Effects of Ozone Depletion: Effects of Ozone Depletion The Discovery: The Discovery Team who discovered the hole 1985.
From left: Joe Farman, Brian Gardiner, and Jonathan Shanklin British Atlantic Survey Research station, Holly Bay, Antarctic coast In 1985, using satellites, balloons, and surface stations, a team of researchers had discovered a balding patch of ozone in the upper stratosphere, the size of the United States, over Antarctica. Total Ozone Mapping Spectrometer (TOMS):
Artist's view of the QuikTOMS spacecraft (image credit: NASA) Total Ozone Mapping Spectrometer (TOMS) Used by NASA to measure ozone concentrations
TOMS – a satellite-borne instrument
TOMS launched in 1996 – makes 35 measurements every 8 seconds
Levels of ozone are measured in Dobson units (DU), where 100 DU is equivalent to a 1 millimeter thick layer of pure ozone Earth’s Atmosphere: Earth’s Atmosphere Slide5: Ozone is a triatomic form of oxygen (O3) found in Earth’s upper and lower atmosphere.
The ozone layer, situated in the stratosphere about 15 to 30 km above the earth's surface.
Ozone protects living organisms by absorbing harmful ultraviolet radiation (UVB) from the sun.
The ozone layer is being destroyed by CFCs and other substances.
Ozone depletion progressing globally except in the tropical zone. The ozone layer www.epcc.pref.osaka.jp/apec/ eng/earth/ozone_layer_depletion/susumu.html Hole Formation Based on Two different mechanisms::
Movement of air from one place to another in the upper stratosphere
Cold temperature in the upper atmosphere causes nitric acid to freeze into crystals forming wispy pink clouds
Forms a vortex of tightly twisted winds thus forming a hole in the upper atmosphere Hole Formation Based on Two different mechanisms: Chemical Mechanism : Chemical Mechanism Different chemicals are responsible for the destruction of the ozone layer
Topping the list :
man-made, non-toxic and inert in the troposphere
In the stratosphere are photolysed, releasing reactive chlorine atoms that catalytically destroy ozone Slide8: A combination of low temperatures and elevated chlorine and bromine concentrations are responsible for the destruction of ozone in the upper stratosphere thus forming a “hole”. (Kerr, 1987) www.met.sjsu.edu/~cordero/ education/education.htm Slide10: Ozone levels over North America (USEPA, March 1994)
Comparing the colors of the bands over a particular city, such as Seattle, shows lower ozone levels in 1994 than in 1979
Over the U.S., stratospheric ozone levels are about 5 percent below normal in the summer and 10 percent below normal in the winter
(U.S.E.P.A. 1994) www.epa.gov/air/airtrends/ aqtrnd95/stratoz.html No Data No Data Stratospheric Ozone and Ultraviolet Radiation (UVR): Stratospheric Ozone and Ultraviolet Radiation (UVR) Ultra-violet radiation (UVR) high energy electromagnetic wave emitted from the sun. It is made up of wavelengths ranging from 100nm to 400nm.
UV radiation includes UV-A, the least dangerous form of UV radiation, with a wavelength range between 315nm to 400nm, UV-B with a wavelength range between 280nm to 315nm, and UV-C which is the most dangerous between 100nm to 280nm. UV-C is unable to reach Earth’s surface due to stratospheric ozone’s ability to absorb it. (Last, 2006)
Too much ultra-violet light can result in:: Too much ultra-violet light can result in: Skin cancer
Eye damage such as cataracts
Immune system damage
Reduction in phytoplankton
Damage to the DNA in various life-forms
this has been as observed in Antarctic ice-fish that lack pigments to shield them from the ultra-violet light (they've never needed them before)
Possibly other things too that we don't know about at the moment Slide13: Effects of UV radiation on biological organisms
DNA damage ………………………….. Maximum effect on small and single cell organisms
Impaired growth and photosynthesis ...poor crop yields
Phytoplankton: ………………………...Reduced uptake of CO2
…………………………………………..Impaired reproductive capacity
Nitrogen-fixing soil bacteria…………. Reduced, damaged
Human health effects:
Suppressed immune system……………..Enhanced susceptibility to infection
…………………………………………..Increase risk of Cancer
…………….………………………….....Loss of skin elasticity (Premature aging)
Neoplasia (cancer)……………………....Melanocytic (malignant melanoma)
…………….………………………….....Squamous cell skin – cancer
…………….……………………………Basal skin – cancer
Still questionable if causes lip cancer or cancer of
the salivary glands
Aquatic Ecosystems: Aquatic Ecosystems www.ciesin.org/docs/ 011-558/011-558.html oceancolor.gsfc.nasa.gov/. ../phyto_zoo.jpg Krill Phytoplankton: Phytoplankton UV-B penetrates water columns to depths of 30m
Increased UV-B exposure
Reduces productivity by interfering with processes of photosynthesis
Alters nitrogen metabolism
Studies (1993) conducted in the Weddle Sea
Evaluated effects of photosynthesis to UV exposure in the presence of vertical mixing, found:
