Ppt 2
Transcript of Ppt 2
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Global CFC production
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Ozone hole in Southern hemisphere October 1979 &
1998
• Monthly means of total ozone in the Southern Hemisphere observed with TOMS
• Images for October of 1979 (left) and 1998 (right).
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Ozone hole: size by month
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Ozone hole measurements over the Antarctic region
1980-98
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Ozone concentration at the center of ozone hole
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Ozone hole over continents: comparison
1996
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Image of the ozone hole over the South pole: July
10 2003
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Image of the ozone hole over the North pole: July
10 2003
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Ozone status: full day global image, July 9th 2003
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Dynamic Equilibriumcreation of ozone
breakdown of ozone
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Anthropogenic Ozone Depletioncreation of ozone
breakdown of ozone
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Effects of UV rays on Aquatic Ecosystems
Ozone depletion causes increases in UV rays’s effects on aquatic ecosystems by:
1. decreasing the abundance of phytoplankton – affects the food stock for fishes and the absorption of CO2
2. decreasing the diversity of aquatic organisms – reduces food stock and also destroys several fish and amphibians.
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Effects of UV rays on Terrestrial Ecosystems
• Damage to plant cell DNA molecules - makes plants more susceptible to pathogens and pests
• Reductions in photosynthetic capacity in the plant - results in slower growth and smaller leaves
• Causes mutations in mammalian cells and destroys membranes
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Harmful effects of UV rays on people
• Skin cancer
• Premature aging (photoaging) of the skin (different from normal chronological aging)
• Cataracts and eye disorders (corneal sunburn and blindness)
• Immune system damage
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Correlation between Ozone depletion and skin
diseases
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The Ultraviolet Exposure Index
INDEX VALUES EXPOSURE
0 – 2 = Minimal 3 - 4 = Low
5 - 6 = Moderate 7 - 9 = High
10 + = Very High
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Factors affecting UV exposure
• Clouds cover - partly cloudy days do little to reduce UV exposure but rainy or substantially overcast days reduce UV exposures
• The time of day – peak exposure time is 12:00 noon - 1:00 p.m. UV intensity is reduced by about half at three hours before and three hours after the peak exposure time.
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Factors affecting UV exposure..2
• The time of year - more UV is received in the late spring and early summer and much less is received in the late fall and early winter.
• Life style – determines a person’s risk to UV exposure. Skiing, sunbathing, or swimming can lead to extremely high exposures. Use of tanning parlors also increase risk.
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Ozone Layer Depletion: Historical Perspective
• The ozone 'hole', it is really not a hole but rather a thinning of the ozone layer in the stratosphere. We will use the term 'hole' in reference to the seasonal thinning of the ozone layer.
• The appearance of a hole in the earth's ozone layer over Antarctica, first detected in 1976.
• 1974: Rowland & Molina theorize CFCs destroy stratospheric ozone molecules
• 1975: U of M / Harvard papers predict that CFCs deplete Earth’s ozone layer
• 1985: Ozone holes found over Antarctic • 1988: Ozone layer thinning over North Pole • 1993: Thinning over mid-latitudes of the Northern Hemisphere • 1997: Low values of total ozone occur in Arctic as well as Antarctic
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Antarctic Ozone Hole Progression
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CH4 itself is an important greenhouse gas, and links climate with air pollution via its influence on tropospheric ozone
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CONTINENT 1 OCEAN CONTINENT 2
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Ozone Layer Depleting Chemicals
• chlorofluorocarbons (CFCs)carbon tetrachloride (CCl4)methyl chloroform (CH3CCl3)hydrochloric acid (HCl)methyl chloride (CH3Cl)methyl bromide(CH3Br)
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International Response to Ozone Layer Depletion
• 1985: United Nations Environment Program (UNEP)• 1987: The Montreal Protocol• 1992: Copenhagen Amendments• 1998: The Montreal Protocol is affecting stratospheric
chemical composition. • 1999-2000: Stratospheric ozone layer recovery will be a
slow process and extend into the next century.Scientific Assessment of Ozone Depletion: 1994 and 1998 (World Meteorological Organization).
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Ozone Layer Depleting Chemicals: CFCs
• CFCs are inert, nonreactive, nontoxic, nonflammable.
