Why are CFC molecules released at ground level able to reach the stratosphere?
Environmental impacts · EPA 608 Core. The correct answer, and the reasoning behind it.
How CFCs and HCFCs destroy stratospheric ozone, and what that does to health and the environment.
The question
Why are CFC molecules released at ground level able to reach the stratosphere?
- They are lighter than air and rise to the stratosphere within hours
- Rain carries them upward during storms
- Sunlight in the lower atmosphere turns them into ozone
- They are very stable and do not break down low in the airCorrect answer
Why “They are very stable and do not break down low in the air” is correct
CFCs are very stable in the troposphere, so instead of breaking down they last long enough for air movement to carry them up into the stratosphere over the years. There strong ultraviolet light finally splits them and releases chlorine.
Source: EPA: Test Topics
Why the other answers are wrong
- They are lighter than air and rise to the stratosphere within hours — CFC vapors are heavier than air; they reach the stratosphere by slow mixing, not by floating up.
- Rain carries them upward during storms — Rain washes soluble chemicals down out of the air; it does not lift CFCs.
- Sunlight in the lower atmosphere turns them into ozone — CFCs are not converted into ozone; they lead to its destruction.
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