Occurrence of PCDD/F in dated lake sediments of the Black Forest, southwestern Germany

Despite concerns about the toxicity of polychlorinated dibenmo-p-dioxins and dibenzofurans (PCDD/F), there are still few data on their past trends in Middle Europe. Here, We use paleolimnology to assess the occurrence of PCDD/F in sediments of four remote Black Forest lakes where atmospheric deposition has been the only possible input. Considerable quantities of PCDD/F occurred in the sediments of one lake before the production of chlorophenols in the 1920s, emphasizing that they are not only recent contaminants. On the basis of homologue profiles typical for soots, we suggest that fossil fuels burned since industrialization were a major source at this time. PCDD/F loadings in sediments accelerated in the 1930s at one site and in the 1960s at three others. Changes in homologue profiles were lake-specific but generally implicated sources in waste incineration, combustion of fossil fuels, and metal processing. Peak TEQ of 205.2 and 228.7 ng/kg occurred respectively in sediments from 1964 to 1985 at Wildsee and from 1982 to 1992 at Herrenwieser See. Despite the small geographical area represented by the lakes, their historical trends in PCDD/F burden differed due probably to variations in local and regional sources. This indicates that more extensive surveys than those often available are required to ensure representative data on regional patterns of contamination.