Safe and Sustainable Use of Arsenic-Contaminated Aquifers in the Gangetic Plain

For a long time it was understood that the extent of the arsenic (As) enriched groundwater is confined within the lower Ganges plain and delta in eastern India. However, during the last few years, reports of elevated As in groundwater of different parts of the middle portions of the Gangetic plain, upstream from West Bengal, in U.P. (Ramanathan et al. Geol Soc Am Program Abstr 38(7):241, 2006) and Bihar, got published. Subsequently, As contamination was detected in foothills of Himalayas in Nepal (Shrestha et al. J Environ Sci Health Part A 38(1):185-200, 2003), which is a sediment provenance for many of the tributaries of the Ganges, and also in the Indus alluvial plains in Punjab and Sindh provinces of Pakistan (Nickson et al. Appl Geochem 20(1):55–68, 2005). In spite of some surveys on As distribution, there is a lack of hydrogeochemical knowledge about the distribution, extent, severity, source and cause of the contamination in these areas. However, initial estimates show that the poisoning might be widespread and several million people may be at risk.

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).

Pollution of groundwater by naturally occurring arsenic (As) is found in sedimentary aquifers worldwide and health problems associated with groundwater As have been documented in many parts of the world such as Bangladesh, India, Pakistan, Nepal, China, Hungary, Vietnam, Thailand, Cambodia, Taiwan, Inner Mongolia, Ghana, Egypt, Japan, Argentina, Mexico, USA and Chile (Mandal BK, Suzuki KT, Talanta 58:201–235, 2002; Mukherjee A, Sengupta MK, Hossain MA, Ahmed S, Das B, Nayak B, Lodh D, Rahman MM, Chakraborti D, J Health Popul Nutr 24:142–163, 2006; Ravenscroft P, Brammer H, Richards K, Arsenic pollution: a global synthesis. Wiley Blackwell, Chichester, 2009). Long-term intake of As-contaminated groundwater above 50 μg/L has caused skin diseases (pigmentation, dermal hyperkeratosis, skin cancer), cardiovascular, neurological, hematological, renal and respiratory diseases, as well as lung, bladder, liver, kidney and prostate cancers (Smith AH, Hopenhayn-Rich C, Bates MN, Goeden HM, Hertz-Picciotto I, Duggan HM, Wood R, Kosnett MJ, Smith MT, Environ Health Perspect 97:259–267, 1992, Smith AH, Goycolea M, Haque R, Biggs ML, Am J Epidemiol 147:660–669, 1998). The mode of occurrence, origin and mobility of As in sedimentary aquifers are influenced by local geology, geomorphology, hydrogeology and geochemistry of sediments (Bhattacharya P, Chatterjee D, Jacks G, Water Resour Dev 3:79–92, 1997; Nickson R, McArthur JM, Burgess W, Ahmed KM, Ravenscroft P, Rahman M, Nature 395:338, 1998; Acharyya SK, Lahiri S, Raymahashay BC, Bhowmik A, Environ Geol 39:1127–1137, 2000; Kinniburgh DG, Smedley PL, Arsenic contamination of groundwater in Bangladesh, Report, WC/00/19. British Geological Survey, Dhaka, 2001). The upper permissible limit of As in drinking water is 10 µg/L as per WHO guideline (WHO, Guideline for drinking water quality. Recommendations. Geneva, 1993), which has been endorsed by Bureau of Indian Standards (Indian standard: drinking water. Specification (first revision), Amendment no. 2, New Delhi, 2003). India is the second most populated country in the world, where a large percentage of world’s population (17.5 %) is living on limited land area (2.4 %). The Gangetic plain is one of the vast Quaternary alluvium track in Asia, and many cities, towns, villages, and hamlets are located on the bank of the Ganga and Ghaghara rivers. The Ghaghara river has originated from Matsatung glacier in the Himalayas and travelled a distance of about 1,080 km in NW–SE direction, to join the Ganga River. The topography of the Gangetic plains are heterogeneous, varying between upland surfaces, plain areas and low lying small natural bodies, viz., swamp and ponds. Recently, groundwater As contamination has been reported in the states of Uttar Pradesh (UP), Bihar and Jharkhand (Chakraborti D, Mukherjee SC, Pati S, Sengupta MK, Rahman MM, Chowdhury UK, Lodh D, Chanda CR, Chakraborty AK, Environ Health Perspect 111:1194–1200, 2003; Acharyya SK, Shah BA, Environ Health Perspect 112:A19–A20, 2004; Bhattacharjee S, Chakravarty S, Maity S, Dureja V, Gupta KK Chemosphere 58:1203–1217, 2005; Ahamed S, Sengupta MK, Mukherjee A, Hossain A, Das B, Nayak B, Pal A, Mukherjee SC, Pati S, Dutta RN, Chatterjee G, Mukherjee A, Srivastava R, Chakraborti D, Sci Total Environ 370:310-322, 2006; Shah BA, Environ Geol 53:1553–1561, 2008). In this study, a survey on arsenic content in groundwater was carried out in Mirzapur, Varanasi, Ghazipur, Ballia, Buxar, Bhojpur, Patna, Vaishali, Faizabad, Gonda and Basti districts of UP and Bihar in the Gangetic plain (Fig. 3.1).

