title: Spatiotemporal variation of ozone precursors and ozone formation in Hong Kong: Grid field measurement and modelling study.
abstract: Grid field measurements of volatile organic compounds (VOCs) covering the entire territory of Hong Kong were simultaneously carried out twice daily on 27 September 2013 and 24 September 2014, respectively, to advance our understanding on the spatiotemporal variations of VOCs and ozone (O3) formation, the factors controlling O3 formation and the efficacy of a control measure in Hong Kong. From before to after the control measure on liquefied petroleum gas (LPG) fueled vehicles, the VOCs originated from LPG vehicle exhaust deceased from 41.3±1.2μg/m(3) (49.7±1.5%) to 32.8±1.4μg/m(3) (38.8±1.7%) (p<0.05). In contrast, the contribution to VOCs made by gasoline and diesel vehicle exhaust and solvent usage increased (p<0.05). VOCs and nitric oxide (NO) in LPG source experienced the highest reductions at the roadside sites, while the variations were not significant at the urban and new town sites (p>0.05). For O3 production, LPG vehicle exhaust generally made a negative contribution (-0.17±0.06 ppbv) at the roadside sites, however it turned to a slightly positive contribution (0.004±0.038 ppbv) after the control measure. At the urban sites, although the reductions of VOCs and NO were minor (p>0.05), O3 produced by LPG vehicle significantly reduced from 4.19±1.92 ppbv to 0.95±0.38 ppbv (p<0.05). Meanwhile, O3 produced by LPG at the new town sites remained stable. The analysis of O3-precursor relationships revealed that alkenes and aromatics were the main species limiting roadside O3 formation, while aromatics were the most predominant controlling factor at urban and new town sites. In contrast, isoprene and sometimes NOx limited the O3 formation in rural environment.
authors.affiliation: Air Quality Studies, Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong.
authors.forename: X P
authors.initials: XP
authors.lastname: Lyu
authors.affiliation: Air Quality Studies, Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong.
authors.forename: M
authors.initials: M
authors.lastname: Liu
authors.affiliation: Air Quality Studies, Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong. Electronic address: ceguohai@polyu.edu.hk.
authors.forename: H
authors.initials: H
authors.lastname: Guo
authors.affiliation: Air Quality Studies, Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong.
authors.forename: Z H
authors.initials: ZH
authors.lastname: Ling
authors.affiliation: Air Quality Studies, Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Air Group, Hong Kong Environmental Protection Department, Hong Kong.
authors.forename: P K K
authors.initials: PKK
authors.lastname: Louie
authors.affiliation: Air Group, Hong Kong Environmental Protection Department, Hong Kong.
authors.forename: C W Y
authors.initials: CWY
authors.lastname: Luk
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000517:prevention & control*; D004784:Environmental Monitoring; D006723:Hong Kong; D008962:Models, Theoretical; D010126:Ozone / Q000032:analysis*; D001335:Vehicle Emissions / Q000032:analysis*; D055549:Volatile Organic Compounds / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D001335:Vehicle Emissions; D055549:Volatile Organic Compounds; D010126:Ozone
keywords: Eulerian box model; MCM; Photochemical O(3); Source apportionment; VOCs