Ozone Depletion

Ozone Depletion

Essay

ozone depletion is a serious problem presently facing the world. The ozone layer protects humans, animals, and plants from harmful ultraviolet rays. Money and time are being spent on ozone repair, but the problem still exists.

The ozone layer is a region of the stratosphere containing ozone, or O3 gas. The ozone layer is necessary to both plant and animal life on earth because it protects the surface from dangerous ultraviolet light.

However, manufacturing and household chemicals that are currently in use have been found to destroy ozone, and the problem has worsened to an ozone layer "hole" above Antarctica. Ozone levels there are 40 percent below normal, and there may be another ozone hole forming above the Arctic region.1

Ozone gas contains an extraneous oxygen atom in each molecule and is highly unstable. This property lets ozone block out ultraviolet rays and makes it an essential part of the eco-system. When harmful ultraviolet-B rays (wavelength 240-320 NM) come through the atmosphere, the O3 molecules absorb the energy and one oxygen atom removes from the molecule. The stray atom will eventually collide with another O2 molecule and ozone will be reformed. With this process, the level of ozone remains constant, as it has for millions of years.3

Recently, a number of chemicals have been found to aid in the rapid destruction of ozone. Most of these chemicals are compounds called chlorofluorocarbons, or CFC’s. It is difficult to ban them outright because they have hundreds of industrial uses. CFC’s are widely used because they are non-toxic, non-flammable, and inexpensive. Recent environmental legislation on both the state and national levels has banned the use of some CFC’s, but the question of their disposal still remains.4

Chlorofluorocarbons do not destroy ozone directly. Compounds made from CFC’s photo-decay series act as catalysts in the breaking up of O3 molecules. When CFC’s reach the stratosphere, they break down when collided by the intense light rays. The molecule comes apart and a majority of the chlorine then forms hydrogen chloride or chlorine nitrate, which then decay into atomic chlorine or chlorine monoxide.3

These are the substances responsible for the physical destruction of ozone. As they come in contact with an ozone molecule, they cause the third oxygen atom to detach and form an O2 molecule with another lost oxygen atom. Since they don’t react with the oxygen, the chlorine compounds remain undamaged and can destroy up to 150,000 ozone molecules each.3

There are a number of different CFC’s. The compounds most responsible for ozone layer destruction are CFC-11 (trichlorofluoromethane), CFCl3; CFC-12 (dichlorodifluoromethane), CF2Cl2; and CFC-113 (1,1,2 trichlorotrifluoroethane), CF2ClCFCl2. All of these compounds are excellent refrigerants, and CFC-12 is marketed by DuPont as Freon™.3

The word "CFC" has become a basic term referring to any substance that is deleterious to the ozone layer. However, many destructive compounds are not CFC’s by definition. All ozone-destroying compounds contain at least one of two common elements: chlorine, or the more catalytic bromine. Compared atom-to-atom, bromine can destroy 10-100 times the number of ozone molecules as chlorine. Fortunately, its atmospheric concentration is much smaller.3

One of the other O3-destructive groups is called the hydrochlorofluorocarbons, or HCFC’s. HCFC’s are organic compounds in which not all of the hydrogen atoms have been replaced by chlorine or fluorine. One such compound is R-22 (HCFC-22), CHClF2.3

Some other non-CFC compounds that destroy the ozone layer include carbon tetrachloride (tetrachloromethane), CCl4; methyl chloroform (1,1,1 trichloroethane), CH3CCl3; and methyl chloride (chloromethane), CH3Cl.3

The result of ozone layer depletion is a increase in ultraviolet rays at the surface. Humans, animals, marine life, and plants are all susceptible to UV radiation damage.

Current studies indicate that ultraviolet rays could be disastrous to the marine eco-system. High UV concentration causes phytoplankton, microscopic organisms at the base of the food chain, to decrease their reproductive activity. Although there is no serious widespread effect now, the problem may escalate in future years.3

Numerous studies have proven that ultraviolet radiation, in both the UV-A and UV-B forms, causes skin cancer. Of the three types of skin cancer, basal