Chapter  22   Air
contentsYou will learn about:• air pollutants, its sources and  effects• The ozone hole• Global warming
air pollution                        Air around us contains pollutants,                        which are harmful substance...
air pollution                                            Harmful          Treatment orPollutants       Major Sources      ...
air pollutioncarbon monoxide (CO) colourless and odourless gas comes from the incomplete combustion of fuel in vehicles;...
air pollutionsulphur dioxide (SO2) fuels (coal and petroleum) contain sulphur as an impurity;  when fuels are burnt, sulp...
air pollutionnitrogen oxides (NO and NO2) oxides of nitrogen (NO and NO2) are produced naturally in  lightning and forest...
air pollutionacid rain                                    gases react with air                                    and wate...
air pollutionacid rain sulphur dioxide (SO2) and nitrogen dioxide (NO2) are  acidic oxides that react with oxygen and wat...
air pollutionacid rain harmful effects:  o   corrodes the cement and stones used in buildings  o   corrodes the steel str...
air pollutionacid rain prevention: o   burn fuels that contain less sulphur o   neutralise acidic oxides from power stati...
air pollutionozone and hydrocarbons ozone, O3, at ground level is a nasty pollutant irritates people’s eyes, chests and ...
air pollutionpollution from motor vehicles exhaust gases from a motorcar engine consist of CO2, CO,  hydrocarbons, H2, ni...
air pollutionmethane (CH4) small amounts of methane are naturally present in the  atmosphere; bacterial decay of vegetati...
the ozone holechlorofluorocarbons (CFCs) are compounds of carbon, chlorine and fluorine; gases at  room conditions; liqui...
the ozone holechlorofluorocarbons (CFCs) are chemically unreactive and do not burn uses of CFCs:  o aerosol propellants ...
the ozone holethe ozone hole the Earth is protected by a layer of ozone about 40km  above the ground this layer of ozone...
the ozone holethe ozone hole chlorine atoms from CFCs destroy the ozone molecules;  amount of ozone in the ozone layer de...
global warmingthe carbon cycle shows the movement of carbon 0.03% of the atmosphere is CO2 CO2 in the air is continuall...
global warmingthe carbon cycle                                          Carbon dioxide in the air       combustion        ...
global warmingglobal warming global warming is largely caused by increasing CO2 and  other heat trapping gases (e.g. meth...
global warmingglobal warming results in rise in sea levels, flooding of low-lying lands,  melting of polar ice caps and c...
combustion of                                                   photosynthesis                        carbon fuels        ...
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Airpollutants

