Removal
If an oxygen atom and an ozone molecule meet, they recombine to form two oxygen molecules:
O3 + O· → 2 O2
And if two oxygen atoms meet, they react to form one oxygen molecule:
2 O· → O2
The overall amount of ozone in the stratosphere is determined by a balance between production by solar radiation, and removal. The removal rate is slow, since the concentration of O atoms is very low.
Certain free radicals, the most important being hydroxyl (OH), nitric oxide (NO), and atoms of chlorine (Cl) and bromine (Br), catalyze the recombination reaction, leading to an ozone layer that is thinner than it would be if the catalysts were not present.
Most of the OH and NO are naturally present in the stratosphere, but human activity, especially emissions of chlorofluorocarbons (CFCs) and halons, has greatly increased the Cl and Br concentrations, leading to ozone depletion. Each Cl or Br atom can catalyze tens of thousands of decomposition reactions before it is removed from the stratosphere.
Read more about this topic: Ozone-oxygen Cycle
Famous quotes containing the word removal:
“If God now wills the removal of a great wrong, and wills also that we of the North as well as you of the South, shall pay fairly for our complicity in that wrong, impartial history will find therein new cause to attest and revere the justice and goodness of God.”
—Abraham Lincoln (1809–1865)
“Many a reformer perishes in his removal of rubbish,—and that makes the offensiveness of the class. They are partial; they are not equal to the work they pretend. They lose their way; in the assault on the kingdom of darkness, they expend all their energy on some accidental evil, and lose their sanity and power of benefit.”
—Ralph Waldo Emerson (1803–1882)
“Anyone who seeks for the true causes of miracles, and strives to understand natural phenomena as an intelligent being, and not to gaze at them like a fool, is set down and denounced as an impious heretic by those, whom the masses adore as the interpreters of nature and the gods. Such persons know that, with the removal of ignorance, the wonder which forms their only available means for proving and preserving their authority would vanish also.”
—Baruch (Benedict)