Destructive photoadsorption of freons on atmospheric aerosols

Under discussion is possible impact of the solar light driven processes on the natural nontechnogeneous remediation of the Earth's atmosphere from fre ons. The paper concerns an expected role of photocatalytic and photosorptio n processes on tropospheric aerosols in Global Chemistry of the Earth's atm osphere as well as recent experimental data on photoadsorption phenomena ov er alkaline earth metal oxides like MgO and CaO at conditions of real Earth 's atmosphere. Interaction of some freons like CF3CH2F (freon 134a) and CHF 2Cl (freon 22) with the ambient air-exposed surface of magnesium oxide and calcium hydroxycarbonate under mild UV radiation, which corresponds to sola r light in the troposphere, is shown to result in their efficient irreversi ble destructive adsorption. The above photoactivity appears to be related w ith an optical absorption, detected at wavelengths ranging within 300-400 n m and caused presumably by some surface compounds. The photoadsorption is o bserved for H-containing freons only while for hydrogen-free ozone-depletin g freons like CF2Cl2 (freon 12) and C2F3Cl3 (freon 113) it is not detected, At the photostimulated adsorption, fluorine and chlorine atoms seem to sub stitute oxygen atoms in the magnesium oxide lattice and hydroxyl groups of calcium hydroxycarbonates. It was found that the observed photoadsorption p henomena might be related also with the presence of a certain amount of N2O natively adsorbed on the alkaline earth metal oxides exposed to ambient ai r.