Water pollution, food chains and quality management
Trace common pollution sources to human and ecological effects, then match water-quality strategies to the contaminant pathway.
This original StudyForA sequence supports Cambridge IGCSE Environmental Management 0680 Topics 1–4 for exams in 2027, 2028 and 2029. Named local examples are chosen by the learner and centre; verify current conditions and local context with reliable sources. It is not a Cambridge paper, official grade or complete course.
Before you begin
- Use the 2027–2029 syllabus and check your exam year and centre's entry arrangements. Topics 1–4 are taught on this page; Topics 5–7 are still being built.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which is a syllabus source of water pollution?
What you will learn
- Trace common pollution sources to human and ecological effects, then match water-quality strategies to the contaminant pathway.
- Use evidence from an unfamiliar case to explain a cause-and-effect link and justify a suitable response.
Identify pollution sources
The syllabus sources are domestic waste, sewage, plastic waste, industrial processes and agricultural practices. They can enter water directly or through runoff and drainage.
Identify the likely pollutant and route before selecting a control. For example, untreated sewage and chemical discharge require different responses.
Explain impacts with precise terms
Polluted water can increase the risk of cholera, an infectious bacterial disease. Toxic substances from industry can accumulate in an organism over time (bioaccumulation) and become more concentrated up a food chain (biomagnification).
Acid rain can affect organisms in rivers and lakes. Leached nutrients from organic matter or inorganic ions can enrich water and cause eutrophication; excess growth and decomposition can reduce oxygen available to organisms.
Control the source and the pathway
Improved sanitation and sewage treatment reduce faecal contamination. Pollution control and legislation can limit discharges, but rules require monitoring, compliance and effective infrastructure.
Good decisions pair a source control with outcome monitoring, such as water-quality tests and evidence on organisms or public health. One measure may not address every pollutant entering a catchment.
Sources for this lesson
Pause and explain
Which strategy directly addresses sewage contamination?
Worked example
A river below farms and a town has high nutrient readings and reports of illness. Explain two possible pathways and propose a first investigation.
Show the worked solution
- Agricultural nutrient runoff or leaching may enrich the water and contribute to eutrophication.
- Untreated sewage or domestic waste may raise the risk of infectious bacterial disease such as cholera.
- Sample upstream and downstream, test relevant water quality and review sanitation and farm inputs before assigning the cause.
Answer Nutrients may enter through farm runoff, while sewage can carry disease-causing bacteria. Compare upstream and downstream samples and trace sources before deciding which control is needed.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A toxic industrial substance is detected in small organisms and in larger predators. Explain bioaccumulation and biomagnification in this context.
Give me a hint
Use one term for change within an organism over time and the other for change along the food chain.
Compare my reasoning
- Bioaccumulation is the gradual build-up of a toxic substance in one organism over time.
- Biomagnification is a rise in concentration at higher levels of a food chain.
- The observations should be supported by comparable measurements and information about diet and exposure.
The substance can accumulate within organisms and become more concentrated up the food chain. Distinguish the within-organism process from the increase between trophic levels.
Look for these in your work
- Both processes correctly distinguished
- Food-chain movement explained
- Evidence limits recognized
A lake receives nutrient-rich runoff and experiences excessive plant growth. Explain the eutrophication pathway and name one useful control and one measure of change.
Give me a hint
Connect nutrient input, growth, decomposition and oxygen; measure more than appearance.
Compare my reasoning
- Leached nutrients enrich the water and can stimulate excess plant or algal growth.
- When biomass dies and decomposes, oxygen can be used up, affecting aquatic organisms.
- Reduce nutrient input through better farm or sewage controls and monitor nutrient levels, oxygen and organism conditions.
Nutrient enrichment can drive excessive growth; decomposition can lower oxygen and harm organisms. Source control plus measurements of nutrients, oxygen and biological conditions can test whether water quality improves.
Look for these in your work
- Full causal chain included
- Source control relevant
- Outcome measures specified
A town proposes legislation to reduce water pollution, but inspectors are scarce and sewage treatment is limited. Recommend a practical package and explain how it could be evaluated.
Give me a hint
Combine enforceable source control with infrastructure and outcome monitoring.
Compare my reasoning
- Prioritise basic sanitation and sewage treatment where untreated waste is a major source.
- Use targeted pollution rules for significant discharges and focus inspections on higher-risk sites.
- Track compliance and water-quality indicators upstream and downstream, then adapt the package based on results.
A practical package combines sanitation and sewage capacity with targeted pollution controls and monitoring. Evaluate compliance and water-quality trends, then adjust where evidence shows sources remain.
Look for these in your work
- Infrastructure and rules combined
- Limited enforcement addressed
- Evaluation tied to results
Common mistakes
- Confusing bioaccumulation and biomagnification
- Assuming all water pollution comes from factories
- Treating nutrient enrichment and infection as the same impact
- Recommending a law without monitoring
What can you explain now?
What is biomagnification?
Compare with the explanation
An increase in a toxic substance's concentration as it passes up a food chain
The correct answer is “An increase in a toxic substance's concentration as it passes up a food chain”. The alternatives “The settling of particles at a water-treatment plant” and “The movement of water into soil” do not match the syllabus concept. Trace common pollution sources to human and ecological effects, then match water-quality strategies to the contaminant pathway.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Trace one water-pollution source to an impact and choose a control that interrupts the pathway.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.