Video Transcript
Which of the following gases do not
significantly contribute to the depletion of the ozone layer? (A) Methyl bromide, (B) halons, (C)
CFCs, (D) nitrogen oxides, (E) carbon dioxide.
Ozone is a gas, and a molecule of
ozone contains three oxygen atoms bonded together. Ozone gas is formed in the
stratosphere, which is the second layer of the atmosphere, at an altitude of between
10 kilometers and 50 kilometers. Firstly, oxygen molecules are split
into two free oxygen atoms by ultraviolet radiation from the Sun. A free oxygen atom can then combine
with an oxygen molecule to form a molecule of ozone.
The highest concentrations of ozone
exist within the stratosphere at an altitude of between 20 kilometers and 40
kilometers. This region of the stratosphere is
referred to as the ozone layer. The ozone layer absorbs
short-wavelength ultraviolet radiation from the Sun, and it protects us from these
harmful rays. The presence of certain trace gases
within our atmosphere can deplete the ozone layer. These gases react with ozone and
destroy it. The depletion of the ozone layer by
these gases was detected over the South Pole. A hole in the ozone layer in this
region was reported in 1985.
The gases responsible for the
depletion of the ozone layer include CFCs, methyl bromide, halons, and nitrogen
oxides. Methyl bromide is used as an
insecticide to protect stored crops. Halons are used in fire
extinguishers. CFCs are used as refrigerant gases
where things are kept cool. Nitrogen oxides are created by jet
aircraft when they burn fuels. All of these gases react with and
therefore remove or deplete ozone. They are not correct answers to
this question.
Carbon dioxide is another gas that
is present in trace amounts in our atmosphere. It is a greenhouse gas as it
absorbs infrared radiation. Carbon dioxide does not react with
ozone, and it does not deplete the ozone layer. Carbon dioxide is the correct
answer.
