Water pollution

Question 1

What is water pollution?

Answer 1

Water pollution is the contamination of bodies of water by pollutants either directly or indirectly

Question 2

Name 4 sources of freshwater pollution

Answer 2

• Agricultural run-off
• Sewage
• Industrial discharge
• Solid domestic waste

Question 3

What is the impact of oil (inorganic pollutant) on water

Answer 3

• floats on surface
• contaminates seabirds
• reduces oxygen levels

Question 4

What is the impact of light + noise pollution on water ecosystems?

Answer 4

• Disrupt turtle nesting sites
• Upset whale navigation
• Change plant growth
• Upset bird cycles

Question 5

What is the biochemical oxygen demand (BOD) ?

Answer 5

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 by microorganisms

Question 6

What are indicator species?

Answer 6

plants and animals that show something about te environment by their presence, absence, abundance or scarcity

Question 7

What is a biotic index?

Answer 7

A biotic index indirectly measures pollution by assaying the impact on species within the community according to their tolerance, diversity and relative abundance

Question 8

Give an example of an indicator species

Answer 8

Indicator species are most sensitive to change so they are the early warning signs that something has changed in ecosystem

e.g. canaries taken down coal mines as they’re more sensitive than humans to poisonous gases, if gases present, canary would die so miners would know to get out

Question 9

Why are invertebrates used to estimate levels of pollution?

Answer 9

• they are sensitive to decreases in oxygen concentration of water, caused by the action of aerobic bacteria as they decompose organic matter
• the presence of indicator species is used to calculate a biotic index

Question 10

How do dead zones and anoxic conditions result from eutrophication?

Answer 10

• When its severe it results in dead zones in oceans//freshwater where theres not enough oxygen to support life
• in less severe cases, biodegradation of organic material uses up oxygen which can lead to anoxic conditions + then anaerobic decomposition, releasing methane and ammonia (toxic gases)

Question 11

Name 5 impacts of eutrophication

Answer 11

• Anaerobic water
• Loss of biodiversity + shortened food chains
• Death of higher plants (eg flowering plants)
• Death of aerobic organisms (invertebrates, fish)
• Increased turbidity of water

Question 12

Name 5 causes of eutrophication

Answer 12

• detergents
• fertilisers
• draining from intensive livestock rearing units
• sewage
• increased erosion of topsoil into water

Question 13

Outline the process of eutrophication

Answer 13

• Eutrophication is increase in nutrients (e.g. phosphates + nitrates) in rivers + lakes
• May be from natural run-off from surroundings or decomposing biomass
• Also from agricultural actual and fertiliser
• Also from sewage
• Increase in biomass of algae caused by both human + natural eutrophication
• Algal blooms prevent plants underneath them receiving light and so increased bacteria feed on them and reduce oxygen content of water
• Reduced oxygen causes collapse of food chains

Question 14

Where has the largest zone in the USA and what are the solutions?

Answer 14

• Gulf of Mexico has largest dead zone in USA
• Caused by excess nitrates+phosphates from Mississippi river basin agriculture
• Solution = a water quality trading scheme that allows those that can reduce nutrients at low cost to sell credits to this facing higher-cost nutrient reduction options

Question 15

What are red tides?

Answer 15

• in coastal waters, algal blooms (large no. of phytoplankton) are sometimes caused by excess nutrients
• if these phytoplankton are a species of dinoflagellate, the bloom looks red
• algae produces toxins which kill fish + accumulate in shellfish, making humans v ill

Question 16

Strategy for reducing pollution // altering the human activity

Answer 16

• Ban detergents w phosphates
• Use ecodetergents w no phosphates
• Plant buffer zones between field + water courses to absorb excess nutrients
• Stop leaching of animal waste or sewage from their sources
• Educate farmers about effective timing for fertiliser application

Question 17

Strategy for reducing pollution // regulating + reducing pollutants at point of emission

Answer 17

• Treat wastewater before release to remove phosphates + nitrates
• Divert // treat sewage wast effectively
• Minimise fertiliser dosage in farming
• Use organic matter instead

Question 18

Strategy for reducing pollution // clean-up and restoration

Answer 18

• Pumping air through lakes
• Dredging sediments w high nutrient levels
• Remove excess weeds
• Restock water bodies w appropriate organisms