Bioaccumulation of polycyclic aromatic compounds: 2. Modeling, bioaccumulation in marine organisms chronically exposed to dispersed oil

Within the frame of a large environmental study, we report on a research pr ogram that investigated the potential for bioaccumulation and subsequent ef fect responses in several marine organisms exposed to chronic levels of dis persed crude oil. Body burden can be estimated from kinetic parameters (rat e constants for uptake and elimination), and appropriate body burden-effect relationships may improve assessments of environmental risks or the potent ial for such outcomes following chronic discharges at sea. We conducted a s eries of experiments in a flow-through system to describe the bioaccumulati on kinetics of polycyclic aromatic hydrocarbons (PAH) at low concentrations of dispersed crude oils. Mussels (Mytilus edulis) and juvenile turbot (Sco phthalmus maximus) were exposed for periods ranging from 8 to 21 d. Postexp osure, the organisms were kept for a period of 9 to 10 d in running seawate r to study elimination processes. Rate constants of uptake (k(1)) and elimi nation (k(2)) of the PAHs during and following exposure were calculated usi ng a first-order kinetic model that assumed a decrease of the substances in the environment over time. The estimated bioconcentration factor was calcu lated from the ratio of k(1)/k(2),. The kinetic parameters of two-, three-, and four-ring PAHs in mussel and fish are compared with estimates based on hydrophobicity alone, expressed by the octanol-water partition coefficient , K-ow (partitioning theory). A combination of reduced bioavailability of P AHs from oil droplets and degradation processes of PAHs in body tissues see ms to explain discrepancies between kinetic rates based on K-ow and actual kinetic rates measured in fish. Mussels showed a pattern more in compliance with the partitioning theory.