title: Impact of NOx reduction on long-term ozone trends in an urban atmosphere.
abstract: We investigated the relationships between ambient O(3) concentrations and the concentrations of its precursors, NO(x) and NMHC, in Osaka, Japan. The levels of O(x)' (where [O(x)']=[O(3)]+[NO(2)]-0.1x[NO(x)] where the last term accounts for primary emissions of NO(2)) were uniform within the city even in the photochemically active season. We suggested that NO oxidation by peroxy radicals was a minor contributor, and that oxidation of locally emitted NO by background O(3) in the city was the primary control on NO(2) concentrations. Ozone concentrations increased linearly from 1985 to 2002 at a rate of 0.6 ppbv/yr, even though O(x)' concentrations remained constant after the mid 1990s. The trend for O(x)' concentrations could not be explained in terms of an increase in local O(3) production, and the trend was found to reflect background O(3) concentrations in Japan. There was a clear relationship between the NO(2)/O(x)' ratio and NO(x) concentration: the ratio decreased with decreasing NO(x) concentration. As a consequence, O(3) increased with decreasing NO(x) concentration. The reduction of NO(x) emissions was deemed to be an important factor for the recent trend of increasing O(3) concentrations in Osaka City.
authors: Osaka City Institute of Public Health and Environmental Sciences, Osaka 543-0026, Japan. y-itano@city.osaka.lg.jp
authors: Yasuyuki
authors: Y
authors: Itano
authors: Hiroshi
authors: H
authors: Bandow
authors: Norimichi
authors: N
authors: Takenaka
authors: Yoshiyuki
authors: Y
authors: Saitoh
authors: Atsushi
authors: A
authors: Asayama
authors: Joji
authors: J
authors: Fukuyama
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D002947:Cities; D004784:Environmental Monitoring; D006838:Hydrocarbons / Q000032:analysis*; D007564:Japan; D009589:Nitrogen Oxides / Q000032:analysis*; D010126:Ozone / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D006838:Hydrocarbons; D009589:Nitrogen Oxides; D010126:Ozone