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Aerosol radiative, physical, and chemical properties in Beijing during June 1999

Bergin, M. H. and Cass, G. R. and Xu, J. and Fang, C. and Zeng, L. M. and Yu, T. and Salmon, L. G. and Kiang, C. S. and Tang, X. Y. and Zhang, Y. H. and Chameides, W. L. (2001) Aerosol radiative, physical, and chemical properties in Beijing during June 1999. Journal of Geophysical Research D, 106 (D16). pp. 17969-17980. ISSN 0148-0227. doi:10.1029/2001JD900073.

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Beijing experiences air pollution such that the sky overhead is gray much of the time even on cloudless days. In order to understand the cause of this problem, the aerosol light scattering coefficient σ_(sp) and absorption coefficient σ_(ap) were measured under dry conditions (instrumental relative humidity <40%) during a 1-week intensive field sampling period in June 1999 in Beijing, China. Additional measurements included the aerosol mass size distribution, chemical composition of the aerosol mass having particle diameters less than 2.5 μm (PM2.5) as well as the chemical composition of the total suspended particulate matter. The mean (and standard deviation) for hourly averages of σ_(sp), σ_(ap), and the single-scattering albedo ω were 488 Mm^(−1) (370 Mm^(−1)), 83 Mm^(−1) (40 Mm^(−1)), and 0.81 (0.08), respectively, which is significantly higher than values reported in urban regions of the United States. The relatively high values of σ_(sp) were accompanied by a daily mean value for the PM2.5 mass concentration of 136 μg m^(−3) (48 μg m^(−3)), which is significantly higher than the proposed U.S. 24-hour average mean National Ambient Air Quality Standard of 65 μg m^(−3). The visual range during the field study, based on measurements of σ_(sp) and σ_(ap), was typically less than 6 km. For several days that did not have rain or fog, there was a clear diurnal trend in σ_(sp), σ_(ap), and ω, with peak values in the early morning and minima that occur in the evenings. The peaks correspond to minima in ambient temperature and maxima in relative humidity. Mass size distribution measurements indicate that although ∼80% of the aerosol mass was located in the coarse particle mode (D_p > 1.0 μm), the submicron aerosol was responsible for ∼80% of the light scattering at 530 nm. The largest contribution to the PM2.5 aerosol mass was due to organic compounds, which accounted for ∼30% of the mass. The contributions of sulfate, ammonium, and nitrate to the PM2.5 mass concentration were ∼15%, 5%, and 8%, respectively. Mineral aerosol contributed ∼16% to the PM2.5 aerosol mass. These data show that combustion-related particles rather than wind-blown dust dominated the light extinction budget during June 1999.

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Additional Information:Copyright 2001 by the American Geophysical Union. (Received October 12, 2000; accepted January 30, 2001.) Paper number 2001JD900073. We thank Judy Chow and Cliff Frazier of the Desert Research Institute for performing the X-ray fluorescence analyses of the airborne particle samples. We also thank Ted Russell at Georgia Tech for discussions related to aerosol nitrate formation.
Issue or Number:D16
Record Number:CaltechAUTHORS:20141027-132555424
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Official Citation:Bergin, M. H., et al. (2001), Aerosol radiative, physical, and chemical properties in Beijing during June 1999, J. Geophys. Res., 106(D16), 17969–17980, doi:10.1029/2001JD900073.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50865
Deposited By: George Porter
Deposited On:27 Oct 2014 20:47
Last Modified:10 Nov 2021 19:02

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