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https://docs.google.com/document/d/1cNd1rpaRzTrJDdadbklVBcSNCxEXJ6m7/edit?usp=sharing&ouid=109474854956598892099&rtpof=true&sd=tru pollution - Tropospheric and stratospheric, Tropospheric pollutants - Gaseous pollutants: Oxides of carbon, nitrogen and sulphur, hydrocarbons; their sources, harmful effects and prevention; Green house effect and Global warming; Acid rain; Particulate pollutants: Smoke, dust, smog, fumes, mist; their sources, harmful effects and prevention. Stratospheric pollution- Formation and breakdown of ozone, depletion of ozone layer - its mechanism and effects. Water Pollution - Major pollutants such as, pathogens, organic wastes and chemical pollutants; their harmful effects and prevention. Soil pollution - Major pollutants such as: Pesticides (insecticides,. herbicides and fungicides), their harmful effects and prevention. Strategies to control environmental pollution. ENVIRONMENTAL POLLUTANTS CHAPTER Any substance which causes pollution in the environment is known as INCLUDES environmental pollutant. WATER POLLUTION The quality of drinking water is very important for human welfare. The pollution of water by sewage has been linked with the spreading of diseases such as cholera and typhoid fever. In addition, industrial wastes also contaminate water. Heavy Metals : Such as Cd, Pb and Hg may be present. Environmental Pollutants Water Pollution Air Pollution Detergent and Fertilizers : The may contain PO–3 as additives which encourages the formation of algae which reduces the dissolved oxygen concentration of water. This process known as Eutrophication. Acid Polluted Water (pH < 3) : This is deadly to most forms of aquatic life. Acid Rain Polychlorinated Biphenyls (PCBs) : PCBs are resistant to oxidation and ● Ozone and Reactions their release into the environment causes skin disorders in humans. They are reported to be carcinogenic. Determination of quality of waste water : It is done through BOD and COD. Biological : Oxygen demand (BOD) - is the amount of oxygen required for biological oxidation by microbes in any unit volume of water. This test is done for at least 5 days. BOD values generally approximates the amount of oxidisable organic matter. Chemical oxygen demand (COD) : BOD measurement takes a few days, so another parameter called COD measurement is required. In COD measurement sample of fixed volume is treated with oxidising agent (usually K2Cr2O7 in acidic medium). The reagent oxidises most of the polluting substances including those which are resistant to microbial oxidation. The remaining K2Cr2O7 is determined by back titration from the concentration of K2Cr2O7 consumed the amount of oxygen used can be calculated. Causing Ozone Depletion AIR POLLUTION Air is very essential for life, particularly oxygen is needed for breathing. But air is never found clean due to the pollution caused by various activities both natural as well as human. Man made pollutants such as gases like CO, NO, NO2 , SO2 , H2SO4 , hydrocarbons and aerosols etc are being constantly released in the atmosphere leading to air pollution. Atmospheric Pollution Tropospheric pollution : Troposphere extends upto height of 10km from sea level. It contains 80 % of total mass of air and almost all of H2O vapour pollution caused by SO2, SO3, NO2 etc Stratospheric pollution : Extends (10–50) km above sea level. It contains N2, O2 and ozone. Table : Sources of Air Pollution Sl. No. Class Aerosols Gases and Vapours 1. Combustion processes Dust, fumes, smoke SO2, NO2, CO, Organic vapours Process dependent (CO2, SO2, CO, NH3, NO2 organic vapours) SO2, H2S, NH3, CO, hydrocarbons mercaptans SO2, CO, fluorides, organic vapours Process dependent Odouroys materials Organic phosphates, chlorinated hydro sulphur oxide, organic vapours Fluorides, I-131, Ar-41 radioactive gases ( Sr-90, Cs-137, C-14 etc. ) 2. Chemical processes Dust, fume, mist (cement and fertilizers) 3. Petroleum operations Dust, mist 4. Metallurgical processes Dust, fumes (Al-refineries, steel plant) 5. Mineral processing Dust, fumes 6. Food and feed operation Dust, mist 7. Agricultural activities Dust, mist, crop spraying, field burning smoke flyash 8. Nuclear energy programme Dust (i) Fuel fabrication (ii) Ore preparation (iii) Bomb explosion Smog Combination of 2 words smoke and fog. This is the best known example of air pollution. Smog is of 2 types : Classical smog : Occurs in cool humid climate and is chemicaly reducing smog and has high concentration of SO2. Photochemical smog : Occurs in warm, dry and sunny climate. It is an oxidsing smog. Major component of photo chemical smog is NO. Formation of photochemical smog : NO is oxidised in air to NO2 and NO2 breaks to NO and O. NO2 ⎯⎯h⎯ν → NO + O This atomic O produces ozone. O + O2 ⎯⎯→ O3 O3 undergoes many reactions constituting the smog O3 + NO ⎯⎯→ NO2 + O2 The other products formed are formaldehyde, acrolein and peroxyacetyl nitrate (PAN). Acid Rain Rain water normaly has pH of 5.6 due to the formation of H+ ions from the reaction of rain water with CO2 present in atmosphere. H O(l) + CO (g) ⎯→ 2H+(aq) + CO–2(aq) . 