Download Eutrophication – Biology or Chemistry

Eutrophication for a
Biology class/Chemistry
class.
Unit 1.4.9 of biology
syllabus
and
Section 9.3 of chemistry
syllabus.
Eutrophication.
Definition of Eutrophication.
• Eutrophication is the addition of
nutrients to water which results in
excessive growth of algae. (Algal
bloom)
• The nutrients are phosphates (PO43-)
and nitrates (NO3-).
• When the algae die, their breakdown by
aerobic bacteria results in
deoxygenation (removal of dissolved
O2 from the water)
• Oxygen loss results in the death of fish.
Eutrophication
Natural
Artificial
Natural Eutrophication.
• Natural eutrophication occurs when
nitrates and phosphate are added,
slowly and over long periods of time, to
rivers and lakes.
Artificial Eutrophication
•
•
•
•
•
Happens much faster than natural.
Is a result of human activity.
Is caused by untreated sewage.
Detergents that are high in phosphates.
Is also caused by fertilisers being
leached from farms into lakes.
• Nitrates and phosphates are present in
these pollutants.
Some Questions.
• Q. What is a form of water pollution that
causes an algal bloom in the water?
• A. Eutrophication.
• Q. Identify ions which are responsible for
eutrophication.
• A. Nitrates (NO3-) and phosphates (PO43-).
• Q. Name any pollutant that contains either of
these ions.
• A. Untreated sewage or fertilisers.
Some revision questions for
chemistry.
• Q. What is the name giving to the test
for the nitrate anion?
• A. The brown ring test.
• Q. When testing for the phosphate ion
in aqueous solution, what is the colour
of the positive result?
• A. Yellow.
• Q. At what stage of sewage treatment
are nitrate and phosphate ions
removed?
• A. Tertiary.
Some revision questions for
biology.
• Q. Define pollution.
• A. Pollution is the addition of harmful
material to the natural environment,
usually as a result of human activity.
• Q. Name any one water pollutant.
• A. Untreated sewage or slurry from
farms.
• Q. How may either of these forms of
pollution be controlled?
• A. Sewage is treated in modern
treatment plants before its discharge
into a river or lake.
Some revision questions for
biology.
• Q. How may pollution caused by slurry
run off from farms be controlled?
• The slurry is stored in leak proof pits
until there are dry weather conditions.
It is spread onto fields where it is less
likely to be leached by rain.
• The slurry is broken down and
nutrients recycled back into the soil.
Describe the ecological impact of
the addition of fertilisers or farm
slurry to a river or lake.
• Excessive amounts of nitrates and phosphates
are added.
• Massive growth in algae.
• Less light reaching plants living at deeper levels
in the lake.
• Aerobic bacteria remove dissolved oxygen as
they break down the algae.
• Many species of fish die.
• Coarse fish can survive and their numbers
increase to levels where they should not be.
• An imbalance in fish and plant numbers results.