Nitrogen isotopes (δ15N) and oxygen isotope anomalies (Δ17O, δ18O) in atmospheric nitrogen dioxide : a new perspective for isotopic constraints on oxidation and aerosols formation processes
Résumé
Urban polar areas can be subject to severe pollution in winter, linked to sharp temperature inversions that trap pollutants close to the surface. However, the formation of secondary aerosols (sulphates, nitrates, organics) in these cold and dark conditions and the role of the Arctic boundary layer are still poorly understood. To address this issue, an intensive international measurement campaign, called ALPACA (ALaskan Pollution And Chemical Analysis), will be conducted in January/February 2021 in and around Fairbanks, Alaska. Among the various atmospheric chemical and physical measurements, gas and particles collections will be carried out for multiple isotopic analyses.
The use of stable isotopes over the past decades 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 distinctive oxygen-17 anomaly (Δ17O) into the reactive nitrogen cycle which has led to a better understanding of nitrate formation pathways in various environments. However, there remain some difficulties to interpret the isotopic composition of the nitrate, mainly due to the lack of clearly established understanding about the link between the oxygen and nitrogen isotopic composition of the nitrogen oxides (NOx= NO + NO2), the precursors of nitrate in the atmosphere, and the chemical state of the atmosphere.