Pollution is the release of substances or energy that harm the environment. This lesson covers its types and control, and four major issues: the greenhouse effect, acid rain, ozone depletion and eutrophication.
You will calculate a pollutant concentration and a percentage reduction. Answer the questions and collect ⭐.
Types
Types and sources of pollution
Pollution can affect air, water or land.
Point sources come from one identifiable place (a pipe or chimney); non-point (diffuse) sources are spread out (e.g. farm run-off).
Primary pollutants are released directly; secondary pollutants form by reaction in the environment (e.g. ground-level ozone).
Calculate
Your turn — concentration
1A factory discharges 200 g of a pollutant per hour into a river carrying 40 000 L per hour. Calculate the pollutant concentration in mg/L.
mg/L
Hint: 200 g = 200 000 mg. Concentration = 200 000 mg ÷ 40 000 L.
Greenhouse
The greenhouse effect
Greenhouse gases — chiefly carbon dioxide, methane, nitrous oxide and water vapour — absorb outgoing infrared radiation and warm the surface. Human emissions strengthen this natural effect (the enhanced greenhouse effect), driving climate change.
Check
Greenhouse gases
1Which gas is a major greenhouse gas released by burning fossil fuels?
Acid rain
Acid rain and its control
Sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) from burning fuels react with water in the air to form sulfuric and nitric acids, producing acid rain that damages lakes, forests and buildings.
Controls include flue-gas desulfurisation (scrubbers) on power stations and catalytic converters on vehicles.
Calculate
Your turn — emission reduction
2Fitting a scrubber cuts a power station’s SO₂ emissions from 800 tonnes to 120 tonnes per year. Calculate the percentage reduction.
In the stratosphere, ozone shields us from harmful UV. CFCs destroyed stratospheric ozone, creating the ozone hole; the Montreal Protocol (1987) phased CFCs out.
At ground level, ozone is a harmful secondary pollutant in photochemical smog.
Check
Ozone
2CFCs are an environmental problem mainly because they:
Eutrophication
Eutrophication
Excess nitrates and phosphates (from fertiliser run-off or sewage) enrich water and cause an algal bloom. The algae block light, so plants die; decomposers multiply and use up dissolved oxygen, and fish and other organisms suffocate.
Check
Eutrophication
3In eutrophication, why do fish die?
Sort it
Which category?
Sort each item into the correct category.
💨 Air pollution issue
💧 Water pollution issue
🛠️ Control method
Match
Term to meaning
Match each term to its meaning.
Statement
Answer
Recap
The big ideas to know
Types: Air/water/land; point vs diffuse; primary vs secondary