2. Assessment of Subsurface Lithology by Resistivity Survey Coupled with Hydrochemical Study to Identify Arsenic Distribution Pattern in Central Gangetic Plain: A Case Study of Bhagalpur District, Bihar, India

The occurrence of arsenic (As)-rich alluvial groundwater is a worldwide problem (Kumar et al. Environ Geochem Health 32:129–146, 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. Int J Water Res Dev 13:79–92, 1997; Ahmed et al. Appl Geochem 19:181–200, 2004; Ben et al. Appl Geochem 18:1417–1434, 2003). Some states as Uttar Pradesh and Bihar reported the presence of elevated concentrations of arsenic in drinking water wells sporadically (Acharyya and Shah, Environ Health Perspect 112:A19–A20, 2004; Chakraborti et al. J Environ Monit 6:74N–83N, 2004; Acharyya, Gondwana Res 8:1–12, 2005; Chauhan et al. Chemosphere 75(1):83–89, 2009; Sankararamakrishnan et al. Sci Total Environ 401:162–167, 2008; Srivastava et al. Initial data on arsenic in groundwater and development of a state action plan, Uttar Pradesh, India. In: Bhattacharya P, Ramanathan AL, Mukherjee AB, Bundschuh J, Chandrasekharam D, Keshari AK (eds) Groundwater for Sustainable Development: Problems, Perspectives and Challenges. Taylor and Francis/A. A, Balkema, 2008; Kumar et al. Environmentalist 31:358–363, 2010). Several authors suggested that the reductive dissolution of Fe (III)-oxyhydroxides in strongly reducing conditions in the young alluvial Holocene sediments is the cause for arsenic mobilization (Harvey et al. Science 298:1602–1606, 2002; Nickson et al. Nature 395:338, 1998; Nickson et al. Appl Geochem 15:403–413, 2000). Groundwater quality is controlled by various factors viz. composition of recharging water, the mineralogy and reactivity of the geological formations in the region of aquifer recharges, the impact of human activities and the environmental parameters that may control the geochemical mobility of redox (oxidation and reduction potential as varies from 169 mV to –134 mV respectively in this case) sensitive elements in the groundwater environment (Bhattacharya et al. Environ Geochem Health 31:23–44, 2009). 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, Environ Health Perspect 112:A19–A20, 2004; Acharyya, Gondwana Res 8:1–12, 2005).