Assessing the urban ozone production sensitivity trends in Korea using the measurements from nation-wide air-monitoring stations from 2001 to 2017

Many national and regional levels of efforts to control the abundance of ozone near the surface have been invested over the last few decades in many countries as the understanding of ozone deepens. However, the effectiveness of these efforts has been frequently questioned because the ozone concentration has not been reduced as anticipated, even though the precursors are under control. The main cause of difficulties in ozone control is to be in the limitations in characterizing ozone production sensitivity over the area of interest, which requires state-of-the-art researches in depth. Thus, the region with insufficient research resources, like Korea, struggles with the ozone issue which tends to be worse in these days. In this study, we introduce an efficient method to assess the ozone production sensitivity based on the measurements from the routine monitoring stations of air quality (O₃, NO₂, CO, SO₂, PM₁₀ and PM_2.5) and synoptic weather parameters (temperature, precipitation, relative humidity and etc.). We investigate the ozone production rate, P(O₃), as a function of NOx, temperature and day of week from 2001 to 2017, in Korea. As a result, Seoul shows different NOx reduction trends in different day of week; the NOx has been reduced and P(O₃) has been increased year by year only for weekdays, while no pattern is observed for weekends. In-depth analyses on the heterogeneity of ozone production characteristics with varying temperature and site locations are studied. The similar analysis results from other regions in Korea will be shown as against with Seoul and discussion about the direction on legitimate regulation will be addressed.