Evolution of NO<sub><i>x</i></sub> in the Denver Urban Plume during the Front Range Air Pollution and Photochemistry Experiment

Abstract

Abstract.As NO x (NO x ≡NO+NO 2 ) is transported away from cities, it undergoes photochemical oxidation to peroxynitrates (RO 2 NO 2 , ΣPNs), alkyl nitrates (RONO 2 , ΣANs), and nitric acid (HNO 3 ). These higher oxide species each have different lifetimes to permanent removal or conversion back to NO x , resulting in nitrogen oxide chemistry that evolves as plumes are transported away from cities. Here, observations from the Front Range Air Pollution and Photochemistry Experiment (FRAPPÉ) are used to describe the evolution of NO x and NO y (NO y ≡NO x +ΣPNs+ΣANs+HNO 3 +…) as the Denver urban 15 plume flows outward from the city center. We evaluate the chemistry, dilution, and deposition rates in the plume to provide numerical constraints on the NO x and NO y,i lifetimes. We find that plume dilution with background air occurs with a lifetime of 3.5 hours. NO x concentrations decrease more rapidly with a lifetime to chemical loss and dilution of 2 hours in the near field of the city center. NO y has an effective lifetime of 3 hours and due to a combination of HNO 3 deposition and dilution.The results provide a useful test of conceptual and numerical models of chemistry during the evolution of urban plumes. 20Atmos. Chem. Phys. Discuss., https://doi

Acyl Peroxy Nitrates Link Oil and Natural Gas Emissions to High Ozone Abundances in the Colorado Front Range During Summer 2015

“…For all of our simulations, the initial NO 2 /NO ratio was ~2, but the NO 2 /NO ratio adjusts within 2–3 time steps (10 min each) to a level consistent with the average ratio of the BAO field measurements (~5). OH concentrations in all simulations were also similar to those measured in the NFRMA during the Front Range Air Pollution and Photochemistry Experiment aircraft campaign in summer 2014 (Ebben et al, ). Additionally, we tested the sensitivity of each simulation to NO x by running each VOC mixture with a series of five NO x scaling factors: 0.25, 0.5, 1, 2, and 3.…”

Seasonality, sources and sinks of C1–C5 alkyl nitrates in the Colorado Front Range

“…We use an OH range of (1-3) × 10 6 molecule cm -3 for winter 2011 based on co-located, simultaneous OH measurements (Kim et al, 2014). We use an average daytime range of (4-8) × 10 6 molecule cm -3 for the summer 2015 campaign based on aircraft OH measurements from summer 2014 in the Northern Colorado Front Range (Ebben et al, 2017). We use (2-5) × 10 6 OH molecule cm -3 for the spring 2015 campaign.…”