photosynthesis by phytoplankton was strongly inhibited near the surface of the water
rapid mixing, photic zone is extended, severe inhibition of photosynthesis Bacterioplankton: Play critical role in aquatic system
Decomposers - absorb dissolved organic carbon and recycle it back into the environment
Primary producers – found at the center of food web
Prone to UV-B stress
Interferes with mechanisms for nitrogen fixation and carbon dioxide fixation
Effects dependent on:
Where found in the water column
Amount of exposure
Amount of protection when moving from one mixing layer to another
Pigmentation – absorb more than 90% of UV-B before it penetrates to the genetic material
Form external filaments which protect them from excess UV-B Bacterioplankton Macroalgae and Seagrasses: Macroalgae and Seagrasses Are sessile and restricted to growth site
Have diverse habitats
Above tidal zones
Some never exposed to air
Have adapted to varying solar exposure
Able to protect themselves from excessive radiation using mechanisms of phototinhibition
mechanisms (electron transport) decrease photosynthesis during excessive radiation
Plants: Plants Slide19: The influence of the UV-B radiation on plant process. Environmental Effects of Ozone Depletion: 1994 Assessment DNA & UV-B: DNA & UV-B DNA absorbs UV-B radiation
Changes shape in DNA
Changes in the DNA molecule mean that enzymes cannot “read” the DNA code
Results in mutated cells or the cells die
Cells have developed the ability to repair DNA
A special enzyme arrives at the damage site
removes the damaged section of DNA
replaces it with the proper components
This makes DNA somewhat resilient to damage by UV-B Higher Plants: Higher Plants Experiments were done to determine if increased UV-B is a threat to terrestrial vegetation:
High UV-B exposure does induce some inhibition of photosynthesis
Studies found no significant effects on photosynthetic productivity
Some researchers have concluded that ozone depletion and increase of UV-B not a direct threat to photosynthetic productivity of crops and natural vegetation (Allen, 1998) Difficult to Unmask UV-B Effects: Difficult to Unmask UV-B Effects Limitations in controlled and field studies include:
Large differences in temperature, precipitation, soil types from year to year and in different locations
UV-B radiation masked by other stresses of land plants such as drought
Drought produces large reductions in photosynthesis and growth masking the effects of UV-B
Water stressed plants produce a high concentration of leaf flavonoids (for pigmentation) providing greater UV-B protection Environmental Effects of Ozone Depletion: 1994 Assessment Flowering: Flowering UV-B radiation can alter both the time of flowering as well as the number of flowers in certain species.
Differences in timing of flowering may have important consequences for the availability of pollinators.
The reproductive parts of plants, such as pollen and ovules are well shielded from solar UV-B radiation. Can plants protect themselves against increased UV-B?: Plant adaptation:
Have UV shielding
Only a small proportion of the UV-B radiation striking leaf penetrates into the inner tissues
When exposed to increasing amounts of UV-B, many species of plants can increase the UV-absorbing pigments in their tissues
Other adaptations include:
Increased thickness of leaves reducing the proportion of inner tissues exposed to UV-B radiation
Have repair mechanisms in plants
includes repair systems for DNA damage Can plants protect themselves against increased UV-B? www.unep.ch/ozone/faq-env.shtml - Amphibians: Amphibians Global Decline Seen In Amphibians: Global Decline Seen In Amphibians Range of explanations as to why amphibians are declining, which include:
Introduction of exotic species
Environmental contaminants and other aspects of global climate change
UV-B radiation is still high on the list for the decline in amphibians seen around the world: UV-B radiation is still high on the list for the decline in amphibians seen around the world Causes damage to many species of amphibians at every stage of their life cycle, from egg to adult
Affects growth and development in larvae
Changes in behavior
Make amphibians more vulnerable to disease and death
In adults, causes retinal damage and blindness
UV-B Effects on Human Effects: UV-B Effects on Human Effects Effects on Human Health: Effects on Human Health Over exposure may:
Increase risk of non-melanoma and malignant melanoma skin cancer
Higher risks of malignant melanoma from severe sunburns – especially in childhood
Risk of malignant melanoma has increased 10%
Risk of nonmalignant melanoma has increased 26%
www.ldeo.columbia.edu/.../ lectures/ozone_health/ Over Exposure: Over Exposure Suppress immune system
Accelerate aging of skin due high exposure
