Effects of efforts to reduce air pollutants such as PM2.5 on increasing surface ozone concentrations

Abstract

Global climate change and increased air pollutant emissions in East Asia have led to an increase in tropospheric ozone concentrations, especially in South Korea. In order to reduce both particulate matter (PM2.5) and ozone concentrations in Korea, efforts to reduce emissions of precursors (NO2, VOCs) and particulate matter have been implemented, and as a result, the concentration of particulate matter has been continuously reduced. However, contrary to expectations, ozone concentrations have continued to increase, and the trend is that both the annual average concentration as well as the number and duration of high concentration ozone events are increasing. Factors affecting tropospheric ozone production are very diverse and complex, including climate change, emission characteristics of precursors (NOx, VOCs) and resulting changes in atmospheric chemical species, changes in chemical reactions due to changes in atmospheric aerosols, natural source VOCs, long-range transport of ozone and precursors, geography and topography, and differences in ozone production characteristics between countries, cities, and regions. While there are global influences such as climate change and long-distance transport of high ozone concentrations from neighboring countries that are responsible for the increase in ozone concentrations in Korea, there is also evidence from various observations that suggests that due to the non-linear relationship between ozone production and its precursors, air pollutant reduction efforts are contributing to the increase in ozone concentrations by changing the local atmospheric chemical composition. The study analyzes changes in ozone precursor emissions, atmospheric chemical composition, and aerosol concentrations resulting from efforts to reduce various air pollutants, including particulate matter and ozone, and ultimately provides insight into how air pollution mitigation efforts are contributing to increased ozone concentrations. The insights are expected to clarify existing understanding of the limiting conditions and chemical reactors for NOx and VOCs involved in ozone formation in urban areas, and to provide evidence and ideas for further understanding.   Acknowledgments This research was supported by Particulate Matter Management Specialized Graduate Program through the Korea Environmental Industry & Technology Institute(KEITI) funded by the Ministry of Environment(MOE)