Polychlorinated biphenyl equilibria in an estuarine system.

The stability of the partition of polychlorinated biphenyl (PCB) congeners between water and the compartments of particulate matter (seston), surface sediment, net-plankton and mussels has been investigated for 1.5 years. Samples were regularly obtained from four stations, representing River Rhine, brackish and saline estuarine and stagnant saline conditions. In spite of the PCB gradients, from freshwater to seawater, and time variations in concentrations, the partition coefficients Kd (distribution coefficients) were very stable for each of the congeners. This demonstrates that the partition between water and the other compartments is due to processes which reach their equilibrium within weeks, independent of the local variations in concentrations. This confirms the non-foodchain accumulation concept of Schneider [1] for aquatic organisms.