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6. Air pollution

Atmosphere

  • Two innermost layers: Troposphere and Stratosphere.

  • Greenhouse gases: H2O, CO2, CH4, N2O.

  • Ozone layer: Concentrated in the stratosphere, protects life from UV radiation.

Air Pollution Types

  • Outdoor: Industrial smog, photochemical smog, acid deposition.

  • Indoor: Smoke, coal fire, cigarette smoke.

Air Pollutants

  • Chemicals in the atmosphere harming organisms and ecosystems.

  • Natural sources: Wind, dust, volcanic eruptions.

  • Human sources: Factories, cars.

Primary and Secondary Pollutants

  • Primary: Emitted directly into the air (e.g., Sulfur Dioxide, Nitrogen Oxides, Carbon Monoxide, VOCs, Particulates).

  • Secondary: Formed from reactions of primary pollutants (e.g., Ozone).

Key Pollutants

Sulfur Dioxide

  • Sources: Sea spray, volcanic fumes, burning fossil fuels (coal and oil).

  • Effects: Corrosive gas, causes acid rain.

Nitrogen Oxides

  • Sources: High-temperature heating, bacteria.

  • Effects: Smog, acid rain, eutrophication.

  • Nitrous oxide (N_2O) is a greenhouse gas.

Carbon Monoxide

  • Sources: Incomplete fuel combustion (cars/trucks).

  • Effects: Inhibits respiration.

  • Carbon dioxide (CO_2) contributes to global warming.

Volatile Organic Compounds (VOCs)

  • Sources: Plants, synthetic chemicals from human activities, burning hydrocarbons.

  • Role: Formation of photochemical oxidants.

Particulate Matter

  • Solid particles or liquid droplets in the atmosphere.

  • Includes: Ash, smoke, pollen, dust.

  • Effects: Reduces visibility, damages lungs (smaller than 2.5 micrometers), causes cancer (e.g., asbestos).

Ozone (O_3)

  • Stratosphere: Shields the biosphere from UV radiation.

  • Troposphere: Pollutant, photochemical oxidant, damages vegetation and buildings.

Smog

Industrial Smog

  • From burning coal (SO2, H2SO4, solid particles).

Photochemical Smog

  • Mixture of primary and secondary pollutants under UV radiation.

Indoor Pollution

  • Less developed countries (LDCs): Burning wood/coal indoors.

  • Developed countries (DCs): Chemicals from building materials (nitrogen oxide from unvented gas stoves).

Reducing Air Pollution

Outdoor

  • Reduce emissions of CO2, SO2, NO2 from power plants and vehicles.

  • Prevention: Remove sulfur from coal, improve fuel efficiency.

  • Reduction: Emission control devices.

Indoor

  • Prevention: Stricter formaldehyde standards.

  • Reduction: Fresh air vents, air circulation.

Acid Deposition

  • Sources: SO2 and NO from power plants.

  • Forms secondary pollutants: H2SO4, HNO3.

  • Types: Wet (acid rain, snow) and dry (acid particles) deposition.

Effects of Acid Deposition

  • Forest damage.

  • Building and monument damage (limestone, marble).

Reducing Acid Deposition

  • Reduce coal use.

  • Remove SO2 and NO from smokestack gases and vehicle exhaust.

Ozone Depletion

  • Caused by chemicals reducing ozone levels in the stratosphere.

  • Effects: Increased UV radiation.

Reducing UV Exposure

  • Stay out of the sun, wear sunglasses.

Effects of Ozone Depletion

  • Impacts human health, structures, food, forests, wildlife, air pollution, and climate change.