Geophysical approach to delineate arsenic hot spots in the alluvial aquifers of Bhagalpur district, Bihar (India) in the central Gangetic plains

Pankaj Kumar,Ram Avtar,G Senthil Kumar,Alok Kumar,Parijat Tripathi,Chander Kumar Singh,A L Ramanathan

doi:10.1007/s13201-013-0133-y

Pankaj Kumar, Ram Avtar + Show 5 more

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https://doi.org/10.1007/s13201-013-0133-y

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Abstract

A combined study of the geophysical survey and hydro-geochemistry in the Quaternary alluvial aquifers of Bhagalpur district from Bihar state in central Gangetic plain of India was carried out with the objective of identifying the geochemical processes and their relation with lithological profile. Results of resistivity survey validated with borehole lithology gave us a clear picture of the geological signature of the aquifers, which support the reducing nature of the aquifer where concentration of arsenic was high. Reducing nature of the aquifer environment was shown by water samples having relatively negative Eh value. From XRD study of the soil samples, it was found that goethite, dolomite, calcite, quartz and feldspar are the major minerals for most of the samples. Output of this work concludes that resistivity survey is an economically feasible tool which can be successfully used to target arsenic-safe aquifers on wide scale.

Highlights

The occurrence of arsenic (As)-rich alluvial groundwater is a worldwide problem (Kumar et al 2010)
The variation in subsurface lithology of the aquifer can be clearly defined on the basis of vertical electrical sounding (VES)
Combined with the geochemical composition, this study reveals that the controlling factor of arsenic in ground water is redox condition and iron content of the aquifer and release of arsenic may depend on oxidation followed by reduction due to vertical movement of water

Summary

Introduction

The occurrence of arsenic (As)-rich alluvial groundwater is a worldwide problem (Kumar et al 2010). Most studies of As pollution have focused on the predominance of As poisoning in the groundwater of West Bengal (India) and Bangladesh and thought to be limited to the Ganges Delta, i.e., the lower Gangetic plain (Bhattacharya et al 1997; Ahmed et al 2004; Ben et al 2003) Some states such as Uttar Pradesh and Bihar reported the presence of elevated concentrations of arsenic in drinking water wells sporadically (Acharyya and Shah 2004; Chakraborti et al 2004; Acharyya 2005; Chauhan et al 2009; Sankararamakrishnan et al 2008; Srivastava et al 2008; Kumar et al 2010). The arsenic-contaminated aquifers are persistent within lowland organic rich, clayey deltaic sediments in the Bengal Basin and locally within similar facies in narrow, entrenched river valleys within the Gangetic alluvial plain (Acharyya and Shah 2004; Acharyya 2005)

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