| Ambient size-resolved particles in Xuanwei atmosphere were collected, and fieldsample campaign were carried out in April2011and November by using aMicro-orifice uniform deposit impactor(MOUDI). The polycarbonate filters wereused for particle collection. SEM/EDS, particle induced X-ray emission(PIXE),Synchrotron Radiation X-ray Absorption Fine Structure(XAFS), ElectronParamagnetic Resonance spectroscopy (EPR) and cell-free DCFH-DA assay wereused to identify the morphologies, elemental composition, and bioreactivity ofsize-resolved particles respectively.The total mass concentrations of the size-resolved particles collected in springand in early winter were316.9μg/m~3and92.82μg/m~3, respectively. Mass percentageof fine particles accounted for68%and61%of the total particulate mass in spring andin early winter samples, respectively, indicating that fine particles were the majorcomponent of the Xuanwei ambient particulate matters. Mass concentration of theambient particles had obvious seasonal variations, the mass levels of those particles inspring air were higher than those in winter air. The highest mass concentrations ofPM1.0~0.56in Xuanwei appeared in spring with values of48.78±8.4μg·m-3. The highestmass concentrations of PM1.8~1.0in winter with values of21.82±4.65μg·m-3.The results of SEM/EDS showed that airborne particles in Xuanwei air could beclassified into regular and irregular particles according to their morphology andelemental composition.The regular particles primarily consisted of soot aggregates,fly ash and mineral particles, and the irregular particles mostly exsited in coarseparticles. The regular particles were mainly found in fine particles. Soots and mineralparticles were the two dominant types of particles in the ultrafine particles.The mass concentrations of22elements, including Mg, Al, Si, P, S, Cl, K, Ca, ScTi, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Br, Mo, and Pb, were investigated in Xuanweisize-segregated air particles with PIXE. It demonstrated that the total massconcentration of these elements in spring particles and early winter particles was8747.37and11587.42ng/m~3, respectively. The results of PIXE results revealed thatcrustal elements (Ca, Ti Si, Fe) were mainly distributed in coarse particles, while tracemetals (Cr, Mn, Ni, Cu, Zn, Pb) dominated in the fine particle fraction, and S, atypical element emitted by coal combustion, mainly resided in fine particles collected from the winter atmosphere.XAFS results show that the Cu speciation in the different size fraction wasdifferent. Speciation of Cu in spring fine particles (PM0.56~0.32) is present as Cu (II),and significant amount of Cu is present as Cu (I) in the ultrafine particles (PM0.1), andCu in winter fine particles (PM0.56~0.32) is present as Cu (I), and significant amount ofCu is present as Cu (II) in the ultrafine particles (PM0.1), however.Enrichment factor analysis result revealed that anthropogenic elements were easilyabsorbed in fine and ultrafine particles.The enrichment factor vaule of these elementswas higher in fine and ultrafine particles than in coarse particles. Al、Si、K、Ca、Feand Ti could be enriched in all size ranges. The enrichment of P、S and Mn in fineparticles was the highest, while the enrichment of Cl、Sc、V、Cr、Co、Ni、Cu、Zn、As、Br、Mo and Pb in ultrafine particles was higher than that of such elements incoarse and ultrafine particles.EPR results indicated that the magnitude of free radical intensity caused bysize-resolved particles followed these patterns: fine particles> coarse particles>ultrafine particles for spring samples and ultrafine particles> fine particles> coarseparticles for winter samples. Cell-free DCFH assay results conclusively showed thatall of the measured particle suspensions displayed a higher oxidative potential thanthe negative control. |
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