Cause an outbreak of rash in fair skinned people due to photo allergy – can be severe dermis.multimedica.de/.../ en/13007/image.htm Skin Protection: Skin Protection Protect the skin against the solar radiation using skin creams with SPF
The greater the numerical value of the SPF the greater the protection
Use lip balm with SPF
Cover up Over Exposure to UV-B….: www.ldeo.columbia.edu/.../ lectures/ozone_health cornea is encountered first then the lens vitreous humor Increases the risk of cataracts
Induces type of protein that provokes cleaving (splitting) in the lens
Leading cause of blindness
The prevalence of cataract after age 30 is doubling each decade
A wedge-shaped growth over the central cornea Over Exposure to UV-B…. Manifestations of…: Manifestations of… Cataracts Pterygium Cancer brought on by over exposure to UV-B Protection: Protection Sunglasses with 100% UV block
Wrap around sunglasses
Eye protection for children
Hats What Is Being Done to Counter the Effects of Ozone Depletion?: What Is Being Done to Counter the Effects of Ozone Depletion? Montreal Protocol (adopted in 1987) – panel of experts was formed to investigate substances responsible for hole formation
Established policies that prevent future use of certain types of chemicals
Stipulated that the production and consumption of compounds contributing towards depletion of ozone in the stratosphere were to be phased out by the year 2000 (2005 for methylchloroform) The Environmental Protection Agency (EPA): The Environmental Protection Agency (EPA) Responsible for enforcing the Montreal Protocol within the U.S.
The EPA has several programs in place;
Regulating and enforcing on-road car and truck air-conditioning systems
Regulating most air-conditioning and refrigeration appliances
Signs of Recovery???: Signs of Recovery??? There have been some signs of recovery
1997 satellite showed a decline of several known ozone-depleting gases
Satellite images show some slowing down of ozone loss
However…. www.coolantarctica.com/. ../ozone_hole.htm Recovery is slow Antarctica - Dec. 2005 Slide38: Images of Antarctica Taken Indicate A Slow Recovery
Understanding the future : Understanding the future Researchers would like to see:
Stations that measure levels of ozone and surface radiation changes in relation to incidence rate of skin cancer and cataracts - installed in urban areas and in remote regions far from populations
More studies to determine biological effects (including human) on UVR exposure
Research on protective creams and ointments and their efficiency in preventing skin cancer and malignant melanoma
More surveillance of UV-related damage to other species living in high latitudes for example….. Reports of Sheep in Iceland developing eye disease – no research to support: Reports of Sheep in Iceland developing eye disease – no research to support (Last, 1993) Future Evolution of Ozone: Future Evolution of Ozone Remains unclear
Current models are unable to reproduce ozone variability accurately
Rates of future increases in greenhouse gases are not yet established
Interactions between ozone depletion and climate change not yet fully understood
Continued monitoring of ozone and ozone-depleting substances is essential
Ozone layer recovery expected by 2050
Hinges on the complete elimination of atmospheric ozone-depleting substances
Replacements for HCFCs, methyl bromide, and halons are still being sought, and studies of the new compounds must continue (U.N.E..P. Progress Report, 2003)
Summing It All Up: Summing It All Up The Ozone is Earth’s only defense against harmful UVR
Studies indicate ozone thinning throughout the globe due to 2 mechanisms:
Research indicates microorganisms, are extremely sensitive to increasing UV-B levels
There is a lot of uncertainty and debate among researchers as to the degree in which land plants are affected by UV-B
There is debate in the scientific community in the role UV-B radiation plays on the decline of amphibians seen globally
In the last decade, there has been an increase in skin cancer and cataracts all related to increase UV-B exposure Efforts Need to Be Continued: Efforts Need to Be Continued Create reliable models
To gain a better understanding of the effects ozone depletion has on organisms living within different ecosystems
Enforcement of Montreal Protocol
To reduce concentrations of chemicals responsible for ozone depletion
Monitoring chemicals being emitted
Gain a better overall understanding on just how ozone depletion is affecting our planet
... Questions: Questions What are the 2 mechanisms responsible for ozone depletion? Explain each mechanism.
Explain 4 effects of ozone depletion.
What efforts have been implemented to counter the effects of ozone depletion? Are there any signs that these efforts are working?
What are some things scientist would like to see done in order to gain a better understanding on the effects of ozone depletion?
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