Evaluation of two MCM v3.1 alkene mechanisms using indoor environmental chamber data

Photo-oxidation experiments on propene-NOx-air and 1-butene-NOx-air mixtures were performed in the CSIRO indoor environmental chamber. These data were used to test the alkene sub-mechanisms from the Master Chemical Mechanism version 3.1 (MCM v3.1). A comparison of measured and modelled propene-NOx data showed that the mechanisms required the inclusion of O(3P)+parent alkene reactions in order to adequately model the results over a wide range of VOC/NOx ratios. Sensitivity studies were performed on propene-NOx and 1-butene-NOx simulations to determine the effect of uncertainties in the chamber parameters and key photolysis rates on the O3, and NOx profiles. The low VOC/NOx propene simulations were sensitive to the formaldehyde (HCHO) photolysis channel that produces HO2 radicals and to the presence of O(3P) reactions. For the higher VOC/NOx propene simulations, the O3, and NOx results were more sensitive to small changes in the initial HONO and NO2 concentrations.