Pollution
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Pollution. OCR Environmental Biology A2 Options module. 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.

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Pollution

Pollution

OCR Environmental Biology

A2 Options module


Introduction to pollution

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.


Sources of pollution

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.


The water cycle

The Water Cycle


The water cycle1

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)


Pollution

  • 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.


Pollution

  • 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.


Questions on the water cycle

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.


Eutrophication

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


Factors which influence the rate of eutrophication

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


Cultural eutrophication of lakes and rivers

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


Further problems caused by eutrophication

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


Causes of cultural eutrophication

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.


Stages of eutrophication

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.


Monitoring water pollution

Monitoring Water Pollution

  • Water pollution can be monitored in two ways.

    • Chemical analysis of the water

      • BOD

      • Chemical reagents

    • Indicator species


Biological oxygen demand

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.


Pollution

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).


Indicator species of water pollution

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.


Indicator species of water pollution1

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.


Pupil activity

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?


The effects of an organic effluent on a river at different distances downstream from the outfall

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)


Events affecting quality of water in a river

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.


Pupil activity1

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)


Pupil activity2

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


Homework

Homework

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


Additional reading

Additional Reading

  • Summary of Eutrophication (handout)

  • Websites

    • www.umanitoba.ca/institutes/fisheries/eutro.html

    • Look on www.findarticles.com search for articles on eutrophication.


Pesticides and toxins

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


The ideal pesticide

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


Problems associated with certain pesticides

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?!


Insecticides

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


Insecticides1

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


  • Case study ddt

    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.


    Case study ddt1

    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.


    Pupil activity3

    Pupil Activity

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


    Case study clear lake california

    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.


    Transfer of an organochlorine pesticide through the food chain of clear lake

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


    Pcb s and heavy metals

    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.


    Environmental concerns

    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.


    Heavy metals

    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


    Case study mercury poisoning

    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.


    Extension reading

    Extension Reading

    • Heavy Pollutants in the Aquatic Environment

      • Highlight summary points in the handout.


    Atmospheric pollution

    Atmospheric Pollution

    Acid Rain

    Ozone Hole

    Global Warming


    Atmospheric pollution1

    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.


    Atmospheric pollution2

    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


    Acid rain

    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


    Acid rain1

    Acid Rain

    • Natural precipitation is weakly acidic (pH 5.6), as carbon dioxide dissolves in rainwater it forms weak carbonic acid.

      • In Britain, Europe and North America, often find pH of 4 or 4.5

      • 10th April 1974 – Rainstorm in Pitlochry, Scotland, pH 2.4

    • The increasing acidity of rainwater has been attributed to the production of sulphur dioxide (SO2) and nitrogen oxides (NOX) during the burning of fossil fuels.


    Pupil activity4

    Pupil Activity

    • Read the Aric Fact sheet “What is Acid Rain?

    • Answer the following questions

      • What are the natural sources of sulphur dioxide and nitrogen oxides?

      • Compare the quantities of natural sources of these gases, and those released from emissions.


    Formation and deposition of acid rain

    Formation and Deposition of Acid Rain


    Formation and deposition of acid rain1

    Formation and Deposition of Acid Rain

    • Washout – when acids present below the clouds are taken up by the falling rain or snow.

    • Rainout – when cloud water droplets or ice crystals containing acids grow to sufficient size to fall.


    Effects of acid rain terrestrial ecosystems

    Effects of Acid RainTerrestrial Ecosystems

    • The most noticeable symptom of acid rain in terrestrial ecosystems is in trees

      • Conifers most at risk, as they do not shed there pines all at once.

      • Deciduous trees only have a few months to intercept acid rain, so only a seasons growth is damaged

    • As a result trees need extra energy to grow extra leaves, which can lead to a failure to reproduce, increasing susceptibility to disease, pests, drought and frosts.


    The effects of acid rain on trees

    The Effects of Acid Rain on Trees


    Effects on trees include

    Effects on trees include

    • Poor growth

    • Lower productivity

    • Discolouration of needles

    • Shallow roots

    • Dieback of crown

    • In Europe, deterioration can be seen in Norway spruce, Scots pine and beech.

    • In areas affected by acid rain populations of wildlife have declined (h/out impacts of air pollution and acid rain on wildlife)


    Pupil activity questions

    Pupil Activity- Questions

    • Which groups of animals tend to be most affected by air pollution and acid rain?

    • What factors play a part in the individual’s response to the pollutant?

    • Take each of the categories of pollutant in turn and describe their effects on wildlife.

      • Gases

      • Non acidic particulates and toxins

      • Acidifying agents (N, S)

    • Explain how acid rain and air pollution can have indirect effects on wildlife populations.


