The objective of this project is to analyze the trend and factors of ozone variation in Taiwan according to the data of Taiwan EPA air quality monitoring network, international references and a series of intensive field measurements. In addition, relationship between ozone and its precursors is also examined to estimate and understand which precursors dominate ozone formation in Taiwan. The main results and assessments include: (1) Two factors contributed to the ozone increase in last decade in Taiwan: decreased nitrogen oxide titration of ozone, long-range transport of increasing ozone from the Asian continent. (2) For ozone control in Kaohsiung, NMHC is more efficient than NOx due to not only NO titration effect of ozone but also the nonlinearity of the ozone production efficiency as a function of NOx. (3) Variation of total oxidant concentrations (O3+NO2) significantly followed ethylbenzene/m,p-xylene ratios (the degree of photochemical processing) during the measurement periods in Taipei and Taichung. (4) In both Taipei and Taichung, xylene, toluene, 1,2,4-TMB, isoprene, CO, ethene and propene were calculated to have the highest ozone formation potentials (OFPs). Nevertheless, xylene, 1,2,4-TMB, CO, ethene and propene were mainly from traffic sources, toluene had significant emissions and/or leakage from non-traffic sources (5) In Kaohsiung, xylene, ethene, toluene, propene, CO and 1,2,4-TMB were calculated to have the highest OFPs. Ethene, toluene and propene were estimated that about 48-67%, 34-68%, 45-57% were emitted and/or leaked from non-traffic sources (industrial and solvent usage).

Ozone; Ozone Precursors; Long-Range Transport