|MadSci Network: Chemistry|
Atmospheric concentrations of CFCs can be known in a number of ways. First,if we know the industrial production of CFCs, if we know the transport of air from the troposphere to the stratosphere, we can calculated steady state concentrations of CFCs in the troposphere. We can do this because we can assume that chemical loss of CFCs in the tropophere (via oxidation with OH) is minimal and that CFCs have a very low solubility in the oceans. We can also directly measure CFCs by "grab sampling." That is, get an evacuated pyrex bulb and take it into the clean troposphere and open it. This will suck in the air in that region. Then purify that air in the laboratory by removing CO2, O2, N2, by crogenic distillation. Then you can either run the sample through a gas chromatograph or a mass spectrometer to view its contents.
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