Airborne observations of peroxy radicals during the EMeRGe campaign in Europe

• Published in: Atmospheric chemistry and physics Vol. 23; no. 13; pp. 7799 - 7822
• Main Authors: George, Midhun, Andrés Hernández, Maria Dolores, Nenakhov, Vladyslav, Liu, Yangzhuoran, Burrows, John Philip, Bohn, Birger, Förster, Eric, Obersteiner, Florian, Zahn, Andreas, Harlaß, Theresa, Ziereis, Helmut, Schlager, Hans, Schreiner, Benjamin, Kluge, Flora, Bigge, Katja, Pfeilsticker, Klaus
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 14.07.2023; Copernicus Publications
• Subjects: Actinometry; Aerosols; Air masses; Aircraft; Altitude; Approximation; Coefficients; Free radicals; Gases; High altitude; Mathematical analysis; Measurement techniques; Megacities; Mixing ratio; Nitrates; Nitric acid; Nitric acids; Nitric oxide; Nitrogen; Nitrogen dioxide; Nitrous acid; Organic compounds; Organic nitrates; Outdoor air quality; Outflow; Oxidation; Ozone; Peroxy radicals; Photochemistry; Photolysis; Plumes; Pollution; Pollution dispersion; Remote sensing; Research aircraft; Smog; Trace gases; VOCs; Volatile organic compounds; Water vapor; Water vapour; Europe
• ISSN: 1680-7324; 1680-7316; 1680-7324
• DOI: 10.5194/acp-23-7799-2023

In this study, airborne measurements of the sum of hydroperoxyl (HO.sub.2) and organic peroxy (RO.sub.2) radicals that react with nitrogen monoxide (NO) to produce nitrogen dioxide (NO.sub.2 ), coupled with actinometry and other key trace gases measurements, have been used to test the current understanding of the fast photochemistry in the outflow of major population centres. The measurements were made during the airborne campaign of the EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales) project in Europe on board the High Altitude and Long Range Research Aircraft (HALO). The measurements of RO2â on HALO were made using the in situ instrument Peroxy Radical Chemical Enhancement and Absorption Spectrometer (PeRCEAS). RO2â is to a good approximation the sum of peroxy radicals reacting with NO to produce NO.sub.2 . RO2â mixing ratios up to 120 pptv were observed in air masses of different origins and composition under different local actinometric conditions during seven HALO research flights in July 2017 over Europe.