title: [Physical and chemical characteristics of individual mineral particles in an urban fog episode].
abstract: Field emission scanning electron microscopy (FESEM) and scanning electron microscopy with energy dispersive X-ray detector (SEM-EDX) were used to study the four aerosol samples collected in Beijing air during the fog and non-fog episodes in winter. Size-distribution of mineral particles in fog sample displayed two major peaks at the size range of 0.1-0.3 microm and 1-2.5 microm. EDX analyses indicated that the major chemical compositions varied greatly in the individual mineral particles of the fog and non-fog episodes, especially the sulfur. A total of 9 different mineral categories were classified, namely, "Si-rich", "Ca-rich", "S-rich", "Fe-rich", "Mg-rich", "Al-rich", "Ti-rich", "K-rich" and "Cl-rich". About 55% of the "Ca-rich" in the fog samples comprised of Ca (50% +/- 1.2%)and S (37% +/- 1.6%) and about 72% of the "S-rich" comprised of S (44% +/- 1.5%) and Ca (33% +/- 2%), illustrating that particles with abundant sulfur were also enriched with abundant calcium. It is suggested that the "Ca-rich" alkali minerals could alleviate acidity of the fog water in Beijing air. The S/Ca mean ratio of mineral particles in the fog sample was 6.11, being 8 times higher than the S/Ca mean ratio of the non-fog samples (0.73). This result showed that sulfuration on the surfaces of aerosol particles was extremely severe, and that the conversion efficiency from SO2 to sulfates was relatively high.
authors.affiliation: State Key Laboratory of Coal Resources and Safe Mining, Department of Resources and Earth Science, China University of Mining and Technology in Beijing, Beijing 100083, China. liwj@cumtb.edu.cn
authors.forename: Wei-Jun
authors.initials: WJ
authors.lastname: Li
authors.forename: Long-Yi
authors.initials: LY
authors.lastname: Shao
authors.forename: Zong-Bo
authors.initials: ZB
authors.lastname: Shi
authors.forename: Jin-Juan
authors.initials: JJ
authors.lastname: Li
authors.forename: Shu-Shen
authors.initials: SS
authors.lastname: Yang
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry; D002681:China; D002947:Cities; D008903:Minerals / Q000032:analysis* / Q000737:chemistry; D010316:Particle Size; D014887:Weather
chemical_list: D000393:Air Pollutants; D008903:Minerals