AP Environmental Science Aquatic and Terrestrial Pollution Guide
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Aquatic and Terrestrial Pollution in the AP Environmental Science blueprint
College Board assigns Unit 8, Aquatic and Terrestrial Pollution, 7–10% of AP Environmental Science multiple-choice questions. This range describes the multiple-choice section, not a percentage of the total exam score.
Aquatic and Terrestrial Pollution
- May 2027
- Bluebook
- Clean-room teaching
- Read the evidence surface.
- Trace the environmental mechanism.
- Check units, scale, and claim scope.
What Aquatic and Terrestrial Pollution covers
Within Aquatic and Terrestrial Pollution, use these routes to connect official topics to evidence, calculations, and environmental decisions.
Unit 8: Aquatic and Terrestrial Pollution
8.1 Sources of Pollution
When studying Aquatic and Terrestrial Pollution, point sources discharge from identifiable locations, while nonpoint pollution is diffuse across a landscape.
8.2 Human Impacts on Ecosystems
8.3 Endocrine Disruptors
8.4 Human Impacts on Wetlands and Mangroves
8.5 Eutrophication
8.6 Thermal Pollution
8.7 Persistent Organic Pollutants (POPs)
8.8 Bioaccumulation and Biomagnification
8.9 Solid Waste Disposal
8.10 Waste Reduction Methods
8.11 Sewage Treatment
8.12 Lethal Dose 50% (LD50)
8.13 Dose Response Curve
A dose-response curve relates exposure dose to the frequency or magnitude of an effect and may include a threshold or no-threshold model.
8.14 Pollution and Human Health
Pollutant risk depends on hazard and exposure, including dose, route, duration, susceptibility, and persistence.
8.15 Pathogens and Infectious Diseases
Pathogens cause infectious disease and can spread through water, food, vectors, air, or direct contact depending on the organism.
Vocabulary anchors
Sources of Pollution; Human Impacts on Ecosystems; Endocrine Disruptors; Human Impacts on Wetlands and Mangroves; Eutrophication; Thermal Pollution; Persistent Organic Pollutants (POPs); Bioaccumulation and Biomagnification; Solid Waste Disposal; Waste Reduction Methods; Sewage Treatment; Lethal Dose 50% (LD50) are the official topic anchors used throughout this unit.
cattail
Their outflow concentrations differ.
Nitrification does not create phosphorus.
about 72.2% — (18-5)/18 ×100≈72.2%.
That is the fraction remaining.
They are chemically distinct.
Evidence lab: Reservoir profiles after two discharges
Reservoir profiles after two discharges Measurements were made 500 m below each discharge point. Site | Surface temperature (°C) | Bottom DO (mg/L) | Chlorophyll-a (µg/L) reference | 22 | 8.1 | 5 heated effluent | 29 | 5.4 | 6 fertilizer tributary | 23 | 2.2 | 41
Which site shows the strongest eutrophication signal?
fertilizer tributary — It combines high chlorophyll with very low bottom dissolved oxygen.
Its chlorophyll is low and oxygen high. Its main contrast is temperature. The indicators are not equal.
Uses two diagnostic indicators together.
Why can thermal pollution lower dissolved oxygen?
Warmer water holds less oxygen and can increase organismal respiration. — Solubility and biological demand can act in the same direction.
Heating does not create oxygen. Cold water can hold more dissolved gas. It also affects gas solubility and metabolism.
Connects temperature to physical and biological oxygen controls.
By what percent is bottom DO lower at the fertilizer site than the reference?
about 72.8% — (8.1-2.2)/8.1 ×100≈72.8%.
That is the remaining fraction. The denominator is reversed. A concentration difference is mislabeled as percent.
Calculates relative oxygen decline with reference denominator.
Why can a persistent organic pollutant remain a risk after discharge stops?
Resistance to degradation and storage in sediments or tissues can prolong exposure. — Persistence creates long environmental residence and delayed release.
That reverses the definition. Fate depends on chemical properties. Existing reservoirs can continue releasing contaminant.
Traces persistence through environmental reservoirs.
Which management package addresses both observed stressors?
