Bioaccumulation of Dioxins in Terrestrial Food Chain: Concentrations of Dioxin Congeners and Trophic Level

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and nonand mono-ortho-substituted polychlorinated biphenyls (dioxin-like PCBs) was analyzed in earthworms, plants, insects, field mouse and birds collected in Kanagawa Prefecture and their accumulation in the terrestrial ecosystem was studied. TEQ was highest in raptor species and followed by mouse liver, other birds, earthworms, plants and insects. Furthermore, the relationships between concentrations of PCDD/F congeners and trophic level based on nitrogen stable isotope ratio (δ 15 N) were examined. The results showed that 2,3,7,8-TeCDD/F concentrations were elevated along with trophic level rising. On the other hand, OCDD/F concentrations were not significantly elevated along with trophic level. Introduction It has been revealed that persistent organic pollutants (POPs) emitted in the past still remain in environment, and are accumulated through food web 1, 2 . In addition, it has been reported that accumulated POPs give adverse effect on wildlife 3 . In aquatic food web, it has been observed that 2,3,7,8-TeCDF concentration increased with rising trophic level while OCDD concentration decreased 4 . However, few studies have been conducted on terrestrial food web. Therefore, in this study, accumulation of dioxin was monitored for terrestrial organisms. In geochemistry, stable isotope ratio has been used as an indicator of trophic position. Generally, it has been known that stable nitrogen isotope ratios (δ 15 N) in predator animals are higher than in those in the preys by about 3~4‰, based on which, relative trophic position of an animal in the food web can be estimated. In this study, the relationships between concentration of dioxins and stable isotope ratio in terrestrial animals were examined and relationships between PCDD/Fs and trophic level were reported. Materials and Methods Sample Collection: Earthworm, plant, insect, and field mouse samples were collected from the fallow in Kanagawa Prefecture, Japan. Bird samples were collected by Kanagawa Prefectural Nature Conservation Center, Kanagawa, Japan, which is a re-habilitation center for injured wild birds. Bird samples were collected throughout the Kanto region, Japan (Figure 1). Earthworms (Megascolecidae and Lumbricidae) were collected in August and October 20005, May and November 2006. Plants (Erigeron philadelphicus) and insects (Atractomorphalata and Oxya japonica and Patanga japonica) were collected in November 2006. Field mouse (Apodemus speciosus) was collected in December 2006. Earthworm, plant, insect samples were collected by hand while field mouse sample was collected by a trap. The birds that died after the accident or sickness were provided for analysis. The samples consisted of Northern Goshawk (Accipiter gentilis), Peregrine Falcon (Falco peregrinus), Japanese Sparrowhawk (Accipiter Figure 1 The location of Kanto region and Kanagawa prefecture, Japan ENVIRONMENTAL LEVELS ASIA Organohalogen Compounds Vol 69 (2007) P-10