Bioaccumulation of Dioxins Through Aquatic Food Chain

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The contamination of levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/DFs) and coplanar polychlorinated biphenyls (co-PCBs) were determined in various aquatic organisms from Lake Shinji and Tokyo Bay. In addition, stable nitrogen isotope ratios, which can be used as a parameter for quantifying trophic levels in the aquatic food chain, were determined.In the aquatic food chain, consist of plankton, benthic organisms, shellfish, and fish, each congener of co-PCB increased with the increasing trophic position. In contract to this, total PCDD/DFs concentration decreased with the increasing trophic position, while in total PCDD/DF-TEQ (toxic equivalents) increased with the trophic position. These phenomena were explained by the different trophic accumulation potency of various dioxin-like congeners through the trophic level (expressed as slope of regression line between congener concentration in organisms and stable nitrogen isotope ratio for each congener). The trophic a … More ccumulation potency were determined to be in the following order : mono-ortho-PCBs > non-ortho-PCBs > 2,3,7,8-substituted PCDD/DF congeners > non-2,3,7,8-substituted congeners. In addition, in the case of 2,3,7,8-substituted PCDD/DFs, the potency decreased with the increase of octanol-water partition coefficient (Kow).Analysis based on the biota-sediment accumulation factor (BSAF) gave the similar result explained above. The BSAFs for 2,3,7,8-PCDD/DF congeners were almost same for planktons, however, those for shellfish and fish decreased with the increase of Kow of those congeners, indicating that 2,3,7,8-congeners with higher Kow values are not efficiently transferred to higher trophic level. This phenomenon was not observed in the case of co-PCBs. BSAFs for co-PCBs were high and indicated to be efficiently transferred to higher trophic levels.These results showed that combined monitoring of nitrogen isotope ratio and contamination will give a better-synthesized data for bioaccumulation of pollutant through the food chain. Less