Resource conundrum in Mongolia: Soil contamination from coal and copper–molybdenum mining

Abstract

Soil contamination and the resulting ecological disturbances are a common phenomenon in mining areas, including the vicinities of the largest and oldest open‐pit mining areas in Mongolia. In this work, the potential ecological risk index (RI), Nemerow integrated pollution index (PIN), and Geoaccumulation index (Igeo) were used to estimate the level of soil contamination with Ni, Cu, Zn, As, Cr, and Pb in the top layer of the soils around Baganuur coal mine and Erdenet copper–molybdenum mine. Three different analytical methods were used: portable X‐ray fluorescence (pXRF) for the first assessment of samples, and stationary X‐ray fluorescence and Inductively Coupled Plasma Optical Emission Spectroscopy for the confirmation of results in the laboratory. Even though general contamination levels in both study areas were relatively low, some potentially toxic elements were found at contents several times higher than the maximum permissible level (MPL) according to the national standard of Mongolia. In the Baganuur area, Zn was up to 2.8 and As was up to 3.00 times higher, while in the Erdenet area, As was up to 2.4, Cr was up to 1.7, Cu was up to 8.1, and Zn was up to 1.2 times higher than MPL of the national standard in the vicinity to the mining and industrial area. The estimation of the pXRF measurement had generally similar results to the other two laboratory methods based on spatial distributions of heavy metal content. Among the different geochemical indices, the PIN showed a more accurately distinguished spatial distribution of contamination. For example, highly contaminated areas were found in the vicinity of the open pit, the tailings pond and the industrial area based on PIN results: 3.6%–4.9% of the total area in Baganuur and 3.1%–4.9% of the total area in Erdenet. The identified pollution levels emphasize the essential need for soil rehabilitation in mining areas, a key factor for Mongolia's economic development and environmental stability. In addition, the lack of documented soil rehabilitation initiatives underscores the pressing need for enhanced environmental responsibility in the country's expanding mining sector.