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IB ESS > 4.4 Water Pollution > Flashcards

4.4 Water Pollution Flashcards

1
Q

What are some factors affecting aquatic ecosystems?

A

Oxygen
Carbon Dioxide
Temperature
Light intensity
Plant life
Animal life

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2
Q

How does Oxygen affect aquatic ecosystems?

A
  • Dissolves in water
  • Concentration determines living organisms present
  • Often in limited supply (demand increases with number of organisms and their level of activity)
  • Increase in temperature decreases oxygen solubility
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3
Q

How does light intensity affect aquatic ecosystems?

A
  • Determines distribution of photosynthesis organisms
  • Decreases with depth
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4
Q

How does other plant/animal life affect aquatic ecosystems?

A
  • Microscopic phytoplankton - surface levels - important primary producer
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5
Q

How does temperature affect aquatic ecosystems?

A
  • Affects water density
  • Water takes relatively long time to heat up –> relatively stable habitat
  • Affects dissolved gases
  • Living organisms have narrow temperature tolerance limits (and optimum temperatures)
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6
Q

How does carbon dioxide affect aquatic ecosystems?

A
  • Dissolves in water to form carbonic acid
  • Increase in carbon dioxide –> decreases pH
  • Increase in temperature = decrease carbon dioxide solubility
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7
Q

What is the definition of pollution?

A

“Pollution is the addition of a substance or an agent to an environment by human activity, at a rate greater than that at which is can be rendered harmless by the environment, and which has an appreciable effect on the organisms within it”

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8
Q

What are some factors that can be measured to test the quality of aquatic systems?

A

pH
Temperature
Suspended solids
Metals
Nitrates
Phosphates

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9
Q

How do you test pH?

A

Using a pH meter:
- Hold meter in water for 1 minute and wait for pH reading to stabilise.
(take multiple readings)

ph 1-6: acidic
ph 7: neutral
ph 8-11: alkaline

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10
Q

How do you measure suspended solids? (turbidity)

A

Suspended solids are measured using a secchi disc (turbidity!)

Lower the disc into the water until you can’t see it any more - record that distance (the higher it is, the clearer the water –> the lower the number of suspended solids)

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11
Q

How do you measure nitrates, phosphates and metals?

A

Using test kits.
–> These give qualitative or semi-qualitative results.
(involves adding testing solutions to the samples and observing colour changes and comparing this to a chart)

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12
Q

What is the definition of “biological oxygen demand” (BOD)?

A

“BOD is a measure of the amount of dissolved oxygen required to break down the organic material in a given volume of water through aerobic biological activity”

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13
Q

How is BOD measured?

A
  1. Take a measured volume sample of water
  2. Measure the oxygen concentration of the sample (using a dissolved oxygen meter/ data logger)
  3. Seal the sample in an air-free container
  4. Place the sample in a dark place at 20 degrees for 5 days
  5. Re-measure the oxygen concentration of the sample
  6. The difference in oxygen concentration is the BOD
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14
Q

What is the BOD determined by?

A
  • Number of aerobic organisms in a water body at any given point
  • Their rate of respiration
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15
Q

Why is the BOD important?

A
  • Some species have higher tolerance level of organic pollution and the low levels of oxygen which coincide with organic pollution
  • Therefore the population density of such species will be higher in polluted areas as there is less competition from other species
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16
Q

Why is there lower dissolved oxygen during the summer months?

A

Summer –> Increase in temperatures –> water temperatures are higher –> solubility of oxygen decreases –> less available dissolved oxygen

17
Q

What do HIGH BOD levels indicate?

A

That there are MANY organisms using oxygen for respiration

18
Q

What is a biotic index?

A

A biotic index is a scale (1-10) that gives a measure of the quality of an ecosystem by the presence and abundance of the species living in it.

19
Q

Biotic indices are an i____ method of measuring pollution

A

Indirect

20
Q

Which species are used to esimate levels of pollution?

A

Invertebrates as these are particularly sensitive to oxygen concentration in water

21
Q

What is Eutrophication?

A

Eutrophication is the addition of excess nutrients (usually nitrates and phosphates) to a freshwater ecosystem, that results in the depletion of the oxygen content of the water.

22
Q

Eutrophication is a n____ process

A

NATURAL

It happens naturally over time but causes problems when process is accelerated by humans.

23
Q

Describe the eutrophication cycle?

A
  1. Excess nutrients wash into the river or lake
  2. High levels of phosphate in particular allow algae to grow faster
  3. Algal blooms form (mats of algae) that block out light to large plants beneath them, causing them to die
  4. More algae mean more food for the zooplankton and small animals that feed on them. These are eaten by fish which multiply as there is more food.
  5. Numbers of zooplankton then decrease so less algae are eaten and numbers increase further
  6. Algae have a high turnover rate and die off quickly. Dead algae are decomposed by aerobic bacteria
  7. A large food source means numbers of aerobic bacteria increase and they use up much of the oxygen in the water as they respire
  8. Falling oxygen levels lead to the death of many plants and animals and many food chains collapse
  9. Oxygen levels continue to fall as the amount of dead material increases and is broken down by bacteria
  10. Dead organic material forms sediments on the lake or river bed and turbidity increases
  11. Eventually all life is gone and the sediment settles to leave a clear blue lake
24
Q

What are some causes of eutrophication?

A

Industrial
–> dissolving of nitrogen oxides by burning fossil fuels
–> Nitrogen compounds produced by cars and factories

Natural
–> Natural run off

Agricultural
–> Inorganic fertiliser runoff (nitrates and phosphates)
–> Manure runoff from feedlots and fields applied with organic fertilizer

Urban
–> Discharge of detergents from homes (phosphates) in grey water
–> Discharge of untreated municipal sewage (nitrates and phosphates)

25
Q

What are some impacts of eutrophication?

A
  • Oxygen deficient water
  • Death of flowering plants
  • Death of aerobic organisms
  • Increased turbidity of water
  • Reduction in the length of food chains
  • Loss of biodiversity
26
Q

Eutrophication damage is less severe in ________ moving water

A
  • Fast moving water = less severe - temporary
    –> Decrease in biodiversity downstream followed by recovery and restoration of clean water
27
Q

What are some things the 1st step of the pollution management model would do to minimize Eutrophication

A

Replace:
- Try to minimise the impact on the environment by encouraging people to be restrained
- Use of organic fertilizers/ manure on agricultural fields
- Practice of mixed cropping/crop rotation so less or no fertilizers are needed
- Educational campaigns to encourage people to use less detergent/ move environmentally friendly detergent

28
Q

What are some things the 2nd step of the pollution management model would do to minimize Eutrophication

A
  • Plant a buffer zone between the fields and water courses to absorb any run-off
  • Developing an alternative to phosphates in detergents
  • Applying fertilizers more carefully so there is reduced run-off
  • Ban or limit detergents containing phosphates
  • Divert or treat sewage waste
29
Q

What are some things the 3rd step of the pollution management model would do to minimize Eutrophication

A
  • Using technology to screen water to remove pollutants
  • Pumping air through lakes to avoid the low oxygen conditions
  • Dredging sediments high nutrient levels from the river and lake beds
  • Remove excess weeds physically or by herbicides and algicides

IB ESS (44 decks)

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