Limit nutrient loads, restore riparian retention, cool or diffuse heated discharge, and monitor depth profiles seasonally. — The package targets nutrient inputs, temperature, and stratified oxygen response.
More nutrients can intensify oxygen depletion. That misses bottom hypoxia. That transfers risks rather than controlling their causes.
Integrates source controls with depth-resolved verification.
pike
Its concentration is the lowest.
The table shows the opposite. It describes feeding position.
7 times — 1.47/0.21=7.
The values are subtracted. The ratio is reversed. A decimal place is shifted.
Computes a unitless concentration ratio.
That can spread contamination.
Evidence lab: Wastewater and toxicity tests
Wastewater and toxicity tests Effluent was tested after each treatment stage; mortality is from a 96-hour bioassay. Stage | BOD (mg/L) | Fecal coliform (CFU/100 mL) | Mortality at 50% effluent influent | 210 | 180000 | 90 secondary | 24 | 12000 | 45 disinfected | 23 | 80 | 42
Which stage most sharply reduces fecal coliform after secondary treatment?
disinfection — The count falls from 12,000 to 80 CFU/100 mL.
No screening row is shown. The secondary row remains high. The table shows a large decline.
Compares sequential microbial counts.
Why does secondary treatment reduce BOD?
Microbes metabolize biodegradable organic matter, lowering later oxygen demand. — Biological oxidation removes much of the substrate that consumes oxygen.
That would tend to increase BOD. That is not the treatment mechanism. BOD concerns oxygen demand from degradable matter.
Connects biological treatment to oxygen demand.
What percent BOD reduction occurs from influent to secondary effluent?
about 88.6% — (210-24)/210 ×100≈88.6%.
That is the remaining fraction. The reduction is divided by the outlet.
Computes treatment efficiency with influent baseline.
What does persistent mortality after disinfection imply?
A nonmicrobial toxicant or treatment by-product may remain, so pathogen counts alone do not establish safety. — The two endpoints respond to different hazards.
BOD changes little across that stage. The coliform decline is not matched by mortality. They measure biological response to exposure.
Interprets divergent health and treatment endpoints.
Which follow-up establishes a dose-response relationship?
Expose replicated organisms to several effluent concentrations plus clean-water and solvent controls, then estimate effect concentration with uncertainty. — Multiple doses and controls support a fitted response rather than a single-point claim.
One dose cannot define response shape. Without a control, background mortality is unknown. Selective reporting biases the estimate.
Designs replicated multi-dose toxicology with controls.
Evidence lab: School solid-waste audit
School solid-waste audit Masses are weekly averages. Material | Discarded (kg) | Currently recycled or composted (kg) food | 310 | 190 paper | 240 | 150 plastic | 180 | 45 metal | 70 | 49
Continue in the A+ teaching layer for the remaining evidence labs, figure, and final audit.
How the AP Environmental Science assesses Aquatic and Terrestrial Pollution
| Item | Weight / count | What it means |
|---|---|---|
| Official topic denominator | 15 | |
| Multiple choice | 80 questions in 90 minutes | |
| Free response | 3 questions in 70 minutes | |
| Calculation credit | ||
| Administration | May 2027 |
Wastewater BOD reduction
Read each question as it appears on the exam paper, choose your answer, then tap it to see the feedback.
Practice 1: Calculate wastewater BOD removal
Treatment lowers biochemical oxygen demand (BOD) from 180 mg/L to 27 mg/L.
What percent of the BOD was removed by the treatment?
Select the best answer.
A. 27 ÷ 180 × 100 = 15%
❌ Not quite 😭 This calculates the fraction remaining after treatment, not the fraction removed. It does not answer the wording of the question.
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B. (180 − 27) ÷ 180 × 100 = 85%
✅ Correct! 😊 This finds the concentration decrease and compares it with the influent baseline. The result is the requested removal percentage.
C. 180 − 27 = 153%
❌ Not quite 😭 The subtraction gives a concentration difference of 153 mg/L. A difference is not a percentage until it is divided by a baseline and multiplied by 100.
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D. (180 − 27) ÷ 27 × 100 ≈ 567%
❌ Not quite 😭 This divides by the treated concentration instead of the original concentration. Reversing the reference value greatly overstates treatment performance.
