Distribution and transition of heavy metals in mine tailing dumps

The vertical distributions of heavy metals and other elements in sediment core samples in a landfill of abandoned mine tailings were examined. Core samples were analyzed by XRF and XRD, and further examined by ICP-AES measurements after acid-sequential extraction with HCl, HF, and HNO₃. According to XRD, the sediments contained α-quartz as the main component, and sericite, chlorite, rhodochrosite, pyrite, jarosite, sphalerite, and galena as minor components. A complete decomposition method using sequential extraction for the mine tailings sediments was established at ambient temperatures. Acid sequential extraction was useful for the analysis of minerals in mine tailings which are difficult to detect by XRD. Rhodochrosite and chlorite were dissolved by HCl-extraction, quartz and sericite by HF-extraction, and sulfides by HNO₃-extraction. Rhodochrosite was the main source of high concentrations of Mn in mine drainage, highly distributed below the - 100 cm zone in the mine tailings, combined with pyrite but not with sericite and quartz. The distributions of most heavy metals were related to those of pyrite.