Pollution

1. Pollution OCR Environmental Biology A2 Options module

2. Introduction to Pollution • Environmental pollution results from human activities causing the release of substances that should not be there; or build up of substances to unnatural or dangerous levels. • Pollutants released – water, land or air; most “pollutants” occur naturally but in much lower concentrations. • Effects of pollution can be: • Localised • Global • Earliest pollution recorded – heavy metals in Greenland ice sheet from 4000 – 3000 years old.

3. Sources of pollution • Increasing industrialisation • Extraction of raw materials • Processing and disposal of waste products • Intensive farming • Everyday domestic life • The source of pollution is not always the area where the effects of pollution are felt.

4. The Water Cycle

5. The Water Cycle • Water evaporates from oceans and rise from vegetation on land (evapotranspiration). • Condensation • Precipitation • Excess water – ground water storage or surface run off to form freshwater streams. • Lakes can form where water is blocked in an area; but artificial lakes can also be made (e.g. dams)

6. The Water Cycle • The hydrologic cycle (water cycle), collects, purifies, and distributes the earth's fixed supply of water. • The main processes in this water recycling are described below • Replenishing inland water supplies, • Rainwater causes erosion • Major medium for transporting dissolved nutrients within and among ecosystems.

7. On a global scale, evaporation exceeds precipitation over the oceans. This results in a net movement of water vapour (carried by winds) over the land. • On land, precipitation exceeds evaporation. Some of this precipitation becomes locked up in snow and ice, for varying lengths of time. • Most forms surface and groundwater systems that flow back to the sea, completing the major part of the cycle. • Living organisms, particularly plants, participate to varying degrees in the water cycle. • Over the sea, most of the water vapour is due to evaporation alone. • On land, about 90% of the vapour results from plant transpiration. • Animals (particularly humans) intervene in the cycle by utilising the resource for their own needs.

8. Questions on the water cycle • Name two ways in which water returns to the oceans from the land. • Briefly describe 3 ways in which humans intervene in the water cycle, and the effects of these interventions. • Name the main reservoir of water on earth. • Name the main reservoirs of fresh water. • Describe the important role of plants in the cycling of water through ecosystems.

9. Eutrophication • “Enrichment of waters by inorganic plant nutrients, usually nitrogen and phosphorous, which increases primary production” • Freshwater ecosystems are classified by the status of nutrients in their waters. • Oligotrophic = nutrient poor and unproductive • Eutrophic = rich in nutrients and productive • Mesotrophic = waters that fall in between

10. Factors which influence the rate of eutrophication • Natural eutrophication is caused by natural features of a lakes catchment, e.g. a lakes nutrient content rises with age. • Cultural eutrophication – anthropogenic influences. • Most important factors in temperate lakes are: • Fertility of drainage basin • Seasonal behaviour of the water • Depth of a lake • Temperature of the water • Rate of turnover of the water • Cultural eutrophication

11. Cultural Eutrophication of lakes and rivers • Areas of concern for lakes and rivers • Acidification of lake water associated with acid rain • Introduction of toxic wastes • Eutrophication • Effects of cultural eutrophication • Species diversity decreases and the dominant biota change • Turbidity increases • Rate of sedimentation increases • Anoxic conditions may occur

12. Further problems caused by eutrophication • Difficulties in the treatment of drinking water • Growth of algae may leave unacceptable tastes or odours in the water supply • Water may be injurious to health • Amenity value is reduced • Growth of plants may inhibit water flow and navigation • Loss of salmonids and coregonids from water may have economic consequences for fisheries

13. Causes of Cultural Eutrophication • Soil erosion may increase phosphate levels in the water • Nitrates from inorganic fertilizers or from sewage treatment facilities • Phosphate from animal waste; sewage or manure • Possible solution to eutrophication is to limit the amount of phosphorous going into watercourses, as it is cheaper to remove at sewage treatment plants.

14. Stages of Eutrophication • Algal bloom – caused by the effect of fertilizers on the growth of microscopic green algae • Rapid growth of algae causes death of higher plants • Flow rate of river slows down • Older algae decompose, bacterial populations increase (BOD increases) • Fish are killed and the entire food web of the river is disrupted.

