Chlorine Nitrate CIONO

During the dark, polar winter the temperature drops to extremely low values, on the order of-80°C. At these temperatures, water and nitric acid form polar stratospheric clouds. Polar stratospheric clouds are important because chemical reactions in the stratosphere are catalyzed on the surface of the crystals forming these clouds. The chemical primarily responsible for ozone depletion is chlorine. Most of the chlorine in the stratosphere is contained in the compounds hydrogen chloride, HCl, or chlorine nitrate, CIONO. Hydrogen chloride and chlorine nitrate undergo a number of reactions on the surface of the crystals of polar stratospheric clouds. Two important reactions are ... 

A reactive species can also be temporarily removed from a catalytic cycle and be stored in a reservoir species (recall N.Os), which itself is relatively unreactive but is not actually removed from the atmosphere. One of the most important reservoir species in the stratosphere is chlorine nitrate (CIONO.), formed by... 

The release of man-made CFCs in the atmosphere has lead to an increase of chlorine containing reservoir molecules such as CIONO, (chlorine nitrate) and HC1 in the stratosphere. Under normal nonpolar conditions, the reaction between both species is extremenly slow. However in the presence of cold surfaces, the following reactions are believed to occur on the PSCs [33] ... 

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