Changes to Ecosystems (iv) Pollution
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What is pollution?
Pollution is the negative effect of a harmful substance on the environment
What are non-toxic pollutants?
These are pollutants which are indirectly harmful.
Give an example of a non-toxic organic pollutant
Give an example of a non-toxic inorganic pollutant
If excessive nutrients get into a water supply then a into a loch/pond/river we say it is...?
What are the ways of measuring organic pollution?
- Indicator species
- BOD (Biological oxygen demand)
What is the biological oxygen demand and how is it measured?
- The BOD test is a water quality test that measures the levels of dissolved oxygen in the water. It is used to estimate the levels of biodegradable organic material there is.
- To measure the BOD:
- Two samples of water are taken (no air in bottles)
- Dissolved oxygen concentration is measured
- One sample is put in the dark (to prevent algae photosynthesising)
- Water is incubated at 20°C for 5 days and DO remeasured
- The mass of O2 used per litre is calculated. This reflects the mass of organic material available for bacterial decomposition. The more oxygen used (the more demand) the more polluted the water
What are toxic pollutants? Give examples
- Toxic pollutants are directly harmful to the health of the organism
- Examples include:
- Pesticides eg TBT and DDT
- Heavy metals eg mercury, cadmium, chromium and lead
- Radioactive waste
What is bioaccumulation?
When a toxin is retained in the bdoy and therefore ends up at a higher concentration in the body than the environment
What is biomagnification?
When a toxin increases in concentration further up the food chain as it accumulates at each level
What is biotransformation?
When a toxin changes in the body into another toxin
Why is mercury a nasty toxic pollutant?
- It is persistant
- It bioaccumulates
- It biomagnifies in a food chain
- It is an irreversible non competitive inhibitor of enzymes and can affect nervous tissue and foetal development
- Can biotransform into toxic methyl mercury
Why is lead a nasty toxic pollutant?
It can bioaccumulate which can lead to lead poisoning and can affect the mental development of young children
What is DDT and why is it a nasty toxic pollutant?
- It is a pesticide that interferes with nerve impulses in insects.
- It is non-specific and persistant with a long hal-life.
- It bioaccumulates in fatty tissues and therefore biomagnifies in food chains
- DDT can biotransform into DDE
- Both DDT and DDE reduce calcium deposition during egg formation. This resulted in birds of prey such as osprey and peregines reducing in number (the eggs broke when parents were nesting on them)
What is TBT and why is it a nasty toxic pollutant?
- TBT is an antifouling agent used on boats to stop baracles growing on them
- TBT is therefore harmful to some marine organisms, including dog whelks. TBT causes female dog whelks to develop male sexual characteristics such as a penis. This causes them to become infertile or die
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