Arsenic (As) rich groundwater in alluvial aquifers is a worldwide problem (Nriagu JO, Bhattacharya P, Mukherjee AB, Bundschuh J, Zevenhoven R, Loeppert RH, Arsenic in soil and groundwater: an introduction. In: Bhattacharya P, Mukherjee AB, Bundschuh J, Zevenhoven R, Loeppert RH (eds) Arsenic in soil and groundwater environment: biogeochemical interactions, health effects and remediation. Trace metals and other contaminants in the environment, vol 9 (Ser Ed Nriagu JO). Elsevier, Amsterdam, 2007). Elevated arsenic concentrations have long been detected in Southeast Asia (e.g. Thailand, Myanmar, Vietnam, Cambodia and Lao), India, Bangladesh, China, Mongolia, Nepal and Pakistan (Smedley PL, Kinniburgh DG, Appl Geochem 17:517–568, 2002). Recent reports of discovery of arsenic (As) enrichment in groundwater of the Brahmaputra river basin (Bhattacharya P, Mukherjee A, Mukherjee AB, Arsenic contaminated groundwater of India. In: Nriagu J (ed) Encyclopedia of environmental health. Elsevier B.V, Amsterdam, 2011) has exposed a significantly large population inhabiting in the river valley to serious health threats, although the actual distribution and extent of the As affected groundwater in the aquifers are yet to be established. Because of its vicinity to the highly As rich groundwater regions of Bengal basin (Bangladesh and West Bengal state of India), the extent of the polluted areas within the Brahmaputra basin may be much wider than what is initially understood. Groundwater arsenic contamination in the Brahmaputra basin aquifers in Assam, a state in the northeastern part of India, has started gaining attention relatively recently. Singh (Arsenic contamination in groundwater of North Eastern India. In: Proceedings of 11th national symposium on hydrology with focal theme on water quality. National Institute of Hydrology, Roorkee, 2004) reported maximum groundwater arsenic concentrations in Jorhat district (Fig. 4.1), located in the southern bank of the Brahmaputra river in Assam (maximum groundwater As concentration ranges between 194 and 657 μg/L), with relatively lower concentrations in the northern bank like Lakhimpur district (50–550 μg/L). Based on studies conducted in Darrang and Bongaigaon districts located in the northern bank (Fig. 4.1) of the Brahmaputra river in Assam, Enmark and Nordborg (Arsenic in the groundwater of the Brahmaputra floodplains, Assam, India—Source, distribution and release, mechanisms. Retrieved from the url: www2.​lwr.​kth.​se/​Publikationer/​PDF_​Files/​MFS_​2007_​131.​pdf, 2007) reported the concentration of arsenic in the two districts between 5 and 606 μg/L. In a study conducted in 2010 (Mahanta C, Pathak N, Bhattacharya P, Enmark G, Nordborg D, Source, distribution and release mechanisms of arsenic in the groundwater of Assam floodplains of Northeast India. In: Proceedings of the World Environmental and Water Resources Congress sponsored by Environmental and Water Resources Institute (EWRI) of the American Society of Civil Engineers, 2008), concentrations beyond 50 μg/L have been confirmed in 72 blocks out of 214 blocks in 22 districts of Assam. A study by Chetia M, Chatterjee S, Banerjee S, Nath MJ, Singh D, Srivastava RB, Sarma HP (Environ Monit Assess 173:1393–1398, 2011) in the Golaghat district reported As concentration ranging between 1 and 128 μg/L in six blocks of the district. These studies so far have remained spatially limited and a comprehensive picture is yet to emerge. To comprehensively evaluate the extent of As contamination in the region, a blanket rapid assessment study was undertaken in large parts of the Brahmaputra basin in Assam. This paper reports the preliminary assessment of arsenic distribution in the Brahmaputra basin in Assam based upon results from 56,180 public groundwater wells, tested during the rapid assessment programme.

