Modeling Study of the Relationship between Photochemical Ozone and Its Preursor Emission of Nitrigen Oxides and Hydrocarbons in Northern Taiwan

Taipei, an well-known densely populated mega-city with heavy traffic, is the rapidly expanding capital city of Taiwan, located in a basin surrounded by mountains on three sides and by two river valleys reaching northwesterly and northeasterly to the Pacific Ocean. Although the monitoring records of recent years show the continuous improvement of air quality, a high level of ozone is still a serious problem, the averaged ozone concentration increased by 10.1% from 1994 to 1998. Photochemical ozone is formed from nitrogen oxides and VOCs through non-linear chemical reactions under special weather conditions. The local scale circulations and airflow would be very complex in this region due to the very complex terrain and the special location. The combination of special meteorological conditions and high emissions in the area may result in very high concentrations of photochemically produced pollutants. The relationship between photochemical ozone and its precursor emission of nitrogen oxides and hydrocarbons in northern Taiwan were investigated based on data analysis and simulation with an air pollution modeling prediction system (APOPS). The use of such a modeling system is needed as northern Taiwan has great changes in topography and pollution episodes are often influenced by local thermal flows.