2025 Cambridge IGCSE Environmental Management (0680) 模擬試題連答案詳解

a) Landfill matches with C because municipal solid waste is used to fill the physical void left by mining. Bioremediation matches with A as it relies on living organisms like bacteria or plants to degrade or absorb toxic materials in the soil. Revegetation matches with B because introducing plant roots holds the soil structure together, preventing wind and water erosion. b) Allowing a quarry to fill with water can cause heavy metals and acidic compounds from the exposed rock walls to dissolve into the water, polluting local groundwater systems or presenting toxicity risks to visiting wildlife and humans.

Part (a): [3 marks total] - 1 mark for each correct matching pair: 1 matches with C, 2 matches with A, 3 matches with B. Part (b): [2 marks total] - 1 mark for identifying a valid hazard (e.g., toxic chemicals leaching from rock faces, unstable walls collapsing, deep water hazards). - 1 mark for explaining its consequence on the environment or human safety.

a) When groundwater is extracted faster than natural recharge rate, pore spaces in the soil/rock collapse, leading to land subsidence (sinking of the ground) and drying up of shallow wells and local wetlands. b) Freshwater in coastal aquifers normally maintains an seaward flow due to hydraulic pressure. Over-extraction lowers the freshwater table and reduces this pressure, which allows denser saltwater from the nearby ocean to migrate inland into the aquifer. c) An aquifer is a body of porous, permeable rock or sediment (like sandstone or gravel) that can store and conduct significant amounts of extractable groundwater.

Part (a): [2 marks] - 1 mark for each valid physical impact (e.g., land subsidence, drying up of wells, reduced river/wetland water levels). Part (b): [2 marks] - 1 mark for mentioning the reduction of freshwater pressure or lowering of the water table. - 1 mark for explaining that ocean saltwater flows inland to replace the lost freshwater. Part (c): [1 mark] - 1 mark for defining an aquifer as a permeable underground rock/sediment layer containing extractable water.

a) Fragmented habitats prevent animals from finding mates from different populations. Wildlife corridors provide physical vegetation paths connecting isolated forest patches. This permits migration, enabling gene flow, reducing the risk of inbreeding depression, and increasing overall genetic diversity. b) Seed banks dry and freeze seeds to keep them viable for decades. This acts as an insurance policy against complete extinction in the wild, and provides a genetic library for ecological restoration and crop-breeding research. c) A main limitation is that recalcitrant seeds (such as those from many tropical trees) die when dried and frozen. Additionally, seeds stored in static conditions do not naturally evolve defenses against evolving climate patterns, pests, or diseases.

Part (a): [2 marks] - 1 mark for stating that corridors connect fragmented habitats or allow individuals to migrate. - 1 mark for explaining that this migration increases gene flow or prevents inbreeding depression. Part (b): [2 marks] - 1 mark for each valid role described (e.g., backup for wild extinction, material for habitat restoration, storage of genetic varieties for agricultural/medical research). Part (c): [1 mark] - 1 mark for a valid limitation (e.g., recalcitrant seeds cannot be stored, high costs of continuous refrigeration, vulnerability to power failure, lack of adaptation/evolution during storage).

(a) Earthquakes and volcanoes are not randomly distributed; they occur in narrow bands/zones, primarily along tectonic plate boundaries. Volcanoes are found at destructive (convergent) boundaries where subduction occurs, and constructive (divergent) boundaries where magma rises. Earthquakes occur at all three types of plate boundaries: destructive, constructive, and conservative (transform) boundaries, where friction and pressure build up and are suddenly released. Some volcanoes also occur at 'hot spots' away from plate boundaries (e.g., Hawaii).

(b) (i) A seismometer is anchored to the ground. During an earthquake, the frame of the seismometer moves with the earth, while a heavy suspended mass remains relatively still due to inertia. A pen or digital sensor attached to the mass records the relative movement between the frame and the mass, producing a seismograph that shows the amplitude and frequency of seismic waves.

(ii) The Richter scale measures the magnitude (energy released) of an earthquake, whereas the Mercalli scale measures the intensity (observable effects and damage caused). The Richter scale is logarithmic (each step is a tenfold increase in amplitude), quantitative, and uses scientific instrument readings (seismometers) to give a single value. The Mercalli scale is qualitative, subjective, expressed in Roman numerals (I to XII), and varies depending on distance from the epicenter and local building standards.

