Bioavailability and Toxicity of a Mixture of Sediment-Associated Chlorinated Hydrocarbons to the Amphi pod Pontoporeia hoyi

The toxicity and bioavailability of a mixture of 13 sediment-associated chlorinated hydrocarbons were determined for the amphipod Pontoporeia hoyi. The processes were traced with two radiolabeled compounds, '4C-2,2',4,4'-tetrachlorobiphenyl (2244TCB) and 3H-benzo(a)pyrene (BaP). The toxicity of the chlorinated hydrocarbon mixture resulted primarily from the lindane and dieldrin components. The 72-h LCM was 14.5 nmol g-I as the sum of the added chlorinated hydrocarbons and 4.7 nmol g-I as the sum of the lindane and dieldrin. At 144 h the LCws had dropped to 1.51 and 0.53 nmol g-I, respectively. At the lowest dose, 2.4 nmol g-' sediment, the time to yield 50% mortality (LTSo) was 119 h. The toxicokinetics for the radiolabeled compounds yielded sediment uptake clearance constants of 0.0018 and 0.018 g dry sediment g-I animal h-I for BaP and 2244TCB in the absence of added chlorinated hydrocarbons. At the lowest chlorinated hydrocarbons dose, the clearance constants of both BaP and 2244TCB were approximately doubled. The clearance constants were not proportional to the freely dissolved concentration of the radiolabeled compounds in the interstitial water but were presumed to be proportional to the compound desorption rates. For the chlorinated hydrocarbons, the uptake clearances were inversely proportional to the log of the octanol-water partition coefficient. The bioaccumulation factor (BAF, concentration in the organism divided by the concentration in the sediment) appeared to peak at about a log octanol-water partition coefficient of 6. However, the BAF ranged from less than 1 to greater than 30 for compounds with a log KO, near 6.