Everything Science Grade 12

CHAPTER 5. THE CHEMICAL INDUSTRY 5.4

3Ca 3 (PO 4 ) 2 ·CaF 2 + 12H 3 PO 4 → 9Ca(H 2 PO 4 ) 2 + 3CaF 2

3. Potassium
   Potassium is obtained from potash, an impure form of potassium carbonate (K 2 CO 3 ).
   Other potassium salts (e.g. KCl and K 2 O) are also sometimes included in fertilis-
   ers.

Fertilisers and the Environment:

Eutrophication

ESCCP

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

DEFINITION: Eutrophication

Eutrophication refers toan increase in chemicalnutrients in an ecosys-

tem. 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 canalso be accelerated bycertain 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 anumber of impacts of eutrophication.

• A decrease in biodiversity (the number of plant and animal species inan ecosys-
  tem)
  When a system is enriched with nitrogen, plant growth is rapid. When the num-
  ber 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 toomuch, this can cause other organisms such as fishto die.


• Toxicity
  Sometimes, the plants that flourish during eutrophication can be toxic and may
  accumulate in the foodchain.

FACT

South Africa’s Depart-

ment 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 waysof preventing eutrophication from tak-
ing place. Cleanup measures can directly remove theexcess nutrients such asnitrogen
and phosphorus from the water. Creating buffer zones near farms, roads and rivers can
also help. These act asfilters and cause nutrients and sediments to be deposited there