Enhanced hydrophobicity and volatility of submicron aerosols under severe emission control conditions in Beijing
Enhanced hydrophobicity and volatility of submicron aerosols under severe emission control conditions in Beijing
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北京严格排放控制条件下亚微米气溶胶疏水性和挥发性增强
DOI：
10.5194/acp-17-5239-2017
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发表时间：
2017-04
影响因子：
6.3
通讯作者：
Sun Yele
中科院分区：
文献类型：
--
作者：
Wang Yuying;Zhang Fang;Li Zhanqing;Tan Haobo;Xu Hanbing;Ren Jingye;Zhao Jian;Du Wei;Sun Yele
摘要。在2015年中国胜利日阅兵期间，北京及周边七省实施了一系列严格的排放控制措施，以确保良好的空气质量，这为研究气溶胶特性的人为影响提供了一个独特的机会。使用吸湿性和挥发性串联差分迁移率分析仪（H/V-TDMA）系统在控制期间和之后测量亚微米气溶胶的吸湿性和挥发性。选取控制洁净期（Clean1）、非控制洁净期（Clean2）和非控制污染期（pollution）三个时段，研究排放控制措施对气溶胶吸湿性和挥发性的影响。由于排放控制措施，气溶胶颗粒的疏水性和挥发性变得更强。相对于Clean2, 40-200 nm颗粒的吸湿系数（κ）在Clean1期间降低了32.0 ~ 8.5 %，40-300 nm颗粒的挥发性收缩系数（SF）降低了7.5 ~ 10.5 %。排放控制还改变了κ (κ- pdf)概率密度函数和SF （SF- pdf）概率密度函数的日变化规律。在Clean1期间，κ-PDF在成核模式下表现出一种近乎疏水（NH）模式，这可能是由于无机微量气体的工业排放急剧减少。与污染期相比，在Clean1和Clean2期间观察到的颗粒全天表现出更显著的非挥发性（NV）模式，这表明150 nm颗粒的外部混合状态更为明显。气溶胶吸湿性随颗粒大小的增加而增加，在污染期间增幅最大。因此，在Clean1和Clean2时期，随着粒径的增大，气溶胶的挥发性变弱（即SF增大），但在Pollution时期没有明显的趋势。通过对NH和NV颗粒数量分数的相关性分析，发现在排放控制期内，疏水性和挥发性颗粒的数量分数较高。
Abstract. A series of strict emission control measures was implemented in Beijing and the surrounding seven provinces to ensure good air quality during the 2015 China Victory Day parade, rendering a unique opportunity to investigate the anthropogenic impact of aerosol properties. Submicron aerosol hygroscopicity and volatility were measured during and after the control period using a hygroscopic and volatile tandem differential mobility analyzer (H/V-TDMA) system. Three periods, namely the control clean period (Clean1), the non-control clean period (Clean2), and the non-control pollution period (Pollution), were selected to study the effect of the emission control measures on aerosol hygroscopicity and volatility. Aerosol particles became more hydrophobic and volatile due to the emission control measures. The hygroscopicity parameter (κ) of 40–200 nm particles decreased by 32.0–8.5 % during the Clean1 period relative to the Clean2 period, while the volatile shrink factor (SF) of 40–300 nm particles decreased by 7.5–10.5 %. The emission controls also changed the diurnal variation patterns of both the probability density function of κ (κ-PDF) and the probability density function of SF (SF-PDF). During Clean1 the κ-PDF showed one nearly hydrophobic (NH) mode for particles in the nucleation mode, which was likely due to the dramatic reduction in industrial emissions of inorganic trace gases. Compared to the Pollution period, particles observed during the Clean1 and Clean2 periods exhibited a more significant nonvolatile (NV) mode throughout the day, suggesting a more externally mixed state particularly for the 150 nm particles. Aerosol hygroscopicities increased as particle sizes increased, with the greatest increases seen during the Pollution period. Accordingly, the aerosol volatility became weaker (i.e., SF increased) as particle sizes increased during the Clean1 and Clean2 periods, but no apparent trend was observed during the Pollution period. Based on a correlation analysis of the number fractions of NH and NV particles, we found that a higher number fraction of hydrophobic and volatile particles during the emission control period.
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作者：
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DOI：
10.1021/jp407991n
发表时间：
2013-12
期刊：
The journal of physical chemistry. A
影响因子：
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作者：
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通讯作者：
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影响因子：
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通讯作者：
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