基于TEM-EDS对四川盆地大气单颗粒气溶胶的研究

为了解四川盆地大气中单颗粒气溶胶理化特征，分别在该区域典型城市（成都市）和背景地区（峨眉山）进行了大气单颗粒样品采集.基于带能谱的透射电子显微镜（TEM-EDS）对两地累计3923个单颗粒的化学组成、形貌特征及混合状态等进行了全面观测和分析，并对两地颗粒物差异性进行了对比分析.结果发现：两地气溶胶颗粒主要包括有机物、富硫、矿物、烟尘和飞灰/金属颗粒，除了以单独的外混形式存在外，大多数颗粒以两种及两种以上颗粒类型混合（即内混）形式存在.通过对成都市不同污染状况下单颗粒特征对比发现，"污染天"的内混颗粒占比高于"清洁天"，分别为74.2%和68.6%；相比"清洁天"，"污染天"颗粒物粒径分布范围更广且峰值区间更大，表明污染过程中颗粒物的大气混合趋于更强.对比成都市与峨眉山分析结果得知，成都市以内混的有机物-硫颗粒为主导（占比为50.2%），而峨眉山以外混的有机物颗粒为主导（占比为50.5%）；成都市含硫类颗粒物（如有机物-硫颗粒）贡献高于峨眉山，而峨眉山两种含碳类颗粒（如烟尘和有机物-烟尘颗粒）占比高于成都市；此外，成都市与峨眉山两地大气颗粒物粒径分布范围及峰值区间均存在一定差异，进一步体现了两地颗粒物来源和老化混合的差异.在峨眉山，与非降雨天相比，一些易溶于水的颗粒物（如含硫类颗粒）在降雨天占比明显降低，而源自当地燃烧过程、粒径较小且疏水性强的颗粒物（如烟尘和有机物-烟尘颗粒）占比相应升高.

Characterization of individual aerosol particles with TEM-EDS in Sichuan Basin

To understand the physiochemical characteristics of individual aerosol particles in Sichuan Basin, samples of atmospheric individual aerosol particles were collected in a typical city (Chengdu) and a background area (Mt. Emei) in Sichuan Basin. Then the chemical composition, morphology and mixing state of 3923 aerosol particles in the two regions were observed and analyzed by transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (TEM-EDS). The results showed that the individual aerosol particles in the two regions mainly included organic matter, S-rich, mineral, soot and fly ash/metal particles. In addition to a small amount of external mixing, most particles existed in the form of internal mixing, i.e., two or more particles mixed with each other. Through the comparative of the characteristics of aerosol particles in different pollution conditions in Chengdu, it can be found that the proportion of the internal mixing particles in the "polluted days" (74.2%) was higher than that of "clean days" (68.6%). Moreover, compared with "clean days", the particles size distribution range of "pollution days" was wider and the peak range was larger, indicating that the mixing of particles tends to be stronger with the aggravation of pollution. The comparison between Chengdu and Mt. Emei showed that the OM-S particles dominated the particles in Chengdu (accounted for 50.2%), while the particles in Mt. Emei were dominated by OM particles (accounted for 50.5%). Meanwhile, the contribution of sulfur-containing particles (such as OM-S) in Chengdu was higher than that of Mt. Emei, while the proportion of two carbon-containing particles (such as soot and OM-soot) in Mt. Emei was higher than that of Chengdu. In addition, the range of particle size distribution and peak range between Chengdu and Mt. Emei were different, which highlighted the differences of the sources and aging mixture of particles between the two regions. In Mt. Emei, the proportion of soluble particles (such as sulfur-containing particles) in rainfall day significantly decreased compared with that of non-rainfall day, while the proportion of particles with small particle size and strong hydrophobicity (such as soot and OM-soot particles) increased correspondingly.