Air Pollution and Stratospheric Ozone Depletion Notes

Major Air Pollutants and Their Sources

  • Air pollution: Introduction of harmful substances into the atmosphere.
  • Includes chemicals, particulate matter, or microorganisms.

Classifying Pollutants

  • Sulfur dioxide (SO_2): Corrosive gas from combustion of fuels like coal and oil.
  • Nitrogen Oxides (NO_x): From motor vehicles and fossil fuel combustion.
  • Carbon Oxides: Carbon monoxide (CO) from vehicle exhaust; Carbon dioxide (CO_2) from burning fossil fuels.
  • Particulate matter (PM): Solid or liquid particles suspended in air.
  • Photochemical oxidant: Pollutants formed by sunlight acting on compounds like nitrogen oxides.
  • Ozone (O_3): Secondary pollutant made of three oxygen atoms.
  • Smog: Mixture of oxidants and particulate matter.
  • Lead: Gasoline additive; impairs the central nervous system.
  • Volatile organic compound (VOC): Organic compound that evaporates easily; precursor to ozone.

Primary and Secondary Pollutants

  • Primary pollutant: Emitted directly from a source (e.g., CO, CO2, SO2, NO_x).
  • Secondary pollutant: Formed from primary pollutants undergoing transformation (e.g., O_3, sulfate, nitrate).

Sources of Air Pollution

  • Natural: Volcanoes, lightning, forest fires, plants.
  • Anthropogenic: Vehicles, power plants, industrial processes, waste disposal.
  • EPA sets standards via NAAQS to control harmful pollutants.

Photochemical Smog and Acid Rain

  • Photochemical smog: Complex formation involving pollutants undergoing transformations.
  • Thermal inversion: Warm air layer traps emissions.
  • Acid deposition: Nitrogen and sulfur oxides combine with atmospheric oxygen and water to form nitric and sulfuric acid.
  • Acid deposition's Effects: Lowers lake pH, decreases aquatic species, mobilizes metals, and damages structures.

Pollution Control Measures

  • Strategies: Avoid emissions, use cleaner fuels, increase efficiency, control pollutants after combustion.
  • Emission controls: Fluidized bed combustion, catalytic converters, baghouse filters, electrostatic precipitators, scrubbers.
  • Innovative measures: Reducing gasoline spillage, restricting solvents, limiting wood stoves, and managing automobile use.

Stratospheric Ozone Depletion

  • Stratospheric ozone layer: Located 45-60 km above Earth; absorbs UV radiation.
  • Formation of ozone: O2 + UV-C → O + O; O + O2 → O_3
  • Breakdown of ozone: O3 + Cl → ClO + O2; ClO + O → Cl + O_2
    • One chlorine atom can break down 100,000 ozone molecules

Indoor Air Pollution

  • Significant hazard in developing and developed countries; 4 million deaths annually.
  • Indoor pollutants: Carbon monoxide, asbestos, radon, VOCs.
  • Sick building syndrome: Caused by inadequate ventilation, chemical or biological contamination.