Controls on high and low groundwater arsenic on the opposite banks of the lower reaches of River Ganges, Bengal basin, India Abhijit Mukherjee a,b, ⁎, Alan E. Fryar c , Emily M. Eastridge c , Rachel S. Nally c , Madhumita Chakraborty a , Bridget R. Scanlon d a Department of Geology and Geophysics, Indian Institute of Technology Kharagpur, Kharagpur 721302, India b School of Environmental Science and Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India c Department of Earth and Environmental Sciences, University of Kentucky, 101 Slone Building, Lexington, KY 40506-0053, USA d Bureau of Economic Geology, University of Texas at Austin, University Station, Box X, Austin, TX 78713-8924, USA GRAPHICAL ABSTRACT abstract article info Article history: Received 24 December 2017 Received in revised form 22 June 2018 Accepted 29 June 2018 Available online xxxx Editor: F.M. Tack Understanding the controls on spatial variability of groundwater arsenic (As) is critical for mitigating As contam- ination. The objective of this study is to determine controls on previously unexplained differences in groundwa- ter As concentrations, which are high along the east bank and low along the west bank of the River Bhagirathi- Hoogly (B-H), the primary Indian distributary of the River Ganges, on the western margin of the Bengal basin. A total of 54 wells were sampled after the monsoon season at four sites (two each east and west of the B-H) in Murshidabad district, West Bengal, for field parameters, major and minor solutes, and stable isotopes of water. An additional four boreholes were drilled for analyses of sediment texture, mineralogy, total organic and inor- ganic carbon, and total As and other metal(loid)s. Results show that higher As in east-bank groundwater (median 0.031 mg/L) is associated with generally more anoxic conditions (higher median total Fe and lower median E H and NO 3 - ) relative to west-bank groundwater (median As b 0.001 mg/L), consistent with previous studies. In con- trast, concentrations of Mn in the study area are highest in west-bank wells near the B-H. Carbonate and silicate weathering appear to be more important in east- and west-bank groundwater, respectively, which may reflect differences in sediment sources. Ranges of total As are similar in east- and west-bank sediments. Relatively de- pleted values of δ 18 O and δ 2 H in the east-bank aquifer and streams appear to reflect focused recharge through paleochannels, while relatively enriched west-bank values suggest diffuse recharge to upland aquifers. We Keywords: Bengal basin Arsenic Groundwater recharge Redox condition Sustainable drinking water supply Science of the Total Environment 645 (2018) 1371–1387 ⁎ Corresponding author. E-mail addresses: amukh2@gmail.com, abhijit@gg.iitkgp.ernet.in (A. Mukherjee). https://doi.org/10.1016/j.scitotenv.2018.06.376 0048-9697/© 2018 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv