Recent Trends and Future Projections in Asian Air Pollution

Abstract

We studied trends in Asian air pollution in recent decades using air-quality monitoring station data, satellite retrieval data (GOME NO2), and regional-scale chemical transport model (CTM) simulation. A newly developed annual Asian-scale emission inventory (REAS) from 1980-2003 was used in observation data analysis and CTM. Analyses of recent trends in annual emissions in China by REAS and satellite GOME NO2 show an 8-10% increase after 2000 suggesting the impact of long-range transport of secondary air pollutants in regions and countries downwind. Detailed analyses of O3 observation data in Japan suggest an annual averaged O3 concentration increase of 2% yr-1 due to this long-range transport. We extended our regional air quality study targeting 2020. REAS provides three emission scenarios for China: the reference case (REF), the policy success case (PSC), and the policy failure case (PFC). Projected REF emissions for 2020 show O3 concentrations rising to 75 to 90 ppbv in June and 75 to 85 ppbv in August over the North China Plain. Projected PFC emissions bring an increase of monthly averaged O3 with greater than 20 ppbv (1 ppbv yr-1 growth) in the North China Plain. Surface O3 under the PFC scenario is enhanced by 6 to 8 ppbv over the Korean Peninsula and by 2 to 6 ppbv in Japan from 2000 to 2020 despite the reduction of NOx in Japan. This may become a critical level in air quality in Asia.