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High secondary aerosol contribution to particulate pollution during haze events in China


Rapid industrialization and urbanization in developing countries has led to an increase in air pollution, along a similar trajectory to that previously experienced by the developed nations1. In China, particulate pollution is a serious environmental problem that is influencing air quality, regional and global climates, and human health2,3. In response to the extremely severe and persistent haze pollution experienced by about 800 million people during the first quarter of 2013 (refs 4, 5), the Chinese State Council announced its aim to reduce concentrations of PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 micrometres) by up to 25 per cent relative to 2012 levels by 2017 (ref. 6). Such efforts however require elucidation of the factors governing the abundance and composition of PM2.5, which remain poorly constrained in China3,7,8. Here we combine a comprehensive set of novel and state-of-the-art offline analytical approaches and statistical techniques to investigate the chemical nature and sources of particulate matter at urban locations in Beijing, Shanghai, Guangzhou and Xi’an during January 2013. We find that the severe haze pollution event was driven to a large extent by secondary aerosol formation, which contributed 30–77 per cent and 44–71 per cent (average for all four cities) of PM2.5 and of organic aerosol, respectively. On average, the contribution of secondary organic aerosol (SOA) and secondary inorganic aerosol (SIA) are found to be of similar importance (SOA/SIA ratios range from 0.6 to 1.4). Our results suggest that, in addition to mitigating primary particulate emissions, reducing the emissions of secondary aerosol precursors from, for example, fossil fuel combustion and biomass burning is likely to be important for controlling China’s PM2.5 levels and for reducing the environmental, economic and health impacts resulting from particulate pollution.

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Figure 1: Chemical composition and source apportionment of PM2.5 collected during the high pollution events of 5–25 January 2013 at the urban sites of Beijing, Shanghai, Guangzhou and Xi’an.
Figure 2: Source contribution to total particulate and organic matter.
Figure 3: Fossil and non-fossil fractional contributions of each source during low and high PM2.5 levels observed in different cities.

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  1. Seinfeld, J. H. Air pollution: a half century of progress. Am. Inst. Chem. Eng. J. 50, 1096–1108 (2004)

    Article  CAS  Google Scholar 

  2. Wang, Y., Zhang, R. Y. & Saravanan, R. Asian pollution climatically modulates mid-latitude cyclones following hierarchical modeling and observational analysis. Nature Commun. 5, (2014)

  3. Cao, J. J. Pollution status and control strategies of PM2. 5 in China. J. Earth Environ. 3, 1030–1036 (2012)

    Google Scholar 

  4. China National Environmental Monitoring Centre. Air Quality Report in 74 Chinese Cities in March and the First Quarter 2013 ( (in Chinese), accessed on, 11 June 2013)

  5. Chen, R. J., Zhao, Z. H. & Kan, H. D. Heavy smog and hospital visits in Beijing, China. Am. J. Respir. Crit. Care Med. 188, 1170–1171 (2013)

    Article  Google Scholar 

  6. Chinese State Council. Atmospheric Pollution Prevention and Control Action Plan ( (in Chinese), accessed on, 12 September 2013)

  7. Zhang, Q., He, K. B. & Huo, H. Cleaning China’s air. Nature 484, 161–162 (2012)

    Article  ADS  CAS  Google Scholar 

  8. Yang, F. et al. Characteristics of PM2. 5 speciation in representative megacities and across China. Atmos. Chem. Phys. 11, 5207–5219 (2011)

    Article  ADS  CAS  Google Scholar 

  9. Wuebbles, D. J., Lei, H. & Lin, J. T. Intercontinental transport of aerosols and photochemical oxidants from Asia and its consequences. Environ. Pollut. 150, 65–84 (2007)

    Article  CAS  Google Scholar 

  10. Jimenez, J. L. et al. Evolution of organic aerosols in the atmosphere. Science 326, 1525–1529 (2009)

    Article  ADS  CAS  Google Scholar 

  11. Watson, J. G. et al. CMB8 Applications and Validation Protocol for PM2.5 and VOCs (US Environmental Protection Agency and Desert Research Institute, Reno, Nevada, 1998)

  12. Canonaco, F., Crippa, M., Slowik, J. G., Baltensperger, U. & Prévôt, A. S. H. SoFi, an IGOR-based interface for the efficient use of the generalized multilinear engine (ME-2) for source apportionment: ME-2 application to aerosol mass spectrometer data. Atmos. Meas. Tech. 6, 3649–3661 (2013)

    Article  Google Scholar 

  13. DeCarlo, P. F. et al. Field-deployable, high-resolution, time-of-flight aerosol mass spectrometer. Anal. Chem. 78, 8281–8289 (2006)

    Article  CAS  Google Scholar 

  14. Orasche, J., Schnelle-Kreis, J., Abbaszade, G. & Zimmermann, R. Technical note: in-situ derivatization thermal desorption GC-TOFMS for direct analysis of particle-bound non-polar and polar organic species. Atmos. Chem. Phys. 11, 8977–8993 (2011)

    Article  ADS  CAS  Google Scholar 

  15. Zhang, Y. L. et al. On the isolation of OC and EC and the optimal strategy of radiocarbon-based source apportionment of carbonaceous aerosols. Atmos. Chem. Phys. 12, 10841–10856 (2012)

