抄録
We measured the concentrations of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxin-like polychlorinated biphenyls in sediments of the Furuayase River, located in the southeast part of Saitama Prefecture, Japan. Surface and core sediment samples were collected at 27 sites at 50 m intervals upstream and downstream of the Matsueshinbashi Bridge. Dioxin concentrations in toxic equivalents (TEQ) in surface sediment at 9 sites located within the area 300 m upstream and 200 m downstream of the bridge exceeded the Japanese environmental standard for sediment. Dioxin concentrations in sliced core samples collected from lower sediment layers were generally higher than concentrations in samples collected from upper layers. The homologue profiles in the samples collected at upstream sites differed from those in the samples collected at downstream sites, suggesting that the bridge piers at the saddle of the riverbed affected the flow and diffusion of surface sediment in the river. Extremely high concentrations of 1,3,7,8-/1,3,7,9-TeCDF were detected in some samples, mainly those collected upstream of the bridge. These congeners were found in the lower layers of sediment, and the contamination in the lower layers sediment may have resulted from the long-term influence of drainage from upstream drainage ditches.
