Department of Chemistry. Kalyani University, Kalyani-741 235, West Bengal, India soil Mechanics Section, River Research Institute, West Bengal, P.O. HRRI, Nadia. West Bengal, India central Forensic Science Laboratory, 30, Gorachand Road, Kolkata-700 014, India E-mail : sujitclahiri@yahoo.com Manuscript received 29 November 2010, accepted 30 November 2010 The biogeochemical proccsses causing As-distribution in ground water of Bengal Delta plain (BDP) areas are not well understood but As-mobilization in ground water are well known. Increased As-mobilization in ground water is due to increased manmade activities like mining, greater use of ammonium and particularly phosphates (as fertilizers, detergents, animal and plant wastes) and excess withdrawal of water causing depletion of water table. Po 4 3- and also NH 4 + ions with minerals may cause displacement of As v or As III from arsenic bearing minerals. However, processes leading to the increase in As-mobilization in ground water (even in surface waters of ...