Toxicokinetics of fluoranthene to the amphipod, Leptocheirus plumulosus, in water-only and sediment exposures

The ability of the equilibrium partitioning (EqP) and critical body residue (CBR) approaches to predict the toxicity of the polycyclic aromatic hydrocarbon, fluoranthene, to a standard sediment toxicity test organism, the amphipod Leptocheirus plumulosus was examined in a series of water-only and sediment exposures. Concentrations of fluoranthene in water that resulted in 50% mortality (10-d LC50) were 39.2 (35.1–43.8, 95% C.I.) and 39.2 (34.1-– 45.1, 95% C.I.) μg / liter in replicate tests. CBR or tissue concentrations that produced 50% mortality after replicate 8-d water-only exposures (LD50) were 0.694 (0.596–0.876, 95% C.I.) and 2.44 (1.83–3.68, 95% C.I.) mmol total fluoranthene-equivalents/kg wet wt tissue, values somewhat lower than the range of CBR established for nonpolar narcotics in other organisms ( ). No significant mortality of L. plumulosus was observed over 26-d sediment toxicity tests, even though estimated interstitial water concentrations (up to 212 μg/liter) exceeded the average water-only LC50 (39.2 μg/liter) by more than a factor of five, suggesting that the EqP approach over-estimated toxicity to this species. Average tissue concentrations attained in sediment tests ( ) were substantially lower than the CBR for nonpolar narcotics in other organisms, and in the water-only tests. Thus, lack of mortality in sediment exposures agrees with CBR predictions. The CBR approach appears to be a useful complement to the EqP approach for predicting the toxicity of sediment-associated contaminants.