    Freshwater ecosystems

    Freshwater Ecosystems

    • 1960’s – 1980’s

      • Lakes in Scandinavia and Scotland lost large numbers of fish and fauna due to acidification.

    • Lakes on granite rocks are more at risk, as limestone helps to buffer the acidity.

    • pH 5.5 or less can lead to damaging of fish embryos and affect adult reproduction

    • At low pH increasing amounts of metal ions are leached out of soils and into streams e.g. Al, Cu, Zn, Mg


    Freshwater ecosystems1

    Freshwater Ecosystems

    • Aluminium

      • Toxic

      • Interferes with the regulation of gill permeability by calcium

      • Sodium is lost and gill surface clogs with mucus

      • This causes respiratory stress

    • Effects also include decrease in calcium uptake in crustaceans and molluscs, which they need to form exoskeletons and shells


    Pupil activity freshwater acidification

    Pupil Activity – Freshwater Acidification

    • List the effects of freshwater acidification and describe how these affect life in the lake/river.

    • Discuss the factors that lead up to freshwater acidification

    • Discuss the ecological advantages and disadvantages of restoration of acid waters (liming)


    Reversing effects of acid rain

    Reversing Effects of acid rain

    • Short term – add calcium carbonate to lakes

    • Long term – reduce sulphur and nitrous oxide emissions

    • Solutions to the problems

      1.    Improved engine designs

      2.    Use of low sulphur and cleansed fuel

      3.    Liming

    • Europe

      • 1990 – 2010 – trend indicate that acid rain emissions will by halved

  • Asia

    • 1990 – 2010 – acid emissions set to treble; coal is the major fuel used in power stations and cleaning measures are expensive.


  • Indicator species of airborne pollution

    Indicator Species of Airborne Pollution

    • Lichens are sensitive to sulphur dioxide, and therefore acid rain.

    • Lichens rely on rainfall for a water supply, they are slow growing but long lived.

    • Indicators of long term and short term pollution include:

      • Species present

      • Size of lichens

      • Condition of lichens


    Indicator species of airborne pollution1

    Indicator Species of Airborne Pollution

    • 1960’s Hawksworth and Rose – classified lichens into 10 zones

      • Zone 10 – lichens sensitive to Sulphur dioxide

      • Zone 1 – contains no lichens

    • In tropical regions, epiphytes, such as orchids are good indicators of airborne pollution as they are sensitive to air pollutants.


    Distribution of lichen zones in england and wales

    Distribution of Lichen Zones in England and Wales.

    Higher zones were found in rural areas, where the air contains the least pollutants.


    Extension reading1

    Extension Reading

    Handout – Air Quality and Lichens

    • Summarise how SO2 affects lichens, and explain how this enables us to use them as biological indicators.

    • Discuss one limitation of the lichen zone chart established by Hawksworth and Rose.


    Pollution of the air

    Pollution of the Air


    Structure of the atmosphere and absorption of ultraviolet and infrared light

    Structure of the atmosphere, and absorption of ultraviolet and infrared light


    Structure of atmosphere

    Structure of atmosphere

    • There are two gaseous regions above the Earth’s surface; the lower one called the troposphere and the upper on called the stratosphere.

    • The ozone layer forms the lower layers of the stratosphere, 15 – 30 km above the Earth’s surface.

    • Ozone layer – absorbs some of the sun’s ultraviolet radiation, acts as a global sunscreen.

    • Excess UV radiation damages the DNA in calls and increases mutation rates.


    Ozone depletion

    Ozone Depletion

    • Ozone is not an abundant molecule in the atmosphere, but it is highly significant for the following reasons:

      • Absorbs ultraviolet light (UV)

      • Involved in a complex series of reactions with natural and artificial chemicals in the environment

      • Has harmful effects on living organisms


    Ozone at ground level

    Ozone at ground level

    • Ozone (O3) is produced by the action of light on exhaust fumes. O3 tends to concentrate around heavy traffic and becomes a pollutant.

    • Effects at ground level

      • Corrodes metal

      • Irritates lungs and throat


    Ozone in stratosphere

    Ozone in Stratosphere

    • O3 is essential for a healthy life, intercepts UV radiation

    • UV

      • Decreases metabolism in plants and algae

      • Increases the occurrence of skin cancer and cataracts

      • May also damage the immune system


    O 3 formation

    O3 Formation

    • O2 -> O3 is a photochemical reaction

      • Most ozone forms above the tropics

      • No ozone forms over which ever pole is in darkness

    • 1980’s – decreasing amount of O3 above Antarctica

    • 1990 - large hole

    • Seasonal holes have appeared over the Artic

    • At lower latitudes the ozone in thinner and it is not advisable in Britain to tan without UV block


    Why should we care about ozone loss

    Why should we care about ozone loss?


