Pollution
50 exam-style questions with answers for 3.4 Pollution in AQA A-level Environmental Science (spec 7447). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, Five Degrees, Associations, or read every question and answer below. Not official AQA material.
All 50 questions and answers
Question 1
Distinguish between bioaccumulation and biomagnification. [2 marks]
Answer:Bioaccumulation is the build-up of a substance in one organism as it is absorbed faster than it is excreted. Biomagnification is the rise in concentration up a food chain.Question 2
Explain how a temperature inversion causes smog. [3 marks]
Answer:A layer of cold dense air is trapped under warmer air. Pollutants cannot rise and disperse, so concentrations build up, especially in valleys with low wind.Question 3
State what ALARA means. [1 mark]
Answer:As Low As Reasonably Achievable: exposure to ionising radiation is kept as low as possible where the benefits outweigh the risks.Question 4
Distinguish between a primary and a secondary pollutant. [2 marks]
Answer:A primary pollutant is released directly. A secondary pollutant forms from reactions of primary pollutants, such as ozone or PANs.Question 5
Explain how acid rain forms. [3 marks]
Answer:Burning fossil fuels releases sulfur dioxide and NOx, which dissolve in water to form sulfurous, sulfuric and nitric acids.Question 6
Describe how flue gas desulfurisation (FGD) works. [2 marks]
Answer:SO2 reacts with calcium carbonate (dry) or dissolves in a sulfite solution (wet), forming solid calcium sulfate.Question 7
Explain how catalytic converters reduce pollution. [3 marks]
Answer:Catalysts reduce NOx to nitrogen and oxygen, and oxidise CO and hydrocarbons to CO2 and water.Question 8
Explain how eutrophication occurs. [4 marks]
Answer:Nitrates and phosphates cause algal blooms that shade submerged plants. Plants and algae die, bacteria decompose them using oxygen, and deoxygenation kills fish.Question 9
State two health effects of nitrates in drinking water. [2 marks]
Answer:Blue baby syndrome (methaemoglobinaemia) and a possible link to stomach cancer.Question 10
Describe the stages of sewage treatment. [4 marks]
Answer:Pre-treatment screens and grit traps, primary sedimentation, secondary aerobic decomposition (activated sludge or filter beds), then tertiary phosphate removal and UV or microfiltration.Question 11
State what the decibel scale shows. [1 mark]
Answer:Sound intensity on a logarithmic scale, so a 10 dB rise is a ten-fold increase.Question 12
Explain why DDT causes environmental problems. [3 marks]
Answer:It is persistent and liposoluble, so it bioaccumulates and biomagnifies up food chains, thinning the eggshells of birds of prey.Question 13
Explain how double hulls reduce oil spills. [1 mark]
Answer:If the outer hull is damaged the inner hull contains the oil.Question 14
Describe critical pathway analysis. [2 marks]
Answer:It identifies the route a pollutant is most likely to take, so monitoring is focused where it will concentrate.Question 15
State how acid mine drainage is controlled. [2 marks]
Answer:Collect the drainage water and neutralise it with lime or crushed limestone.Question 16
Define the term ‘synergism’. [1 mark]
Answer:The combined effect of two substances is greater than the sum of their separate effects.Question 17
Define the term ‘persistence’. [1 mark]
Answer:How long a pollutant remains before it breaks down.Question 18
Distinguish between a point source and a diffuse source. [2 marks]
Answer:A point source is a single location such as a chimney. A diffuse source has many small sources, such as vehicles.Question 19
Describe how smoke smog forms. [2 marks]
Answer:Smoke particles and fog accumulate under a temperature inversion.Question 20
Describe how an electrostatic precipitator works. [2 marks]
Answer:Charged wires attract smoke particles from flue gas, which stick and are collected.Question 21
Explain how photochemical smog forms. [3 marks]
Answer:UV light drives reactions between NOx, hydrocarbons and ozone, producing PANs that concentrate under a temperature inversion.Question 22
Explain why carbon monoxide is harmful. [2 marks]
Answer:It binds to haemoglobin, reducing oxygen carriage.Question 23
Explain how thermal pollution harms aquatic life. [2 marks]
Answer:Warm water holds less dissolved oxygen, so deoxygenation kills organisms.Question 24
State how cooling towers reduce thermal pollution. [1 mark]
Answer:Heat is transferred to the atmosphere before water is discharged.Question 25
Describe how oil spills affect birds. [3 marks]
Answer:Oil causes toxicity, asphyxiation and loss of insulation. Birds spend longer preening, so feed their young less.Question 26
Describe two oil spill clean-up methods. [2 marks]
Answer:Booms contain oil, skimmers collect it, dispersants break it up, and bioremediation uses bacteria.Question 27
Explain why methyl mercury is more harmful than elemental mercury. [2 marks]
Answer:It is absorbed strongly and crosses the blood-brain barrier, while liquid elemental mercury is hardly absorbed through the gut.Question 28
Evaluate landfill for solid waste. [3 marks]
Answer:Low cost, but causes methane and leachate pollution, loses resources and uses land.Question 29
Evaluate incineration for solid waste. [3 marks]
