Impact of acid mine drainage and hydrogeochemical studies in a part of Rajrappa coal mining area of Ramgarh District, Jharkhand State of India

Abstract

Groundwater quality studies of coal mining areas are very important due to coal explorations, dumping of huge quantity of over burdens, and subsequently mixing with the coal mine drainage areas. The main objective of this study was to evaluate the possible influence of acid mine drainage (AMD), in the groundwater in terms of major ions, trace elements and identifying the hydrogeochemical characteristics, in the Rajrappa coal mining area in the central part of India. The results show that groundwater is generally neutral to alkaline in nature. The major ions and trace elements concentrations in the groundwater samples were found to be below the permissible limits based on WHO guidelines and suitable for the drinking water purposes. Few wells show a higher order in certain parameters due to impact local geologic strata. The piper diagram shows two major hydrochemical water types represents, such as Ca-Mg-Cl, and Ca-Mg-HCO3 types. Based on major ion concentrations and its minor variations are indicative of the stable geochemical and hydrologic environments, which controls the groundwater chemistry in the coal mining area. Geochemical evolution of the groundwater chemistry mainly controls by the natural geochemical processes such as mineral dissolution, rock-water interactions and mineral precipitation processes. Saturation index studies show that, groundwater samples were near saturation to equilibrium conditions with the carbonate phase minerals of calcite and dolomite and undersaturated with gypsum and anhydrite. Secondary minerals of Fe and Mn – sulphate and carbonate phase species are in undersaturated conditions. The shorter residence times of groundwater in the wells, lack of acid mine drainage generating conditions and the impact of dilution during high base flows are diluting the coal mining drainage streams and making a negligible impact of acid mine drainage.