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Variation of PM2.5 Chemical Compositions and their Contributions to Light Extinctions in Seoul

Category: Aerosol and Atmospheric Chemistry

Accepted Manuscripts
DOI: 10.4209/aaqr.2017.10.0369
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Seung-Myung Park1,2, In-Ho Song1, Jong Sung Park1, Jun Oh1,2, Kwang Joo Moon1, Hea Jung Shin1, Jun Young Ahn1, Min-Do Lee1, Jeonghwan Kim2, Gangwoong Lee 2

  • 1 Air Quality Research Division, National Institute of Environmental Research, Seo, Incheon 22689, Korea
  • 2 Department of Environmental Science, Hankuk University of Foreign Studies, Yongin, Gyeonggi 17035, Korea

Highlights

One-year measurement of aerosol chemical and optical properties was made in Seoul.
Aerosol light scattering and absorption extinction were 132.2 Mm–1 and 57.5 Mm–1.
The most dominant species for light extinction were OM and EC.
Current IMPROVE scheme underestimated aerosol light extinction by 30%.
Underestimation was mainly attributed to fresh OM and EC in urban conditions.


Abstract

The objective of this study was to determine comprehensive chemical components in PM2.5 from March 2011 to February 2012 in Seoul, South Korea and their contributions to light extinctions. Major chemical components in aerosol were: ammonium sulfate, 30.3%; ammonium nitrate, 25.2%; organic matter, 21.3%; crustal mass, 16.9%; element carbon, 6.1%; and trace metals, 0.2%. PM2.5 mass concentrations and light extinctions were mostly correlated in their diurnal and monthly variations, which indicated that aerosol mass was the key variable for light extinctions in Seoul. However, aerosol size and compositions (of PM2.5) also played significant roles in light extinctions. We applied IMPROVE algorithm to quantify the contribution of observed chemical components to light extinctions. It was found that IMPROVE formula tended to underestimate light extinctions up to 30% in urban conditions where large sources of organic matter (OM) and element carbon (EC) existed, unless any revision were made before the light extinction calculations. IMPROVE algorithm was further optimized for observed light extinctions for OM and EC. Revised light extinction efficiencies of OM and EC in Seoul were increased about 1.5–3 times higher than those in original IMPROVE algorithm. Optimized IMPROVE scheme in this study reproduced the observed light extinctions more accurately in Seoul. Overall 41% contributions of OM and EC to light extinctions in Seoul were close to 50% of nitrate and sulfate contribution although the former mass contributions were only half of latter.

Keywords

PM2.5 Visibility Light extinction OM EC


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