Spatial distribution and corresponding determining factors of metal concentrations in surface sediments of Beppu Bay, southwest Japan.

This study determined the factors contributing to the spatial distribution of 14 metal concentrations in the surface sediments of Beppu Bay on the basis of comparisons of the organic geochemical properties and environmental parameters through principal component analysis (PCA) and redundancy analysis (RDA). The results of PCA and RDA showed that the concentrations of V, Cr, Co, and As were closely related to the distances between the sampling sites and the Oita River. This indicated that these metals originated from the river's drainage area. The Mn, Cu, Mo, and Cd concentrations were related to the water depth. These results indicated that the Mo, Cd, and Cu deposition processes were controlled by oxygen depletion, and that these elements accumulated in the deeper parts of the bay under anoxic conditions.