title: Genesis of arsenic-rich groundwater and the search for alternative safe aquifers in the Gangetic Plain, India.
abstract: Distribution and mobilization of groundwater arsenic from a 1580-km(2) area in the Gangetic Plain was studied. A two-tier aquifer system made up of Quaternary sand layers exists within 300 m below ground. Arsenic concentration exceeding >50 microg/L is confined within the active floodplain of the Ganga River, affecting the top aquitard and upper 5- to 20-m slice of the underlying shallow aquifer. The genesis of arsenic was investigated by principal component analyses involving total dissolved solids, Ca(+2), Mg(+2), Na(+), K(+), HCO3-, Cl(-1), SO4(-2), NO3-, Fetotal, and Astotal and analyzed for 57 groundwater samples, hydrochemical facies analyses, aquifer-aquitard configuration, and water-level behaviour. A 20- to 25-m thick deeper aquifer, appearing at 190 to 205 m below ground and separated from the shallow aquifer by a thick clay sequence, was low in arsenic load (<2 microg/L). Hydrostratigraphy and pumping tests revealed that the deeper aquifer can be used for community drinking in contaminated areas.
authors.affiliation: Central Ground Water Board, Lok Nayak Bhawan, Dak Bunglow, Patna 800001, India. dsaha002@yahoo.com
authors.forename: Dipankar
authors.initials: D
authors.lastname: Saha
authors.affiliation: Central Ground Water Board, Lok Nayak Bhawan, Dak Bunglow, Patna 800001, India.
authors.forename: R R
authors.initials: RR
authors.lastname: Shukla
mesh_terms: D001151:Arsenic / Q000032:analysis*; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000032:analysis; D060587:Groundwater / Q000032:analysis* / Q000737:chemistry; D007194:India; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D014874:Water Pollutants, Chemical; D001151:Arsenic