Transportation and Sources of Dioxins and Dioxin-like PCBs in Rivers Flowing into Tokyo Bay

Abstract

The amounts of dioxins (PCDD/Fs) and dioxin-like PCBs transported by rivers from various sources to Tokyo Bay were estimated. River water samples were collected at six stations in six different rivers (Edo River, Naka River, Ara River, Sumida River, Tama River and Tsurumi River) from April 2001 to July 2003, and the concentrations of PCDD/Fs and dioxin-like PCBs in these rivers were determined. On the basis of these results, the annual amounts of PCDD/Fs and dioxin-like PCBs transported by each river to Tokyo Bay were estimated. It was estimated that 10 g-TEQ (particulate phase) and 2.3 g-TEQ (dissolved phase) were transported to Tokyo Bay annually in recent years. Also, the contributions of sources of PCDD/Fs and dioxin-like PCBs in these rivers were estimated by a chemical mass balance (CMB) approach. In Tama and Tsurumi Rivers, it was estimated that more than 85% of total TEQ originated from combustion, while the contribution of combustion was less than 60% in the Ara River. Moreover, the amounts of PCDD/Fs and dioxin-like PCBs transported from each source were estimated, assuming that the contributions of sources in a river are constant in recent years. It was estimated that 8.4 g-TEQ, 1.1 g-TEQ, 0.45 g-TEQ, 1.2 g-TEQ originating from combustion, PCP, CNP and commercial PCBs, respectively, were transported to Tokyo Bay annually.