The problem of naturally occurring As pollution in groundwater is a burning issue which has now been recognised as one of the greatest environmental hazards, threatening the lives of the millions across the globe (Nickson R, McArthur JM, Burgess W, Ahmed KM, Ravenscroft P, Rahman M, Nature 395:338, 1998, Nickson RT, McArthur JM, Ravenscroft P, Burgess WG, Ahmed KM, Appl Geochem 15(4):403–413, 2000; Smith AH, Lingas EO, Rahman M, Bull World Health Organ 78(9):1093–1103, 2000; Berg M, Tran HC, Nguyen TC, Pham HV, Schertenlrib R, Giger W (2001), Environ Sci Technol 35:2621–2626, 2001; Anawar HM, Akai J, Mostofa KMG, Safiullah S, Tareq SM, Environ Int 27:597-604, 2002; Smedley PL, Kinniburgh DG, Appl Geochem 17(5):517–568, 2002; Guo HM, Wang YX, Shpeizer GM, Yan SL, J Toxicol Environ Health Part A, Environ Sci Eng Toxic Hazard Subst Control 38:2565–2580, 2003; Ravenscroft P, Burgess GW, Ahmed KM, Burren M, Perrin J, Hydrogeol J 13:727–751, 2003; Smedley PL, Zhang M, Zhang G, Luo Z, Appl Geochem 18(9):1453–1477, 2003; Li J, Wang Z, Cheng X, Wang S, Jia Q, Han L et al, Chin J Endem 24:183–185, 2005; Polya DA, Gault AG, Diebe N, Feldman P, Rosenboom JW, Gilligan E et al, Mineral Mag 69:807–823, 2005; Anawar HM, Akai J, Yoshioka T, Konohira E, Lee JY, Fukuhara H, Tari Kul Alam M, Garcia Sanchez A, Environ Geochem Health 28:553–565, 2006; Enmark G, Nordborg D, Arsenic in the groundwater of the Brahmaputra floodplains, Assam, India – Source, distribution and release mechanisms. Committee of Tropical Ecology ISSN 1653–5634 minor field study 131. Uppsala University, Sweden, 2001; Nriagu et al. Arsenic in soil and groundwater: an introduction. In: Bhattacharya P, Mukherjee AB, Bundschuh J, Zevenhoven R, Loeppert RH (eds), Arsenic in soil and groundwater environment: biogeochemical interactions, health effects and remediation, trace metals and other contaminants in the environment, vol 9, (Ser ed Nriagu JO). Elsevier, Amsterdam, 2007; Kumar M, Kumar P, Ramanathan AL, Bhattacharya P, Thunvik R, Singh UK, Tsujimura M, Sracek O, J Geochem Explor 105:83–94, 2010a, Kumar P, Kumar M, Ramanathan AL, Tsujimura M, Environ Geochem Health 32:129–146, 2010b; Bundschuh J, Litter MI, Parvez F, Román-Ross G, Nicolli Hugo B, Jean J-S, Liu C-W, María Dina L, Armienta A, Guilherme Luiz RG, Cuevas AG, Cornejo L, Cumbal L, Toujaguez R, One century of arsenic exposure in Latin America: a review of history and occurrence from 14 countries, 429:2–35, 2012). Long-term ingestion of drinking water having As concentration beyond the permissible limit of 50 μg/L leads to detrimental effects on human health. Epidemiological studies have shown that inorganic As is a serious toxicant and can cause a variety of adverse health effects, such as dermal changes, respiratory, pulmonary, cardiovascular, gastrointestinal, haematological, hepatic, renal, neurological, developmental, reproductive, immunologic lead to cancer and other degenerative effects of the circulatory and nervous system (Golub MS, Macintosh MS, Baumrind N, J Toxicol Environ Health Part B 1(3):199-241, 1998; Lin T-H, Huang Y-L, Wang M-Y, J Toxicol Environ Health 53:85–93, 1998; NRC 2001; Ahamed S, Kumar Sengupta M, Mukherjee A, Amir HM, Das B, Nayak B, Pal A, Mukherjee CS, Pati S, Nath DR, Chatterjee G, Mukherjee A, Srivastava R, Chakraborti D, Sci Total Environ 370(2–3):310–322, 2006). In view of the above perspective WHO in 1993 has lowered its earlier permissible limit of 50 μg/L in drinking water to 10 μg/L. The BIS has also endorsed 10 μg/L as the permissible limit for As in drinking water.

