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SMOG

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  1. SMOG Ch. 18

  2. Smog • Localized air pollution in urban areas, mixture of pollutants that form with interaction with sunlight TYPES: • Brown • Gray

  3. Photochemical (Brown) Smog • Brown haze • Light initiates complex chemical reactions

  4. Photochemical Smog in Santiago, Chile

  5. Photochemical Smog Reaction • VOCs + NOx + Heat + Sunlight yields • Ground level O3 and other photochemical oxidants • Aldehydes • Other secondary pollutants

  6. PANS and other pollutants Volatile organic compounds (VOCs) Simplified Model Ozone (O3) Oxygen (O2) Nitric oxide (NO) + Oxygen atom (O) Water vapor (H2O) Hydrocarbons UV radiation Peroxyacyl nitrates (PANs) Nitrogen dioxide (NO2) Oxygen (O2) Nitric oxide (NO) Oxygen (O2) Burning fossil fuels Nitrogen (N) in fossil fuel Fig. 18-11, p. 475

  7. HOW? (Nitric Acid AKA Acid Rain) NO2 +UV NO + O 2NO + O2 2NO2 3NO2 + H2O 2HNO3 + NO N2 & O2 in air react @ high temps nitrogen monoxide Stinky, yellowish brown gas, haze above cities (Nitrogen dioxide) Forms nitric acid & Nitrogen monoxide

  8. HOW? Tropospheric Ozone (BAD!) NO2 +UV NO + O O + O2O3 Produces free oxygen Tropospheric ozone  O2 + hydrocarbons + NO PANS (peroxyacyl nitrates)

  9. Fig. 17-6 p. 424 Photochemical Smog Reaction

  10. Photochemical Oxidants • NO2, O3, PANS • Able to react with & oxidize compounds in atm. or our lungs • Respiratory health issues • Damaging to vegetation

  11. Smog • Hotter days = O3 & other components

  12. What’s location got to do with it? • Cities with sunny, warm & dry climates • Greater number of motor vehicles EX: LA; Salt Lake City, Utah; Syndey, Australia; Sao Paulo, Brazil; Bangkok, Thailand; Mexico City, Mexico and Santiago, Chile

  13. Industrial (Gray) Smog • Smoke pollution • Sulfur oxides • Particulates from burning coal/oil, • Problems in China/India/Russia due to lack of pollution controls on smokestacks

  14. Industrial Smog Reaction • When burned, most carbon in coal and oil converted to CO & CO2 • Soot = unburned coal (suspended particulates) • Sulfur dioxide & sulfuric acid created

  15. Ammonium sulfate [(NH 4 )2SO4] Ammonia (NH3) Sulfuric acid (H2SO4) Carbon monoxide (CO) and carbon dioxide (CO2) Water vapor (H2O) Sulfur trioxide (SO3) Oxygen (O2) Sulfur dioxide (SO2) Burning coal and oil Oxygen (O2) Sulfur (S) in coal and oil Carbon (C) in coal and oil Fig. 18-9, p. 474

  16. How? (Carbon) C + O2 CO2 + Soot (gray color) 2C + O2 2CO + Soot

  17. How? (Sulfur) S + O2 SO2 (suffocating gas) 2SO2+ O2 2SO3 SO3 + H2O H2SO4 (sulfuric acid, acid rain) 2NH3 + H2SO4 (NH4)2SO4 (Ammonium Sulfate – GRAY COLOR)

  18. Smog also creates greenhouse gases • Methane (CH4) • Nitrous Oxide (N2O

  19. What’s Location Got to Do With It? • Temperature differences help to disperse air pollutants preventing harmful buildup of air toxins • Ground air is warmed, rises, then cools = CONVECTION

  20. Temperature Inversions • Ground air colder than upper air – trap harmful pollutants near ground • Cooler air is denser than warmer air above it • Pollutants concentrate in stagnant cool layer • NO mixing due to density

  21. Types of Temperature Inversions • Subsidence - Warmer mass enters high altitude region and floats atop a colder air mass. Prevents vertical mixing.

  22. Types of Temperature Inversions • Subsidence

  23. Descending warm air mass Inversion layer Sea breeze Increasing altitude Mountain range Decreasing temperature Types of Temperature Inversions • Radiation – Occurs at night as ground air cools faster than air above. Sun rises and warms surface – dispersing pollutants that were trapped during night

  24. Types of Temperature Inversions*

  25. Where does this occur? • Valleys surrounded by mountains

  26. Where does this occur? • Near coastlines with sunny climage, and surrounded by mountains EX: Los Angeles, CA

  27. Where does this occur? • Leeward side of mountains