Bioaccumulation of Pcdd/dfs and Dioxin-like Pcbs in the Soil Food Web of Fallow Rice Fields in Japan

Abstract The objective of this study is to investigate the concentration of PCDD/DFs and dioxin-like PCBs in a fallow soil ecosystem and to reveal its bioaccumulation mechanism. Soil, earthworm and lesser Japanese mole (Mogera imaizumi) samples were collected in the two fallow rice fields in Kanagawa Prefecture, Japan. The TEQ concentrations of dioxins in soils (organic carbon base) and earthworms (fat base) were same level, but those in mole livers (fat base) were much higher than those in earthworms. The congener profiles of soil and earthworm are quite similar. However, there were major differences in the congener profiles between mole’s muscle and liver, and earthworms. This might have been a result of mole’s characteristic accumulation of dioxins in liver and also congener specific metabolism of dioxins in mole body. This study showed that dioxins do not accumulate from soil to earthworm but do accumulate from earthworms to mole liver, implying that this might be one of the major exposure routes to their predators.