    Why should we care about ozone loss1

    Why should we care about ozone loss?

    • Less ozone in stratosphere, more harmful UV radiation reaches Earth.

      • Worse sunburns

      • More cataracts

      • Increase chance of skin cancer

      • Suppression of immune system

      • Yields of crops may drop (UV sensitivity)

      • Decreases the metabolism of plants and algae


    Worse case scenario

    Worse Case Scenario


    Chlorofluorocarbons cfcs

    Chlorofluorocarbons (CFCs)

    • Chemicals containing bromine and chlorine are responsible for thinning the Ozone Layer.

    • They are from a group called halocarbons and include CFCs, the pesticide methyl bromide, nitrous oxide and methane.


    Problem started

    Problem Started

    • 1970’s and 1980’s – CFC’s widely used in refrigerators, aerosol sprays, solvents, cleaning agents, fire extinguishers, fast food packaging.

    • In winter, CFCs accumulate in clouds, then in spring, sunlight causes a photochemical reaction which breaks down CFC’s into “free radical” chlorine atoms. This occurs mainly in the polar areas.


    Pollution

    CFCs

    • Chlorine atoms react with ozone

      Cl• + O3 ClO• + O2

    • ClO• reacts with atmospheric components (usually an oxygen atom)

      ClO• + O  Cl• + O2

    • Ozone molecule is destroyed without using up the chlorine.

    • Chlorine catalyses the reaction, it is estimated that one chlorine atom can remove 100 000’s ozone molecules.


    Montreal protocol

    Montreal Protocol

    • Summarise the international attempts to control the levels of CFC’s

    • 16th Sept 1987

      • 21 states and those in the EC signed the Montreal Protocol on Substances that delete the Ozone Layer

      • This was the first ever environmental treaty

      • Aim:to halve emissions of CFC’s by 1999


    3 phase programme for reduction of cfc production

    3-phase programme for reduction of CFC production

    • Phase 1:

      • To cap CFC production in the middle of the year at 1986 levels.

    • Phase 2:

      • Between 1993 and 1994 nations should cut CFC consumption by 20%

    • Phase 3:

      • Reduce CFC use by 50% by 1999


    Exemptions to treaty

    Exemptions to treaty

    • Eastern bloc countries, developing countries, Brazil and Argentina.

    • Since then further modifications have been brought in, by 1995 150 countries had signed up.


    Problems

    Problems

    • CFC’s can persist in the stratosphere for 70 years

    • Only applies to developed countries

    • Insufficient funds to help countries switch to less ozone depleting technology.

    • Methyl bromide production will not be cut back until 2002.

    • Black market for CFC’s in America and Europe.

    • Alternatives to CFCs include the greenhouse gases.


    Carbon dioxide the greenhouse effects

    Carbon DioxideThe Greenhouse Effects

    • Outline roles of carbon dioxide and methane in enhanced greenhouse effect and global warming.

    • Appreciate international efforts to reduce carbon dioxide emissions.


    Carbon dioxide

    Carbon Dioxide

    • Carbon dioxide is naturally occurring in the atmosphere at a concentration of less than 0.05%.

    • CO2 Levels

      • Constant 2,500 – 200 ya 270ppm

      • Since industrial revolution risen to 360ppm

    • Since 1960 levels have been slowly rising


    Carbon dioxide concentrations in the northern hemisphere

    Carbon dioxide concentrations in the Northern Hemisphere


    Seasonal variations in co 2 concentrations

    Seasonal variations in CO2 concentrations

    • Spring & summer – CO2 levels fall, as plants make new leaves and grow

    • Autumn & winter – CO2 levels rise as leaves fall and decay, producing CO2

    • 2 reasons for overall rise in CO2 levels

      • Global use of fossil fuels as energy source; fossil fuels act as sinks in the carbon cycle, carbon would not naturally escape.

      • Increase in the destruction of the world’s forests. Trees act as carbon reservoirs


    Rate of co 2 fixation by trees

    Rate of CO2 fixation by trees

    • Tropical rainforest

      • between 1-2 kg/m2 carbon per year

    • Deciduous forest

      • 0.2 – 0.4kg/m2/year

    • Increasing CO2 levels caused by deforestation is reversible. As regrowth of forests would use CO2 and release O2

    • Forests can be renewable energy resources if allowed to grow.


    Greenhouse effect

    Greenhouse Effect

    • The presence of the atmosphere increases the Earth’s surface temperature by an average of about 33oC.

    • Sun’s energy travels through the atmosphere and warms the Earth’s surface.

    • Some heat is radiated back into the atmosphere where the gases prevent heat energy from escaping into outer space.


