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Date May 2014 Marks available 4 Reference code 14M.2.SL.TZ0.5
Level Standard Level Paper Paper 2 Time zone Time zone 0
Command term Outline Question number 5 Adapted from N/A

Question

Outline the conditions and processes that lead to the formation of photochemical smog.

[4]
a.

Evaluate the use of biotic indices compared with direct methods of measuring pollution.

[6]
b.

Pollution management strategies may be applied at any of the three levels identified in the diagram below:

With reference to acid deposition, evaluate the political and economic advantages of applying management strategies at the levels of production and impact of the pollutant.

[8]
c.

Markscheme

 

Conditions for photochemical smog [2 max]:
local topography/valleys/lack of wind reducing dispersal of pollutants;
temperature inversion;
high population density/fossil fuel use/traffic density;
high amounts/intensity of solar radiation / sunny;

Processes forming photochemical smog [3 max]:
largely photochemical reactions / reactions increased by sunlight;
use of fossil fuels releases hydrocarbons through evaporation / nitrogen oxide/NO through combustion;
emission of suspended particles catalyse photochemical reactions;
NO reacts with oxygen to form NO2;
Sunlight promotes the formation of O atoms from NO2;
… that combine with O2 to form ozone (the main secondary pollutant in photochemical smog);
hydrocarbons react with NO2, O2 and light to form aldehydes & PAN;

 

[4 max]

a.

 

Award 1 max for distinguishing biotic indices and direct methods.
biotic indices measure the quality of ecosystem rather than quantity of pollutant / biotic indices are dependent on the tolerance/diversity/abundance of organisms, not concentration/toxicity/identity of pollutant;

They are advantageous in that:
they measure the widespread effects/impacts of pollutants on the system;
…which is more significant than the quantity/concentration/nature of the pollutant;
they are specific to the characteristics of a given habitat;
they will address the combined/integrated impact of many pollutants/human activities;
Avoids use of expensive instrumentation;

They are disadvantageous in that:
they do not identify the specific pollutants;
… leaving the possible source of pollution unclear;
the quality of a given community may vary for reasons other than pollution / initial quality may not be known;
may require counting/identification of organisms which are difficult to collect/identify (eg lichen, invertebrates) / prone to human error;

 

Award [4 max] for responses that give only advantages, or only disadvantages.

[6 max]

b.

 

Level of “producing”. Award [1 max] for outlining such management: relevant to acid rain:
Eg management can be applied at level of producing by reducing use of fossil fuels/ switching to alternative energy sources;

political advantages/disadvantages:
it may not be popular to impose limits on use of fossil fuels in certain societies;
but it does address root cause of problem;
and political factors have the advantage of generating laws/incentives;
in democratic societies such management may have strong influence on voting/political support;
may gain international support for an issue that often crosses national boundaries;

economic advantages/disadvantages:
it may be very costly to switch to alternative energy sources;
could be long-term economic benefit in this for countries importing fuel;
would be economically beneficial in context of international C-trading;
may gain volunteer support from community/NGOs that make management more cost effective;

Level of “impact”. Award [1 max] for outlining such management:
Eg. management can be applied at level of impact by liming of water bodies/restoration of natural communities;

political advantages/disadvantages:
it may be popular because it allows use of fossil fuels to continue;
and restores aesthetic qualities of environment;
but may conflict with the increasing “green”/ecocentric sector of many societies;

economic advantages/disadvantages:
avoids cost of switching from fossil fuel technologies;
liming and restoration may be very costly;
could be mitigating benefits eg sustainable goods/services of restored systems;
provides for environmental projects attractive to local community/NGO voluntary support;

 

Alternative points of equivalent validity, significance and relevance to those given, should be credited.

Award [5 max] for responses that address only one level of management, or only political, or only economic, factors.

[8 max]

Expression of ideas: [2 max]

c.

Examiners report

Generally mediocre. Most candidates were able to make one or two specific points, but rarely more.

a.

Generally weak. While most candidates gave a thorough description of biotic indices with examples, few addressed the key focus of the question that was a comparative evaluation with direct methods.

b.

Generally OK, but responses were very mixed in quality. Those candidates that clearly referred to a management strategy relevant to acid deposition at each of the required levels usually went on to give clear political/economic advantages. Those that floundered at this first step, however, often gained very little further credit.

c.

Syllabus sections

Topic 6: Atmospheric systems and societies » 6.3 Photochemical smog
Topic 6: Atmospheric systems and societies

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