Environmental Science Chapter on Air Pollutants

APES Ultimate Review Packet

• The packet includes a 9-unit video review series
• Guided notes are included
• Unit quizzes are available
• Extra math practice is provided
• Two full-length practice exams are included
• Answer keys are available for all materials

Introduction to Air Pollution (Pollutants)

• Slides are available on slidesgo.com
• Video lectures for each topic are available on YouTube.
• Daily Instagram reviews are available.
• Resources are completely free, but donations are welcome (Venmo, Square, PayPal)

Objective/EKs/Skill

• Essential knowledge about coal combustion includes that it releases air pollutants - carbon dioxide, sulfur dioxide, toxic metals, and particulates.
• Fossil fuel combustion releases nitrogen oxides which lead to ozone production, photochemical smog, and nitric acid formation (acid rain).
• Other pollutants include carbon monoxide, hydrocarbons, and particulate matter.
• Air quality can be affected by sulfur dioxide released from fossil fuel combustion, mainly diesel fuels.
• The EPA regulated lead, especially in fuels, dramatically reducing its presence in the atmosphere.
• Air pollutants can be either primary or secondary.

Air Pollution Basics

• The Clean Air Act (1970) identified 6 criteria air pollutants that the EPA monitors; these are regulated to set limits.
• Pollutants like Sulfur dioxide (SO₂), Coal combustion, (electricity), Respiration, Irritation, smog, acid precipitation, Particulate Matter (PM), FF/biomass combustion, Respiration, irritation, smog
• Nitrogen Oxides (NOx), All FF combustion (gas esp), Photochemical smog, acid precipitation
• Carbon Monoxide (CO), Incomplete combustion, Lethal to humans
• Ozone (O₃), Photochemical smog, acid precipitation, Lead
• Lead, Metal plants, waste incineration

Air Pollutants vs. Greenhouse Gases

• CO₂ is not one of the 6 criteria air pollutants in the Clean Air Act.
• CO₂ does not directly lower air quality from a human health standpoint
• CO₂ is not toxic to organisms to breath
• CO₂ is not damaging to lungs/eyes
• In APES, CO₂ is not typically included on FRQ scoring guides as an air pollutant

Coal Combustion

• Coal combustion releases more air pollutants than other fossil fuels (FFs) - ~35% of global electricity.
• It releases CO, CO₂, SO₂, NOx, toxic metals (mercury, arsenic, lead), and PM (often carries toxic metals).
• SO₂ impacts respiratory system, causing inflammation of bronchioles & lungs, worsening asthma & bronchitis
• Sulfur aerosols reduce visibility by reducing incoming sunlight.
• SO₂ forms sulfurous (grey) smog.
• SO₂ combines with water & O₂ to form sulfuric acid.

Nitrogen Oxides (NOx)

• NOx is released from combustion of anything, especially fossil fuels; it's a combination of NO and NO₂.
• It's formed when N₂ combines with O₂ during combustion.
• NO can convert to NO₂ by reacting with O₃ or through sunlight.
• NOx causes respiratory irritation and leads to tropospheric ozone (O₃) formation, resulting in photochemical smog.
• NOx combines with water and O₂ to form nitric acid.

EPA & Lead

• The EPA began phasing out lead from gasoline in 1974
• Vehicles made after 1974 were mandated with catalytic converters - to reduce NOx, CO, and hydrocarbon emissions.
• Lead is neurotoxic (harmful) to humans

Primary vs. Secondary Air Pollutants

• Primary pollutants are emitted directly from sources such as vehicles, power plants, factories, and natural sources (volcanoes, forest fires).
• Examples of primary pollutants include CO₂, VOCs, SO₂, PM, and hydrocarbons.
• Secondary pollutants are transformed from primary pollutants through chemical reactions in the presence of sunlight.
• Examples of secondary pollutants include tropospheric ozone (O₃), sulfuric acid (H₂SO₄) and sulfate (SO₄²⁻), and nitric acid (HNO₃) and nitrate (NO₃⁻).

Practice FRQ 7.1

• Temperature affects NOx production from coal combustion.
• Experiment repetition using natural gas would likely show lower NOx formation rates at all temperatures due to differences in chemical composition.

