Case Study 7 Major Global Environmental Issues

1
Case Study 7 Major Global Environmental Issues

• 1 Nuclear Waste Disposal
• 2 Greenhouse Effect
• 3 Coral Reefs
• 4 Desertification

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Nuclear Waste Disposal
1

• Nuclear waste
• Nuclear fuel is made of solid pellets of enriched
  uranium.
• One pellet has an amount of energy equivalent to
  almost one ton of coal.
• Fuel will be used until it is spent, or no longer
  efficient in generating heat.
• Once a year, approximately one-third of the
  nuclear fuel inside a reactor is removed and
  replaced with fresh fuel.
• The used fuel is called spent fuel.
• Highly radioactive.
• Must be isolated in a repository for thousands of
  years.
• If not properly isolated, its radioactivity can
  harm people and the environment.

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Nuclear Waste Disposal
1

• Temporarily put into a pool of water at the
  reactor site.
• Water is a radiation shield and coolant.
• Need to find safe, permanent disposal is becoming
  critical.
• At some nuclear power plants, the storage pools
  are almost full.
• Permanent disposal
• Isolate high-level radioactive waste for
  thousands of years.
• Safe for 10,000 years.
• The primary problem has to do with the
  radioactive half-life of nuclear fuels.
• A transgenerational issue into the realm of
  geologic time.

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Nuclear Waste Disposal
1

• Issue
• One of the primary controversies over the use of
  nuclear energy for peaceful purposes.
• About 95 of all radioactive waste comes from
  civilian source uses of nuclear energy.
• More than 50 years of experience using atomic
  energy.
• Lack any safe, permanent means for disposing its
  waste.
• Spent fuel is stored at more than 60 nuclear
  power plants across the country.
• By 2000, 40,000 metric tons of spent fuel have
  been produced.

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Nuclear Waste Disposal
1

• Geologic burial
• Hollowing out a repository a quarter mile or so
  below the surface
• Drill holes in the host rock.
• Place wastes in specially designed containers.
• Place the containers in the holes in the rock.
• Surround the containers with an impermeable
  material such as clay to retard groundwater
  penetration.
• Seal the containers with cement.
• When the repository is full, seal off the
  entrance at the surface.
• Mark it with an everlasting signpost warning
  future generations of its deadly contents.

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Nuclear Waste Disposal
1

• Problems
• Groundwater motion.
• Groundwater seeps into the containers absorb the
  radioactive materials.
• Water tables shift over time so that today's
  situation can change dramatically long before the
  radioactivity has ceased.
• Tectonic activity.
• Can alter the geologic base within which the
  repository site is situated.
• Threaten the encasements of the radioactive
  materials.
• Terrorism.
• Unpredictable outcome but a very real threat in
  many countries.

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Nuclear Waste Disposal
1

• Reprocessing
• Spent fuel is dissolved in acid, separating the
  uranium, plutonium and other fission products.
• The uranium can re-enriched and recycled.
• The fission products are encased in glass and
  stored.
• The plutonium is recombined with uranium 238,
  made into rods and put into reactors.
• The fuel is called mixed oxide, or mox, and
  essentially substitutes plutonium 239 for the
  fissile uranium 235 in first-generation fuel.
• Not permitted in the US since 1977.
• Only France, England and Russia reprocess their
  spent nuclear fuels.

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Greenhouse Effect
2

• Context
• Not by itself a pollutant.
• Natural process permitting to support life.
• Without the greenhouse effect, the Earth would be
  60o F cooler.
• Combined actions of several greenhouse gases
  (notably carbon dioxide).
• Process
• The atmosphere is generally permeable to short
  wave radiations.
• Those radiations are reflected by the earth
  surface as infrared radiations.
• Greenhouse gases absorb and re-emit towards the
  surface.

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Greenhouse Effect
2

• Higher capacity of the atmosphere to retain heat.
• Indirect consequence of
• Carbon dioxide emissions (about 71 of the
  contribution).
• CFCs (3), ozone and methane (8).
• Impacts
• Contributes to global warming.
• Since 1850, levels of carbon dioxide increased by
  25.
• Average temperature increased by one degree
  Celsius.
• By 2050, an additional rise between 1.5 and 4.5
  degrees Celsius could occur.
• Ecosystems may be pushed northward.
• As much as 150-550 km in mid-latitude regions.

