Mobility and natural attenuation of metals and arsenic in acidic waters of the drainage system of Timok River from Bor copper mines (Serbia) to Danube River

Abstract

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.

Estimation and comparison of the environmental impacts of acid mine drainage‐bearing river water in the Bor and Majdanpek porphyry copper mining areas in Eastern Serbia

“… aDordievski et al . (2018); T, total concentrations; D, concentrations of dissolved fractions; P, concentrations of particulate fractions; MAX, maximum concentrations in river water from unpolluted areas; MIN, minimum concentrations in river water from unpolluted areas; Mean, mean concentrations in river water from unpolluted areas; Detection limit: Fe = 10 μg/L, As = 0.03 μg/L, Cu = 0.2 μg/L, Mn = 0.1 μg/L, Zn = 0.5 μg/L, Cd = 0.01 μg/L, Pb = 0.01 μg/L.…”

“…The dominant chemical fraction of Cu in acidic river water of the Bor River, Bela River, and Krivelj River (B1–B7 and K3–K4) was the dissolved fraction (Figure 6). On the other hand, the particulate Cu was dominant in water having a neutral to alkaline signature in the Timok River downstream of the confluence of the Bela River and Timok River (B9–B13) (Dordievski et al ., 2018). The chemical fraction of Cu differed greatly before (B8) and after (B9) mixing of acidic water of the Bela River (Ca‐Mg‐SO 4 ‐type water) with weakly alkaline water of the Timok River (Ca‐Mg‐HCO 3 ‐type water).…”

“…In addition, ores from the Majdanpek mine are transported to the smelter in the Bor mine as concentrates and refined into metals with ores used from the ore deposits in the Bor mining area. The waste water from metallurgical facilities (including a smelter) of the Bor mine contains high concentrations of heavy metals and arsenic (Dordievski et al ., 2018). In the Bor mining area, the waste water from metallurgical facilities (including a smelter) is discharged into the Bor River without any treatment.…”

“…The average concentration is only about one‐third of the average bicarbonate ion concentration in unpolluted river water in the study area in Eastern Serbia, where limestone is dominant (Ciobanu et al ., 2002; Kozelj, 2002; Jelenkovic et al ., 2016). Moreover, the concentration of bicarbonate ion in river water in the study area in Eastern Serbia is also higher than the world average of bicarbonate ion concentration in river water in areas where igneous rocks are dominant without limestone (Oyarzun et al ., 2013; Dordievski et al ., 2018). Due to the presence of a high concentration of bicarbonate ion in unpolluted water of the Timok River (Ca‐Mg‐HCO 3 ‐type water), the polluted water of the Bela River is neutralized by the buffering reaction shown below: …”

“…Several studies have been conducted on the quality of polluted river water (Milijasevic et al ., 2011; Ishiyama et al ., 2012; Atanackovic et al ., 2013; Gardic et al ., 2015; Serbula et al ., 2016; Dordievski et al ., 2018; Milijasevic Joksimovic et al ., 2018). Ishiyama et al .…”