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

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 investigated the 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 and ground 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 the mine. 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 mine drainage 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 bed sediment 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 concentration in water resources was due to high Ba concentration in the coal, coal tailing and in quarry tailings. Keywords: heavy metals, groundwater, surface water, sediment, alkaline mine drainage, coal-mining. La liberacion de metales pesados en el medio ambiente representa uno de los efectos ambientales mas importantes en la extraccion de carbon, lo cual necesita ser estudiado con mayor profundidad. El presente estudio investigo los efectos de la mineria del carbon en un ambiente alcalino y en el drenaje de la mina de carbon Takht, con respecto a la distribucion de determinados metales pesados (Zn, Pb, Ni, Cr y Ba) en superficie y en las aguas subterraneas de la region. La mina esta ubicada a 12 km al sureste de Minoodasht, en la provincia de Golestan en el norte de Iran. Se recogieron muestras de aguas subterraneas y aguas superficiales aguas arriba y aguas abajo de la mina. Las concentraciones de los elementos se midieron mediante la espectrometria de masa de acoplamiento inductivo (ICP-MS). Los resultados indican que un ambie