Unit iii notes social issues 1
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Global warming is caused by an increase in greenhouse gases like carbon dioxide and methane that are trapping heat in the atmosphere. This is leading the planet to warm at a dangerous rate, with the average global temperature already 1°C higher than 1900 levels. The major cause of increased greenhouse gases is human activities like burning fossil fuels and deforestation. If emissions are not reduced, the global temperature could increase by 1-3°C by the middle of the century, causing serious environmental effects.
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Unit iii notes social issues 1
- 1. UNIT III Social Issues and the Environment Global Warming Global warming is defined as the increase in temperature of the earth, which causes more changes in climate. The Imbalance of earth surface temperature in presence of green house gases (CO2, CH4, N2O, CFC and H2O) in the environment known as global warming The average global temperature is now 1°C (1.8°F) higher than in 1900. Predictions of future climates indicate that by the middle of the next century the earth's global temperature may be 1°C to 3°C higher than today. The greenhouse effect The lower most layer of atmosphere traps heat by a natural process due to the presence of certain gases this effect is known as green house effect and maintain the temperature for sustaining the life on earth surface. The atmospheric gases trap heat on earth surface to keep the planet warm enough to sustain life, this process is called the greenhouse effect, it is a natural process and without these gases, the Earth would be too cold for humans, plants and other creatures to live. Ultraviolet (UV) radiation has a higher energy level than visible light, and infrared (IR) radiation has a lower energy level. Some of the sun's incoming radiation is absorbed by the atmosphere, the oceans and the surface of the Earth. Much of it, however, is reflected out to space as low-energy infrared radiation. For Earth's temperature to remain stable, the amount of incoming solar radiation should be roughly equal to the amount of IR leaving the atmosphere. This reflected energy cause the imbalance of earth surface temperature known as global warming Causes of Global warming The cause of global warming is the increasing quantity of greenhouse gases in atmosphere produced by human activities, like the burning of fossil fuels or deforestation. These activities produce large amounts of greenhouse gas emissions which are causing global warming. Greenhouse gases There are several gases in Earth's atmosphere known as "greenhouse gases" because they exacerbate the greenhouse effect: Carbon dioxide (CO2), methane, nitrous oxide, water vapor and ozone are among the most prevalent, according to NASA. Not all greenhouse gases are the same: Some, like methane, are produced through agricultural practices including livestock manure management. Others, like CO2, largely result from natural processes like respiration and from the burning of fossil fuels. The majorities of man-made carbon dioxide emissions are from the burning of fossil fuels such as coal and oil so that humans can power various vehicles, machinery, keep warm and create electricity. Other important sources come from land-use changes (ex: deforestation) and industry (ex: cement production). Methane is created by humans during fossil fuel production and use, livestock and rice farming, as well as landfills.
- 2. Nitrous oxide emissions are mainly caused by the use of synthetic fertilizers for agriculture, fossil fuel combustion and livestock manure management. Fluorinated gases are used mainly in refrigeration, cooling and manufacturing applications The volcanic eruptions, microbial degradation of waste materials release the methane and nitrous oxide Forest fire, open burning of fire wood release the carbon dioxide Effects of Global Warming Following are some of the effects of global warming a. More heat waves b. Expansion of desert area c. Natural fires in forest lands d. More evaporation of water from oceans and water bodies e. Melting of ice caps, Arctic and Antarctica regions f More cloud formation in the atmosphere. g. Shorter and warmer winters and longer and shorter summer h. Changes in pattern of rainfall i. Rise in sea level j. Flooding and submergence of low lying coastal areas k. Disruption in farming l. More droughts m. More impacts on plants, animals and humans Control and Remedial measures of Global Warming Some of the control and remedial measures of global warming are: