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.

Sulphur speciation of PM10 samples by XANES spectroscopy

“…Comparing the shape of the peak and also its second derivative with literature data for different sulphate salts [25], as well as the standard CaSO 4 spectrum, it may be deduced that the sulphate is present predominately in the CaSO 4 form. These sulphate particles are likely formed by the reaction between CaCO 3 and sulphate ions in the atmosphere [36].…”

“…Huggins and colleagues [24] worked on some standard reference materials and on just one real PM 10 sample; in this case, the only S species that have been detected were sulphates. Takahashi et al [25] report speciative S analyses from size-fractionated aerosols from a single site, collected in Japan during an episode of heavy dust transport from China and in absence of such transport. Matsumoto and colleagues [26] report some S speciative analyses on diesel vehicular emissions.…”

Characterization of mineral particles in winter fog of Beijing analyzed by TEM and SEM

“…Particularly, surfaces of mineral particles play an important role as a reaction site for sulfate ions in the atmosphere (Takahashi et al 2006;Pandis and Seinfeld 1989). In our samples, "S+Ca" and "Ca+S" subtypes in fog sample show higher percentages than those in the nonfog samples (Table 2).…”

Spatial correlativity of atmospheric particulate components simultaneously collected in Japan

“…The spatial correlatives were slightly weaker for Ca 2+ , K + , Na + , and Cl − . (NH 4 ) 2 SO 4 and NH 4 NO 3 are generally known as secondary formation particles, which possibly suggests LRT partially along with a (NH 4 )HSO 4 , H 2 SO 4 (Hatakeyama et al 2006;Satsumabayashi 2007), and CaSO 4 based on the X-ray absorption fine structure (XAFS) study (Takahashi et al 2006). Figure 8 shows the spatial correlation coefficients of metallic elements toward Osaka.…”