Work

Wintertime Trends of Fine Particulate Matter (PM 2.5 ) in South Korea, 2012–2022: Response of Nitrate and Organic Components to Decreasing NO x Emissions

Year: 2025

Type: article

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.

Source: Geophysical Research Letters

DOI: 10.1029/2025gl116091