15. Monitoring Water Pollution • Water pollution can be monitored in two ways. • Chemical analysis of the water • BOD • Chemical reagents • Indicator species

16. Biological Oxygen Demand • BOD is a common measure of organic pollution • Calculation of BOD • How much oxygen is taken up by a sample of water when it is kept in the dark for 5 days at 20oC. • Kept in the dark to prevent photosynthesis. • Therefore the oxygen used up is by the micro-organisms breaking down organic matter.

17. The table below shows the BOD of some organic pollutants, the figures are for before the pollutants enter a river (once in a river the pollutant will become diluted).

18. Indicator Species of Water Pollution • In order to use indicator species as a measure of organic pollution you must first understand the tolerance levels of different species to pollution. A level for pollution is estimated depending on the presence or absence of certain organisms from a habitat. • Biological monitoring gives a summary of the recent history of the environment.

19. Indicator Species of Water Pollution • In 1964, Trent River Authority devised a recording system for monitoring the pollution of watercourses. • BMWP Score Sheet – points are allocated on the presence of invertebrate families. The score is totalled them divided by the number of groups present. The lower the score, the more polluted the river. • Aquatic plants and invertebrates complement each other as biological indicators, as they have different tolerance levels to certain chemicals.

21. Pupil Activity • Explain why the use of biochemical oxygen demand and indicator species may give different measures of water pollution. • Suppose a river contains only the families Piscicolidae, Planorbidae, Hirudidae, Asellidae and Chironomidae; what is the BMWP score?

22. The effects of an organic effluent on a river at different distances downstream from the outfall A + B = physical and chemical changes C = changes in micro- organisms D = changes in larger animals (based on Hynes, 1960)

23. Events affecting quality of water in a river • In a given stretch of river, there is continual exchange of water, so that events at some distance upstream can affect the river much lower down.

25. Pupil Activity • Practice Exam Questions • Answer all practice questions in full • You can use your notes and the text books • Typical changes of water quality and the plant and animal populations in a river after the introduction of sewage. • Give an account of the ways in which human activities lead to the pollution of water (10 marks)

26. Pupil Activity • Sewage – inadequate treatment leading to pollution • Using the information given in the handout, in the table and in the graphs, explain as fully as possible the changes of water quality, and plant and animal populations in a river after the introduction of sewage

28. Homework • Make notes on how Lichens can work as an indicator species for Air Pollution.

29. Additional Reading • Summary of Eutrophication (handout) • Websites • www.umanitoba.ca/institutes/fisheries/eutro.html • Look on www.findarticles.com search for articles on eutrophication.

30. Pesticides and Toxins • Appreciate the need for pesticides and explain the consequences of pollution by DDT. • Pesticides are an important group of agricultural chemicals, which are designed to kill organisms, therefore their use has health and environmental concerns. • Need for pesticides • Necessary in intensive farming regimes to; • prevent damage of crops whilst growing • give a longer shelf life to fruits and vegetables by reducing decay from surface micro-organisms • reduce the infection of farm animals

31. The Ideal Pesticide • effective at low dosage against its specific target • inexpensive to manufacture • non-polluting • Plentiful • easy to apply • breakdown products should be harmless to non-target organisms in air, soil and water

32. Problems associated with certain pesticides • pose a risk to human health • herbicides have a rapid breakdown and are only toxic when absorbed or ingested in high concentrations • fungicides not known to have environmental effects?!

33. Insecticides • Early insecticides include: • stomach poisons • tar oils • plant extracts • Since 1940’s 3 main types of insecticides come into use • Organochlorines (chlorinated hydrocarbon compounds) • Examples – DDT, Dieldrin • Ecological effects of DDT, accumulation of toxin in food chains • Organophosphate compounds • Examples – malathion and diazion • Very toxic to insects and humans

34. Insecticides • Carbamates • Examples – carboxyl, aldicarb • Do not leave long lasting residues in environment • Lethal to non-target organisms • Problems with pesticides • Kill non-target species • target species evolve resistance to the insecticide • some insecticides become concentrated up food chains

36. Case Study: DDT • The story of dichlorodiphenyltrichloroethane (DDT to its friends) • In 1939 DDT was first used as an insecticide. DDT and other Organochlorines last for 10-25 years in the environment. As they are more soluble in fat than water, once they have been ingested they remain in fatty tissues (lipids). • DDT and Organochlorines have been found to accumulate in food chains.

