Environmental Sustainability, practice questions

B, Sulfur dioxide dissolves in atmospheric moisture to form dilute sulfuric acid, which falls as acid rain.

C, Extra greenhouse gases released by human activities trap more heat, intensifying the natural greenhouse effect.

B, A high BOD means microorganisms are using a lot of oxygen to decompose organic matter, indicating heavy organic pollution.

C, Preservation keeps an area of nature completely untouched by human use.

C, CFCs release chlorine atoms in the stratosphere that break down ozone molecules.

C, Eutrophication begins when excess nutrients, often from fertiliser runoff or sewage, enter a body of water.

C, Restoration actively repairs an ecosystem that has already been damaged.

D, Sustainable development balances economic, social and environmental considerations, not political popularity.

B, An EIA is carried out before a development project is approved so its likely effects can be identified in advance.

D, Solar power uses photovoltaic cells to convert sunlight directly into electricity.

• (a) Factory B's discharge likely raised the BOD of the river between Town A and Town C, using up dissolved oxygen that the fish near Town C needed to survive.
• BOD measures the oxygen used by microorganisms breaking down organic matter, so a higher organic pollution load leaves less oxygen for aquatic life.
• (b) Taking BOD readings upstream of Factory B, near Town A, and downstream of it, near Town C, and comparing the two values would show whether BOD rises sharply after the discharge point.
• A much higher downstream BOD value would support Factory B as the source of the extra organic pollution.
• (c) The factory could treat its wastewater to remove organic matter before discharging it into the river.
• This would lower the BOD of the discharge and reduce the amount of oxygen consumed by microorganisms downstream, protecting aquatic life such as the fish near Town C.

• (a) The assessment identifies the project's likely effects on the surrounding environment before it is approved, so mitigation steps can be planned rather than approving the project without considering its consequences.
• (b) Clearing forest on the hillside could increase soil erosion, since fewer plant roots would hold the soil in place.
• The cleared hillside could also increase the risk of sediment or runoff entering the nearby river, potentially raising its BOD or disturbing aquatic habitats.
• (c) A buffer zone of retained vegetation could be left along the riverbank to filter runoff before it reaches the water.
• Alternatively, a terracing or drainage system could be built to slow water flow down the slope and reduce soil erosion.
• These conditions could be attached to the project's approval to reduce its overall environmental impact.

• (a) Solar and wind power generate electricity without burning fuel, so they release no carbon dioxide, sulfur dioxide or particulate matter during operation, unlike a coal-fired plant.
• This means switching to them would reduce the country's contribution to global warming and acid rain.
• (b) Solar power output depends on sunlight availability and wind power output depends on wind speed, so neither can provide a constant electricity supply at all times.
• (c) Combining renewable sources such as solar, wind and hydroelectric power means that when one source is unavailable, for example solar power at night, another may still be generating electricity.
• A mixed supply is therefore more reliable than depending on a single renewable source alone.
• This balances the environmental benefit of reducing fossil fuel use with the practical need for a dependable electricity supply.

Human activities such as burning fossil fuels, deforestation and improper waste disposal cause air, water and land pollution, alongside a rise in greenhouse gases that drives global warming. Each threat has a distinct cause, so an exam answer should name a specific activity and its specific effect rather than describing pollution in general terms. Open burning and vehicle exhaust, for example, are two separate sources of air pollution with different pollutants and different control measures.

Greenhouse gases such as carbon dioxide and methane trap heat in the atmosphere that would otherwise escape into space, a natural effect that keeps Earth warm enough for life. Human activities release extra greenhouse gases, trapping more heat and raising the average global temperature, which is global warming.

BOD measures how much oxygen microorganisms use to break down the organic matter in a water sample over a set time. A high BOD value means the water contains a lot of organic pollution, since more oxygen is used up, leaving less available for fish and other aquatic organisms. Comparing BOD values upstream and downstream of a discharge point is a common way to judge how much a specific source has polluted a river.

Preservation protects an area of nature and keeps it untouched by human use, such as a strict nature reserve. Conservation manages the wise, sustainable use of a resource so it is not exhausted, such as controlled fishing. Restoration actively repairs an ecosystem that has already been damaged, such as replanting a cleared forest.

Green technology reduces environmental harm compared with older methods, including renewable energy, recycling processes and cleaner production methods that release less pollution. Choosing a green technology usually involves weighing its environmental benefit against its cost and how practical it is to adopt widely. An electric vehicle, for example, produces no exhaust emissions itself, though the source of the electricity used to charge it also matters.

Sustainable development meets the needs of people today without reducing the ability of future generations to meet their own needs. It balances economic growth, social wellbeing and environmental protection together rather than treating environmental protection as separate from development. Planting a fast-growing replacement crop for every tree logged in a plantation forest is one practical example of this balance.

The ozone layer in the upper atmosphere absorbs most of the sun's harmful ultraviolet (UV) radiation. Chemicals such as chlorofluorocarbons (CFCs), once common in aerosols and refrigerants, break down ozone molecules, thinning this layer and allowing more UV radiation to reach the Earth's surface, which raises the risk of skin damage and harm to some crops.

Eutrophication begins when excess nutrients, often from fertiliser runoff or untreated sewage, enter a body of water and cause algae to grow rapidly, forming a dense bloom. When the algae die, decomposers use up large amounts of dissolved oxygen breaking them down, which can leave too little oxygen for fish and other aquatic life.

Renewable energy sources, such as solar, wind and hydroelectric power, generate electricity without burning fossil fuels, which reduces the greenhouse gases released compared with coal or oil power plants. Adopting them at a larger scale usually requires weighing the upfront cost of infrastructure against the long-term reduction in emissions.

An Environmental Impact Assessment is a formal study carried out before a development project, such as a new highway or factory, is approved. It identifies the project's likely effects on the surrounding environment so that mitigation steps can be planned, rather than approving a project without considering its environmental consequences.