(c) Reasons why people live near active volcanoes:
1. Volcanic ash and weathered volcanic rocks create highly fertile soils that are excellent for intensive agriculture.
2. Volcanoes attract tourists, providing local jobs and income in hospitality, guiding, and souvenir sales.
3. Volcanic areas can be used to generate geothermal energy, providing cheap, renewable electricity and heating.
4. Volcanic activity often brings valuable minerals and ores (e.g., sulfur, copper, gold) close to the surface, creating mining jobs.

(d) Planning, monitoring, and evacuation are vital strategies, but each has strengths and limitations:
- Monitoring: Technicians use tiltmeters to measure ground deformation, gas spectrometers to detect changes in sulfur dioxide emissions, and seismometers to detect harmonic tremors. Effectiveness: Excellent for providing early warnings, allowing evacuations before an eruption begins. Limitations: High-tech monitoring equipment is expensive and requires highly trained scientists, which may not be available in low-income countries.
- Evacuation: Moving people away from the hazard zone. Effectiveness: Directly saves lives by removing populations from dangerous areas (pyroclastic flows, lahars). Limitations: Relies on clear evacuation routes, reliable transport, and emergency shelters. False alarms can lead to public distrust and reluctance to evacuate in future events.
- Planning/Hazard Mapping: Restricting land use in high-risk zones (e.g., valleys prone to lahars) and preparing emergency response plans. Effectiveness: Minimizes long-term vulnerability by preventing high-value development in danger zones. Limitations: Relies on strict government enforcement of zoning laws, which is often bypassed in rapidly growing urban areas due to land pressure.

(a) Explain the distribution of earthquakes and active volcanoes around the world. [4]
- Award 1 mark for stating they occur in narrow bands / linear patterns along tectonic plate boundaries.
- Award 1 mark for associating volcanoes with destructive (convergent) and constructive (divergent) boundaries.
- Award 1 mark for stating earthquakes occur at all boundary types (destructive, constructive, conservative).
- Award 1 mark for mentioning anomalies / hot spots (e.g., Hawaii) or explaining that friction/subduction causes these hazards at boundaries.

(b) (i) Describe how a seismometer is used to monitor earthquake activity. [2]
- Award 1 mark for: The frame of the seismometer is anchored to the ground and moves when the ground vibrates.
- Award 1 mark for: A heavy weight (inertial mass) remains stationary, and the relative movement between the frame and weight is recorded / drawn as a seismograph.

(ii) Compare the Richter scale and the Mercalli scale as methods for measuring earthquakes. [4]
- Award 1 mark for: Richter measures magnitude/energy released, whereas Mercalli measures intensity/damage/impact on humans.
- Award 1 mark for: Richter is quantitative/objective/uses instruments, whereas Mercalli is qualitative/subjective/uses observations.
- Award 1 mark for: Richter has no upper limit (or logarithmic scale), whereas Mercalli is on a fixed scale of I to XII.
- Award 1 mark for: An earthquake has only one Richter value, but its Mercalli intensity varies depending on the distance from the epicenter / local building construction.

(c) Suggest three reasons why people choose to live in these locations. [3]
- Award 1 mark for each valid reason (up to 3):
- Fertile volcanic soils (good for farming).
- Geothermal energy potential (cheap power).
- Tourism opportunities (jobs/income).
- Extraction of valuable minerals / sulfur mining.
- Poverty/lack of choice or family ties to the region.

(d) Evaluate the effectiveness of planning, monitoring, and evacuation strategies in reducing the impact of volcanic eruptions. [7]
- Level 3 (5–7 marks): Balanced evaluation of all three strategies (monitoring, planning, evacuation). Explains how each works, highlights their strengths in saving lives/reducing damage, and clearly outlines their limitations (e.g., cost, infrastructure, enforcement, false alarms).
- Level 2 (3–4 marks): Discusses at least two strategies. Explains their benefits but has limited evaluation of their disadvantages or practical limitations.
- Level 1 (1–2 marks): Simple description of one or two strategies without evaluation of their effectiveness or limitations.
- Indicative Content:
- Monitoring: Seismic activity, gas emissions, ground tilt. High effectiveness for prediction, but expensive and requires skilled personnel.
- Evacuation: Saves lives, but needs transport, shelter, and clear communication. False alarms cause loss of trust.
- Planning/Zoning: Long-term risk reduction, prevents building in high-risk zones (e.g., lahar channels). Hard to enforce due to land shortage.

