In situ production of hybrid N₂O in dust-rich Antarctic ice
Abstract
Nitrous oxide (N₂O) is a potent greenhouse gas involved in the destruction of stratospheric ozone. Past atmospheric mixing ratios of N₂O are archived in ice cores; however, the presence of in situ N₂O production in dust-rich Antarctic ice complicates their accurate reconstruction, especially during glacial periods. This production occurs in extremely cold ice and without sunlight. This study aims to understand the reaction producing N₂O in Antarctic ice by identifying the precursors and the reaction pathway. We compared the oxygen and nitrogen bulk and position-specific isotope composition of in situ N₂O in ice cores to the isotopic composition of nitrate (NO3-), a possible precursor of N₂O. The 15 N signature of NO3- is fully transferred into the central N atom (N α ) of in situ N₂O, but it is not transferred into the terminal N atom (N β ), resulting in a 50 % transfer of the 15 N signature of NO3- into the bulk 15 N isotopic composition. These findings suggest that the in situ N₂O production involves two different nitrogen precursors present in ice: the central N atom (Nα) originates from NO3- and the terminal N atom (N β ) from a different precursor not yet identified. Oxygen isotope analysis shows that NO3- cannot be the only reservoir for the O atom of in situ N₂O. Temperature, pH, and absence of sunlight in Antarctic ice point to an abiotic N-nitrosation reaction. The limiting factor of the reaction is probably associated with mineral dust and might be Fe 2+ , reducing NO3- to NO₂- or the precursor of the Nβ atom. The site preference (SP) values of in situ N₂O are highly variable between different ice cores and depend on the bulk ¹⁵N isotopic composition of N₂O, itself depending on the ¹⁵N isotopic composition of the NO3- precursor. This finding is unexpected because SP is usually determined by the production pathway through symmetric reaction intermediates that mix the N atoms in α and β positions and average out their isotopic difference. In contrast, our results provide the first evidence of a hybrid N₂O production pathway involving an asymmetric intermediate that preserves the distinct ¹⁵N signatures of two different precursors – one contributing to the Nα atom and the other to the Nβ atom.
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BibTeX
@article{soussaintjean2026situ,
title = {{In situ production of hybrid N₂O in dust-rich Antarctic ice}},
author = {Lison Soussaintjean and Jochen Schmitt and Joël Savarino and J. Andy Menking and Edward J Brook and Barbara Seth and Vladimir Lipenkov and Thomas Röckmann and Hubertus Fischer},
journal = {Biogeosciences},
year = {2026},
month = jun,
doi = {10.5194/bg-23-3939-2026},
url = {https://hal.science/hal-05789095v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - In situ production of hybrid N₂O in dust-rich Antarctic ice
AU - Lison Soussaintjean
AU - Jochen Schmitt
AU - Joël Savarino
AU - J. Andy Menking
AU - Edward J Brook
AU - Barbara Seth
AU - Vladimir Lipenkov
AU - Thomas Röckmann
AU - Hubertus Fischer
PY - 2026
DA - 2026/06/15
JO - Biogeosciences
DO - 10.5194/bg-23-3939-2026
UR - https://hal.science/hal-05789095v1
AB - Nitrous oxide (N₂O) is a potent greenhouse gas involved in the destruction of stratospheric ozone. Past atmospheric mixing ratios of N₂O are archived in ice cores; however, the presence of in situ N₂O production in dust-rich Antarctic ice complicates their accurate reconstruction, especially during glacial periods. This production occurs in extremely cold ice and without sunlight. This study aims to understand the reaction producing N₂O in Antarctic ice by identifying the precursors and the reaction pathway. We compared the oxygen and nitrogen bulk and position-specific isotope composition of in situ N₂O in ice cores to the isotopic composition of nitrate (NO3-), a possible precursor of N₂O. The 15 N signature of NO3- is fully transferred into the central N atom (N α ) of in situ N₂O, but it is not transferred into the terminal N atom (N β ), resulting in a 50 % transfer of the 15 N signature of NO3- into the bulk 15 N isotopic composition. These findings suggest that the in situ N₂O production involves two different nitrogen precursors present in ice: the central N atom (Nα) originates from NO3- and the terminal N atom (N β ) from a different precursor not yet identified. Oxygen isotope analysis shows that NO3- cannot be the only reservoir for the O atom of in situ N₂O. Temperature, pH, and absence of sunlight in Antarctic ice point to an abiotic N-nitrosation reaction. The limiting factor of the reaction is probably associated with mineral dust and might be Fe 2+ , reducing NO3- to NO₂- or the precursor of the Nβ atom. The site preference (SP) values of in situ N₂O are highly variable between different ice cores and depend on the bulk ¹⁵N isotopic composition of N₂O, itself depending on the ¹⁵N isotopic composition of the NO3- precursor. This finding is unexpected because SP is usually determined by the production pathway through symmetric reaction intermediates that mix the N atoms in α and β positions and average out their isotopic difference. In contrast, our results provide the first evidence of a hybrid N₂O production pathway involving an asymmetric intermediate that preserves the distinct ¹⁵N signatures of two different precursors – one contributing to the Nα atom and the other to the Nβ atom.
SN - 1726-4170
SN - 1726-4189
ER -