Answer:Reduces volume and can generate energy, but loses resources, may release dioxins below 1000 °C and can discourage recycling.Question 30
State the units used for radioactivity. [3 marks]
Answer:Becquerel for activity, gray for absorbed dose, sievert for effective dose.Question 31
Define the term ‘pollutant’. [1 mark]
Answer:A substance, or form of energy, in the environment at a concentration that causes harm to living organisms or the environment.Question 32
Define the term ‘mobility’ in relation to a pollutant. [1 mark]
Answer:The ability of a substance to move and disperse in air, water or living organisms.Question 33
Define the term ‘liposolubility’. [1 mark]
Answer:The ability of a substance to dissolve in lipids (fats), so it can be stored in fatty tissues and cell membranes.Question 34
Explain how acid deposition harms freshwater lakes. [3 marks]
Answer:Lower pH damages eggs, gills and organisms with exposed membranes (1); acid mobilises toxic aluminium ions from soil which poison fish (1); loss of species breaks food chains, so biodiversity falls (1).Question 35
Explain how the health effects of ground-level ozone arise. [2 marks]
Answer:Ozone is a strong oxidising agent that irritates and damages lung tissue (1); causes breathing difficulty and aggravates asthma and respiratory disease (1).Question 36
Describe the health effects of particulates such as PM10. [2 marks]
Answer:Tiny particles are inhaled deep into the lungs (1); cause or aggravate asthma, bronchitis and heart disease (1).Question 37
Explain why municipal waste incinerators must burn at high temperature. [2 marks]
Answer:Temperatures above 1000°C are needed to prevent the formation of dioxins (1); dioxins are persistent, toxic and carcinogenic (1).Question 38
Describe the features of a well-managed landfill site. [3 marks]
Answer:Any three: triple polymer liner; leachate collection and treatment; methane collection (used as fuel); no toxic waste accepted; daily soil cover; waterproof cap when completed; fences against litter.Question 39
Describe how high-level radioactive waste is stored. [3 marks]
Answer:Dried powdered waste is mixed with molten glass (vitrification) (1); sealed in stainless steel containers (1); stored in concrete blocks with cooling air channels to absorb radiation and remove heat (1).Question 40
Explain how the inverse square law is used to reduce radiation exposure. [2 marks]
Answer:Radiation intensity falls with the square of the distance from the source (1); doubling distance reduces exposure to a quarter, so remote handling equipment is used (1).Question 41
Distinguish between exposure and contamination. [2 marks]
Answer:Exposure is the absorption of radiation (1); contamination is physically carrying the source of radiation (so exposure also occurs) (1).Question 42
Explain why alpha radiation is most dangerous if ingested. [3 marks]
Answer:Alpha particles are strongly ionising with a high RBE (about 20) (1); they cannot penetrate skin but if inside the body all their energy is absorbed in a small volume of tissue (1); causing intense local damage to cells and DNA (1).Question 43
Explain why isotopes with medium half-lives pose the greatest radiation risk. [2 marks]
Answer:Emission rate is high enough to be harmful (1); half-life is too long to avoid the source until it is safe, unlike short half-lives, whereas long half-lives emit slowly (1).Question 44
Describe the effects of noise on humans. [3 marks]
Answer:Hearing damage to hair cells in the cochlea (1); stress, raised blood pressure and heart disease through increased adrenalin (1); irritability, sleep loss and difficulty concentrating (1).Question 45
State two ways of reducing aircraft noise. [2 marks]
Answer:Any two: night flight restrictions; flight paths avoiding urban areas; quieter engines with chevron nozzles; steep climb after take-off; constant 3° descent angle; acoustic insulation of nearby homes; fines for excess noise.Question 46
Describe bioremediation of an oil spill. [2 marks]
Answer:Microorganisms (bacteria) are encouraged to break down hydrocarbons (1); nutrients such as nitrogen and phosphorus may be added to speed up their growth (1).Question 47
Compare organochlorine and organophosphate insecticides. [3 marks]
Answer:Organochlorines (eg DDT): highly persistent, liposoluble, bioaccumulate and biomagnify, low toxicity to mammals (2); organophosphates (eg malathion): low persistence and bioaccumulation but high toxicity to mammals (1).Question 48
Describe how nitrate pollution from farming can be controlled. [3 marks]
Answer:Use of low-solubility fertilisers such as urea (1); nitrate vulnerable zones: no fertiliser in winter, reduced applications, slurry stored in tanks (1); cover crops absorb nitrates over winter (1).Question 49
Explain how low-sulfur fuels and flue gas desulfurisation reduce acid rain. [2 marks]
Answer:Low-sulfur fuels release less sulfur dioxide when burned (1); FGD removes SO2 from flue gases using lime/limestone to form calcium sulfate/gypsum (1).Question 50
Distinguish between acute and chronic effects of radiation. [2 marks]
Answer:Acute effects occur rapidly, usually from a high dose (1); chronic effects develop slowly, usually from low doses over a long time, eg cancer (1).