Chemical speciation of metals in surface sediments from small urban and agricultural rivers.

Characteristic distributions of Al, Mn, Fe, Ni, Zn, and Pb were investigated in the surface sediments of a small river (Niitsu River) flowing through both urban and agricultural areas, along with comparison with those from the upper main stream (Nodai River). The mean compositions of the most mobile metals were ordered as Zn = Mn > Ni = Pb = Fe > Al in the Niitsu River. They were Mn = Zn = Pb = Fe > Ni = Al in the Nodai River. Mn, Fe, Ni, and Zn in the Niitsu River showed higher compositions of mobile (2.9%-36%) and oxidizable (6.6%-16%) phases than those in the Nodai River. The Ni and Zn in the Niitsu River also had higher reducible phase composition (15% and 16%, respectively). In the Niitsu River, Pb had the higher oxidizable composition (29%). Over 90% of Al was in the lithogenic phase in the two rivers.