Pollution - events and processes that do harm to the planet, especially living organisms.
Usually caused by human activities but similar effects can be caused by natural events such as volcanic etuptions, natural oil leakage or forest fires.
Human activities that cause pollution:
- extracting resources, e.g. mining
- using resources, e.g. fuel combustion (burning fuels)
- manufacturing, e.g. fuel combustion to power factory machinery
- disposal of unwanted, worn out or unnecessary goods, e.g. domestic waste
- food production, e.g. pesticides & fertilisers
Factors that affect the behaviour of pollutants in the environment:
- mobility - how and where they travel
- state of matter - solid/liquid/gas
- chemical form - organic/inorganic compound
- timescale of action
- what they affect - living organisms, non-living
- direct or indirect action
The behaviour of the pollutants are controlled by the properties of the pollutants and the features of the environment into which they are released. This means that the same pollutant may have very different effects if released in to two different locations.
The properties of pollutants
The major properties
Toxicity - the measure of how poisonous a material is. It harms the biological process that takes place within a living organism. This is done by damaging proteins, especially enzymes that control biological reactions.
e.g. Carbon monoxide binds to haemoglobin in the blood and prevents it carrying oxygen.
Specificity - measure of the differing toxicity of a substance to different types of organisms. Different organisms have different sensitivities to toxic substances, so a particular toxic substance could be very harmful to one organism, but less harmful to another.
e.g. pyrethoid insecticides will kill both insects and mammals but insects are more sensitive than mammals. Therefore farmers use a dose thats sufficient to kill insects but not the malmmals. Pyrethoids are specific toxins for insects.
Persistence - the measure of how long it takes for a pollutant to chemically break down. Many pollutants are compounds which have many different elements combined together. A variety of chemical, biological or physical processes may change the compounds so that they can't cause harm and are therefore not pollutants. Persistance is a measure of the length of time that a pollutant remains in the environment and can therefore cause harm.
This term is usually only applied to substances that will eventually break down, if they can't as they are too stable they would be described as non-degradable.
Persistant pollutants = CFCs which are chemically stable and break down slowly. They may remain in the atmosphere for many decades.
Non persistance pollutants = Sewage breaks down quickly if the conditions are right (warm, plenty of oxygen) for the bacteria.
Biodegradability - (degradation - process of chemical breakdown) Biodegradation is the process of being broken down by biological processes (decomposers-fungi/bacteria) The rate of biodegradation is affected by environmental factors such as temperature and oxygen availability.
Biodegradable pollutants - sewage, paper
Less biodegradable pollutants - most plastics, DDT
Mobility - measure of how easily a material moves in the environment. Pollutants that are more mobile and likely to travel…