37. Case Study: DDT • In the 1950’s the numbers of peregrine falcons in Europe halved over 20 years, this was traced to DDT dressing put on seeds, eaten by pigeons, eaten by the Falcons. The DDT caused the falcons to lay eggs with thinner shells, so when they were sat on they were smashed. In the 1980’s, after restrictions on the use of DDT, falcon numbers returned to normal.

38. Pupil Activity • Read through the information, answer the questions on “pesticides and Bioaccumulation”.

39. Case Study: Clear Lake, California • The earliest example of Bioaccumulation comes from Clear Lake in California. • 1949 • lake was sprayed with DDD, 99% of non-biting phantom midge larva died. • 1951 • swarms of midge recover • 1954 • second dose of DDD, this time more concentrated • 100 Western Grebes dead on lake (bioconc. X 30 000) • 1957 • population fell 30 000 to 30 pairs, most of which were sterile • 1960’s • switch to substitute organophosphorous insecticide and Grebe populations are slowly recovering.

40. Transfer of an organochlorine pesticide through the food chain of Clear Lake.

41. PCB’s and Heavy Metals • Outline the sources of polychlorinated biphenyls (PCBs) and heavy metals and the consequences of their release on the environment. • PCBs • There are over 200 different types of PCB; they were first released in the US in 1929. • Their use includes electrical insulators and the manufacture of paint, ink and plastics. • Effects of PCBs were first noticed in the 1960’s and their use was banned in the 1970’s.

42. Environmental Concerns • Egg shell thinning • Interference with mammalian reproduction • Damage to the immune system • Carcinogenic • Since 1988, over 20 000 seals in the North Sea have died of viral infections, these are thought to have been enhanced by PCB poisoning. • In Canada, Inuit nursing mothers have five times more PCB in their milk than mothers in southern Canada.

43. Heavy Metals • Heavy metals become pollutants when found in high concentrations in water and soils. • There has been an increase in heavy metal concentrations since the industrial revolution, but they have been around for over 3000 years. • Effects at high Concentrations • 1.    Toxic to animals • 2.    Developmental defects • 3.    Cancers • 4.    Kidney failure • 5.    Immune system failure

44. Case Study: Mercury Poisoning • Mercury is a serious pollutant in the Amazon Basin, where it is used to extract gold. • In the 1950’s in Minamoto Bay in Japan, high concentrations of Methyl Mercury was released into the river, this concentrated in the marine food chain. • The Japanese ate fish and shellfish; over 1000 people were killed or disabled between 1950 and 1970. • Some plants can develop tolerance to heavy metals, for example Leadwort near the abandoned lead mines in Yorkshire and Derbyshire.

46. Extension Reading • Heavy Pollutants in the Aquatic Environment • Highlight summary points in the handout.

47. Atmospheric Pollution Acid Rain Ozone Hole Global Warming

48. Atmospheric Pollution • Atmospheric pollution can be attributed to anthropogenic causes; it causes harm to humans and other living organisms in the environment. • By the late 20th C. atmospheric pollution effects can be seen in all nations of the world. • Air pollution is a global problem as it ignores international boundaries, as does the wind that carries it. This had led to international co-operation and global legislation for air pollution.

49. Atmospheric Pollution • The increase in pollution over the last 150 years can be attributed to the increasing human population and increases in urban and industrialised societies. • There are 3 main forms of atmospheric pollution • Acid rain • Ozone hole • Global warming

50. Acid Rain • Explain the production of acid rain and it’s effect on lakes and forests • 1872 - The Scottish chemist, Robert Angus Smith, first used the term “Acid rain”. • Acid rain is used to describe the acidity of wet and dry deposition • Wet deposition = rain, snow, hail, sleet, mist or fog • Dry deposition = gases and particles