Identification of sources of lead in the atmosphere by chemical speciation using X-ray absorption near-edge structure (XANES) spectroscopy

Sources of Pb pollution in the local atmosphere together with Pb species, major ions, and heavy metal concentrations in a size-fractionated aerosol sample from Higashi-Hiroshima(Japan) have been determined by X-ray absorption near-edge structure(XANES) spectroscopy, ion chromatography, and ICP-MS/AES, respectively. About 80% of total Pb was concentrated in fine aerosol particles. Lead species in the coarse aerosol particles were PbC2O4, 2PbCO3·Pb(OH)2, and Pb(NO3)2, whereas Pb species in the fine aerosol particles were PbC2O4, PbSO4, and Pb(NO3)2. Chemical speciation and abundance data suggested that the source of Pb in the fine aerosol particles was different from that of the coarse ones. The dominant sources of Pb in the fine aerosol particles were judged to be fly ash from a municipal solid waste incinerator and heavy oil combustion. For the coarse aerosol particles, road dust was considered to be the main Pb source. In addition to Pb species, elemental concentrations in the aerosols were also determined. The results suggested that Pb species in size-fractionated aerosols can be used to identify the origin of aerosol particles in the atmosphere as an alternative to Pb isotope ratio measurement.     

Oxidation of antimony (III) in soil by manganese (IV) oxide using X-ray absorption fine structure

The oxidation of antimony (III) in soils was studied using X-ray absorption fine structure (XAFS) spectra. An andosol soil sample and artificial soil samples (SiO₂ blended with iron (III) hydroxide and manganese (IV) oxide) were used herein. After adding antimony (III) oxide to all soil samples, the oxidation process was observed by recording the XAFS spectra of Sb K-edge, Fe K-edge, and Mn K-edge. The results indicated that manganese (IV) oxide played an important role in the oxidation of Sb(III); however iron (III) hydroxide was not directly related to the reaction. During a 2-hr continuous Sb K-edge X-ray absorption near edge structure (XANES) measurement with an interval of 1 min of one of the artificial soil samples (SiO₂ + MnO₂ + Sb₂O₃), a pseudo-first-order reaction was determined with an average estimated rate of 0.52 ± 0.04 hr^? 1. Compared to the lower oxidation rate of andosol, it is suggested that because of the low concentration of Mn(IV) in natural soils, the oxidation process of Sb(III) might be relatively slow and require more time to convert Sb(III) to Sb(V).