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Airpollutants

  1. 1. Chapter 22 Air
  2. 2. contentsYou will learn about:• air pollutants, its sources and effects• The ozone hole• Global warming
  3. 3. air pollution Air around us contains pollutants, which are harmful substances to the environment Harmful Treatment orPollutants Major Sources Effects Prevention supply excess air to headaches; ensure complete carbon incomplete combustion breathing combustion; fitmonoxide of carbon fuels difficulties; can vehicles with kill people catalytic converters bacterial decay of methane vegetation; farm global warming no easy solutions animals and rice growing breathing difficulties; oxides of lightning; vehicle fit vehicles with acid rain; nitrogen engines catalytic converters produces ozone
  4. 4. air pollution Harmful Treatment orPollutants Major Sources Effects Prevention sunlight acting on irritates eyes reduce vehicle ozone unburnt hydrocarbons and lungs; emissions of and nitrogen dioxide asthma attacks pollutants breathing burn less sulphur- combustion of fossil difficulties; containing fuels; sulphur fuels – especially coal; asthma absorb SO2 from dioxide volcanoes’ eruptions attacks; acid chimney gases with rain calcium carbonate unburnt produces fit vehicles with vehicle engineshydrocarbons ozone catalytic converters
  5. 5. air pollutioncarbon monoxide (CO) colourless and odourless gas comes from the incomplete combustion of fuel in vehicles; all new motor cars in Singapore are fitted with catalytic converters; oxidises CO to CO2 can be absorbed by haemoglobin in the blood, thus blood can no longer absorb O2 extra amounts of CO result in tiredness, headaches, heart damage and small amounts can be lethal
  6. 6. air pollutionsulphur dioxide (SO2) fuels (coal and petroleum) contain sulphur as an impurity; when fuels are burnt, sulphur is oxidised to SO2 is also emitted from volcanoes’ eruptions irritates the eyes and causes breathing difficulties; main cause of acid rain in Singapore, there are measures to reduce the emission of SO2 into the atmosphere: o oil fuels are not allowed to contain more than 2% sulphur o exhaust gases from power stations and industries are treated with CaCO3 to remove acidic SO2 volcanoes: natural source of SO2 pollution
  7. 7. air pollutionnitrogen oxides (NO and NO2) oxides of nitrogen (NO and NO2) are produced naturally in lightning and forest fires excess man-made production of oxides of nitrogen is harmful; found inside motorcar engines, power stations and industries damage people’s lungs and react with other pollutants to form ozone preventive measure: motorcars are fitted with catalytic converters to reduce oxides of nitrogen to N2
  8. 8. air pollutionacid rain gases react with air and water in clouds sulphuric acid nitric acid gases damage ACID RAIN green leaves acid corrodes buildings and metal structures coal, oil, fossil lakes fuels burned soils acidified acidified acid damages acid kills trees through fish roots
  9. 9. air pollutionacid rain sulphur dioxide (SO2) and nitrogen dioxide (NO2) are acidic oxides that react with oxygen and water vapour in the air to form sulphuric acid and nitric acid which become acid rain SO2 + oxygen + water vapour sulphuric acid NO2 + oxygen + water vapour nitric acid acidic atmosphere acid rain oxides typical pH of acid rain is 4 which is 1000 times more acidic than clean water
  10. 10. air pollutionacid rain harmful effects: o corrodes the cement and stones used in buildings o corrodes the steel structures such as fences and bridges o kills fishes in fresh water lakes o makes agricultural land acidic thus crops grow poorly damage to left statue caused by acid rain
  11. 11. air pollutionacid rain prevention: o burn fuels that contain less sulphur o neutralise acidic oxides from power stations with alkalis before they are released into the atmosphere o fit motor cars with catalytic converters to reduce the emission of nitrogen oxides o adding calcium hydroxide to lakes and soils to neutralise the acid
  12. 12. air pollutionozone and hydrocarbons ozone, O3, at ground level is a nasty pollutant irritates people’s eyes, chests and throats and causes breathing difficulties produced by the action of sunlight on pollutants such as NO2 and hydrocarbons; formation of a ‘photochemical smog’ preventive measure: reduce the emissions of unburnt hydrocarbon fuels sunlight reacting with unburnt hydrocarbons from vehicle exhausts causing formation of ozone
  13. 13. air pollutionpollution from motor vehicles exhaust gases from a motorcar engine consist of CO2, CO, hydrocarbons, H2, nitrogen oxides, lead compounds and other non-polluting gases measures have been taken to reduce this pollution: o introduction of lead-free petrol (Singapore stopped using leaded petrol in 1998) o oxygen sensor and modified distributor are used to ensure more complete combustion o catalytic converters are fitted in cars to remove the pollutants
  14. 14. air pollutionmethane (CH4) small amounts of methane are naturally present in the atmosphere; bacterial decay of vegetation and other sources increasing amount of methane in recent years observed; human activities such as agriculture, mining and waste disposal methane (heat- trapping gas) causes ‘greenhouse effect’ / global warming rice fields are a major source of methane
  15. 15. the ozone holechlorofluorocarbons (CFCs) are compounds of carbon, chlorine and fluorine; gases at room conditions; liquids under a small pressure examples of CFCs: CFCl3 and CF2Cl2 model of a CFC molecule, CFCl3
  16. 16. the ozone holechlorofluorocarbons (CFCs) are chemically unreactive and do not burn uses of CFCs: o aerosol propellants o coolant fluids for refrigerators and air conditioners o good solvents to clean grease from silicon chips CFCs molecules rise up into the atmosphere and are decomposed by sunlight to produce chlorine atoms aerosol cans and foam plastic are sources of CFCs
  17. 17. the ozone holethe ozone hole the Earth is protected by a layer of ozone about 40km above the ground this layer of ozone absorbs harmful ultraviolet(UV) radiation from the Sun harmful UV radiation from the Sun ozone hole ozone layer South Pole Antarctica
  18. 18. the ozone holethe ozone hole chlorine atoms from CFCs destroy the ozone molecules; amount of ozone in the ozone layer decreases formation of the ozone hole; dangerous UV radiation streamed through the hole causes skin cancer an damage to vegetation use of CFCs is phased out to protect the ozone layer
  19. 19. global warmingthe carbon cycle shows the movement of carbon 0.03% of the atmosphere is CO2 CO2 in the air is continually being removed by green plants in photosynthesis; it is then replaced by other processes (e.g. combustion and respiration) this two-way process has been in balance over the past few millennia; amount of CO2 in the atmosphere remained fairly constant however, with global industrialisation and increased use of fossil fuels, amount of CO2 in the atmosphere increases; resulting in global warming
  20. 20. global warmingthe carbon cycle Carbon dioxide in the air combustion hea t an da cid r ain Fossil fuels Carbon dioxide (coal, petroleum, Limestone chalk in the sea death, decay and respiration natural gas) death and decay photosynthesis decay and pressure over millions Sea shells of years eating Plants Animals
  21. 21. global warmingglobal warming global warming is largely caused by increasing CO2 and other heat trapping gases (e.g. methane) in the atmosphere large amount of heat trapped on Earth; Earth becomes hotter carbon dioxide and some radiation from methane trap radiation by the Sun radiated back reflecting it back to Earth into space radiation from the Sun reaches the Earth’s surface vehicles rice fields and decaying vegetation factories and mining power station
  22. 22. global warmingglobal warming results in rise in sea levels, flooding of low-lying lands, melting of polar ice caps and changes in global climate measures to reduce use of fossil fuels (to reduce CO2 emission): o use tidal, wind and hydroelectric energy to generate electricity o use of solar energy
  23. 23. combustion of photosynthesis carbon fuels nitrogen and respiration removed argon and from air by added to oxygen other gases global inc air by lud warming es by CO2 se d contains excess of is cau contains is air pollutants methane are are is aresulphur are carbondioxide des are monoxide unburnt CFCs troy nitrogen hydrocarbons ing c au protective aus oxides is se e ozone layer cau causes se petrolchemicalacid rain ozone smog

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