AP Environmental Science Unit 7 Review: Atmospheric Pollution

7–10% of AP multiple choice
8 topics
AP exam review verified for 2027

Unit 7 is about where air pollutants come from, what they do to the atmosphere and to living things, and how human society can reduce them through technology, regulation, and behavior change.

Fiveable's AP Environmental Science Unit 7 review covers 8 topics, with guided practice questions for the unit.

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AP Environmental Science unit 7 topics

7.1

Introduction to Air Pollution

Identifies pollutants released by coal combustion and fossil fuel burning, distinguishes primary from secondary pollutants, and introduces the Clean Air Act and EPA regulation of lead and other emissions.

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7.2

Photochemical Smog

Explains how NOx and VOCs react with heat and sunlight to form ground-level ozone and smog, why ozone peaks on summer afternoons, and how catalytic converters and vapor recovery nozzles reduce smog precursors.

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7.3

Thermal Inversion

Describes how a warm air layer above cooler surface air reverses the normal temperature gradient, trapping smog and particulates near the ground and worsening air quality.

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7.4

Atmospheric CO2 and Particulates

Covers natural sources of atmospheric CO2 (respiration, decomposition, volcanic eruptions) and natural particulate matter (volcanic ash, dust, sea salt, wildfire smoke, pollen).

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7.5

Indoor Air Pollutants

Identifies indoor pollutants by source category: natural (radon, mold, dust), human-made (VOCs, formaldehyde, asbestos, lead paint), and combustion (CO, NOx, tobacco smoke). Radon-222 is the second leading cause of lung cancer in the U.S.

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7.6

Reduction of Air Pollutants

Covers pollution-control devices including catalytic converters, vapor recovery nozzles, wet and dry scrubbers, and electrostatic precipitators, plus regulatory and conservation approaches.

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7.7

Acid Rain

Traces acid deposition from SO2 and NOx emissions through atmospheric conversion to sulfuric and nitric acid, and explains effects on soils, lakes, and structures, including how limestone bedrock buffers acid inputs.

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7.8

Noise Pollution

Defines noise pollution in terms of decibel levels and physiological harm, identifies urban sources, and describes effects on human hearing and stress as well as wildlife communication, hunting, and migration.

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Practice AP Environmental Science unit 7 questions

Try AP-style questions on unit 7, then use the review notes below for anything you miss.

Example stimulus-based MCQs

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experimental_data

Stimulus-based practice question

Urban traffic noise may interfere with robin mating calls. Ecologists recorded robin songs at three sites with different mean traffic noise levels and compared the minimum song frequency at each site.

Location Type	Mean Traffic Noise (dB)	Mean Minimum Song Frequency (kHz)
Rural Forest	45	1.8 $\pm 0.2$
Suburban Park	60	2.4 $\pm 0.3$
Urban Center	75	3.2 $\pm 0.2$

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Question

Which conclusion about the hypothesis is best supported by the data?

The data refute the hypothesis because robins in urban areas had lower song frequencies than robins in rural areas.

The data are inconclusive because song frequency showed no relationship to traffic noise across the three sites.

The data support the hypothesis because robins at noisier sites had higher minimum song frequencies.

The data prove the hypothesis because traffic noise causes permanent hearing damage in robins.

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Stimulus-based practice question

Historical marble statues in a city showed increasing annual surface mass loss $(\mathrm{g/m^2})$ over a 30-year period. A scientist compared the statues' mass loss with the city's average annual atmospheric sulfur dioxide $(\mathrm{SO_2})$ concentration and claimed that anthropogenic $\mathrm{SO_2}$ emissions are the primary cause of the accelerated weathering.

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Question

Which assumption most directly connects the evidence to the claim?

The marble used for the statues is especially susceptible to natural physical weathering.

Most atmospheric $\mathrm{SO_2}$ in the city comes from natural sources such as volcanic vents.

Sulfuric acid formed from atmospheric $\mathrm{SO_2}$ reacts with calcium carbonate in marble, increasing chemical weathering.

Statue mass loss is mainly proportional to physical erosion caused by rainfall.

