49 exam-style questions on Urban air pollution — topic 8.3 of Human populations and urban systems in the IB Environmental Systems and Societies syllabus — with answers and explanations. Samples below; the full set is free with an account.
Which of these urban air pollutants is a secondary pollutant?
Answer: Peroxyacetyl nitrate produced in sunlit polluted city air
A secondary pollutant is never emitted directly but forms in the atmosphere from reactions between primary pollutants. Peroxyacetyl nitrate and tropospheric ozone both appear only after nitrogen oxides react with volatile organic compounds in sunlight.
A city lying in a mountain basin records its worst photochemical smog episodes under which combination of conditions?
Answer: Clear sunny skies, light winds and a temperature inversion
The reactions that produce ozone and PAN are driven by ultraviolet light, and an inversion with light winds stops the products dispersing, so pollutants accumulate over the basin instead of being ventilated away.
A city funds a new tram network so that residents make fewer car journeys in the first place. In the pollution management model this measure operates at the level of
Answer: altering the human activity that produces the pollutant
Level 1 changes the activity itself, level 2 controls emissions once the activity is happening through devices such as catalytic converters, and level 3 treats the damage after release. Earlier levels are cheaper and more effective but depend on behaviour change.
A three-way catalytic converter fitted to a petrol car reduces which combination of pollutants?
Answer: Carbon monoxide, nitrogen oxides and unburnt hydrocarbons
The converter oxidises carbon monoxide and unburnt fuel and reduces nitrogen oxides, which is why it is called three-way. It does nothing about carbon dioxide, since that is the intended product of complete combustion, and this is why a converter improves local air quality without helping the climate.
The London smog of December 1952 caused thousands of deaths within a few weeks. Its essential ingredients were
Answer: smoke and sulfur dioxide from coal, trapped by a temperature inversion
This was industrial or sulfurous smog, the cold-weather type produced by burning coal in homes and power stations while calm anticyclonic conditions and an inversion prevented dispersal. It is the opposite case to photochemical smog, which needs sunshine and traffic emissions, and it led directly to the smoke control areas of the Clean Air Act.
Air quality standards regulate fine particulate matter more strictly than coarse particulate matter because the finer particles
Answer: penetrate deep into the lungs and pass into the bloodstream
Coarse particles are largely filtered out in the nose and upper airways, whereas particles below about 2.5 micrometres reach the alveoli and cross into the circulation, which is why the health evidence links them to heart disease and stroke as well as to lung conditions.
That was 6 of 49 Urban air pollution questions.
Practise all 49 freeOutlineAO2 · 1–4 marks
A brief account or summary: the main points in two or three sentences, no evaluation.
DrawAO1 · 1–2 marks
A labelled, accurate drawing with a ruler where lines are straight; axes and units on a graph.
DistinguishAO2 · 1–4 marks
Make the difference clear for BOTH terms — a definition of one of them is only half an answer.
49 Urban air pollution questions — free with an account. Spaced repetition, streaks and full exam simulations included.
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