Geochemical contamination in the mine affected soil of Raniganj Coalfield – A river basin scale assessment

The study aimed to assess the heavy metals (K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, As, Pb, Sr, Zr) contamination in the soil of mine affected Singaran river basin and to analyse spatial variation in the contamination level considering 32 soil samples. Elemental analysis of soil samples has been performed through Energy Dispersive X-ray Analysis (EDX) to quantify the elemental concentration (mg kg−1). Heavy metal concentrations have been assessed through geo-accumulation index (Igeo) and enrichment factor (EF). Indices showed soils have moderate accumulation of most of the metals with moderate enrichment of Sr, Zr, Zn, Cu and Ni. Soil contamination level assessment has been carried out using indices like Contamination Factor (CF), degree of contamination (Cdeg), modified degree of contamination (mCdeg) and Pollution Load Index (PLI). CF shows moderate to considerable contamination by Sr, Zr, Ca, Cu, Mn, Zn and Ni. Mean indices values (mCdeg and PLI for the entire basin are 3.38 and 2.23 respectively) show low to moderate level of soil contamination. These indices result have been mapped and analysed in GIS platform to get spatial variation of pollution level. Opencast mines dominate middle catchment area and so is comparatively contaminated. Sample sites 11, 18 and 25 evidenced high values of all indices of pollution load. From the ecological standpoint Ecological Risk Factor (Er) and Potential Ecological Risk Index (RI) have been estimated to assess regional threat to native soil environment and it shows low ecological risk potential. Analysis shows that mine dominated soil of the entire Singaran basin is less contaminated in all respect but tends to the moderate contamination level at the mid-catchment area, especially by Sr, Zr, Zn, Cu and Ni.