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.