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Understanding the fate of oxides of nitrogen (NOx) is important due to their roles in forming ozone (O3) and fine particulate matter (PM2.5). This study examines the importance of surface-enhanced renoxification as a NOx source at rural and urban sites in New York (NY) during selected spring/summer and winter case study periods in 2016–2018. The rural site was Pinnacle State Park (PSP) in Addison, NY, and the urban site was Queens College (QC) in New York City. Observation-based renoxification rates (RRs) were estimated at both sites, and the contributions from these RRs were compared to the ambient NOx. Renoxification due to surface nitrate (= nitric acid (HNO3) + particle nitrate (pNO3)) photolysis at PSP was likely a minor NOx source during summer and a non-negligible NOx source during winter. However, during photochemically active case study days at PSP, modeling analyses found that renoxification only had a noticeable effect on O3 production at low O3 production rates, suggesting that renoxification has little influence on high O3 and O3 exceedance events. At QC, renoxification was a negligible contributor to the ambient NOx during spring, summer, and winter, confirming that NOx in New York City is almost entirely controlled by anthropogenic NOx emissions.
Ninneman et al. (Fri,) studied this question.