13 marks
List three forms of aquatic pollution.
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Water Pollution (SL IB Environmental Systems & Societies (ESS))
Topic Questions
2a1 mark
One parameter that can be measured in order to analyse the quality of a particular aquatic ecosystem is turbidity.
Explain what is meant by the term turbidity.
2b1 mark
Outline how turbidity is measured.
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32 marks
An ecologist collects samples from two different freshwater sources.
Sample A contains stonefly and mayfly nymphs, as well as a few freshwater shrimp, whereas sample B contains a few freshwater shrimp, as well as bloodworms and Tubifex worms. Both samples are found to have the same species richness and species diversity.
i)
Identify which sample contains the more polluted water.
The organisms outlined above helped the ecologist assess the quality of a particular environment (in this case a freshwater environment).
ii)
State the general term used to describe these types of organisms.
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4a2 marks
The boxes below show a number of pollutants and the ways that they affect ecosystems.
Join each pollutant with a straight line to the effect that it creates.
4b1 mark
The figure below shows the positions of four farms and the concentrations of nitrate at different points in a river.
Identify which farm is likely to have been using too much fertiliser on its land.
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17 marks
Explain how a lake affected by eutrophication can be cleaned and restored.
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29 marks
Evaluate the uses of indicator species and biotic indices in measuring aquatic pollution.
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1a5 marks
When raw sewage is released into a waterway it can lead to eutrophication.
The statements below list some of the stages of the process of eutrophication.
i)
Number the statements to put the stages into the correct order.
| Stage of Eutrophication | Order |
| Algal bloom prevents sunlight from reaching aquatic plants. Water oxygen levels fall | |
| Excessive nutrients from fertilisers run-off from the land into the water | |
| Algae also show rapid growth | |
| Death of organisms requiring dissolved oxygen in water | |
| Decomposition rate increases. Aerobic respiration of decomposers reduces dissolved oxygen further | |
| Aquatic plants flourish, growing rapidly |
[3]
ii)
Explain one other potential consequence of the release of raw sewage into a water system.
[2]
1b4 marks
The levels of dissolved oxygen were measured in a river, the results were plotted on a graph, this is shown below.
i)
At which point (A, B, C or D) does raw sewage enter the river?
[1]
ii)
Explain your answer.
[3]
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2a4 marks
Farmers may add chemical fertilisers to their soil to increase crop yield.
These fertilisers may leak into rivers.
A scientist measures the oxygen content of water in two different locations of the same river during the month of April.
In location A he finds that the mean dissolved oxygen was 6 mg per litre and at location B he finds that the mean dissolved oxygen was 3 mg per litre.
He concludes that the use of fertiliser in the field has affected the oxygen content of the river.
Discuss his conclusion.
2b
6 marks
6 marksThe diagram shows a river and the location of a fertiliser factory.
The arrows indicate the direction of the flow of the river.
A scientist recorded the nitrate concentrations of the water at site A and site B. Her results are shown in the table.
| Site |
Nitrate concentration / mg per dm3 |
|||
| Sample 1 | Sample 2 | Sample 3 | Mean | |
| A | 17 | 25 | 18 | 20 |
| B | 49 | 64 | 58 | |
i)
Calculate the mean nitrate concentration found at site B.
[2]
ii)
The scientist observed algae and some dead fish in the river at site B. These were not present at site A.
Give an explanation for these observations.
[4]
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35 marks
i)
Define the term biochemical oxygen demand (BOD).
[2]
ii)
Describe how it is measured.
[3]
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4a1 mark
Define the term eutrophication.
4b3 marks
Eutrophication is an example of positive feedback.
Explain how.
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