Effects of seasonal management programs on PM 2.5 in Seoul and Beijing using DN-PMF: Collaborative efforts from the Korea-China joint research

South Korea and China have implemented increasingly stringent mitigation measures to reduce the health risks from PM exposure, jointly conducting a ground-based air quality observation study in Northeast Asia. Dispersion normalized positive matrix factorization (DN-PMF) was used to identify PM sources in Seoul and Beijing and assess the effectiveness of the seasonal management programs (SMPs) through a comparative study. Samples were collected during three periods: January-December 2019, September 2020-May 2021, and July 2021-March 2022. In Seoul, ten sources were resolved (Secondary nitrate: 8.67 μg/m , 34 %, Secondary sulfate: 5.67 μg/m , 22 %, Motor vehicle: 1.83 μg/m , 7.2 %, Biomass burning: 2.30 μg/m , 9.1 %, Residual oil combustion: 1.66 μg/m , 6.5 %, Industry: 2.15 μg/m , 8.5 %, Incinerator: 1.39 μg/m , 5.5 %, Coal combustion: 0.363 μg/m , 1.4 %, Road dust/soil: 0.941 μg/m , 3.7 %, Aged sea salt: 0.356 μg/m , 1.4 %). The SMP significantly decreased PM mass concentrations and source contributions of motor vehicle, residual oil combustion, industry, coal combustion, and biomass burning sources (p-value