Multiphase modeling of nitrate photochemistry in the quasi-liquid layer (QLL): implications for NO_x release from the Arctic and coastal Antarctic snowpack

C. S. Boxe (1) , A. Saiz-Lopez (1)

1 JPL - Jet Propulsion Laboratory

We utilize a multiphase model, CON-AIR (Condense Phase to Air Transfer Model), to show that the photochemistry of nitrate (NO₃^?) in and on ice and snow surfaces, specifically the quasi-liquid layer (QLL), can account for NO_x volume fluxes, concentrations, and [NO]/[NO₂](?=[NO]/[NO₂]) measured just above the Arctic and coastal Antarctic snowpack. Maximum gas phase NO_x volume fluxes, concentrations and ? simulated for spring and summer range from 5.0×10⁴ to 6.4×10⁵ molecules cm^?3 s^?1, 5.7×10⁸ to 4.8×10⁹ molecules cm^?3, and ~0.8 to 2.2, respectively, which are comparable to gas phase NO_x volume fluxes, concentrations and ? measured in the field. The model incorporates the appropriate actinic solar spectrum, thereby properly weighting the different rates of photolysis of NO₃^? and NO₂^?. This is important since the immediate precursor for NO, for example, NO₂^?, absorbs at wavelengths longer than nitrate itself. Finally, one-dimensional model simulations indicate that both gas phase boundary layer NO and NO₂ exhibit a negative concentration gradient as a function of height although [NO]/[NO₂] are approximately constant. This gradient is primarily attributed to gas phase reactions of NO_x with halogens oxides (i.e., as BrO and IO), HO_x, and hydrocarbons, such as CH₃O₂.

Domains: Ocean, Atmosphere

C. S. Boxe, A. Saiz-Lopez. Multiphase modeling of nitrate photochemistry in the quasi-liquid layer (QLL): implications for NO_x release from the Arctic and coastal Antarctic snowpack. Atmospheric Chemistry and Physics Discussions, 2008, 8 (2), pp.6009-6034. ⟨hal-00304055⟩