Soil contamination around porphyry copper mines: an example from a semi-arid climate.

Extraction and processing of disseminated metalliferous ores, porphyry copper in particular, results in significant tonnages of waste and can cause severe disturbances and contamination in natural ecosystems. This is particularly important in semi-arid climates where natural soils are often deprived of organic matter and nutrients. This study was conducted on seven sites around Sungun Copper Mine, northwest Iran. Soil texture, EC, pH, and concentrations of nutrients, organic matter, along with 16 metal and metalloids were measured in 94 soil samples. Results showed a gradient of contamination from low contamination in natural hillsides to high contamination in mine waste depositories, Waste Dump and Oxide Dump, alongside Pakhir and Sungun Rivers. Nutrient deficiency occurred in disturbed sites. The main contaminant point sources were Waste Dump, mine pit drainage, and Oxide Dump. The results of Non-metric multidimensional scaling ordination showed elevated Cd, Zn, Fe, Cu, Pb, As, Mo, Mn, Co, S concentrations, high EC, and higher sand percentage in the sites affected by mine waste and acid mine drainage. Geo-Accumulation and Potential Ecological Risk Indices indicated that Pakhir riverside, Sungun riverside, and Oxide Dump have severe to moderate levels of environmental risks. Positive correlations between certain metal elements suggest common sources and similar reaction pathways, which may contribute to their similar geochemical behaviour in transport, deposition, and interdependence. Overall, the deficiency of organic matter and nutrients along with the soil sandy texture in contaminated sites of Sungun Copper Mine are the main limiting factors in managing metal mobility and soil remediation.

Metal and metalloid accumulation in native plants around a copper mine site: implications for phytostabilization.

Mining activities can result in a pollution legacy of metal and metalloid containing soils and wastes. In this study concentrations of the metals and metalloids Al, As, Ca, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Zn, and the non-metals (P, S) were measured in the shoots of 35 different plant species spontaneously growing at four contaminated sites around the Sungun Copper Mine in East Azerbaijan (Iran) in order to evaluate their potential in phytoremediation of this area. The results show that metal and metalloid accumulation differed between the different species. None of the plant species exceeded the relevant trace element hyperaccumulation thresholds. Plant accumulation of Al was found to be relatively high in Achillea vermicularis (Asteraceae, with up to 5,280 µg g-1) and in Trifolium fragiferum (Fabaceae, with up to 4,895 µg g-1). Papaver dubium (Papaveraceae) had relatively high foliar Cu concentrations (with up to 294 µg g-1) while growing in the waste Rrock dump. Teucrium polium (Lamiaceae) had the highest concentrations of Pb (with up to 62 µg g-1). Most of the native species can be classed as metal-tolerant "excluder"-type species, and may, therefore, be suitable for phytostabilization of the mining wastes around the Sungun Copper Mine.

Plants growing on metalliferous soils are threatened by mining and mineral extraction. Identifying the flora in metal-contaminated soils and mineral wastes is of great importance for biodiversity conservation and for their use in future reclamation programs. This study adds valuable information on the potential of native plants for use in the phytoremediation of copper mines in Iran, as well as in other parts of the world with a similar geology and climate.