    Article  ADS  CAS  Google Scholar 

  16. Cao, J. J. et al. On the potential high acid deposition in northeastern China. J. Geophys. Res. 118, 4834–4846 (2013)

    Google Scholar 

  17. Robinson, A. L. et al. Rethinking organic aerosols: semivolatile emissions and photochemical aging. Science 315, 1259–1262 (2007)

    Article  ADS  CAS  Google Scholar 

  18. Zheng, M. et al. Seasonal trends in PM2. 5 source contributions in Beijing, China. Atmos. Environ. 39, 3967–3976 (2005)

    Article  ADS  CAS  Google Scholar 

  19. Wang, G. H. et al. High loadings and source strengths of organic aerosols in China. Geophys. Res. Lett. 33, L22801 (2006)

    Article  ADS  Google Scholar 

  20. Atkinson, R. & Arey, J. Atmospheric degradation of volatile organic compounds. Chem. Rev. 103, 4605–4638 (2003)

    Article  CAS  Google Scholar 

  21. Wang, X. F. et al. The secondary formation of inorganic aerosols in the droplet mode through heterogeneous aqueous reactions under haze conditions. Atmos. Environ. 63, 68–76 (2012)

    Article  ADS  CAS  Google Scholar 

  22. Ervens, B., Turpin, B. J. & Weber, R. J. Secondary organic aerosol formation in cloud droplets and aqueous particles (aqSOA): a review of laboratory, field and model studies. Atmos. Chem. Phys. 11, 11069–11102 (2011)

    Article  ADS  CAS  Google Scholar 

  23. Seinfeld, J. H. & Pandis, S. N. Atmospheric Chemistry and Physics: From Air Pollution to Climate Change 2nd edn (Wiley, 2006)

    Google Scholar 

  24. Hallquist, M. et al. The formation, properties and impact of secondary organic aerosol: current and emerging issues. Atmos. Chem. Phys. 9, 5155–5236 (2009)

    Article  ADS  CAS  Google Scholar 

  25. Wang, X. et al. Characterization of organic aerosol produced during pulverized coal combustion in a drop tube furnace. Atmos. Chem. Phys. 13, 10919–10932 (2013)

    Article  ADS  Google Scholar 

  26. Wang, Y., Zhang, Q. Q., He, K., Zhang, Q. & Chai, L. Sulfate-nitrate-ammonium aerosols over China: response to 2000–2015 emission changes of sulfur dioxide, nitrogen oxides, and ammonia. Atmos. Chem. Phys. 13, 2635–2652 (2013)

    Article  ADS  Google Scholar 

  27. Xing, J. et al. Projections of air pollutant emissions and its impacts on regional air quality in China in 2020. Atmos. Chem. Phys. 11, 3119–3136 (2011)

    Article  ADS  CAS  Google Scholar 

  28. Tiwari, S. et al. Diurnal and seasonal variations of black carbon and PM2.5 over New Delhi, India: Influence of meteorology. Atmos. Res. 125–126, 50–62 (2013)

    Article  Google Scholar 

  29. The United Nations Environment Program (UNEP). Africa Environment Outlook 3: Our Environment, Our Health (2013); available at

  30. The World Health Organization (WHO). 7 Million Premature Deaths Annually Linked to Air Pollution (published online 25 March 2014); available at

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The research leading to these results received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 290605, the Swiss National Science Foundation (SAPMAV, no.200021_13016, WOOSHI, no. 200021L_140590, and Ambizione, PZ00P2_131673), the Swiss Competence Centers Environment and Sustainability as well as Energy and Mobility under project OPTIWARES, the National Science Foundation of China (no. 40925009), the “Strategic Priority Research Program” of the Chinese Academy of Sciences (XDA05100402), and the Helmholtz Virtual Institute of Complex Molecular Systems in Environmental Health – Aerosol and Health (HICE). The help of G. Salazar (University of Bern) during 14C analysis is acknowledged.

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Authors and Affiliations



R.-J.H., I.E.H. and C.B. wrote the paper. R.-J.H., J.-J.C. and A.S.H.P. designed the study. R.-J.H., I.E.H., C.B. and K.R.D. performed the offline AMS analysis. Y.Z., P.Z. and S. S. performed the 14C analysis. M.S. performed the IC analysis. G.A. and J.S.-K. performed the TD-GC-MS analysis. R.-J.H., I.E.H., C.B. and A.S.H.P. analysed the data. All authors reviewed and commented on the paper.

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Correspondence to Jun-Ji Cao or André S. H. Prévôt.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains additional information on the sample collection and sampling sites (Section 1); details of the chemical analysis (Section 2); extensive evaluation of a set of environmentally optimal solutions for source apportionment of PM2.5 and OC using the CMB and ME-2 models (Section 3); evaluation of model uncertainty and the sensitivity of the results to model inputs as well as the estimate of the contribution of fossil and non-fossil sources to secondary organic aerosol (Section 4); examination of potentially unidentified sources (Section 5); representativeness of the measurement sites (Section 6) and relevance of SOA formation (Section 7). The Supplementary Information also includes Supplementary Figures S1-S30, Supplementary Tables S1-S3 and additional references. (PDF 2634 kb)

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Huang, RJ., Zhang, Y., Bozzetti, C. et al. High secondary aerosol contribution to particulate pollution during haze events in China. Nature 514, 218–222 (2014).

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