Rate coefficients for the reactions of OH radical and ozone with a series of unsaturated esters

Abstract

Unsaturated esters are emitted into the atmosphere from biogenic and anthropogenic sources. Their atmospheric degradation through reactions with the main atmospheric oxidants (OH, O3, NO3, Cl) contributes to the formation of important secondary pollutants. Kinetic and mechanistic parameters for these reactions are highly required in order to estimate the atmospheric lifetimes and hence the impacts of these important classes of VOCs. In this study, the gas-phase rate coefficients of the reaction of OH radical and O3 with a series of unsaturated esters are reported. The esters investigated include methyl methacrylate (MMA), ethyl methacrylate (EMA), n-propyl methacrylate (nPMA), n-butyl methacrylate (nBMA), iso-propyl methacrylate (iPMA), iso-butyl methacrylate (iBMA) and fully deuterated methyl methacrylate (MMA-D8). The measurement combined the pulsed laser photolysis-laser induced fluorescence for the OH studies in the temperature range 257–376K and a 7300 L atmospheric simulation chamber for the O3 reactions at 291 ± 2K. This work provides the first temperature-dependence studies of OH reaction with EMA, nPMA, iPMA and iBMA and of O3 reaction with nPMA, iPMA and iBMA at room temperature. The obtained data are discussed in terms of the structure reactivity relationships and their atmospheric consequences by estimating the atmospheric lifetimes for the studied esters with respect to O3, OH radical and other oxidant in the troposphere.