(a) Biodiversity is the variety of different species, genetic diversity within those species, and the range of different ecosystems in a given area. It is vital to maintain high biodiversity in tropical rainforests because:
- It ensures ecosystem stability; if one species declines, others can adjust, preventing food web collapse.
- It provides a vast gene pool and potential sources for new medicines and crops.
- It maintains nutrient cycling and carbon storage, which regulates global climate.

(b) (i) To use random quadrat sampling:
1. Lay out two tape measures at right angles along the edge of the \( 100\text{ m} \times 100\text{ m} \) field to act as axes (\(x\) and \(y\)).
2. Use a random number generator to obtain pairs of coordinates.
3. Place a quadrat of known size (e.g., \( 1\text{ m}^2 \)) at the generated coordinates.
4. Count and record the number of individuals of the target plant species inside the quadrat.
5. Repeat this process for a minimum of 10–20 quadrats to calculate the mean density per quadrat.
6. Multiply the mean density by the total area of the field (\( 10,000\text{ m}^2 \)) divided by the quadrat size to estimate the total population.

(ii) To ensure reliability and lack of bias:
- Randomization: Coordinates must be generated randomly, not chosen subjectively by the student, to prevent bias toward areas with high or low plant density.
- Sample size: A large number of quadrats (high sample size) must be sampled to ensure the mean is representative of the whole area, reducing anomalous results.

(c) (i) Three features of national parks that protect wild species:
1. Legal protection: Laws that ban or strictly regulate activities such as hunting, poaching, logging, and mining.
2. Active patrolling: Park rangers who monitor the area to deter and arrest poachers or illegal loggers.
3. Boundary zoning: Restricting tourist access to specific zones while keeping core areas completely wild and undisturbed.

(ii) Difficulties in developing countries:
- Financial constraints: Lack of funding for hiring sufficient park rangers, purchasing vehicles, and maintaining boundary fences.
- Conflicts with local communities: Locals may lose access to traditional land for farming, fuel wood collection, or hunting, leading to hostility.
- Poaching and illegal trade: High demand for wildlife products (e.g., ivory, exotic plants) drives illegal activities that are difficult to police in remote areas.
- Weak governance/corruption: Bribery of officials can lead to unenforced environmental laws and illegal resource extraction.

(d) Ecotourism helps conserve ecosystems by:
- Generating revenue through entry fees and tourist spending, which can directly fund conservation activities and park management.
- Creating sustainable jobs for local people (e.g., guides, lodge staff), reducing their reliance on destructive activities like slash-and-burn farming or poaching.
- Raising environmental awareness and educating tourists and locals about the value of the ecosystem.

(a) Define the term 'biodiversity' and explain why it is important to maintain high biodiversity in a tropical rainforest ecosystem. [4]
- Award 1 mark for defining biodiversity (variety of species, genes, and ecosystems).
- Award up to 3 marks for explaining importance (any three of):
- Increases ecosystem resilience / stability / prevents food web collapse.
- Genetic resource / gene pool conservation.
- Potential source of medicines / pharmaceuticals.
- Maintains ecosystem services (e.g., carbon sequestration, oxygen production, nutrient cycling).

(b) (i) Describe how the student could use random quadrat sampling to estimate this population. [4]
- Award 1 mark for establishing a coordinate grid using tape measures along the boundaries.
- Award 1 mark for using a random number generator to select sampling coordinates.
- Award 1 mark for counting the plants in a set number of quadrats.
- Award 1 mark for calculating the mean number per quadrat and scaling up to the total area of \( 10,000\text{ m}^2 \).

(ii) Explain how the student could ensure their sampling is reliable and unbiased. [2]
- Award 1 mark for: Using random numbers avoids bias (as the investigator does not choose where to place the quadrat).
- Award 1 mark for: Using a large number of quadrats (high sample size) increases the reliability of the mean.

(c) (i) Describe three features of national parks that help to protect wild species. [3]
- Award 1 mark for each valid feature (up to 3):
- Legal ban/restriction on hunting, logging, or mining.
- Patrols by rangers/wardens to prevent illegal activity.
- Fencing or clear boundary markers.
- Designated tourist zones / restricted core areas.
- Education/visitors centers.

