title: Dissolved Organic Matter Quality in a Shallow Aquifer of Bangladesh: Implications for Arsenic Mobility.
abstract: In some high arsenic (As) groundwater systems, correlations are observed between dissolved organic matter (DOM) and As concentrations, but in other systems, such relationships are absent. The role of labile DOM as the main driver of microbial reductive dissolution is not sufficient to explain the variation in DOM-As relationships. Other processes that may also influence As mobility include complexation of As by dissolved humic substances, and competitive sorption and electron shuttling reactions mediated by humics. To evaluate such humic DOM influences, we characterized the optical properties of filtered surface water (n = 10) and groundwater (n = 24) samples spanning an age gradient in Araihazar, Bangladesh. Further, we analyzed large volume fulvic acid (FA) isolates (n = 6) for optical properties, C and N content, and (13)C NMR spectroscopic distribution. Old groundwater (>30 years old) contained primarily sediment-derived DOM and had significantly higher (p < 0.001) dissolved As concentration than groundwater that was younger than 5 years old. Younger groundwater had DOM spectroscopic signatures similar to surface water DOM and characteristic of a sewage pollution influence. Associations between dissolved As, iron (Fe), and FA concentration and fluorescence properties of isolated FA in this field study suggest that aromatic, terrestrially derived FAs promote As-Fe-FA complexation reactions that may enhance As mobility.
authors.affiliation: INSTAAR, University of Colorado , Boulder, Colorado 80309-0450, United States.|Department of Civil, Construction, and Environmental Engineering, San Diego State University , San Diego, California 92182, United States.
authors.forename: Natalie
authors.initials: N
authors.lastname: Mladenov
authors.affiliation: School of Earth and Environmental Sciences, Queens College, City University of New York , Flushing, New York 11367, United States.|Lamont-Doherty Earth Observatory, Columbia University , Palisades, New York 10964, United States.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: INSTAAR, University of Colorado , Boulder, Colorado 80309-0450, United States.
authors.forename: Bailey
authors.initials: B
authors.lastname: Simone
authors.affiliation: School of Natural Sciences, St. Edward's University , 3001 S. Congress Ave, Austin, Texas 78704, United States.
authors.forename: Theresa M
authors.initials: TM
authors.lastname: Bilinski
authors.affiliation: INSTAAR, University of Colorado , Boulder, Colorado 80309-0450, United States.
authors.forename: Diane M
authors.initials: DM
authors.lastname: McKnight
authors.affiliation: INSTAAR, University of Colorado , Boulder, Colorado 80309-0450, United States.
authors.forename: Diana
authors.initials: D
authors.lastname: Nemergut
authors.affiliation: Lamont-Doherty Earth Observatory, Columbia University , Palisades, New York 10964, United States.
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Radloff
authors.affiliation: School of Earth and Environmental Sciences, Queens College, City University of New York , Flushing, New York 11367, United States.|Department of Environmental Science and Management, North South University , Bashundhara, Dhaka-1229, Bangladesh.
authors.forename: M Moshiur
authors.initials: MM
authors.lastname: Rahman
authors.affiliation: Department of Geology, University of Dhaka , Dhaka-1000, Bangladesh.
authors.forename: Kazi Matin
authors.initials: KM
authors.lastname: Ahmed
mesh_terms: D001151:Arsenic / Q000032:analysis*; D001459:Bangladesh; D005453:Fluorescence; D019015:Geologic Sediments / Q000032:analysis; D060587:Groundwater / Q000032:analysis* / Q000737:chemistry; D006812:Humic Substances / Q000032:analysis; D007501:Iron / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D012722:Sewage; D014874:Water Pollutants, Chemical / Q000032:analysis; D018508:Water Purification / Q000379:methods
chemical_list: D006812:Humic Substances; D012722:Sewage; D014874:Water Pollutants, Chemical; D007501:Iron; D001151:Arsenic