| 城市雾天单个矿物颗粒物理和化学特征 |
| 摘要点击 6383 全文点击 2505 投稿时间：2007-02-10 修订日期：2007-04-02 |
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| 中文关键词 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） |
| 英文关键词 aerosol scanning electron microscopy with energy dispersive X-ray (SEM-EDX) individual particle analysis fog episode inhalable particles (PM10) |
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| 中文摘要 |
| 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0.1～0.3 μm和1～2.5 μm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. |
| 英文摘要 |
| 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. |
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