(ii) Explain the difficulties that governments in developing countries might face when setting up and managing national parks. [4]
- Award 1 mark for each valid explanation (up to 4):
- Limited government budget / lack of money to pay for equipment/rangers.
- High pressure on land for agriculture or urban expansion due to population growth.
- Human-wildlife conflict / local communities losing access to land/resources leading to resentment.
- Difficulty in policing vast, remote areas against well-armed poachers.
- Corruption/bribery allowing illegal logging or poaching to continue.

(d) Explain how ecotourism can help to conserve ecosystems. [3]
- Award 1 mark for: Funding generated (from park fees/accommodation) is reinvested into conservation.
- Award 1 mark for: Provides alternative sustainable livelihoods for locals (e.g., tour guides) so they do not resort to poaching or logging.
- Award 1 mark for: Raises ecological awareness and educates visitors/communities about conservation.

(a) (i) Calculation of percentage difference:
Difference = \( 450 - 50 = 400 \) litres.
Percentage difference relative to Country C = \( \frac{400}{50} \times 100\% = 800\% \).
(Alternatively, using the average as the base: \( \frac{400}{250} \times 100\% = 160\% \); both approaches are accepted if mathematical steps are correct).

(ii) Reasons for the difference:
1. Availability of piped water directly into homes in Country A, whereas in Country D, water must be collected from remote communal sources.
2. Widespread use of water-intensive domestic appliances (washing machines, dishwashers, power showers, flush toilets) in high-income countries.
3. Outdoor water use (watering lawns, washing cars, swimming pools) is common in high-income countries but virtually non-existent in low-income domestic settings.
4. Differences in cost: water is often highly subsidized or relatively cheap in high-income nations compared to household income.

(b) (i) Desalination is the process of removing salt and minerals from seawater or brackish water to make it potable. This is done through thermal distillation (boiling water and condensing the steam) or reverse osmosis (forcing water through semi-permeable membranes under high pressure). It increases freshwater availability in arid coastal regions but requires high energy inputs and is very expensive.

(ii) Rainwater harvesting involves collecting, filtering, and storing rainwater runoff from rooftops, paved surfaces, or catchments before it reaches the ground or drains. The water is stored in tanks or cisterns and can be used for domestic purposes (toilet flushing, gardening, washing) or treated for drinking. It is a low-cost, decentralized method that reduces runoff and soil erosion.

(c) (i) Difference between physical and economic water scarcity:
- Physical water scarcity: Occurs when the demand for water exceeds the available natural water resources in an arid or semi-arid region. There is simply not enough physical water in rivers, lakes, or aquifers due to low rainfall and high evaporation rates.
- Economic water scarcity: Occurs when there is enough physical water available in nature, but there is a lack of financial investment, infrastructure, or institutional capacity to extract, treat, and distribute clean water to the population. People cannot access it because they lack wells, pipes, or treatment plants.

(ii) Impacts of building a large-scale reservoir/dam:
- Economic impacts (Positive): Provides a reliable, year-round water supply for domestic, industrial, and agricultural use; can generate hydroelectric power, which is a renewable energy source; creates opportunities for tourism and recreational activities (boating, fishing).
- Economic impacts (Negative): High capital cost to build and maintain; forces resettlement of local populations with high compensation costs.
- Environmental impacts (Negative): Floods large areas of terrestrial habitats upstream, leading to loss of biodiversity; blocks the natural migration routes of fish and other aquatic species; traps sediment behind the dam wall, reducing nutrient flow downstream and causing downstream riverbed erosion; decomposing flooded vegetation in the reservoir releases greenhouse gases (methane).

(a) (i) Calculate the percentage difference in daily water consumption per person between Country A and Country C. Show your working. [2]
- Award 1 mark for correct working:
\( \frac{450 - 50}{50} \times 100 \) or \( \frac{400}{50} \times 100 \).
- Award 1 mark for the correct answer: 800% (accept 160% if calculated as percentage difference over the average: \( \frac{400}{250} \times 100\% = 160\% \)).

(ii) Suggest three reasons for the large difference in domestic water usage between high-income countries (like Country A) and low-income countries (like Country D). [3]
- Award 1 mark for each valid reason (up to 3):
- Access to piped water inside the house vs collecting water from distance.
- Ownership of water-intensive appliances (dishwashers, washing machines, flushing toilets, baths).
- Use of water for luxury purposes (pools, lawns, washing cars).
- Ability to pay for high water usage (affordability of water bills).
- Differences in public education / awareness of conservation.

