1.4.9 Human Impact on an Ecosystem 1 Pollution
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.
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.
Domestic Pollution Industrial/Air Pollution Some types of Pollution Agricultural Pollution – slurry, if it gets into a river/pond River/Water Pollution
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.
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
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
Learning check List some types of pollution • Industrial • Agricultural • Domestic • River/Water
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.
Effect of one pollutant from one area- Agricultural, Industrial or Domestic
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.
Control of Pollutants in the selected area - Agricultural, Industrial or Domestic
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
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)
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
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?
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
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
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.
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
Learning check • 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 List some of the effects of acid rain