Influence of trophic status on PCB distribution in lake sediments and biota.

We investigated the relationship between trophic status and polychlorinated biphenyl (PCB) distribution in 19 Swedish lakes. We analyzed PCB in water, phytoplankton, zooplankton, fish and sediment during two sampling periods, in spring and summer. The mass of sigma PCB in the lake sediments was positively related to lake trophy, i.e. more PCBs were accumulated and buried in the sediment of eutrophic lakes than in oligotrophic lakes. In the oligotrophic lakes a greater fraction of the total PCB load was dissolved in water. We conclude that this is a result of higher sedimentation rates in eutrophic lakes and relatively lower turnover of organic carbon in the water column of the shallow, eutrophic lakes. In the stratified lakes, the amount of PCB per cubic meter in the epilimnion decreased from spring to summer. We suggest that sedimentation of plankton beneath the thermocline during stratification act as a sink process of PCBs from the epilimnion.

Factors determining the uptake of persistent pollutants in an eel population (Anguila anguilla L.).

The distribution of persistent pollutants in an eel population from a eutrophic lake of southern Scandinavia was examined. The origin of PCBs, DDT, DDE and lindane found in the fish was most likely the atmosphere. The most important factors for uptake of the chlorinated hydrocarbons was age (exposure time), growth rate and fat content. The life cycle of the eel is unique with a stage in freshwater when energy reserves (fat stored in muscular tissue) and lipophilic pollutants are accumulated. This stage is followed by a long migration to the spawning areas in the Sargasso Sea when pollutants are released from the fat deposits. These two stages followed by a once-in-a-lifetime spawning behaviour, makes the eel especially vulnerable to persistent pollutants. The effects of persistent pollutants combined with the eel's unusual life cycle may explain the decline in the eel population in northern Europe in recent decades.

Microbial degradation of xenobiotic, aromatic pollutants in humic water.

The microbial degradation of a number of 14C-labeled, recalcitrant, aromatic pollutants, including trichloroguaiacol and di-, tri-, and pentachlorophenol, was investigated in aquatic model systems in the laboratory. Natural, mixed cultures of microorganisms in the water from a brown-water lake with a high content of humic compounds mineralized all of the tested substances to a higher degree than did microorganisms in the water from a clear-water lake. Dichlorophenol was the most rapidly degraded pollutant.

An attempt to measure the flow of chlorinated hydrocarbons, such as PCBs, from water to air in the field.

A field sampling device to study the transport of aromatic, persistent chlorinated hydrocarbons from water to air was constructed. It was tested in large, outdoor artificial ponds contaminated with polychlorinated biphenyls (PCBs). The PCB compounds volatilised to air at a rate of 0.9 to 9.6 ng m(-2) h(-1) depending on levels of PCBs in the water and water temperature.