Stratospheric Importance of CIO Radicals

Rowland and Molina and Stolarski and Cicerone proposed that halocarbons 11 and 12 (CFCh and CF2CI2) have a long lifetime in the troposphere, can accumulate there, and diffuse upwards to the stratosphere. Although not photolysed in the troposphere, the two halocarbons absorb in the solar radiation window between 190 and 210 nm, which can occur in the stratosphere at similar altitudes to those where the ozone concentration is reasonably high. Photolytically formed chlorine atoms, either from man-made sources or some natural sources such as combustion of vegetation, may then react via a rapid chain-reaction scheme, giving the overall stoicheiometry O + O3 - 2O2 as the combination of reactions (31) 

In the meantime, substitutes for halocarbons 11 and 12 are being sougjit. For their main uses either as aerosol-can propellants for consumer products, or as working fluids for heat exchangers in air-conditioning and refrigeration plant, the necessary properties are demanding. Apart from low cost and easily attainable 

It seems likely that further kinetic studies and modeling investigations, as well as mudi accelerated research on alternative halocarbons, will be required before a complete solution of the ozone-depletion theory is at hand. For instance, the role of chlorine nitrate, QONOi, has recently been discussed. This molecule can act as an additional QO sink reaction, leading to a reduction in the effect of halocarbons on ozone depletion. 

Halocarbons effects on stratospheric ozone. Panel on Atmospheric Chemistry, National Academy of Sciences, Washington, 1976. 

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