Wintertime Trends of Fine Particulate Matter (PM <sub>2.5</sub> ) in South Korea, 2012–2022: Response of Nitrate and Organic Components to Decreasing NO <sub>x</sub> Emissions
Abstract We analyze 2011–2022 trends in wintertime fine particulate matter (PM 2.5 ) and its composition in South Korea using surface network data and machine learning. PM 2.5 decreased nationwide by 1.2 μg m −3 per year after correcting for meteorology. However, Seoul PM 2.5 declined only after 2019 and its composition has shifted toward particulate nitrate (pNO 3 − ) and organic aerosol (OA). Trends in pNO 3 − , OA, nitrogen dioxide (NO 2 ), and ozone (O 3 ) suggest that nighttime formation of the nitrate radical (NO 3 ) from the NO 2 + O 3 reaction is a key driver of pNO 3 − and secondary OA (SOA) formation. Increasing O 3 as nitrogen oxide (NO x ) emissions decline has increased nighttime NO 3 production over the 2012–2022 period, promoting pNO 3 − and SOA formation. As NO x emissions in South Korea continue to decline, transition from NO x ‐saturated to NO x ‐limited conditions for NO 3 formation should lead to rapid decreases in nighttime PM 2.5 formation.
Authors
- Laura Hyesung Yang (ORCID: https://orcid.org/0000-0002-0057-7120)
- Hwajin Kim (ORCID: https://orcid.org/0000-0001-6138-6443)
- Soontae Kim (ORCID: https://orcid.org/0000-0002-1198-934X)
- Hong Liao (ORCID: https://orcid.org/0000-0001-6628-1798)
- Yujin J. Oak (ORCID: https://orcid.org/0000-0003-4719-8790)
- Jinsoo Choi (ORCID: https://orcid.org/0000-0001-8135-8562)
- D. J. Jacob
- Shixian Zhai (ORCID: https://orcid.org/0000-0002-0073-7809)
- Ellie Beaudry
- Nadia K. Colombi (ORCID: https://orcid.org/0009-0004-5052-0095)
- Ruijun Dang (ORCID: https://orcid.org/0000-0002-7662-3816)
- Drew C. Pendergrass (ORCID: https://orcid.org/0000-0002-8210-4983)
- Ke Li (ORCID: https://orcid.org/0000-0002-9181-3562)
- Jinsoo Park (ORCID: https://orcid.org/0000-0002-5781-3796)
Institutions
- Planetary Science Institute (US)
- Harvard University (US)
- Seoul National University (KR)
- Chinese University of Hong Kong (HK)
- Nanjing University of Information Science and Technology (CN)
- Korea National Institute of Health (KR)
- Ajou University (KR)
- National Institute of Environmental Research (KR)
Publication Details
- Journal
- Geophysical Research Letters
- Published
- 2025-10-10
- DOI
- https://doi.org/10.1029/2025gl116091
- Citations
- 2
- Primary Topic
- Atmospheric chemistry and aerosols
- Type
- article
- Field-Weighted Citation Impact
- 2.60