Fingerprinting localized dioxin contamination: Ichihara Anchorage case.

Although concentrations of polychlorinated dibenzo-p-dioxins and dibezofurans (PCDD/Fs; dioxins) in majority of Japanese river and ocean sediments decreased below the national environmental quality standard of 150 pg-TEQ. (g-dry sediment)(-1) by 2004, localized contamination inasmuch as 100-fold excess of the environmental quality standard has been reported at various locations including Ichihara Anchorage in northeastern Tokyo Bay. In the present study, we analyzed all mono- to octachlorinated dioxins in 12 surface sediments from Ichihara Anchorage and applied positive matrix factorization (PMF) to quantitatively fingerprintthe congener pattern and geographical distribution of a factor causing the localized contamination. A PMF-derived fingerprint attributable to dioxin impurities in pentachlorophenol (PCP) exerted more than 90% contribution to total dioxin concentrations in Ichihara Anchorage surface sediments. Although majority of Ichihara Anchorage-born dioxins were trapped at the origin, contribution of the PCP-derived dioxins in overall Tokyo Bay gradually increased toward Ichihara Anchorage, indicating the impact of localized dioxin contamination on a large proportion of Tokyo Bay. We suggest that, in addition to runoff from rice paddies (to which PCP had long been applied as herbicide) at the basin, Ichihara Anchorage serves as a significant source of PCP-derived dioxins especially in eastern Tokyo Bay.