Arsenic (As) contamination of groundwater is a major environmental and public health issue in the Ganga-Brahmaputra-Meghna (GBM) plains, including almost all states in the Ganga basin, large areas of Bangladesh (GBM basin), and some districts of Assam (Brahmaputra and Meghna sub-basins of the GBM basin) in North East India (Chowdhury UK, Biswas BK, Chowdhury TR, Samanta G, Mandal BK, Basu GC, Chanda CR, Lodh D, Saha KC, Mukherjee SK, Roy S, Kabir S, Quamruzzaman Q, Chakraborti D, Environ Health Perspect 108(5):393–397, 2000; Chakraborti D, Mukherjee SC, Pati S, Sengupta MK, Rahman MM, Chowdhury UK, Lodh D, Chanda CR, Chakraborti AK, Basu GK, Environ Health Perspect 111(9):1194–1201, 2003; Singh AK, Arsenic contamination in groundwater of North Eastern India. In: Proceedings of national seminar on hydrology, National Institute of Hydrology, Roorkee, India. http://​users.​physics.​harvard.​edu/​~wilson/​arsenic/​references/​singh.​pdf. Accessed 25 June 2013, 2004; Ahamed S, Sengupta MK, Mukherjee A, Hossain MA, Das B, Nayak B, Pal A, Mukherjee SC, Pati S, Dutta RN, Chatterjee G, Mukherjee A, Srivastava R, Chakraborty D, Sci Total Environ 370:310–322, 2006; Nickson R, Sengupta C, Mitra P, Dave SN, Banerjee AK, Bhattacharya A, Basu S, Kakoti N, Moorthy NS, Wasuja M, Kumar M, Mishra DS, Ghosh A, Vaish DP, Srivastava AK, Tripathi RM, Singh SN, Prasad R, Bhattacharya R, Deverill P, J Environ Sci Health A 42:1707–1718, 2007). Further, the detection of As in the groundwater of several districts of Manipur, which are part of the Chindwin-Irrawaddy basin (Chakraborti D, Singh EJK, Das B, Shah BA, Hossain MA, Nayak B, Ahamed S, Singh NR, Environ Geol 56:381–390, 2008; Oinam JD, Ramanathan AL, Linda A, Singh G, Environ Earth Sci 62:1183–1195, 2011, Oinam JD, Ramanathan AL, Singh G, J Asian Earth Sci 48:136–149, 2012; Singh EJK, Gupta A, Singh RM, Environ Sci Pollut Res 20(4):2421–2434, 2013), suggests possible As contamination of groundwater in the river valleys of Myanmar as well. Arsenic in the groundwater of this area is derived from the microbial reductive dissolution of iron (Fe) oxyhydroxide and subsequent release of the sorbed As (Nickson RT, McArthur JM, Ravenscroft P, Burgess WG, Ahmed KM, Appl Geochem 15:403–413, 2000; Winkel L, Berg M, Amini M, Hug SJ, Johnson CA, Nat Geosci 1:536–542, 2008). The presence of arsenic in this region is, therefore, a natural phenomenon that warrants realistic assessment of the risks involved followed by proper, often locale-specific management in order to reduce public misery while achieving safe and sustainable utilization of surface- as well as ground-water resources. The problem of arsenic contamination of groundwater in the lower Ganga basin state of West Bengal and in Bangladesh has been amply highlighted (Nickson R, McArthur J, Burgess W, Ahmed KM, Ravenscroft P, Rahmann M, Nature 395:338, 1998, Nickson RT, McArthur JM, Ravenscroft P, Burgess WG, Ahmed KM, Appl Geochem 15:403–413, 2000; Chowdhury UK, Biswas BK, Chowdhury TR, Samanta G, Mandal BK, Basu GC, Chanda CR, Lodh D, Saha KC, Mukherjee SK, Roy S, Kabir S, Quamruzzaman Q, Chakraborti D, Environ Health Perspect 108(5):393–397, 2000; Smith AH, Lingas EO, Rahman M, Bull World Health Organ 78:1093–1103, 2000; Rahman MM, Chowdhury UK, Mukherjee SC, Mondal BK, Paul K, Lodh D, Biswas BK, Chanda CR, Basu GK, Saha KC, Roy S, Das R, Palit SK, Quamruzzaman Q, Chakraborti D, Clin Toxicol 39(7):683–700, 2001; Fazal MA, Kawachi T, Ichion E, Water Int 26(3):370–379, 2001; Chakraborti D, Das B, Rahman MM, Chowdhury UK, Biswas B, Goswami AB, Nayak B, Pal A, Sengupta MK, Ahamed S, Hossain A, Basu G, Roychowdhury T, Das D, Mol Nutr Food Res 53:542–551, 2009) since long, while that in the middle Ganga plain is relatively less widely known, although the situation may be no less alarming in this region as well.