• Human-made CFCs used in:- refrigeration- air conditioning- foam blowing- cleaning electronic components- solvents
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Biological Effects of Ultraviolet Radiation
• Sunburn,Premature Aging & PreCancer
• Cancer of Skin-Basal and Squamous Cell Carcinoma-Melanoma
• Cataracts
• Photosensitivity
• Immune system changes
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Human Immune System can be suppressed by ultraviolet radiation• suppression of immune system
• increased incidence of infection
• promotion of cancer growth
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Good & Bad Effects of Sunlight
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Modern Impacts to Ozone (2)
Methyl Bromide
• What is it?
• Challenges to Montreal Protocol
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Methyl Bromide
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Uses of Methyl Bromide
60 million lbs /yr in US
• Agricultural (75%)– Strawberries
• Stored products (11%)
• Flame retardants (6%)
• Pest management (6%)– Termite removal
• Chemical production (2%)
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Schedule for Elimination
1991: Designated Class I ozone depleter in Montreal Protocol
1997: Agreed to following schedule
Developed Countries—elimination by 2005
Developing Countries—elimination by 2015
Requests for “Critical Use Exemptions”
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US Strawberry Industry
• US supplies 80% of plants from nurseries or strawberries to world market
• Average consumption:
4 lb/person/yr
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Benefits of Methyl Bromide
• Worker safety – Non-toxic
– Reduces need for toxic pesticides
• Economical• Easy-to-Use • Effective
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Alternatives
• Fumigants applied through drip irrigation
• Harnessing “good microbes”
• Composting for weed suppression
• Soil solarization• Crop rotation
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Effectiveness
• Other fumigants do not work
• Worker health issue• Lower yields • Loss of nurseries
– Even organic farms get plant stocks from nurseries that rely on methyl bromide
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CFCs vs MEBr
Why did one industry eventually support ban while another is struggling and begging for exemptions?
Methyl Bromide CFCs-no viable alternatives -DuPont developed HFCs
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Another potential threat?
Hydrogen Fuel Cells
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Production of Hydrogen
• Anticipate that 10% of all hydrogen manufactured will leak into the atmosphere during production, storage and transport.
• Current loss is higher
• Estimate: 60 million tons / year
• Roughly doubles current input (all sources)
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Hydrogen chemistry
• Hydrogen is light—rises rapidly to stratosphere
• Reacts with oxygen to form water
• A “wetter” atmosphere would cool the lower stratosphere, especially around Poles
• Increase in water vapor is catalyst for ozone depletion by freeing Cl free radicals
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Spatial and Temporal Patterns
• Poles have greater ozone loss than other regions:– Colder– More vapor formation– Also: polar vortex
• Particularly severe in polar spring (October)• Increased hydrogen would enhance this
phenomenon
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Ozone Layer Impacts
• 7-8% depletion around Poles anticipated
• Depends upon if and how quickly hydrogen economy introduced
• If >50 years, may not be critical issue
• Possible work to lessen H leakage
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Current Status of Ozone Hole
Extent of ozone depletion:
1981— 900,000 sq mi
2001—17,100,000 sq mi
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Location of Ozone Losses
Ozone loss extends beyond Antarctica and Arctic Polar regions
Ozone loss over US currently 5% below normal rates
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Current Rate of Ozone Depletion
• Decrease in rate of ozone depletion (since 1997)• Slowing of buildup of harmful Cl- from CFCs• Ozone hole is still growing, but…
Models anticipate restoration of “normal” balance of ozone in stratosphere by 2050
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Impacts of Ozone Depletion
Human Health • Skin cancer• Melanoma• Cataracts• Immune system function• Increased incidence,
severity and duration of infectious diseases
• Reduced efficacy of vaccinations
Ecological Health• Pathogen locally up &
down• Biodiversity locally up &
down• Aquatic organisms
adversely impacted• Decreased biomass
productivity • Polar systems especially
vulnerable
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Impacts of Ozone Depletion
Economic• Plastics
– designed with stabilizers to withstand UV radiation of certain intensity
– replacement of key medical equipment and supplies, decreased lifespan of plastics
• Manufacturing practices• Agriculture• Consumer costs and burdens
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Breakdown of Sources
Sterilization 3%
Aerosols5%
Refrigeration and Air
Conditioning30%
Other P roducts 12%
Solvent Cleaning P roducts
36%Foam P roducts14%
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