Nitrous acid (HONO) is an important atmospheric trace gas, as it photo-dissociates into nitrogen monoxide (NO) and hydroxyl radical (OH), which is the main driver of atmospheric oxidation cycles leading to ozone and aerosol formation. The exchange of HONO between air and snow affects the oxidation capacity of air masses in contact with snow and influences the way nitrogen oxides are trapped into ice archives, from which past climates are reconstructed.
We have used the short-lived radioactive isotope ¹³N to follow migration of HONO in a snow sample packed into a small flow tube in situ. The figure shows how the distribution of HO¹³NO along the snow sample evolves with time.

This work has been performed in the group of Prof. Heinz W. Gäggeler / Prof. Andreas Türler.

References:

• M. Kerbrat, T. Huthwelker, H. W. Gäggeler and M. Ammann;
  "Interaction of Nitrous Acid with Polycrystalline Ice: Adsorption on the Surface and Diffusion into the Bulk"
  J. Phys. Chem. C, 114, 2208–2219, (2010); doi:10.1021/jp909535c.