title: Characteristics of surface ozone at an urban site of Xi'an in Northwest China.
abstract: Surface ozone concentrations in Xi'an, China were monitored from March 23, 2008 to January 12, 2009 using the Model ML/EC9810 ozone analyzer. The daily average O(3) ranged from <1 ppb to 64.2 ppbv with an annual average of 16.0 ppbv. The seasonal average of O(3) in summer (32.5 ppbv) was more than 10 times higher than that in winter (3.0 ppbv). A significant positive correlation was found between ozone concentration and ambient temperature, indicating that the intensity of solar radiation was one of the several major factors controlling surface ozone production. Using the NOAA HYSPLIT 4 trajectory model, the three longest O(3) pollution episodes were found to be associated with the high biogenic volatile organic carbon (BVOC) emissions from the vegetation of Qinling Mountains. No significant weekday and weekend difference in O(3) levels was detected due to the non-significant change in NO(x) emissions. O(3) depletion by NO emission directly emitted from vehicles, low oxygenated VOC concentrations, and low-level solar radiation caused by high aerosol loading all contributed to the low levels of O(3) found in Xi'an compared to other cities and rural areas.
authors.affiliation: Department of Environmental Sciences and Engineering, Xi'an Jiaotong University, Xi'an, China.  zxshen@mail.xjtu.edu.cn.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.forename: Zhenxing
authors.initials: Z
authors.lastname: Shen
authors.forename: Junji
authors.initials: J
authors.lastname: Cao
authors.forename: Leiming
authors.initials: L
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Jianjun
authors.initials: J
authors.lastname: Li
authors.forename: Suixin
authors.initials: S
authors.lastname: Liu
authors.forename: Yufan
authors.initials: Y
authors.lastname: Sun
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000706:statistics & numerical data; D002681:China; D002947:Cities / Q000706:statistics & numerical data; D004784:Environmental Monitoring; D008956:Models, Chemical; D009589:Nitrogen Oxides / Q000032:analysis; D010126:Ozone / Q000032:analysis*; D012621:Seasons; D055549:Volatile Organic Compounds / Q000032:analysis
chemical_list: D000393:Air Pollutants; D009589:Nitrogen Oxides; D055549:Volatile Organic Compounds; D010126:Ozone