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HNO3, this is a corrosive, non-volatile, and
inorganic acid. It is a strong acid (dissociates completely in aqueous solution)
and is also an oxidizer. In the atmosphere it is formed by the conversion of
nitrogen monoxide into nitrogen dioxide, and ultimately into nitric acid:
2NO + O2 --> 2NO2
3NO2 + H2O --> 2HNO3 + NO
Nitrogen monoxide in this process most often come from (fossil fuel-based)
combustion processes that use atmospheric air (containing 78.1% N2)
which combines with atmospheric oxygen in those high temperature combustion
process (see nitrogen monoxide and nitrogen dioxide entries below). Nitric acid
is highly water soluble. This solubility with water allows easy removal of
nitric acid from the troposphere by atmospheric precipitation. Commonly, this is
referred to as acid rain or snow. Nitric acid has a relatively low concentration
in the atmosphere but provides an important role in the production of sulfuric
acid. It acts as a catalyst in the conversion of sulfur dioxide to sulfuric
acid. Sulfuric acid is usually formed within cloud droplets by oxidation of
dissolved sulfur dioxide again most foten released by fossil fuel combustion.
[T.E
Graedel and Paul J. Crutzen. Atmospheric Change: An Earth System Perspective. WH
Freeman and Co, NY.1993.]
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