Example FRQs

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FRQ

Urban air pollution, ozone formation, atmospheric conditions

1. Air pollution is a major environmental concern in urban areas. A city located in a valley experiences frequent episodes of poor air quality, particularly during certain weather conditions. Scientists monitored air pollutant concentrations at various times of day and under different atmospheric conditions to understand the factors contributing to pollution episodes.

Figure 1. Ground-Level Ozone Concentration (ppb) Versus Time of Day (hours), with EPA 70 ppb Standard

Based on the data in Figure 1, identify the ground-level ozone concentration at 10 AM.

Based on the data in Figure 1, describe the trend in ground-level ozone concentration between 8 AM and 4 PM.

Identify the primary source of nitrogen oxides ( $NO_x$ ) in urban areas that contributes to photochemical smog formation.

Describe the process by which nitrogen oxides and volatile organic compounds react to form ground-level ozone.

Figure 2. Vertical Temperature Profiles Under Normal Conditions vs. Thermal Inversion (with Pollutant Trapping)

Based on the diagrams in Figure 2, describe one way that atmospheric conditions during a thermal inversion differ from normal atmospheric conditions.

Indoor Air Pollutant Concentrations in Two Building Types

Building Type	Radon (pCi/L)	Carbon Monoxide (ppm)	Formaldehyde (ppb)	Particulate Matter $PM_{2.5}$ ( $μg/m^3$ )
Newly Constructed Home	1.2	2.5	45	18
Older Home (built 1975)	5.8	8.2	12	15

Indoor air quality is an important environmental health concern. A group of students investigated the concentrations of various indoor air pollutants in two different building types: a newly constructed home with modern insulation and ventilation systems, and an older home built in 1975. The students used calibrated air quality monitors to measure pollutant concentrations in the main living areas of each building over a 24-hour period. The data from their investigation are shown in the table below.

Identify the dependent variable in the students' investigation.

ii.

Based on the data in the table, identify which building type had a higher radon concentration.

Explain why the formaldehyde concentration is higher in the newly constructed home compared to the older home.

ii.

Explain one potential health effect of long-term exposure to elevated radon concentrations in the older home.

Describe one effect of acid deposition on aquatic ecosystems such as lakes and streams. Acid deposition is another air pollution problem that affects ecosystems. Sulfur dioxide ( $SO_2$ ) and nitrogen oxides ( $NO_x$ ) released from industrial sources and vehicle emissions can be converted to sulfuric acid and nitric acid in the atmosphere.

Explain how catalytic converters in vehicles help reduce the formation of photochemical smog in urban areas.

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FRQ

Air pollution, thermal inversions, acid deposition effects

3. A coastal city with a population of 850,000 people is experiencing severe air quality problems due to emissions from a coal-fired power plant and a nearby cement manufacturing facility. The city is located in a valley surrounded by mountains, which contributes to frequent thermal inversion events during winter months. Local health officials have documented increased respiratory illnesses, and environmental monitoring stations have recorded elevated levels of sulfur dioxide (SO₂), nitrogen oxides (NOₓ), and particulate matter (PM₂.₅). Additionally, residents in poorly ventilated homes near the industrial area have reported health concerns related to indoor air quality.

Identify one natural source of particulate matter in the atmosphere, other than volcanic eruptions.

Describe how a thermal inversion contributes to increased air pollution concentrations in the city.

Explain how sulfur dioxide emissions from the coal-fired power plant can lead to acid deposition and describe one environmental effect of acid deposition on aquatic ecosystems.

Calculate the percent reduction in sulfur dioxide emissions achieved by the wet scrubbers. Show your work. The coal-fired power plant currently emits 145 metric tons of sulfur dioxide per day. After installing wet scrubbers (flue-gas desulfurization technology), the plant reduces its SO₂ emissions to 22 metric tons per day.

Calculate the expected nitrogen dioxide concentration in parts per billion (ppb) after the traffic reduction measures are implemented. Show your work. Environmental monitoring data shows that nitrogen dioxide (NO₂) concentrations in the city average 65 parts per billion (ppb) during morning rush hour. The city implements an expanded public transit system and carpooling incentives, which reduces vehicle traffic by 35%. Studies show that NO₂ concentrations are directly proportional to vehicle traffic volume.

Identify one indoor air pollutant commonly found in homes with poor ventilation and describe one human health effect associated with chronic exposure to this pollutant.

