Correlation of ozone with NO_y in photochemically aged air

Abstract

During the summer of 1988, measurements of photochemical trace species were made at a coordinated network of seven rural sites in the eastern United States and Canada. At six of these sites concurrent measurements of ozone and the sum of the reactive nitrogen species, NOy, were made, and at four of the sites a measure for the reaction products of the NO x oxidation was obtained. Common to all sites, ozone, in photochemically aged air during the summer, shows an increase with increasing NOy levels, from a background value of 30-40 parts per billion by volume (ppbv)at NOy mixing ratios below 1 ppbv to values between 70 to 100 ppbv at NOy levels of 10 ppbv. Ozone correlates even more closely with the products of the NOx oxidation. The correlations from the different sites agree closely at mixing ratios of the oxidation products below 5 ppbv, but systematic differences appear at higher levels. Variations in the biogenic hydrocarbon emissions may explain these differences. IntroductionElevated and potentially harmful levels of ozone are being found in many rural areas of North America during summer. Daily maximum 03 levels measured in rural areas are often comparable to those found in urban areas and daily average levels can exceed urban levels. There is substantial evidence from field measurements and model calculations that most of this ozone is being produced photochemically from ozone precursors emitted within the region [Research Triangle Institute, 1975; Vukovich et al., 1977Vukovich et al., , 1985Cleveland et al., 1977;Spicer et al., 1979;Wolff and Lioy, 1980;Fehsenfeld et al., 1983;Kelly et al., 1984;Liu et al., 1987]. A similar situation appears to exist for western Europe [Cox et al., 1975;Guicherit and Van Dop, 1977;Hov, 1984]. The photochemical processes responsible for these high levels are thought to be quite similar to the processes that operate in urban photochemical smog but with important differences. In

Intercontinental Transport of Air Pollution: Will Emerging Science Lead to a New Hemispheric Treaty?

“…Observation-based studies of O3, its precursors, and other tracers of continental emissions provide useful information on background levels as well as evidence of intercontinental influence on these concentrations (2,13,(18)(19)(20)(21). In fact, O3 observations at mountain sites in Europe indicate that human activities over the past century have at least doubled tropospheric O3 concentrations (22).…”

Ozone photochemistry in boreal biomass burning plumes

“…Since NO y is representative of all NO x emissions, NO z provides a measure of the number of NO x molecules that have undergone photo-oxidation. Several studies have shown that the O 3 abundance in polluted air masses is linearly related to the abundance of NO z (e.g., Trainer et al, 1993;Kleinman, 2000). The enhancement of O 3 abundance relative to NO z (i.e.…”

Nitrogen dioxide measurement by cavity attenuated phase shift spectroscopy (CAPS) and implications in ozone production efficiency and nitrate formation in Beijing, China

“…The OPE x can be derived from the regression slopes of correlations between O x and NO z [Kleinman et al, 1994;Trainer et al, 1993]. Therefore, the accuracy of NO 2 measurement plays an important role in the calculation of OPE x by influencing the quantification of O x and NO z .…”

“…Since the oxidants of NO x can be removed from the O 3 -productionreaction system, Liu et al [1987] defined the number of molecules of O 3 formed per NO x as O 3 production efficiency of NO x (OPE x ), which has been used as an important indicator in studying O 3 chemistry. Trainer et al [1993] and Kleinman et al [1994] found better correlations between O 3 and the oxidation products of NO x , i.e., NO z (= NO y À NO x ) than the sum of reactive nitrogen species, NO y , in the photochemically aged air, based on which the OPE x was revised as Δ[O 3 + NO 2 ] / Δ[NO z ]. Therefore, accurate measurements of NO y and NO x are of importance to understand the formation mechanism of O 3 production, and hence to make the corresponding control strategies for mitigation of photochemical smog.…”