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h i g h l i g h t s < A conceptual model is for the first time developed for ozone for Hong Kong. < Tropical cyclones are most conducive to the occurrence of high O 3 episodes. < Super-regional and regional transports are other factors that contribute to high O 3 levels in Hong Kong. a b s t r a c tPhotochemical ozone (O 3 ) formation is related to its precursors and meteorological conditions. A conceptual model of O 3 air pollution is developed based on the analysis of data obtained at Tung Chung (TC) in Hong Kong. By comparing meteorological parameters between O 3 and non-O 3 episode days, it was found that high temperatures, strong solar radiation, low wind speeds and relative humidity, northeasterly and/or northwesterly prevailing winds were favorable for the O 3 formation, while tropical cyclones were most conducive to the occurrence of O 3 episodes. Backward trajectories simulation and graphical illustration of O 3 pollution suggested that super-regional (i.e. central and eastern China) and regional (i.e. Pearl River Delta, southern China) transport was another factor that contributed to high O 3 levels in Hong Kong. The photochemical O 3 formation, generally VOC-limited in Hong Kong, was controlled by a small number of volatile organic compounds (VOCs). Furthermore, the positive matrix factorization (PMF) simulation suggested that solvent usage and vehicular emissions are the major contributors to ambient VOCs in Hong Kong. Finally, this paper presents recommendations for further O 3 research and implementation of O 3 control strategies.

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Chemical-looping Combustion (CLC) has been proposed as an energy-efficient combustion method for in situ capture of CO2. Kinetic model for parallel reactions of the CaSO4 oxygen carrier with CO in a CLC process is explored in this paper. Tests on an isothermal reaction were carried out in a Thermogravimetric Analyzer coupled with Fourier Transform Infrared spectrum (TGA-FTIR), and the instantaneous evolutions of SO2 and COS were monitored by the FTIR quantitative analysis. The reaction temperature was varied between 850 and 1050 °C, while 5-28% CO concentrations were utilized. The experiments showed that the reduction of CaSO4 by CO was a complex process, with the products of either sole CaS or both CaS and CaO depending on the reaction temperature as well as the concentration of CO reactant. The parallel reactions of CaSO4 with CO were investigated in terms of the selectivity based on the nucleation and growth model under isothermal conditions. According to the fitting results, the nucleation and growth model fit well the conversion−time data, and some of the kinetic parameters were obtained.