The study area is within the Bor copper mining region, Eastern Serbia, where wastewaters from the Bor metallurgical/smelting facilities have caused serious copper (Cu) and arsenic (As) contamination to the Timok river system. The operating conditions at smelting facilities control the pH of the river waters, resulting in highly acidic waters in 2019 than 2015. This study compares the mobility of Cu and As and risk assessment of river water contamination during both years as well as assessing the risks of riverbed sediments contamination and investigating the origins of Cu and As pollution. In the river system, As generally existed as a particulate species in the entire study area during both years and was widely removed from river waters by sorption onto the hydrous ferric oxides (HFO), whereas dissolved Cu was removed from river waters only at neutral pH conditions with hydrous aluminum oxides (HAO) and HFO at the downstream reservoir site of Timok River. Despite the similarity in Cu mobility during both years, the lower pH of river waters in 2019 than 2015 enabled dissolved Cu species to be transported farther downstream, resulting in a higher level of river water pollution. The contamination factor (CF), used to estimate levels of sediment pollution, had higher values for Cu and As compared to Zn, Pb, Co, and Ni. The CF values of Cu were the highest in sediments near the Bor metallurgical/smelting facilities and at downstream reservoir site, whereas the CF values of As were generally high in the entire research field. Additionally, the ecological risk potential (Er) values of Cu were the highest in sediments of the Bor River and Timok River, reflecting an enrichment of Cu at these sites. Finally, a clarification on the origin of Cu pollution and risks of mobilization was inferred from the sequential extraction test. The predominant Cu species in sediments of the upstream region were oxidizable and residual, hosted by copper sulfides originating from the flotation tailings, suggesting a relatively low risk of Cu release from these sediments. However, at the downstream site (especially reservoir sediments), the contribution of acid‐soluble Cu was 34.8%, suggesting a higher risk of Cu release. The highest contributions of acid‐soluble and reducible Cu (18%) at the reservoir site were promoted by the effective settlement of Cu‐sorbing HAO and HFO. The Cu contents of these two fractions were 0.86 wt%, almost three times higher than that of Cu ore in Veliki Krivelj open pit mine.

In the study area of eastern Serbia, which includes the Bor and Maidenpek mining areas of the Republic of Serbia, a research of environmental evaluation of the study area was carried out by means of field survey for environment and satellite image analysis in order to establish and improve methods for assessing the environmental impact of mining areas by satellite image analysis. The results of this study showed that it was possible to efficiently determine the distribution of overburdens and tailings in a wide area based on the distribution of points having jarosite spectra, and that it was possible to distinguish waste rocks such as overburdens and tailings with high environmental impact from those waste rocks with relatively low environmental impact based on the mineral assemblage of the waste rocks estimated from satellite image analysis. In addition, if topographical data before and after mining development are obtained from the satellite image analysis, the volume of the waste rocks can be estimated, and the quantitative estimation of the amount of toxic elements dissolved from the waste rocks could be possible by combining the experimental data on the extraction of toxic elements from the waste rocks. In addition, the predicted hazardous area (Type I), where high concentration of Cu may be leached from the waste rocks revealed by the surface survey, corresponds to the area where waste rocks such as overburdens and tailings is distributed around the mine and the area where waste rocks such as tailing is distributed along the river downstream of the mine as estimated by the satellite image analysis. These results indicate that it is possible to predict the environmental impact in advance of the survey in the mining area, and to predict the environmental impact in the mining area where it is not possible to go directly to the survey and to consider guidelines for countermeasures.