(b) (i) Explain how the following processes can be used to increase the availability of fresh water: Desalination [3]
- Award 1 mark for: Removal of salt from saline/ocean water to make it potable.
- Award 1 mark for: Description of method (distillation / boiling and condensing OR reverse osmosis / semi-permeable membrane).
- Award 1 mark for a limitation or detail: Very expensive / energy-intensive / produces salty brine waste that can harm ecosystems.

(ii) Rainwater harvesting [3]
- Award 1 mark for: Collecting rainwater from rooftops / gutters / catchment surfaces.
- Award 1 mark for: Storing the water in tanks / underground cisterns for future use.
- Award 1 mark for: Can be used directly for non-potable domestic tasks (gardening, toilets) or filtered for drinking, reducing reliance on main municipal supply.

(c) (i) Explain the difference between physical water scarcity and economic water scarcity. [4]
- Award up to 2 marks for physical water scarcity:
- Natural lack of water due to dry climate / high evaporation / low rainfall (1).
- Water demand is higher than the physical supply available (1).
- Award up to 2 marks for economic water scarcity:
- Water is physically present in nature, but cannot be accessed (1).
- Caused by lack of money / poor infrastructure / lack of pipes, wells, or treatment facilities (1).

(ii) Discuss the economic and environmental impacts of building a large-scale reservoir/dam to supply water to a major city. [5]
- Award up to 3 marks for economic impacts (must include at least one positive/negative):
- Positive: Reliable water source for city / industry (1); hydroelectricity generation (1); flood control downstream (1).
- Negative: Extremely high construction costs (1); loss of agricultural land / relocation costs for displaced communities (1).
- Award up to 3 marks for environmental impacts (must include at least one negative/positive):
- Negative: Flooding of habitats / loss of biodiversity upstream (1); block migration of fish species (1); retention of nutrient-rich sediment behind the dam (1).
- Positive: Creates wetland habitats for some waterbirds / aquatic species (1).
- Max 5 marks total. Balanced answer must have at least one economic and one environmental point.

(a) To sample birds, researchers can use point counts or line transects. First, map the area and use a random number generator to select coordinates. At each coordinate, stand still for a set period (e.g., 10 minutes) and record all birds seen or heard. (b) Total abundance before logging: \(45 + 30 + 12 + 50 + 18 = 155\). Total abundance after logging: \(15 + 28 + 2 + 48 + 4 = 97\). Total decrease in abundance: \(155 - 97 = 58\). Percentage decrease: \((58 / 155) \times 100 = 37.42\%\). (c) Selective logging targets only mature or specific tree species, leaving the canopy partially intact. This preserves microclimates, maintains soil structure to prevent erosion, leaves seed trees for natural regeneration, and reduces habitat destruction. (d) Governments can share revenues from eco-tourism, provide financial subsidies for sustainable agroforestry, and hire locals as conservation officers or forest rangers. (e) Legal protection: National parks enforce strict bans on hunting and logging, reducing direct human impact. Habitat management: They allow active restoration of degraded areas and provide a continuous corridor of undisturbed habitat for breeding.

(a) [Max 4 marks]: 1 mark for random selection of sampling sites (e.g. using coordinate grids and random numbers). 1 mark for describing the technique (e.g. point count or line transect). 1 mark for standardizing the effort (e.g. fixed time, fixed distance). 1 mark for recording all visual and auditory detections. (b) [Max 4 marks]: 1 mark for calculating correct total before (155). 1 mark for calculating correct total after (97). 1 mark for correct method of calculating percentage change: \(((155 - 97)/155) \times 100\). 1 mark for correct final answer of 37.4% or 37% (accept 37.42%). (c) [Max 4 marks]: 1 mark for preservation of forest canopy/microclimate. 1 mark for preventing widespread soil erosion due to root retention. 1 mark for leaving seed trees for natural regeneration. 1 mark for reduced impact on food webs/habitats. (d) [Max 3 marks]: 1 mark for each valid incentive (e.g. eco-tourism jobs, sustainable agriculture funding, educational programs, ranger salaries). (e) [Max 5 marks]: Up to 2 marks for stating the roles (e.g. legal protection, habitat conservation/restoration). Up to 3 marks for explaining how these roles help species (e.g. bans prevent poaching, large connected areas allow migration and reduce edge effects, research programs help monitor health).

