Major Air Pollutants and Their Sources

• Air pollution
  • Introduction of chemicals, particularly matter, or microorganisms into atm at concentrations high enough to harm life and alter ecosystems
  • Can occur naturally from volcanoes or fires, but humans have contributed to it as well

Air pollution is a global system

• Atm is a major repository for air pollution
  • Thus air pollution is a global system
  • Pollution in Asia has caused acid rain fall in US

Classifying Pollutants

• US Clean Air Act monitors and controls 6 criteria pollutants and more, stating allowed concentrations for the pollutants

  • Sulfur Dioxide
  • Nitrogen oxides
  • Carbon monoxide
  • Particulate matter
  • Lead
  • Ozone
  • VOCs
  • Mercury
  • Carbon dioxide

  Sulfur Dioxide

  • SO2
  • Corrosive gas that comes from combustion of fuel
  • Respiratory irritant

  Nitrogen Oxides

  • NOx
  • Can transform from NO to NO2 easily
  • 78% of atmosphere contains N2
  • From motor vehicles
  • Helps form ozone

  Carbon Oxides

  • CO
    • Colorless, odorless gas
    • Formed during INCOMPLETE COMBUSTION
    • Dangerous indoor pollutant
      • CO poisoning
  • CO2
    • Colorless, odorless gas
    • formed during COMPLETE COMBUSTION
    • Been rising increasingly

  PM

  • Particulate matter
  • Solid or liquid particles suspended in air
  • Comes from combustion of biofuel
  • PM 10 are harmful as they are not filtered out by our noses
  • PM 2.5 are even worse
  • PM can also scatter and absorb sunlight
    • Haze
      • Reduced visibility

  Photochemical Oxidants

  • Oxides remove electrons from other chemicals
  • Photochemical oxidants
    • Air pollutants formed from as a result of sunlight acting on compounds such as NOx
  • O3
    • Secondary pollutant
  • In presence of SOx and NOx, photochemical oxidants can enhance formation of certain particulate matter
    • Smog
      • Air pollution that is mix of oxidants and PM
      • Los Angeles type smog
        • Brown smog, sulfurous
      • London type smog
        • Gray smog, industrial

  Lead and other metals

  • Pb is a trace metal, occurring naturally in rocks
    • Was added into car fuel, but later removed
    • Still present in paints
    • Neurotoxin
  • Hg is another trace metal found in oil and fuel
    • Neurotoxin

  VOCs

  • Organic compound that evaporates at typical temp.
  • Hydrocarbons
  • Play important role in formation of Photochemical smog
  • Not hazardous directly

Primary and Secondary Pollutants

Primary

• Polluting compound that comes directly out of a smokestack, exhaust pipe, or natural emission source
• COx, NOx, SOx, PM, and VOCs

Secondary

• Primary pollutants that have been transformed
• Can occur due to light, water, oxygen, etc.
• Ozone is secondary pollutant formed from NOx and VOCs
• Focus on trying to reduce primary pollutants to reduce secondary

Air pollution comes from both natural and human sources

Natural Sources

• Volcanoes, lightning, forest fires, etc.
• Lightning strikes can create NOx
• Living organisms can release VOCs