UPTAKE OF HYDROPHOBIC XENOBIOTICS BY FISH IN WATER LADEN WITH SEDIMENTS FROM THE FRASER RIVER

摘要

We examined the uptake of three hydrophobic chemicals, TCB (1,2,4-trichlorobenzene), PeCB (1,2,3,4,5-pentachloroben-zene), and HCBP (2,2′,4,4′,6,6′-hexachlorobiphenyl), by unfed juvenile rainbow trout (Oncorhynchus mykiss) in test aquaria containing sediments from the Fraser River. Our working hypothesis was that the low organic carbon content of the Fraser River sediments would increase the bioavailability of xenobiotics associated with these sediments. The test chemicals and sediments were introduced into aquaria 9 d before the fish were introduced. Measured concentrations of the chemicals in the bottom sediments, suspended sediments, and filtered (0.45 μm) water suggested that the test system had reached a quasiequilibrium state by day 9. Subsequently, a 6-d exposure of fish in the test aquaria resulted in a significant accumulation of the test chemicals in the fish tissues and significant reductions in the chemical concentrations of the bottom sediments, suspended sediments, and filtered water. Mass balance analysis suggests that the appearance of HCBP and PeCB in the fish after 6 d could not be accounted for solely by the amount of chemical dissolved in the water at the time when the fish were introduced. A large unaccounted-for fraction of TCB, possibly due to fish metabolism, precluded an accurate mass balance analysis for this chemical. Because chemical uptake in fish with the pharynx plugged (to eliminate the gut uptake route) was similar to that in control fish and because direct access to bottom sediments did not alter chemical uptake, we conclude that hydrophobic chemicals such as PeCB and HCBP associated with suspended sediments from the Fraser River can readily desorb and be taken up across the gill.