Ground-level ozone (O3) is a secondary pollutant produced by its precursors, such as volatile organic compounds (VOC) and nitrogen oxides (NOx) through complex photochemical reactions in sunlight. This study was aimed to investigate the relationships of surface ozone with its precursors in urban locations. Atmospheric measurements of hydrogen peroxide (H2O2) and nitric acid (HNO3) were conducted at the three sites, namely Nan-Tze, Chien-Chin and Hsiung-Kong, in Kaohsiung City during three consecutive days of fall, winter and spring seasons in 2002-2003, from which the ozone-VOC-NOx sensitive regimes were derived using two methods, namely the indicator ratios of H2O2/HNO3 and O3/HNO3 developed by Sillman (1997), and the extent parameter, E, of SPM (Smog Production Model) developed by Blanchard (1994). Measurements indicate that H2O2 reaches its peak concentration approximately at noon to afternoon (12:00 to 15:00); meanwhile HNO3 reaches its lowest concentration. In general, fall season has highest concentrations on H2O2 and HNO3, followed by spring and winter. The correlation analyses indicate that ozone has positive relationships with temperature and solar insolation, while it has negative relationships with NOx, NO and NO2. According to the indicator ratios of H2O2/HNO3 = 0.3 ¡V 0.6, O3/HNO3 = 12 -16 (Sillman, 1997), results show that VOC-limited regimes occupy about 62.5% and 58.3% at the Hsiung-Kong site, 47.8% and 69.6% at the Nan-Tze site, and 33.3% and 70.8% at the Chien-Chin site in the fall season. Results also show that VOC-limited regimes occupy about 80.9% and 66.7% at the Hsiung-Kong site, 54.2% and 41.7% at the Nan-Tze site, and 70.8% and 45.8% at the Chien-Chin site in the winter, while it is 52.4¢Mand 80.9¢Mat the Hsiung-Kong site, 50.0¢Mand 66.7¢Mat the Nan-Tze site, and 35.7¢Mand 28.6¢Mat the Chien-Chin site in the spring. According to the critical value of extent parameter, Ecrit = 0.7 (Blanchard, 1994), IV results show that VOC-limited regimes pre-dominate at three sites in autumn, winter and spring, all occupying 100% except in that a VOC-limited regime occupies about 91.7% at the Chien-Chin site in spring. In summary, the ozone-VOC-NOx sensitivity results derived from indicator ratios agree fairly well with SPM results, except for the Chien-Chin site in spring. The indicator ratios and Ecrit are frequently considered to be universal under given assumptions. However, these values may vary with meteorology and topography. Further studies are needed to characterize these parameters locally.

ABSTRACT Ground-level ozone (O3) is a secondary pollutant produced by its precursors, such as volatile organic compounds (VOC) and nitrogen oxides (NOx) through complex photochemical reactions in sunlight. This study was aimed to investigate the relationships of surface ozone with its precursors in the urban and rural locations in Pingtung County. Atmospheric measurements of hydrogen peroxide (H2O2) and nitric acid (HNO3) were conducted at the two sites, namely Pingtung city and Chaochou, in Pingtung County during three consecutive days of fall, winter and spring seasons in 2002-2003, from which the ozone-VOC-NOx sensitive regimes were derived using two methods, namely the indicator ratios of H2O2/HNO3 and O3/HNO3 developed by Sillman (1997), and the extent parameter, E, of SPM (Smog Production Model) developed by Blanchard (1994). According to the indicator ratios of H2O2/HNO3 = 0.3 ¡V 0.6, O3/HNO3 = 12 -16 (Sillman, 1997), results at the Pingtung site show that VOC-limited regimes occupy about 68% in autumn, winter and spring. Results at the Chaochou site show that VOC-limited regimes occupy about 52.8% in autumn and winter, while NOx-limited regimes occupy about 54.2% in spring. According to the critical value of extent parameter, Ecrit = 0.7 (Blanchard, 1994), results show that VOC-limited regimes predominate (93.8%) at Pingtung site in winter and spring. Results at the Chaochou site show that VOC-limited regimes predominate (87.5%) in winter, while NOx-limited regimes predominate (58.3%) in spring. In summary, the ozone-VOC-NOx sensitivity results derived from indicator ratios agree fairly well with SPM results. The indicator ratios and Ecrit are frequently considered to be universal under given assumptions. However, these values may vary with meteorology and topography. Further studies are needed to characterize these parameters locally.