    Pollution

    Greenhouse gas

    Source or origin

    Water vapour (H2O)

    Evaporation and transpiration

    Carbon Dioxide (CO2)

    Combustion of fossil fuels, wood

    CFC’s

    Refrigerators, aerosol sprays

    Methane (CH4)

    Cattle, rice fields, bogs and rubbish tips

    Nitrous oxide (N2O)

    Denitrification

    Ozone (O3)

    Secondary pollutant from car exhausts


    Pollution

    • Due to human activity CO2 and CH4 are increasing in abundance. This may be causing global warming by enhancing the natural greenhouse effect of the atmosphere.

    • Methane (CH4)

      • Primarily from the breakdown of cellulose

      • Animal emissions exceed 100 million tonnes

      • 10 times more effective as a greenhouse gas than CO2

      • Concentration in the atmosphere is lower than carbon dioxide

      • Increase 800ppbv to 1720ppbv in last 200 years

    • Carbon dioxide contributes about 60% to the greenhouse effect, methane contributes about 15%.


    Climatic effects

    Climatic Effects

    • Climate in naturally variable, last 100 years seen an average world temperature rise of 0.5oC

    • Predicted a 1oC – 5oC rise in the next 50 years

    • What evidence?

    • The effects of global warming are not known, and many scientists remain unconvinced that it is occurring.


    Present situation

    Present Situation

    • Oceans surface is warmer at the equator

    • More water evaporates

    • Warm air rises faster causing stronger winds

    • Moisture laden air is carried further from the tropics

    • Less rain in the tropics

    • Floods in temperate regions

  • Last 30 years seen more extremes of weather and more droughts in the tropics


  • El nino

    El Nino

    • Warms surface waters off the coast of South America

    • Causing drought and conditions in Australia and Indonesia

    • Torrential rain in Peru and Ecuador.

    • If El Nino lasts for 12 months or longer, it severely disrupts populations of plankton, fish and seabirds in upwelling areas and can trigger extreme weather changes over much of the globe.


    Future

    future

    • Death and destruction from hurricanes and floods

    • Ice caps melt – rise in sea levels

    • Polar meltdown would switch the path of the Gulf Stream

      • colder climate in the North Atlantic and UK.


    Effects of global warming on british flora

    Effects of Global Warming on British Flora

    • Increasing the northwards range of rare orchids

    • Plants adapted to the cold would suffer e.g. bluebells rely on a cool spring

    • Due to the complexity of ecosystems it is very difficult to predict how changes in climate will affect biodiversity. However the combination of this and habitat loss is not looking good for biodiversity.


    International efforts to reduce carbon dioxide emissions

    International efforts to reduce carbon dioxide emissions

    • 1998 – international panel on climate change formed to report on the global situation

    • 1992 – climate change convention was signed at the Rio Earth Summit in 1992 (greenhouse gas emissions to go back to 1990 levels by 2000)

    • 1997 - Kyoto Protocol

      • Recognised this was unachievable

      • Targeted CO2, methane, nitrous oxide, some fluorocarbons and sulphur hexafluoride.

      • Aim to cut emissions to 5% below 1990 by 2010

      • Each nation given a specific target – allowing countries to trade in carbon emissions


    Montreal vs kyoto protocol

    Montreal Protocol

    Kyoto Protocol

    Ozone depletion was evident

    Uncertainty about the actual consequences of global warming.

    Technology existed to replace CFC’s with less damaging products

    Developed world is reliant on fossil fuels, no easy alternative energy source.

    - Developed countries need to make the major contribution to lowering greenhouse gas emissions.

    Montreal vs. Kyoto Protocol


    Pollution

    • Another reason for lack of success is the current political climate.

    • To stabilise atmospheric CO2 at 560ppm (which is two time the natural level), requires a reduction to 60% below 1990 levels.


    Approaches to reducing emissions

    Approaches to reducing Emissions

    • Less reliance on fossil fuels, switch to renewable energy resources

    • Energy saving measures – insulating houses

    • Lower expectations about the standard of living

    • Plant more trees (CO2 sink)

    • Alternatives to petrol and diesel for a fuel – “clean sources of energy”

    • Pump CO2 underground or down to ocean floor

    • Encourage massive oceanic algal blooms to trap CO2 in organic matter.


    Are there any environmentally friendly fuels

    Are there any environmentally friendly fuels?

    • Handout – are any of the alternatives environmentally friendly?


    Revision questions

    Revision questions

    • Explain how anthropogenic eutrophication can lead to loss of certain species from aquatic habitats.

    • Explain why the use of biochemical oxygen demand and indicator species may give different measures of water pollution.

    • List five harmful consequences of acid rain.

    • Briefly distinguish between the roles of CFCs in the thinning of the ozone layer and the greenhouse effect.


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