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Case Study 7 Major Global Environmental Issues

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Case Study 7 Major Global Environmental Issues. 1 Nuclear Waste Disposal ... If not properly isolated, its radioactivity can harm people and the environment. ... – PowerPoint PPT presentation

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Title: 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

2
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.

3
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.

4
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.

5
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.

6
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.

7
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.

8
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.

9
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.

10
Average Temperature at the Earth's Surface
(Land-based Series), 1866-1999
2
11
Global Average Temperature at Earth's Surface and
Atmospheric Concentrations of Carbon Dioxide,
1950-1999
2
12
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.

13
Greenhouse effect attributed to human activities
2
14
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
17
Contribution to Global Warming
2
18
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
19
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.

20
SO2 and NOx Emissions in North America and
Europe, 1980-1994
2
21
Ozone Hole, Antarctica, September 2000
2
South America
Antarctica
New Zealand
22
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.

23
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.

24
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.

25
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.

26
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.

27
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.

28
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.

29
Coral Reefs
3
30
Degradation of Coral Reefs
3
31
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.

32
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.

33
Desertification in the Sahel
4
Mauritania
Mail
Niger
Chad
Senegal
Sudan
Burkina Faso
Ethiopia
Somalia
34
Drylands, Mali
4
35
Relationships between Demographic Pressure and
Desertification
4
36
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.
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