Investigation of the ozone formation potential for ethanol using a smog chamber

Abstract

The ozone formation reactivity of ethanol has been studied using chamber experiments and model simulations. The computer simulations are based on the MCM v3.1 mechanism with chamber-dependent auxiliary reactions. Results show that the MCM mechanism can well simulate C₂H₅OH-NO _x chamber experiments in our experimental conditions, especially on ozone formation. C₂H₅OH-NO _x irradiations are less sensitive to relative humidity than alkane species under our experimental conditions. In order to well simulate the experiments under high relative humidity conditions, inclusion of N₂O₅+H₂O=2HNO₃ in the MCM mechanism is necessary. Under C₂H₅OH-limited conditions, the C₂H₅OH/NO _x ratio shows a positive effect on d(O₃-NO)/dt and RO₂+HO₂. High C₂H₅OH/NO _x ratios enhance the production of organoperoxide radical and HO₂ radical concentrations, which leads to a much quicker accumulation of ozone. By using ozone isopleths under typical scenarios conditions, the actual ozone formation ability of ethanol is predicted to be 2.3–3.5 part per billion (ppb) in normal cities, 3.5–146 ppb in cities where ethanol gas are widely used, and 0.2–3.2 ppb in remote areas. And maximum ozone formation potential from ethanol is predicted to be 4.0–5.8 ppb in normal cities, 5.8–305 ppb in cities using ethanol gas, and 0.2–3.8 ppb in remote areas.