Relationship between distribution of heavy metals and sedimental condition in the sediment of Osaka Bay

Abstract

The concentrations of heavy metals (Hg, Cd, Cu, Zn, Pb, Ni, Mn, Cr, Fe) were determined in surface sediment samples collected from Osaka Bay and Otsuchi Bay, Japan in 2000. Mean concentrations (μg/g dry wt) of heavy metals in sediments from Osaka Bay were as follows: Hg 0.34; Cd 1.23; Cu 44.9; Zn 242; Pb 57.8; Ni 37.8; Mn 888; Cr 49. The concentrations of heavy metals were higher in sediments from the northeastern parts of Osaka Bay. This is probably due to industrial and domestic wastewater delivered by rivers through large cities. Highly significant correlation coefficients were observed among the concentrations of heavy metals except for Mn. Mean levels of heavy metals in sediments of Osaka Bay were several times higher than those of Otsuchi Bay which is a non-industrialized area. The distribution patterns of heavy metals, ignition loss and chemical oxygen demand were fairly similar, and inversely correlated with those of sediment grain-size in Osaka Bay. From these results, it is considered that the sediment grain-size and organic substance contents are probably the crucial parameters that control the concentration of heavy metals except for Mn.