About one-third of the earth’s land surface is facing challenge of water scarcity in both quantitative and qualitative terms (Postel SL, Last oasis: facing water scarcity, 2nd edn. W.W. Norton, New York, 1997). In the last few decades, the global finding of the presence of elevated concentrations of various toxic solutes from natural and anthropogenic sources has limited the available volume of safe drinking water. Understanding the aquifer hydraulic properties and hydrochemical characteristics of water is crucial for proper planning, management and sustainable utilization of groundwater. Generally, the motion of groundwater along its flow paths below the ground surface increases the concentration of the chemical species; hence the groundwater chemistry could reveal important information on the geological history of the aquifers and the suitability of groundwater for domestic, industrial and agricultural purposes (Kortatsi BK, Aquat Geochem 13(1):41–74, 2007).

Tectonic evolution of Himalayas is related to high erosional potential and substantial sediment transport. Fluvial deposition of clastic material in the Middle Gangetic plain (MGP) is mainly governed by crustal deformation and climatic condition of Himalayas (Singh M, Singh IB, Müller G, Geomorphology 86:144–175, 2007). Seven large Asian rivers—Ganga, Indus, Brahmaputra, Yangtze, Huang He or Yellow River, Salween and Mekong—are fed by Himalayan glaciers which are supplying ~30 % of the global sediments to the ocean (Milliman JD, Meade RH, J Geol 9:1–19, 1983; Singh VB, Ramanathan AL, Pottakkal JG, Kumar M, J Asian Earth Sci 79:224–234, 2014, 2005). High flux of sediment transported from different terrain of Himalayas is product of geologically young rock formation (Singh VB, Ramanathan AL, Pottakkal JG, Kumar M, J Asian Earth Sci 79:224–234, 2014). It provides an opportunity to study the fluvial system and post-depositional changes in sediment water interaction depending on the degree of mobility of element under the altered environmental conditions. Arsenic (As) contamination of groundwater is a global problem. Understanding of As mobilization from sediments to As-contaminated aquifers is important for water quality management in areas of MGP of India.

