Unit 2: Water pollution

Topic & Major Objective

Subject Content

Knowledge expected

Water Pollution

The main bodies of water to be included here are:

a) The oceans

b) Subsurface water

c) Coastal waters

d) Lakes & rivers

e) Enclosed & semi-enclosed seas

Candidates are expected to know examples of water pollutants and how these end up in the sinks mentioned. Particular attention should be given to the pollution of subsurface and coastal waters as the final sinks for pollutants. (To the pollutants originating at sea land pollutants must be added due to run-off).

General properties and dynamics of water pollutants:

a) Dispersal

b) Biodegradation

c) Photodegradation

d) Size of emissions

e) Volume of water considered

f) Residence time of water/pollutant

The relative mobility of pollutants in water and factors influencing their concentration and durability in the water column.

Specific water pollution issues

Thermal pollution:

a) Ecological consequences

b) Temperature dependence of gas solubility in water

c) Increased rates of chemical reactions at higher temperature

Candidates are expected to become aware of how thermal pollution alters the habitats’ physical conditions thus disturbing natural systems. The discussion should be purely qualitative.The use of cooling towers to lower water temperature should be briefly discussed.

Acid drainage, mines and acid rain:

a) Tolerance range of organisms to pH

b) Increased solubility of heavy metals at low pH

c) Use of pumps, and the addition of lime to contain the problem

Candidates are expected to become aware of how acidity disrupts natural systems. Candidates should also become aware of at least one technique of how to reduce acidity in water bodies.

Heavy metal pollution:

a) Biomagnification via food chains.

b) Small tolerance range of most organisms to heavy metals.

c) Acid water due to release of acidic compounds from waste, slag and piping.

d) Bioaccumulation to toxic levels e.g. physiological effects of mercury and lead

e) Control of pH to reduce solubility of the metals.

Candidates are expected to be able to understand the consequences of heavy metal pollution, the issues of biomagnification and bioaccumulation being so important due to their multiplying effect up food chains and food webs.Candidates are expected to be able to handle a quantitative treatment of these issues.

The metals to be treated here are: Zinc, Lead, Copper, Arsenic, Mercury and Cadmium.

Nitrate, phosphate and organic pollution:

a) Ground water nitrate pollution

b) Biological, pathogenic organisms contamination

c) Eutrophication, algal blooms and problems of toxin release

d) BOD & COD, oxygen sag

Candidates are expected to understand the importance of ground water, that it may also be polluted and that its recovery from pollution can be a very slow process.

Candidates should be aware of the importance of clean water and that water is an excellent vector and host for some of the most dangerous pathogenic agents on Earth.

A discussion about one major human disease caused by contaminated water.