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.