Cambridge O Level Environmental Management: Water — Revision Notes (5014, 2027-2029)

Syllabus edition note. These notes follow the Cambridge O Level Environmental Management 5014 syllabus for exams in 2027, 2028 and 2029, in which Topic 3 Water has six sub-topics, including oil pollution and plastic pollution.

Topic 3 Water of Cambridge O Level Environmental Management (5014) covers where fresh water comes from, how it is made safe, what pollutes it, the diseases linked to it, how the sea is fished and farmed, and the two marine pollution problems of oil and plastic. It is the largest topic in the syllabus, so learn it as six short checklists and practise linking causes to impacts to management.

Full explanations: Water study guide. Test yourself: Water practice questions.

Syllabus coverage (5014, 2027-2029)

Sub-topic	Outcomes
3.1 Water sources and supply	3.1.1-3.1.10: water cycle; fresh water sources; oceans; potable water; treatment; global availability; desalination; multipurpose dams
3.2 Water pollution	3.2.1-3.2.3: sources; impacts; improving water quality
3.3 Water-related diseases	3.3.1-3.3.4: malaria transmission and control; cholera control
3.4 Marine aquaculture	3.4.1-3.4.5: exploitation; definition; impacts; managing harvesting
3.5 Oil pollution	3.5.1-3.5.4: causes; impacts; prevention; minimising impacts
3.6 Plastic pollution	3.6.1-3.6.7: plastic types; microplastics; impacts; strategies

3.1 Checklist: water sources and supply

• Stores: oceans (salt water); ice sheets and glaciers, ground water, atmosphere, lakes and rivers (fresh water).
• Transfers: precipitation, interception, surface run-off, infiltration, through-flow, ground water flow, transpiration, evaporation, condensation.
• Fresh water sources: rain and snow; rivers, lakes and reservoirs; aquifers and wells; desalinated sea water.
• Five oceans: Pacific, Atlantic, Indian, Southern, Arctic.
• Potable water = water that is safe to drink. Treatment: screening → sedimentation → filtration → chlorination.
• Availability differs between water-rich and water-poor regions and between urban and rural areas; there are global inequalities in both water and sewage treatment.

Desalination

• Distillation: heat water until it boils; salt stays in the liquid; steam is cooled and condensed.
• Reverse osmosis: high pressure pushes water through a membrane that stops most ions.
• Benefit: a reliable supply where rivers and aquifers are scarce. Limitation: high energy use and cost, and salty waste (brine).

Multipurpose dam uses: flood control, hydro-electric power, irrigation, water storage, transport, recreation, tourism, fish farming. Limitations include flooding of land and homes, loss of habitats, sediment trapped behind the dam and high construction cost.

3.2 Checklist: water pollution

Source	Impact
Sewage, domestic waste	Cholera bacteria; nutrient enrichment
Plastic waste	Entanglement; ingestion
Industrial processes	Toxic substances accumulate; bioaccumulation and biomagnification
Agricultural practices	Leaching of fertiliser → nutrient enrichment → eutrophication
Acid rain	Acidifies rivers and lakes, harming organisms

• Bioaccumulation = build-up of a toxin in one organism over time.
• Biomagnification = increase in concentration of a toxin up a food chain.
• Eutrophication chain: nutrients → algal bloom → light blocked, plants die → bacteria decompose them, using oxygen → fish die.
• Improving quality: improved sanitation; sewage treatment; pollution control and legislation.

3.3 Checklist: malaria and cholera

Malaria: vector = female Anopheles mosquito; parasite = Plasmodium, passed to humans in a bite and back to uninfected mosquitoes when they feed on infected blood.

Malaria control	Cholera control
Personal: nets, repellent, vaccination, antimalarial drugs	Handwashing
Vector: cover or drain breeding sites, spray insecticide, sterilise male mosquitoes, biological control	Sanitation and sewage treatment; potable water by boiling and chlorination; vaccination

Malaria is spread by a vector; cholera is spread by contaminated water - so their controls differ.

3.4 Checklist: exploitation and marine aquaculture

• Exploitation impacts: overfishing and overharvesting; effects on target and bycatch species; disrupted food chains.
• Marine aquaculture = farming of marine species in captivity: fish, crustaceans, seaweeds.
• Impacts: reduces pressure on wild fisheries; more food for people; but risk of escape, disease, effects on local food webs, nutrient enrichment from waste, energy use, and the need to catch wild fish as feed.
• Managing harvesting: limits on boat and net size; larger mesh so young fish escape; pole and line; quotas; closed seasons; limited fishing days; protected areas; conservation laws; international agreements with implementation and monitoring.

3.5 Checklist: oil pollution

• Causes: offshore and onshore extraction; pipelines; shipping; cleaning tanks at sea; refineries.
• Impacts on: birds (oiled feathers lose insulation and buoyancy); marine mammals; fish; crustaceans; seaweeds; coral reefs; beaches.
• Prevention: MARPOL (International Convention for the Prevention of Pollution from Ships); double-hulled tankers; risk assessments; regular maintenance.
• Minimising impacts: improved navigation systems; booms and sorbents; detergent sprays; skimmers; controlled burning.

3.6 Checklist: plastic pollution

Type	Key point
Conventional plastics	Made from fossil fuels; generally non-biodegradable
Bioplastics	Fully or partly made from biological raw materials; can be biodegradable or not
Biodegradable plastics	Designed to decompose in water or soil by bacteria and fungi into water, biomass and gases (CO2, methane); rate depends on biotic and abiotic factors
Non-biodegradable plastics	Break down over a long period
Microplastics	Less than 5 mm; from larger plastics breaking down or used in products

Impacts on marine ecosystems: visual pollution; entanglement; mistaken for food; bioaccumulation and biomagnification. Strategies: alternative packaging; avoid single-use plastics; safe disposal; recycling; legislation and enforcement.

Worked example: biomagnification

A toxin in sea water is at 0.001 units. Concentration multiplies by 10 at each feeding level: plankton 0.01 → small fish 0.1 → large fish 1 → seabird 10 units. The seabird has 10 000 times the concentration in the water, which is why top predators are worst affected.

Common mistakes and exam traps

• Swapping bioaccumulation (one organism) and biomagnification (along a food chain).
• Saying malaria is spread by dirty water - it is spread by mosquito bites.
• Calling all bioplastics biodegradable.
• Forgetting that aquaculture needs feed, often from wild-caught fish.
• Listing oil-spill clean-up methods when the question asks about prevention.

Frequently asked questions

What are the four stages of water treatment in 5014? Screening, sedimentation, filtration and chlorination, in that order.

What size is a microplastic? Less than 5 mm in length. Microplastics form when larger plastics break down, or are added to commercial products.

What is MARPOL? The International Convention for the Prevention of Pollution from Ships. The 5014 syllabus names it as a strategy for preventing oil spills.

Official syllabus

Cambridge O Level Environmental Management (5014) syllabus for 2027, 2028 and 2029 - official syllabus PDF, Topic 3 Water.