Abstract. We report evidence for ice catalyzing N 2 O 5 heterogeneous hydrolysis from a study conducted near Fairbanks, Alaska in November 2007. Mixing ratios of N 2 O 5 , NO, NO 2 , and ozone are reported and are used to determine steady state N 2 O 5 lifetimes. When air masses are subsaturated with respect to ice, the data show longer lifetimes (≈20 min) and elevated N 2 O 5 levels, while ice-saturated air masses show shorter lifetimes (≈6 min) and suppressed N 2 O 5 levels. We also report estimates of aerosol surface area densities that are on the order of 50 µm 2 /cm 3 , a surface area density that is insufficient to explain the rapid losses of N 2 O 5 observed in this study, reinforcing the importance of other reactive surfaces such as ice. Consideration of two possible responsible types of ice surfaces, the snowpack and suspended ice particles, indicates that both are reasonable as possible sinks for N 2 O 5 . Because ice-saturated conditions are ubiquitous in high latitudes, ice surfaces are likely to be a key loss of N 2 O 5 , leading to nitric acid production and loss of NO x in high latitude plumes.

Dinitrogen pentoxide, N₂O₅, is an important nighttime intermediate in the oxidation of NO_x that is hydrolysed on surfaces. We conducted a field campaign in Fairbanks, Alaska during November 2009 to measure the gradient and derive a flux (and deposition velocity) of N₂O₅ depositing to snowpack using the aerodynamic gradient method. The deposition velocity of N₂O₅ under Arctic winter conditions was found to be 0.59 ± 0.47 cm s⁻¹, which is the first measurement of this parameter to our knowledge. Based on the measured deposition velocity, we compared the chemical loss rate of N₂O₅ via snowpack deposition to the total steady state loss rate and found that deposition to snowpack is at least 1/8th of the total chemical removal of N₂O₅ that is located within the first few meters above the ground surface

Dinitrogen pentoxide, N₂O₅, is an important nighttime intermediate in oxidation of NO_x that is hydrolysed on surfaces. We conducted a field campaign in Fairbanks, Alaska during November, 2009 to measure the flux (and deposition velocity) of N₂O₅ depositing to snowpack using the aerodynamic gradient method. The deposition velocity of N₂O₅ under Arctic winter conditions was found to be 0.59 ± 0.47 cm/s, which is the first measurement of this parameter to our knowledge. Based on the measured deposition velocity, we compared the chemical loss rate of N₂O₅ via snowpack deposition to the total steady state loss rate and found that deposition to snowpack is a significant fraction of the total chemical removal of N₂O₅ measured within a few meters of the ground surface

Abstract. We report evidence for ice catalyzing N2O5 heterogeneous hydrolysis from a study conducted near Fairbanks, AK in November 2007. Mixing ratios of N2O5, NO, NO2, and ozone are reported and are used to determine steady state N2O5 lifetimes. When air masses are sub-saturated with respect to ice, the data show longer lifetimes (≈20 min) and elevated N2O5 levels, while ice-saturated air masses show shorter lifetimes (≈6 min) and suppressed N2O5 levels. We also report estimates of aerosol surface area densities that are on the order of 50 μm2/cm3, a surface area density that is insufficient to explain the rapid losses of N2O5 observed in this study, reinforcing the importance of other reactive surfaces such as ice. Ice-saturated pollution plumes are ubiquitous in high latitudes; therefore, catalysis on these surfaces is largely responsible for nocturnal processing of N2O5 leading to nitric acid production and loss of NOx in high latitude plumes.