Characteristics of Chemical Composition of Main Components of Landscapes in the Southern Mining Regions of Mongolia

Abstract

Currently, change of ecological conditions in new mining regions under development in South Gobi (Ömnögovi) aimag of Mongolia is an extremely urgent problem due to insufficient knowledge about the territory, increase in production rate, and discontent of public organizations and local populations as a result of environmental degradation. In summer 2024, field investigations were conducted by the present authors in the Gobi Desert (Mongolia), including sampling of soil and groundwater, in the deposit and mining regions of coal “Tavan Tolgoi” and copper “Oyu Tolgoi”, as well as chemical-analytical works. The goal of the present work was to assess the contemporary ecological state of soils and groundwater in the mining sums Khanbogd and Tsogttsetsii in South Gobi (Ömnögovi) aimag of Mongolia. Mineralization level and content of major ions in groundwater and soil aqueous extracts corresponds to the natural–climatic conditions of the dry-steppe and semi-desert zone. Concentration of contamination elements and substances (As, HM, and petroleum products) in the water and soils indicates challenging ecological situation in the mining regions. As a result, the investigation revealed largely fresh groundwater in copper-mining area and brackish (slightly saline) groundwater in coal-mining area. Point sources of groundwater and soil contamination were detected in the territory of farm holdings located in the proximity to mining enterprises. High concentrations of ions of sodium, fluorine, magnesium, chlorine, sulfates, and a numbers of HMs were found in waters of wells and boreholes of the local residents. According to the water pollution index (WPI), groundwater quality (in wells and boreholes) varies from “clean” (WPI = 1.03) to “polluted” (WPI = 2.11). Increased contents of nickel, copper, zinc, and arsenic, exceeding the sanitary and hygienic standards, were detected in soils of the same territories. Values of the composite contamination index of soils (∑с) vary between 3.7 and 24.9, which corresponds to the acceptable and moderately hazardous categories.