城市雾天单个矿物颗粒物理和化学特征  

Physical and Chemical Characteristics of Individual Mineral Particles in an Urban Fog Episode

作　　者：李卫军[1] 邵龙义[1] 时宗波[1] 李金娟[1] 杨书申[1] 

机构地区：[1]中国矿业大学(北京)资源与地球科学系煤炭资源与安全开采国家重点实验室,北京100083

出　　处：《环境科学》2008年第1期253-258,共6页Environmental Science

基　　金：国家重点基础研究发展规划(973)项目(2006CB403701);国家自然科学基金项目(40275040;40575065)

摘　　要：应用场发射扫描电镜（FESEM）和带能谱的扫描电镜（SEM-EDX）对北京冬季雾天和正常天气下收集的4个样品进行研究.雾天中矿物颗粒的数量-粒度分布的峰值出现在0.1-0.3μm和1-2.5μm之间，并且发现雾天出现的二次矿物颗粒的数量百分含量（4.67%）高于正常天气条件（0.12%）.单个矿物颗粒的EDX能谱显示，雾天和正常天气中单个矿物颗粒的主要化学成分有一定的差别，尤其是S元素.矿物颗粒分为9种不同类型：“富Si”、“富Ca”、“富S”、“富Fe”“富Mg”、“富Al”、“富Ti”、“富K”和“富Cl”，其中雾天“富Ca”中55%的颗粒含有Ca（50%±1.2%）和S（37%±1.6%），“富S”中72%的颗粒含有S（44%±1.5%）和Ca（33%±2%），说明了雾天中绝大部富集S的颗粒物中同时富集Ca，这在一定程度上说明了北京市大气中这些含Ca的碱性矿物对雾水酸性有一定的缓冲作用.雾天样品中S/Ca的平均比值为6.11，如果以冬季正常天气条件下S/Ca的均值0.73为背景值，雾天中S/Ca的比值是冬季正常天气的8倍，可见雾天中颗粒物表面的硫化现象相当严重，同时也显示出雾天SO2向硫酸盐的转化率比较高.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 μm and 1 - 2.5 μm. 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.

关 键 词：气溶胶 带能谱的扫描电镜(SEM/EDX) 单颗粒分析 雾天 可吸入颗粒物(PM10) 

分 类 号：X513[环境科学与工程—环境工程] X511