How Can Chlorofluorocarbons (CFCs) Get to the Stratosphere If They e Heavier than Air?
CFCs reach the stratosphere because the Earth’s atmosphere is always in motion and mixes the chemicals added into it. CFC molecules are indeed several times heavier than air. Nevertheless, thousands of measurements from balloons, aircraft, and satellites demonstrate that the CFCs are actually present in the stratosphere. This is because winds and other air motions mix the atmosphere to altitudes far above the top of the stratosphere much faster than molecules can settle according to their weight. Gases such as CFCs that do not dissolve in water and that are relatively unreactive in the lower atmosphere are mixed relatively quickly and therefore reach the stratosphere regardless of their weight. Measured changes in concentration of constituents versus altitude teaches us more about the fate of compounds in the atmosphere. For example, the two gases carbon tetrafluoride (CF4, produced mainly as a by-product of the manufacture of aluminum) and CFC-11 (CCl3F, used in a variety of human act
