title: Thermally Released Arsenic in Porewater from Sediments in the Cold Lake Area of Alberta, Canada.
abstract: Elevated arsenic (As) in aquifers in close proximity to in situ oil sands extraction in the Cold Lake area, Alberta, Canada is attributed to high temperature steam (~200 °C) injected into oil sands deposits to liquefy bitumen. Heat propagated from hot injection wells alters physicochemical properties of the surrounding sediments and associated porewater. Seven sediments from four different cores drilled up to ~300 m depth collected from different locations in the area were used to study the thermal effect (~200 °C) on As distribution in the sediments and its release into porewater. Sediments were moistened with synthetic aquifer or deionized water according to the moisture regimes present in aquitard, aquifer and fractured zones. Heat application greatly released As in the porewater (500-5200 and 1200-6600 μg L(-1)) from aquifer and fractured sediments, respectively. Mass balance of As chemical fractionation showed that ~89-100% of As in porewater was released from exchangeable and specifically adsorbed As in the sediments. Heat application also altered As distribution in the sediments releasing As from exchange surfaces and amorphous Fe oxides to soluble As fraction. The results provide great insight into As release mechanisms warranting development of strategies to mitigate groundwater As contamination during industrial operation.
authors.affiliation: Department of Renewable Resources, University of Alberta , Edmonton, AB T6G 2G7, Canada.
authors.forename: Muhammad Babar
authors.initials: MB
authors.lastname: Javed
authors.affiliation: Department of Renewable Resources, University of Alberta , Edmonton, AB T6G 2G7, Canada.
authors.forename: Tariq
authors.initials: T
authors.lastname: Siddique
mesh_terms: D000416:Alberta; D001151:Arsenic / Q000032:analysis*; D019015:Geologic Sediments / Q000737:chemistry*; D060587:Groundwater / Q000032:analysis / Q000737:chemistry; D006358:Hot Temperature; D006838:Hydrocarbons; D061329:Oil and Gas Fields; D014874:Water Pollutants, Chemical / Q000032:analysis*; D060986:Water Wells
chemical_list: D006838:Hydrocarbons; D014874:Water Pollutants, Chemical; C006647:asphalt; D001151:Arsenic