Characterization of the number and chemical size distribution as well as hygroscopicity of fine and ultrafine particles in Beijing, China
Final Report Abstract
Number size distributions measured in Beijing show strong variations. Beside heavy pollution events also new particle formation has been found frequently. The growth rates are usually smaller, the nucleation rates higher than results from e.g. European sites indicate. The median PM1 mass concentration was 90 μg m-3. Days with low PM1 values were connected with air masses coming from the northwest, those with high PM1 are connected with air which spent the last 24 hours between south and west of Beijing. Clean air masses move in general much faster than polluted air. Size dependent hygroscopic properties of the urban submicrometer aerosol in Beijing show that the aerosol population could be divided into three groups concerning its hygroscopic behaviour, namely nearly hydrophobic, less hygroscopic and more hygroscopic. It turned out, that growth factors for less and more hygroscopic particles in the range smaller than Dp = 100 nm in dry diameter were slightly smaller than those found in urban environments in European or other Asian studies. These differences were assumed to be due to the high relative mass fractions of carbonaceous material which was also confirmed by chemical analysis. Hydrophobie particle fractions decreased with the level of pollution showing, that the urban aerosol in Beijing was highly influenced by aged air masses during polluted periods indicating sulfate as a main component of the observed aerosol in the accumulation mode range. Particle mass concentration mean values for PM18 were found to be about 170 μg m-3 in summer and winter. Maximum values of about 350 μg m-3 were also similar in both seasons. There was no significant difference of seasonal mean values. Nevertheless, events with northerly origin of air mass showed lower concentrations than events with southerly origin independent of the season. All events remaining under the PM10 EU limit of 50 μg m-3 had northerly air mass origin. The maximum size range for mass was shifting from Dpaer = 1.0-1.8 μm in summer to 0.32- 0.56 μm in winter. This is valid also for sulfate, nitrate, and ammonium. Particulate carbon concentration (TC) mean value difference between summer and winter was not significant. The same is true for OC and EC. In contrast, events with northerly air mass origin had significant lower TC concentrations than those with southerly origin independent of the season. In fact, the origin of air mass had more influence on the particulate carbon content than the season. Nonpolar organic compounds like alkanes and PAHs were detected. The sum of alkanes for PMig in winter samples was about ten times higher than in summer. During summer, maximum was observed in coarse mode particles (re-suspension of road dust, biogenic origin), during winter anthropogenic sources (domestic heating) were dominant. Summer and winter patterns for PAHs were similar, but concentrations in winter were 30 times higher. This could be a result of numerous domestic coal heating stoves as well as coal power plants. Long range transports from other industrialized areas may also contribute to the huge difference.
Publications
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Variations and Characteristics of Fine and Ultrafine Particle Number Size Distributions in the Urban Atmosphere of Beijing. PhD thesis (Chinese), 171 pages
Wu Zhijun
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2004. Aerosol number size distribution measurements in Beijing, China. AGU 2004 Fall Meeting, San Francisco, CA, USA, 13-17 December
Wehner, B., T. Tuch, A. Wiedensohler, Z. J. Wu, M Hu, M. Shao, and C. S. Kiang
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2004. Aerosol number size distribution measurements in Beijing, China. European Aerosol Conference (EAC), Budapest, Hungary, 6-10 September
Wehner, B., A. Massling, T. Tuch, Z. J. Wu, S. Liu, M. Hu, and A. Wiedensohler
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2004. Variability of the aerosol number size distribution in Beijing, China: New particle formation, dust storms, and high continental background. Geophys. Res. Lett., 31, L22108
Wehner, B., A. Wiedensohler, T. Tuch, Z. J. Wu, M. Hu, J. Slanina, and C. S. Kiang
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2005. Characteristics of fine and ultrafine particles in Beijing. SINO-GERMAN Workshop "Global change, urbanisation and health", Beijing, China
Hu, M., L. He, X. Huang, Z. Wu, B. Wehner, A. Wiedensohler
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2005. Episodes of high pollution in Beijing, China. European Aerosol Conference (EAC), Ghent, Belgium, 28 August - 2 September, pp. 719
Wehner, B., Z. Wu, S. Liu, Y. Cheng, J. Meier, M. Hu, and A. Wiedensohler
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2005. New particle formation in Beijing, China. European Aerosol Conference (EAC), Ghent, Belgium, 28 August - 2 September, pp. 99
Wehner, B., Wu, Z., Bauer, S., Hu, M. and Wiedensohler, A.
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2005. Size-segregated determination of growth factors and number fractions of different hygroscopic particle groups in the urban submicrometer Beijing aerosol. European Aerosol Conference (EAC), Ghent, Belgium, 28 August - 2 September, p. 40
Massling, A., M. Stock, B. Wehner, T. Tuch, Z. Wu, M. Hu, and A. Wiedensohler
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(2006) Volume size distributions of soluble particle matter of the aerosol in Beijing. 7th International Aerosol Conference, pp. 1751 - 1752
Massling, A., Stock, M., Wehner, B., Tuch, T., Wu, Z., Hu, M., Brüggemann, E., Gnauk, T., Herrmann, H., Wiedensohler, A.
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2006. Aerosol particles in the developing world; a comparison between New Delhi in India and Beijing in China. Water Air Soil Poll., 775, 5-20
Laakso, L., I. K. Koponen, P. Mönkkönen, M. Kulmala, V.-M. Kerminen, B. Wehner, A. Wiedensohler, Z. Wu, and M. Hu
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2006. Formation and growth of ultrafine particles in Beijing, China. 7th International Aerosol Conference, American Association for Aerosol Research (AAAR), St. Paul, Minnesota, USA, 10-15 September, pp. 1609-1610
Wehner, B., S. Bauer, Z. Wu, M. Hu, M. Dal Maso, T. Petäjä, M. Kulmala, W. Birmili, and A. Wiedensohler
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Effects of high temperature high relative humidity and rain process on particle size distributions in the summer of Beijing. 2006, Environmental Science, Vol. 27 (11) 2293-2299 In Chinese and English abstract
Hu, M., Liu S., Wu Z., Zhang J., Zhao Y., Wehner B., Wiedensohler A.
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2007. New particle formation in the mega-city: Beijing, China. J. Geophys. Res., 112(D09209)
Wu, Z., M. Hu, S. Liu, B. Wehner, S. Bauer, A. Wiedensohler, T. Petäjä, M. Dal Maso, M. Kulmala
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Features of particle number size distributions during heavy polluted episodes in Beijing. 2007, The 10th international conference on atmospheric sciences and applications to air quality, p 199
Wu, Z., M. Hu, B. Wehner, A. Wiedensohler