The presence of high concentrations of arsenic (As) in groundwater is a worldwide well known environmental problem in recent years (Nriagu et al. Arsenic in soil and groundwater: an introduction. In: Bhattacharya P, Mukherjee AB, Bundschuh J, Zevenhoven R, Loeppert RH (eds), Arsenic in soil and groundwater environment: biogeochemical interactions, health effects and remediation, trace metals and other contaminants in the environment, vol 9, (Ser ed Nriagu JO). Elsevier, Amsterdam, 2007). Most estimates 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 (the lower Ganga plain) (Bhattacharya et al. Int J Water Res Dev 13:79–92, 1997; Bhattacharya et al. Arsenic in the environment: a global perspective. In: Sarkar B (ed) Handbook of heavy metals in the environment. Marcell Dekker, New York, 2002a; Ahmed et al. Appl Geochem 19(2):181–200, 2004; Ben et al. Appl Geochem 18:1417–1434, 2003). High As in the groundwater of the Lower Gangetic plain of Bangladesh and West Bengal was reported by Bhattacharya et al. (Int J Water Res Dev 13:79–92, 1997). Several authors suggested that the reductive dissolution of Fe (III)-oxyhydroxides in strongly reducing conditions of the young alluvial sediments is the cause for groundwater As mobilization (Ahmed et al. Appl Geochem 19(2):181–200, 2004; Bhattacharya et al. Int J Water Res Dev 13:79–92, 1997; Bhattacharya et al. Bull Environ Contam Toxicol 69:538–545, 2002b; Harvey et al. Science 298:1602-1606, 2002; McArthur et al. Water Resour Res 37:109–117, 2001; Nickson et al. Nature 395:338–349, 1998; Nickson et al. Appl Geochem 15:403–413, 2000). The reduction is driven by microbial degradation of sedimentary organic matter, which is a redox-dependent process consuming dissolved O₂ and NO₃ ⁻ (Stumm and Morgan. Aquatic chemistry: an introduction emphasizing chemical equilibria in natural waters. Wiley, New York, 1981; Bhattacharya et al. Int J Water Res Dev 13:79–92, 1997; Bhattacharya et al. Arsenic in the environment: a global perspective. In: Sarkar B (ed) Handbook of heavy metals in the environment. Marcell Dekker, New York, 2002a; Bhattacharya et al. Bull Environ Contam Toxicol 69:538–545, 2002b; Nickson et al. Appl Geochem 15:403–413, 2000). Overall, the quality of groundwater depends on the composition of recharging water, the mineralogy and reactivity of the geological formations in aquifers, the impact of human activities and the environmental parameters that may control the geochemical mobility of redox sensitive elements in the groundwater environment (Kumar et al. Environ Geol 50:1025–1039, 2006, 2007; Bhattacharya et al. Environ Geochem Health 31:23–44, 2009; Hasan et al. Environ Geol 57:499–511, 2009).

Groundwater is the primary source of water for domestic, agricultural and industrial uses in many countries. Water resources of good quality are becoming an important issue being vital to health, safety and socio-economic development of man. The rising demands for hygienic water often cannot be met by surface water supplies. This has led to increased dependence on groundwater resources in many parts of the world. Hence suitable quantity and quality of groundwater become a more crucial alternative resource to meet the drastic increase in social and agricultural development and to avoid the expected deterioration of groundwater quality due to heavy abstraction for miscellaneous uses. Water quality and its management have received added attention in developing countries. Further intensive use for irrigation makes groundwater a critical resource for human activities. Thus water remains the principal driver for development in South Asia.

Naturally occurring, carcinogenic, arsenic (As) is omnipresent in hydrological systems, and is considered as the most serious abiotic contaminant of groundwater in several parts of the world (Smedley and Kinniburgh, Appl Geochem 17:517–56, 2002; Chatterjee et al., Environ Geol 49:188–206, 2005; Charlet et al., Appl Geochem 22:1273–1292, 2007; Mukherjee et al., J Contam Hydrol 99:1–7, 2008a; Neumann et al., Nat Geosci 3:46–52, 2010 and references therein). Holocene aquifers of south-east Asia (mostly shallow, <50 m) often contain high As groundwater. The groundwater is predominantly used for irrigation and domestic purposes, e.g., cooking, drinking and bathing (Bhattacharya et al., J Water Resour Dev 13:79–92, 1997; Bhattacharyya et al., Mol Cell Biochem 253:347–355, 2003a; Charlet et al., Appl Geochem 22:1273–1292, 2007). In south-east Asia, As-rich groundwaters are often found in alluvial plains of regional rivers (Fendorf et al., Science 328:1123–1127, 2010). Prolonged consumption of groundwater with elevated levels of As may cause a formidable threat to human health and millions of people are now at risk (Bhattacharyya et al. Mol Cell Biochem 253:347–355, 2003a; Chatterjee et al., Water Res 44:5803–5812, 2010; Nath et al., Water Air Soil Pollut 190:95–113, 2008a). Arsenic contamination in groundwater and related health issues is considered as the greatest mass poisoning in human history (Smith et al., Bull World Health Organ 78:1093–1103, 2000).

