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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-1232
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
21 Feb 2018
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
Characteristics of PM2.5 mass concentrations and chemical species in urban and background areas of China: emerging results from the CARE-China network
Zirui Liu1, Wenkang Gao1, Yangchun Yu1, Bo Hu1, Jinyuan Xin1, Yang Sun1, Lili Wang1, Gehui Wang3, Xinhui Bi4, Guohua Zhang4, Honghui Xu5, Ziyuan Cong6, Jun He7, Jingsha Xu7, and Yuesi Wang1,2 1State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
2Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
3State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710075, China
4State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
5Zhejiang Meteorology Science Institute, Hangzhou 310017, China
6Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
7International Doctoral Innovation Centre, The University of Nottingham Ningbo China, Ningbo 315100, China
Abstract. The Campaign on atmospheric Aerosol REsearch network of China (CARE-China) is a long-term project for the study of the spatiotemporal distributions of physical aerosol characteristics as well as the chemical components and optical properties of aerosols over China. This study presents the first long-term datasets from this project, including three years of observations of online PM2.5 mass concentrations (2012–2014) and one year of observations of PM2.5 compositions (2012–2013) from the CARE-China network. The average PM2.5 concentrations at 20 urban sites is 73.2 μg/m3 (16.8–126.9 μg/m3), which was three times higher than the average value from the 12 background sites (11.2–46.5 μg/m3). The PM2.5 concentrations are generally higher in east-central China than in the other parts of the country due to their relative large particulate matter (PM) emissions and the unfavorable meteorological conditions for pollution dispersion. A distinct seasonal variability of the PM2.5 is observed, with highs in the winter and lows during the summer at urban sites. Inconsistent seasonal trends were observed at the background sites. Bimodal and unimodal diurnal variation patterns were identified at both urban and background sites. The chemical compositions of PM2.5 at six paired urban and background sites located within the most polluted urban agglomerations and cleanest regions of China were analyzed. The major PM2.5 constituents across all the urban sites are organic matter (OM, 26.0 %), SO42− (17.7 %), mineral dust (11.8 %), NO3 (9.8 %), NH4+ (6.6 %), elemental carbon (EC) (6.0 %), Cl (1.2 %) at 45 % RH and residual matter (20.7 %). Similar chemical compositions of PM2.5 were observed at background sites but were associated with higher fractions of OM (33.2 %) and lower fractions of NO3 (8.6 %) and EC (4.1 %). Significant variations of the chemical species were observed among the sites. At the urban sites, the OM ranged from 12.6 μg/m3 (Lhasa) to 23.3 μg/m3 (Shenyang), the SO42− ranged from 0.8 μg/m3 (Lhasa) to 19.7 μg/m3 (Chongqing), the NO3 ranged from 0.5 μg/m3 (Lhasa) to 11.9 μg/m3 (Shanghai) and the EC ranged from 1.4 μg/m3 (Lhasa) to 7.1 μg/m3 (Guangzhou). The PM2.5 chemical species at the background sites exhibited larger spatial heterogeneities than those at urban sites, suggesting the different contributions from regional anthropogenic or natural emissions and from the long-range transport to background areas. Notable seasonal variations of PM2.5 polluted days were observed, especially for the megacities in east-central China, resulting in frequent heavy pollution episodes occurring during the winter. The evolution of the PM2.5 chemical compositions on polluted days was similar for the urban and nearby background sites, suggesting the significant regional pollution characteristics of the most polluted areas of China. However, the chemical species dominating the evolutions of the heavily polluted events were different in these areas, indicating that unique mitigation measures should be developed for different regions of China. This analysis reveals the spatial and seasonal variabilities of the urban and background aerosol concentrations on a national scale and provides insights into their sources, processes, and lifetimes.
Citation: Liu, Z., Gao, W., Yu, Y., Hu, B., Xin, J., Sun, Y., Wang, L., Wang, G., Bi, X., Zhang, G., Xu, H., Cong, Z., He, J., Xu, J., and Wang, Y.: Characteristics of PM2.5 mass concentrations and chemical species in urban and background areas of China: emerging results from the CARE-China network, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-1232, in review, 2018.
Zirui Liu et al.

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Short summary
We have established a national-level network (CARE-China)) that conducted continuous monitoring of PM2.5 and its chemical compositions in China. Our analysis reveals the spatial and seasonal variabilities of the urban and background aerosol species and their contributions to the PM2.5 budget. The integration of data provided an extensive spatial coverage of fine particle concentrations and could be used to validate model results and implement effective air pollution control strategies.
We have established a national-level network (CARE-China)) that conducted continuous monitoring...
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