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Average Temperature at the Earth's Surface
(Land-based Series), 1866-1999
2
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Global Average Temperature at Earth's Surface and
Atmospheric Concentrations of Carbon Dioxide,
1950-1999
2
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Greenhouse Effect
2

• Rise in sea levels is a potential problem for
  coastal areas where most human activities are
  located.
• Rise of 20 cm during the 20th century.
• Rise of sea levels, between .5 and 1 meter (2 to
  3 feet) by mid 21st century.
• A rise of one meter may flow substantive surface
  of land.
• 70 of Bangladesh could be under water.
• 50 cm 30 million people flooded in the Yangtze
  delta.
• May indirectly affects sea current patterns and
  fishing.
• Fluctuations in weather systems with changes in
  regional and seasonal weather patterns.
• Significant effects on the ecosphere,
  particularly for agriculture.

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Greenhouse effect attributed to human activities
2
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Estimated Climate Factors Change, 1850-2000 (in
watts/m2)
2
15
Share of Global CO2 Emissions, 1996
2
16
Total Carbon Emissions, 1900-1999 (in millions of
tons)
2
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Contribution to Global Warming
2
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The Carbon Cycle
2
Atmosphere
Respiration and assimilation
Respiration
Respiration and assimilation
Respiration
Emission
Ecosphere
Animal activities
Human activities
Lithosphere
Hydrosphere
Limestone
Decomposition
Fossil fuels
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Greenhouse Effect
2

• Acid rain
• Major industrial regions are consuming vast
  amounts of coal and petroleum.
• The outcome is the generation of acid
  precipitation.
• Level of exposition to sunlight influences the
  level of formation of acid (sulfuric and nitric).
• When dissolved in water, sulfuric and nitric
  acids lower the pH (higher concentrations of
  hydrogen ions).
• Standard pH of fresh water ranges between 6.5 and
  7.5.
• Sulfuric and nitric acids are carried over large
  distances through weather systems.
• Acid rain and acid depositions are known to alter
  the ecological balance of continental ecosystems
• Eastern United States and Canada are affected by
  acid precipitation generated by industries along
  the Great Lakes.

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SO2 and NOx Emissions in North America and
Europe, 1980-1994
2
21
Ozone Hole, Antarctica, September 2000
2
South America
Antarctica
New Zealand
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Coral Reefs
3

• Context
• The most complex aquatic ecosystem found on
  Earth.
• Only found between 30 degrees north and south
  latitude.
• Largest concentration is found between 4 degrees
  north and south latitude.
• Support greater numbers of fish and invertebrate
  species than any other ecosystem in the ocean.
• Home to over 25 percent of all marine life and
  are among the world's most fragile and endangered
  ecosystems.

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Coral Reefs
3

• Issue
• More than a quarter of the worlds reefs are at
  high risk.
• Just under a third of these habitats are at
  moderate risk.
• Overexploitation of marine resources, including
  destructive fishing practices, and coastal
  development present the greatest threat.
• In the last few decades, mankind has destroyed
  over 35 million acres of coral reefs.
• 58 of the world's reefs are at risk.
• If the present rate of destruction continues, 70
  of the worlds coral reefs will be killed within
  our lifetimes.

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Coral Reefs
3

• Sedimentation
• Construction along coasts, inshore construction,
  mining or farming upstream, or logging in
  tropical forests.
• Causes soil to erode and rush downstream into the
  ocean and onto coral reefs.
• This dirt, silt, or sand can make the water
  cloudy or muddy, smothering the coral which can't
  get enough light to survive.
• Mangrove trees and seagrasses which normally act
  as filters for sediment are also being rapidly
  destroyed.
• Led to an increase in the amount of sediment
  which reaches coral reefs.
• Mangrove forests are often cut for firewood or
  removed to create open beaches.
• They are also destroyed by prawn harvesters to
  open up areas to create artificial prawn farms.

