chapter 20

Question 1

water pollution

Answer 1

any chemical, biological, or physical change in water quality that has a harmful effect on living organisms
- e.g. infectious bacteria, inorganic & organic chemicals, excess heat

Question 2

how scientists monitor water quality

Answer 2

• bacterial counts; drinking water should not contain any colonies per 100mL; safe swimming water should not have more than 200 colonies per 100mL
• chemical analysis: checking inorganic/organic chemicals, sediment content, and turbidity
• indicator species

Question 3

bacterial source tracking

Answer 3

new field of science that uses molecular biology techniques to determine subtle differences in strains of bacteria based on their host

Question 4

biological oxygen demand

Answer 4

the amount of dissolved oxygen consumed by aquatic decomposers

Question 5

point-source v. nonpoint-source pollution

Answer 5

point source: discharge pollutants at specific locations; easy to identify, monitor, and regulate
- drain pipes, ditches, sewer lines, factories

nonpoint source: scattered and diffused; cannot be traced back to any single site of discharge; difficult and expensive to identify/control
- runoff from croplands & livestock feedlots

Question 6

leading sources of water pollution

Answer 6

• agriculture: erosion/overgrazing, fertilisers, pesticides, excess salt (from irrigation)
• industries
• mining

Question 7

recovery from pollution in STREAMS

Answer 7

• combination of dilution & biodegradation if stream’s flow is not reduced due to damming, agricultural diversion, drought
• breakdown of pollutants by bacteria –> oxygen sag curve; organisms that have high oxygen demand die

Question 8

sag curve

Answer 8

graph that shows how the concentration of dissolved oxygen in a body of water changes over distance from a point of pollution

Question 9

factors of how great a sag curve is

Answer 9

• volume of stream
• volume of wastes entering
• flow rate
• temperature
• pH levels

Question 10

factors of severe pollution in the ganges river, india

Answer 10

• religious beliefs, cultural traditions
• poverty
• little economic development
• large population size

Question 11

why are lakes less effective at diluting pollutants?

Answer 11

• lakes are often lentic/still bodies of water with little to no flow
• lakes are stratified into layers with little vertical mixing; may take 100yrs to flush/change water in lakes
• lakes are more vulnerable to runoff contamination
• chemical concentrations biomagnify through the food webs in lakes

Question 12

eutrophication

Answer 12

when a body of water receives too many nutrients, which leads to an overgrowth of algae and other microorganisms

Question 13

natural vs cultural eutrophication

Answer 13

• natural: natural nutrient enrichment of lakes, depends on composition of surrounding drainage basin, enrich abundance of desirable organisms
• cultural: human-caused, near urban or agricultural areas, can lead to significant pollution problems, also in coastal waters/estuaries/bays due to runoff

Question 14

“blooms” of organisms reducing lake productivity

Answer 14

• algae overgrowth –> less sunlight
• algae overgrowth –> increases bacteria, decreases DO –> fish die –> if it gets bad enough, anaerobic bacteria take over

Question 15

how to reduce cultural eutrophication

Answer 15

• banning/limiting phosphates in detergents
• using advanced treatment methods to remove nitrates & phosphates from wastewater
• using soil conservation methods to reduce runoff

Question 16

how to clean up lakes

Answer 16

• removing excess weeds
• controlling plant growth
• pumping air through lakes to avoid oxygen depletion

Question 17

Why is groundwater especially vulnerable to contamination?

Answer 17

• groundwater cannot effectively cleanse itself and dilute/disperse pollutants
• groundwater flows very slowly
• cleansing is slow bc of low DO, cold water temperature, less population of decomposing bacteria
• degradable wastes may take 100s of years to cleanse; nondegradables stay forever
• groundwater pollution is a low-risk ecological ecological issue, but a high-risk human health issue

Question 18

Effects of nitrates in ground water

Answer 18

• prevalent in agricultural areas
• nitrates convert to nitrites in the body —> can cause cancer
• in babies under 6mo, high levels of nitrites can lead to blue baby syndrome, where blood cannot cary sufficient oxygen to the cells

Question 19

Degradable pollutants (examples)

Answer 19

raw sewage, sludge, oil, some industrial wastes

• high levels of degradation occur in deep-water areas and rivers/streams with high flow rate

Question 20

coastal pollution

Answer 20

• 40% of the world’s population lives on or within 100km from the coast; this puts a tremendous burden on wetlands, estuaries, coral reefs, mangrove swamps
• sewage is often dumped into the sea without treatment; beach pollution, shellfish contamination
• extensive nonpoint runoff has caused seasonal, large oxygen-depleted zones in temperate coastal waters due to oxygen depletion

Question 21

preventing coastal pollution

Answer 21

• reduce number and size of oxygen-depleted zones
• reduction of nitrogen inputs
• planting forests & grasslands to soak up excess nitrogen
• restore costal wetlands
• improve sewage treatment
• require further reduction of NOx emissions
• use forms of renewable energy to replace fossil fuels

Question 22

london dumping convention 1972

Answer 22

100 countries agreed to not dump highly roxic pollutants & radioactive wastes into the open sea
- by 1994, it became a permanent ban

Question 23

oysters’ roles in water pollution

Answer 23

• oysters filter algae and silt
• over-harvesting, coupled with two parasitic oyster diseases reduced the oyster population to about 1% of its population in chesapeake bay
• introduction of disease-resistant oysters into chesapeake bay could help to recover the population and filter pollution faster

Question 24

causes of oil pollution in oceans

Answer 24

• released from day-to-day activities
• off-shore oil wells, leaks from pipelines and storage tanks, tankers being washed out, loading/unloading of tankers
• most oil pollution comes from on-land activities

Question 25

effects of oil pollution

Answer 25

• often last 3-15 years
• volatile organic hydrocarbons in oil kill aquatic organisms, esp larval forms
• tar-like globs coat bird feathers & fur of marine mammals; these animals die from loss of body heat or drown
• bottom-dwellers are killed with heavy components sink to sea floor
• recovery in cold water takes longer
• oil slicks on shore negatively impact local economy

Question 26

preventing oil spills

Answer 26

• floating booms, skimmers, absorbent devices
• chemical methods: coagulating agents to clump oil, dispersants to break up slicks
• using bacteria to degrade oil; less expensive, more effective

Question 27

oil pollution act 1990

Answer 27

set up a trust fund of $1mil per spill for cleanup
- by 2015, all american oil tankers must be double hulled

Question 28

reducing non point pollution

Answer 28

• prevent it from reaching bodies of surface water
• reduce soil erosion
• reforestation of watersheds
• cover crops
• reduce fertiliser & pesticide use
• rely more on biological control methods
• clean water act
• effective use of animal wastes
• use of septic tanks
• more effective sewage treatment

Question 29

clean water act

Answer 29

• sets standards for allowed levels of key water pollutants
• requires polluters to obtain permits that specify amounts of pollutants allowed
• experiments with a discharge trading policy (like the cap and trade system)
• requires feedlots to apply for epa permits

Question 30

sewer systems

Answer 30

• can overflow & discharge untreated sewage directly into surface water
• expensive to build and maintain