Influence of ore deposits on river sediment compositions in Dan River drainage, China

We mainly investigated trace element contamination of surface sediments in the Dan River drainage, the source of drinking water for the South to North Water Transfer Project, China, to determine trace element sources and associated levels of risk. Sediment samples were collected at 95 sites along the Dan River in connection with field surveys, and total element concentrations were determined using inductively coupled plasma-mass spectrometry (ICP-MS). Concentrations of most elements were lower than background levels; however, toxic heavy metals, such as As, Cd, Pb, and Sb, showed extremely high concentrations at sites associated with nearby metal ore deposits. Moreover, the spatial variations of contamination by some heavy metals were directly related to the distributions of metal ore deposits in the North and South Qinling terrains; sediment samples with especially high concentrations of Sb and As were from the North Qinling terrain, while sediments with especially high concentrations of Cd and Pb were from the South Qinling terrain, suggesting that metal ore distributions and associated mining activity strongly influence the distribution of heavy metals and heavy metal contamination in the Dan River drainage. Multivariate techniques, including Pearson correlation, hierarchical cluster, and factor analysis, were used to assess the sources of metal contamination. Results indicate that distributions of Al, Ba, Cu, Fe, Mg, Mn, Pb, Sn, Ti, V and Zn are controlled by natural sources; Co and Cr by a combination of geological and anthropogenic inputs; whereas As, Cd, Ni, Sb, and Pb appear to be primarily of anthropogenic origin. The ecological risk associated with heavy metal contamination of sediments was rated as moderate, based on an assessment using geo-accumulation index (I_geo), enrichment factor (EF), potential ecological risk index (RI) and mean probable effect concentration quotient (m_PECQ).