i. Reduction in consumption of fossil fuel such as coal and petroleum. ii. Use of biogas plants. iii. Use of nuclear power plants. iv. Increasing forest cover. v. Use of unleaded petrol in automobiles. vi. Installation of pollution controlling devices in automobiles and industries. Acid rain Acid rain was discovered in the 1800's in Great Britain. Acid rain is a broad term used to describe several ways that acids fall out of the atmosphere. A more precise term is 'acid deposition'. Wet deposition and dry deposition are the two parts of acid deposition. Wet deposition refers to acidic rain, fog, and snow. As this acidic water flows over and through the ground, it affects plants and animals in many ways. Dry deposition refers to acidic gases and particles. About half of the acidity in the atmosphere falls back to earth through dry deposition. Both wet and dry deposition can cause the same damage. Sulphuric acid (H2SO4.) and Nitric acid (HNO3) are the two principal acids present in acid rain. Acid rain is still a very large environmental problem that the world is trying to solve. Until the atmospheric release of pollutants is stopped, acid rain will continue to fall and become one of the greatest examples of the destructive behavior of mankind. Measuring Acid Rain Acid rain is measured using pH scale. Lesser value of pH indicates more acidity. Pure water has a pH value of 7.0. Normal rain is slightly acidic, with a pH value of 5.6, because carbon dioxide dissolves into it. Mechanism of Formation of acid rain Mechanism of formation of Sulphuric acid:
- 3. The different sources of acid rain are shown in Figure Fig: Sources of acid rain. Sulphur dioxide and oxides of nitrogen are the primary sources of acid rain. These developed due to natural activities and anthropogenic activities. These are tabulated in Table -4.1. Table: Sources of SO2 and NOx. Impacts of Acid Rain Acid rain can cause serious problems for many different, animals and plants. 1. Both dry and wet deposition of sulphur dioxide significantly increases the rate of corrosion of lime stone, sand stone and marble. 2. Forest tree population is affected and decreased by acid rain. 3. Acid rain in combination with ozone may damage the waxy coating on leaves and needles. This may weaken or damage them and provide opportunities for disease to enter the tree. 4. Acid rain may change the characteristics of soil and eventually pollute the streams and lakes. 5. Acid rain adds hydrogen ions to the soil. These hydrogen ions leach the important nutrients such as Calcium, Magnesium and Potassium and affect its availability to the roots of the plant. 6. It may reduce the number of zooplanktons, phytoplankton, mollusks, and small crustaceans. 7. It reduces the decomposition of dead plants and animals.
- 4. 8. Calcium deficiency in fishes can lead for bone malformation. 9. The health effects that people have to worry about are not caused by acid rain, but are caused when people breathe in these tiny particles or ozone. When these particles get into people’s lungs, they can cause health problems, or can make existing health problems worse. Also, nitrogen oxides cause ground level ozone, which causes respiratory problems like, pneumonia and bronchitis, and can even cause permanent lung damage. 10. The chemicals found in acid rain can cause paint to peel and stone statues to begin to appear old and worn down, which reduces their value and beauty. Control of acid rain The formation of acid rain can be minimized by using the following methods. 1. by reducing pollution from industries, 2. By using other sources of energy, and 3. By using cleaner automobiles. 1. Reducing Pollution from industries: The release of sulphur dioxide is reduced from the coal burning power plants in the following ways. a. By using less sulphur coal. b. By washing the coal to remove some of the sulphur. c. By installing pollution controlling devices like scrubbers to remove the sulphur dioxide. 2. By using other sources of energy: By producing energy without using fossil fuels more possibility of acid rain can be minimized. Use of fossil fuel can be reduced by using use renewable energy sources, such as solar and wind power. Renewable energy sources help in reducing acid rain because they produce much less pollution. These energy sources can be used to power machinery and produce electricity. 3. By using cleaner automobiles: Automobiles are the major sources of the acid rain pollutants. By using pollution control device like catalytic converter or by using natural gas in the automobiles, the possibility of formation of pollutants that are responsible for the formation of acid rain can be minimized. 