6: Explain the causes and effects of ozone depletion, global warming and acid rain. State the role of individual in overcoming these problems.

Ozone Depletion

Ozone is formed by the effect of ultra-violet radiation on oxygen molecules and there are a layer of ozone above the earth between 15 and 40 kilometers. In this way, a large amount of potentially harmful ultra-violet radiation is absorbed and so prevented from reaching the earth’s surface. There is evidence that this beneficial ozone layer is being damaged by atmospheric pollutant. However, a number of pollutants can affect the ozone layer, examples include, chlorofluorocarbons(CFCs) and nitrous oxide(NO). For CFCs, which is being the best known pollutants affecting ozone layer. CFCS are used in refrigerator, as propellants in aerosol sprays, and make up the bubbles in many plastic foams, e.g. expanded polystyrene. They are remarkably inert and therefore reach the upper stratosphere unchanged. For the effects, ultraviolet radiation has direct facts on DNA. It can modify the genetic information in body cells. And then an increase in the incidence of skin cancer, cataract and lung diseases, as well as a reduction in the function of the immune system is probably due to the increase in ultraviolet radiation reaching the Earth. Furthermore, an increase in exposure to ultraviolet radiation can greatly reduce the yields of crops.

Fortunately, ozone layer will be replenished by itself in about 30 years so that if the use of CFCs products can be banned in all over the world. The problem of ozone depletion can be solved.

Global warming

Global warming is mainly caused by a rise in atmospheric carbon dioxide concentration. At the same time, it also depends on the other gases’ concentration. For examples, CFCs, Methane, Carbon monoxide and Oxides of nitrogen. Carbon dioxide is formed during the respiration of organisms, and by the burning of fossil fuels. Scientists believed that this change in air composition prevents more of the sun’s heat escaping from the earth, much in the way the glass in a greenhouse does. They argue that the rise in temperature that this so-called greenhouse effect. However, it produces will cause expansion of the oceans and the gradual melting of the polar ice caps with a consequent rise in sea level.

Acid rain

The major substances of the formation of acid rain are Sulphur dioxide and Nitrogen oxides. For Sulphur dioxide, this is the primary cause of acid rain. It is mainly released from the burning of fossil fuels in power stations, heavy industries and motor vehicles. In the atmosphere, it reacts with oxygen in the air. Within 43 days, it will be converted into sulphur trioxide. During this period, it can be transported for a considerable distance by wind and then dissolved in rain water to form a dilute solution of sulphuric acid. Nitrogen oxides are another cause of acid rain. The burning of fossil fuels in motor vehicles and power stations are mainly responsible for the release of nitrogen oxides into atmosphere. Like sulphur dioxide, nitrogen dioxides reacts with water and oxygen to form nitric acid. These rain causes damage to buildings, statues and monuments. Marble and various metals are corroded by acid rain. At the same time, it also causes human respiratory diseases such as bronchitis and asthma. For environment, acid rain not only can damage tree foliage directly and weaken the trees so that they become more susceptible to diseases, insects and drought. But also increases the acidity of soil. Soil has natural capacity to neutralize some inputs of acids. This normal soil-buffering capacity will be depleted in the presence of acid rain. When the soil Ph is below 4.5, most valuable nutrients are rapidly lost and bacterial activities will be greatly reduced. This affects the soil fertility and in turn, affects the growth of forest trees and crops.