(a) The trend shows a rapid, exponential increase in sulfur dioxide gas emissions over the six-month period, starting at 120 tonnes/day in January and peaking at 2200 tonnes/day in June. This indicates that magma is rising closer to the Earth's surface, releasing dissolved gases as pressure decreases, signaling a high probability of an imminent volcanic eruption. (b) People live near active volcanoes because: 1. Volcanic ash weathers into highly fertile soil (rich in nutrients like potassium and phosphorus) ideal for intensive agriculture. 2. Geothermal energy can be harnessed for cheap, renewable electricity. 3. Volcanic landscapes attract tourists, creating local jobs, and some communities have deep ancestral or cultural ties to the land. (c) 1. Pyroclastic flows: Managed through hazard mapping and establishing strict permanent exclusion zones. 2. Lahars (volcanic mudflows): Managed by building concrete diversion channels, check dams, and installing real-time acoustic flow monitors. (d) HICs typically experience lower loss of life due to early warning systems, strict building codes, and rapid emergency services, but suffer massive economic losses because of high-value infrastructure damage. LICs face much higher casualty rates due to poor infrastructure, lack of evacuation planning, and dense populations, alongside prolonged economic setbacks due to insufficient funds for rapid rebuilding. (e) Tiltmeters are placed on the volcano's slopes to measure tiny changes in the angle (tilt) of the ground, which occurs as magma accumulates and swells the volcano. GPS and satellite technology (like InSAR) monitor wider surface deformation from space and track thermal anomalies or gas plumes, providing early warnings without risking scientists' lives on the ground.

(a) [Max 4 marks]: 1 mark for describing the trend (rapid/exponential increase). 1 mark for citing data (from 120 to 2200 tonnes/day or a calculation of the increase). 1 mark for explaining that magma is rising. 1 mark for stating that pressure release allows more dissolved gas to escape/eruption is imminent. (b) [Max 3 marks]: 1 mark for each valid reason (fertile soils for farming, geothermal energy generation, tourism/employment, mineral extraction, historical/cultural ties). (c) [Max 4 marks]: 1 mark for identifying a hazard and 1 mark for its corresponding mitigation strategy. Repeat for second hazard. (e.g. Pyroclastic flow + exclusion zone/evacuation; Lahar + check dams/channels; Ash fall + provision of masks/roof reinforcement). (d) [Max 5 marks]: 1 mark for comparing death tolls (higher in LICs, lower in HICs). 1 mark for comparing economic damage (higher absolute cost in HICs, higher relative impact on GDP in LICs). 1 mark for role of building regulations/infrastructure quality. 1 mark for emergency preparedness/warning systems. 1 mark for long-term recovery capabilities. (e) [Max 4 marks]: 2 marks for tiltmeters (measuring physical slope/ground angle changes caused by rising magma). 2 marks for satellite/GPS technologies (tracking thermal changes, measuring overall ground displacement/swelling over large areas).

(a) Total decline from Year 1 to Year 5 = \(31\text{ m} - 12\text{ m} = 19\text{ m}\). The time interval between Year 1 and Year 5 is 4 years. Average annual rate of decline = \(19\text{ m} / 4\text{ years} = 4.75\text{ m/year}\). (b) 1. Land subsidence: When water is removed, the sediment compacts, causing the ground above to sink. 2. Saltwater intrusion: Coastal aquifers can be contaminated as seawater seeps in to replace freshwater. 3. Lowering of water tables: Nearby rivers, lakes, and wetlands dry up as they lose groundwater support. (c) Advantages: Dams create reservoirs that store huge volumes of water for dry seasons, generate clean hydroelectric power, and regulate river flow to control downstream flooding. Disadvantages: Reservoirs flood large areas of land, displacing local communities and destroying terrestrial habitats; they block fish migration routes and trap fertile river silt behind the dam wall, reducing downstream soil fertility. (d) Reverse osmosis works by pumping saline water under extremely high pressure through semi-permeable membranes, which allow water molecules to pass but trap salt ions. Environmental challenges include the very high energy demand (often powered by fossil fuels, causing greenhouse gas emissions) and the production of highly concentrated waste brine, which is toxic to marine life when pumped back into the ocean. (e) Urban households can: 1. Install rainwater harvesting tanks to catch roof runoff for watering gardens. 2. Use dual-flush toilets and low-flow showerheads to reduce daily water volume. 3. Recycle greywater from sinks and washing machines to flush toilets.

