The surface of particles in Tamagawa estuary and Tokyo Bay and their influence on the distribution of trace elements

Abstract

The surface and bulk chemical composition of suspended particles (SP) from the Tamagawa estuary and Tokyo Bay have been studied. X-ray photospectroscopy (XPS) was used for the surface analyses. By comparison with bulk analysis, it was found that there was a surface layer enriched in organic matter and manganese, and that such the particles were coexisting. Silica may also be adsorbed onto the surface, but is depleted relative to the bulk nevertheless. The organic matter in the surface is considered to be humic acids from its chemical composition, and becomes the dominant substance on the surface with increasing depth and distance offshore, overwhelming silicates and oxides. The effect of such particles on dissolved trace metals was investigated by comparing their concentration gradients with the coverage of humic acid, silicates and oxides in the surface. The concentration gradients of dissolved Ni, Cu and Zn correlate better with the surface areas of Al, Fe and Mn than with that of organic matter, suggesting the former are more effective adsorbers of metals than the latter.