Analysis of wintertime NO2 pollution in the Tokyo metropolitan area

The high concentration of NO2 in the Tokyo Metropolitan area was investigated by means of air quality monitoring station data analysis and two numerical models: a photochemical box model and a photochemical grid model. Based on monitoring data, the typical variation with time of NO, NO2 and O3 for days with high NO2 concentrations is presented. The application of the photochemical box and photochemical grid models successfully reproduced these variations when using typical emission intensities for NOx and NMHC from the Tokyo downtown area. Model results revealed that the high concentrations of NO2 in winter (exceeding the Japan environmental quality standard) mainly result from photochemical oxidation of NO to NO2.