Oxidation is a process in which something (an atom or molecule or substance) loses an electron to something else. Photo-oxidation is therefore the process of oxidation which is caused by shining light on it. Often, light can be used to cause reactions to happen, such as oxidation. The term "photo" comes from "photon" which is light.
Its primary use is in the Contact Process (making Sulphuric Acid). This can be done directly by reacting Sulphur Trioxide with Water to form dilute, but highly corrosive, Sulphuric Acid: SO3(g) + H2O(l) = H2SO4(aq) It can also be achieved indirectly by adding Sulphur Trioxide to Sulphuric Acid to form Disulphuric Acid (Pyrosulphuric Acid, Fuming Sulphuric Acid or Oleum) then Reacting Disulphuric Acid with Water to Form Concentrated Sulphuric Acid: SO3(g) + H2SO4(l) = H2S207(l) H2S2O7(l) + H20(l) = 2H2SO4(l)
its the breakdown of NO2 and NO3 into gaseous nitrogen N2. When this happens the N2 is released into the atmosphere because it is for the most part unusable by plants and organisms, unless it is submerged in water. When it gets into the atmosphere it acts as a catalyst in the break down of ozone. Now its not typically as wide spread or released in the amounts that CO2 is on a daily basis however since it isn't needed in huge quantities.