Size-fractionated water-soluble ions during autumn and winter: Insights into volatile ammonium formation mechanisms in Shanghai, a megacity of China
Size-fractionated water-soluble ions during autumn and winter: Insights into volatile ammonium formation mechanisms in Shanghai, a megacity of China
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秋冬季节水溶性离子的尺寸分级：中国大城市上海挥发性铵形成机制的见解
DOI：
10.1016/j.aeaoa.2019.100011
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发表时间：
2019-04
影响因子：
--
通讯作者：
Jianmin Chen
中科院分区：
文献类型：
--
作者：
Xingnan Ye;Ye Tao;Yuxuan Liu;Ruyu Wang;Qing Li;Xin Yang;Jianmin Chen
2014年秋冬季，利用微孔均匀存款撞击器在上海市区采集了不同粒径的气溶胶样品。结果表明，PM1.8的平均浓度从秋季的49 μ g m − 3上升到冬季的74 μ g m − 3。与此相反，水溶性无机物种的相对贡献从秋季的40%下降到冬季的31%。这一发现表明，有机质（OM）的增加，大大有助于在冬季颗粒物污染的恶化。与秋季相比，冬季大气细颗粒物中硫酸盐浓度降低，而NH4Cl浓度显著升高，成为细颗粒物的重要组成部分。当[NH4 +]/[SO42-]> 2时，秋季硝酸盐的生成显著，表明H2SO4被NH3完全中和，生成（NH4）2SO4。我们的结果表明，[NO3-]/[SO42-]和[NH4 +]/[SO42-]之间的回归得出了一个不切实际的硝酸盐形成机制，当颗粒NH4Cl丰富。在[NO3-]/[SO42-]和[NH4 +]/[SO42-]之间的回归中，用{[NO3-]+[Cl-]}代替[NO3-]，可以确定在冬季过量的有效NH3可以与HNO3和HCl反应生成NH4NO3和NH4Cl之前，（NH4）2SO4优先生成。大气颗粒物中硫酸盐和硝酸盐浓度与环境相对湿度的相关性不显著，表明湿颗粒物的非均相反应不是上海冬季灰霾形成的关键。我们的研究结果表明，需要更多的研究来了解中国复杂的雾霾形成机制。
Size-fractionated aerosols were collected by a Micro-Orifice Uniform Deposit Impactor at an urban site in Shanghai during the autumn and winter of 2014. The results showed that the average concentration of PM1.8increased from 49 μg m−3in autumn to 74 μg m−3in winter. By contrast, the relative contribution of the water-soluble inorganic species decreased from 40% in autumn to 31% in winter. This finding suggests that the increase of organic matter (OM) greatly contributed to the deterioration of particle pollution in winter. Compared to autumn, the concentration of sulfate decreased whereas the concentration of NH4Cl increased significantly and became an important constituent of the fine particles in winter. The formation of nitrate in autumn became significant at [NH4+]/[SO42−] > 2, indicating that H2SO4was fully neutralized by NH3to form (NH4)2SO4. Our results showed that the regression between [NO3−]/[SO42−] and [NH4+]/[SO42−] drawn an unrealistic nitrate formation mechanism when the particulate NH4Cl was abundant. Replacing [NO3−] with {[NO3−]+[Cl−]} in the regression between [NO3−]/[SO42−] and [NH4+]/[SO42−], it is established that (NH4)2SO4is preferentially formed before the excess available NH3can react with HNO3and HCl to form NH4NO3and NH4Cl during wintertime. The concentrations of particulate sulfate and nitrate were not positively correlated with the ambient relative humidity, indicating that heterogeneous reactions on wet particles were not the key to haze formation in Shanghai during winter. Our results suggest that more studies are needed to understand the complex haze formation mechanisms in China.
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影响因子：
4.4
作者：
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