Contribution of VOC sources to photochemical ozone formation and its control policy implication in Hong Kong

Since volatile organic compounds (VOCs) are important precursors of ozone (O3), identification and quantification of their emission sources are prerequisite for the formulation and implementation of O3 pollution control policies. In this study, seven major sources of VOCs were identified and their contributions to photochemical O3 formation were evaluated at an urban site (TW) in Hong Kong by the combined application of the positive matrix factorization (PMF) model and the observation based model (OBM). The relative incremental reactivity (RIR)-weighted values, which considered both the reactivity and abundance of VOCs, suggested that paint and sealant solvents, diesel exhaust and liquefied petroleum gas (LPG) usage were the key contributors to O3 formation. Among the identified sources, xylenes and ethylbenzene in paint and sealant solvents, toluene in gasoline exhaust, butanes, ethene, propene and propane in LPG usage and n-butane and ethene in diesel exhaust made significant contributions. Sensitivity analysis on the basis of relative O3 reduction efficiency (RORE), using the reduction of VOCs from 10% to 90% as input, indicated that the O3 reduction was the most effective when the identified VOC sources and the major species from these sources were cut by specific percentages. The findings provide valuable insights into the formulation and implementation of VOCs and O3 control strategies in Hong Kong.