title: Microscale characterization of sulfur speciation in lake sediments.
abstract: Prairie pothole lakes (PPLs) are naturally sulfur-enriched wetlands in the glaciated prairie region of North America. High sulfate levels and dynamic hydrogeochemistry in combination render PPLs a unique environment to explore the speciation of sedimentary sulfur (S). The goals of this research were to define and quantify the solid-phase S pools in PPL sediments and track seasonal dynamics of S speciation. A quantitative X-ray microprobe method was developed based on S 1s X-ray absorption near-edge structure (XANES) spectroscopy and multienergy X-ray fluorescence mapping. Three S pools-pyritic S, reduced organic S (organic mono- and disulfide), and oxidized S (inorganic sulfate, ester sulfate, and sulfonate)-were identified in PPL sediments. No significant seasonal variation was evident for total S, but S speciation showed a seasonal response. During the spring-summer transition, the reduced organic S decreased from 55 to 15 mol %, with a concomitant rise in the oxidized S. During the summer-fall transition, the trend reversed and the reduced organic S grew to 75 mol % at the expense of the oxidized S. The pyritic S, on the other hand, remained relatively constant (∼22 mol %) over time. The seasonal changes in S speciation have strong potential to force the cycling of elements such as mercury in prairie wetlands.
authors.affiliation: Department of Civil Engineering, University of Minnesota, 500 Pillsbury Drive Southeast, Minneapolis, Minnesota 55455, United States.
authors.forename: Teng
authors.initials: T
authors.lastname: Zeng
authors.forename: William A
authors.initials: WA
authors.lastname: Arnold
authors.forename: Brandy M
authors.initials: BM
authors.lastname: Toner
mesh_terms: D002244:Carbon / Q000032:analysis; D017753:Ecosystem; D019015:Geologic Sediments / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D060106:Lakes / Q000737:chemistry*; D010084:Oxidation-Reduction; D016062:Porosity; D012621:Seasons; D013431:Sulfates / Q000032:analysis; D013440:Sulfides / Q000032:analysis / Q000737:chemistry; D013455:Sulfur / Q000032:analysis*; D013499:Surface Properties; D013816:Thermodynamics; D014481:United States; D056928:X-Ray Absorption Spectroscopy
chemical_list: D013431:Sulfates; D013440:Sulfides; C011342:pyrite; D013455:Sulfur; D002244:Carbon; D007501:Iron