بررسي آلودگي منابع آبي مجموعه معدني ذغالسنگ طرزه با توجه به خصوصيات ژئوشيميايي منطقه

Investigation on Contamination of the Water Resources in Tazareh Coal Mine Complex with Respect to the Geochemical Characteristics of the Region

Coal mining changes the original geochemical equilibrium of rock bodies and by changing the oxidantion condition of the area; it may cause the release of elements from the coal and ambient rocks into the environment. In the present study, the effects of mining activities in Tazareh Mine Complex, located on 70km North West of Shahrood, were investigated. Concentrations of As, S, Cu, Fe, Hg, Sb, Pb, Zn, Sr and Se in the water resources, tailings and the coals excavated from the main tunnel of the mine were determined to find out the distribution of these elements in the groundwater. The coal in this region shows a high value of enrichment factor for Cu, Pb, As, Hg and Se (22.55, 77.01, 17.86, 44.64, 61.95, and 486.40, respectively). The tailing and face have much less enrichment factor for the above mentioned elements compared and the coal in the region. In terms of correlation among the elements, high correlations between Fe and Pb (0.929) and also Zn and Hg (0.980) were detected. Heavy elements in very low concentrations (3.1 and 2501 ppb for Cu and Sr, respectively and less than the detection limit for Pb, Zn, Fe, As, Sb, Hg and Se) were detected in the mine drainage due to Natural Alkaline Mine Drainage (NAMD) with pH=7.6. Mining, however, caused an elevation in the concentration of S, Sr, Cu, As and Se (430000, 8505, 3.7, 1.5 and 3 ppb, respectively) in the groundwater. S, with a rise of 9.4 times in the downstream groundwater comparing to the upstream groundwater, showed the highest increase.