Calculate the total mass of particulate matter, in kilograms, that would be released into the atmosphere in one year after the electrostatic precipitators are installed. Show your work. The cement manufacturing facility produces particulate matter emissions at a rate of 2.8 kilograms per hour when operating at full capacity. The facility operates 16 hours per day, 6 days per week. The city requires the facility to install electrostatic precipitators that capture 98.5% of particulate emissions. There are 52 weeks in a year.

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FRQ

Air pollution, temperature inversion, photochemical smog

2. A major metropolitan area experiences frequent air quality problems, particularly during summer months. The city is located in a valley surrounded by mountains and has a population of 3 million people. The primary sources of air pollution include vehicle emissions, industrial facilities, and power plants. Local health officials have documented increased respiratory illness rates during pollution episodes.

Figure 1. Atmospheric Temperature Profile Under Normal and Inversion Conditions

Identify the atmospheric condition shown in the right diagram of Figure 1 that traps air pollutants near ground level.

Figure 2. Daily Variation in Air Pollutant Concentrations

Based on the information in Figure 2, identify the secondary air pollutant that forms from chemical reactions involving primary pollutants and sunlight.

Based on the information in Figure 2, identify the time of day when ozone concentrations reach their maximum level.

Explain why ozone concentrations are highest in the afternoon rather than during morning rush hour when NOx emissions are elevated.

Describe one negative effect of exposure to elevated ozone levels on human respiratory health.

Propose a realistic solution the city government could implement to reduce NOx emissions from the transportation sector.

Describe one way that catalytic converters in vehicles reduce air pollution at the source.

Justify the solution proposed in part F by providing an additional environmental or public health advantage, other than the reduction of NOx emissions.

Describe one way that sulfur dioxide (SO2) and nitrogen oxides (NOx) from the city's industrial facilities contribute to acid deposition in downwind regions.

Describe one harmful effect of acid deposition on aquatic ecosystems in lakes located downwind from the metropolitan area.

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AP Environmental Science unit 7 practice test

A timed, AP-style test built only from unit 7 questions — multiple choice plus free response, scored with AI feedback. Use the standard format or build your own.

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Unit 7 review notes

7.1

Sources and Types of Air Pollutants

Coal combustion is the most pollutant-dense energy source, releasing SO2, CO2, toxic metals like mercury and lead, and particulate matter. Vehicle combustion adds NOx, CO, hydrocarbons, and VOCs. The Clean Air Act authorized the EPA to regulate these emissions, and phasing out leaded gasoline dramatically reduced atmospheric lead. The key conceptual split is primary vs. secondary pollutants.

Primary pollutant: Emitted directly into the atmosphere from a source, such as SO2 from coal combustion or CO from incomplete fuel burning.
Secondary pollutant: Forms in the atmosphere through reactions involving primary pollutants, such as tropospheric ozone or sulfuric acid.
NOx from combustion: Nitrogen oxides released at high combustion temperatures; precursors to ozone, photochemical smog, and nitric acid in acid rain.
Clean Air Act / EPA: Federal law that empowers the EPA to set National Ambient Air Quality Standards and regulate pollutants including SO2, NOx, particulates, CO, ozone, and lead.
Particulate matter: Tiny solid or liquid particles (PM2.5 and PM10) from combustion and dust; linked to respiratory disease and reduced visibility.

Can you list three pollutants released by coal combustion and classify each as primary or secondary?

Pollutant	Source	Primary or Secondary	Key Effect
SO2	Coal combustion, diesel	Primary	Acid rain, respiratory irritation
NOx	Vehicles, power plants	Primary	Smog precursor, acid rain
Tropospheric ozone	NOx + VOCs + sunlight	Secondary	Photochemical smog, lung damage
CO	Incomplete combustion	Primary	Asphyxiant, binds hemoglobin
Particulate matter	Combustion, dust	Primary	Respiratory disease, reduced visibility

7.2

Photochemical Smog

Photochemical smog is a secondary pollution event driven by the reaction: NOx + VOCs + heat + sunlight produces ground-level ozone and other oxidants including peroxyacyl nitrates (PANs). NOx concentrations peak in the morning rush; ozone peaks in the afternoon when sunlight is strongest. Urban geography, traffic density, summer heat, and stagnant air all amplify smog formation. Reductions come from catalytic converters, vapor recovery nozzles, reformulated fuels, and public transit expansion.

