The decoding of recent environmental history using the Lake Biwa sediments

点击翻译按钮获取中文摘要

The historical trends of the environmental pollutions recorded in the Lake Biwa sediments were analyzed. Estimations of the accumulation rates of the sediments were carried out by the 210Pb and the 137Cs techniques. The heavy metals, such as Cr, Ni, Cu, Zn, As, Hg, and Pb, were used as a maker of the anthropogenic pollutions. The vertical profiles of Cr and Ni in the sediments show constant distributions, whereas the concentrations of other heavy metals increased in the upper layer of the sediment. The contaminations of the heavy metals in the sediments could be explained by an anthropogenic discharge from the hinterland and its historical changes. Whole inventories of the heavy metals were calculated in the sediment of the north basin for 100 years from 1900s, at 465 tons for Cu, 1050 tons for Zn, 2.8 tons for Hg, and 284 tons for Pb. In addition, the composition of the major elements in the sediments was analyzed in concentration correlation matrix and cluster analysis in order to clarify the correlation of chemical characteristics of the sediments between the sites. The generic correlations among the sampling sites of the Lake Biwa sediments could be explained by the physical and chemical redistribution of the components during the processes in which the sedimentary materials are transported through the lacustrine water currents.