Unit 7: Air Pollution

Intro to Air Pollution

• Primary Pollutants:
  • Emitted directly from a source (e.g., $NO_2$ from a car).
• Secondary Pollutants:
  • Formed in the atmosphere through chemical reactions (e.g., $O<em>3$ from $NO</em>2$).

Key Pollutants

• Need to know both abbreviations and names.
• Many air pollutants come from burning fossil fuels.
  • Fossil fuels are a running trend through air pollution.

SOX (Sulfur Oxides)

• Mainly from power plant coal burning.
• Example: Sulfur dioxide ($SO_2$).

NOX (Nitrogen Oxides)

• From coal burning power plants and cars.
• Example: Nitrogen dioxide ($NO_2$).

Carbon Dioxide ($CO_2$)

• Naturally occurring: respiration, decomposition, volcanoes.
• Contributes to climate change as a greenhouse gas.

Toxic Metals

• Released through combustion of coal.
• Examples: Lead (Pb) and mercury (Hg), both toxic to the nervous system.

Particulate Matter (PM)

• From combustion: coal, cigarette smoke, wood fires (forest fires).

Clean Air Act (CAA)

• A United States federal law.
• Regulates six major air pollutants.
• Regulates lead in gasoline.

Photochemical Smog (Smog)

• Forms when NOx chemicals react with sunlight and VOCs.
• NOx forms early in the day (rush hour traffic).
• NOx + Sunlight -> Ozone ($O_3$).
• Smog forms more in urban areas (traffic).
• VOCs (Volatile Organic Compounds) are present.
• VOCs: gasoline, formaldehyde, varnishes, paint, nail polish, perfume, tree sap.
• VOCs easily evaporate at room temperature and have strong smells.
• Environment (mountains, valleys) affects smog formation.

Reaction for Photochemical Smog

• $NO_2$ (nitrogen dioxide) emitted by cars reacts with sunlight.
• $NO_2$ + Sunlight -> $NO$ + $O$ (oxygen radical).
• $O$ + $O<em>2$ (oxygen gas) -> $O</em>3$ (ozone).

Normal Ozone Formation

• $O_3$ reacts with $NO$ (nitric oxide) at night.
• $O<em>3$ + $NO$ -> $O</em>2$ + $NO_2$.
• Breaks back down once the sun is down.

Smog Formation with VOCs

• VOCs bind with $NO$.
• $NO$ + VOCs -> Photochemical Oxidants.
• $O_3$ is not broken down and floats around in the atmosphere.
• Photochemical Oxidants + $O_3$ -> Smog.

Thermal Inversions

• Normal Conditions: Warmer air near the surface, colder air as you go out towards space.
• Thermal Inversion: Warm air traps cold air close to the earth's surface.
• Pollution (smog, particulates) gets trapped beneath the warm air.
• Example: Great Smog of London, 1900s - 12,000 deaths due to trapped pollution from coal burning.

Acid Deposition

• Acid rain or dry deposition (particulate acid).
• Due to nitrogen oxides (NOX) and sulfur oxides (SOX).
• SOX and NOX mix with water vapor.
• Secondary Pollutants: Nitric acid and sulfuric acid.
• Acid rain may form in one location but affect other areas.

Effects of Acid Deposition

• Irritating to skin, lungs, eyes.
• Acidification of soils and water bodies.
• Damages forests and buildings (marble statuary).
• Leaches toxic metals from the ground (e.g., mercury).
• Limestone in soils can neutralize acid (alkaline/basic end of pH scale).

Indoor Air Pollutants

• From natural and man-made sources, and combustion.

Natural Sources

• Radon (radioactive material).
• Mold.
• Dust.
• Particulates: asbestos.

Man-Made Sources

• Insulation.
• Volatile Organic Compounds (VOCs) from furniture, paneling, carpets.
• Formaldehyde.
• Lead in paint (old homes).
• VOCs: Lung and eye irritation.

Combustion

• Wood in fireplace: Carbon monoxide (CO), NOx, SOx, particulate matter.
• Tobacco and cigarettes.
• Carbon monoxide is an asphyxiant.

Radon

• From uranium decaying in the ground.
• Uranium -> Radon-222 (gas).
• Leaks into home foundations, especially basements.
• Damages lungs, second leading cause of lung cancer in the US.

Noise Pollution

• High levels cause hearing loss and physiological stress.

Sources

• Urban transportation, construction, domestic activity (loud stereos), industrial activity.

Effects on Humans

• Anxiety, poor concentration, loss of sleep, stress, effect on physical health.

Effects on Animals

• Altered behavior.
• Inability to communicate.
• Difficulty finding a mate.
• Echolocation issues.
• Ocean animals affected by boat motor noise, sonar, offshore drilling.

Methods for Reduction of Air Pollutants

• Catalytic converters: Reduce NOx chemicals and carbon monoxide.
• Vapor recovery nozzles: Capture fumes at gasoline pumps.
• Scrubbers: Remove particulates with water (coal fired power plants).
• Electrostatic precipitators: Remove particulates with static (power plant smokestacks).
• Reduce fossil fuel use.
• Regulatory methods: Clean Air Act (CAA).