Articles | Volume 15, issue 3
Atmos. Chem. Phys., 15, 1299–1312, 2015
Atmos. Chem. Phys., 15, 1299–1312, 2015

Research article 06 Feb 2015

Research article | 06 Feb 2015

Fossil vs. non-fossil sources of fine carbonaceous aerosols in four Chinese cities during the extreme winter haze episode of 2013

Y.-L. Zhang1,2,3,4, R.-J. Huang2,6, I. El Haddad2, K.-F. Ho5,6, J.-J. Cao6, Y. Han6, P. Zotter2, C. Bozzetti2, K. R. Daellenbach2, F. Canonaco2, J. G. Slowik2, G. Salazar1,3, M. Schwikowski2,3, J. Schnelle-Kreis7, G. Abbaszade7, R. Zimmermann7,8, U. Baltensperger2, A. S. H. Prévôt2, and S. Szidat1,3 Y.-L. Zhang et al.
  • 1Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
  • 2Paul Scherrer Institute (PSI), Villigen, 5232 Villigen-PSI, Switzerland
  • 3Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland
  • 4Yale-NUIST Center on Atmospheric Environment, Nanjing University of Information Science and Technology, Nanjing, Jiangsu, China
  • 5School of Public Health and Primary Care, Chinese University of Hong Kong, Hong Kong, China
  • 6Key Laboratory of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, 710061 Xi'an, China
  • 7Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Joint Mass Spectrometry Centre, Cooperation Group Comprehensive Molecular Analytics, and Helmholtz Virtual Institute of Complex Molecular Systems in Environmental Health – Aerosol and Health (HICE), 85764 Neuherberg, Germany
  • 8University of Rostock, Joint Mass Spectrometry Centre, Institute of Chemistry – Chair of Analytical Chemistry, 18015 Rostock, Germany

Abstract. During winter 2013, extremely high concentrations (i.e., 4–20 times higher than the World Health Organization guideline) of PM2.5 (particulate matter with an aerodynamic diameter < 2.5 μm) mass concentrations (24 h samples) were found in four major cities in China including Xi'an, Beijing, Shanghai and Guangzhou. Statistical analysis of a combined data set from elemental carbon (EC), organic carbon (OC), 14C and biomass-burning marker measurements using Latin hypercube sampling allowed a quantitative source apportionment of carbonaceous aerosols. Based on 14C measurements of EC fractions (six samples each city), we found that fossil emissions from coal combustion and vehicle exhaust dominated EC with a mean contribution of 75 ± 8% across all sites. The remaining 25 ± 8% was exclusively attributed to biomass combustion, consistent with the measurements of biomass-burning markers such as anhydrosugars (levoglucosan and mannosan) and water-soluble potassium (K+). With a combination of the levoglucosan-to-mannosan and levoglucosan-to-K+ ratios, the major source of biomass burning in winter in China is suggested to be combustion of crop residues. The contribution of fossil sources to OC was highest in Beijing (58 ± 5%) and decreased from Shanghai (49 ± 2%) to Xi'an (38 ± 3%) and Guangzhou (35 ± 7%). Generally, a larger fraction of fossil OC was from secondary origins than primary sources for all sites. Non-fossil sources accounted on average for 55 ± 10 and 48 ± 9% of OC and total carbon (TC), respectively, which suggests that non-fossil emissions were very important contributors of urban carbonaceous aerosols in China. The primary biomass-burning emissions accounted for 40 ± 8, 48 ± 18, 53 ± 4 and 65 ± 26% of non-fossil OC for Xi'an, Beijing, Shanghai and Guangzhou, respectively. Other non-fossil sources excluding primary biomass burning were mainly attributed to formation of secondary organic carbon (SOC) from non-fossil precursors such as biomass-burning emissions. For each site, we also compared samples from moderately to heavily polluted days according to particulate matter mass. Despite a significant increase of the absolute mass concentrations of primary emissions from both fossil and non-fossil sources during the heavily polluted events, their relative contribution to TC was even decreased, whereas the portion of SOC was consistently increased at all sites. This observation indicates that SOC was an important fraction in the increment of carbonaceous aerosols during the haze episode in China.

Short summary
Source apportionment of fine carbonaceous aerosols using radiocarbon and other organic markers measurements during 2013 winter haze episodes was conducted at four megacities in China. Our results demonstrate that fossil emissions predominate EC with a mean contribution of 75±8%, whereas non-fossil sources account for 55±10% of OC; and the increment of TC on heavily polluted days was mainly driven by the increase of secondary OC from both fossil-fuel and non-fossil emissions.
Final-revised paper