Air Pollution Types of air pollutants

Size: px
Start display at page:

Download "Air Pollution Types of air pollutants"

Transcription

1

2

3

4

5 Air Pollution Types of air pollutants 1.Carbon compounds (e.g., CO2,CO) 2.Sulphur compounds (e.g., SO2, H2S and H2SO4) 3.Nitrogen oxides (e.g., NO, NO2 and HNO3 ) 4.Ozone (e.g., O3) 5.Fluorocarbons 6.Hydrocarbons (e.g., benzene, benzyprene, etc.) 7.Metal (e.g., lead, nickel, arsenic, beryllium, tin, vanadium, titanium, etc.) 8.Photochemical products (e.g., olefins, aldehydes photochemical smog, PAN, PB2N, etc.) 9.Particulate matter (e.g., fly ash, dust, grit) and 10.Toxicants.

6 1. Carbon compounds (eg,co2,co)

7 2.Sulphur compounds(eg,so2, H2S and H2SO4)

8 3. Nitrogen oxides ( e.g., NO, NO2 and HNO3)

9 4.Ozone (e.g., O3)

10 5. Fluorocarbons

11 6. Hydrocarbons (e.g., benzene, benzyprene, etc.)

12 7. Metal (e.g. lead, nickel, arsenic, beryllium, tin, vanadium, titanium, etc) Lead Arsenic

13 Tin Titanium

14 8. Photochemical products (e.g., olefins, aldehydes photochemical smog, PAN, PB2N, etc)

15 9. Particulate matter ( e.g., fly ash, dust, grit)

16 10. Toxicants

17

18 Green House Gases The gases responsible for raising the temperature of the earth and its atmosphere are referred to as green house gases. These gases have the ability to absorb inferred radiation reflected from the earth surface. Therefore, the blanket of these gases in the atmosphere trap all the infra-red rays which produce heat on the earth surface. The heating of earth s atmosphere due to trapped infra-red rays reflected from the earth surface is called Green House Effect which cause global warming.

19 Major Green house gases from human activities Green house Gas Sources Carbon dioxide Burning of fossil fuel, especially coal, deforestation plant burning Methane Rice paddies, termites, landfills, coal seams, gas leaks from oil and gas production and pipelines Nitrous oxide Fossil fuel burning, fertilizer animal wastes Chlorofluorocarbon (CFCs) Air-conditioners, refrigerators Hydrochlorofluoro carbons (HCFCs) Air conditioners, refrigerators Hydrofluorocarbons (HFCs) Air-conditioners, refrigerators Halons Fire extinguishers

20 Carbon Compound (CO, CO2)

21 Carbon monoxide (CO) Carbon monoxide gas is formed by incomplete combustion of fossil fuel like coal and petroleum, or other organic matter. Automobiles are the commonest source of carbon monoxide pollution in cities. Other common sources are oil refineries, metallurgical operations and other internal combustion engines.

22 It is a major pollutant for man and other animals as it combines with blood haemoglobin more than 200 times faster than oxygen does. Therefore, in rooms, with burning coal even while the oxygen content may not be so deficient, carbon monoxide produced causes suffocation. It is estimated that this gas accounts for about half of the total air pollutants added to atmosphere. Vegetation and soil are regarded as a natural sink for carbon monoxide pollution.

23 Carbon dioxide (CO) Carbon dioxide is a resource at its natural level of 0.03% as it is the raw material of photosynthetic reaction by which food is prepared by green plants and on this food ultimately all organisms including man depend. Carbon dioxide is a product of respiration and all living cells respire. The CO2 so produced is naturally balanced by its photosynthetic utilization.

24 However, two very important human activities: (i) the burning of fossil fuels (ii) destruction of forests have resulted in an imbalance of CO2 cycling. Its content in air is rising due to higher release and lower utilization and causing Green House Effect of warming up of air. In nature, the rise in CO2 is necessarily accompanied with decrease in O2 content which has harmful effects on human health. Thus CO2 increase has manifold adverse effects particularly on oxygen deficiency and green house effect on global weather and climate.

25 Impacts of Global warming on Human Health As a result of global warming human populations will be displaced. In a warmer climate people will get more frequently sick. Diseases now found in the warm tropical areas will spread to new regions. Many diseases are transmitted by mosquitoes and other animals when these animals will move into colder regions. Other tropical diseases including dengue fever, yellow fever and encephalitis may spread into new regions. It is also predicted that there will be rising incidence of allergies and respiratory disease, as warmer air is more charged with pollutants, fungal spores and pollens.

