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Question 20N.3.HL.TZ0.19

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Date November 2020 Marks available [Maximum mark: 6] Reference code 20N.3.HL.TZ0.19
Level HL Paper 3 Time zone TZ0
Command term Suggest Question number 19 Adapted from N/A
19.
[Maximum mark: 6]
20N.3.HL.TZ0.19

Suggest how nitrogen and phosphate cycles can be disrupted by humans or extreme weather events.

[6]

Markscheme

a. excess rains/floods/irrigation can wash away nutrients/N/P by leaching;

b. excess rains/floods/irrigation can lead to waterlogged soils;

c. waterlogging leads to denitrification due to anaerobic conditions;

d. nutrients are added to the cycles by application of fertilizer;

e. nutrients are removed by the harvesting of agricultural crops;

Nitrogen:
f. lightning increases N in soil;

g. planting legumes increases N in soil;

Phosphate:
h. mining of P speeds up the P cycle/depletes P reserves;

i. phosphorus is added to waters in detergents;

j. phosphorus is mined/taken from rocks for making detergents/fertilizers;

Examiners report

Only the strongest candidates could focus on human impact and extreme weather events for this question, as most provided unorganized answers relating to knowledge addressed in previous papers about nutrient cycles in general, limited phosphate availability, pollution, global warming or eutrophication; some even mentioned earthquakes and volcanoes, which may be catastrophic, but are not weather events.

Syllabus sections