19 Nov 2020

19 Nov 2020

Review status: this preprint is currently under review for the journal ACP.

Source Apportionment of Carbonaceous Aerosols in Beijing with Radiocarbon and Organic Tracers: Insight into the Differences between Urban and Rural Sites

Siqi Hou1,, Di Liu1,a,, Jingsha Xu1, Tuan V. Vu1,b, Xuefang Wu2, Deepchandra Srivastava1, Pingqing Fu3, Linjie Li4,c, Yele Sun4, Athanasia Vlachou5, Vaios Moschos5, Gary Salazar6, Sönke Szidat6, André S. H. Prévôt5, Roy M. Harrison1, and Zongbo Shi1 Siqi Hou et al.
  • 1School of Geography Earth and Environmental Science, University of Birmingham, Birmingham, B15 2TT, UK
  • 2School of Earth Sciences and Resources, China University of Geosciences, Xueyuan Road 29, 100083, Beijing, China
  • 3Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China
  • 4State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric, Physics, Chinese Academy of Sciences, Beijing, 100029, China
  • 5Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen PSI, CH-5232, Switzerland
  • 6Department of Chemistry and Biochemistry & Oeschger Centre for Climate Change Research, University of Bern, Bern, CH-3012, Switzerland
  • anow at: Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China
  • bnow at: School of Public Health, Imperial College London, London, UK
  • cnow at: Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg 41296, Sweden
  • These authors contributed equally to this work.

Abstract. Carbonaceous aerosol is the dominant component of fine particles in Beijing. However, it is challenging to apportion its sources. Here, we applied a newly developed method which combined radiocarbon (14C) with organic tracers to apportion the sources of fine carbonaceous particles at an urban (IAP) and a rural (PG) site of Beijing. PM2.5 filter samples (24-h) were collected at both sites from 10 November to 11 December 2016 and from 22 May to 24 June 2017. 14C was determined in 25 aerosol samples (13 at IAP and 12 at PG) representing low pollution to haze conditions. Biomass burning tracers (levoglucosan, mannosan and galactosan) in the samples were also determined using GC-MS. Higher contributions of fossil-derived OC (OCf) were found at the urban site. OCf to OC ratio decreased in the summer samples (IAP: 67.8 ± 4.0 % in winter and 54.2 ± 11.7 % in summer; PG: 59.3 ± 5.7 % in winter and 50.0 ± 9.0 % in summer) due to less consumption of coal in the warm season. A novel extended Gelencsér method incorporating the 14C and organic tracer data was developed to estimate the fossil and non-fossil sources of primary and secondary OC (POC and SOC). It showed that fossil-derived POC was the largest contributor to OC (35.8 ± 10.5 % and 34.1 ± 8.7 % in winter time for IAP and PG, 28.9 ± 7.4 % and 28.9 ± 9.6 % in summer), regardless of season. SOC contributed 50.0 ± 12.3 % and 47.2 ± 15.5 % at IAP, and 42.0 ± 11.7 % and 43.0 ± 13.4 % at PG in the winter and summer sampling periods respectively, within which the fossil-derived SOC was predominant and contributed more in winter. The non-fossil fractions of SOC increased in summer due to a larger biogenic component. Concentrations of biomass burning OC (OCbb) are resolved by the extended Gelencsér method with average contributions (to total OC) of 10.6 ± 1.7 % and 10.4 ± 1.5 % in winter at IAP and PG, and 6.5 ± 5.2 % and 17.9 ± 3.5 % in summer, respectively. Correlations of water-insoluble OC (WINSOC), water-soluble OC (WSOC) with POC and SOC showed that although WINSOC was the major contributor to POC, a non-negligible fraction of WINSOC was found in SOC for both fossil and non-fossil sources especially during winter. In summer, a greater proportion of WSOC from non-fossil sources was found in SOC. Comparisons of the source apportionment results with those obtained from a Chemical Mass Balance model were generally good, except for the cooking aerosol.

Siqi Hou et al.

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Status: final response (author comments only)
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Siqi Hou et al.

Data sets

Radiocarbon (14C) and source apportionment results by the extended Gelencsér method Roy M. Harrison, Siqi Hou, and Jingsha Xu

Siqi Hou et al.


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Short summary
This study provides a newly developed method which combines radiocarbon (14C) with organic tracers to enable source apportionment of primary and secondary fossil vs non-fossil sources of carbonaceous aerosols at an urban and a rural site of Beijing. The source apportionment results were compared with those by Chemical Mass Balance and AMS/ACSM-PMF methods. Correlations of WINSOC and WSOC with different sources of OC were also performed to elucidate the formation mechanisms of SOC.