Atmos. Chem. Phys. Discuss., 10, 14611-14637, 2010
www.atmos-chem-phys-discuss.net/10/14611/2010/
doi:10.5194/acpd-10-14611-2010
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Variation of particle number size distributions and chemical compositions at the urban and downwind regional sites in the Pearl River Delta during summertime pollution episodes
D. L. Yue1, M. Hu1, Z. J. Wu1,2, S. Guo1, M. T. Wen1, A. Nowak2, B. Wehner2, A. Wiedensohler2, N. Takegawa3, Y. Kondo3, X. S. Wang1, Y. P. Li1, L. M. Zeng1, and Y. H. Zhang1
1State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China
2Leibniz Institute for Tropospheric Research, Permoserstrasse 15, 04318 Leipzig, Germany
3Research Center for Advanced Science and Technology, University of Tokyo, Tokyo 153-8904, Japan

Abstract. In order to characterize the features of particulate pollution in the Pearl River Delta (PRD) in the summer, continuous measurements of particle number size distributions and chemical compositions were simultaneously performed at Guangzhou urban site (GZ) and Back-garden downwind regional site (BG) in July 2006. Particle number concentration from 20 nm to 10 μm at BG was (1.7±0.8)×104 cm−3, about 40% lower than that at GZ, (2.9±1.1)×104 cm−3 with intensive traffic emissions. The total particle volume concentration at BG was 94±34 μm3 cm−3, similar to that at GZ, 96±43 μm3 cm−3. More 20–100 nm particles, significantly affected by the traffic emissions, were observed at GZ, while 100–660 nm particle number concentrations were similar at both sites as they are more regional. PM2.5 values were also similar at GZ (69±43 μg m−3) and BG (69±58 μg m−3), indicating the fine particulate pollution in the PRD region to be regional. Two kinds of pollution episodes, the accumulation pollution episode and the regional transport pollution episode, were observed. Fine particles over 100 nm dominated both number and volume concentrations of total particles during the late periods of these pollution episodes. Accumulation and secondary transformations are two main reasons for the nighttime accumulation pollution episode. SO4−2, NO3, and NH4+ accounted for about 60% in 100–660 nm particle mass and PM2.5. When south or south-southeast wind prevailed in the PRD region, regional transport of pollutants takes place. Regional transport contributed about 30% to fine particulate pollution at BG during a regional transport case. Secondary transformation played an important role during regional transport, causing higher increase rates of secondary ions in PM1.0 than other species and shifting the peaks of sulfate and ammonium mass size distributions to larger sizes. SO4−2, NO3, and NH4+ accounted for about 70% and 40% of PM1.0 and PM2.5, respectively.

Citation: Yue, D. L., Hu, M., Wu, Z. J., Guo, S., Wen, M. T., Nowak, A., Wehner, B., Wiedensohler, A., Takegawa, N., Kondo, Y., Wang, X. S., Li, Y. P., Zeng, L. M., and Zhang, Y. H.: Variation of particle number size distributions and chemical compositions at the urban and downwind regional sites in the Pearl River Delta during summertime pollution episodes, Atmos. Chem. Phys. Discuss., 10, 14611-14637, doi:10.5194/acpd-10-14611-2010, 2010.
 
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