| Date | November 2017 | Marks available | 1 | Reference code | 17N.2.SL.TZ0.3 |
| Level | Standard Level | Paper | Paper 2 | Time zone | Time zone 0 |
| Command term | Identify | Question number | 3 | Adapted from | N/A |
Question
Figure 5: A layer of smog covering the Chilean city of Santiago
[Source: CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=428144]
Identify one human factor that contributes to photochemical smog.
Identify one natural factor that contributes to photochemical smog.
Explain why the formation of photochemical smog may have harmful effects on the environment of cities such as Santiago (Chile).
Markscheme
(intensive) combustion of fossil fuels/organic matter/through high density traffic/urbanisation/industrialisation/forest burning/release of VOCs from aerosols;
local topography/high insolation/sunlight/low wind/thermal inversion;
reduced growth and productivity of plants/reduces crop yields by damaging them;
leads to the reduction of the air quality/visibility/ambience within the urban area;
particulates/chemicals within the smog enter the lungs and irritate respiratory system/cause respiratory disease/lung cancer;
particulates/chemicals within the smog may cause irritation of eyes/eye diseases;
the chemicals within the smog react with plastic/rubber causing it to perish/become hard/inflexible;
tropospheric ozone (a secondary pollutant) is a greenhouse gas/contributes to global warming/climate change;
smog pollutants reduce immune system of humans and animals (become more susceptible to diseases);
Award [1] for each correct explanation, up to [4 max].
Examiners report
Most were able to identify a valid human factor contributing to photochemical smog, though a good number mistakenly identified CO2 from fossil fuels.
A slim majority were able to identify one natural factor.
Vast majority were able to identify at least one impact of smog but very few identified four for full credit.
Syllabus sections
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19M.2.SL.TZ0.3b:
State two factors necessary for the chemical formation of ozone in the troposphere.
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19N.2.SL.TZ0.5a:
Outline, using examples, the differences between primary and secondary pollution.
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14M.2.SL.TZ0.5a:
Outline the conditions and processes that lead to the formation of photochemical smog.
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19N.2.SL.TZ0.5c:
To what extent is pollution impacting human food production systems?
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19M.2.SL.TZ0.3d:
Suggest possible reasons for the overall trends of tropospheric ozone levels in Figure 3.
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17N.2.SL.TZ0.3b:
Explain why the formation of photochemical smog may have harmful effects on the environment of cities such as Santiago (Chile).
- 17N.2.SL.TZ0.3a.ii: Identify one natural factor that contributes to photochemical smog.
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18M.2.SL.TZ0.4c:
Disturbance of the composition and processes of the atmospheric system through human activity always disturbs the equilibria of marine systems.
Discuss the validity of this statement with reference to named examples.
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19M.2.SL.TZ0.3c:
Outline why a high concentration of ozone in the troposphere is a direct problem for humans, while in the stratosphere it is a benefit to humans.
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18M.2.SL.TZ0.6a:
With reference to named examples, distinguish between a primary and secondary pollutant.
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19M.2.SL.TZ0.3a:
With reference to Figure 3, calculate the difference between the highest concentration and lowest concentration of tropospheric ozone.
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18N.2.SL.TZ0.7b:
Urban air pollution can become a problem as human populations develop. Evaluate urban air pollution management strategies at the three levels of intervention.
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15N.1.SL.TZ0.5b.ii:
Evaluate one management strategy for urban air pollution.
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15N.1.SL.TZ0.5b.i:
Describe the formation of tropospheric ozone.
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16M.1.SL.TZ0.6a:
Human activities affect the concentration of both stratospheric and tropospheric ozone.
Outline the differences in these two effects by completing the following table.
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17M.2.SL.TZ0.7b:
Explain how changes in the concentration of stratospheric and tropospheric ozone in the atmosphere can affect global biodiversity.
