atmospheric chemistry

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different gasses in atmosphere and their effects

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atmospheric chemistry

  1. 1. Assignment Of Anthropology Roll # 1774 Submitted by : Asma Sattar Submitted to : Ma’m Sobia Department Of Environment Science 2nd Semester : 2011-2015 GCUF Created by : 1
  2. 2. Contents 1. 2. 3. 4. Atmospheric chemistry definition Atmospheric composition Visuals of composition of Earth’s atmosphere Essential gasses and harmful gasses      5. 3 4 5 6 Carbon mono oxide Nitrogen oxides Hydro oxides Sulphur oxides Mercury emissions 7 8 9 10 11 Atmospheric problems 12 Acid rain Smog Global warming Ozone depletion 12 14 16 17     6. Slide no. References 20 2
  3. 3. • Definition: Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the earth atmosphere and that of other planets is studied, the was gases, liquids and solids in the atmosphere interact with each other and with earth’s surface and associated biota, and how human activities may be changing the chemical and physical characteristics of the atmosphere. 3
  4. 4. Atmospheric composition The atmosphere is compose of mixture of gases in different proportions. i.e., Average composition of dry atmosphere (mole fractions)  Nitrogen, N2: 78.084%  Oxygen, O2: 20.946%  Argon, Ar: 0.934%        Minor constituents (mole fractions in ppm) Carbon dioxide, CO2: 383 Neon, Ne: 18.18 Helium, He: 5.24 Methane, CH4: 1.7 Krypton, Kr: 1.14 Hydrogen, H2: 0.55 Water Water vapor : highly variable 4
  5. 5. Visualization of composition by volume of Earth’s atmosphere: Diatomic molecules: nitrogen and oxygen are more dominant constituents of atmosphere Nobel gasses: Argon(Ar) is present in much higher concentration then neon, helium, krypton and xenon. Water vapors: accounts for roughly 0.25% of atmosphere, is a highly variable constituent with concentration ranging from around 10 ppmv in coldest region 5 and up to 5% by volume in hot region.
  6. 6. Essential gasses: O2: requires for breathing CO2: requires for plants photosynthesis N2: used by nitrogen fixing bacteria O3: absorb most of the cosmic rays and major proportion of electromagnetic radiations coming from the sun Water vapors: responsible for sustaining form of life on the Earth Harm full gases: Carbon monoxide Nitrogen oxides Sulphur oxides Hydro carbons Mercury emissions 6
  7. 7. Carbon monoxide Natural sources:  Volcanic eruption  Natural gas  Oxidation of methane Human activities:  Fuel burning in various types of transportation  Forest fires  Combustion of fossil fuel  Agricultural products Impacts:  Highly poisonous gas  Causes suffocation if inhaled  Bind blood hemoglobin  Exposure to high concentration of CO results in headache, fatigue, unconsciousness and eventually death. 7
  8. 8. Nitrogen oxides Natural sources:  Bacterial action produces NOx mainly NO Human activities:  Combustion of coil, oil, natural gas gasoline  Oxidation of nitrogenous compounds present in fossil fuels N2+O2 2NO 2NO+O2 2NO2 Impacts:  Acid rain  Dust particles 8
  9. 9. Hydro carbons oxides Natural sources:  Different trees and plants  Paddy field  Anaerobic decomposition of organic matter Human activities:  Auto mobiles  Petroleum  Coal , wood  Incinerators  Refuse burning  Solvent evaporator Impacts :  Global warming  Climate change  Smog  Air pollution 9
  10. 10. Sulphur oxide Natural sources:  Volcanoes 67%  Oxidation of sulphur containing gases produce by decomposition of organic matter Human activities:  Combustion of coal (containing 1-9%) crude oil and other fossil fuels in power plants and petroleum industry. S+O2  SO2 2SO2+O2  2SO2 Impacts:  Irritant and suffocating b/c of pungent odour  Acid deposition in atmosphere  Sulphate aerosols  Respiratory troubles among older people 10
  11. 11. Mercury emissions Natural sources:  Gold and silver mining Human activities:  Industries  Fluorescent lamps  The burning of coal  Cement production  Caustic soda production  Pig iron and steel production from batteries Impacts:  Methyl mercury accumulates in fish affect water quality 11
  12. 12. Atmospheric problem Acid rain: Acid rain is a mixture of sulphuric and nitric acids Wet deposition:  Rain  Hail Process involved in acid deposition  Snow  Fog Dry deposition:  Gasses and particles 12
  13. 13. Causes & chemistry: a) Acid reaction with sulphur  S+O SO2  2SO2+O2 2SO3  SO3+H2O H2SO4 b) Acid reaction with nitrogen  N2+O2 2NO  2NO+O2 2NO2  4NO3+O2+2H2O 4HNO3 Environmental effects: Water and marine life:  Extinction of fishes in lakes Flora:  Damage of plants, forest, crops tissues and death of whole tree Soil:  Improper growth of plants Human health:  Respiratory problems 13
  14. 14. Smog : Smog is a combination of smoke and fog Types : • Reducing smog • Oxidizing smog or photo chemical smog Conditions required for formation of smog: 1. 2. 3. Sufficient NO, hydro carbons, volatile organic compounds Sunlight Movement of air mass 14
  15. 15. Sources of smog Man made sources: • Vehicle exhaust • Industrial emissions • Biomass burning • Peg benzene Natural sources: • Vegetation • Trees • Rain forests • Isoprene 15
  16. 16. Global warming: Global warming is the rising average temperature of earth’s atmosphere and oceans and is caused by increasing concentration of green house gases. Green house gases: water vapors, methane, CO2, ozone, nitrous oxides, and chlorofluorocarbons. Effects of global warming: • Ice sheet melting • Rise in sea levels • Wildlife effects • Human health • Increase in hurricanes 16
  17. 17. Ozone depletion: ozone layer protects the earth from the ultra violet rays sent down by the sun, if the ozone layer is depleted by human action are disastrous. Ozone is a relation of oxygen and is made of three oxygen atoms (O3). Reaction: ozone itself can be photolysed with weak ultra violet light and even with the light from the range of wavelengths which can be seen by the human eye. From the splitting of ozone, oxygen molecules (02) and atoms (O) are produced again. The atomic oxygen can collide with another ozone molecule and split it up, to produce two oxygen molecules. 17
  18. 18. The reactions of ozone synthesis and photolysis occur very quickly CFCl3 ----------> CFCl2 + Cl Cl + O3 ------------>ClO + O2 ClO + O--- -------> Cl + O2 18
  19. 19. Natural cause: Volcanoes and oceans releases large amount of chlorine Human activities: • chlorofluouro carbons (CFCs) • hydrofluoric carbons (HFCs) • ozone depleting substances (ODS) • methyl bromide ( used as pesticide) • halons (used in fire extinguishers) • methyl chloroform 19
  20. 20. References Websites :  www.environment.nationalgeographic.com  www.atmospheric-chemistry-and-physics.net  www.wikipedia.com  www.stuffintheair.com  www.amazon.com  http://wiki.answers.com/Q/what are some of the harmful gases being emitted into the atmosphere. Books:  Chemistry 12, 1st edition , publisher – Shaikh Barkat Ali & sons Lahore by Dr.Jamil Anwar & M.Akram Kashmiri 20

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