Copy of Unit 7 Smedes APES Note Slides (22-23)

Air Pollution Basics

• Coal Combustion:

  • Main source of electricity; can cause respiratory irritation, smog, and acid precipitation.

  • Releases various pollutants:

    • SO2 (Sulfur dioxide)

    • NOx (Nitrogen Oxides - NO & NO2)

    • CO (Carbon Monoxide)

    • Particulate Matter (PM)

    • Tropospheric Ozone (O3)

    • Pb (Lead)

• Combustion Types:

  • Fossil Fuels (FF): Generous emissions, particularly NOx.

  • Biomass Combustion: Also contributes to respiratory irritation and smog.

  • Pollutants can arise from incomplete combustion, such as photochemical smog.

• Criteria Air Pollutants:

  • Clean Air Act (1970) identified six major pollutants that the EPA monitors and regulates.

Air Pollutants vs. Greenhouse Gasses

• CO2:

  • Not categorized as a criteria pollutant under the Clean Air Act as it does not directly affect human health or air quality.

  • Regulated as a greenhouse gas since a Supreme Court ruling in 2007.

  • Focus should be on criteria air pollutants like SO2, NOx, O3, and PM in exams.

Coal Combustion

• Most polluting fossil fuel; approximately 35% of global electricity comes from coal.

• Releases:

  • CO

  • CO2

  • SO2

  • NOx

  • Toxic metals (mercury, arsenic, lead)

  • PM, which often contains these toxic metals.

• Impacts of SO2:

  • Acts as a respiratory irritant, worsening conditions like asthma.

  • Forms sulfurous smog and can contribute to acid precipitation.

Nitrogen Oxides (NOx)

• Sources: Emitted from the combustion of fossil fuels and biomass.

  • NO is formed when nitrogen and oxygen combine during combustion; NO2 forms from reactions involving O3.

• Environmental and Health Impacts:

  • Acts as a respiratory irritant.

  • Contributes to the formation of tropospheric ozone and photochemical smog.

  • Forms nitric acid when combined with water and oxygen, leading to acid rain.

EPA & Lead

• Prior to the Clean Air Act, lead was extensively used in gasoline.

• EPA initiated a phase-out of lead in fuel starting in 1974.

  • Catalytic converters required in vehicles to reduce NOx, CO, and hydrocarbons.

  • Lead is a known neurotoxin and can damage human nervous systems.

Primary vs. Secondary Air Pollutants

• Primary Pollutants:

  • Directly emitted from sources: vehicles, power plants, factories, and natural events like fires.

  • Examples: NOx, CO, SO2, VOCs, PM.

• Secondary Pollutants:

  • Formed from reactions in the atmosphere caused by primary pollutants.

  • Often occur during daylight due to photochemical reactions.

  • Examples: Tropospheric Ozone (O3), sulfuric and nitric acids.

Photochemical Smog Formation

• Precursors to Smog:

  • NO2 is broken down by sunlight into NO + O.

  • Free O then combines with O2 to form ozone (O3).

• Conditions for Formation:

  • Presence of VOCs which combine with NO to create photochemical oxidants.

  • Higher temperatures increase evaporation of VOCs, facilitating smog.

• Major emissions sources: gasoline, cleaning products, and other hydrocarbons.

Impacts of Smog

• Environmental Effects:

  • Reduces sunlight availability, impacting photosynthesis.

• Human Impacts:

  • Respiratory issues like asthma and bronchitis exacerbated.

  • Economic consequences due to healthcare costs for pollution-related ailments and reduced agricultural yields.

Urban Heat Island Effect

• Urban areas experience higher temperatures due to:

  • Lower surface albedo (dark surfaces absorb heat).

  • Reduced vegetation leading to less evapotranspiration.

Thermal Inversion Effects

• Normal Conditions: Warm air rises, carrying pollutants higher into the atmosphere.

• Thermal Inversion: A layer of warm air traps cooler air near the surface, preventing pollutant dispersion.

• Consequences: Higher concentrations of pollutants lead to health problems and reduced visibility.

Natural Sources of Pollutants

• Examples: Lightning strikes, forest fires, and volcanic activity release NOx, CO, PM, and VOCs which can contribute to pollution.

PM and Health Impacts

• PM10 and PM2.5: Classified by size, with PM2.5 being more harmful due to deeper lung penetration.

  • Sources include combustion processes and can aggravate respiratory diseases.

Global Air Pollution Patterns

• Developed vs. Developing Countries:

  • Developing nations rely on biomass fuels leading to high indoor pollution levels.

  • Developed nations have regulatory measures in place, but still contend with pollution from industrial activities.

Indoor Air Pollutants

• Common sources include VOCs from household products, radon from soil, and mold from damp areas.

• Lead: Previously common in paint, now regulated due to its neurotoxic effects.

Pollution Reduction Measures

• General Practices:

  • Use public transport, conserve energy, and shift to renewable energy sources.

• Laws and Regulations:

  • Clean Air Act outlines regulations and standards for air quality.

• Emission Control Technologies:

  • Utilization of scrubbers, electrostatic precipitators, and catalysts in vehicles to control emissions.