The impacts of alkaline mine drainage on Ba, Cr, Ni, Pb and Zn concentration in the water resources of the Takht coal mine, Iran

Abstract

The release of heavy metals into the environment represents one of the most important environmental effects involved in extracting coal; it needs to be studied more fully. The present research investigatedthe effects of coal-mining in an alkaline environment and alkaline mine drainage in the Takht coal mine regarding the distribution of selected heavy metals (Zn, Pb, Ni, Cr and Ba) on the region's surface andground water . The mine is located 12 Km southeast of Minoodasht, in Golestan province in northern Iran. Samples were collected from groundwater and surface water resources upstream and downstream of themine. The elements' concentrations were measured by the inductively-coupled mass spectrometry (ICPMS) method. The results showed that an alkaline environment was responsible for producing alkaline minedrainage due to the presence of limestone; this caused high pH (8.41) in the area's groundwater resources. Mining activities increased Ba, Cr, Ni, Pb and Zn concentration in the groundwater from 3.39, 0.5, 0.2,0.5, 9.2 ppb to 83.52, 2.2, 0.6, 2.6, 48.3 ppb and from 68.7, 0.5, 1.3, 0.8, 172.6 ppb to 91, 1.2, 4.5, 1.3, 27.6 ppb in surface water, respectively. Due to the basic environment, heavy metal accumulation in the bedsediment for both tunnel effluents and runoffs was higher than during the soluble phase. pH was the main controlling factor in elements' solubility and their distribution in the environment. Increased Ba concentrationin water resources was due to high Ba concentration in the coal, coal tailing and in quarry tailings.