The role of nitrogen oxides in nonurban ozone formation in the planetary boundary layer over n America, w europe and adjacent areas of ocean

Abstract

The status of knowledge on photochemical ozone formation and the effects of nitrogen oxides and peroxyacyl nitrates on such formation have been evaluated. The literature is reviewed on 1. (a) nonurban ozone and nitrogen oxide concentration distributions, (b) ozone lifetimes, (c) nitrogen oxide lifetimes, and (d) ozone formation in plumes as related to nitrogen oxide. The modeling approaches applied to ozone formation 1. (a) with urban plumes, 2. (b) power plant plumes, 3. (c) high pressure systems, and 4. (d) during longerrange transport of ozone are discussed. In addition, models concerned with the contributions to ozone formation associated with reactions of natural hydrocarbons and nitrogen oxide near ground level and photochemical ozone formation associated with reactions of carbon monoxide and of more persistent organic species with nitrogen oxides in the free troposphere are considered. It is concluded that urban plumes are major contributors to elevated ozone concentrations measured at nonurban locations, particularly during the passage of high pressure systems. Ozone can survive at significant concentration levels for more than one day of transport. However, the evidence for multiday ozone transport is to a large extent associated with transport over water. Ozone formation during the first day of transport does not appear to be limited by the availability of nitrogen oxides. However, it is likely that multiday formation and transport of ozone within the boundary layer is limited in duration because of the relatively short lifetimes of nitrogen oxides and peroxyacyl nitrates. Photochemical formation of ozone in the free troposphere may be an important contributor to longer-time average ozone concentrations in rural areas. These free tropospheric processes depend in part on anthropogenic sources of precursors and are especially sensitive to the vertical distribution of nitrogen oxides in the atmosphere.