Ozone In The Atomosphere – Its Birth and Decay

Monday, June 25, 2007

In Kathmandu, the magnitude of atmospheric pollution has been increasing rapidly. Further, this polluted atmosphere is multiplying by unwanted waste materials from garment industries, pollutant gases from worn-out vehicles and plenty of dust generated by unplanned urban scheme It is now the high time for the government of Nepal to pass and implement laws pertaining to the environment. By saving nature we will save our lives.

Something about Ozone in the Atmosphere:

Ozone is an allotropic form of oxygen, containing the oxygen atoms in the molecule. Its chemical symbol is O3 in contrast to ordinary oxygen (O2) where there are only two oxygen atoms. It is a bluish gas, very active chemically and a powerful oxidizing agent.

Atmospheric phenomena associated with the earth’s magnetic and gravitational fields extend outward for several thousand kilometers. The largest concentration of ozone is found to occur near the outer limit of the stratosphere (20-30 km). This layer is called ozone layer. The ozone layer is extremely useful to you as it filters the harmful ultraviolet radiations coming from the sun into the earth’s surface. The ozone layer protects us from the harmful UV radiations from the sun by absorbing and thereby screening out them which otherwise can cause skin cancers. When the UV radiations are absorbed by the DNA present in the cells of all living beings, the resulting disorder called the “DNA disorder” can lead to mutation, genetic defects, and skin cancer. The depletion in the thickness of the ozone layer is now positively exposing the plants, animals, and human beings to the UV radiation thereby adversely affecting their yield, health and genetics.

Many substances participate in the decay of ozone by different processes. Scientists know a lot about it. There are only a few substances that react with the ozone strongly enough to “eat” it. The chlorofluorocarbons (CCl2F2), methane, and nitrogen oxide gases have the capacity to react with ozone and convert it into oxygen. CFCs are very stable compounds which escape from the leaky air-conditioners and refrigerators. These slowly reach the ozone layer of the atmosphere and come in contact with the UV radiations which are capable of breaking CFCs and releasing chlorine from it. The chlorine atom acts upon the ozone and produces oxygen and ClO. The ClO in turn acts upon another ozone molecule to produce two molecules of oxygen and release one of chlorine and again the chlorine atom acts on new ozone molecule. Thus chlorine acts as a catalyst and just one chlorine atom can destroy several thousand of ozone molecules before the released chlorine gets converted into the dilute HCl which comes down with the rain. Similarly, nitrous oxide produced by the biological denitrification slowly reaches the stratosphere where it gets oxidized into nitric oxide. The nitric oxide acts upon the ozone molecule to produce oxygen and nitrogen dioxide. The nitrogen dioxides eventually acted by water and acid precipitates in the form of rain. Besides the aerosols from cfcs from refrigerators, spray packs of fresheners, hair sprayers, fly killers release aerosols which float in the air and slowly reach the ozone layer. The other main culprits for depleting the ozone layer are synthetic chemicals, foams, electronics industries, carbon tetrachloride used in pesticides and paints, etc.

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