Potential Strong Inhibition on Ozone Production Sensitivity by Particle Uptake

The accurate identification of ozone (O-3) production sensitivity is central to developing O-3 pollution control policies. It is determined by the relative ratio of the radical loss to the total primary radical production. However, such radical losses in the traditional sensitivity analysis typically rely on nitrogen oxide (NOx) sinks while ignoring particle uptake (collisions between compounds in the gas phase and condensed phases that result in irreversible uptake due to chemical reactions). Therefore, we combine NOx and particle uptakes to optimize peroxy radical loss estimates and thus analyze the relative sensitivity. We also assess the absolute responses of precursor reduction to O-3 production. Such relative and absolute sensitivity analysis is applied to measurements in Chun'an, a county in China, where volatile organic compounds (VOCs) and NOx are both rich. Consequently, the relative sensitivity analysis presents that the dominant precursor for O-3 production sensitivity shifts from volatile organic compounds (VOCs) in the morning and evening to NOx in the afternoon, the main driver of which is related to NO depletion. In contrast, the absolute sensitivity analysis confirms that VOCs persistently determine the diurnal ozone production sensitivity. Moreover, they both show that particle uptake does not change the regime classification of O-3 production sensitivity (i.e., VOC- or NOx-sensitive regime) but potentially has a strong inhibition on the sensitivity magnitude (within 16% and 38% for VOC- or NOx-sensitive regimes, respectively). Our results partly explain more insensitive O-3 production measurements than those suggested by traditional sensitivity analyses, which has important implications for synergistic controls on O-3 and fine particulate matter pollution.

Automated summary

The accurate identification of ozone (O-3) production sensitivity is crucial for developing pollution control policies. This study combines nitrogen oxide (NOx) and particle uptakes to optimize peroxy radical loss estimates and analyze the relative sensitivity in Chun'an, China. The results show that the dominant precursor for O-3 production sensitivity shifts from volatile organic compounds (VOCs) in the morning and evening to NOx in the afternoon.