The object of this project is to explore ozone problem with data of Photochemical Assessment Monitoring Stations (PAMS) in Central Taiwan, and to identify the causes of high ozone concentration by means of air quality model simulation. Two periods of interest during 2002 were selected to represent high (October) and low (June) ozone episodes. Data of ozone and its precursor collected in PAMS in Central Taiwan were compared with corresponding EPA data and model simulations. NMHC observations with PAMS stations at Tsongneng, Tsoutuen, and Jusan include 56 VOCs. Observation data shows that benzene and isoprene values were lower in October than in June. But ozone concentrations are yet higher in October than in June. This indicates that amount of pollutants and intensities of photochemical processes are not sufficient to explain the formation of ozone in this region. Other data such as meteorological variables and model simulations results must be used. TAQM simulations were performed using 2002 June and October as representative low and high ozone episodes. Analysis of these simulation results compared several parameters for ozone formation and the level of impacts. Among those considered, direction of air flow appears to be the principal control parameter for air quality in Central Taiwan. For the autumnal northeasterly air flow, Central Taiwan is strongly affected by vortex entrapment on the lee side of the mountains. Land-sea flow reversal further adds to the build up of ozone and precursors. Our risk analysis shows that benzene appears to be the most harmful among all the observed VOCs in Taiwan. Overall, there does not appear to be any risk for acute health effect. However there are limited areas with potential for chronic exposures that may lead to cancer.

PAMS observation,Model Simulation,Risk Analysis