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.

ABSTRACT According to the data of the Taiwan Air Quality Monitoring Network (TAQMN), the suspenden particulates decreases gradually with year at the Kao-Ping Air Quality Area, but the ozone increases with year and deteriorates. Therefore, the problem of the ozone is wating for solving at Kao-Ping Air Quality Area. Because the ground-level ozone has a relationship with NOx and VOC, they are thought to be the major precursors of the ozone. The concentration of the ozone is not linearly related with concentrations NOx and VOC. The precursors of the ozone affect the ground-level ozone, so the photochemical indicators are further developed in recent years. The photochemical indicators H2O2,HNO3 and NOy in this study in Kaohsiung area are analysed by criteria values (Sillman,1995 and 1997) and on-site sampling. The sampling sites are at Nan-Zih, Siao-Gang, Lin-Yuan and Chiao-Tou. The results can determine the major precursors forming ozone. In addition Smog Production Model (SPM) is also used to analyze the results. According to the analyses of the photochemical indicators, Nan-Zih, Siao-Gang, Lin-Yuan and Chiao-Tou are VOC-limited in the spring, summer, fall and winter.According to the analysis result of SPM, the four sites are also VOC-limited in four seasons.

The weakly bound association products of atmospherically relevant radical species (O₂, OH, NO₂, HO₂ and NO) have been studied theoretically using quantum-chemical methods. The thermodynamic stabilities, which are crucial to determining the probability of formation in Earth's atmosphere, were calculated for the hydrotrioxy radical (HOOO) and peroxynitrous acid (HOONO, an isomer of nitric acid) relative to the radical dissociation products. In the case of HOONO, the experimentally determined values were confirmed. For HOOO, the predicted stability was significantly lower than the experimentally determined value; a conclusion that was supported by later experimental work and indicates that HOOO will not form in significant quantities in Earth's atmosphere. The fundamental and multi-quantum vibrational transitions were also predicted for both the HOONO and HOOO systems. The theoretical work on the HOONO system aided the assignment of experimental spectra and was used to correct equilibrium rotational constants. The HOOO system presented a challenge for the methods used here and work to apply other approaches in describing the vibrational modes is ongoing. Second-order vibrational perturbation theory, combined with a correlated quantum-chemical method and a moderately sized basis set, provides a method for accurately predicting fundamental and low-order multi-quantum transition energies and intensities for many systems (HOOO being an exception). Here coupled cluster theory, at a level which treats one- and two-electron correlation with a correction for three-electron correlation, and atomic natural orbitals basis sets were used in the vibrational calculations. To predict the dissociation energies of weakly bound species with the precision required (due to the small energy differences involved), high-order correlation contributions (a full treatment of three-electron correlation and a correction for four-electron correlation) are included, as is extrapolation to the basis set limit. Other contributions, such as that for the zero-point energy, were also considered. For the HOOO system, one-dimensional potential curves along the dissociation and torsional coordinates were constructed with standard single-reference and equation-of-motion coupled-cluster methods. The latter is better able to describe the nature of a system in the bond-breaking region and the complex electronic structure of a species formed from two radical fragments, one doubly degenerate in the ground state: X²[Pi] OH and X³[Sigma] O₂. A possible barrier to dissociation and the torsional potential for HOOO were investigated. / text