Lillian Liem 6S 26

Date:04-01-2004

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

Air pollution is exerting increasing impact on the environment. Humans have been altering the chemistry of the atmosphere on a global scale through their activities. This may already be modifying the climate. These changes not only threaten the health of human beings and other organisms, but also create many environmental problems such as diminish the protective ozone layer in the upper atmosphere (ozone depletion), acid rain and contribute to the potential of global climatic changes. All these are seriously upsetting the balance of the global ecosystem.

Ozone Depletion

The ozone layer is an important protective layer in the upper atmosphere. It provides a thermal blanket for the Earth, and protects life by filtering out harmful ultraviolet radiation from the sum. Ozone depletion refers to a lowered concentration of ozone in the upper atmosphere, leading to the formation of “holes”. They have been due to chemical effects. Chlorofluorocarbon compounds are regarded as the major cause of ozone depletion. They are a group of organic compounds composed of chlorine, fluorine and carbon. These chemicals may drift up to the upper atmosphere and are involved in chlorine – releasing reactions. The chlorine radical is released from CFC compounds and reacts with an ozone molecule in the presence of sunlight. This chlorine radical can attack another ozone molecule to form “holes”. The destruction of the ozone layer results in a significant increase in ultraviolet radiation reaching the Earth’s surface. Ultraviolet radiation has direct fects on DNA that can modify the genetic information in body cells. Also, it leads to an increase in the incidence of photochemical smog and can greatly reduce the yields of crops.

Less use CFC compounds can reduce the effects of ozone

depletion. Many aerosol sprays such as hair mosses and household cleaning products contain CFC compounds. So, we need to use the other that are now free of CFC compounds and avoid using foam plastic and plastic containers.

Global Warming

Global warming refers to the gradual increase in the average temperature in the atmosphere as a result of the accumulation of greenhouse gases (CO, CFC compounds, Methane and NO). The increase in concentration of greenhouse gases in the atmosphere slows down the heat loss from the Earth to the Space. As a result, the atmosphere is warming up. This leads to changes in changes in climate and other subsequent effects on the Earth. Deforestation causes the increase in atmospheric carbon dioxide content. Extensive rearing of livestock is also a cause of global warming because methane is released into atmosphere from the manure of livestock in some countries. Also, rapid growth of transport and extensive use of cooling agents release NO and a large amount of CFC compounds into the atmosphere. Global warming may be a big problem, but there are many little things we can do to make a difference. If we try, most of us can do our part to reduce the amount of greenhouse gases that we put into the atmosphere.

Planting trees is fun and a great way to reduce greenhouse gases. Trees absorb carbon dioxide, a greenhouse gas, from the air. Whenever we use electricity, we help put greenhouse gases into the air. By turning off lights, the television, and the computer when you are through with them, you can help a lot. Solar energy is a fancy way of saying "energy that comes from the sun." Solar energy can be used to heat homes, buildings, water, and to make electricity.

Acid Rain

Acid rain refer to precipitation in the form of dilute acid solutions. It is formed by the reactions of various industrial pollutants, such as SO2 and NO2 with naturally occurring oxygen and water vapour, forming acid solutions. Acid rain typically has a pH from 4.0 to 5.4. SO2 mainly released from the burning of fossil in power stations, heavy industries and motor vehicles. In the atmosphere, SO2 reacts with oxygen in the air. Then it will be converted in SO3. and can be transported by wind and dissolved in rain water to form dilute H2SO4. Besides, NO2 is released from the burning of fossil fuels in motor vehicles and power stations into the atmosphere. NO will combine with atmosphere oxygen to form NO2 then reacts with water and oxygen to from HNO3. Acid rain increase the acidity of soil. This affects the soil fertility and in turn, affects the growth of forest tress and crops. Also, Acid rain can induce the release of aluminium ions from soil particles, Once released, the water-soluble aluminium ions may reach a concentration that is poisonous to plants that can damage the roots of trees and kill aquatic organisms.

In order to reduce the formation of acid rain, we buy vehicles with low NO_x emissions, and maintain all vehicles well and turn off lights, computers, and other appliances when we are not using them. We can use energy efficient appliances: lighting, air conditioners, heaters, refrigerators, washing machines, etc.