Characteristics of Heavy Metals in the Bottom Mud of Mining and Urban Rivers

Abstract

In order to separate the different forms of heavy metals contained in bottom mud of urban and mining rivers, fractionation of metals by chemical extractants was carried out. Heavy metals were fractionated by successive extraction with 2N-CH₃COONH₄, 0.1M-EDTA and 0.5N-HC1, and by decomposition with HNO₃-H₂O₂. The lattice-held metals, which were separated by HNO₃-H₂O₂ decomposition, were 70-80% of the total in the bottom mud receiving waste water from mining industry, suggesting that the most of these metals were composed of ore minerals. On the other hand, the fraction of HNO₃-H₂O₂ was only 20-30% in urban rivers receiving industrial or municipal waste water. The major fractions of the heavy metals were separated with 2N-CH₃COONH₄ or 0.1M-EDTA. It was suggested that large parts of Cd, Zn, and Cu in the mud of urban rivers bind weakly with clay or organic matter and Pb binds more strongly with organic matter.