2 2 3 When pH of rain water drops below 5.6 it becomes acidic. Acid rain caused by the presence of oxides of sulphur and nitrogen in the atmosphere. Oxides of sulphur are released into the environment largely because of fossil fuel combustion, ore smelting etc. Nitrogen oxides emitted into the atmosphere mainly from automobile exausts and fossil fuel combustion. SO2 and NO2 after oxidation and reaction with water are major contributors to acid rain. 2SO2(g) + O2(g) + 2H2O(l) ⎯→ 2H2SO4(aq) 4NO2(g) + O2(g) + 2H2O(l) ⎯→ 4HNO3(aq). Acid rain is toxic to vegetation and aquatic life. It damages building and statues and dissolves heavy metals from soils, rocks etc. The heavy metals such as Cu, Pb, Hg, Al etc leached from soil enter well waters and produce a variety of toxic effect. OZONE AND REACTIONS CAUSING OZONE LAYER DEPLETION Ozone (O3) a light bluish gas found in the stratosphere, absorbs ultraviolet (UV) radiation of the sun which is harmful to the living things. O3 therefore act as one of the earth's most important life support system. In recent years however there have been reports of the depletion of this protective ozone layer. The major cause of ozone layer depletion is believed to be the release of chlorofluoro carbon compounds (CFCS), also known as freons into the atmosphere. These compounds enter its upper layers where they get broken down by the powerful UV radiation emitted by the sun. The life time of CF2Cl2 (CFC-12) is 139 years while that of CFCl3 (CFC-11) is about 77 years. The decomposition product destroy ozone as is clear from the following reactions. CF2Cl2(g) + hν ⎯→ Cl∙(g) + ∙CF2Cl(g) Highly reactive chlorine free radical (Cl) reacts with ozone to form chlorine monoxide. . Cl(g) + O3(g) ⎯→ ClO∙(g) + O2(g) ClO∙(g) + O(g) ⎯→ Cl∙(g) + O2(g) It has been shown that over one thousand ozone molecules, can be destroyed by one Cl∙(g). Effect of the Depletion of Ozone Layer Following are the main effect of ozone layer depletion in stratosphere Increased human cataracts Skin cancer Reduction of planktons in ocean waters Depletion of plants and crops etc. SOIL POLLUTION It is caused by pesticides and other chemicals which are added to the soil to grow better crops. Solid wastes are another cause of land pollution. Pesticides are used to kill unwanted organisms. Synthetic pesticides are concern to us. Pesticides affects human being through eating of food, drinking water. These pesticides can be classified in three ways. Classification Insecticides : Control of insects by insecticides help to curb disease for e.g, (malaria and yellow fever) and protects crops. e.g., organo- chlorine like DDT. Bhopal gas tragedy Occured in 2nd Dec., 1984 in Bhopal (United Carbide Ltd.) point. Methyl iso-cyanate was used to manufacture the insecticide called Carbaryl or Sevin (commercial name). There were three tanks in the plants that stored MIC. Due to increase of pressure in one of the tanks so its valve released so MIC escaped into atmosphere. This MIC was Hydrolysed due to presence of water in surrounding ponds. CH3 — N= C = O + H2O CH3NH2 + CO2↑ + ΔH Impurities present in water of metals which caused polymerisation reaction 3 CH3–NCO Catalyst + Q CH3 Both above reactions are exothermic in nature. So escaping tendency of MIC increased and caused immense loss of life and injury to people and life stock. Recycling Sewage treatment Incineration Digestion Dumping (For glass bottles, metal scraps etc) (process removes grease) (provides means to dispose of the relatively inert PCBs) (used in conversion of organic matters in CO2 and H2O) (sludge contain N and P, which makes it useful as fertiliser) Herbicides used to kill weeds. e.g., NaClO3 and Na3AsO3 etc. Organic herbicides as triazines are presently widely used to kill weeds in cornfields. Fungicides are used to kill fungi. Since fungi are plants without chlorophyll. Organic compounds of Mercury (CH3)2Hg have been used as fungicides. Methyl mecury as a fungicide was used in bread resulted human deaths in Iraq. ❑ ❑ ❑