title: Arsenic release from Floridan Aquifer rock during incubations simulating aquifer storage and recovery operations.
abstract: While aquifer storage and recovery (ASR) is becoming widely accepted as a way to address water supply shortages, there are concerns that it may lead to release of harmful trace elements such as arsenic (As). Thus, mechanisms of As release from limestone during ASR operations were investigated using 110-day laboratory incubations of core material collected from the Floridan Aquifer, with treatment additions of labile or refractory dissolved organic matter (DOM) or microbes. During the first experimental phase, core materials were equilibrated with native groundwater lacking in DO to simulate initial non-perturbed anaerobic aquifer conditions. Then, ASR was simulated by replacing the native groundwater in the incubations vessels with DO-rich ASR source water, with DOM or microbes added to some treatments. Finally, the vessels were opened to the atmosphere to mimic oxidizing conditions during later stages of ASR. Arsenic was released from aquifer materials, mainly during transitional periods at the beginning of each incubation stage. Most As released was during the initial anaerobic experimental phase via reductive dissolution of Fe oxides in the core materials, some or all of which may have formed during the core storage or sample preparation period. Oxidation of As-bearing Fe sulfides released smaller amounts of As during the start of later aerobic experimental phases. Additions of labile DOM fueled microbially-mediated reactions that mobilized As, while the addition of refractory DOM did not, probably due to mineral sorption of DOM that made it unavailable for microbial utilization or metal chelation. The results suggest that oscillations of groundwater redox conditions, such as might be expected to occur during an ASR operation, are the underlying cause of enhanced As release in these systems. Further, ASR operations using DOM-rich surface waters may not necessarily lead to additional As releases.
authors.affiliation: Department of Geological Sciences, University of Florida, 241 Williamson Hall, P.O. Box 112120, Gainesville, FL 32611, USA.
authors.forename: Jin
authors.initials: J
authors.lastname: Jin
authors.affiliation: Department of Geological Sciences, University of Florida, 241 Williamson Hall, P.O. Box 112120, Gainesville, FL 32611, USA. Electronic address: azimmer@ufl.edu.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Zimmerman
authors.affiliation: Florida Geological Survey, 3000 Commonwealth Blvd., Tallahassee, FL 32303, USA.
authors.forename: Stuart B
authors.initials: SB
authors.lastname: Norton
authors.affiliation: Department of Environmental Engineering Sciences, University of Florida, 217 A.P. Black Hall, P.O. Box 116450, Gainesville, FL 32611, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Annable
authors.affiliation: Department of Soil and Water Science, University of Florida, 2181 McCarty Hall, P.O. Box 110290, Gainesville, FL 32611, USA.
authors.forename: Willie G
authors.initials: WG
authors.lastname: Harris
mesh_terms: D001151:Arsenic / Q000032:analysis*; D004784:Environmental Monitoring; D005431:Florida; D060587:Groundwater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification; D014881:Water Supply
chemical_list: D014874:Water Pollutants, Chemical; D001151:Arsenic
keywords: Aquifer storage and recovery (ASR); Arsenic; Carbonate rocks; Dissolved organic matter (DOM); Floridan Aquifer; Groundwater