Observation-Based Estimations of Relative Ozone Impacts by Using Volatile Organic Compounds Reactivities

The incremental reactivity and measured volatile organic compound (VOC) concentrations have been widely used to estimate ozone impacts of VOC emissions. However, these studies usually use the maximum incremental reactivity (MIR) that deviated from the real airshed conditions and ignore the consumption of VOCs due to photochemical reactions between emissions and measurement. This study proposed that ozone impacts should be derived by multiplying incremental reactivities based on real airshed conditions (R-IR) by ambient VOC concentrations corrected by kinetic reactivity. This method reflected the ambient photo-oxidation condition and the chemical decay of VOCs in the period between their emissions and measurement. This study derived the R-IR scales and estimated the ozone impact of 79 VOCs in the summer in the megacity Shanghai and small city Taian in eastern China. It was found that alkenes and aromatics had the highest ozone impacts in the megacity Shanghai and small city Taian, respectively. The R-IR values in those two Chinese cities showed significant consistency with U.S. MIR, indicating that ozone in eastern China could be generally VOC limited.