Determination of environmentally safe chromium concentration in mountain-meadow chernozem-likes soil in the vicinity of a mining enterprise

Introduction. Chromium (Cr) is one of the most toxic heavy metals. The pulp of the Urup Mining and Processing Plant (MPP) contains a high concentration of Cr up to 1370 mg/kg. At the same time, the maximum permissible concentration of Cr in the soil (0.05 mg/kg) is not consistent with its natural content in the soil (up to 130 mg/kg). To assess the impact of the Urup MPP tailing dump on the adjacent mountain-meadow chernozem-likes soils, it is advisable to determine the environmentally safe Cr content. Materials and methods. Cr (VI) contamination of mountain meadow chernozem soil was simulated in laboratory conditions. Chromium was introduced into the soil in concentrations 10, 25, 50, 100, 250, 500 mg/kg. The exposure period of the model experiment was 30 days while maintaining constant humidity and temperature. At the end of this period, in all samples of mountain meadow chernozem soil there were determined biological indicators: the number of soil bacteria, indicators of enzyme activity, root length and germination of radishes. Results. Cr contamination of mountain-meadow chernozem-likes soil was found to lead to inhibition of biological parameters. An inverse relationship has been established between the Cr concentration and the biological parameters of the soil. In the vicinity of a mining enterprise in a mountain-meadow chernozem-likes soil, a concentration of 125 mg/kg should be taken as an environmentally safe Cr concentration. Limitations. Environmentally safe concentrations can be used primarily as a local environmental standard for the Cr content in the soil in the area of the mining and processing plant. Conclusion. The proposed environmentally safe concentration of Cr around a copper mining enterprise can be recommended for use by institutions in the field of environmental protection, agricultural and scientific activities.