Characteristics of summertime PM2.5 organic and elemental carbon in four major Chinese cities: Implications of high acidity for water-soluble organic carbon (WSOC)

Ravi Kant Pathak, Tao Wang, K. F. Ho, S. C. Lee

Research output: Journal article publicationJournal articleAcademic researchpeer-review

139 Citations (Scopus)


Although laboratory studies suggest that aerosol acidity ([H+]) significantly enhances the production of secondary organic aerosol (SOA) through heterogeneous chemistry, field studies have provided limited evidence of such enhancement. In this study, correlation of strong aerosol acidity with WSOC was investigated using the 24-hr PM2.5samples collected at sites near four major cities of China - Beijing (BJ), Shanghai (SH), Lanzhou (LZ), and Guangzhou (GZ) - during the summers of 2004-2006. PM2.5samples were characterized by high atmospheric loadings of PM2.5, OC, EC, sulfate, nitrate, aerosol acidity, and aerosol-water, especially in Beijing and Shanghai. On average, OC and EC were distributed in the ratio of approximately 2:1 among carbonaceous aerosols (TC = OC + EC) in all four cities. However, the WSOC fraction in OC differed across the four cities (BJ ∼ 55% of OC; SH ∼ 35%; LZ ∼ 40%; GZ ∼ 32%). We found an increased WSOC content in organic carbon (OC) fraction in the samples with elevated aerosol acidity (H+) and the WSOC was thought to be influenced by aerosol acidity. The WSOC/OC ratio showed a strong positive correlation with the normalized strong acid concentration ([H+]/[OC]) in the four cities. The higher WSOC fraction in OC at higher strong acidity is postulated to be linked to the conversion of OC to WSOC via heterogeneous acid-catalyzed chemistry.
Original languageEnglish
Pages (from-to)318-325
Number of pages8
JournalAtmospheric Environment
Issue number2
Publication statusPublished - 1 Jan 2011


  • Acid catalyzed reaction
  • Acidity
  • EC
  • OC
  • SOA
  • WSOC

ASJC Scopus subject areas

  • Environmental Science(all)
  • Atmospheric Science

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