Abstract
The study was conducted to determine the concentrations of metals (Cd, Co, Cr, Cu, Mo, Ni, Pb and Zn) and their association with various geochemical substrates in sediments of Old Nakagawa River, Tokyo, Japan. Hall sequential extraction procedure was employed for the fractionation of metals and the concentrations were measured in the liquid extracts by inductively coupled plasma mass spectrometry (ICP-MS). The association of Cd (76-98%) and Zn (48-67%) were found highest with AEC (adsorbed/ exchangeable/ carbonate) phase; Cu (45-60%), Ni (18-40%) and Pb (44-73%) with amorphous Fe oxyhydroxide phase, and the maximum fractionation of Co, Cr and Mo were in both crystalline Fe oxide (12-43, 12-60 and 11-70%, respectively) and amorphous Fe oxyhydroxide phase (20-35, 15-60 and 15-40%, respectively). The observed order of potential trace metal mobility in the aquatic system was: Cd > Zn > Pb > Cu > Ni > Cr > Co > Mo. The sediments of Old Nakagawa River was considered to be polluted on the basis of unpolluted sediments and geochemical background values with respect to Cd, Cr, Cu, Pb, Mo and Zn. Only the AEC fraction was surpassed the toxicological reference values for Cd, Cr, Zn, Cu and Ni recommended by the U. S. Environmental Protection Agency (US EPA). According to the enrichment factors (EFc), geoaccumulation index (Igeo) and pollution load index (PLI), most of the sites have higher values for Cd, Cr, Cu, Pb, Mo and Zn. However, on the basis of marine sediment pollution index (MSPI), the sediment quality range was good to bad although the mean value indicated average quality of sediments of Old Nakagawa River. The study will also make some recommendations to clean up the river systems.
