08 May 2023
 | 08 May 2023
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Seasonal variations in composition and sources of atmospheric ultrafine particles in urban Beijing based on near-continuous measurements

Xiaoxiao Li, Yijing Chen, Yuyang Li, Runlong Cai, Yiran Li, Chenjuan Deng, Chao Yan, Hairong Cheng, Yongchun Liu, Markku Kulmala, Jiming Hao, James N. Smith, and Jingkun Jiang

Abstract. Understanding the composition and sources of atmospheric ultrafine particles (UFPs) is essential in evaluating their exposure risks. It requires long-term measurements with high time resolution, which are to date scarce. We performed near-continuous measurements of UFP composition during four seasons in urban Beijing using a thermal desorption chemical ionization mass spectrometer, accompanied by real-time size distribution measurements. We found that UFPs in urban Beijing are dominated by organic components, varying seasonally from 68 to 81 %. CHO organics are the most abundant in summer, while sulfur-containing organics, some nitrogen-containing organics, nitrate, and chloride are the most abundant in winter. With the increase of particle diameter, the contribution of CHO organics decreases, while that of sulfur-containing and nitrogen-containing organics, nitrate, and chloride increase. Source apportionment analysis of the UFP organics indicates contributions from cooking and vehicle sources, photooxidation sources enriched in CHO organics, and aqueous/heterogeneous sources enriched in nitrogen- and sulfur-containing organics. The increased contributions of cooking, vehicle, and photooxidation components are usually accompanied by simultaneous increases in UFP number concentrations related to cooking emission, vehicle emission, and new particle formation, respectively. While the increased contribution of the aqueous/heterogeneous composition is usually accompanied by the growth of UFP mode diameters. The highest UFP number concentrations in winter are due to the strongest new particle formation, the strongest local primary particle number emissions, and the slowest condensational growth of UFPs to larger sizes. This study provides a comprehensive understanding of urban UFP composition and sources and offers valuable datasets for the evaluation of UFP exposure risks.

Xiaoxiao Li et al.

Status: open (until 25 Jun 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-809', Anonymous Referee #1, 02 Jun 2023 reply

Xiaoxiao Li et al.


Total article views: 303 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
221 74 8 303 27 4 8
  • HTML: 221
  • PDF: 74
  • XML: 8
  • Total: 303
  • Supplement: 27
  • BibTeX: 4
  • EndNote: 8
Views and downloads (calculated since 08 May 2023)
Cumulative views and downloads (calculated since 08 May 2023)

Viewed (geographical distribution)

Total article views: 307 (including HTML, PDF, and XML) Thereof 307 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 07 Jun 2023
Short summary
The near-continuous measurements reveal the composition, sources, and seasonal variations of UFPs in urban Beijing. Vehicle, cooking emissions, and new particle formation are the main sources of UFP numbers and aqueous/heterogeneous processes increase UFP mode diameters in urban Beijing. UFP numbers are the highest in winter due to the highest primary particle emission rates and new particle formation rates, and CHO fractions are the highest in summer due to the strongest photooxidation.