3.2 Ozone Layer Depletion Ozone Ozone is an odorless, colorless gas composed of three atoms of oxygen (0,). The 'normal' oxygen we breathe has 2 atoms of oxygen in it (0 ). Ozone has-the same chemical structure whether it occurs miles above the earth or at ground level and can be 'good' or 'bad,' depending on its location in the atmosphere. Ozone is naturally formed by short wavelength ultraviolet radiation in the upper stratosphere. Wavelengths less than 240 nm are absorbed by normal oxygen molecules (O2)3 which dissociate to give O atoms. The O atoms in combination with other oxygen molecules produce ozone. O2+ (Short wavelength < 240nm) -> O+ O O2+O ----------O3 CFC CFC is short for Chlorofluorocarbon. These are manmade chemicals which comprise Chlorine, Fluorine and Carbon atoms. These were developed in the early 1930s and are used in various industrial, commercial, and household applications. These substances are a. Non-toxic b. Non-flammable
- 5. c. Non-reactive with other chemical compounds. These desirable safety characteristics, along with their stable thermodynamic properties, make them ideal for many applications as coolants for commercial and home refrigeration units, aerosol propellants, and solvents in electronic industry, and blowing agents in fire extinguishers. The most important types of CFC's for ozone depletion are a. Trichlorofluoromethane, CFC1- (called as CFC-11) CFCL2 b. Dichlorodifluoromethane, CFCl2 (CFC-12) c. 1,1,2 Trichlorotrifluoroethane,CF3Cl2CFC(CFC-l 13) Ozone Layer Depletion Process In the stratosphere region, between 19 and 30 km above the Earth's surface, ozone is constantly being produced and destroyed naturally. This production and destruction makes the stratosphere with ozone layer, which is used to filter the ultra violet radiation from the Sun and protects life on Earth. Usually there is a fine balance between the build up and loss of ozone. But the man-made chemicals called Chlorofluorocarbons (CFC's), which are used as propellants in aerosol sprays, refrigerants, and coolants etc., are destroying the ozone molecules in the ozone layer. The Chlorofluorocarbons themselves do not destroy ozone molecules. But they are decaying the ozone molecules at the low temperatures. A small amount of Chlorine atom (Cl), and Chlorine Monoxide (CO), is functioned as catalyst in the process of destruction of ozone. Once the chlorine has broken up one ozone molecule, it is freed to repeat the process again and again, until its removal by any other means or reaction in the atmosphere. The Chlorofluorocarbons released are stable and can live up to about 100 years. Dobson Unit Dobson Unit (DU) is the scale for measuring the total amount of ozone occupying a column overhead. One Dobson unit (1 DU) is defined as 0.01 mm at 0°C and 1 atmospheric pressure. If the ozone layer thickness is compressed to 0°C and 1 atmosphere pressure, is about 5 mm thick, then the average thickness of the ozone layer would be about 500 DU. In absolute terms, 1 DU is about 2.7 x 1016 molecules/cm2 . G.M.B. Dobson, between the years 1920- 1960, carried out pioneering studies of atmospheric ozone, and designed the standard instrument used to measure ozone from the ground. The Dobson spectrophotometer measures the intensity of solar UV radiation at four wavelengths, two of which are absorbed by ozone and two of which are not. Harmful Effects of ozone layer depletion The ozone layer is protecting all the life forms in the earth from the Sun's damaging UV radiation. Any significant decrease in the amount of ozone high up in the atmosphere would result in an increase in the amount of UV radiation reaching the Earth's surface. This in turn would lead to an increase in harmful effects for human beings and all other lives. Human Health i. Reddening of skin in sun light (Sun burn) ii. Skin Cancer iii. Reduction in body's immunity to disease iv. Eye disorders like Cataracts and Blindness
- 6. Other Living things i.The UV rays are harmful to other forms of wildlife, particularly small ii.Plants and animals living in the sea called 'Plankton'. Plankton forms iii.The base of the Ocean food chain. iv.The UV rays can damage certain crops, like rice, which many people in the world rely on for food. These can damage polymers used in paint, clothing and other materials. Controlling methods of Ozone depletion Planting the trees, Create the awareness in general public, Decrease the usage of refrigerators,, deodorants, Air conditioners Use the halogens (Bromine) instead of chlorocarbons