Professor, Department of Environmental and Life Sciences, School of Food and Nutritional Sciences, University of Shizuoka, Japan

Speech Title: Analysis of historical trend of pollution sources of zinc in Tokyo Bay based on zinc isotope ratio in sediment core

Abstract: Clarifying the sources of toxic substances in aquatic environments is essential for achieving the effective reduction of their environmental risks and the conservation of ecosystems. Tokyo Bay is surrounded by a densely populated and highly industrialized area, and the recent concentrations of some toxic metals, including Zn, Cd, and Pb, in sediments are sufficiently high compared with their background levels. This suggests that there are still important sources of the metals in the bay. In this study, we investigated the historical trend in pollution sources of Zn in Tokyo Bay on the basis of Zn isotope ratio (δ⁶⁶Zn) in a sediment core. The Zn isotope ratio may provide useful information on the sources of Zn in environmental samples if each source of Zn has distinctive isotope ratio. The δ⁶⁶Zn in the sediment core showed a similar historical trend to that of the Zn concentration. The δ⁶⁶Zn values of anthropogenic Zn in the core were estimated using the two-component end-member equation. To date, it is likely that anthropogenic Zn in Tokyo Bay is originated from sources other than atmospheric deposition, vehicle exhausts and tires, road debris, and treated water from sewage treatment plants, on the basis of the δ⁶⁶Zn values of their sources.