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Full explanation
- Step 1Find the removed BOD: 180 − 27 = 153 mg/L.
- Step 2Use the influent concentration, 180 mg/L, as the original baseline.
- Step 3Calculate 153 ÷ 180 × 100 = 85%.
Practice 2: Design a wastewater dose-response test
Disinfected wastewater has a low fecal coliform count, but exposed test organisms still show mortality.
Design an investigation to determine whether mortality changes with wastewater concentration. Include the treatment range, controls, replication, response variable, and an appropriate conclusion rule.
Show your work.
A. Expose one organism to full-strength wastewater and report whether it survives.
❌ Not quite 😭 One organism at one dose provides neither replication nor a response curve. Background mortality and individual variation cannot be evaluated.
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B. Expose replicated groups to several wastewater concentrations plus clean-water and solvent controls, then compare mortality after equal time.
✅ Correct! 😊 Multiple doses reveal response shape, while replication and controls support comparison with background effects. Equal exposure time keeps the endpoint consistent.
C. Test several concentrations but omit a clean-water control because every group contains wastewater.
❌ Not quite 😭 Several doses may show a gradient, but without a control the investigator cannot estimate mortality unrelated to the wastewater exposure.
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D. Use one concentration, expose groups for different durations, and keep only the result with the highest mortality.
❌ Not quite 😭 Changing duration confounds dose with exposure time, and selective reporting biases the estimate. The design does not test concentration cleanly.
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Full explanation
- Step 1Set wastewater concentration as the independent variable and mortality after a fixed exposure as the dependent variable.
- Step 2Use several concentrations spanning low to high exposure and replicate each treatment.
- Step 3Include clean-water and any needed solvent controls to measure background effects.
- Step 4Compare mortality across concentrations and report the pattern with uncertainty rather than relying on one dose.
Key terms for Aquatic and Terrestrial Pollution
- Sources of Pollution
- Human Impacts on Ecosystems
- Endocrine Disruptors
- Human Impacts on Wetlands and Mangroves
- Eutrophication
- Thermal Pollution
- Persistent Organic Pollutants (POPs)
- Bioaccumulation and Biomagnification
- Solid Waste Disposal
- Waste Reduction Methods
- Sewage Treatment
- Lethal Dose 50% (LD50)
Aquatic and Terrestrial Pollution FAQ
Why is a point source easier to regulate than nonpoint runoff?
A point source has a discrete discharge location that can be monitored and permitted. Nonpoint pollution arises across landscapes and events, so management often targets practices, land cover, and watershed loads.
What is the complete eutrophication mechanism?
Nutrient enrichment can increase algal production; dead biomass is decomposed; microbial respiration raises biological oxygen demand; dissolved oxygen falls, especially in poorly mixed bottom water.
How are bioaccumulation and biomagnification different?
Bioaccumulation is contaminant buildup within an organism through time. Biomagnification is increasing concentration at higher trophic levels through dietary transfer of a persistent, biologically retained substance.
What does an LD50 value permit me to conclude?
It estimates the dose lethal to half a tested population under specified conditions. It does not define every sublethal effect, chronic risk, human sensitivity, or environmental exposure scenario.
Why does wastewater safety require more than one endpoint?
BOD, nutrients, pathogens, toxic chemicals, and biological responses represent different hazards. A process that disinfects effectively may leave dissolved toxicants, while low BOD does not prove pathogen removal.
Continue through the APES system
How to study Aquatic and Terrestrial Pollution
Trace water pollution through source, transport, transformation, exposure, and endpoint. Keep concentration separate from total load, and compare surface, depth, upstream, downstream, influent, and effluent locations before assigning a mechanism.
Rehearse treatment as a sequence: physical separation, biological oxidation, nutrient control, disinfection, and residuals management. For each stage, name what it removes, what it does not remove, and which measurement verifies performance.
For toxicology, draw a dose-response curve and label population, route, duration, endpoint, control, and uncertainty. Distinguish acute lethality from chronic or endocrine effects and relate laboratory dose to realistic environmental exposure cautiously.
