Topic 10: Pollution Of Water

Question 1

The water cycle is a natural purification process. How?

Answer 1

When water falls/precipitates it flows into the sea containing dissolved and suspended materials including pollutants with it
When water evaporates as water vapour, it is pure, which leaves the pollutants behind so they may become more concentrated

Question 2

What factors affect the dilution of pollutants in water?

Answer 2

Effluent quantity
Volume of water
Residence time of water

Question 3

Effluent quantity
How does this affect the dilution of a pollutant in water?

Answer 3

The amount of pollution affects the concentration
If the concentration is low, many pollutants aren’t harmful

Question 4

Volume of water
How does this affect dilution?

Answer 4

The larger the body of water, the more waste will be diluted

Question 5

Residence time of the water
How does this affect the dilution of pollutants?

Answer 5

The shorter the residence time of water, the more likely a pollutant will be carried away by flowing water and not accumulate

Question 6

What is degradation?

Answer 6

The process by which substances are broken down
Involves both biotic and abiotic processes

Question 7

Name 3 factors that can determine the rate of degradation

Answer 7

High levels of sunlight or UV
Dissolved oxygen
Higher temperatures

Question 8

How do high levels of sunlight/UV affect the rate of degradation?

Answer 8

They may cause photo degradation

Question 9

how does dissolved oxygen affect the rate of degradation?

Answer 9

Increased the rate at which aerobic bacteria break down sewage

Question 10

How do higher temperatures affect the rate of degradation

Answer 10

Increase the rat of most reactions

Question 11

How does the removal rate affect the concentration of pollutants in water?

Answer 11

They are less of a problem if they become part of the sediment because that removes them from the water
E.g. phosphates and pesticides can be absorbed onto sediment particles

Question 12

How does dispersal affect the concentration of pollutants in water?

Answer 12

Currents will disperse pollutants in water so they are more diluted, this can reduce harmful effects
However if the pollutants persist and dont biodegrade, they can become more concentrated over time and cause more problems

Question 13

Give an example of a polluted water body, and the cause of the pollution

Answer 13

River Ganges
Areas with large human populations