Atmospheric Structure and Ozone

Location in Earth's atmosphere. In the midlatitudes, the peak concentrations of ozone occur at altitudes from 20 to 25 km (about 12 to 16 miles). Most of the remaining ozone occurs in the troposphere, the layer of the atmosphere that extends from Earth's surface up to the stratosphere. The Ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. The ozone layer contains less than 10 parts per million of ozone, while the average ozone concentration in Earth's atmosphere as a whole is about 0.3 parts per million

Life is not possible without a stable atmosphere containing the right chemical ingredients for living organisms: hydrogen, oxygen, nitrogen, and carbon. These ingredients must be balanced. Therefore we need carbon dioxide, ozone as well as water vapours. These are present in minute quantities but are essential for life. So the correct answer is ' Carbon dioxide, ozone and water vapours'.

The absorption of ultraviolet radiation by ozone molecules in the stratosphere releases heat, which causes the temperature in the stratosphere to increase with altitude, making it warmer than it would be otherwise.

The UV-A radiations are scattered and reach the surface of the earth continually. These are the least harmful radiations. The UV-B and UV-C are the most harmful radiations are capable of burning the human skin within 15 minutes of the exposure. These are absorbed by the ozone layer in the stratosphere. The ozone depletion results in the exposure of the earth surface to the UV-B and UV-C causing immunity problems, skin cancers, chlorophyll bleaching etc.

The ozone layer in the stratosphere absorbs solar UV-B (280-320 nm) which is the most harmful part of the ultraviolet. Thus it acts as protector gas for plants, animals by absorbing harmful UV radiation in the stratosphere and as pollutant around the ground level. Nature intended that the stratospheric ozone layer would block the sun's harmful ultraviolet rays.. (CFC), which contains chlorine, an ozone destroyer.

The concentration of ozone varies with an altitude of the atmospheric layers. Ozone is basically stratospheric gas. The reaction of the oxygen with the UV radiations result in the formation of the ozone layer. Peak concentration, an average of 8 molecules per million molecules occur above the altitude of 30kms from the earth's surface which is roughly 20 miles. This is the height that corresponds to the stratosphere.

The high altitude supersonic aircraft flying in stratosphere zone emit nitrous oxides which can destroy ozone significant quantity being highly reactive. Aerosols are tiny particles in the air resulting from the burning of fossil fuels, emission from cars and factories are also causal factors of aerosols. It may be referred to the spray cans that release chlorofluorocarbons which cause the breakdown of ozone Into oxygen once these compound reach the stratosphere.

'Good ozone' is found in the upper part of the atmosphere called the stratosphere and it act as a shield by absorbing ultraviolet radiations from the sun. UV rays are, highly injurious to living organisms. 'Bad ozone' is formed in the lower part of atmosphere called troposphere and it harms plants and animals.

Ozone-depleting substances (ODS) are substances that react with ozone present in the stratosphere and destroy the same. The major Ozone-depleting substances are chlorofluorocarbons (14% of total depletion), nitrogen oxides (3.5% depletion), sulphur dioxide, halon, carbon tetrachloride, methyl chloroform, chlorine, etc.

Ozone depletion is occurring widely in the stratosphere, particularly marked over the Antarctic region.

An ozone layer, present in the stratosphere, reflects the ultraviolet rays emitted by the sun and thus it prevents us from skin diseases and mutation.

The main factor responsible for the depletion of ozone layer is addition of Cl in the atmosphere.
Each Cl atom can destroy as many as 100,000 ozone molecules. Cl atoms comes from chlorofluorocarbons.