The use of NO_y, H₂O₂, and HNO₃ as indicators for ozone‐NO_x‐hydrocarbon sensitivity in urban locations

Abstract

Correlations are presented between model predictions for O3‐NOx‐hydrocarbon sensitivity and afternoon concentrations of four “indicator species”: NOy, O3/(NOy‐NOx), HCHO/NOy, and H2O2/HNO3. The indicator species correlations are based on a series of photochemical simulations with varying rates of anthropogenic and biogenic emissions and meteorology. Hydrocarbon‐sensitive chemistry in models is shown to be linked to afternoon NOy > 20 ppb, O3/(NOy ‐ NOx) < 7, HCHO/NOy < 0.28, and H2O2/HNO3 < 0.4. Lower NOy and higher ratios correspond with NOx‐sensitive ozone. The correlation between NOx‐hydrocarbon sensitivity and indicator species remains, even when model emission rates and hydrocarbon/NOx ratios are changed by a factor of 2. Methods are developed for evaluating the goodness of fit between model NOx‐hydrocarbon sensitivity and indicator values. Ozone chemistry is also analyzed in terms of fundamental properties of odd hydrogen, and theoretical criteria for the transition between NOx‐ and hydrocarbon‐sensitive regimes are derived. A theoretical correlation between O3 and H2O2 + NOy ‐ NOx is developed as a way to extend rural O3‐NOy correlations into urban locations. Measured indicator values during pollution events in Los Angeles, Atlanta, and rural Virginia are used to illustrate the range of observed values under different environmental conditions.

Empirical ozone isopleths as a tool to identify ozone production regimes

“…Using an analysis of the ozone production efficiency and indicator variables (cf. also [Sillman, 1995]), they could show that ozone production in Verzago was rather ROG-sensitive in these cases.…”

“…Our interpretation is that ozone isopleth plots derived from measured values of ozone and it's precursors (reactivity weighted hydrocarbons (=ROGs) and either NOx or NOz) are suitable to identify the sensitivity of ozone production at one given site. In a previous paper [Thielmann et al, submitted], we analyzed the sensitivity of ozone production using the indicator variables introduced by [Sillman, 1995]. Indicator variables are derived from measured values of photochemical products.…”

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

“…[20] The daily OPE x in this study is always lower than the value suggested for O 3 -VOC sensitivity (OPE x < 7, [Sillman, 1995]), indicating that the ozone production in summer in Beijing is VOC-limited. Therefore, measures to control VOC emissions in Beijing would be effective to reduce O 3 levels.…”

Air chemistry during the 1995 SOS/Nashville intensive determined from level 2 network

“…3. The comparison of the O•4NOy ratios to model simulations [Sillman, 1995] suggests that the rural and suburban locations are in a NOx -sensitive oxidant t•)nnation chemistry regime while the urban location (downtown Nashville) is in a chemistry regime that is sensitive to both NOx and VOC concentrations.…”