Cause and Effects of Ozone Depletion,

Global Warming and Acid Rain

In the recent years, human activities exert different kinds of substances into the air affecting the atmosphere causing air pollution. These air pollutions brings about a number of environmental problems such as ozone depletion, global warming and acid rain which threatens the health of human beings and other organisms.

Ozone is a highly reactive gas comprising triatomic oxygen. It provides a thermal blanket for the earth, and protects life by filtering out harmful ultraviolet radiation from the sun. Ozone depletion is the lowered in concentration of ozone in the upper atmosphere. The major cause of ozone depletion is the presence of pollutants such as chlorofluorocarbon compounds, halons and bromine. Chlorofluorocarbon (CFC) compounds are a group of organic compounds, which have been widely used, in daily life as cooling agents in refrigerators and air-conditioners, as blowing agents in the manufacture of foam plastic for insulation and packaging, as propellants for aerosol sprays and also as solvents for cleaning electronic circuit boards and computer components. CFC compounds are remarkably inert and have a long lifetime in the atmosphere, which will be drift up to the upper atmosphere and chlorine radical is released from CFC compounds and reacts with an ozone molecule in the presence of sunlight, therefore ozone molecules are destroyed and forms a chlorine monoxide radical. Chlorine monoxide radical reacts with oxygen radical to form chlorine radical again, which will attack another ozone molecule. Ozone depletion will lead to a series of problems. As the ozone layer is destroyed it will increase the ultraviolet radiations reaching the Earth’s surface. The ultraviolet radiation will have direct effects on DNA causing changes in the genetic information in body cells. Also, it will increase the incidence of skin cancer, cataract, lung diseases and reducing the function of the immune system. Ultraviolet radiations also greatly reduce crop yields. Aquatic life especially phytoplankton which is very sensitive to ultraviolet light, will be affected. The reduction of its productivity in the ocean would disrupt the ecological balance of the food webs. The increase of ultraviolet radiation will also lead to an increase in the incidence of photochemical smog.

Another problem that air pollution brings about is global warming. Global warming is the gradual increase in t he average temperature in the atmosphere as a result of the accumulation of greenhouse gases. It is caused by the increase in concentration of greenhouse gases in the atmosphere that slows down the heat loss from the Earth to the Space. Greenhouse gases include carbon dioxide, chlorofluorocarbons, methane, nitrous oxide, ozone, water vapour and other gases. A large amount of greenhouse gases are generated by various human activities. Tremendous amount of carbon dioxide are released into the atmosphere through burning of fossil fuels in motor vehicles, power stations and factories. Deforestation also increase atmospheric carbon dioxide, because large quantity of trees are reduced, which reduces the rate of removal of carbon dioxide in the air by photosynthesis. And timber and other products from wood may be burnt as fuel or eventually incinerated or decomposed naturally, which combine with oxygen to form carbon dioxide into the air. Extensive use of cooling agents, blowing agents, insulating and packaging materials, aerosol sprays and solvents leads to the release of a large amount of chlorofluorocarbon compounds into the atmosphere. Methane released into the atmosphere from manure of livestock due to the extensive rearing of livestock also causes global warming. Global warming causes a number of possible effects. Firstly, there will be thermal expansion of the oceans, melting of glacial ice and melting of ice caps at Arctic and Antarctic would elevate sea levels, causing flooding at coastal regions. Many of the rainforests in the world at low-lying and at the margin of water level would be removed due to submergence. The distribution of the climatic regions and ocean currents would be changed altering agricultural regions. It also causes weather extremes such as drought, flooding, damaging hurricanes, typhoons and violent storms would increase in intensity and occur more frequently. The increase in the average temperature of marine and freshwater bodies would affect cold-water fish and marine mammals leading to undesirable competition for habitats and food sources. It also affects biodiversity, as some species would become extinct. Increase in temperature may also favor the spread of pathogenic microorganisms affecting humans and other organisms. Pests could also become more active and grow faster, damaging crops and spreading plant diseases causing food shortage and famines.

Acid rain is another major problem caused by air pollution. Acid rain is the precipitation in the form of dilute acid solutions. It is formed by the reactions of various industrial pollutants, such as sulphur dioxide and nitrogen dioxides with naturally occurring oxygen and water vapour forming acid solutions. The acid solutions precipitate as rain or snow. It causes a number of harmful effects. It damages buildings, statues and monuments. It also causes human respiratory diseases such as bronchitis and asthma. It also damages tree foliage and weaken the trees, becoming more susceptible to diseases, insects and drought. The soil acidity will also be increased, which losses valuable nutrients and reducing bacterial activities, affecting the soil fertility. Acid rain also induces the release of aluminium ions from soil particles. The aluminium ions may reach a concentration that is poisonous to plants, damaging roots of trees and other organisms. Lakes will also be acidified and the moderately toxic inorganic mercury compounds in the lake-bottom sediment are converted into methylmercury accumulating the fatty tissues of animals. It will increase in concentrations in the food chains and food webs.