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Date November 2019 Marks available 1 Reference code 19N.3.HL.TZ0.1
Level Higher level Paper Paper 3 Time zone TZ0 / no time zone
Command term Suggest Question number 1 Adapted from N/A

Question

Scientists have constructed systems to reproduce the conditions of natural wetlands. The mesocosms below were used to study nutrient removal from water flowing through.

[Source: © 2013. Silviya Lavrova and Bogdana Koumanova (October 2nd 2013). Nutrients and Organic Matter Removal in a
Vertical-Flow Constructed Wetland, Applied Bioremediation – Active and Passive Approaches, Yogesh B. Patil and
Prakash Rao, IntechOpen, DOI: 10.5772/56245. Available from: https://www.intechopen.com/books/applied-bioremediationactive-
and-passive-approaches/nutrients-and-organic-matter-removal-in-a-vertical-flow-constructed-wetland]

Compare and contrast the design of both mesocosms (vertical flow and horizontal flow).

[2]
a.

Suggest with a reason which system best reproduces the conditions of the natural environment.

[1]
b.

State two variables other than temperature and light that should be controlled in this experiment, in order to discover which system is more effective at removing nutrients from water.

[2]
c.

Markscheme

Similarities [1 max]
a. both have similar design «input and output» ✔

b. both open systems ✔

Differences [1 max]
c. vertical flow/«figure» A has pump but horizontal flow/«figure» B does not/flows naturally ✔ Do not accept references to rate of flow or pressure as they are unknown.

d. horizontal flow/«figure» B has a larger «surface» area
OR
horizontal flow/«figure» B has more plants ✔ Accept vice versa.

e. vertical flow/«figure» A has a pre-treatment «with sedimentation tank» before treatment but not horizontal flow/«figure» B ✔ Accept vice versa.

a.

a. horizontal flow/«figure» B because it is larger
OR
horizontal flow/«figure» B contains more/several plants ✔

b. horizontal flow/«figure» B because it works by natural flow
OR
horizontal flow/«figure» B because it works without a pump ✔ Do not accept river instead of flow.

b.

a. type/number of plants ✔

b. type of soil/substrate ✔

c. pH level ✔

d. initial concentration of nutrients ✔

e. timespan of experiment ✔

f. volume of water/influent
OR
flow rate ✔ Do not accept amount instead of volume.

If more than two variables written, mark only the first two.

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Core » Topic 4: Ecology » 4.1 Species, communities and ecosystems
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Core » Topic 4: Ecology
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