Reactive oxidized nitrogen speciation and partitioning in urban and rural New York State

Abstract

This study examined reactive oxidized nitrogen (NO_y) speciation and partitioning at one urban site, Queens College (QC) in New York City, and one rural site, Pinnacle State Park (PSP) in Addison, New York (NY) from September 2016 to August 2018 and June 2016 to September 2018, respectively. Oxides of nitrogen (NO_x), nitric acid (HNO₃), particle nitrate (pNO₃), peroxy nitrates (PNs), alkyl nitrates (ANs), and NO_y measurements were made at both sites. Across all seasons at QC, the median NO_x, HNO₃, pNO₃, PNs, ANs, and NO_y concentrations were 10.99, 0.49, 0.24, 0.62, 0.94, and 13.95 parts per billion (ppb), respectively. All-season median percent contributions of NO_x, HNO₃, pNO₃, PNs, and ANs to the total NO_y at QC were 77, 4, 2, 5, and 7%, respectively. Therefore, the sum of the individual NO_y species (NO_yi ≈ NO_x + HNO₃ + pNO₃ + PNs + ANs) accounted for 95% of the total NO_y at QC, which was well within measurement uncertainties. At PSP, the median NO_x, HNO₃, pNO₃, PNs, ANs, and NO_y concentrations were 0.65, 0.16, 0.12, 0.13, 0.18, and 1.56 ppb, respectively, over all seasons. The median percent contributions of NO_x, HNO₃, pNO₃, PNs, and ANs to NO_y over all seasons at PSP were 42, 10, 8, 9, and 12%, respectively. NO_yi comprised 81% of NO_y across all seasons at PSP, and deviations from 100% closure were generally within measurement uncertainties. Since both datasets yielded NO_y budget closure results that were either fully or largely explained by the measurement uncertainties, the observed NO_yi is likely representative of ambient NO_y in urban and rural New York. The results have implications for understanding the fate of NO_x emissions and their impact on local and regional air quality in urban and rural New York State.Implications: Continuous speciated and total reactive oxidized nitrogen (NO_y) measurements were made in urban and rural New York from 2016 to 2018. Different NO_y species have contrasting effects on the chemistry that impacts ozone (O₃) and fine particulate matter (PM_2.5) formation and concentrations. Since O₃ and PM_2.5 are regulated pollutants that have proven difficult to control, the results have implications for current and future air quality policy.