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IB ESS HL 8.3 Urban Air Pollution Questions

Practise IB ESS HL 8.3 by analysing pollutant cycles and evaluating photochemical smog, acid deposition and coordinated urban responses.

Syllabus
First assessment 2026
Course
ESS HL
Level
HL

Exam points

  • Classify primary and secondary pollutants, then use PM2.5/NOx charts to explain urban emission peaks.
  • Trace fuel-combustion NOx/SOx through acid formation to nitric or sulfuric acid.
  • Read acid-deposition maps to link pH patterns with soil leaching, vegetation and freshwater damage.
  • Evaluate activity changes, emission controls or restoration, including international air-quality standards.
  • Explain ozone formation from NOx/VOCs in sunlight and how inversions, weak winds or topography trap smog.
  • Distinguish direct ozone harm to health, crops and materials from indirect healthcare and economic costs.

Covered syllabus points

8.3.1—Urban air pollutants8.3.2—Primary pollutant sources8.3.3—Fossil fuel combustion8.3.4—Management strategies8.3.5—Acid rain formation8.3.6—Acid rain impacts8.3.7—Acid rain management8.3.8 (HL)—Photochemical smog8.3.9 (HL)—Smog intensification factors8.3.10 (HL)—Tropospheric ozone direct impacts8.3.11 (HL)—Tropospheric ozone indirect impacts

Question 1

[Maximum number: 10]
Figure 3: Concentration of atmospheric pollutants associated with photochemical smog

Figure:Concentration of atmospheric pollutants associated with photochemical smog

Question (a)

(a)

Identify one primary pollutant from the pollutants shown in the photochemical-smog pollutant chart shown above.

[ 1 ]

Question (b)

(b)

Outline why the pollutant named in Question 3 (a)(i) is referred to as a primary pollutant.

[ 1 ]

Question (c)

(c)

Outline one reason why there is an increase in nitrogen oxides and hydrocarbons early in the day.

[ 1 ]

Question (d)

(d)

Explain the changes in ozone concentration over the period shown in the photochemical-smog pollutant chart shown above.

[ 3 ]

Question (e)

(e)

State one environmental impact of the accumulation of ozone shown in the photochemical-smog pollutant chart shown above.

[ 1 ]

Question (f)

(f)

Outline two local conditions that may increase the severity of photochemical smog.

[ 2 ]

Question (g)

(g)

Outline the role of catalytic converters in reducing photochemical smog.

[ 1 ]

Question 2

[Maximum number: 9]
Figure 3(a): Average hourly variation in ozone on wet and dry days in Guarujá, Brazil

Figure 3(a): Average hourly variation in ozone on wet and dry days in Guarujá, Brazil

Figure 3(b): Average hourly variation in NOx on wet and dry days in Guarujá, Brazil

Figure 3(b): Average hourly variation in NOx on wet and dry days in Guarujá, Brazil

Figure 3(c): Average hourly variation in SO2 on wet and dry days in Guarujá, Brazil

Figure 3(c): Average hourly variation in SO2 on wet and dry days in Guarujá, Brazil

Question (a)

(a)

Identify the time of day that ozone is at its lowest concentration on a wet day in Figure 3(a).

[ 1 ]

Question (b)

(b)

Outline two reasons for the trend of hourly ozone concentrations shown in Figure 3(a).

[ 2 ]

Question (c)

(c)

Describe one impact of high SO2\mathrm{SO}_{2} concentrations on forest systems.

[ 1 ]

Question (d)

(d)

Outline one possible source of the pollutant shown in Figure 3(b).

[ 1 ]

Question (e)

(e)

Outline why SO2\mathrm{SO}_{2} levels are lower on wet days than on dry days, as shown in Figure 3(c).

[ 1 ]

Question (f)

(f)

Evaluate a strategy to manage the effects of one pollutant named in Figure 3(b) or Figure 3(c).

[ 3 ]

Question 3

[Maximum number: 4]

With reference to named examples, distinguish between a primary and secondary pollutant.

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