title: Role of competing ions in the mobilization of arsenic in groundwater of Bengal Basin: insight from surface complexation modeling.
abstract: This study assesses the role of competing ions in the mobilization of arsenic (As) by surface complexation modeling of the temporal variability of As in groundwater. The potential use of two different surface complexation models (SCMs), developed for ferrihydrite and goethite, has been explored to account for the temporal variation of As(III) and As(V) concentration, monitored in shallow groundwater of Bengal Basin over a period of 20 months. The SCM for ferrihydrite appears as the better predictor of the observed variation in both As(III) and As(V) concentrations in the study sites. It is estimated that among the competing ions, PO4(3-) is the major competitor of As(III) and As(V) adsorption onto Fe oxyhydroxide, and the competition ability decreases in the order PO4(3-) ≫ Fe(II) > H4SiO4 = HCO3(-). It is further revealed that a small change in pH can also have a significant effect on the mobility of As(III) and As(V) in the aquifers. A decrease in pH increases the concentration of As(III), whereas it decreases the As(V) concentration and vice versa. The present study suggests that the reductive dissolution of Fe oxyhydroxide alone cannot explain the observed high As concentration in groundwater of the Bengal Basin. This study supports the view that the reductive dissolution of Fe oxyhydroxide followed by competitive sorption reactions with the aquifer sediment is the processes responsible for As enrichment in groundwater.
authors.affiliation: KTH - International Groundwater Arsenic Research Group, Division of Land and Water Resources Engineering, Department of Sustainable Development, Environmental Sciences and Engineering, KTH Royal Institute of Technology, Teknikringen 76, SE-100 44 Stockholm, Sweden; Department of Chemistry, University of Kalyani, 741235 Kalyani, West Bengal, India. Electronic address: ashis@kth.se.
authors.forename: Ashis
authors.initials: A
authors.lastname: Biswas
authors.affiliation: KTH - International Groundwater Arsenic Research Group, Division of Land and Water Resources Engineering, Department of Sustainable Development, Environmental Sciences and Engineering, KTH Royal Institute of Technology, Teknikringen 76, SE-100 44 Stockholm, Sweden; Department of Soil and Environment, Swedish University of Agricultural Sciences, Box 7014, SE-750 07 Uppsala, Sweden.
authors.forename: Jon Petter
authors.initials: JP
authors.lastname: Gustafsson
authors.affiliation: Institute of Mineralogy and Geochemistry, Karlsruhe Institute of Technology, Adenauerring 20b, D-76131 Karlsruhe, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Neidhardt
authors.affiliation: KTH - International Groundwater Arsenic Research Group, Division of Land and Water Resources Engineering, Department of Sustainable Development, Environmental Sciences and Engineering, KTH Royal Institute of Technology, Teknikringen 76, SE-100 44 Stockholm, Sweden; Department of Chemistry, University of Kalyani, 741235 Kalyani, West Bengal, India.
authors.forename: Dipti
authors.initials: D
authors.lastname: Halder
authors.affiliation: Department of Chemistry, University of Kalyani, 741235 Kalyani, West Bengal, India.
authors.forename: Amit K
authors.initials: AK
authors.lastname: Kundu
authors.affiliation: Department of Chemistry, University of Kalyani, 741235 Kalyani, West Bengal, India.
authors.forename: Debashis
authors.initials: D
authors.lastname: Chatterjee
authors.affiliation: Institute of Mineralogy and Geochemistry, Karlsruhe Institute of Technology, Adenauerring 20b, D-76131 Karlsruhe, Germany.
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Berner
authors.affiliation: KTH - International Groundwater Arsenic Research Group, Division of Land and Water Resources Engineering, Department of Sustainable Development, Environmental Sciences and Engineering, KTH Royal Institute of Technology, Teknikringen 76, SE-100 44 Stockholm, Sweden.
authors.forename: Prosun
authors.initials: P
authors.lastname: Bhattacharya
mesh_terms: D001151:Arsenic / Q000032:analysis*; D004784:Environmental Monitoring; D005290:Ferric Compounds / Q000032:analysis; D060587:Groundwater / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000032:analysis; D008962:Models, Theoretical; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D005290:Ferric Compounds; D007477:Ions; D014874:Water Pollutants, Chemical; C092844:ferric oxyhydroxide; D001151:Arsenic
keywords: Arsenic mobilization; Bengal Basin; Competing ions; Groundwater; Surface complexation modeling; Temporal variability