The Mobility and Phytotoxicity of Trace Elements in Metalliferous Mine Tailings.

For remediation of toxic trace elements contaminated soils, management of their mobility is crucially required. In particular, since mine tailings contain As and heavy metals mainly as a stable form, better understanding and controlling of As and heavy metal mobility in mine tailings is essential. Hence, the present study was conducted to evaluate mobility of As and heavy metals together with total contaminations in metalliferous mine tailings. In addition, using phytotoxicity assay technique, environmental impact of the extent of trace elements mobility in mine tailings was examined. For the chemical distribution and leachability of As, Cd, Pb, Cu, Ni, and Zn in the mine tailings, sequential extraction method, synthetic precipitation leaching procedure (SPLP) and toxic characteristic leaching procedure (TCLP) were introduced in association with aqua regia extraction for total metal contaminations. After that, regression analysis was conducted to examine the relationship among the data from each extraction. The results appeared that despite high concentration of trace elements in all main tailing samples examined, the fraction of mobile trace elements were relatively low because they were mainly associated with stable fraction. There were significantly positive correlations between mobile fraction of trace element examined by sequential extraction and the leachable fraction examined by leachability tests except for SPLP. With most elements examined SPLP contents were strongly correlated with water-soluble fraction obtained from sequential extraction. According to phytotoxicity assay, mobile fraction of As and heavy metal provided better prediction of root growth response in lettuce than total concentration of As and heavy metals. Particularly, principle component analysis (PCA) and multiple regression analysis showed that mobile As content in the mine tailings was the most critical factor affecting phytotoxicity in lettuce implying As associated with mobile fraction in mine tailings would play a more important role in mine tailings-induced toxicity.