Photochemical reactions of impurities in natural snow and ice are important because they: (1) release reactive gases � such as nitrogen oxides (NOx) and molecular halogens � to the atmosphere, (2) transform pollutants in snow and ice, and (3) alter the composition of the snow/ice, which can influence ice core records of past atmospheres.  Understanding these impacts requires quantifying the photochemical kinetics of solutes, which is complicated by the fact that they can be present in different reservoirs in/on the ice. These include at the air-ice interface, at the interface between ice grains, and within the bulk ice matrix.  Past work suggests that reactions at the air-ice interface can be enhanced relative to reactions in the other reservoirs, but this is an unresolved issue. To examine this question, we are using two complementary approaches.  In the first, we are employing 3-D X-ray computed tomography to image the locations of solutes in laboratory ice samples frozen using different techniques.  For the second approach, we are characterizing the photochemistry of solutes in ice samples prepared with these different freezing techniques to see how photon fluxes and photochemical kinetics vary between the three ice reservoirs.

Photochemistry at ice interfaces

248th National Meeting (2014)

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