26 Jan 2023
 | 26 Jan 2023

Coarse particulate matter air quality in East Asia: implications for fine particulate nitrate

Shixian Zhai, Daniel J. Jacob, Drew C. Pendergrass, Nadia K. Colombi, Viral Shah, Laura Hyesung Yang, Qiang Zhang, Shuxiao Wang, Hwajin Kim, Yele Sun, Jin-Soo Choi, Jin-Soo Park, Gan Luo, Fangqun Yu, Jung-Hun Woo, Younha Kim, Jack E. Dibb, Taehyoung Lee, Jin-Seok Han, Bruce E. Anderson, Ke Li, and Hong Liao

Abstract. Air quality network data in China and South Korea show very high year-round mass concentrations of coarse particulate matter (PM), as inferred by difference between PM10 and PM2.5. Coarse PM concentrations in 2015 averaged 52 μg m-3 in the North China Plain (NCP) and 23 μg m-3 in the Seoul Metropolitan Area (SMA), contributing nearly half of PM10. Strong daily correlations between coarse PM and carbon monoxide imply a dominant source from anthropogenic fugitive dust. Coarse PM concentrations in the NCP and the SMA decreased by 21 % from 2015 to 2019 and further dropped abruptly in 2020 due to COVID-19 reductions in construction and vehicle traffic. Anthropogenic coarse PM is generally not included in air quality models but scavenges nitric acid to suppress the formation of fine particulate nitrate, a major contributor to PM2.5 pollution. GEOS-Chem model simulation of surface and aircraft observations from the KORUS-AQ campaign over the SMA in May–June 2016 shows that consideration of anthropogenic coarse PM largely resolves the previous model overestimate of fine particulate nitrate. The effect is smaller in the NCP which has a larger excess of ammonia. Model sensitivity simulations show that decreasing anthropogenic coarse PM over 2015–2019 directly increases PM2.5 nitrate in summer, offsetting half the effect of other emission controls, while in winter it increases the sensitivity of PM2.5 nitrate to ammonia and sulfur dioxide emissions. Decreasing coarse PM helps to explain the flat wintertime PM2.5 nitrate trends observed in the NCP and the SMA despite decreases in nitrogen oxides and ammonia emissions. The continuing decrease of coarse PM from abating fugitive dust pollution will require more stringent nitrogen oxides and ammonia emission controls to successfully decrease PM2.5 nitrate.

Shixian Zhai 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-2022-1485', Anonymous Referee #2, 18 Feb 2023
  • RC2: 'Comment on egusphere-2022-1485', Anonymous Referee #1, 19 Feb 2023
  • AC1: 'Comment on egusphere-2022-1485', Shixian Zhai, 16 Mar 2023

Shixian Zhai et al.


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Short summary
Anthropogenic fugitive dust is causing severe coarse particulate matter (PM) air pollution in East Asia. Due to emission control efforts, coarse PM decreased steadily. We find that the decrease of coarse PM is the major reason for the lack decrease of fine particulate nitrate, as it allows more nitric acid to form fine particulate nitrate. The continuing decrease of coarse PM requires more stringent ammonia and nitrogen oxides emission controls to successfully decrease fine particulate nitrate.