2SyllabusCurrent Environmental Global Issues: Global Warming & Green Houses Effects, Acid Rain , Depletion of Ozone Layer
3Important QuestionsExplain Green House Effect. What are various sources of green house gases.How depletion of Ozone layer does takes place in the atmosphere? Explain the ill effect of Ozone Depletion.Define Acid Rain. How does it form and what are its ill effects?Enlist Global Environmental Pollution Problems. Describe one in detail and suggest remedial measures to reduce them.What is Ozone? How is it formed? Describe the main causes of depletion of Ozone layer and briefly comment over control measures taken to prevent further ozone depletion at international level.Explain the Green House Effect with the help of schematic diagram and compare the effect of different green house gases in global warming.Write short notes on (i) Acid Rain (ii) Environmental DegradationEnlist global environmental problems and discuss any one.Write explanatory notesOzone layer DepletionAcid Rains
4Green House EffectThe Increase in CO2 content of the environment has been responsible for gradual heating up the globe, by a process called as green house effect. The progressive warming up of the earth’s surface due to blanketing effect of manmade CO2 in the atmosphere is known as green house effect.
6From sun 3 types of radiations are emitted, ultraviolet rays(< 400 nm), Visible rays ( 400 – 700 nm) and Infrared rays (700 – 1000 nm), of this the visible rays are having maximum intensity i.e. (400 nm to 700nm wavelength). Approx 47 % of the solar radiation is absorbed by water and land surfaces and the remaining rays are radiated back to the atmosphere in the form of Infrared rays (700 nm – 1000 nm). Water vapor and CO2 molecules in atmosphere near earth’s surface absorb the infrared radiations (heat rays) emitted by earth. Thus the net effect causes warming of atmosphere. This effect is called a green house effect.
7Principle of Green House Effect The transparent walls and roofs of the green house are such that they allow visible sunlight to enter but prevents the entry of long wavelength Infrared radiations to go out.Thus the sunlight is absorbed by soil and structure of the green house. It is then re-emitted as heat rays which cannot pass through the glass. The amount of energy in the green house thus increases the warmth of the atmosphere. In similar ways the earth’s atmosphere bottles up the energy of the sun like green house. Here CO2 and water vapor acts like glass windows.CO2 and water vapor in the atmosphere transmits short wavelength solar radiations but reflect longer wavelength heat radiations from warm surfaces of the earth. CO2 molecules are transparent to sunlight but not to heat radiations, so they trap and re-enforce the solar heat like a green house
11Sources of Green House Gasses 1) Burning of Coal, Oil, Natural Gas in the factories.2) Burning of fossil fuels at power stations3) Use of Petrol and Diesel from automobiles, railways, aircrafts etc.4) Burning of firewood and deforestation5) Tree and plants release carbon as CO2.6)Fire in the forests contribute to the release of CO2
12Effects of Warming up of Air Increase in temperature on earth’s surface will cause more evaporation of surface water.Melting of Glaciers (ice mountains)Rise in Sea Level will wash away entire countries from Bombay to Boston.Shifting of climate zones will occur.
14Control Reduce the consumption of fossil fuels Use anti pollution devicesNon conventional energy sources should be developed as a alternate to fossil fuel.Prevent deforestationPlanting more trees.
15Acid RainAcid Rain is a environmental Problem caused due to rapid industrialization. Acid rain has become invisible threat to rivers, lakes and forests.Acid rain means presence of acids in rainwater. The basic component of acid rain are nitric acid, and sulphuric acid.
16Causes of Acid RainAcid Rain is because of human activities. Sulphuric acid is formed when (SO2) is discharged from combustion process converts to sulphurtrioxide (SO3) which reacts with the water vapor present in the atmosphere to form sulphuric acid (H2SO4).The oxides of sulphur and nitrogen are produced by combination of fossil fuels, smelters, power plant, automobile exhausts, domestic fire.
19Effects of Acid RainThe acid rain damages the leaves of plants and trees and retard the growth of forest.Wash out the nutrients from the soil.Significant reduction of fish population and decease in aquatic micro organisms.Damage to Buildings and structural materials.Corrosion of houses, monuments, statues and bridges.The human nervous system, respiratory system and digestive system may get affectedAcid rain reduces the rate of photosynthesis and hence growth of plants.
20Control Liming of Lakes Tough laws to reduce acid forming pollutants, being released in atmosphere.
