"photolyzing" - 1 õppematerjal

Formaldehyde

In reviewing the fate of formaldehyde in the environment, it should be noted that the environmental factors that influence the bioavailability to humans of formaldehyde from contaminated air, water, or plant material have not been studied. Air Formaldehyde is removed from the atmosphere by direct photolysis and oxidation by photochemically produced hydroxyl radicals. Formaldehyde absorbs ultraviolet (UV) radiation at wavelengths of 360 nm and longer; therefore, it is capable of photolyzing in sunlight. A half-life of 6 hours has been measured for photolysis in simulated sunlight. There are two photolytic pathways, one producing H2 and CO, and the other producing H and HCO radicals. When the rates of these reactions are combined with estimates of actinic irradiance, the predicted half-life of formaldehyde due to photolysis in the lower atmosphere is 1.6 hours at a solar zenith angle of 40 degrees. Based