Polychlorinated Dibenzo-para-dioxins and Polychlorinated Dibenzofurans in Sediments from U.K. Estuaries

Concentrations of polychlorinated dibenzo-para-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) have been determined in sediments from U.K. coastal locations adjacent to the estuaries of the Dee, Humber, Mersey, Tees, Tweed and Tyne and from an offshore site in Morecambe Bay. The sediments had total PCDD/DF concentrations of <100 pg g-1, except for the Dee and Morecambe Bay which had total PCDD (total PCDF) concentrations of 750 (390) and 207 pg g-1 (116 pg g-1), respectively. However, estuarine sediments collected during axial transects of Dee, Humber and Clyde Estuaries had total PCDD (total PCDF) concentrations in the range 530-1880 (340-710), 300-1890 (260-1240) and 290-4670 pg g-1 (100-1540 pg g-1), respectively. Examination of the homologue groups showed that about 70% of PCDDs were in the octa-chlorinated form in the Dee and Clyde, whereas for PCDFs the hepta- and hexa-chlorinated forms were relatively more important. The association of PCDD/DFs with particle surfaces was interpreted using data on sediment characteristics and a two-stage adsorption model. The conclusions from this study have implications for the estuarine transport of PCDD and PCDF and their uptake by benthic organisms.