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Cloud Condensation Nuclei (Ccn) from Fresh and Aged Air Pollution in the Megacity Region of Beijing : Volume 11, Issue 3 (25/03/2011)

By Gunthe, S. S.

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Book Id: WPLBN0003996022
Format Type: PDF Article :
File Size: Pages 39
Reproduction Date: 2015

Title: Cloud Condensation Nuclei (Ccn) from Fresh and Aged Air Pollution in the Megacity Region of Beijing : Volume 11, Issue 3 (25/03/2011)  
Author: Gunthe, S. S.
Volume: Vol. 11, Issue 3
Language: English
Subject: Science, Atmospheric, Chemistry
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Historic
Publication Date:
2011
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

Citation

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Rose, D., Achtert, P., Zhu, T., Nowak, A., Pöschl, U., Kondo, Y.,...Shao, M. (2011). Cloud Condensation Nuclei (Ccn) from Fresh and Aged Air Pollution in the Megacity Region of Beijing : Volume 11, Issue 3 (25/03/2011). Retrieved from http://www.ebooklibrary.org/


Description
Description: Biogeochemistry Department, Max Planck Institute for Chemistry, Mainz, Germany. Atmospheric aerosol particles serving as cloud condensation nuclei (CCN) are key elements of the hydrological cycle and climate. CCN properties were measured and characterized during the CAREBeijing-2006 campaign at a regional site south of the megacity of Beijing, China. Size-resolved CCN efficiency spectra recorded for a supersaturation range of S = 0.07% to 0.86% yielded average activation diameters in the range of 190 nm to 45 nm. The corresponding effective hygroscopicity parameters (Κ) exhibited a strong size dependence ranging from ~0.25 in the Aitken size range to ~0.45 in the accumulation size range. The campaign average value (Κ = 0.3 ± 0.1) was similar to the values observed and modeled for other populated continental regions.

The hygroscopicity parameters derived from the CCN measurements were consistent with chemical composition data recorded by an aerosol mass spectrometer (AMS) and thermo-optical measurements of apparent elemental and organic carbon (ECa and OC). The CCN hygroscopicity and its size dependence could be parameterized as a function of AMS based organic and inorganic mass fractions using the simple mixing rule Κ p ≈ 0.1 · forg + 0.7 · finorg.

When the measured air masses originated from the north and passed rapidly over the center of Beijing (fresh city pollution), the average particle hygroscopicity was reduced (Κ = 0.2 ± 0.1), which is consistent with enhanced mass fractions of organic compounds (~50%) and ECa (~30%) in the fine particulate matter (PM1). Moreover, substantial fractions of externally mixed weakly CCN-active particles were observed at low supersaturation (S = 0.07%), which can be explained by the presence of freshly emitted soot particles with very low hygroscopicity (Κ<0.1). Particles in stagnant air from the industrialized region south of Beijing (aged regional pollution) were on average larger and more hygroscopic, which is consistent with enhanced mass fractions (~60%) of soluble inorganic ions (mostly sulfate, ammonium, and nitrate). Accordingly, the number concentration of CCN in aged air from the megacity region was higher than in fresh city outflow ((2.5–9.9) × 103 cm−3 vs. (0.4–8.3) × 103 cm−3) although the total aerosol particle number concentration was lower (1.2 × 104 cm−3 vs. 2.3 × 104 cm−3). A comparison with related studies suggests that the fresh outflow from Chinese urban centers generally may contain more, but smaller and less hygroscopic aerosol particles and thus fewer CCN than the aged outflow from megacity regions.


Summary
Cloud condensation nuclei (CCN) from fresh and aged air pollution in the megacity region of Beijing

Excerpt
Achtert, P., Birmili, W., Nowak, A., Wehner, B., Wiedensohler, A., Takegawa, N., Kondo, Y., Miyazaki, Y., Hu, M., and Zhu, T.: Hygroscopic growth of tropospheric particle number size distributions over the North China Plain, J. Geophys. Res., 114, D00G07, doi:10.1029/2008JD010921, 2009.; Andreae, M. O., Jones, C. D., and Cox, P. M.: Strong present-day aerosol cooling implies a hot future, Nature, 435, 1187–1190, 2005.; Andreae, M. O.: Correlation between cloud condensation nuclei concentration and aerosol optical thickness in remote and polluted regions, Atmos. Chem. Phys., 9, 543–556, doi:10.5194/acp-9-543-2009, 2009.; Andreae, M. O. and Rosenfeld, D.: Aerosol-cloud-precipitation interactions. Part 1. The nature and sources of cloud-active aerosols, Earth-Sci. Rev., 89, 13–41, 2008.; Andreae, M. O. and Gelencsér, A.: Black carbon or brown carbon? The nature of light-absorbing carbonaceous aerosols, Atmos. Chem. Phys., 6, 3131–3148, doi:10.5194/acp-6-3131-2006, 2006.; Birmili, W., Stratmann, F., and Wiedensohler, A.: Design of a DMA-based size spectrometer for a large particle size range and stable operation, J. Aerosol Sci., 30(4), 549–553, 1999.; Chang, R. Y.-W., Slowik, J. G., Shantz, N. C., Vlasenko, A., Liggio, J., Sjostedt, S. J., Leaitch, W. R., and Abbatt, J. P. D.: The hygroscopicity parameter ($\kappa $) of ambient organic aerosol at a field site subject to biogenic and anthropogenic influences: relationship to degree of aerosol oxidation, Atmos. Chem. Phys., 10, 5047–5064, doi:10.5194/acp-10-5047-2010, 2010.; Chen, D. S., Cheng, S. Y., Liu, L., Chen, T., and Guo, X. R.: An integrated MM5-CMAQ modeling approach for assessing trans-boundary PM10 contribution to the host city of 2008 Olympic summer games – Beijing, China, Atmos. Environ., 41, 6, 1237-1250, doi:10.1016/j.atmosenv.2006.09.045, 2007.; Cheng, Y. F., Berghof, M., Garland, R. M., Wiedensohler, A., Wehner, B., Müller, T., Su, H., Zhang, Y. H., Achtert, P., Nowak, A., Pöschl, U., Zhu, T., Hu, M., and Zeng, L. M.: Influence of soot mixing state on aerosol light absorption and single scattering albedo during air mass aging at a polluted regional site in Northeastern China, J. Geophys. Res., 114, D00G10, doi:10.1029/2008JD010883, 2009.; DeCarlo, P. F., Slowik, J. G., Worsnop, D. R., Davidovits, P., and Jimenez, J. L.: Particle morphology and density characterization by combined mobility and aerodynamic diameter measurements. Part 1: Theory, Aerosol Sci. Tech., 38(12), 1185–1205, 2004.; Deng, Z. Z., Zhao, C. S., Ma, N., Liu, P. F., Ran, L., Xu, W. Y., Chen, J., Liang, Z., Liang, S., Huang, M. Y., Ma, X. C., Zhang, Q., Quan, J. N., Yan, P., Henning, S., Mildenberger, K., Sommerhage, E., Schäfer, M., Stratmann, F., and Wiedensohler, A.: Size-

 

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