Abstract

A part of Raniganj coalfield, eastern India, covering an area of about 156 km2 (60 mi2), was studied to identify the impact of mining on geoenvironment, in terms of heavy-metal mobilization. Twenty-eight soil samples were taken from four major landuse classes, viz., mining area, land with or without scrub, agricultural field, and social forestry area, and analyzed for pH, electrical conductivity, organic carbon, and heavy metals (Fe, Mn, Zn, Cu, Ni, Co, Cr, Pb, Cd, and As). Intermediate groundwater flow system of the area was inferred through the fitting of polynomial trend surfaces to the water-table elevation data from 55 observation wells for premonsoon, monsoon, and postmonsoon periods. Quantitative analyses of 17 groundwater samples (7 from mining areas and 10 from nonmining areas) were carried out with special reference to heavy metals (Fe, Mn, Zn, Cu, Ni, Co, Cr, Pb, Cd, and As) during these three periods. Twigs of selected planted species used in reclamation of one of the mine spoils in the area were also analyzed for heavy metals (Fe, Mn, Zn, Cu, Ni, Co, Cr, Pb, Cd, and As). Impacts of mining have been measured in terms of erosion and heavy-metal mobilization from mine spoils to the surrounding geoenvironment. Leaching on mine spoils followed by surface runoff contaminated the soil with heavy metals, whereas leaching followed by percolation contaminated the groundwater with heavy metals. Effects were inferred in terms of changing ecosystem. Native plant species like Shorea robusta, Terminalia tomentosa, etc. are being replaced by smaller species like Butea monosperma, which appears to be more tolerant in this changed ecosystem.

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