APES Test #2 Review

Air pollution

The contamination of the atmosphere by harmful substances at concentrations that negatively affect organisms or the environment.

Primary pollutants

Pollutants released directly into the atmosphere from a source.

Examples: CO, CO₂, SO₂, NOₓ, VOCs, particulate matter.

Secondary pollutants

Pollutants formed in the atmosphere when primary pollutants chemically react.

Examples: O₃, PANs, H₂SO₄, HNO₃.

Particulate matter (PM)

Tiny solid particles or liquid droplets suspended in air.

PM₂.₅ is especially dangerous because it can penetrate deep into the lungs.

Carbon dioxide (CO₂)

A greenhouse gas produced by respiration, decomposition, combustion, deforestation, and other processes.

Carbon monoxide (CO)

A colorless, odorless gas produced primarily by incomplete combustion.

Methane (CH₄)

A powerful greenhouse gas produced by wetlands, landfills, livestock, rice agriculture, and fossil-fuel extraction.

Sulfur dioxide (SO₂)

A gas produced mainly by burning sulfur-containing fossil fuels and metal smelting.

Nitrogen oxides (NOₓ)

Gases produced mainly during high-temperature combustion in vehicles, power plants, and industry.

Ozone (O₃)

Stratospheric O₃ protects from UV; tropospheric O₃ is harmful air pollution.

CFCs

Chlorofluorocarbons, formerly used in refrigerants, aerosol propellants, and foam production.

Montreal Protocol

International agreement that phased out ozone-depleting substances such as CFCs.

Lead (Pb)

A toxic heavy metal formerly common in gasoline and paint and still released by some industrial processes.

Clean Air Act

U.S. federal law regulating air pollution and establishing standards for air quality.

Asbestos

A naturally occurring mineral fiber formerly used extensively in insulation and construction materials.

VOCs

Volatile organic compounds that easily evaporate and can react with NOₓ to form photochemical smog.

Photochemical smog

A mixture of secondary pollutants formed when NOₓ + VOCs react in sunlight.

Temperature inversion

A layer of warm air traps cooler air and pollutants near Earth's surface.

Formaldehyde

A VOC and indoor air pollutant released by some building materials, furnishings, and combustion.

Hydrocarbons

Organic compounds composed primarily of hydrogen and carbon; many are VOCs and contribute to smog.

Radon

A radioactive gas produced by uranium decay in soil and rock that can accumulate indoors.

Acid rain

Acidic precipitation caused primarily by atmospheric SO₂ and NOₓ forming sulfuric and nitric acids.

Noise pollution

Excessive or unwanted sound that negatively affects humans or wildlife.

Stationary source

A fixed source of pollution, such as a factory or power plant.

Mobile source

A moving source of pollution, especially cars, trucks, ships, and airplanes.

Vapor recovery nozzle

Captures gasoline vapors during fueling to reduce VOC emissions.

Catalytic converter

Converts harmful vehicle pollutants into less harmful substances.

Targets: CO, NOₓ, hydrocarbons/VOCs.

Scrubber

Removes pollutants, especially acidic gases such as SO₂, from industrial exhaust.

Bag filter

Uses fabric bags to physically trap particulate matter.

Electrostatic precipitator

Electrically charges particles and attracts them to oppositely charged plates.

Particulate matter: sources, environmental effects, health effects, and solutions

• Sources: combustion, vehicles, construction, agriculture, wildfires, dust

• Environment: reduced visibility; deposits on ecosystems

• Health: respiratory/cardiovascular disease, asthma, lung damage

• Solution: bag filters, ESPs, cleaner fuels, emission controls

CO₂: sources, environmental effects, health effects, and solutions

• Sources: fossil fuels, deforestation, cement production; respiration/decomposition naturally

• Environment: greenhouse effect → climate change; ocean acidification

• Health: high concentrations can cause headache, dizziness, unconsciousness

• Solution: renewables, energy efficiency, conservation, reforestation

CO: sources, environmental effects, health effects, and solutions

• Sources: incomplete combustion from vehicles, furnaces, fires

• Environment: contributes to atmospheric chemistry

• Health: binds to haemoglobin → reduces O₂ transport

• Solution: complete combustion, catalytic converters, ventilation

CH₄: sources, environmental effects, health effects, and solutions

• Sources: livestock, landfills, rice paddies, wetlands, fossil-fuel extraction

• Environment: powerful greenhouse gas; contributes to O₃ formation

• Health: primarily indirect climate effects

• Solution: capture landfill gas, improve livestock/rice management, repair gas leaks

SO₂: sources, environmental effects, health effects, and solutions

• Sources: coal/oil combustion, metal smelting, volcanoes

• Environment: acid deposition; damages forests, soils, lakes

• Health: respiratory irritation; worsens asthma

• Solution: low-sulfur fuel, scrubbers, renewable energy

SO₂ → sulfuric acid → acid rain.

NOₓ: sources, environmental effects, health effects, and solutions

• Sources: vehicles, power plants, industrial combustion

• Environment: photochemical smog, nitric acid, acid deposition, eutrophication

• Health: respiratory irritation and asthma

• Solution: catalytic converters, public transportation, cleaner energy

NOₓ → smog + nitric acid.

