4.4 Water Pollution

Question 1

BOD definition

Answer 1

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

Question 2

BOD is affected by

Answer 2

the number of aerobic organisms, their rate of respiration

Question 3

why can BOD be used to measure pollution

Answer 3

it indicates the amount of oxygen needed by microorganisms to break down organic matter in water. High BOD levels mean there is a lot of organic pollution (like sewage or waste), which depletes oxygen in the water, making it harder for aquatic life to survive. Essentially, the higher the BOD, the more polluted the water is

Question 4

what is an indicator species

Answer 4

can be used as an indirect measure of pollution and/or environmental degradation

the presence or absence and health of these indicator species can be used to suggest conditions in the environment

Question 5

example of biotic indices that can measure pollution levels

Answer 5

tolerance, diversity and abundance of organisms

Question 6

eutrophication, what happens?

Answer 6

increase in nitrates and/or phosphates, leading to rapid growth of algae, accumulation of dead organic matter, a high rate of decomposition, increased BOD, oxygen-dependent organisms die

Question 7

natural causes of eutrophication

Answer 7

• Nutrients added from decomposing biomass
• run-off from surrounding areas
• upwelling ocean currents bringing nutrients to the surface

Question 8

human causes of eutrophication

Answer 8

• Run off of fertilisers or manure from agricultural land
• domestic wastewater that contains detergents (that have phosphates)
• non treated sewage

Question 9

positive feedback in eutrophication

Answer 9

Question 10

negative feedback in eutrophication

Answer 10

increase in nutrient promotes growth of plants that store them in biomass -> reduction in nutrients so balance is restored

Question 11

impacts of eutrophication environmental

Answer 11

• more bacteria increase BOD → makes water anoxic
• algal blooms → less light penetration to underwater plants
• reduced oxygen levels leads to death of organisms
• diversity of primary producers changes and finally decreases (dominant species change)

Question 12

impacts of eutrophication society

Answer 12

financial: loss of fertilisers from fields may reduce crop productivity and therefore farm yield and profit

health: nitrate-enriched water is associated with higher rates of stomach cancer and ‘blue baby syndrome’

Question 13

what is a dead zone

Answer 13

can occur in oceans and freshwater when there is not enough oxygen to support aquatic and marine life (can be a result of eutrophication)

Question 14

1 pollution management strategy

Answer 14

altering human activity
- legislation or taxes to limit use of nitrate rich fertilisers
- educational campaigns to promote organic farming
- developing alternatives to phosphates in detergents

Question 15

2 pollution management strategy

Answer 15

regulating and reducing pollutants at point of emission
- plant buffer zones around fields to avoid run off
- use fertiliser only at times of low rainfall, to reduce runoff

Question 16

3 pollution management strategy water pollution

Answer 16

clean up and restoration
- pump oxygen into anoxic lakes and ponds
- restock water bodies with fish and other species
- introduce surface plants, to absorb excess nutrients

Question 17

abiotic features that one can measure

Answer 17

• ph of water
• dissolved oxygen levels
• amount of sunlight
• turbidity of water

Question 18

biotic features that one can measure for water pollution

Answer 18

• birth and death rate of different species
• species abundance and richness
  
  • simpsons diversity index
  • lincoln index
• amount of decomposers
• habitat + genetic diversity
• algae -> use area or volume

Question 19

2 examples of indicator species

Answer 19

1. high levels of river pollution = tubifex (worm)
2. low levels of river pollution = stonefly nymph (bug)