(a) [Max 3 marks]: 1 mark for correct calculation of total decline (19m). 1 mark for dividing by the correct number of years (4 years). 1 mark for the correct final answer with units (4.75 meters/year or m/yr). (b) [Max 3 marks]: 1 mark for each valid environmental impact (subsidence, saltwater intrusion, drying up of surface water/wetlands, loss of vegetation due to deep water table). (c) [Max 6 marks]: Up to 3 marks for advantages (reliable domestic/agricultural supply, hydroelectric power, flood prevention, recreational opportunities). Up to 3 marks for disadvantages (loss of habitats due to flooding, displacement of human populations, barrier to fish migration, silt build-up behind dam, loss of nutrient flow downstream). (d) [Max 5 marks]: 1 mark for explaining high pressure. 2 marks for describing filtration through semi-permeable membranes (allowing water, blocking salt). 1 mark for high energy requirement/associated air pollution. 1 mark for disposal of concentrated brine harming marine life. (e) [Max 3 marks]: 1 mark for each practical domestic method (e.g. rainwater harvesting, greywater reuse, low-flow aerators, repairing leaks, dual-flush toilets).

(a) Total sample size = 800. The total angle of a pie chart is \(360^{\circ}\). Angle for 'Support': \((520 / 800) \times 360^{\circ} = 234^{\circ}\). Angle for 'Oppose': \((160 / 800) \times 360^{\circ} = 72^{\circ}\). Angle for 'Undecided': \((120 / 800) \times 360^{\circ} = 54^{\circ}\). (b) Environmental benefits: 1. They generate electricity with zero emissions of greenhouse gases or acidic air pollutants. 2. Wind speeds are stronger and more consistent over water, making them highly efficient. Environmental drawbacks: 1. The physical installation disrupts seabed habitats and marine organisms. 2. Underwater noise and vibrations from the turbines can interfere with marine mammal communication and navigation (echolocation). (c) Sulfur dioxide (\(\text{SO}_2\)) is released from burning coal. It reacts with oxygen and water vapor in the atmosphere to form weak sulfuric acid (\(\text{H}_2\text{SO}_4\)), which falls as acid rain. In aquatic ecosystems, acid rain lowers the pH of lakes and rivers. This acidic water causes toxic aluminum ions to leach from surrounding soils into the water, which clogs fish gills and causes them to suffocate, disrupting entire aquatic food webs. (d) 1. Flue-gas desulfurization (scrubbers): Alkaline slurries (like lime) are sprayed into emissions to neutralize and remove sulfur dioxide. 2. Electrostatic precipitators: Use electric charges to attract and capture fly ash and particulate matter before they escape the chimney. (e) Transitioning is challenging because building renewable infrastructure requires massive up-front capital investment that developing nations may lack. Existing national grids are often designed for centralized fossil-fuel power and require expensive upgrades to handle intermittent renewable energy. Socially, closing coal mines and power plants leads to massive job losses, harming local communities dependent on those industries.

(a) [Max 3 marks]: 1 mark for correct calculation of Support (234 degrees). 1 mark for correct calculation of Oppose (72 degrees). 1 mark for correct calculation of Undecided (54 degrees). (b) [Max 4 marks]: 1 mark for each benefit (no greenhouse gases/SO2, higher efficiency, saves land space on shore). 1 mark for each drawback (marine habitat disruption, noise pollution affecting marine life, visual pollution/aesthetic concerns, hazard to migrating birds). (c) [Max 5 marks]: 1 mark for explaining reaction of SO2 with atmospheric water vapor to form sulfuric acid. 1 mark for lowering the pH of water bodies. 1 mark for leaching of aluminum ions from soil/rock into water. 1 mark for aluminum clogging fish gills/causing death. 1 mark for impact on aquatic food webs (e.g. loss of sensitive invertebrate species). (d) [Max 4 marks]: 2 marks for FGD/scrubbers (describing chemical neutralization of sulfur dioxide). 2 marks for electrostatic precipitators (describing charging and collecting particulates) or carbon capture and storage (capturing CO2 and storing it underground). (e) [Max 4 marks]: 1 mark for high capital setup costs. 1 mark for grid unreliability/intermittency challenges. 1 mark for social impacts (job losses in mining/coal communities). 1 mark for lack of local technical expertise/dependence on foreign technology.