Historical Trend of the Anthropogenic Heavy Metal Pollution in the Estuary Sediment of Osaka Bay, Japan

The concentration of heavy metals such as chromium, nickel, copper, zinc, arsenic and lead were determined in the dated core sediment in order to evaluate the historical trend of the anthropogenic heavy metal pollution in Osaka Bay. The time trends of the pollution profile of the heavy metals were clarified in the core. The pollution of anthropogenic heavy metals began around the Meiji restoration 1860’s. The contamination increased by 1960’s and decreased from 1970’s to the present. The dramatic decrease of the metal concentration in the sediment after 1970's has shown the result of the legal regulation in Japan. The concentration of these pollutant elements showed the mutually high correlation in the sediment. It is shown that the pollution of Osaka Bay by the heavy metals originated from the industrial activity of the urban district in the coastal area. The correlations of the metal concentrations and the total sulfur (TS) concentration were also very high, and it is indicated that the contaminated heavy metals were being fixed in the sediment as a sulfide.