26 Global Warming

27 Atmosphere

28 Chlorofluorocarbons (CFCs) Chlorofluorocarbons or CFCs are chemicals synthesized by man for use in several kinds of industries including refrigeration and air conditioning and find their way into the atmosphere. CFCsare highly stable and non destructive. They slowly reach the upper zone of the atmosphere where ultra violet radiation decomposes them. It is estimated that if the CFCs emission is totally stopped now, it will take about 100 years for its breakdown or in stopping its migration from troposphere to stratosphere, but there is little hope for reduction in its emission. The chlorine molecules combine with ozone to produce oxygen and CIO and CIO again combines with O3 to produce 2O2 and CI. Thus the chlorine of CFCs acts as a catalyst to break ozone into oxygen.

29 Methane (CH4) Methane (CH4) is another greenhouse gas which is naturally produced. In recent years its production and release into the atmosphere appears to have increased due to human influence.

30 The main sources are biological processes such as enteric fermentation in cattle, sheep and other animals, anaerobic situations in wetlands and rice fields and burning of biomass and fossil fuel by man. Methane gas increases stratospheric water vapour on oxidation. The rise in water vapour is really a more important source of greenhouse effect than the direct effect of methane gas.

31 Nitrous oxide (N2O) Nitrous oxide (N2O) is emitted from the burning of fossile fuel. Its content is also reported to be rising all over the world. Current rate of increase is about 0.2 % to 0.3 % per year. Some of the N2O reaching into the air is from the breakdown (or denitrification processes) of manures and fertilizers. One N2O reaches the air it does not change its form for many year. Only on reaching the upper layers it slowly reacts with atomic oxygen.

32 Sulphur dioxide (S2O) and hydrogen sulphide (HS) These gaseous pollutants are naturally released by the biological decomposition and from volcanic eruptions. They are also released artificially due to activities such as smelting of sulphide containing ores, combustion of sulphur containing fuels such as coal and oil, petroleum refining and obtaining of geothermal energy. Since the quantity of burning of such fossil fuels is fantastic, the quantity of sulphur dioxide emitted into the atmosphere is in the order of more than a hundred thousand tons each day. This gas is also quite harmful causing diseases of eye, throat and lungs.

33 Smoke occurring in combination with fog is called smog. Under such a condition SO2 reacts with O2 and SO3 is formed which in turn combines with water to form H2SO4. In such a case sulphur dioxide would be called as primary pollutant since this gas itself is a pollutant and H2SO3 as secondary pollutants. Sulphuric acid corrodes many of the building and marble structures.

34 Hydro carbons (HC) Hydrocarbons, which are a variety of chemicals, are emitted in huge quantity by the burning of petrol in automobiles. These are quite harmful and frequently combine with NO2 and produce photochemical smog.

35 Ozone (O3) Ozone mantle or shield or umbrella as the layer is called around km attitude in the atmosphere is extremely important as it absorb the ultraviolet (UV) radiation. UV radiations are of short wavelengths between mm nm is called UV-C: nm UV-B and nm as UV-A. Out of the three categories, UV-B is most dangerous to plants and animals.

36 It affects the living organisms in many ways sunburn, ageing, wrinkling of skin, cataract of eye, destruction of protein, mutation of genes leading to skin cancer or melanoma, etc. are some of the common effect of UV radiation on human population. Ozone causes pollution when occurring in concentrations higher than 15 to 20 ppm. Ozone injures first the plasma membrane and then reacts with proteins and fatty acids. If the ozone stress is withdrawn, most plants, recover, but the exposure effect persists for a long period.

37 Air pollutants. These are the gases, along with their sources, that contribute to four environmental effects of major concern photochemical smog, acid deposition, the greenhouse effect, and destruction of the ozone shield. An examination of the sources of these gases shows that vehicle exhaust and fossil fuel burning are the chief contributors.

38 Particulate matter which are small to very small in size that keep floating in the air. Particles around one micron in size present in air in the form of solid or liquid are generally called as aerosol. Particles smaller than aerosol assume the appearance of smokes and fumes while larger than the aerosol are dusts if the particles are solid and mist if they are liquid droplets.

39 Other particulate pollutants are either living like bacteria, pollen grain, fungal and other spores, or non-living like flyash from burning coal and wood, chemical, compounds from metallurgical industries and lead combined with chlorine and bromine, etc.

40