Temporal development of chlorinated hydrocarbons in the Baltic Sea sediments: Characterization of the pollution maximum

The Baltic Sea, a semi-enclosed marginal sea with a catchment area four times its size, acts as a sink and continues to show detectable levels of persistent organic pollutants (POPs) in its sediments. This is attributed to the synthesis and industrial use of commercial polychlorinated biphenyls (PCB) products, as well as the widespread use and discharge of certain chlorinated pesticides into the natural environment during the last century. Our study investigates chlorinated hydrocarbon pollutants, the polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and its metabolites as well as hexachlorobenzene (HCB) in sediments based on several short sediment cores from different basins covering almost the entire Baltic Sea. In this study, we document the decline of PCB, HCB and DDT metabolites in Baltic Sea sediments, visible in a sevenfold reduction of pollution levels over a period of 50 years since their maximum production in the mid-eighties of the last century. We reflect the pollution levels against the global regulations, especially the worldwide ban of the POPs at the beginning of the 21st century. Based on our results, we are now able, for the first time, to evaluate the fate of POPs in Baltic Sea sediments and to provide further explanation for the detection of POPs in previous and future studies.