Temporal Monitoring of Organochlorine Compounds in Seawater by Semipermeable Membranes following a Flooding Episode in Western Europe

During January 1995, a severe flooding event in central and western Europe caused a significant outflow of contaminated freshwater into the Northern Sea and to Skagerrak. This water reached the Swedish west coast in mid-March. During this time, SPMD (semipermeable membrane device) sampling was performed directly in the plume. Depending on the salinity, this contaminated water was found at a depth of 22−25 m in Skagerrak. Two SPMD sampling sites were placed in this area at a depth of 24 m, and the SPMDs were changed every 12−16 days during the 12-week study. In the meantime, water temperature increased from 4 to 8 °C at the 24 m depth. PCBs, DDTs, chlordane, hexachlorobenzene, α-HCH, γ-HCH (lindane), dieldrin, and other organochlorine compounds were detected in the SPMD samples. A time trend with elevated concentrations during the floodwater arrival, followed by decreasing concentrations, could be seen for most of the compounds studied. The highest levels of organochlorine compounds were found for PCBs and DDTs. The amounts found in the truly dissolved aqueous phase were respectively 4 and 2 times higher during mid-March 1995 when compared to an apparent baseline level measured during April and May. By using earlier reported relationships between water concentration and sampling rates, a truly dissolved concentration was calculated for each compound.