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Chemical Composition of PM2.5 and its Impact on Visibility in Guangzhou, Southern China

Category: Aerosol and Atmospheric Chemistry

Volume: 16 | Issue: 10 | Pages: 2349-2361
DOI: 10.4209/aaqr.2016.02.0059
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Weihua Chen1, Xuemei Wang 2, Shengzhen Zhou 2, Jason Blake Cohen2, Jinpu Zhang3, Yu Wang4, Ming Chang1, Yanjun Zeng3, Yexin Liu3, Zhenhao Ling2, Guixiong Liang3, Xiaonuan Qiu3

  • 1 School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510085, China
  • 2 School of Atmospheric Sciences, Sun Yat-Sen University, Guangzhou 510085, China
  • 3 Guangdong Environmental Monitoring Center, Guangzhou 510030, China
  • 4 Guangzhou Environmental Monitoring Center, Guangzhou 510030, China

Highlights

One-year field experiment was conducted for PM2.5 composition in Guangzhou.
50 µg m–3 of PM2.5 was a threshold for visibility lower than 10 km.
Hygroscopic properties of OC and EC were took into consideration.
Ions and OM with nitrate were more important under heavily polluted conditions.


Abstract

A one-year field experiment was conducted in 2013 at an urban and suburban site in Guangzhou, Southern China to study the chemical compositions of PM2.5 and reconstruct the IMPROVE Algorithm to investigate the impact of aerosol components on visibility. Annual average PM2.5 mass concentration was 61.3 ± 27.6 and 54.2 ± 29.7 µg m–3 at the urban and suburban site, with organic matter (OM), sulfate (SO42–), and nitrate (NO3) among the dominant components, accounting for 40.3%, 16.3%, and 8.0% of the PM2.5 mass concentration respectively. Based on the modified IMPROVE Algorithm, the localized Mass Scattering Efficiencies (MSE) for sulfate and nitrate was obtained, with values of 2.16 ± 0.34 m2 g–1 and 2.63 ± 0.66 m2 g–1 at urban site and 2.22 ± 0.31 m2 g–1 and 2.76 ± 0.84 m2 g–1 at suburban site. Hygroscopic growth factors (Gf) for OM and EC were also taken into consideration with average values of 1.28 ± 0.13 m2 g–1 and 1.15 ± 0.11 m2 g–1 at the urban site and 1.18 ± 0.09 m2 g–1 and 1.10 ± 0.09 m2 g–1 at the suburban site. The estimated total light extinction coefficient was 294.7 ± 106.9 and 255.8 ± 119.0 Mm–1 at the urban and suburban site, with OM, SO42– and NO3 contributing 41.7%, 16.5% and 11.5% at the urban site, and 42.1%, 21.3% and 9.1% at the suburban site. Secondary water-soluble ions and OM as a whole was becoming increasingly vital under polluted conditions, with nitrate in particular being more important under heavily polluted conditions in Guangzhou.

Keywords

Chemical composition Visibility Light extinction coefficient IMPROVE Hygroscopic growth factor


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