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

TL;DR

This study investigates the role of anthropogenic coarse particulate matter in East Asia, revealing its impact on fine particulate nitrate formation and emphasizing the need for stricter emission controls to improve air quality.

Contribution

It demonstrates that including coarse PM in models improves the understanding of PM2.5 nitrate dynamics and highlights the importance of controlling ammonia and nitrogen oxides emissions.

Findings

Coarse PM decreased by 21% from 2015 to 2019.

Including coarse PM in models reduces simulated PM2.5 nitrate.

Decreasing coarse PM increases PM2.5 nitrate in summer and winter.

Abstract

Coarse particulate matter (PM) is a serious air pollution problem in East Asia. Analysis of air quality network observations in the North China Plain and the Seoul Metropolitan Area shows that it is mainly anthropogenic and has decreased by 21% over 2015-2019. This anthropogenic coarse PM is generally not included in air quality models but scavenges nitric acid to suppress the formation of fine particulate (PM2.5) nitrate, a major contributor to PM2.5 pollution. Including it in the GEOS-Chem model decreases simulated PM2.5 nitrate to improve agreement with observations. Decreasing anthropogenic coarse PM over 2015-2019 directly increases PM2.5 nitrate in summer, offsetting the effect of other emission controls, while in winter it increases the sensitivity of PM2.5 nitrate to ammonia and sulfur dioxide emissions. Our work implies the need for stronger ammonia and nitrogen oxides emission controls to improve PM2.5 air quality as coarse PM continues to decrease.