Ozone Depletion, Greenhouse Gases, and Climate Change (1989) / Chapter Skim
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6 Heterogeneous Chemical Processes in Ozone Depletion
6 Heterogeneous Chemical Processes in Ozone Depletion
Pages 48-55
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From page 48... ...
One is that in contrast to most other species containing chlorine and composed of many atoms, it absorbs light relatively inefficiently; hence it is an efficient sink for storing chIorine. Related species with fewer oxygen atoms photolyze much more readily and do not serve as efficient reservoirs of chlorine.
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From page 49... ...
The chlorine monoxide combines with nitrogen dioxide to reform chlorine nitrate, thereby partially replenishing the chlorine reservoir and removing any remaining nitrogen dioxide from the air. The net effect of the cycle is to release chlorine from the hydrogen chloride (normally very stable)
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From page 50... ...
For initially liquid solutions with a concentration of less than 24 percent, the resultant hydrogen chloride concentration in the solid phase was between about one-third and one-fourth of the corresponding liquidphase value (Figure ~1~. This result, in contradiction to those of the earlier studies, implies that polar stratospheric ice clouds will absorb significant amounts of hydrogen chloride vapor.
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From page 51... ...
Finally, the spectrum for ice containing hydrogen chloride and chlorine nitrate is essentially the same as that for ice containing hydrogen chloride and nitric acid (Figure ~3~. This implies that when chlorine nitrate is deposited on an ice crystal that was previously treated with hydrogen chloride, nitric acid is produced that remains in the solid phase within the ice.
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From page 52... ...
The conclusion of all these experiments is that the chlorine nitrate-hydrogen chloride reaction is very efficient in the presence of ice and produces molecular chlorine, thus converting chlorine from an inactive reservoir form to a form that is readily affected by ultraviolet (UV) radiation (Figure 6-4~.
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From page 53... ...
with the hydrogen chloride in the ice to produce nitric acid and nitry} chloride, which is relatively unstable in the presence of UV. This reaction has been studied by the SRI group and also by a group at the Jet Propulsion Laboratory and has been shown to be an important one for chlorine conversion.
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From page 54... ...
A very similar situation probably obtains with sulfuric acid. The critical point is the amount of water available in the condensed phase for the reaction to occur.
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From page 55... ...
A plausible argument is that if sulfuric acid droplets exist at temperatures close to the frost point of water in the surrounding atmosphere, then they will become very dilute. What happens will depend critically on the temperature, and experiments should be conducted with that in mind.
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