title: Speciation of sulfate in size-fractionated aerosol particles using sulfur K-edge X-ray absorption near-edge structure.
abstract: X-ray absorption near-edge structure (XANES) at sulfur K-edge was used to determine the sulfate species present in size-fractionated aerosol particles based on the postedge structure after the main absorption peak in the XANES region. A comparison of the XANES spectra of reference sulfate materials and aerosol samples collected in Tsukuba in Japan clearly showed that (NH4)2SO4 was the main sulfur species in particles with a smaller diameter and CaSO4 x 2H2O (gypsum) was the main sulfur species in particles with a larger diameter. A simulation of the XANES spectra by reference materials allows us to obtain the quantitative mixing ratios of the different sulfate species present in the aerosol samples. The presence of minor sulfur species other than (NH4)2SO4 and gypsum at the surface of mineral aerosols is suggested in our simulations and by a surface-sensitive conversion electron/He-ion yield XANES. In the absence of a contribution from a large dust event, the mole concentration of gypsum in the mineral aerosol fraction (particle diameter > 1 microm) determined by XANES is similar to that of Ca which is determined independently using ion chromatography. This shows that the Ca and sulfate in the mineral aerosols are present only as gypsum. Considering that calcite is the main Ca mineral in the original material arising from an arid and semiarid area in China, it is strongly suggested that gypsum is formed in aerosol during its long-range transportation by a reaction between calcite and sulfate ions.
authors.affiliation: Graduate School of Science and Laboratory for Multiple Isotope Research for Astro- and Geochemical Evolution, Hiroshima University, Japan. ytakaha@hiroshima-u.ac.jp
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kanai
authors.forename: Hikari
authors.initials: H
authors.lastname: Kamioka
authors.forename: Atsuyuki
authors.initials: A
authors.lastname: Ohta
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Maruyama
authors.forename: Zhiguang
authors.initials: Z
authors.lastname: Song
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shimizu
mesh_terms: D015502:Absorptiometry, Photon / Q000295:instrumentation / Q000379:methods*; D000336:Aerosols; D000393:Air Pollutants / Q000032:analysis*; D002118:Calcium / Q000737:chemistry*; D002133:Calcium Sulfate / Q000737:chemistry; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D015233:Models, Statistical; D013431:Sulfates / Q000032:analysis* / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry*; D014965:X-Rays
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D013431:Sulfates; D013455:Sulfur; D002118:Calcium; D002133:Calcium Sulfate