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.