Photochemical Smog

• Photochemical smog occurs as a result of nitrogen oxides and volatile organic compounds (VOCs), driven by heat and sunlight.
• Nitrogen oxides/VOCs react to produce various pollutants
• Many environmental factors affect photochemical smog formation, including nitrogen oxide production during the day and ozone peaking in the afternoon, due to oxygen and sunlight reactions.
• Volatile Organic Compounds (VOCs) which form from sources such as formaldehyde and gasoline, are also important factors.
• Photochemical smog is prevalent in urban areas due to high motor vehicle presence.
• Reducing nitrogen oxide and VOCs reduces photochemical smog.

Factors That Increase Smog Formation

• More sunlight (high temperatures/summer afternoon) increases O₃ production.
• Temperature increase speeds up the evaporation of VOCs triggering reactions that lead to O₃ formation
• Increased vehicle traffic/high concentrations of VOC emissions/high concentration of pollutants that react with sunlight,
• Air pollution in urban area is due to higher amounts of traffic, high temperatures, and high concentrations of VOC emissions like those from factories

Impacts & Reduction of Smog

• Smog reduces sunlight, limiting photosynthesis.
• O₃ damages plant stomata
• O₃ and related chemical reactions irritate animal respiratory tracts- worsens asthma, bronchitis, COPD
• Increased health care costs are incurred to treat related diseases (asthma, bronchitis, and COPD).
• Workers miss work/productivity may decrease due to respiratory diseases.
• Crop yield is decreased due to less sunlight reaching crops and damage to plant stomata.

Practice FRQ 7.2

• NO2 concentration and ozone concentration have positive correlation, as NO2 increases so does ozone.
• Time of day impacts ozone formation, with peaks in the afternoon.

Thermal Inversion

• A thermal inversion occurs when the normal temperature gradient in the atmosphere is reversed (meaning the air temperature near the Earth's surface is cooler than the air at higher altitudes).
• Thermal inversions trap air pollutants close to the ground, often creating conditions more conducive to smog.
• This is especially true for smog and particulates (PM)

Factors Affecting Thermal Inversions

• When the temperature gradient is normal, the atmosphere is warmer at ground level, and the temperature decreases as altitude increases. Warm air rises (convection), which carries pollutants away from ground level.
• Inverting the normal temperature gradient can trap pollutants/smog at ground level, increasing pollutant concentrations (e.g., smog).

Atmospheric CO₂ & PM

• There is a variety of natural sources of particulate matter.
• Natural sources of CO2 include respiration, decomposition, and natural volcanic eruptions
• Natural sources of PM include sea salt, pollen, ash from forest fires, volcanoes, dust

Natural Sources of Air Pollutants

• Lightning strikes convert atmospheric nitrogen (N₂) to NOx
• Forest fires produce CO, PM, and NOx
• Plants emit VOCs
• Volcanoes release SO₂, PM, CO, and NOx
• Decomposition of organic matter can release CO₂ and other airborne particles (PM)

PM10 vs. PM2.5

• PM10 and PM2.5 are both particulate matter, differing in their size - PM2.5 particles (smaller) are more harmful due to ability to travel deep into human lungs.
• PM2.5 can penetrate deeper into the human respiratory tract & are associated with chronic bronchitis and lung cancer

Practice FRQ 7.4

• The control group in the experiment would be the petri dishes placed 50, 100, and 200 yards from the existing road (not under construction)
• The dependent variable is the amount of PM collected in each petri dish.
• Measurement can be determined by visually counting the PM particles using a microscope.

Indoor Air Pollutants

• Indoor air pollutants include, but are not limited to, carbon monoxide (asphyxiant), asbestos, dust, smoke, common natural sources such as radon, mold, and dust, volatile organic compounds (VOCs) from building materials.
• Some examples of indoor common substances are insulation, formaldehyde from building materials, paints, carpets, and furniture.
• Other combustion-related air pollutants include carbon monoxide, nitrogen oxides, sulfur dioxide, particulate matter, and tobacco smoke.
• Indoor air quality affected by factors includes building materials, furniture, upholstery, carpeting, and paints.
• Some common natural substances in indoor air are radon, mold, and dust..

