Mechanism reduction for tropospheric chemistry - Butane oxidation

A detailed butane oxidation mechanism for the troposphere was reduced using objective methods. The reductions of this large scheme have been based on sensitivity analysis over a wide range of atmospheric conditions, characterised by extremely low, intermediate and high [NOx]. The quasi-steady-state approximation (QSSA) was applied to reduce further the number of differential (rate) equations needed to describe the kinetics. Significant simplifications were achieved leading to reductions in the number of differential equations of a factor of 6-10, depending on the conditions. The reductions lead to a greater transparency in the mechanism and to a more facile identification of key reaction routes. This facility is demonstrated via a discussion of secondary routes to HO2 via carbonyl photolysis.