Development of seasonal ozone maximum reactivity scales for Beijing, China.

We designed scenarios based on urban emissions to develop a Maximum Incremental Reactivity (MIR) scale for 41 conventional volatile organic compounds (VOCs) in Beijing and quantitatively analyzed the various factors affecting MIR in urban areas. We explored the effects of updating the representative urban atmosphere used for ozone reactivity calculations by incorporating updated meteorological data, emission rates, initial condition concentrations, and VOC profile compositions. A box model equipped with the Master Chemical Mechanism (MCM) was used to localize the MIR scale for Beijing based on urban emission model inputs, and this was compared with scenarios in the United States. The MIR differences for most VOC species were minimal; however, Beijing exhibited higher MIR values for aromatic hydrocarbons in the summer, attributed to the higher emission intensity of aromatics in the city. Due to differences in meteorological conditions and emission scenarios, the MIR showed significant seasonal characteristics across different months. It is necessary to calculate independent MIR scales for different urban agglomerations under specific ozone pollution seasons and emission conditions. This study provides recommendations for the application of the MIR scale and can serve as a reference for VOC control strategies in China and other countries facing ozone pollution.