Verification of NOx emission inventory over South Korea using sectoral activity data and satellite observation of NO2 vertical column densities

In this study, the emission inventories of NOx, which is a major air pollutant of South Korea were compared and analyzed. The two bottom-up emission inventories, Clean Air Policy Support System (CAPSS) and Regional Emission inventory in ASia (REAS), which are the latest emission inventories about the air pollutant emissions about South Korea were compared to find out the trend of NOx emission during 1996–2005. Also, these two emission inventories were compared with the top down NOx emissions estimated from satellite observations to validate the amount of NOx emitted from South Korea. The total NOx emission trends, sectoral and regional comparisons were carried out. The trend of the top down estimated NOx emission was similar to CAPSS and REAS. However, the magnitudes of the top down estimated NOx emission were usually closer to those of CAPSS than those of REAS. The NOx emissions from transportation sector of REAS were larger than that of CAPSS, and this corresponded to the difference of total amount of NOx emission between CAPSS and REAS. By comparing the differences of the ratios of the vehicle kilometers traveled (VKT) and emission factors (EFs), it was identified that most of the difference between CAPSS and REAS was due to these factors for diesel vehicles in REAS. Implications of this higher VKT values in REAS were discussed.