Aquatic Geochemistry of Dhanbad, Jharkhand: Source Evaluation and Quality Assessment

Surface, subsurface and mine water collected from rural, urban, industrial and coal mining areas of Dhanbad district have been analysed to assess the major ion chemistry, the weathering and geochemical processes controlling the water composition and suitability of water for domestic, industrial and agricultural uses. Ca, Mg, and HCO₃ dominate the chemical composition of the water chemistry. However, in the mine water and water samples collected from mining areas, high concentration of SO₄ has been observed. Water chemistry of the study area strongly reflects the dominance of continental weathering and higher concentration of SO₄, Cl and TDS in some samples indicates mining and anthropogenic impact on water quality. The high contribution of (Ca+Mg) to the total cations, relatively high (Na+K)/TZ⁺ ratio (0.27) and low equivalent ratio of (Ca+Mg)/(Na+K) i.e. 3.6 suggest combined influence of carbonate and silicate weathering. The higher values of C-ratio for most of the surface and subsurface water signify that carbonic acid weathering is the major proton producer in these waters. However, the low C-ratio for the mine water (average 0.22) and the waters collected near the coal mining areas suggests that sulphide oxidation and/or coupled reactions (involving both carbonic acid weathering and sulphide oxidation) control the chemical quality in the mining areas. The quality assessment of surface and subsurface water shows that water is suitable for domestic use with few exceptions. The calculated values of SAR, RSC and sodium percentage indicate that water can be used for irrigation without any hazard.