APES- Unit 7

Air Pollution Basics

• Types of Air Pollutants

  • Air Pollutants vs. Greenhouse Gases (GHGs): Different kinds of pollutants that affect air quality and contribute to climate change.

  • Coal Combustion: A major source of air pollutants, particularly sulfur dioxide (SO2) and nitrogen oxides (NOx).

  • Nitrogen Oxide (NOx): Includes both NO and NO2; contributes to smog and respiratory issues.

  • Lead (Pb): Historically added to gasoline, now being phased out due to health risks.

Clean Air Act (1970)

• Established by the EPA to regulate air pollutants.

  • Identified 6 criteria pollutants that must have acceptable limits.

  • CO2 is not included in these 6 pollutants despite its role as a GHG and environmental impact.

  • Primary focus: Public health and air quality (toxicity, visibility effects).

Primary vs. Secondary Pollutants

• Primary Pollutants: Emitted directly from sources, e.g., NOx, CO, VOCs.

• Secondary Pollutants: Formed through reactions in the atmosphere, e.g., tropospheric ozone formation from NOx and VOCs.

Impacts of Specific Pollutants

• Sulfur Dioxide (SO2):

  • Respiratory irritant that contributes to acid rain.

  • Forms sulfuric acid when combined with atmospheric water.

• Nitrogen Oxide (NOx):

  • Contributes to photochemical smog and respiratory problems.

• Lead (Pb):

  • Removed from gasoline in 1974; vehicles require catalytic converters to lessen NOx and CO emissions.

Photochemical Smog Formation (7.2)

• Normal Ozone (O3) Formation: Involves chemical reactions under sunlight.

• Precursor Pollutants: NOx and VOCs, emitted from vehicles and industrial processes.

  • Emission increases during daytime; smog formation peaks in warmer temperatures.

Ozone Formation Process

1. Morning traffic raises NO2 levels.

2. Sunlight breaks down NO2 into NO and free oxygen (O).

3. O combines with O2 to produce O3.

4. At night, O3 reacts with NO to revert to NO2, leading to reduced daytime levels.

Impacts + Reduction of Smog

• Environmental Effects: Reduced sunlight for photosynthesis; damage to plant stomata; respiratory issues in humans (asthma, bronchitis).

• Economic Effects: Increased healthcare costs, lost productivity, and reduced agricultural yields.

• Reduction Strategies:

  • Reduce vehicle numbers (carpooling, public transport).

  • Transition to renewable energy sources, e.g., solar and wind.

Urban Heat Island Effect

• Urban areas experience higher temperatures due to materials like asphalt absorbing heat.

• Less vegetation leads to decreased evapotranspiration, raising local air temperatures, and increasing smog.

Historical Events to Know

• Donora, PA (1948): Steel mill pollution led to 20 deaths due to temperature inversions trapping smoke.

• London Smog (1952): Cold weather combined with coal burning caused severe smog, resulting in 4,000 deaths.

Natural Sources of Air Pollution

• CO2 and Particulate Matter (PM): From natural processes such as respiration, plant emissions, wildfires, and volcanic activity.

• Respiration: All living organisms release CO2.

• Volcanic Activity: Releases SO2, PM, NOx, affecting air quality.

PM10 vs. PM2.5

• Particulate Matter (PM): Refers to airborne particles that can cause respiratory issues.

  • PM10: Larger particles (can be filtered by the nose).

  • PM2.5: Smaller particles (penetrate deep into lungs, associated with chronic diseases).

Indoor Air Pollutants

• Developing Countries: Use of biomass fuels indoors leads to high CO, PM, and VOC emissions due to poor ventilation.

• Developed Countries: Utilize commercial fuels, with major sources of indoor pollutants coming from household products and poor ventilation.

  • Lead: Historically contained in paints and pipes; poses neurological risks, especially to children.

Reducing Emissions

• Laws and Regulations:

  • Clean Air Act enables EPA to set and enforce air quality standards.

  • Pollution Credits for companies performing below emissions standards.

  • Corporate Average Fuel Economy (CAFE) establishes efficiency standards for vehicles.

Strategies to Reduce Air Pollution

• Promote increased use of public transport and renewable energy.

• Implement vapor recovery nozzles to lower VOC emissions.

• Use catalytic converters to convert harmful emissions (NOx and CO).

Acid Rain (7.9)

• Primary Pollutants: SO2 and NOx are the main contributors to acid rain.

  • Formation: SO2/NOx react with atmospheric O2 and H2O to create nitric and sulfuric acid.

Environmental Effects

• Acidification of soil and water reduces pH, affecting forest ecosystems and aquatic life.

• High H+ concentrations can displace essential nutrients from soil, harming plant and animal life.

Urban Noise Pollution (7.10)

• Sources: Construction, transportation, industrial activities, and domestic noise.

• Effects on Wildlife: Disrupted communication and migration, hearing damage in animals, and physiological stress.

• Aquatic Pollution: Marine life, especially whales, face challenges due to noise disrupting communication and migration; seismic testing also harmful.