Estimation of Local and Transboundary Impacts on Pm2.5 Source Contributions by the Unprecedented Cross-Country Experiment During the Covid-19 Outbreak
The COVID-19 pandemic led to a significant reduction in PM2.5 levels in Seoul, with a notable decrease in contributions from various pollution sources.
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this study against the rest of the dsip corpusSummary and findings
This study evaluated the local and transboundary impacts on PM2.5 source contributions in Seoul, Korea during the early COVID-19 outbreak from January to March 2020. The analysis compared PM2.5 concentrations and source contributions to similar periods in 2019. Significant reductions in PM2.5 concentrations were observed, with various sources showing decreased contributions.
Abstract
Korea and China have been regulating fine particulate matter (PM2.5) sources because it causes severe impacts on public health and economic losses in Northeast Asia. Despite stringent regulations, local and transboundary impacts of PM2.5 sources continue to affect air quality in Seoul, Korea and are not yet fully understood, raising cross-country issues. The early stage of the COVID-19 outbreak during January–March 2020 was an unprecedented period that provided a cross-country experiment to separate the local and transboundary impacts on contributions of PM2.5 sources identified in Seoul. Thus, Seoul’s PM2.5 concentrations and source contributions during this period were statistically evaluated relative to comparable periods in 2019 using dispersion normalized positive matrix factorization (DN-PMF) and synoptic meteorological analysis. The monthly average of PM 2.5 concentration and contributions of secondary nitrate, sulfate, biomass burning, and district heating and incineration in Seoul in March 2020 decreased significantly (−47%, −54%, −59%, −75%, and −52%, respectively) (p < 0.001) compared to 2019. Especially, episodes 1 and 2 showed transboundary impacts of PM 2.5 sources under meteorological patterns favorable for long-range transport from China to Seoul. During episode 1, residential coal combustion in northeastern China enhanced sulfate and secondary nitrate contributions in Seoul. During episode 2, China's emission reductions reduced the contributions from the primary sources (primary sulfate, biomass burning, district heating and incineration, mining industry, metallurgical industry, and oil combustion) and secondary nitrate to the maximum in Seoul. However, during episode 3, atmospheric stagnation on the Korean Peninsula enhanced the contributions of mobile and coal combustion in Seoul. The COVID-19 pandemic in China clearly separated the local and transboundary impacts on the contributions of PM2.5 sources in Seoul.