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Abstract
Arsenic (As) enrichment in groundwater has become a major global environmental disaster. Groundwater samples were collected from 64 sites located in the districts of 24-Parganas (S), and Nadia in West Bengal, India (Bhagirathi sub-basin), and 51 sites located in the districts of Comilla, Noakhali, Magura, Brahman baria, Laxmipur, Munshiganj, Faridpur and Jhenaida in Bangladesh (Padma-Meghna sub-basin). Groundwater samples were also collected from two As-affected areas (Chianan and Lanyang plains) of Taiwan (n = 26). The concentrations of major solutes in groundwater of the Padma-Meghna sub-basin are more variable than the Bhagirathi sub-basin, suggesting variations in the depositional and hydrological settings. Arsenic concentrations in groundwaters of the studied areas showed large variations, with mean As concentrations of 125 μg/L (range: 0.20 to 1,301 μg/L) in Bhagirathi sub-basin, 145 μg/L (range: 0.20 to 891 μg/L) in Padma-Meghna sub-basin, 209 μg/L (range: 1.3 to 575 μg/L) in Chianan plain, and 102 μg/L (range: 2.5 to 348 μg/L) in Lanyang plain groundwater. The concentrations of Fe, and Mn are also highly variable, and are mostly above the WHO-recommended guideline values and local (Indian and Bangladeshi) drinking water standard. Piper plot shows that groundwaters of both Bhagirathi and Padma-Meghna sub-basins are of Ca–HCO3 type. The Chianan plain groundwaters are of Na–Cl type, suggesting seawater intrusion, whereas Lanyang plain groundwaters are mostly of Na–HCO3 type. The study shows that reductive dissolution of Fe(III)-oxyhydroxides is the dominant geochemical process releasing As from sediment to groundwater in all studied areas.
Acknowledgment
JPM would like to thank the National Science Council of Taiwan for financial support. PB would like to thank National Cheng Kung University, Taiwan for the visiting professorship under the Top 100 University Advancement Scheme. JB thanks the National Science Council of Taiwan for the financial support. The authors, especially PB, acknowledge the Swedish International Development Cooperation Agency (Sida) – Department of Development Partnerships for the research project within the framework of the Sustainable Arsenic Mitigation – SASMIT (Sida Contribution 73000854) as well as the Strategic Environmental Research Foundation (MISTRA), Sweden for their research support (dnr: 2005-035-137) to the KTH-International Groundwater Arsenic Research Group at the Department of Land and Water Resources Engineering, Royal Institute of Technology, Stockholm. The analytical support by Ann Fylkner and Monica Löwen at the laboratories of KTH, Lena Lundman at Tema Vatten, Linköping University are gratefully acknowledged. We deeply appreciate the editorial support of Colleen Heavens, Production Editor, Taylor & Francis LLC, for her meticulous support during the final proof editing of this manuscript.
