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Air Pollution

Air Pollution. Chapter 19. Atmosphere Quiz. Name the five layers of the atmosphere What are the four main gases found in air other than water? Name three primary air pollutants Name three secondary air pollutants. Five layers of the atmosphere. Troposphere Densest, 11 miles thick

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Air Pollution

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  1. Air Pollution Chapter 19

  2. Atmosphere Quiz • Name the five layers of the atmosphere • What are the four main gases found in air other than water? • Name three primary air pollutants • Name three secondary air pollutants

  3. Five layers of the atmosphere • Troposphere • Densest, 11 miles thick • Air cools with increased altitude • Ozone is poisonous here • Planes fly here • Weather occurs here

  4. Five layers of the atmosphere • Stratosphere • From 11 miles to 30 miles up from earth • Temperatures rise with increased altitude • Contains ozone layer

  5. Ozone layer • Blocks out 95% of UV radiation • Allows life to exist • Prevents sunburn/cancer of skin • Prevents oxygen in troposphere from converting into toxic ozone

  6. Five layers of the atmosphere • Mesosphere – middle layer, air cools with increased altitude • Thermosphere – air warms with increased altitude • Exosphere – air cools with increased altitude, blends to space

  7. What is in air • 78% nitrogen • 21% oxygen • 1% argon • < .1% carbon dioxide

  8. What does our atmosphere do? • Two main natural processes • Greenhouse effect – keeping the planet warm through absorbing long wave radiation from the planet (water, CO2, CH4) • Ozone shield – blocking unwanted UV radiation

  9. Primary pollutants • CO – carbon monoxide • CO2 – carbon dioxide • SO2 – sulfur dioxide • NO – Nitric oxide • NO2 – Nitrogen dioxide • Hydrocarbons • particulates

  10. Primary pollutants • Can be natural (volcano) but most are human released • Cars, industrial plants and power plants (especially coal) are main sources • When primary pollutants mix in air some form new secondary pollutants

  11. Secondary Pollutants • SO3 – sulfur trioxide • HNO3 – nitric acid • H2SO4 – sulfuric acid • H2O2 – hydrogen peroxide • O3 - ozone • PANs – peroxyacyl nitrates

  12. Human impact • We are altering natural balance of cycles in the atmosphere • Add ¼ more carbon dioxide (global warming) • Burn fossil fuels and use fertilizers releasing NOx into the air creating more acid rain (nitric acid) • Add sulfur to air from burning coal and refining petroleum (sulfuric acid)

  13. That’s only the beginning • Heavy metals • 2x the arsenic as nature releases • 7x the cadmium • 17x the lead It is hard to judge the effect on particulates, but we release large amounts of ash and dust

  14. Photochemical smog • Brown smog • Mostly Ozone, aldehydes, PANs and Nitric acid formed from NOx from cars/factories and volatile organic compounds (CH4, propane, benzene, CFCs) mixing in the presence of sunlight

  15. Smog chemistry • N2 + O2 = 2NO (engine of car) • Then in the air • 2NO + O2 = 2NO2 (brown haze) • Gives choking odor • 3NO2 + H2O = 2HNO3 + NO • Produces acid rain and some NO2 goes on to react this way • NO2 + UV = NO + O which then • O + O2 = O3 (ozone)

  16. More smog • Collectively NO2, O3, and PANs are known as chemical oxidants because they react easily with other compounds or in your lungs • Very small (trace) amounts can irritate respiratory tracts or damage crops/vegetation

  17. Industrial smog • Known as gray-air smog • Mostly SO2 and H2SO4 as well as suspended particles (ash) • Mostly caused by burning coal, but can be prevented with controls (scrubbers, etc.)

  18. When smog is a real problem • Thermal inversion – a layer of warm air sits on top of a cold layer trapping pollutants that would normally disperse. This causes air pollutants to rise to harmful or deadly levels

  19. Ughh! • Enough bad news for one day.

  20. Industrial smog • C + O2 = CO2 and CO and soot • S + O2 = SO2 • 2SO2 + O2 = 2SO3 • SO3 + H2O = H2SO4 • H2SO4 + 2NH3 = (NH4)2SO4 (salt) + soot give the gray color

  21. Acid deposition • Acid rain – wet acid • Acid deposition – dry acid (solid or a gas) • Natural rain is pH 5 – 5.6 (without acid) CO2 is dissolved from air forming weak carbonic acid

  22. Who/Where is affected? • Areas that are downwind from industrial or dense urban zones are in greatest risk of damage due to acid deposition • Vegetation and aquatic life receive most of the damage

  23. Acid protection • Natural buffers in soil – Ca+ and Mg+ can react and neutralize acids. • Thin acidic soils offer no buffering

  24. Acid production • Factories, power plants, smelters and cars produce the most acid • Acid crosses large distances via the wind and can still damage “clean” nations/areas

  25. Acid associated problems • Humans – respiratory (bronchitis and asthma) • Buildings – premature aging • Trees – weakens leaves, disease pest can then kill tree • Soil – release metals (toxic) like aluminum (3rd most abundant element in crust) which can kill fish by producing excess mucus

  26. Acid associated problems continued… • Aquatic – release methylmercury from natural mercury which accumulates to toxic levels in fish

  27. Acid prevention • Reduce energy use • Switch from coal to cleaner energy sources • Remove sulfur from coal before burning • Remove SO2, NOx and particulates from smokestacks with scrubbers • Remove NO2 from car exhaust

  28. More acid cleanup • Limestone can be added to lakes to neutralize acid, but it is hard to determine how much and liming can kill some organisms

  29. Let’s step inside • Indoor air pollution • Carbon monoxide • Asbestos • Nitrogen oxide • Trichloroethane (aerosols, dry cleaning) • Chloroform (chlorine in hot water) • Radon (gas from uranium-238) • Tobacco smoke • Formaldehyde – particle board, furniture • Styrene – carpet, plastics

  30. What does it do • Smoke – cancer, asthma, bronchitus • CO – dizziness, headache, heart attack • Pm10 – respiratory disease, cancer • SO2 – restricted airway • NO – lung irritation, asthma, encourage spread of cancer • VOCs (benzene and formaldehyde) and toxic particulates (lead, cadmium, PCB, dioxins) – mutations, reproductive problems

  31. Ozone hurts trees • As well as harming humans in the troposphere, ozone affects plants and trees • Damage to leaves through pores • Reduced wax coating • Reduced photosynthesis • Reduced nutrient uptake

  32. Regulation/protection • Clean air act • Sets nation limits for seven pollutants – pm10, SO2, CO, Nox, O3, VOCs, and lead • Also prevents significant deterioration in any area • EPA set levels for 302 individual compounds and 20 categories of toxic compounds

  33. Improving the Laws • Switch from cleanup to prevention • Conservation/alternate energy sources (no fossil fuels) • Stricter emission standards • Eliminate trash incineration

  34. Emission controls for smokestacks • Electrostatic precipitator • Baghouse filter – good for pm10 • Cyclone separator • Wet scrubber • All collect toxic solids which then must be disposed of as hazardous waste

  35. Reducing indoor air pollution • Better venting • In developing countries – better stoves, no smoke in the house • Use natural fibers • Reduce use of household cleaners with harsh chemicals • No dry cleaning

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