Developing vs. Developed Countries

• Developing nations tend to use more subsistence fuels (e.g., wood).
• Combustion of these fuels can release significant amounts of CO, PM, NOx, and VOCs.
• Poor ventilation can contribute to higher indoor pollutant concentrations in developing countries.
• Developed nations typically use commercial fuels/fossil fuels like oil, coal, and natural gas for their energy.

PM & Asbestos

• Particulate matter (PM) is a common indoor pollutant.
• Examples include smoke from indoor biomass combustion, cigarettes, dust.
• Asbestos was previously used in insulation but poses a risk of lung cancer and asbestosis if disturbed.

CO (Carbon Monoxide)

• CO is produced by the incomplete combustion of fuel.
• CO is an asphyxiant that causes suffocation by binding to hemoglobin, displacing oxygen in the blood.
• CO is odorless and colorless making it hard to detect.
• CO can be detected by carbon monoxide detectors.
• High levels of CO released by malfunctioning furnace ventilation can result in a fatal risk to humans at high levels.
• Developing nations have higher rates of indoor biomass combustion for cooking and heating.

VOCs (Volatile Organic Compounds)

• VOCs are chemicals present in many home products.
• VOCs readily vaporize and can irritate eyes, lungs, and bronchioles
• Examples include adhesives, sealants, carpet glues, formaldehyde (commonly found in particle board/carpets), household cleaners, and various types of plastics and fabrics.

Radon Gas

• Radon-222 is an naturally-occurring radioactive gas, a decay product of uranium.
• Radon gas can seep into homes through cracks in foundations, ground water sources, or basements.
• Significant exposure to Radon can cause cancer.
• Testing homes for radon is important due to its harmful effects on humans.

Dust & Mold

• Dust settles naturally in homes and worsens respiratory conditions (asthma, bronchitis, COPD, emphysema).
• Mold growth occurs in dark, damp, and poorly ventilated areas (e.g., under sinks/showers, in walls).
• Mold release spores and can irritate respiratory tracts.
• Mold can be removed through cleaning and by addressing ventilation issues that lead to growth.

Lead

• Lead is a toxic metal found in paint in older homes.
• Lead in paint can be chipped or eaten by children due to its sweet taste.
• Lead can be inhaled as dust and absorbed into the blood stream and can create various health issues.
• Lead exposure is dangerous to children as they are still developing and can affect their central nervous system causing various developmental delays and brain damage.
• Lead water pipes can also release lead into drinking water.
• Lead can be removed by stripping existing paint in a home, and replacing it with lead-free paint and/or replacing lead water pipes.

Practice FRQ 7.5

• Understanding U.S. blood lead surveillance data from 1997-2015 can provide causes for trends in blood lead levels, in terms of the percentage of children.

Reduction of Air Pollutants

• Regulatory practices, conservation practices, and alternative fuels are all methods to reduce air pollutants.
• Examples of practices include using vapor recovery nozzles on gasoline pumps in order to keep fumes from escaping into the atmosphere; catalytic converters to convert pollutants in automobiles and industrial equipment into molecules that are less harmful; devices that remove or neutralize pollutants (e.g., wet and dry scrubbers).
• Using electricity sources such as solar, wind, and hydro energy reduces pollution.
• Reducing the number of vehicles on the road, walking, biking, and/or taking public transport is a way of reducing NOx emissions.
• Implementing measures such as conservation or switching to alternative fuels are important considerations.

Laws/Regulations

• The Clean Air Act gives the EPA the authority to regulate the amounts and concentration of chemicals emitted in air.
• Corporations are fined or sued if they violate EPA set limits.
• Pollution credits are like pollution permits.

Reducing Vehicle Air Pollutants

• Vapor recovery nozzles reduce hydrocarbon VOC emissions during refueling, returning vapors to storage tanks.
• Catalytic converters use metals to convert pollutants (NOx, CO, hydrocarbons) into less-harmful molecules.
• Both devices are part of the effort to address pollution control.

