17 Apr 2023
 | 17 Apr 2023

High-time-resolution chemical composition and source apportionment of PM2.5 in northern Chinese cities: implications for policy

Yong Zhang, Jie Tian, Qiyuan Wang, Lu Qi, Manousos Ioannis Manousakas, Yuemei Han, Weikang Ran, Yele Sun, Huikun Liu, Renjian Zhang, Yunfei Wu, Tianqu Cui, Kaspar Rudolf Daellenbach, Jay Gates Slowik, André S. H. Prévôt, and Junji Cao

Abstract. Fine particulate matter (PM2.5) pollution is still one of China's most important environmental issues, especially in northern cities during wintertime. In this study, intensive real-time measurement campaigns were conducted in Xi’an, Shijiazhuang, and Beijing to investigate the chemical characteristics and source contributions of PM2.5 and explore the formation progress of heavy pollution for policy implications. The chemical compositions of PM2.5 in the three cities were all dominated by organic aerosol (OA) and nitrate (NO3-). Results of source apportionment analyzed by the hybrid environmental receptor model (HERM) showed that the secondary nitrate plus sulfate contributed higher to PM2.5 compared to other primary sources. Biomass burning was the dominant primary source in the three pilot cities. The contribution of coal combustion to PM2.5 is non-negligible in Xi’an and Shijiazhuang but is no longer the important contributor in the capital city of Beijing due to the execution of a strict coal-banning policy. The potential formation mechanisms of secondary aerosol in three cities were further explored by establishing the correlations between the secondary nitrate plus sulfate and aerosol liquid water content (ALWC), and Ox (O3 + NO2), respectively. The results showed that photochemical oxidation and aqueous-phase reaction were two important pathways of secondary aerosol formation. According to the source variations, air pollution events that occurred in campaigns were classified into three types: biomass combustion dominated, secondary nitrate plus sulfate dominated, and a combination of primary and secondary sources. Additionally, this study compared the changes in chemical composition and source contributions of PM2.5 in past decades. The results suggested that the clean energy replacements for the rural household should be urgently encouraged to reduce the primary source emissions in northern China, and collaborative control on ozone and particulate matter need to be continuously promoted to weaken the atmosphere oxidation capacity for the sake of reducing secondary aerosol formation.

Yong Zhang et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-457', Anonymous Referee #1, 09 May 2023
  • RC2: 'Comment on egusphere-2023-457', Anonymous Referee #2, 12 May 2023

Yong Zhang et al.


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Short summary
PM2.5 pollution still frequently occurred in northern China during winter, and it is necessary to figure out the causes of air pollution based on intensive real-time measurement. The findings elaborated the chemical characteristics and source contributions of PM2.5 in three pilot cities, revealed potential formation mechanisms of secondary aerosols, highlighted the importance of controlling biomass burning and inhibiting generation of secondary aerosol for air quality improvement.