Abstract
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.
Highlights
China, as the world’s second largest economy, is facing severe air pollution problems due to its rapid economic growth
Previous studies have shown that high particulate matter (PM) concentrations usually correspond to southerly winds, while low PM concentration are generally related to northerly winds, because there were more high-concentration air pollutants from source locations south of the Beijing area (Wehner et al, 2008; Wang et al, 2010; Gao et al, 2011)
When emission control measures were in place, particles became more hydrophobic and volatile compared to particles in the non-control period
Summary
As the world’s second largest economy, is facing severe air pollution problems due to its rapid economic growth. This has led to highly elevated aerosol concentrations, especially in urban regions such as Beijing, Shanghai, and Guangzhou (Hsu et al, 2012; Huang et al, 2014). Y. Wang et al.: Enhanced hydrophobicity and volatility of submicron aerosols health hazard and changes in the regional climate because of aerosol direct and indirect climate effects The pollution formation mechanism and the climate effects of aerosols remain highly uncertain due to the highly variable physical and chemical properties of aerosols, as well as complex mechanisms that govern aerosol–climate interactions (Tao et al, 2012; Wang et al, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
