An overview of emissions of SO2 and NOx and the long-range transport of oxidized sulfur and nitrogen pollutants in East Asia

The long-range transport of oxidized sulfur (sulfur dioxide (SO₂) and sulfate) and oxidized nitrogen (nitrogen oxides (NO_x) and nitrate) in East Asia is an area of increasing scientific interest and political concern. This paper reviews various published papers, including ground- and satellite-based observations and numerical simulations. The aim is to assess the status of the anthropogenic emissions of SO₂ and NO_x and the long-range transport of oxidized S and N pollutants over source and downwind region. China has dominated the emissions of SO₂ and NO_x in East Asia and urgently needs to strengthen the control of their emissions, especially NO_x emissions. Oxidized S and N pollutants emitted from China are transported to Korea and Japan, due to persistent westerly winds, in winter and spring. However, the total contributions of China to S and N pollutants across Korea and Japan were not found to be dominant over longer time scales (e.g., a year). The source–receptor relationships for oxidized S and N pollutants in East Asia varied widely among the different studies. This is because: (1) the nonlinear effects of atmospheric chemistry and deposition processes were not well considered, when calculating the source–receptor relationships; (2) different meteorological and emission data inputs and solution schemes for key physical and chemical processes were used; and (3) different temporal and spatial scales were employed. Therefore, simulations using the same input fields and similar model configurations would be of benefit, to further evaluate the source–receptor relationships of the oxidized S and N pollutants.