The species and geochemical characteristics of heavy metals in the sediments of Kangjiaxi River in the Shuikoushan Mine Area, China

The different geochemical species of heavy metals in sediments in the Kangjiaxi River, Shuikoushan Mine Area, were separated and analysed. The exchangeable proportions of Pb, Zn and Cu in sediments are very low, never exceeding 1.5%, but the proportion of exchangeable Cd is as high as 10–15%. The CO3 form of Cd, Cu, Pb and Mn in total increases. The proportion of this form of Ca in total is very high (11–16%) which indicates that in the HCO3− and Ca2+ system in Kangjiaxi river water, under the present alkaline conditions (pH 7.6–7.8), the trace metals co-precipitate strongly with CO3. The heavy metals in the forms of Fesingle bondMn oxides are the main existing forms in the non-residue fractions. These forms of Cd, Zn and Pb occupy a total of 21–52%, 29–54% and 65–79%, respectively and the proportions of this form of Mn reach 65–79%. This shows that the precipitation effect of Fesingle bondMn oxides in water is very strong and it is also the main characteristic of heavy metals in the sediments in the subtropical climate.