title: Stimulation of Microbially Mediated Arsenic Release in Bangladesh Aquifers by Young Carbon Indicated by Radiocarbon Analysis of Sedimentary Bacterial Lipids.
abstract: The sources of reduced carbon driving the microbially mediated release of arsenic to shallow groundwater in Bangladesh remain poorly understood. Using radiocarbon analysis of phospholipid fatty acids (PLFAs) and potential carbon pools, the abundance and carbon sources of the active, sediment-associated, in situ bacterial communities inhabiting shallow aquifers (<30 m) at two sites in Araihazar, Bangladesh, were investigated. At both sites, sedimentary organic carbon (SOC) Δ(14)C signatures of -631 ± 54‰ (n = 12) were significantly depleted relative to dissolved inorganic carbon (DIC) of +24 ± 30‰ and dissolved organic carbon (DOC) of -230 ± 100‰. Sediment-associated PLFA Δ(14)C signatures (n = 10) at Site F (-167‰ to +20‰) and Site B (-163‰ to +21‰) were highly consistent and indicated utilization of carbon sources younger than the SOC, likely from the DOC pool. Sediment-associated PLFA Δ(14)C signatures were consistent with previously determined Δ(14)C signatures of microbial DNA sampled from groundwater at Site F indicating that the carbon source for these two components of the subsurface microbial community is consistent and is temporally stable over the two years between studies. These results demonstrate that the utilization of relatively young carbon sources by the subsurface microbial community occurs at sites with varying hydrology. Further they indicate that these young carbon sources drive the metabolism of the more abundant sediment-associated microbial communities that are presumably more capable of Fe reduction and associated release of As. This implies that an introduction of younger carbon to as of yet unaffected sediments (such as those comprising the deeper Pleistocene aquifer) could stimulate microbial communities and result in arsenic release.
authors.affiliation: School of Geography and Earth Sciences, McMaster University , Hamilton, Ontario L8S 4L8, Canada.
authors.forename: K J
authors.initials: KJ
authors.lastname: Whaley-Martin
authors.affiliation: Environmental Sciences Department, Barnard College , New York, New York 10027, United States.
authors.forename: B J
authors.initials: BJ
authors.lastname: Mailloux
authors.affiliation: Lamont-Doherty Earth Observatory, Columbia University , Palisides, New York 10964, United States.
authors.forename: A
authors.initials: A
authors.lastname: van Geen
authors.affiliation: Lamont-Doherty Earth Observatory, Columbia University , Palisides, New York 10964, United States.
authors.forename: B C
authors.initials: BC
authors.lastname: Bostick
authors.affiliation: Environmental Sciences Department, Barnard College , New York, New York 10027, United States.
authors.forename: R F
authors.initials: RF
authors.lastname: Silvern
authors.affiliation: Environmental Sciences Department, Barnard College , New York, New York 10027, United States.
authors.forename: C
authors.initials: C
authors.lastname: Kim
authors.affiliation: Department of Geology, University of Dhaka , Dhaka 1000, Bangladesh 10964.
authors.forename: K M
authors.initials: KM
authors.lastname: Ahmed
authors.affiliation: Department of Geology, University of Dhaka , Dhaka 1000, Bangladesh 10964.
authors.forename: I
authors.initials: I
authors.lastname: Choudhury
authors.affiliation: School of Geography and Earth Sciences, McMaster University , Hamilton, Ontario L8S 4L8, Canada.
authors.forename: G F
authors.initials: GF
authors.lastname: Slater
mesh_terms: D001151:Arsenic; D001459:Bangladesh; D002244:Carbon; D019015:Geologic Sediments / Q000382:microbiology; D060587:Groundwater / Q000382:microbiology; D010743:Phospholipids; D014874:Water Pollutants, Chemical
chemical_list: D010743:Phospholipids; D014874:Water Pollutants, Chemical; D002244:Carbon; D001151:Arsenic