title: Arsenic fractionation and mineralogical characterization of sediments in the Cold Lake area of Alberta, Canada.
abstract: Elevated arsenic (As >0.01 mg L(-1)) in some domestic well water in the Cold Lake area of Alberta, Canada is of great concern for public health. To determine possible sources of groundwater As, sediments (n=135) collected from five different locations (up to ~300 m depth) in the area were characterized. Total As concentrations in the sediments varied from ~1 to 35 mg kg(-1). Sediments derived from shale contained high As (~13 mg kg(-1); n=14), particularly the shale of Lea Park formation where maximum average As was ~32 mg kg(-1) (n=2). Unoxidized sediments of Grand Centre (24.9 ± 4.2 mg kg(-1) As) and Bonnyville (19.9 ± 1.8 mg kg(-1) As) formations also contained high As. Sequential extraction procedure (SEP) revealed the dominance of exchangeable and specifically adsorbed As (6 to 46% of total As) in the sediments of varying As concentrations (0.8 to 35.4 mg kg(-1) As). The high As sediments (>7 mg kg(-1) As) also contained significant amount of sulfide bound As (11 to 34% of total As), while low As (<7 mg kg(-1) As) sediments had crystalline oxide minerals bound As (25 to 75% of total As) as major phases. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed the presence of pyrite, and μ-XRD analysis signaled the presence of arsenopyrite in sediments containing ~20 mg kg(-1) As. X-ray absorption near edge structure (XANES) spectroscopy analysis suggested dominance of arsenite (AsIII; ~60 to 90% of total As) in all the sediments. These findings may help to devise strategies to investigate mechanisms of As release into the groundwater.
authors.affiliation: Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2E3, Canada. Electronic address: mjaved@ualberta.ca.
authors.forename: Muhammad Babar
authors.initials: MB
authors.lastname: Javed
authors.affiliation: Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2E3, Canada. Electronic address: gary.kachanoski@mun.ca.
authors.forename: Gary
authors.initials: G
authors.lastname: Kachanoski
authors.affiliation: Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2E3, Canada. Electronic address: tariq.siddique@ualberta.ca.
authors.forename: Tariq
authors.initials: T
authors.lastname: Siddique
mesh_terms: D000416:Alberta; D001151:Arsenic / Q000032:analysis*; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D060106:Lakes / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D001151:Arsenic
keywords: Arsenic distribution; Fractionation; Geological formation; Mineralogy; Surficial deposits; XANES spectroscopy