Historical changes of environmental pollution based on concentrations of heavy metals and lead isotope ratios in bottom sediment core at Nagasaki-bay

Takasaka, Yuiko*; Katahira, Kenshi*; Moriwaki, Hiroshi*; Yamazaki, Hideo*; Kokubu, Yoko   ; Yoshikawa, Shusaku*

Metal concentrations and lead isotope ratios in a bottom sediment core from Nagasaki-bay in Japan were measured by ICP-MS following the microwave extraction method. Before 1920s, metal concentrations in the sediment core samples were low and lead isotope ratios were near those of Japanese lead ore. From the middle of the 1930s, environmental pollution by heavy metals would become visible around Nagasaki-bay because the metal concentrations in the sediments increased and lead isotope ratios were changing. Spiked peaks for several metals in the sediment core samples were observed around 1960 when industry was developed rapidly. The amount of heavy metals released to the environment would have decreased by the law for the environmental pollution enforced in 1976. In this way, metal concentrations and lead isotope ratios in sediment core reflected the activations of industry and could reveal environmental changes for 100 years around Nagasaki-bay.