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Volume 14, No. 1, February 2014, Pages 260-268 PDF(649 KB)  
doi: 10.4209/aaqr.2012.12.0360   

Impact of Relative Humidity and Water Soluble Constituents of PM2.5 on Visibility Impairment in Beijing, China

Jing Chen1, Shasha Qiu2, Jing Shang1, Ossima M.F. Wilfrid1, Xingang Liu1, Hezhong Tian1, Johan Boman2

1 State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China
2 Department of Chemistry and Molecular Biology, Division of Atmospheric Science, University of Gothenburg, SE 41296 Göteborg, Sweden




Beijing has been experiencing severe particulate pollution accompanying the fast growing population and economy. This study investigated the impact of PM2.5 and its water soluble organic and inorganic constituents on visual impairment in Beijing under different meteorological conditions. According to the analysis of PM2.5 samples collected in Spring 2012, water soluble species took up 38.1% of PM2.5 mass, among which NO3 was the most abundant constituent, followed by SO42–, NH4+ and water soluble organic matter. The correlation analysis between visibility and aerosol loadings as well as meteorological parameters revealed the dominant impact of meteorological conditions, relative humidity in particular, on visibility impairment over the mass concentration of PM2.5. Compared to the total aerosol loading of PM2.5, visibility was better correlated with the total mass of water soluble constituents (WSC). The visual range in Beijing was the most sensitive to both WSC and PM2.5 in the RH range of 30–70%. Severe visual impairment was observed for RH ≥ 70% with the least sensitivity to WSC and PM2.5. The effects of synoptic scale circulation on meteorological variables that affect air quality were also examined with the movement of a cold front as a case study. The findings have direct implications to region-wide policy-making and control strategies.



Keywords: Visibility impairment; Water soluble ion; Water soluble organic carbon; Hygroscopic growth; Synoptic circulation.



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