22Thus it leads to decrease in Ozone concentration which results in reaching of ultraviolet rays to earth surface due to which heat increases to uncomfortable levels and the temperature of earth increases.
23Main Ozone Layer Depletors CFC (Chloro Floro Carbon) The Chlorofloro carbon are less costly, non toxic, and safe to handle material is used in propellants, cleaning solvents, plastic foams, in dry cleaning industries, for sterilizing surgical instruments. Because of wide use of CFC the CFC in the atmosphere is increased and which has caused irreparable damage to our environment.
24Oxides of Nitrogen:- Burning of Fossil fuels and increase in use of nitrogen as a fertilizer are also contributing in destruction of ozone layer.Thus in addition to CFC, the oxides of nitrogen also plays an important role in depletion of Ozone.
25Mechanism of Ozone Depletion The chlorofloro carbons are highly stable and hence they slowly diffuse in the atmosphere. The ultraviolet rays decompose the CFCs and thus free chlorine and fluorine radicals are released In the atmosphere. This chlorine radical released in the atmosphere converts O3 into O2Similarly oxides of Nitrogen also depletes the ozone
26CFCl3 CFCL2 + Cl Cl + O3 ClO + O2 ClO + O Cl + O2 Similarly UV raysCFCl CFCL2 + ClCl + O ClO + O2ClO + O Cl + O2SimilarlyNOx + O NO2 + O2UV raysUV raysUV rays
28Oxygen in the Atmosphere UV radiationOO2++OO3 (ozone)OAn oxygen molecule consists of two oxygen molecules. When an oxygen molecule (O2) is struck by UV radiation, it splits into two separate oxygen atomsFree oxygen molecules can then combine with oxygen molecules to create ozone, or O3.Over hundreds of millions of years, more and more ozone began to build up in the earth’s atmosphere, which is miles above the earth’s surface and begins to form the ozone layer.+O2
29O O2 + UV + O3 (ozone) O2 O2 O + + heat O3 (ozone) + O2 O + O3 (ozone) Once in the atmosphere, the oxygen atoms and molecules behave in predictable ways, especially because ozone is highly unstable (e.g., almost any opportunity to break down, it will). There are three primary reactions that occur:Ozone absorbs UV radiation and is broken down into O and O2.Some of these free oxygen atoms then either combine with other ozone to form more oxygen:Or…. They recombine with existing oxygen to re-form ozone and release heat into the atmosphere.It is in this way that the stratospheric ozone “shields” us from UV radiation. It doesn’t really “reflect” the heat like a mirror, but rather absorbs it and transforms it into heat which is released back into space.In addition to ozone break down from UV radiation, there are other natural causes of its breakdown:nitrogen and chlorine are released from oceans in fine sea mist, which will react with ozone.volcanic activity release chlorine, hydrogen, and nitrogen which will also react with ozone.The process of O3 breaking into its constituents O2 and O, and cycling back again, is a natural process.Over the course of one billion or so years, the stratosphere has reached a dynamic equilibrium between the oxygen compounds.O2O+
30Cl- “Free Radicals”… O3 (ozone) ClO O2 + + ClO O2 + O + Cl- Cl- So the chlorine is a “free radical” (like a free agent in baseball).Their hypothesis—after following its logical chemistry—was that this free radical would then create chlorine oxide, which is unstable. It naturally attracts single oxygen atoms, thereby producing an oxygen molecule and once again freeing the free radical!This produces a self-perpetuating cycle that can continuously break down ozone molecules. In other words, a single molecule of CFC, once it reaches the stratosphere, could break down more than 100,000 molecules of ozone as the chlorine continuously frees itself.This short, elegant study was the basis for awarding these two men the Nobel Prize in Chemistry in 1995 for their research findings in this groundbreaking study.O2+O+
31Effects of Ozone Depletion The damage to ozone layer will result in damage to plants and animalsFor every 2.5 cm increase in the size of ozone hole, there will be 5 – 6 % increase in skin cancer and cataracts.Ultraviolet rays may interfere with photosynthesis leading to lower crop yieldUltraviolet rays causes genetic changes in DNA, leading to lower crop yield.
32Control. Discourage use of CFCs and NOx Better alternative for CFC should be developed.Reforestation and forest prevention.
34Maximum ozone hole area for 2009 was 24 million km2 on 17 September. The Dobson unit (DU) is a unit of measurement of atmospheric ozone columnar density, specifically ozone in the stratospheric ozone layer. One Dobson unit refers to a layer of ozone that would be 10 µm (micrometre)