YAMAMURO Masumi Geological Survey of Japan, Senior Researcher, 地質調査所, 主任研究官
HANAI Yoshimichi Institute of Environmental Science and Technology, Yokohama National University, Research Associate, 環境科学研究センター, 助手 (00114984)
NAKAI Satoshi Institute of Environmental Science and Technology, Yokohama National University, Associate Professor, 環境科学研究センター, 助教授 (70217644)
|Budget Amount *help
¥3,700,000 (Direct Cost : ¥3,700,000)
Fiscal Year 2000 : ¥1,400,000 (Direct Cost : ¥1,400,000)
Fiscal Year 1999 : ¥2,300,000 (Direct Cost : ¥2,300,000)
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
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