anomaly (117O) of atmospheric nitrate

• Main Authors: S. Morin, J. Savarino, S. Bekki, S. Gong, J. W. Bottenheim
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2006
• Subjects: Arctic; Canada; Nunavut
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.592.6160; http://hal.archives-ouvertes.fr/docs/00/32/84/85/PDF/acp-7-1451-2007.pdf

Abstract. 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 117O of nitrate (117O(NO−3)). This relationship can be expressed as: 117O(NO−3)/ ‰ = (0.15±0.03)×O3/ (nmol mol−1)+(29.7±0.7), with R2=0.70(n=12), for 117O(NO−3) ranging between 29 and 35 ‰. We derive mass-balance equations from chemical reac-tions operating in the Arctic boundary layer, that describe the evolution of 117O(NO−3) as a function of the concentrations of reactive species and their isotopic characteristics. Changes in the relative importance of O3, RO2 and BrO in the oxida-tion of NO during ODEs, and the large isotope anomalies of O3 and BrO, are the driving force for the variability in the measured 117O(NO−3). BrONO2 hydrolysis is found to be a dominant source of nitrate in the Arctic boundary layer, in agreement with recent modeling studies. 1