit River. Nymphs obtained 95% of steady state condi tions within a 32 day exposure period for all chemicals of study. Usin g two different exposure strategies, estimates of uptake rate coeffici ents ranged from 0.27 to 11.38 g(sediment). g(lipid)(-1) . h(-1) and b ecame independent of K-ow for chemicals of log K-ow > 5.9. Biota Sedim ent Accumulation Factors ranged from 1.2 to 9.4, and followed similar trends as observed for k(s) estimates. The results support the conclus ion that bioaccumulation occurred as a result of ingestion of contamin ant sorbed to sediment organic carbon, and that sediment was the prima ry chemical exposure route for hydrophobic organic chemicals with log K-ow > 5.9.