Remediation of the Earth's atmosphere through photoinitiated destruction of freons on the alkaline earth oxide components of tropospheric aerosols

Interaction of some freons with the ambient air-exposed surface of magnesiu m oxide and calcium hydroxycarbonate in darkness and under mild UV radiatio n, corresponding to solar light in the troposphere, can result in efficient irreversible destructive adsorption of some freons. The above photoadsorpt ion activity appears to be related to the optical absorption, detected at w avelengths ranging within 300-400 nm and caused presumably by surface carbo nates or some other surface compounds. The irreversible adsorption is obser ved for H-containing freons like CF3CH2F and CHF2Cl, while for hydrogen-fre e ozone-depleting freons like CF2Cl2 no adsorption is detected. We suggest that at the photostimulated adsorption, fluorine and chlorine atoms substit ute oxygen atoms in the magnesium oxide lattice and hydroxyl groups of calc ium hydroxycarbonates. It was also found that most of the observed photoadsorption phenomena might be related to the presence of a certain amount of N2O natively adsorbed on the alkaline earth oxides exposed to ambient air. Also under discussion is a possible impact of the solar light driven photoadsorption on solid tropo spheric aerosols, containing magnesium oxide and calcium hydroxycarbonate, on the natural non-technogeneous remediation of the Earth's atmosphere from freons. (C) 1999 Elsevier Science B.V. All rights reserved.