photochemical smogs

1) in the combustion of engines the high temps cause nitrogen to be converted into nitrous monoxide 2) Nitrous monoxides are oxidized to produce nitrous dioxide which is split by UV radiation 3) this provides oxygen-free radicals which creates tropospheric ozone

a variety of reactions of primary and secondary pollutants in the presence of UV radiation during temperature inversions creating high levels of tropospheric ozone and nitrogen oxides

a secondary pollutant in photochemical smogs caused by the reaction of tropospheric ozone, nitrogen oxides, and unburnt hydrocarbons to form peroxyacetyl nitrates