Heavy metal concentration of river sediment in the light of the environmental quality standard value of Japan from the river in and around the Tokyo Japan: A case study at the Tama, Tsurumi, Edo and Ara rivers

The river sediment is basically composed of clastic materials derived from the surface of the Earth. Purpose of our study is clarify the quantitative estimation of ratio of influence given to river sediment of nature and human activity by using of heavy metals. We show the geochemical and geological characteristics of stream sediments from the Tama, Tsurumi, Edo and Ara Rivers that flow in Tokyo bay, Japan. We show research results of the degree of contamination in above four rivers that are the relativery polluted river in Japan. Sediment samples collected from various points along the upper and lower streams were subjected to content analysis and elution analysis (using liquate (flow) out test) on the heavy metals like Cd, CN, Pb, Cr(6+), As and Hg from the river sediment for the purpose of environment assessment. Content of Cd, CN, Pb, Cr(6+), As, and Hg except Pb was above the environmental quality limit in few locations of the Tsurumi river. However, in the down-river part (mouth region) Pb-concentration was 10 times higher than at the source regions as the result of human impact; for Hg the same tendency was detected at the all rivers. This study is the first research that investigated river sediment in the light of the envirnomental quality standard in Tokyo area, Japan.