The water-soluble ionic composition of PM2.5 in Shanghai and Beijing, China

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal

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Author(s)

  • Xiaohong Yao
  • Ming Fang
  • Steven Cadle
  • Tai Chan
  • Patricia Mulawa
  • Kebin He
  • Boming Ye

Detail(s)

Original languageEnglish
Pages (from-to)4223-4234
Journal / PublicationAtmospheric Environment
Volume36
Issue number26
Publication statusPublished - Sep 2002
Externally publishedYes

Abstract

A year-long field study to characterize the ionic species in PM2.5 was carried out in Shanghai and Beijing, China, in 1999-2000. Weekly samples of PM2.5 were collected using a special low flow rate (0.4lmin-1) sampler. In Shanghai, SO4 2- NO3 - and NH4 + were the dominant ionic species, which accounted for 46%, 18% and 17% of the total mass of ions, respectively. Local SO2 emissions were an important source of SO4 2- in PM2.5 because the SO4 2- concentration was correlated with the SO2 concentration (r=0.66). The relatively stable SO4 2-/SO2 mass ratio over a large range of temperatures suggests that gas-phase oxidation of SO2 played a minor role in the formation of SO4 2-. The sum of SO4 2- and NO3 - was highly correlated with NH4 + (r=0.96), but insufficient ammonium was present to totally neutralize the aerosol. In Beijing, SO4 2-, NO3 - and NH4 + were also the dominant ionic species, constituting 44%, 25% and 16% of the total mass of water-soluble ions, respectively. Local SO2 emissions were an important source of SO4 2- in the winter since SO4 2- was correlated with SO2 (r=0.83). The low-mass SO4 2-/SO2 ratio (0.27) during winter, which had low humidity, suggests that gas-phase oxidation of SO2 was a major route of sulfate formation. In the summer, however, much higher mass ratios of SO4 2-/SO2 (5.6) were observed and were ascribed to in-cloud sulfate formation. The annual average ratio of NO3 -/SO4 2- was 0.4 and 0.6 in Shanghai and in Beijing, respectively, suggesting that stationary emissions were still a dominant source in these two cities. Copyright © 2002 Elsevier Science Ltd.

Research Area(s)

  • Correlation analysis, Dicarboxylic acids, Nitrate, Seasonal variation, Sulfate

Citation Format(s)

The water-soluble ionic composition of PM2.5 in Shanghai and Beijing, China. / Yao, Xiaohong; Chan, Chak K.; Fang, Ming; Cadle, Steven; Chan, Tai; Mulawa, Patricia; He, Kebin; Ye, Boming.

In: Atmospheric Environment, Vol. 36, No. 26, 09.2002, p. 4223-4234.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal