title: Sulfur speciation in soil by S K-Edge XANES spectroscopy: comparison of spectral deconvolution and linear combination fitting.
abstract: Defined, quartz-diluted mixtures of sulfur (S) compounds with different oxidation state (OS) were analyzed by K-edge XANES spectroscopy using linear combination fitting (LCF) and spectrum deconvolution by fitting several Gaussian and arctangent functions (GCF). Additionally, for different soils the S speciation as calculated by both methods was compared with results of a wet-chemical S speciation. For mixtures of FeS, L-cysteine, and Na2SO4, the S speciation was recovered with satisfactory accuracy and precision by both methods at the 2 and 0.2 mg S g(-1) level. For GCF, white-line peaks must be normalized with respect to their OS-specific absorption cross-section. LCF must be conducted with dilute reference compounds to avoid self-absorption effects. For mixtures of FeS, FeS2, S°, and L-cysteine, both procedures showed poor accuracy. For the soils, similar percentages of reduced inorganic S, organic S, and sulfate were calculated by LCF, GCF, and wet chemical S speciation. GCF allows a fair estimation of S species groups with different OS (inorganic reduced S, organic reduced S, organic intermediate S, oxidized S) in soils without standards. If dilute standards of all S compounds assumed to be present in a sample are available, LCF is more objective and allows a more detailed S speciation.
authors.affiliation: Technische Universität München, Lehrstuhl für Bodenkunde, D-85354 Freising, Germany. prietzel@wzw.tum.de
authors.forename: Jörg
authors.initials: J
authors.lastname: Prietzel
authors.forename: Anna
authors.initials: A
authors.lastname: Botzaki
authors.forename: Nora
authors.initials: N
authors.lastname: Tyufekchieva
authors.forename: Mareike
authors.initials: M
authors.lastname: Brettholle
authors.forename: Jürgen
authors.initials: J
authors.lastname: Thieme
authors.forename: Wantana
authors.initials: W
authors.lastname: Klysubun
mesh_terms: D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy / Q000295:instrumentation / Q000379:methods*
chemical_list: D012987:Soil; D012989:Soil Pollutants; D013455:Sulfur