title: On the relationship between ozone and its precursors in the Pearl River Delta: application of an observation-based model (OBM).
abstract: OBJECTIVE
  Photochemical smog, characterized by high concentrations of O(3) and fine particles, is of great concern in the urban areas, in particular megacities and city clusters like the Pearl River Delta.
  
  
  RESULTS
  Ambient ozone (O(3)) and its precursors were simultaneously measured at two sites in the Pearl River Delta, namely, Wan Qing Sha (WQS) in Guangzhou and Tung Chung (TC) in Hong Kong, from 23 October to 01 December 2007 in order to explore their potential relationship. Eight high O(3) episode days were identified at WQS and two at TC during the sampling campaign, indicating a more serious O(3) pollution in Guangzhou than in Hong Kong. An observation-based model was employed to determine the ozone-precursor relationship. At both sites, O(3) production was found to be volatile organic compound (VOC)-limited, which is consistent with previous observations. Anthropogenic hydrocarbons played a key role in O(3) production, while reducing nitric oxide emissions aided the buildup of O(3) concentrations. Among VOC species, the summed relative incremental reactivity (RIR) of the top 12 compounds accounted for 89% and 85% of the total RIR at WQS and TC, respectively, indicating that local photochemical O(3) formation can be mainly attributed to a small number of VOC species.
  
  
  CONCLUSIONS
  A large increment in both simulated HO(2) and O(3) concentrations was achieved with additional input of hourly carbonyl data. This suggested that apart from hydrocarbons, carbonyls might significantly contribute to the O(3) production in the Pearl River Delta.
authors.affiliation: Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong.
authors.forename: Hairong
authors.initials: H
authors.lastname: Cheng
authors.forename: Hai
authors.initials: H
authors.lastname: Guo
authors.forename: Xinming
authors.initials: X
authors.lastname: Wang
authors.forename: Sam M
authors.initials: SM
authors.lastname: Saunders
authors.forename: S H M
authors.initials: SH
authors.lastname: Lam
authors.forename: Fei
authors.initials: F
authors.lastname: Jiang
authors.forename: Tijian
authors.initials: T
authors.lastname: Wang
authors.forename: Aijun
authors.initials: A
authors.lastname: Ding
authors.forename: Shuncheng
authors.initials: S
authors.lastname: Lee
authors.forename: K F
authors.initials: KF
authors.lastname: Ho
mesh_terms: D000392:Air Movements; D000393:Air Pollutants / Q000032:analysis*; D001272:Atmosphere / Q000737:chemistry*; D002681:China; D004784:Environmental Monitoring; D007700:Kinetics; D008956:Models, Chemical; D010083:Oxidants, Photochemical / Q000032:analysis*; D010126:Ozone / Q000032:analysis*; D052638:Particulate Matter / Q000032:analysis; D012621:Seasons; D055549:Volatile Organic Compounds / Q000032:analysis
chemical_list: D000393:Air Pollutants; D010083:Oxidants, Photochemical; D052638:Particulate Matter; D055549:Volatile Organic Compounds; D010126:Ozone