Fresh Water Pollution (T4)

Question 1

What are the three main pollutants of fresh water?

Answer 1

• nitrates from fertilisers
• organic waste
• detergents

Question 2

What is eutrophication and what can cause it?

Answer 2

Eutrophication is an increase in mineral ions in lakes and rivers which can occur naturally but also artificially as follows:

• farmers often add inorganic fertilisers to their crops to replace the minerals lost when crops are removed
• the nitrates in these fertilisers are very soluble and so are easily leached from the soils and can enter waterways
• the levels of nitrates and ions can rise rapidly in lakes and rivers which are affected, causing the increase in mineral ions known as eutrophication

Question 3

Describe seven ways in which eutrophication can have disastrous and cumulative effects on waterways…

Answer 3

• as nitrate levels rise, algae are able to use the nitrates to produce extra proteins for growth and rapid reproduction
• the algae then form an algal bloom, preventing light from penetrating further into the water
• submerged plants cannot photosynthesise and so die
• the algae eventually die as they run out of nitrates
• bacteria decay the dead plants and algae, thus releasing more nitrates, and the cycle begins again
• the bacteria reproduce due to the large amount of dead matter, and their respiration uses up more and more oxygen
• the waterway eventually can become completely devoid of oxygen, and all like in the water will die