APES Topic 7.1: Introduction to Air Pollution

Objective

• Identify the sources and effects of different air pollutants.
• Practice explaining how modifications to experiments can change results.

Importance of Specific Air Pollutants

• In APES Free Response Questions (FRQs), specify pollutants rather than general pollution.
• Pollutants are specific chemicals, compounds, or particles with environmental and human health effects.

Clean Air Act (1970)

• Empowers the EPA to regulate six criteria air pollutants.
• Allows EPA to set acceptable air quality standards and penalize entities exceeding emissions limits.

Six Criteria Air Pollutants

1. Sulfur Dioxide (SO2)

   • Source: Coal combustion.
   • Effects: Respiratory irritant, forms acid rain.

2. Nitrogen Oxides (NOx)

   • Source: Fossil fuel combustion, especially gasoline from cars.
   • Effects: Forms tropospheric ozone, photochemical smog, precursor to acid precipitation.

3. Carbon Monoxide (CO)

   • Source: Incomplete combustion of fossil fuels and biomass.
   • Effects: Lethal to humans, displaces oxygen in bloodstream.

4. Lead

   • Source: Metal smelting, waste incineration.
   • Effects: Neurotoxicant, damages nervous systems of humans and animals.

5. Ozone (O3)

   • Specifically tropospheric ozone.
   • Effects: Smog precursor, respiratory irritant.

6. Particulate Matter

   • Sources: Combustion, construction, forest fires.
   • Effects: Respiratory tract irritant, worsens asthma and bronchitis, contributes to smog.

Carbon Dioxide (CO2)

• Not initially a criteria air pollutant in the Clean Air Act.
• Supreme Court (2007): EPA can regulate CO2 due to climate change threat.
• CO2 does not directly lower air quality but contributes to global warming.
• Not typically considered an air pollutant in APES FRQs.

Coal Combustion

• Releases more pollutants per unit mass than other fossil fuels.
• Major source of global electricity generation.
• Pollutants released: CO, CO2, SO2, NOx, toxic metals (mercury, arsenic, lead).

Specific Impacts of SO2

• Respiratory irritant, impacts eyes, lungs, bronchioles.
• Forms sulfur aerosols, contributing to smog.
• Leads to acid rain (sulfuric acid, sulfate).

Specific Impacts of NOx

• Released by combustion due to atmospheric nitrogen.
• Contributes to ozone formation, acid rain (nitric acid, nitrate).

EPA's Actions on Lead

• Lead phased out from gasoline starting in 1974.
• Catalytic converters required from 1975.
• Lead concentrations in the atmosphere have significantly declined.

Primary vs. Secondary Air Pollutants

• Primary Pollutants: Directly emitted (e.g., from vehicles, power plants).
• Secondary Pollutants: Formed by transformation of primary pollutants (e.g., ozone, sulfuric acid).

Practice FRQ 7.1

• Experiment on NOx production at different temperatures during coal combustion.
• Question: How would results change if using natural gas instead of coal?