1-D Air-snowpack modeling of atmospheric nitrous acid at South Pole during ANTCI 2003

摘要

A 1-D air-snowpack model of HONO has been developed and constrained byobserved chemistry and meteorology data. The 1-D model includes moleculardiffusion and mechanical dispersion, windpumping in snow, gas phase toquasi-liquid layer phase HONO transfer and quasi-liquid layer nitrate andinterstitial air HONO photolysis. Photolysis of nitrate is important as adominant HONO source inside the snowpack, however, the observed HONOemission from the snowpack was triggered mainly by the equilibrium betweenquasi liquid layer nitrite and firn air HONO deep down the snow surface (i.e. 30 cmbelow snow surface). The high concentration of HONO in the firn air issubsequently transported above the snowpack by diffusion and windpumping.The model uncertainties come mainly from lack of measurements and theinterpretation of the QLL properties based on the bulk snow measurements.One critical factor is the ionic strength of QLL nitrite, which is estimatedhere by the bulk snow pH, nitrite concentration, and QLL to bulk snow volumeratio.