1.4.9 Human Impact on an Ecosystem 1
Pollution
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Need to know
• Define the term: Pollution. • State areas affected by pollution.• State mechanisms to control pollution.• Explain the difference between the terms
pollutant and pollution.• Discuss the ecological impact of one human
activity.
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Pollution
What it is
Types of pollution
Pollutants
Effects of pollutants
Control of pollutants
Ecological impact of one human activity
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Pollution
Pollution is any human addition (contamination) to a habitat or the environment that leaves it less able to sustain life.
It is the most harmful human impact and affects air, fresh water, sea, soil and land.
Chemicals of human origin that harm the environment are called pollutants.
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Some types of Pollution
Industrial/Air Pollution
Domestic Pollution
River/Water Pollution
Agricultural Pollution
– slurry, if it gets into a river/pond
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Learning check
Explain the difference between Pollution and Pollutant
Pollution is any human addition (contamination) to a habitat or the environment that leaves it less able to sustain life.
Pollutants are chemicals of human origin that harm the environment.
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Pollutants
are produced by human activities• CO2 from respiration is not a pollutant –
why?• excess CO2 from burning fossil fuels is
• SO2 from marshes & volcanoes is not – why?
• SO2 from factory chimney is
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Pollutants
Some pollutants are normally present in an environment, e.g. CO2, but levels are increased by human activity.
Other pollutants never exist in an environment e.g. oil slick, CFCs
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Learning check
List some types of pollution
• Industrial • Agricultural• Domestic• River/Water
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From the Syllabus & Guidelines
The Syllabus states: “Study the effects of any one pollutant.”
The Guidelines for Teachers states: “Give the effects of one pollutant from any of the following areas: domestic, agricultural, industrial.” and
“Give an example of one way in which pollution may be controlled in the selected area.”
What follows is only a sample of the pollutants available.
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Effect of one pollutant from one area- Agricultural, Industrial or Domestic
Area Pollutant Source Effects
Agricultural Slurry & Fertiliser
Washed or leached from land
Formation of algal blooms and eutrophication
IndustrialSulphur dioxide
Burning fossil fuels
Forms ‘acid rain’More detail later
Domestic Plastic bags ShoppingNon-biodegradable Suffocate small animals, Litter
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Eutrophication & Algal bloom
eutrophication: a condition where lakes become over-enriched with nutrients, resulting from excess artificial fertilisers washed into rivers and lakes.
There is a rapid increase in the growth of alga (algal bloom) as they use up the nutrients.
When all the nutrients are used up the algae die and are broken down by bacteria, which use up the oxygen in the water resulting in the death of aquatic organisms such as fish.
Eutrophication of a River
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Control of Pollutants in the selected area - Agricultural, Industrial or Domestic
Area Pollutant Control Measures
AgriculturalSlurry & Fertiliser
Avoid spreading these:• on wet, waterlogged, frozen or steeply sloping land• within 1.5m of any watercourse.
IndustrialSulphur dioxide
Fit catalytic scrubbers in factory chimneys
Domestic Plastic bagsBag tax/levy. Reuse/Recycle bags
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Learning check
CO2 is produced by all living things as a reuslt of respiration. Is CO2 a pollutant? Explain your answer.
No
Explanation: Pollutants are produced by human activities• CO2 from respiration is not a pollutant
• excess CO2 from burning fossil fuels is
Ecological impact of one human activity
Burning Fossil Fuels
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Acidic oxides and acid rain
• All rain is acidic – but not the same pH
• CO2 in the air dissolves in rainwater to form carbonic acid – pH = 5.5 in unpolluted air
• Acid rain refers to very acidic rain with a pH of 4.5 or less (Note: pH 4.5 is 10 times more acidic than pH 5.5)
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Acid rain
• Burning of fossil fuels (e.g. …) releases acidic oxides into the air, especially SO2 and nitrogen oxides (NOx)
• SO2 dissolves in rainwater to form sulphurous acid (H2SO3) or reacts with particles in the air to form sulphuric acid (H2SO4)
• The resulting rain is very acidic and can be carried far by the wind
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Effects of acid rain
• Reduces soil pH• Phosphorus (P) binds to soil particles and is
unavailable to plant roots• Al becomes soluble and poisonous and with
K, Ca and Mg is washed (leached) from the soil into lakes and water supplies
Soil is impoverished and fish die in highly mineralised water. Why?
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Effects of acid rain
• Erodes limestone buildings• Causes breathing difficulties – irritates the
delicate lining of the lungs• Inhibits chlorophyll formation and burns the
leaves of plants
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Learning check
What is acid rain?• Acid rain refers to very acidic rain with a pH
of 4.5 or less
How is acid rain formed?• Burning fossil fuels releases SO2 and nitrogen
oxides (NOx)
• SO2 dissolves in rainwater to form sulphurous acid (H2SO3) or reacts with particles in the air to form sulphuric acid (H2SO4)
• The resulting rain is acid rain
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Effects of acid rain
Acid rain is a ‘trans-boundary problem’ i.e. it is formed in one country but transported or blown huge distances to another.
Norway ‘imported’ its acid pollutions from the English Midlands and the Ruhr valley in Germany.
• Ireland is lucky that the prevailing winds are from the Atlantic and not from Europe.
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Dealing with acid rain
• Reducing the quantity of fossil fuels burned• Using catalysts to treat chimney gases
(‘scrubbers’ are fitted to the insides of chimneys)
• Catalytic converters fitted to modern cars• Developing alternative ‘clean’ energy
sources
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Learning check
List some of the effects of acid rain• Reduces soil pH• Phosphorus (P) becomes unavailable to plant
roots• Al, K, Ca and Mg is washed (leached) from the
soil into lakes and water supplies• Fish die in highly mineralised water• Erodes limestone buildings• Causes breathing difficulties • Inhibits chlorophyll formation• Burns the leaves of plants
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END
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