Geochemical characterization of arsenic-affected alluvial aquifers of the Bengal Delta (West Bengal and Bangladesh) and Chianan Plains (SW Taiwan): Implications for human health Bibhash Nath a,⇑ , Jyoti Prakash Maity b , Jiin-Shuh Jean b , Gavin Birch a , Sandeep Kar b , Huai-Jen Yang b , Ming-Kuo Lee c , Rasmani Hazra d , Debashis Chatterjee d a School of Geosciences, University of Sydney, Sydney, NSW 2006, Australia b Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan City 701, Taiwan c Department of Geology and Geography, Auburn University, AL, USA d Department of Chemistry, University of Kalyani, Nadia 741 235, West Bengal, India article info Article history: Received 6 October 2010 Accepted 18 January 2011 Available online 22 January 2011 Editorial handling by R. Fuge abstract Major ion and trace element analyses were performed on groundwater samples collected from the Bengal Delta (Chakdaha municipality, West Bengal and Manikgonj town, Bangladesh) and Chianan Plains (SW Taiwan) to compare geochemical characteristics. Results showed that concentrations of Na, K, Mg, Cl and SO 4 were generally higher in Chianan Plain (CNP) groundwaters, while high Ca was observed in Ben- gal Delta Plain (BDP) groundwater. Measured As concentrations in groundwaters of BDP and CNP showed large variations, with mean As concentrations of 221 lg/L (range: 1.1–476 lg/L) in Chakdaha, 60 lg/L (range: 0.30–202 lg/L) in Manikgonj, and 208 lg/L (range: 1.3–575 lg/L) in CNP groundwater. The Fe- reduction mechanism was found to be the dominant geochemical process in releasing As from sediment to groundwater in Chakdaha, West Bengal, however the Mn-reduction process was dominant in ground- waters of Manikgonj, Bangladesh. In Chianan Plain groundwater, a combination of geochemical processes (e.g., bacterial Fe-reduction, mineral precipitation and dissolution reactions) controlled release of As. Fluorescence spectral patterns of the groundwater showed low relative fluorescence intensity (RFI) of dissolved humic substances in BDP groundwater (mean: 63 and 72 QSU, Chakdaha and Manikgonj, respectively), while high RFI was observed in CNP groundwater (mean: 393 QSU). The FT-IR spectra of the extracted humic acid fractions from sediments of Chianan Plain showed a stronger aliphatic band at 2850–3000 cm 1 and a higher resolved fingerprint area (from 1700 to 900 cm 1 ) compared with BDP sediments. The geochemical differences between the study areas may play a crucial role in the clin- ical manifestation of Blackfoot disease observed only in Chianan Plain, SW Taiwan. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Natural enrichment of groundwater by As has become a crucial water quality problem in many parts of the world, including the USA, countries of the European Union, and countries of the south and East Asia (Smedley and Kinniburgh, 2002, and references therein). The prolonged consumption of groundwater with high As has emerged as a serious public health issue, leading to unprec- edented environmental problems, especially in parts of South and East Asia. The scale of the problem is notably grave in the Bengal Delta Plain (BDP), including West Bengal, India and Bangladesh, where the population relies heavily on groundwater for drinking (PHED, 1993; Acharyya et al., 1999; BGS and DPHE, 2001). Skin, lung, liver and prostate cancers are common among the population to mention only a few of the most severe consequences of As poi- soning (Smith et al., 2000; Guha Mazumder et al., 2000). The inci- dence of high As groundwater in the Chianan Plain (CNP) of SW Taiwan is best known for its unique cases of endemic Blackfoot dis- ease (BFD), a peripheral vascular disease (i.e., gangrene). Blackfoot disease was first reported between 1910 and 1920 (Kao and Kao, 1954) however, public awareness of the problem did not begin un- til it became endemic (Tseng et al., 1961). In India and Bangladesh, studies have indicated that As may be released due to reductive dissolution of Fe(III)-oxyhydroxide solids in the aquifer in low-lying areas where a small hydraulic gradient (<0.001 m/km) hinders groundwater flow and flushing of aquifers (e.g., BGS and DPHE, 2001). McArthur et al. (2004) further observed that the highest As concentrations tend to occur in the shallow Holocene aquifers where Fe(III)-oxyhydroxides are reduced, while 0883-2927/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.apgeochem.2011.01.029 ⇑ Corresponding author. Fax: +61 2 9351 2442. E-mail address: bibhash.nath@sydney.edu.au (B. Nath). Applied Geochemistry 26 (2011) 705–713 Contents lists available at ScienceDirect Applied Geochemistry journal homepage: www.elsevier.com/locate/apgeochem