Photochemical smog formula: NOx + VOCs + heat + sunlight produces ground-level ozone and secondary oxidants; not a balanced chemical equation but the conceptual shortcut used on the exam.
VOCs: Volatile organic compounds that evaporate at room temperature from gasoline, solvents, and even trees; react with NOx to form smog.
Diurnal ozone pattern: NOx peaks in the morning; ozone builds through the day and peaks in the afternoon when UV radiation is highest.
PANs: Peroxyacyl nitrates, secondary smog components that cause eye irritation and are toxic to plants.
Smog reduction strategies: Catalytic converters, vapor recovery nozzles, low-VOC fuels, and public transportation reduce the NOx and VOC inputs that drive smog chemistry.

Why does ground-level ozone peak in the afternoon rather than in the morning when NOx emissions are highest?

7.3

Thermal Inversion

Normally, air temperature decreases with altitude, allowing warm surface air to rise and disperse pollutants. During a thermal inversion, a layer of warm air sits above cooler surface air, acting as a lid that prevents vertical mixing. Smog, particulates, and other pollutants accumulate near the ground where people breathe. Valleys and coastal basins surrounded by mountains are especially prone to inversions.

Normal lapse rate: Temperature decreases with altitude, so warm surface air rises and carries pollutants upward and away.
Thermal inversion: Warm air layer above cooler surface air reverses the normal gradient, trapping pollutants close to the ground.
Pollutant trapping: Smog and particulates cannot disperse vertically during an inversion, raising ground-level concentrations and health risks.

Describe how a thermal inversion changes the normal atmospheric temperature gradient and explain the pollution consequence.

Condition	Temperature gradient	Pollutant behavior
Normal atmosphere	Decreases with altitude	Warm surface air rises, dispersing pollutants
Thermal inversion	Increases with altitude (warm layer above)	Cool surface air trapped; pollutants accumulate near ground

7.4

Natural Sources of CO2 and Particulates

Not all atmospheric CO2 and particulate matter comes from human activity. Natural CO2 sources include cellular respiration by all organisms, decomposition of organic matter, and volcanic eruptions. Natural particulate sources include volcanic ash, windblown mineral dust, sea salt aerosols, wildfire smoke, pollen, and fungal spores. Recognizing these natural baselines is important for distinguishing background levels from anthropogenic additions.

Natural CO2 sources: Respiration, decomposition of organic matter, and volcanic degassing all release CO2 into the atmosphere without human involvement.
Natural particulate sources: Volcanic ash, Saharan dust, sea salt spray, wildfire smoke, pollen, and fungal spores are major natural contributors to atmospheric particulate matter.
Anthropogenic vs. natural baseline: Human activities add CO2 and particulates on top of natural fluxes; the exam may ask you to distinguish the two categories.

Name two natural sources of CO2 and two natural sources of particulate matter.

7.5

Indoor Air Pollutants

Indoor air can be more polluted than outdoor air. Pollutants fall into three source categories: natural (radon, mold, dust), human-made materials (VOCs and formaldehyde from furniture and carpets, asbestos from insulation, lead from paint), and combustion (carbon monoxide, NOx, SO2, particulates, tobacco smoke). Radon-222, produced by uranium decay in soil and rock, infiltrates homes through basements and foundation cracks and is the second leading cause of lung cancer in the United States.

Carbon monoxide (asphyxiant): Colorless, odorless gas from incomplete combustion that binds hemoglobin and reduces oxygen delivery; detected with CO detectors.
Radon-222: Radioactive gas from uranium decay in soil; enters homes through basements and cracks; second leading cause of lung cancer in the U.S.
Asbestos: Fibrous mineral used in insulation; when disturbed, releases inhalable fibers linked to mesothelioma and lung disease.
Formaldehyde: VOC off-gassed from pressed wood furniture, carpets, and building materials; irritates eyes and respiratory tract.
Source categories: Natural (radon, mold, dust), human-made (VOCs, formaldehyde, lead paint, asbestos), and combustion (CO, NOx, tobacco smoke, particulates).

