We can define the term
NOy as the sum of NOx plus all oxidized nitrogen
species that represent sources of oxides of nitrogen
through processes that occur on relatively short time
scales. That includes nitric acid (HNO3), inorganic
aerosol nitrate (NO3), nitrous acid, nitrate radical,
peroxynitric acid (HOONO2), chlorine nitrate
(C1ONO2), dinitrogen pentoxide (N205), peroxyacetyl nitrate and other organic nitrates of various
types