Flashcards · 5014 · Topic 3

Water flashcards

25 cards on Topic 3, subtopics 3.1 to 3.6. Pick a subtopic or study them all.

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Infiltration vs surface run-off vs through-flow: Infiltration: water soaking into the soil. Surface run-off: water flowing over the ground surface. Through-flow: water moving sideways through the soil.
Where can fresh water be obtained?: From the atmosphere (rain), surface water (lakes and rivers), ground water (wells and aquifers) and desalinated sea water.
Put the water treatment stages in order and give the purpose of each: Screening removes large objects; sedimentation lets particles settle; filtration through sand and gravel removes fine particles; chlorination kills microorganisms. The result is potable (drinkable) water.
How does reverse osmosis desalinate water?: Pressure forces sea water through a membrane that holds back the salt. It usually uses less energy than distillation, but the membranes need maintenance.
Give two benefits and two limitations of a multipurpose dam: Benefits: hydro-electric power, flood control, irrigation water, storage, recreation. Limitations: high cost, people and habitats displaced, silt trapped, river ecosystems downstream disrupted.

Explain how fertiliser run-off can kill fish in a lake: Nutrients cause an algal bloom, which blocks light so plants die. Bacteria decomposing the dead material use up the oxygen, and fish suffocate. This is eutrophication.
Why do top predators have the highest levels of some toxins?: Biomagnification: the toxin builds up in each organism (bioaccumulation) and its concentration increases at each step up the food chain.
Which diseases are linked to sewage in water?: Infectious waterborne diseases such as cholera, spread when untreated sewage contaminates drinking water.
How can acid rain pollute fresh water?: Sulfur dioxide and nitrogen oxides from the air dissolve in rain, which lowers the pH of lakes and rivers and harms aquatic organisms.

Malaria vs cholera: how is each spread?: Malaria: vector-borne, spread by the bite of an infected female Anopheles mosquito. Cholera: waterborne, spread by drinking water or eating food contaminated with the bacterium.
Why do insecticide-treated bed nets reduce malaria?: Anopheles mosquitoes bite mainly at night, so nets protect sleepers, and the insecticide kills mosquitoes that land on them.
Why does draining standing water help control malaria?: Mosquitoes lay their eggs in standing water, so removing it reduces the number of vectors.
Give a limitation of vaccination as a way to control cholera: Vaccines may not reach everyone at risk, especially in poor or disaster-hit areas, and they do not replace the need for clean water and sanitation.

Define marine aquaculture: Farming marine species, such as fish, crustaceans and seaweeds, in captivity.
Overfishing vs overharvesting: Overfishing: catching fish faster than stocks can reproduce. Overharvesting: taking any wild species, such as shellfish or seaweed, faster than it can recover.
Give two problems marine aquaculture can cause: Farmed animals can escape and spread disease to wild stocks, and waste and uneaten feed cause nutrient enrichment. Wild fish may also be caught to feed farmed species.
How do mesh sizes, quotas and closed seasons protect fish stocks?: Larger mesh lets young fish escape to breed; quotas limit the total catch; closed seasons stop fishing while fish breed.

Name sources of oil pollution at sea: Off-shore oil extraction, pipelines, shipping and tanker accidents, cleaning tanks at sea, and refineries on shore.
Why is oil so harmful to seabirds?: It coats their feathers, which then lose their insulation and waterproofing, and birds swallow it while preening.
What is MARPOL?: The International Convention for the Prevention of Pollution from Ships, which sets international rules to prevent pollution, including oil discharges, from ships.
Prevention vs minimising the impact of oil spills: Prevention: MARPOL, double-hulled tankers, risk assessments, regular maintenance. Minimising impact: improved navigation, booms, sorbents, skimmers, detergent sprays, controlled burning.

Does a bioplastic always biodegrade?: No. Bioplastics are made fully or partly from biological material, but some are not biodegradable.
Define microplastics: Plastic pieces smaller than 5 mm, formed when larger plastic items break down.
How do plastics harm marine animals?: Animals become entangled, or mistake plastic for food, and plastics and their chemicals build up in organisms and food chains.
Suggest ways to reduce plastic pollution: Use alternative packaging, avoid single-use plastics, dispose of waste safely, recycle, and pass and enforce laws.