Tracing the sources and fate of nitrogen oxides in a polar urban environment: an isotopic survey during the ALPACA campaign

• Main Authors: Albertin, Sarah, Bekki, Slimane, Savarino, Joel, Caillon, Nicolas, Richard, Soline, Brett, Natalie, Law, Kathy S., Mao, Jingqui, Simpson, William, R.
• Other Authors: TROPO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM), Université de Montpellier (UM), Geophysical Institute Fairbanks, University of Alaska Fairbanks (UAF)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2023
• Subjects: [SDU]Sciences of the Universe [physics]; Arctic; Fairbanks; Alaska
• Online Access: https://insu.hal.science/insu-04216316

International audience Urban polar areas can be subject to severe air pollution in winter, exacerbated by sharp temperature inversions very effective at trapping pollutants near to the surface. However, the formation of secondary aerosols in these cold and dark conditions and the role of the arctic boundary layer are still poorly understood. To address this issue, a major international measurement campaign was conducted in January/February 2022 in and around Fairbanks, Alaska, as part of the CASPA (Climate-relevant Aerosol Sources and Processes in the Arctic) and ALPACA (ALaskan Pollution And Chemical Analysis) projects. Among the various atmospheric chemical and physical measurements, gaseous and particulate samples were collected and subjected to isotopic analyses in order to identify the sources of nitrogen oxides (NOx) emissions and understand how they are oxidized to atmospheric nitrate (NO3-).The use of stable isotopes has demonstrated its ability to provide information relevant for tracing emission sources, individual chemical processes and budgets of atmospheric trace gases. Of particular interest is the propagation of the ozone oxygen-17 anomaly (Δ17O) into the reactive nitrogen cycle which has led to a better understanding of NO3- formation pathways in various environments. However, there remain some difficulties to interpret NO3- isotopic composition, mainly due to the lack of clearly established understanding about the link between the oxygen and nitrogen isotopic composition of the NOx and the chemical state of the atmosphere.Here, we present the results of the multi-isotope composition of atmospheric NO2 collected on denuder tubes (n = 33) in downtown Fairbanks. We find significant oscillations in Δ17O and δ15N values. The maximum Δ17O value is recorded during the day (39.7 ‰), and the minimum value at night (3.6 ‰). Δ17O values are significantly different during the day and night, with a mass-weighted mean of 30.8 and 11.5 ‰, respectively. Conversely, δ15N values show no diurnal trend and range ...