Classify radon, formaldehyde, and carbon monoxide by their indoor source category and describe one health effect of each.

Pollutant	Source category	Health effect
Radon-222	Natural (uranium decay)	Lung cancer
Carbon monoxide	Combustion	Asphyxiation, oxygen deprivation
Formaldehyde	Human-made (building materials)	Respiratory irritation
Asbestos	Human-made (insulation)	Mesothelioma, lung disease
Mold	Natural	Allergic reactions, respiratory problems

7.6

Reduction of Air Pollutants

Air pollution reduction strategies fall into three categories: regulatory practices (Clean Air Act standards, EPA enforcement), conservation practices (driving less, energy efficiency), and alternative fuels (natural gas, renewables). Device-level controls are the most testable: catalytic converters, vapor recovery nozzles, wet and dry scrubbers, and electrostatic precipitators each target specific pollutants at specific emission points.

Catalytic converter: Converts CO, NOx, and hydrocarbons in vehicle exhaust into CO2, N2, O2, and H2O through chemical reactions over a catalyst.
Vapor recovery nozzle: Captures gasoline fumes at the pump nozzle, preventing VOC emissions during vehicle refueling.
Wet/dry scrubbers: Industrial devices that remove SO2 and particulates from exhaust streams using liquid spray (wet) or dry sorbent injection (dry).
Electrostatic precipitator: Uses high-voltage electric charge to attract and collect particulate matter from industrial exhaust before it exits the stack.
Regulatory approach: The Clean Air Act and EPA standards set enforceable emission limits; compliance drives adoption of control technologies.

Match each device (catalytic converter, scrubber, electrostatic precipitator, vapor recovery nozzle) to the pollutant it primarily targets.

Device	Pollutant targeted	Where used
Catalytic converter	CO, NOx, hydrocarbons	Vehicle exhaust
Vapor recovery nozzle	VOCs (gasoline fumes)	Gas station pump
Wet/dry scrubber	SO2, particulates	Industrial/power plant exhaust
Electrostatic precipitator	Particulate matter	Coal plant exhaust stack

7.7

Acid Rain

Acid deposition occurs when SO2 and NOx from coal-burning power plants and motor vehicles react with water vapor in the atmosphere to form sulfuric acid (H2SO4) and nitric acid (HNO3). These acids fall as wet deposition (rain, snow) or dry deposition (particles, gases). Communities downwind of major emission sources receive the highest acid loads. Effects include soil acidification, lake acidification and fish kills, and corrosion of marble and limestone structures. Limestone bedrock can buffer acid inputs by neutralizing acidity with calcium carbonate.

Acid deposition sources: SO2 from coal plants and NOx from vehicles and power plants are the primary precursors; both convert to acids in the atmosphere.
Wet vs. dry deposition: Wet deposition is acid dissolved in precipitation; dry deposition is acidic gases and particles settling directly onto surfaces.
Soil and lake acidification: Lower pH reduces plant nutrient availability, mobilizes toxic aluminum ions, and kills acid-sensitive aquatic species.
Limestone buffering: Calcium carbonate in limestone bedrock neutralizes incoming acid, so regions with limestone geology experience less ecological damage.
Downwind effect: Acid deposition affects communities far from the emission source because SO2 and NOx travel long distances before converting to acids.

Explain why a lake on granite bedrock is more vulnerable to acid rain damage than a lake on limestone bedrock.

7.8

Noise Pollution

Noise pollution is sound at levels high enough to cause physiological stress and hearing loss. Urban sources include transportation (road traffic, aircraft, rail), construction (pile driving, jackhammers), and industrial and domestic activity. Effects on humans include hearing loss, stress, and sleep disruption. Effects on wildlife include stress responses, masking of communication and hunting sounds, hearing damage, and altered migratory routes. Noise pollution is measured in decibels (dB).

Noise pollution definition: Sound at levels sufficient to cause physiological stress or hearing loss in humans or animals.
Urban sources: Transportation (vehicles, aircraft, trains), construction equipment, and industrial and domestic activity are the primary urban noise sources.
Human health effects: Chronic exposure causes permanent hearing loss, elevated stress hormones, cardiovascular strain, and sleep disruption.
Wildlife effects: Noise masks animal communication and hunting sounds, causes stress, damages hearing, and can redirect migratory routes.
Sonar interference: Artificial sound waves from shipping or military operations disrupt echolocation and navigation in marine mammals.

