natural water. Experiments with the Gota river water have shown that 25 ml of cyclohexane was lost by dissolution and 25 ml as droplets when extracting 200 1. of water. Knowing this, the results can be compensated for solvent losses. ACKNOWLEDGMENTThe authors wish to thank David Dyrssen for valuable discussions. We are also indebted to Soren Jensen for the provision of the polychlorinated biphenyls and to Birgitta Jarmark for technical assistance in the PCB analysis.