Hydrogen peroxide formation from the photooxidation of formaldehyde and its presence in rainwater

The photooxidation of formaldehyde with sunlamps (Emax = 3100 Å) produces hydrogen peroxide at varying concentrations depending upon the amount of water vapor present. It is postulated that the variable production of H2O2 is a result of condensation on the reactor surface. Rainwater samples were also analyzed for H2O2. Summer rain in the Triangle area of North Carolina contained as much as 200 ppb (w/w) of H2O2. Rainwater collected in December contained much less H2O2, usually 2–8 ppb. The lower concentration found in the colder conditions is attributed to a decrease in photochemical activity.