Identify two urban noise sources and describe one effect on human health and one effect on wildlife.

Key terms

Term	Definition
Primary Pollutants	Substances emitted directly into the atmosphere from a source, such as SO2 from coal combustion or CO from incomplete fuel burning.
Secondary Pollutants	Pollutants formed in the atmosphere through chemical reactions involving primary pollutants, such as tropospheric ozone formed from NOx and VOCs in sunlight.
Nitrogen Oxides (NOx)	Reactive gases released by high-temperature combustion in vehicles and power plants; precursors to photochemical smog, tropospheric ozone, and nitric acid in acid rain.
Volatile organic compounds (VOCs)	Chemicals that evaporate at room temperature from gasoline, solvents, and some plants; react with NOx and sunlight to produce photochemical smog.
Tropospheric ozone	Ground-level ozone formed when NOx and VOCs react with heat and sunlight; a major component of photochemical smog and a respiratory irritant.
Particulate Matter	Tiny solid or liquid particles suspended in the air from combustion, dust, and natural sources; linked to respiratory disease and reduced visibility.
Sulfur Dioxide	Gas released primarily from coal combustion and diesel burning; a primary pollutant and the main precursor to sulfuric acid in acid deposition.
Clean Air Act	U.S. federal law that authorizes the EPA to set and enforce National Ambient Air Quality Standards for pollutants including SO2, NOx, CO, ozone, particulates, and lead.
radon	Naturally occurring radioactive gas produced by uranium decay in soil and rock; infiltrates homes through basements and cracks and is the second leading cause of lung cancer in the U.S.
Carbon Monoxide	Colorless, odorless gas from incomplete combustion; classified as an asphyxiant because it binds hemoglobin and reduces the blood's ability to carry oxygen.
Scrubbers	Industrial air pollution control devices that remove SO2 and particulates from exhaust streams using liquid spray (wet scrubbers) or dry sorbent injection (dry scrubbers).
acidification of soils	Process by which acid deposition lowers soil pH, reducing plant nutrient availability, mobilizing toxic aluminum ions, and degrading ecosystem function.
Formaldehyde	VOC off-gassed from pressed wood furniture, carpets, and building materials; a common human-made indoor air pollutant that irritates the eyes and respiratory system.
Peroxyacyl Nitrates (PANs)	Secondary smog pollutants formed from VOCs and NOx reactions; cause eye irritation and are toxic to plants.
sulfur oxides	Gaseous sulfur-oxygen compounds, primarily SO2, released from coal-burning power plants; react with water vapor to form sulfuric acid and contribute to acid deposition.

How to review unit 7

Topics students miss most

Miss rates come from Fiveable multiple-choice practice.

7.4

Atmospheric CO2 and Particulates

35%1,770 tries

7.6

Reduction of Air Pollutants

33%1,781 tries

7.5

Indoor Air Pollutants

32%2,339 tries

Common unit 7 mistakes

Confusing primary and secondary pollutants

SO2 and NOx are primary pollutants emitted directly from combustion. Tropospheric ozone, sulfuric acid, and nitric acid are secondary pollutants formed in the atmosphere. Students often misclassify ozone as primary because it is so commonly discussed.

Mixing up smog and acid rain precursors

Both smog and acid rain involve NOx, but photochemical smog also requires VOCs and sunlight, while acid rain requires SO2 or NOx reacting with water vapor. Sulfur dioxide is a major acid rain precursor but is not a direct smog ingredient.

Describing thermal inversion backwards

During an inversion, the surface air is cooler and the air above is warmer, which is the reverse of normal. Students sometimes describe it as warm air at the surface trapping pollution, which is the normal condition that allows dispersion.

Forgetting that radon is a natural indoor pollutant

Radon is not a product of human activity. It forms from uranium decay in soil and rock and enters homes passively. Confusing it with combustion pollutants like CO leads to incorrect source identification on exam questions.

