Assessing soil contamination in a mining city using Cu, Mo, Pb, and Zn isotopic ratios and PMF analysis

초록

Soil contamination poses significant threats to the environment and human health in mining cities, yet studies utilizing Cu, Mo, Pb, and Zn isotopes and positive matrix factorization (PMF) to identify soil contamination sources remain scarce. This study investigated soil contamination in Erdenet, a city located near one of the world's largest Cu-Mo mines in Mongolia. Soil in the region was found to be contaminated with As, Cu, and Mo. Through the use of isotopic ratios of Cu, Mo, Pb, and Zn, combined with PMF analysis, it was determined that dust from the tailings dump resulted in soil contamination extending as far as the eastern residential area of Erdenet. Despite the possible fractionation of Cu and Zn isotopes during leaching and weathering, the isotopic ratios of Cu, Mo, Pb, and Zn effectively identified contamination sources. While certain soil samples in the ore areas showed substantial delta 65Cu depletion by several per mil likely due to longterm surface leaching processes, weathering over the past few decades is unlikely to have significantly altered the isotopic fingerprints in soils. Specifically, delta 65Cu and delta 66Zn reflected both leaching zones and contamination sources, whereas delta 98Mo and 208Pb/206Pb primarily reflected contamination sources, likely due to minimal isotopic fractionation during dissolution. These findings indicate that combining and selecting specific metal isotopes can enable both source identification for certain metals and leaching zone assessment in mining areas. Implementing dust prevention measures at the tailings dump is crucial for mitigating soil contamination in both the tailings area and the eastern residential area.

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