Ozone Production Sensitivity to NOx and VOCs in the New York City Airshed During LISTOS

Despite significant reductions in ozone precursors in recent decades, the New York-New Jersey-Connecticut area currently surpasses the EPA’s national air quality standard for ozone. Using air samples collected from the Long Island Sound Tropospheric Ozone Study (LISTOS) in the late spring and summers of 2017-2019, we calculate ozone production (PO₃) and test its sensitivity to changes in initial concentrations of ozone precursors using a 0-D box model. We find characteristic diurnal and seasonal cycle of PO₃ due to changes in observed NO₂ and VOCs. We often find PO₃ to be VOC limited in downtown NYC, along the Connecticut coast, and central Connecticut. In these samples PO₃ is most sensitive to either biogenic VOC or anthropogenic alkenes depending on time of day and season. We also explore the relationships of different metrics for photochemical regime classification (i.e, NO_x or VOC limited PO₃).

We further compare PO₃ calculations using the near explicit Master Chemical Mechanism (MCMv3.3.1) to Carbon Bond 6 revision 2 (CB6r2) for a more direct link to regulatory air quality models. Modeled PO₃ is 25% faster in MCMv3.3.1, due largely to the speciation of VOC and organic peroxy radicals. This finding has implications for how condensed mechanisms in regional and global chemical transport models might respond to changing VOC distributions in urban areas.