Assuming all regions are equally affected by acid rain

Limestone bedrock neutralizes acid inputs through calcium carbonate buffering, so lakes and soils in limestone regions are less damaged. Granite or other non-buffering bedrock regions suffer greater acidification. The exam tests this distinction directly.

How this unit shows up on the AP exam

Source-to-effect reasoning

AP Environmental Science questions frequently ask you to trace a pollutant from its emission source through atmospheric processes to an environmental or health effect. For Unit 7, practice writing that chain for photochemical smog (vehicle NOx and VOCs to ground-level ozone to respiratory harm) and for acid rain (coal plant SO2 to sulfuric acid to lake acidification), including how limestone buffering modifies the outcome.

Propose and justify a solution

Free-response questions often present a pollution scenario and ask you to identify a specific technology or policy that would reduce it and explain the mechanism. For Unit 7, be ready to name the correct device (catalytic converter, scrubber, electrostatic precipitator, or vapor recovery nozzle), state what pollutant it targets, and explain how it works rather than just naming it.

Distinguish categories and classify examples

Multiple-choice and free-response items test whether you can correctly classify pollutants as primary or secondary, indoor sources as natural, human-made, or combustion, and reduction strategies as regulatory, conservation, or alternative-fuel approaches. Misclassifying ozone as primary or radon as a combustion product are common errors that cost points.

More ways to review

Topic study guides

Open the individual guides for Unit 7 when you want a closer review of one topic.

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Practice questions

Use AP-style practice after you review the notes so you can check what you understand.

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FRQ practice

Practice free-response reasoning and compare your answer with scoring guidance.

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Cram archive videos

Watch past review streams filtered to Unit 7 when you want a video walkthrough.

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Official unit cheatsheet

Open the Fiveable one-page unit review, then explore visual cheatsheets for a quick refresher.

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Score calculator

Estimate your broader AP score goal after you review the course and exam format.

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Unit 7 printables

Print the unit cheatsheets ($3) for Unit 7. Yours to keep, no subscription needed.

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Frequently Asked Questions

What's on the APES Unit 7 progress check (MCQ and FRQ)?

The APES Unit 7 progress check includes both MCQ and FRQ parts drawn from all 8 topics in the unit. MCQ questions test your ability to identify pollutant types, explain thermal inversion and photochemical smog formation, and analyze the causes and effects of acid rain. The FRQ portion typically asks you to describe a pollution scenario, explain its environmental or health impacts, and propose reduction strategies. Practice with matched questions at /ap-enviro/unit-7.

How do I practice APES Unit 7 FRQs?

APES Unit 7 FRQs most often pull from air pollution sources and effects, acid rain chemistry, thermal inversion, and pollution reduction strategies. A typical question gives you a scenario, then asks you to identify the pollutant, explain the mechanism, and evaluate a solution. To practice, write out full responses to past prompts, check them against College Board scoring guidelines, and focus on using precise vocabulary like primary vs. secondary pollutants. Find practice FRQs for this unit at /ap-enviro/unit-7.

Where can I find APES Unit 7 practice questions?

The best place to find APES Unit 7 practice questions, including multiple-choice and practice test sets, is /ap-enviro/unit-7. You'll find MCQs covering photochemical smog, thermal inversion, acid rain, indoor air pollutants, and noise pollution, along with FRQ practice that mirrors the real exam format. Working through a full practice test for this unit helps you spot which of the 8 topics need more attention before exam day.

How should I study APES Unit 7?

Start by building a clear picture of how air pollution works: trace a pollutant from its source through its effects, using topics like photochemical smog formation and thermal inversion to understand why pollution gets trapped near the ground. Then move to acid rain, atmospheric CO2, and indoor pollutants before finishing with reduction strategies and noise pollution. A few concrete steps that work well:
- Draw a cause-and-effect diagram for each major pollutant type.
- Memorize the difference between primary and secondary pollutants with real examples.
- Practice explaining thermal inversion and photochemical smog out loud, since these show up often on both MCQ and FRQ.
- Use the progress check as a self-test after finishing all 8 topics. All study guides and practice for this unit are at /ap-enviro/unit-7.

Ready to review Unit 7?Start with the notes, check the topic cards, and use the practice or resource links when they are available for this course.

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