• Soma Giri

      Articles written in Journal of Earth System Science

    • Metal contamination of agricultural soils in the copper mining areas of Singhbhum shear zone in India

      Soma Giri Abhay Kumar Singh Mukesh Kumar Mahato

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      The study was intended to investigate the heavy metal contamination in the agricultural soils of the copper mining areas in Singhbhum shear zone, India. The total concentrations of the metals were determined by inductively coupled plasma-mass spectrometer (ICPMS). Pollution levels were assessed by calculating enrichment factor (EF), geo-accumulation index (Igeo), contamination factors (CF), pollution load index (PLI), Nemerow index and ecological risk index (RI). The metal concentrations in the soil samples exceeded the average shale values for almost all the metals. Principal component analysis resulted in extraction of three factors explaining 82.6% of the data variability and indicated anthropogenic contribution of Cu, Ni, Co, Cr, Mn and Pb. The EF and Igeo values indicated very high contamination with respect to Cu followed by As and Zn in the agricultural soils. The values of PLI, RI and Nemerow index, which considered the overall effect of all the studied metals on the soils, revealed that 50% of the locations were highly polluted with respect to metals. The pollution levels varied with the proximity to the copper mining and processing units. Consequently, the results advocate the necessity of periodic monitoring of the agricultural soils of the area and development of proper management strategies to reduce the metal pollution.

    • Fluvial geochemistry of Subarnarekha River basin, India

      Abhay Kumar Singh Soma Giri Aaditya Chaturvedi

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      The fluvial geochemistry of the Subarnarekha River and its major tributaries has been studied on a seasonal basis in order to assess the geochemical processes that explain the water composition and estimate solute fluxes. The analytical results show the mildly acidic to alkaline nature of the Subarnarekha River water and the dominance of Ca$^{2+}$ and Na$^{+}$ in cationic and HCO$_{3}^{-}$ and Cl$^{-}$ in anionic composition. Minimum ionic concentration during the monsoon and maximum concentration in the pre-monsoon seasons reflect concentrating effects due to decrease in the river discharge and increase in the base flow contribution during the pre-monsoon and dilution effects of atmospheric precipitation in the monsoon season. The solute acquisition processes are mainly controlled by weathering of rocks, with minor contribution from marine and anthropogenic sources. Higher contribution of alkaline earth (Ca$^{2+} + $Mg$^{2+}$) to the total cations (TZ$^{+}$) and high (Na$^{+}+$K$^{+}$)/Cl$^{-}$, (Na$^{+}+$K$^{+}$)/TZ$^{+}$, HCO$_{3}^{-}$/(SO$_{4}^{2-}+$Cl$^{-}$) and low (Ca$^{2+}+$Mg$^{2+}$)/(Na$^{+}+$K$^{+}$) equivalent ratios suggest that the Subarnarekha River water is under the combined influence of carbonate and silicate weathering. The river water is undersaturated with respect to dolomite and calcite during the post-monsoon and monsoon seasons and oversaturated in the pre-monsoon season. The pH–log H$_{4}$SiO$_{4}$ stability diagram demonstrates that the water chemistry is in equilibrium with the kaolinite. The Subarnarekha River annually delivered 1.477$\times 10^{6}$ ton of dissolved loads to the Bay of Bengal, with an estimated chemical denudation rate of 77 ton km$^{-2}$ yr$^{-1}$. Sodium adsorption ratio, residual sodium carbonate and per cent sodium values placed the studied river water in the ‘excellent to good quality’ category and it can be safely used for irrigation.

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