O₃: sources, environmental effects, health effects, and solutions

• Source: secondary pollutant formed from NOₓ + VOCs + sunlight

• Environment: damages plants and reduces crop yields

• Health: lung irritation and worsened asthma

• Solution: reduce NOₓ and VOC emissions

CFCs: sources, environmental effects, health effects, and solutions 

• Sources: refrigerants, aerosol propellants, foam

• Environment: destroy stratospheric ozone

• Health: increased UV → skin cancer and cataracts

• Solution: Montreal Protocol; safer substitutes

Lead: sources, environmental effects, health effects, and solutions 

• Sources: old gasoline/paint, batteries, mining, smelting

• Environment: toxic to ecosystems

• Health: nervous-system/brain damage, especially dangerous during development

• Solution: remove lead from products; control industrial emissions

Asbestos: sources, environmental effects, health effects, and solutions

• Sources: old insulation and construction materials

• Environment: airborne fibers can contaminate environments

• Health: asbestosis, lung cancer, mesothelioma

• Solution: professional containment/removal

VOCs: sources, environmental effects, health effects, and solutions

• Sources: paints, solvents, gasoline, cleaners

• Environment: react with NOₓ → photochemical smog

• Health: some are toxic/carcinogenic; respiratory irritation

• Solution: low-VOC products, ventilation, vapor recovery

Radon: sources, environmental effects, health effects, and solutions

• Source: uranium decay in soil/rock

• Environment: radioactive indoor pollutant

• Health: increases lung-cancer risk

• Solution: test homes; ventilation and radon mitigation

Acid rain: sources, environmental effects, health effects, and solutions

• Sources: SO₂ and NOₓ

• Environment: acidifies lakes/soil; damages forests; corrodes buildings

• Health: respiratory effects mainly from precursor pollutants

• Solution: reduce SO₂/NOₓ emissions

Photochemical smog: sources, environmental effects, health effects, and solutions

• Sources: NOₓ + VOCs + sunlight

• Environment: damages plants/crops

• Health: respiratory irritation, asthma

• Solution: reduce vehicle/industrial NOₓ and VOC emissions

Noise pollution: sources, environmental effects, health effects, and solutions

• Sources: traffic, aircraft, construction, industry

• Environment: disrupts wildlife communication and behavior

• Health: stress, sleep disruption, hearing damage

• Solution: sound barriers, zoning, quieter equipment

The complete equation for photosynthesis

6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂

The complete equation for cellular respiration

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP

How can CO₂ enter the atmosphere through natural and human activities?

Natural:

• Respiration

• Decomposition

• Volcanic eruptions

• Wildfires

• Ocean release

Human:

• Fossil-fuel combustion

• Deforestation

• Cement production

• Land-use change

Compare primary and secondary pollutants

Primary = emitted directly

Examples: CO, SO₂, NOₓ, CO₂, PM, VOCs

Secondary = formed in atmosphere

Examples: O₃, PANs, H₂SO₄, HNO₃

How does photochemical smog form?

1. Vehicles/industry release NOₓ + VOCs

2. Sunlight provides energy

3. NO₂ absorbs sunlight:
   NO₂ + sunlight → NO + O

4. Oxygen atom combines with O₂:
   O + O₂ → O₃

5. VOC reactions help produce additional oxidants such as PANs

Result: photochemical smog.

How does acid deposition occur?

SO₂ + O₂ → SO₃

SO₃ + H₂O → H₂SO₄

And nitrogen oxides form nitric acid:

NO₂ + OH → HNO₃

These acids return to Earth through wet or dry deposition.

How does limestone neutralize acid deposition?

A: Limestone contains CaCO₃, an alkaline carbonate.

CaCO₃ + acid → calcium salt + CO₂ + H₂O

The carbonate consumes H⁺, increasing pH and neutralizing acidity.

Acid + carbonate = neutralisation.

How does a thermal inversion worsen pollution?

Normally:
warm air rises, pollutants disperse

During inversion:
warm air sits above cool surface air, pollutants become trapped

This causes increased concentrations of PM, CO, NOₓ, O₃ and other pollutants near the ground.

Why can indoor pollution be worse than outdoor pollution?

Buildings can trap pollutants because of limited ventilation, allowing concentrations to build up.

Important indoor pollutants:

• Radon

• CO

• VOCs

• Formaldehyde

• Asbestos

• PM

• Tobacco smoke

• Mold

How does a catalytic converter reduce photochemical smog?

It converts harmful vehicle pollutants into less harmful substances:

CO → CO₂

Hydrocarbons → CO₂ + H₂O

NOₓ → N₂

Therefore it reduces the NOₓ and VOC/HC precursors needed to make photochemical smog.

How does a wet scrubber work?

Exhaust passes through a liquid that captures particles and/or reacts with acidic gases.

Example:

SO₂ + CaCO₃ + ½O₂ → CaSO₄ + CO₂

How does a dry scrubber work?

A dry alkaline substance reacts with acidic gases.

Ex: SO₂ + CaO → CaSO₃

How does a vapor recovery nozzle work?

Captures gasoline vapors while fuel is pumped → reduces VOC emissions.

How does an electrostatic precipitator work?

Charge particles → attract particles to plates → remove particles

Primarily removes particulate matter.

How does a bag filter work?

Exhaust passes through fabric bags that physically trap particulate matter.