Identification of nitrogen dioxide and ozone source regions for an urban area in Korea using back trajectory analysis

The NO2 and O-3 in an urban background site of Seoul, Korea (Yongsan), were analyzed using hourly data collected from 2005 to 2013. The potential role of meteorological parameters in controlling air quality at the receptor site was analyzed using a conditional probability function. In addition, the relative contributions of such variables were examined for special cases (i.e., more than 60 ppb of NO2 and O-3) with the help of trajectory. A potential source contribution function with a grid size resolution of 0.25 degrees x 0.25 degrees was used to determine the potential exogenous sources of NO2 and O-3 for the study area. The results of both the trajectory and potential source contribution function analyses suggest that both the northern China region and local emission sources are the most influential source pathways contributing to the recent increase in NO2 concentration at the study site. In the case of O-3, this role was shared by both oceanic and mountainous regions of China and Japan. (C) 2016 Elsevier B.V. All rights reserved.