Bor, Krivelj, and Bela Rivers belong to the watershed of Timok River, which is a tributary of transboundary Danube River. These rivers receive metal-rich acidic wastewater from metallurgical facilities and acid mine drainage (AMD) from mine wastes around Bor copper mines. The aim of this study was to determine the mobility and natural attenuation of metals and arsenic in rivers from Bor copper mines to Danube River during the year 2015. The results showed that metallurgical facilities had the largest impact on Bor River by discharging about 400 t of Cu per year through highly acidic wastewater (pH = 2.6). The highest measured concentrations of Cu in river water and sediments were 40 mg L and 1.6%, respectively. Dissolution of calcite from limestone bedrock and a high concentration of bicarbonate ions in natural river water (about 250 mg L) enhanced the neutralization of acidic river water and subsequent chemical precipitation of metals and arsenic. Decreases in the concentrations of Al, Fe, Cu, As, and Pb in river water were mainly due to precipitation on the river bed. On the other hand, dilution played an important role in the decreases in concentrations of Mn, Ni, Zn, and Cd. Chemically precipitated materials and flotation tailings containing Fe-rich minerals (fayalite, magnetite, and pyrite) were transported toward Danube River during the periods of high discharge. This study showed that processes of natural attenuation in catchments with limestone bedrock play an important role in reducing concentrations of metals and arsenic in AMD-bearing river water.

Mining activities in the Bor and Majdanpek mining areas in Eastern Serbia started in 1903 and 1961, respectively. Environmental problems in the Bor mining area began after the opening of the Bor mine. Long‐term pollution of river water in the Bor and Majdanpek mining areas has an environmental impact on East Europe because all of the river water from these mining areas flows into the Danube River. However, the sizes of areas with pollution and the differences between the environmental impacts of the Bor and Majdanpek mining areas are not clear. In order to determine the effects of mining activities on river water in the study area, creation of geochemical maps showing the distributions of sulfate, heavy metals, and arsenic; estimation of threshold values to discriminate anomalous values from background values; and comparison of the environmental impacts of the two mining areas were carried out. High concentrations of SO42−, Fe, As, Cu, and Mn were found in the Bor River, Krivelj River, and Bela River located in the Bor mining area. These rivers are characterized by acidic pH ranging from 2.9 to 6.2. High concentrations of these components were also measured in the Small Pek River and the upper reach of the Pek River. These rivers are located in the Majdanpek mining area and are characterized by weakly alkaline pH (7.3–8.4). The acidic river water in the Bor mining area transports large quantities of heavy metals and arsenic downstream (6,900 t/year of Fe, 42 t/year of As, 910 t/year of Cu, and 187 t/year of Mn). On the other hand, the weakly alkaline river water in the Majdanpek mining area transports smaller quantities of heavy metals and arsenic downstream (160 t/year of Fe, 0.1 t/year of As, 6 t/year of Cu, and 272 t/year of Mn). The environmental impact of the Bor mining area is significantly larger than that of the Majdanpek mining area. In addition, on the basis of the distribution of anomalous values in river water, pollution caused by mining activities reaches the Danube River, which is located more than 100 km from the Bor and Majdanpek mining areas. Concentrations of SO42−, Fe, As, Cu, and Mn in the Bela River in the Bor mining area have been greatly decreased after mixing of acidic polluted water of the Bela River with water of the Timok River containing a high bicarbonate concentration. This fact suggests that river water in the Bor and Majdanpek mining areas has sufficient capacity for neutralization. Considering appropriate countermeasures of environmental reclamation, such as artificial neutralization at some important sources of waste water before discharging the waste water from the mining sites, there is a possibility for environmental reclamation in both mining areas because unpolluted river water in the study area has sufficient capacity for neutralization in a natural system.

A natural zeolite from Serbia was employed for the removal of heavy metals from acid mine drainage (AMD) generated in the area of copper mine. The efficiency of the natural zeolite samples was tested on AMD that contained manganese, copper, zinc, nickel and cadmium ions in the concentrations above the maximal allowed, according to existing legislation. The results of X-ray diffraction (XRD) analyses of natural zeolite having a particle size of ¹1 + 0.3 mm, confirmed that the clinoptilolite (Al 1.6 H 30 Ca 2.06 O 47.56 Si 16.4 ) is a dominant mineral of mine tuff. A dynamic method was used for the experiments in order to simulate real conditions in an industrially relevant environment. The effect of the flow rate of AMD, type of columns and zeolite classes on the degree of adsorption of the heavy metals from AMD was investigated. The results of chemical analyses of treated AMD samples at a flow rate of 0.0033 dm 3 s ¹1 which corresponds to the spontaneous outflow from the real accumulation indicate that concentrations of heavy metals are not decreased below that allowed for defined recipient class, except for copper. Also, these results show that the heavy metal ion removal serie for the industrially relevant environment can be given as: Cu > Zn > Cd > Mn > Ni.

Dust from an electric arc furnace is formed as the main by-product of the steel production process from the secondary iron-based raw materials. This dust has significant contents of Zn and Fe, as well as Pb, Cd, Ca, Mg, Cr, Mn, Si, Ni, Cu, F, Cl and other elements and is considered hazardous industrial solid waste since it contains heavy metals. In order to protect the environment and public health from the negative impact of this type of hazardous waste, it is necessary, even mandatory, to carry out its treatment in accordance with the legislation of the country where it is located. Before applying any treatment of the electric arc furnace (EAF) dust, it is necessary to perform its detailed characterization. In this paper, the following characterization of EAF dust originating in the Republic of Serbia was performed: physical-mechanical and chemical characterization, determination of granulometric composition, and mineralogical characterization. Also, the EAF dust impact on the environment and human health was assessed (Leachability and Toxicity Characteristic Leaching Procedure (TCLP) tests). The results have shown that the Zn content is in the range 32 to 35 % and that the main mineralogical phases of the dust are zincite, franklinite, magnetite, and magnesioferrite. Granulometric analysis has shown that 80 % of the sample consists of particles less than 26 ?m in size. According to the leaching test results, the EAF dust is characterized as a hazardous waste due to the increased chloride content, while the TCLP test indicated dust toxicity due to the increased contents of Zn, Cd, and Pb.