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Coral Reefs
3

• Fishing with Explosives
• Over-fished reefs and desperate fishermen produce
  a deadly combination when reefs are dynamited to
  harvest small fish.
• Large explosions which kill all the fish in the
  surrounding area and reduce nearby coral to
  lifeless rubble.
• Human Run-off (fertilizers and sewage)
• Encourage rapid algae growth which chokes coral
  polyps, cutting off their supply of light and
  oxygen.
• Over-fishing makes this problem even worse
  because the fish that would normally eat the
  algae have been captured and killed.
• Cyanide Fishing
• Commercial fishing fleets often use cyanide and
  other poisons to stun and capture valuable reef
  fish.
• Method often used to catch tropical fish for
  aquariums and is now used to capture fish for
  live fish restaurants.

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Coral Reefs
3

• Poisons not only the fish, but the coral polyps.
• Philippines
• Up to 400 thousand pounds of cyanide are sprayed
  and dumped onto the reefs each year.
• Less than 10 of the coral reefs in this area
  remain healthy.
• Collection and Dredging
• Removing coral to be used for construction
  material or sold as souvenirs.
• Dredging and dynamiting of coral for
  construction.
• Water pollution
• Petroleum products and other chemicals dumped
  near coastal waters eventually find their way to
  the reefs.
• Oil and gas leaked or spilled near a coral reef
  poison coral polyps and other marine life.

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Coral Reefs
3

• Trash dumped into the water can also kill coral
  reef life.
• Plastic bags get caught in the stomachs of
  turtles and fish, causing them to starve to
  death.
• Trash can also cover coral reefs, blocking off
  the sunlight needed to keep the reefs alive.
• Lost or discarded fishing nets can snag on reefs
  and strangle to death thousands of fish that get
  caught in them.
• Careless recreation
• Careless boating, diving, fishing, and other
  recreational uses of coral reef areas can cause
  damage to coral reefs.
• Dropping anchors onto reefs can crush or break
  coral.
• When people grab, kick, walk on, or collect
  coral, they also contribute to coral reef
  destruction.

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Coral Reefs
3

• Global warming
• Unprecedented increase in the number of coral
  bleaching events during the past 2 decades.
• Most coral reefs could be destroyed by 2050.
• When ocean temperatures get too high, coral
  polyps lose the symbiotic algae inside them,
  causing them to turn white, or bleach, and
  eventually die.
• Lead to more extreme and unpredictable weather.
• An increase in tropical storms could do extensive
  physical damage to coral reef ecosystems.
• Rising sea levels may become a serious threat to
  coral reefs and to small island nations based on
  coral reef atolls.

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Coral Reefs
3
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Degradation of Coral Reefs
3
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Desertification
4

• Context
• 40 of the surface of the earth is either a
  desert or under desertification.
• 55,000 - 80,000 square miles per year (larger
  than Greece).
• Deforestation, climate change, huge population
  growth and over-farming and grazing.
• Desertification in the Sahel
• Roughly a 500-km wide band in Sub-Saharan Africa.
• Includes Gambia, Senegal, Mauritania, Mali,
  Burkina Faso, Niger and Tchad.
• Sudan and Ethiopia can also be considered as part
  of this band.
• Rainfall is scarce in the northern part of the
  band, permitting only grazing.

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Desertification
4

• As we move south, some forms of agriculture are
  possible.
• Precipitation is also highly cyclical with
  periods of droughts and sufficient rainfall.
• Agricultural system is not able to withstand
  demographic growth.
• Agriculture has always been extensive in the
  region
• Poor productivity of the land.
• Left to rest (fallow) for about seven years.
• With demographic growth, all the agricultural
  land is used and soils are loosing their
  fertility.
• Sahara desert gaining ground (several miles per
  year).
• The population is eating the capital instead of
  living off the interests.

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Desertification in the Sahel
4
Mauritania
Mail
Niger
Chad
Senegal
Sudan
Burkina Faso
Ethiopia
Somalia
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Drylands, Mali
4
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Relationships between Demographic Pressure and
Desertification
4
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Desertification
4

• The Amazonian forest
• Brazil is the most populous country of South
  America.
• Population located dominantly along the coastline
  and vast inhabited interior.
• For the sake of national development, the
  Brazilian government is developing the interior.
• A symbolic gesture was done when the Brazilian
  capital was relocated to Brasilia, built from
  scratch.
• Mostly done at the expense of the Amazonian
  forest, the largest rainforest in the world.
• Constructing highways, building dams, and cutting
  down the rainforest to make place for agriculture
  are in the process of destroying a complex
  ecosystem.
• Creation of laterite soils.