An access to safe drinking water is primary human need, but at many places around the globe this primary requirement is not fulfilled and millions of people are forced to drink contaminated water. On a larger scale, various elements such as As, F, V, U, Pb, Hg etc. are contaminating the available drinking water resources (WHO, Guidelines for drinking-water quality, Recommendations. World Health Organization, Geneva, 2006). Among all the above mentioned elements, As is posing a major threat and several countries around the globe are facing problem of As contamination in the groundwater. The problem of As contamination is most severe in the South-East Asian countries (Bhattacharya et al. Int J Water Resour Dev 13:79–92, 1997; Chandrasekharam et al. Proc Water Rock Interact 12:1051–1054, 2001; McArthur et al. Appl Geochem 19:1255–1293, 2004; Nickson et al. Nature 395:338, 1998; Smedley and Kinniburgh, Appl Geochem 17:517–568, 2002; van Geen et al. Appl Geochem 23:3244–3251, 2008). Elevated As concentrations have been reported at places in Nepal, India, Bangladesh, Myanmar, Cambodia, Vietnam and Thailand etc. It is estimated that about 200 million people living in Asia are exposed to various health risks due to consumption of As contaminated water (Sun, Toxicol Appl Pharmacol 198:268–271, 2004). In Bengal delta plain alone more than 50 million people are routinely exposed, thus it is described as the worst case of mass-poisoning in the history of mankind (Ahsan et al. Bull Environ Contam Toxicol 82:11–15, 2009; Chakraborti et al. Environ Health Perspect 111:1194–1201, 2003). The WHO (Guidelines for drinking-water quality, 4th edn. World Health Organization, Geneva, 2011) permissible limit of As in drinking water is 10 μg/L, while the Indian permissible limit is five times higher (50 μg/L). In Bengal delta plain As concentrations more than 1,000 μg/L has been reported at several places. Still it appears that the extent of the contamination is not fully known and many new affected areas are getting discovered on regular basis. Apart from West Bengal, higher As concentrations have been reported from other Indian states including Bihar, Uttar Pradesh, Assam, Jharkhand, Chattisgarh and Madhya Pradesh (Acharyya et al. Environ Geol 49:148–158, 2005; Ahamed et al. Sci Total Environ 370:310–322, 2006; Bhattacharjee et al. Chemosphere 58:1203–1217, 2005; Chakraborti et al. India Curr Sci 77:502–504, 1999, Environ Health Perspect 111:1194–1201, 2003; Das et al. Environ Geochem Health 18:5–15, 1996; Paul and Kar, Environ Ecol 22:588–589, 2004).

Arsenic contaminated groundwater causes danger to the health of millions of people in India. In this context, a comparative study has been made to evaluate the Arsenic (As) concentration in groundwater of Gangetic alluvium, West Bengal and south eastern coastal aquifer at Kalpakkam, India. The variations of Ar concentration with lithologies, depth of aquifers, sources and distribution of Ar and hydrochemical facies of groundwater has been clearly identified from the two localities. In Gangetic alluvium, As concentrations appear to be mostly low in groundwater from deep aquifers and it is interesting to note that in almost all the formations of coastal aquifer, the concentration increases with increase of depth. The shallow ground water of the southern coastal aquifer reveals the presence of oxidizing conditions and frequently flushing during the monsoonal period, which may also dilute or reduce the concentrations. The poor relationship between As and Fe indicates the As release into the groundwater depends on several processes such as mineral weathering, O2 consumption, and NO3 reduction and is de-coupled from Fe cycling.

Arsenic contamination of groundwater has been detected in more than 70 countries and has become a major public health concern worldwide (Bundschuh et al. Environ Geochem Health 32:307–315, 2010). Arsenic contamination in groundwater of Southeast Asian regions received significant interest in recent years. In this region, countries affected with As in groundwater include Bangladesh, several states of India, Nepal, Myanmar, Pakistan, Vietnam, Lao People’s Democratic Republic, Cambodia, several provinces of China (Inner Mongolia, Shanxi, Xinjiang, Ningxia, Jilin, Shandong, Qinghai, Sichuan, Anhui, Heilongjiang, Henan, Gansu, Jiangsu, Yunnan and Hunan) and lowlands of Sumatra in Indonesia (Rahman et al. Environ Geochem Health 31:9–21, 2009; Yu et al. Environ Health Perspect 115:636–642, 2007).

