Sources, transport, reservoirs and fate of dioxins, PCBs and HCB in the Baltic Sea environment

The importance of the persistence of a compound released to the environment became apparent in 1966 when PCBs were demonstrated to be abundant in biota. This was the first time a non-intentionally spread chemical was found to accumulate and cause effects in the environment. Unfortunately, since then, many other compounds with similar properties have been detected in the environment. During the last decades, the environmental pollution of PCBs, dioxins and other persistent organic pollutants (POPs) has been extensively studied in numerous media in many countries all over the world. In Sweden, there has been much focus on the situation in the Baltic Sea and its surroundings. Since around the 1970s, the levels of dioxins and PCBs have shown decreasing environmental trends. For some POPs, these trends have levelled off in many areas since the mid-1980s and have remained more or less stable since then. In 1972, the use of PCBs in open systems was banned and thereafter many other actions have been taken in order to reduce emissions of dioxins and other POPs. These measures obviously had a great impact on the situation. The lack of profound improvement during the last fifteen years is, however, troublesome and suggests the presence of hitherto unknown sources and/or that the importance of some known (primary and secondary) sources has been misjudged.The aim of the current work was to identify the sources that contribute to the present pollutant situation including current fluxes of POPs to, from and within the Baltic Sea. Some well-known POPs were selected (PCBs, dioxins and HCB) as representatives for a broad range of physical-chemical properties. These compounds are also known to have different (primary) sources and they represent both intentionally and unintentionally formed pollutants. Based on current knowledge and new measurements, the current pollution scenario of the Baltic Sea ecosystem was modelled in order to get an overview of the relative impact of various sources. Future scenarios were also predicted including varying pollution source strengths.The results from this study are intended to be used together with other relevant information to form an up-to-date basis for a new Swedish strategy on POPs with special emphasis on POPs formed unintentionally.Main authors: Karin Wiberg, Department of Chemistry, Umeå University, Michael McLachlan, Department of Applied Environmental Science, Stockholm University, Per Jonsson, Department of Applied Environmental Science, Stockholm University, Niklas Johansson, Swedish Environmental Protection AgencyContributing authors: Sarah Josefsson, Eva Knekta, Ylva Persson and Kristina Sundqvist, Department of Chemistry, Umeå University; James Armitage, Dag Broman, Gerard Cornelissen, Anna-Lena Egebäck and Ulla Sellström, Department of Applied Environmental Science, Stockholm University and Ingemar Cato, Geological Survey of Sweden