Section 15 vid 2

Air Pollution Overview

• Definition: Air pollution causes harm to living organisms and alters the climate due to harmful chemicals in the atmosphere.

• Sources:

  • Natural: Forest fires, volcanic eruptions.

  • Anthropogenic (Human-made): Majority from stationary sources (factories, power plants) and mobile sources (cars, buses).

Types of Air Pollutants

• Classification: Pollutants are classified as primary or secondary.

  • Primary Pollutants: Harmful chemicals emitted directly into the troposphere (e.g., carbon monoxide, sulfur dioxide).

  • Secondary Pollutants: Formed by reactions between primary pollutants (e.g., nitric acid, ozone).

  • UV Light: Some reactions are catalyzed by UV light, impacting formation and spread.

Classes of Air Pollutants

• Major Classes:

  • Carbon Oxides: Carbon monoxide (CO).

  • Nitrogen Oxides: Nitrogen dioxide (NO2).

  • Sulfur Oxides: Sulfur dioxide (SO2).

  • Volatile Organic Compounds (VOCs): Methane, propane, chlorofluorocarbons.

  • Suspended Particulate Matter (SPM): Includes sulfate salts, nitrates, lead, asbestos.

  • Photochemical Oxidants: Ozone, peroxacil nitrates (PANS), hydrogen peroxide, aldehydes.

  • Radioactive Substances: Radon, plutonium, strontium.

  • Hazardous Air Pollutants (HAPs): Linked to nervous system problems and cancers (e.g., benzene, formaldehyde).

Specific Air Pollutants

Carbon Monoxide (CO)

• Source: Incomplete combustion of fossil fuels; 75-95% from motor vehicles.

• Effects: Reduces blood's oxygen-carrying capacity, leading to slowed reactions and increased respiratory issues.

Nitrogen Dioxide (NO2)

• Source: Combustion of carbon-containing fuels from vehicles and industrial plants.

• Properties: Reddish-brown irritating gas, contributes to photochemical smog, and forms nitric acid linked to acid rain.

• Effects: Aggravates respiratory issues, damages ecosystems (soils, aquatic life, trees).

Sulfur Dioxide (SO2)

• Source: Combustion of fossil fuels (sulfur-containing oil and coal).

• Effects: Converts to sulfuric acid, primary component of acid deposition, causes respiratory problems, and environmental damage to biomes, trees, and materials.

Particulate Matter (PM)

• Definition: Any droplet or aerosol suspended in the atmosphere; smaller particles cause haze and health issues.

• Regulation: EPA bans emissions of particles 10 microns or less; pushes for reductions in PM 2.5 (2.5 microns or less).

• Health Effects: Can cause respiratory illnesses, especially at lower lung levels.

• Lead: Released as PM, bioaccumulates, causes serious nervous system damage.

Tropospheric Ozone (O3)

• Classification: Secondary pollutant, component of photochemical smog.

• Formation: Forms from the reaction of VOCs and nitrogen oxides in the presence of UV light.

• Characteristics: Reactive, contributes to urban air pollution, and forms through a complex chemical reaction sequence.

Chemical Reactions and Effects

• Acid Rain Formation: Nitrogen and sulfur oxides react with water to form nitric and sulfuric acids.

• Smog Formation: Primary and secondary pollutants mix, exacerbated by high temperatures in urban areas.

Summary of Key Processes

• Nitrogen Oxide Conversion: Involves reactions with VOCs and UV light leading to secondary pollutants like ozone.

• Multiple Choice Review: Understand the difference between primary and secondary pollutants; sulfur dioxide is a primary pollutant that contributes to secondary pollutants.

Conclusion

• Discussion Point: Be prepared to discuss the process of nitric oxide conversion as it relates to VOCs and their environmental impact.