[Physical and chemical characteristics of individual mineral particles in an urban fog episode].
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.
Li
Wei-Jun
WJ
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
Shao
Long-Yi
LY
Shi
Zong-Bo
ZB
Li
Jin-Juan
JJ
Yang
Shu-Shen
SS
D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry; D002681:China; D002947:Cities; D008903:Minerals / Q000032:analysis* / Q000737:chemistry; D010316:Particle Size; D014887:Weather
D000393:Air Pollutants; D008903:Minerals