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Fertilisers and the environment: eutrophication

Eutrophication is the enrichment of an ecosystem with chemical nutrients, normally by compounds that contain nitrogen or phosphorus. Eutrophication is considered a form of pollution because it promotes plant growth, favoring certain species over others. In aquatic environments, the rapid growth of certain types of plants can disrupt the normal functioning of an ecosystem, causing a variety of problems. Human society is impacted as well because eutrophication can decrease the resource value of rivers, lakes, and estuaries making recreational activities less enjoyable. Health-related problems can also occur if eutrophic conditions interfere with the treatment of drinking water.


Eutrophication refers to an increase in chemical nutrients in an ecosystem. These chemical nutrients usually contain nitrogen or phosphorus.

In some cases, eutrophication can be a natural process that occurs very slowly over time. However, it can also be accelerated by certain human activities. Agricultural runoff, when excess fertilisers are washed off fields and into water, and sewage are two of the major causes of eutrophication. There are a number of impacts of eutrophication.

  • A decrease in biodiversity (the number of plant and animal species in an ecosystem) When a system is enriched with nitrogen, plant growth is rapid. When the number of plants increases in an aquatic system, they can block light from reaching deeper. Plants also consume oxygen for respiration, and if the oxygen content of the water decreases too much, this can cause other organisms such as fish to die.
  • Toxicity Sometimes, the plants that flourish during eutrophication can be toxic and may accumulate in the food chain.

Interesting fact

South Africa's Department of Water Affairs and Forestry has a 'National Eutrophication Monitoring Programme' which was set up to monitor eutrophication in impoundments such as dams, where no monitoring was taking place.

Despite the impacts, there are a number of ways of preventing eutrophication from taking place. Cleanup measures can directly remove the excess nutrients such as nitrogen and phosphorus from the water. Creating buffer zones near farms, roads and rivers can also help. These act as filters and cause nutrients and sediments to be deposited there instead of in the aquatic system. Laws relating to the treatment and discharge of sewage can also help to control eutrophication. A final possible intervention is nitrogen testing and modeling . By assessing exactly how much fertiliser is needed by crops and other plants, farmers can make sure that they only apply just enough fertiliser. This means that there is no excess to run off into neighbouring streams during rain. There is also a cost benefit for the farmer.

Discussion : dealing with the consequences of eutrophication

In many cases, the damage from eutrophication is already done. In groups, do the following:

  1. List all the possible consequences of eutrophication that you can think of.
  2. Suggest ways to solve these problems, that arise because of eutrophication.

Chemical industry: fertilisers

Why we need fertilisers

There is likely to be a gap between food production and demand in several parts of the world by 2020. Demand is influenced by population growth and urbanisation, as well as income levels and changes in dietary preferences.

The facts are as follows:

  • There is an increasing world population to feed
  • Most soils in the world used for large-scale, intensive production of crops lack the necessary nutrients for the crops

Conclusion: Fertilisers are needed!

The flow diagram below shows the main steps in the industrial preparation of two important solid fertilisers.

  1. Write down the balanced chemical equation for the formation of the brown gas.
  2. Write down the name of process Y.
  3. Write down the chemical formula of liquid E.
  4. Write down the chemical formulae of fertilisers C and D respectively. The following extract comes from an article on fertilisers: A world without food for its people A world with an environment poisoned through the actions of man Are two contributing factors towards a disaster scenario.
  5. Write down THREE ways in which the use of fertilisers poisons the environment.

Questions & Answers

what is photosynthesis
Sihle Reply
is process whereby green plants to convert light energy into chemical energy.
what is an isomer?
Kiba Reply
organic compounds with the same molecular formula but different structural formula
how is frequency directly proportional to kinetic energy max. and what is the relationship between the wavelength and the energy of a photon. eg if a photon with a greater wavelength and a photon with less frequency. what would be the energies. as in which one would be greater and why
Pearl Reply
relationship wave depend n enrgy greadt reflect of energy n the form of tex shape
what is Cell capacity?
liphelo Reply
what are hydrocarbons
Nyiko Reply
compounds that are made up of hydrogen and carbon only
They are compounds that consist only with hydrogen &carbon elements.
how do i calculate the work done on an object by a frictional force
Emmelda Reply
@ Emmelda it's W = FxCos180 Where 180° is the angle between Frictional force and where the object is going, it's always 180° because it opposes the motion. Then F is the magnitude of the force and x is the displacement
Ohm's law state that provide the temperature remains constant, that potential difference is directly proportional to the current flowing in the circuit
Ezile Reply
state ohms law
what does ohm's law state ?
Gugu Reply
ohm's law state that the potential difference across a conductor is directly proportional to the current in the conductor at constant temperature
ohm'law in metalic conductor is directly proportional to the potential difference provided the temparature
what is the principle on which generator is based
Nqobile Reply
electromagnetic induction
Explain it😌
mechanical​ energy is used to rotate turbines inside the generator where a coil placed between two fixed magnets.as the coil rotates it cuts the magnetic flux due to the magnets. the magnetic flux will then induce an electric current into the coil which will be transmitted to the brushes
may you Please instruct me on how to do Flemmings Right hand dynamo Rule
Fleming's right-hand rule shows the direction of induced current when a conductor attached to a circuit moves in a magnetic field. It can be used to determine the direction of current in a generator's windings
 hold out the right hand with the first finger, second finger and thumb at the right angle to each other.forefinger represents the direction of the line of Force, the thuMb points in the direction of Motion or applied force, then seCond finger points in the direction of the induced Current
what is spectrum
Mpeh Reply
It is a different combinations of frequency of light or any types of waves.
Heii guys what's the topic? Am neww
Vannessa Reply
In nuclear reactions, is it necessary that there must only be one element on the product side and a radioactive particle or you can have a product that are both radioactive particles?
Jobena Reply
conservative force is a force when the work done in moving the object between the two points that does not depend on the path way
Bongiwe Reply
what is conservative force?
Mh Reply
It is a force , that does not have any external features affecting it
what does the alternating current do
Kwanga Reply

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Source:  OpenStax, Siyavula textbooks: grade 12 physical science. OpenStax CNX. Aug 03, 2011 Download for free at http://cnx.org/content/col11244/1.2
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