With increasing detection of arsenic contaminated aquifers upstream of the Bengal delta plain in last decade, groundwater contamination by arsenic is being perceived as the most severe health hazard over entire Gangetic Plain. The issue of mass arsenic poisoning was initially linked to direct consumption of arsenic contaminated groundwater through hand pumps, but the growing realization that such aquifers are also being increasingly tapped for obtaining irrigation water fuelled fears of arsenic ingestion by the affected population both directly through drinking water sources and indirectly through the water-soil-crop route in this highly fertile region.

It is predicted that around 100 million people living in the Ganga-Meghna- Brahmaputra plain are at the risk of serious arsenic toxicity through exposure of contaminated groundwater (Chakraborti D et al., Groundwater arsenic contamination in Ganga-Meghna-Brahmaputra plain, its health effects and an approach for mitigation. In: UNESCO UCI groundwater conference proceedings. http://​www.​groundwater-conference.​uci.​edu/​proceedings.​html#chapter1, 2008). Groundwater arsenic contamination in the Gangetic Bengal has been termed as the largest mass poisoning in the history of human kind (Smith et al., Bull WHO 78(9):1093–1103, 2000). Arsenic pollution has spread in fourteen out of total nineteen districts of Gangetic Bengal (Chakraborti et al., Mol Nutr Food Res 53(5):542–551, 2009). Application of arsenic-contaminated groundwater for irrigation in Gangetic Bengal has shown to influence accumulation of arsenic in rice, the major staple food in West Bengal (Meharg, Trends Plant Sci 9:415–417, 2004, 2009; Signes-Pastor et al., J Agric Food Chem 56(20):9469–9474, 2008; Bhattacharya et al., Paddy Water Environ 8(1):63–70, 2010a; Samal et al., J Environ Sci Health Part A: Environ Sci Eng 46:1259–1265, 2011; Banerjee et al., Sci Rep 3, Article number: 2195, 2013; Santra et al., Procedia Environ Sci 18:2–13, 2013). Rice is an efficient accumulator of arsenic than any other cereal crops (Su et al. Plant Soil 328:27–34, 2010) and consumption of rice has been termed as an important source of inorganic arsenic intake to human body (Meharg et al., Environ Sci Technol 43(5):1612–1617, 2009).

The presence of arsenic in ground water has been reported from many parts of the world, particularly in the Bengal delta of India and Bangladesh (Berg et al. Environ Sci Tech 35(13):2621–2626, 2001; Rahaman et al. Environ Geochem Health 35(1):119–132, 2013), China (Kinniburgh and Smedley, Arsenic contamination in ground water of Bangladesh. Final Report Summary, Bangladesh Department of Public Health Engineering, British Geological Society, Keyworth. http://​www.​bgs.​ac.​uk/​arsenic, 2000), Vietnam (UNESCAP-UNICEF-WHO, United Nations economic and social commission for Asia and the Pacific, geology and health: solving arsenic crisis in Asia and Pacific region. UNESCAP-UNICEF-WHO expert group meeting, Bangkok, 2001) and Nepal (Tandukar et al. Proceedings of International Conference on arsenic in Asia-Pacific Region, Adelaide, 2001). In India, apart from West Bengal, arsenic contamination has been reported in other states like Ballia (Chauhan et al. Chemosphere 75(1):83–91, 2009); Ghazipur and Varanasi districts of UP (Ahamed et al. Sci Total Environ 370(2–3):310–322, 2006), middle Gangetic plain of Bihar (Chakraborti et al. Environ Health Perspect 111(9):1194–1201, 2003), Sahibgunj district of Jharkand (Bhattacharjee et al. Chemosphere 58:1203–1217, 2005), and Northeastern Karnataka (Chakraborti et al. J Hazard Mater 262:1048–1055, 2012). Till date, the data from various reports and research papers indicate that arsenic in ground water used for drinking occurs in more than 250 blocks in approximately 55 districts of India.

There is much similarity between the geological formation of the Gangetic and the Brahmaputra plains as both are formed by sedimentation of soils from the Himalayas. The shallow aquifers of both the plains are also expected to be similar except for some variations caused by difference in rainfall and occurrence of floods. Hence, the findings of arsenicosis and arsenic (As) contamination of groundwater in Bangladesh and the Gangetic plains of India (Chakraborti et al. Talanta 58:3–22, 2002; Chatterjee et al. Analyst 120:643–650, 1995) had indicated the possibility of similar fate of the Brahmaputra plains and the Borak plains of the north-eastern region of India also, which was soon proven to be true.