Nitrite to Nitrate Spontaneous Oxidation in Suspended Aqueous Droplets
Abstract
We report experimental evidence of the spontaneous formation of NO3− in suspended aqueous droplets containing NO2−, driven by hydroxyl radicals and NO2 produced by the intrinsic properties of the air-water interface. This oxidation of nitrite anions is observed in single droplets of micrometer size using optical tweezers, with the υ1(N–O) Raman mode of NO3− detected around 1,050 cm−1 as a function of time. The influence of pH, particle size, initial NO2− concentration, and different gaseous atmospheres (air and nitrogen) has been systematically studied. In sharp contrast, no bulk oxidation was observed under similar conditions. By using KSCN as an OH radical scavenger, we demonstrate the critical role of hydroxyl radicals generated at the air-water interface in nitrate formation. These experiments suggest that a particle effect is indeed at play, leading to the spontaneous formation of NO3− through the interaction of NO2 and OH radicals.
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BibTeX
@article{meroni2026nitrite,
title = {{Nitrite to Nitrate Spontaneous Oxidation in Suspended Aqueous Droplets}},
author = {C. Meroni and Adrien Gandolfo and C. George},
journal = {Geophysical Research Letters},
year = {2026},
month = oct,
doi = {10.1029/2025gl120957},
url = {https://hal.science/hal-05629961v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Nitrite to Nitrate Spontaneous Oxidation in Suspended Aqueous Droplets
AU - C. Meroni
AU - Adrien Gandolfo
AU - C. George
PY - 2026
DA - 2026/10/09
JO - Geophysical Research Letters
DO - 10.1029/2025gl120957
UR - https://hal.science/hal-05629961v1
AB - We report experimental evidence of the spontaneous formation of NO3− in suspended aqueous droplets containing NO2−, driven by hydroxyl radicals and NO2 produced by the intrinsic properties of the air-water interface. This oxidation of nitrite anions is observed in single droplets of micrometer size using optical tweezers, with the υ1(N–O) Raman mode of NO3− detected around 1,050 cm−1 as a function of time. The influence of pH, particle size, initial NO2− concentration, and different gaseous atmospheres (air and nitrogen) has been systematically studied. In sharp contrast, no bulk oxidation was observed under similar conditions. By using KSCN as an OH radical scavenger, we demonstrate the critical role of hydroxyl radicals generated at the air-water interface in nitrate formation. These experiments suggest that a particle effect is indeed at play, leading to the spontaneous formation of NO3− through the interaction of NO2 and OH radicals.
SN - 0094-8276
SN - 1944-8007
ER -