Reducing SO₂ & NOx

• Crushed limestone (calcium carbonate) can react with SO₂ to form calcium sulfate, effectively removing or reducing the amount of SO₂ in the atmosphere.
• Fluidized bed combustion is a method that increases combustion efficiency and improves reaction time between SO₂ and limestone.
• Dry and wet scrubbers are devices that use chemicals to remove pollutants (NOx, SO₂, VOCs) from the atmosphere's waste gases and streams using mist and water droplets to trap pollutants and prevent their release into the atmosphere’s air.

Electrostatic Precipitator & Baghouse Filter

• Power plant/factory emissions are passed through a device consisting of negatively charged electrodes, causing particles to become negatively charged, and stick to positively charged collection plates.
• Particles are collected in a collection hopper to then be taken to landfills.
• Bag filters trap particulate matter from industrial and combustion processes and dispose of it into collection hoppers.

Practice FRQ 7.6

• Obama-era CAFE standards (Corporate Average Fuel Economy) reduced NOx levels in urban areas.
• The data in Figure 1 (not included here) regarding the decline in fuel consumption following the passing of Obama-era CAFE standards supports the claim.

Acid Rain

• Acid rain happens due to nitrogen and sulfur oxides, from either natural or anthropogenic sources, which react with water and O₂.
• These reactions are a cause for acid deposition.
• NOx and SO₂ are both emitted by fossil fuels for power plants and vehicles.
• These pollutants have a significant detrimental impact on plant and animal life in particular areas.
• Regional variations in bedrock and soils influence the neutralization capacity.

Sources of NOx & SO₂

• Major sources of NO and SO₂ include coal-fired power plants, metal factories, and vehicles that burn diesel fuel
• Regulations are in place to reduce NOx and SO₂ emissions.
• The clean air act has led to a significant decrease in the emissions and the effects of acid deposition that results.

Acid Rain Effects

• Acidic rain/water leads to acidification of soils and bodies of water, corroding human-made structures.
• H+ ions displace nutrients from soil and increase the solubility of toxic metals aluminum and mercury.
• Acidic rain impacts aquatic species negatively by disrupting the optimal pH levels or range and causing a decline in population due to factors such as: aluminum toxicity, disruption of blood osmolarity, or toxicity toward the respiratory system.
• Indicator species can be surveyed in order to determine the conditions of the ecosystem in either soil, water or other related factors.

Mitigating Acid Rain

• Limestone/calcium carbonate, a natural base, can neutralize acidic soil/water, forming bicarbonate (HCO₃⁻) and releasing calcium (Ca²⁺)ions.
• Regions with limestone bedrock have natural buffering capabilities for acid rain.
• Humans can artificially introduce crushed limestone to acidic soils/water to neutralize effects
• Decreasing the primary pollutants will reduce the impact of acid rain.

Practice FRQ 7.7

• Scientists can examine how acid deposition affects crustaceans in temperate forests.
• The independent variable is the type of rainwater used for misting soil samples
• The effects of crushed limestone on the soil should be included in the study.

Noise Pollution

• Noise pollution, or environmental sound at high enough levels to cause health problems (hearing loss, physiological stress, headaches, or communication difficulties), comes from many sources like construction, transportation, industrial activities, and domestic sources such as neighbor's music or lawn mowers.
• Noise pollution can affect animal survival rates by disrupting communication, migration and mating calls.

Wildlife Effects (Aquatic)

• Noise pollution disrupts communication among various animal species leading to disruption in migration, mating, or other communication.
• Aquatic noise pollution comes from ship engines, military sonar, or seismic air blasts from oil and gas surveys.
• Noise exposure can cause physiological stress or hearing loss in numerous animal species that inhabit water.
• The seismic air blasts from oil and gas surveys can disrupt communication or cause physical trauma to aquatic animals.

Practice 7.8

• Using evidence from the NAMEPA document (not included), the effects of increased levels of aquatic noise pollution on whales and other marine species should provide support for either a negative or a positive outcome.

Test your knowledge on air pollutants and their effects with this engaging quiz based on key concepts from environmental science. Explore topics such as VOCs, NOx emissions, and the Clean Air Act. Perfect for students looking to strengthen their understanding of air quality issues.