We report the first measurements of the oxygen isotope anomaly of atmospheric inorganic nitrate from the Arctic. Nitrate samples and complementary data were collected at Alert, Nunavut, Canada (82°30′ N, 62° 19′ W) in spring 2004. Covering the polar sunrise period, characterized by the occurrence of severe boundary layer ozone depletion events (ODEs), our data show a significant correlation between the variations of atmospheric ozone (O3) mixing ratios and Δ17O of nitrate (Δ17O(NO3-)). This relationship can be expressed as: Δ17O(NO3-)/‰ = (0.15±0.03)×O3/(nmol mol-1)+(29.7±0.7) , with R2=0.70(n=12), for Δ17O(NO3-) ranging between 29 and 35‰. We derive mass-balance equations from chemical reactions operating in the Arctic boundary layer, that describe the evolution of Δ17O(NO3-) as a function of the concentrations of reactive species and their isotopic characteristics. Changes in the relative importance of O3, RO 2 and BrO in the oxidation of NO during ODEs, and the large isotope anomalies of Os and BrO, are the driving force for the variability in the measured Δ17O(NO3-). BrONO2 hydrolysis is found to be a dominant source of nitrate in the Arctic boundary layer, in agreement with recent modeling studies.
CITATION STYLE
Morin, S., Savarino, J., Bekki, S., Gong, S., & Bottenheim, J. W. (2007). Signature of Arctic surface ozone depletion events in the isotope anomaly (Δ17O) of atmospheric nitrate. Atmospheric Chemistry and Physics, 7(5), 1451–1469. https://doi.org/10.5194/acp-7-1451-2007
Mendeley helps you to discover research relevant for your work.