Reactivity-based strategies for photochemical ozone control in Europe

A photochemical trajectory model has been used to assess reactivity-based VOC emission control strategies for Europe by implementing a detailed speciated VOC emission inventory and a highly explicit Master Chemical Mechanism. These reactivity-based strategies envisaged that the emissions of the xylenes, trimethylbenzenes and all aromatic species could be replaced or substituted by the emission of one of a potential range of 94 organic compounds, each present in current emissions. Depending on the reactivity of the substituted VOC species, ozone mixing ratios along an east-west air parcel trajectory travelling for 5 days across northwest Europe would increase or decrease relative to a base case without substitution. In all, eight alcohols, six esters, six ketones, three ethers and an alkane, a cycloalkane and a glycol ether have been identified that give greater ozone reductions when substituting for aromatic compounds than would be given by the corresponding mass-based control strategy. It is concluded that VOC substitution strategies for the stationary sources would offer significant ozone benefits compared with simple across-the-board mass emission reduction strategies of the kind proposed by the EU CAFÉ and UN ECE LRTAP convention processes.