Published on April 26, 2012
Harini .A Revathi .C Manimala.R: Harini .A Revathi .C Manimala.R OZONE LAYER What is ozone?: What is ozone? Ozone is a special form of oxygen, made up of three oxygen atoms rather than the usual two oxygen atoms. It usually forms when some type of radiation or electrical discharge separates the two atoms in oxygen molecule(O 2 ),which can then individually recombine with other oxygen molecules to form ozone(O 3 ) Ozone : Ozone O 3 = Ozone is composed of 3 oxygen atoms. O 3 inhalation becomes a problem at concentrations greater than 80 parts per billion sustained during a continuous 8-hour period (EPA). O 3 absorbs harmful solar ultraviolet radiation. A necessary condition for life. O 3 is mainly found in the stratosphere. O 3 both heats the stratosphere by absorbing UV and is a greenhouse gas (absorbing and emitting in the Infrared). O 3 concentrations are small (peak concentrations are about 10 parts per million at an altitude of about 32 km (20 miles). Ozone layer : Ozone layer Ozone layer is a deep layer in the stratosphere encircling the Earth that has large amounts of ozone in it. The layer shields the entire Earth from much of the harmful ultraviolet radiation that comes from the sun. Ozone hole The ozone "hole" is really a reduction in concentrations of ozone high above the earth in the stratosphere. The ozone hole is defined geographically as the area wherein the total ozone amount is less than 220 Dobson Units. : Ozone hole The ozone "hole" is really a reduction in concentrations of ozone high above the earth in the stratosphere . The ozone hole is defined geographically as the area wherein the total ozone amount is less than 220 Dobson Units. Ultraviolet light and ozone: Ultraviolet light and ozone Ultraviolet light and ozone: Ultraviolet light and ozone The ozone in the ozone layer is very small it is vitally important to life because it absorbs biologically harmful ultraviolet radiation coming from the sun. UV radiation is divided into three categories based on its wavelength UV-A (400-315mm) UV-B (315-280mm) and UV-C (280-100mm) UV-C which would be very harmful to all living things is entirely screened out by ozone at around 35 sunburn excessive exposure can also cause genetic damage resulting in problems such as skin cancer. Most UV-A reaches the surface this radiation is significantly less harmful although it can potentially cause genetic damage. Effect of ultraviolet radiation: Effect of ultraviolet radiation UV rays penetrate the skin and break down collagen and elastic – the two main components that make up our skin. When the skin is exposed to sunlight the production of melanin, the pigment that gives the skin its color, increases. This pigment prevents damage to a certain extent by absorbing UV rays. However, excessive exposure results in wrinkled and darkened skin. Light-skinned persons and infants are at a higher risk of damage by exposure to the sun. This is due to the insufficient quantity of melanin. Effect of ultraviolet radiation: Effect of ultraviolet radiation What chemicals cause ozone loss?: What chemicals cause ozone loss? Source Chemicals Ozone depletion : Ozone depletion The ozone layer can be depleted by free radical catalysts including nitric oxide, nitrous oxide hydroxyl atomic chlorine and atomic bromine. Recent years due to the large quantities of manmade organ halogen compounds especially chlorofluorocarbons (cfcs) bromofluorocarbons . In 2009 nitrous oxide was the largest ozone-depleting substance emitted through human activities. Ozone depletion: Ozone depletion Stratospheric ozone is necessary since it keeps the Earth’s temperature favorable for life, and protects the Earth from ultra violet radiation. Ozone depletion contributes both to increased ultra violet radiation on Earth and to global climate change. Synthetic chemicals, such as CFCs and halos, are responsible of the stratospheric ozone depletion. Troposphere (ground-level) ozone is very harmful and thus it is defined as an air pollutant. The ground level ozone is a summer pollutant because its formation is faster in warm conditions. The ozone in Antarctica : The ozone in Antarctica The ozone above Antarctica became so thin that scientists began using the term ozone "hole" to describe its alarming depletion. The hole naturally expands and contracts with the seasons. The average total Antarctic ozone level was less than half what it was in the 1970s. By 1998, Antarctic ozone levels reached record lows. The hole had extended to 10.5 million square miles (27 million square kilometers), covering the entire Antarctic land mass and even the southern tip of South America. Over some parts of Antarctica, the total ozone column was depleted by up to 60% during the September through November period the atmosphere and breaks down CFCs. PowerPoint Presentation: Ozone Hole in Antarctica Antarctic ozone hole: Antarctic ozone hole British Antarctic Survey scientists Farman , Gardiner and Shank in Nature the observed decline in polar ozone was far larger than anyone had anticipated Satellite measurements showing massive depletion of ozone around the south pole were becoming available at the same time. However, these were initially rejected as unreasonable by data quality control algorithms the ozone hole was detected only in satellite data when the raw data was reprocessed following evidence of ozone depletion in situ observations When the software was rerun without the flags, the ozone hole was seen as far back as 1976. PowerPoint Presentation: Stratospheric ozone absorbs energy from the ultraviolet part of the solar spectrum, heating the lower stratosphere. This part of the spectrum accounts for less than one percent of the total solar energy reaching our atmosphere. Stratospheric ozone is important because it prevent dangerous ultraviolet rays from harming plants and animals on Earth's surface, but reductions in the amount of radiation absorbed does not have a measurable impact on temperatures below. Does climate change have an impact on the stratospheric ozone layer? : Does climate change have an impact on the stratospheric ozone layer? The thickness of the polar stratospheric ozone layer depends on the rate of production of ozone in the tropical stratosphere, The movement of ozone from the tropics to the poles, the amount of ultraviolet radiation from the Sun, The polar stratospheric cloud cover, and The chemical reactions between the ozone and ozone- depleting substances. Each of these factors might be affected by climate change. PowerPoint Presentation: Is there a connection between the ozone hole and global warming? Global warming is caused primarily from putting too much carbon into the atmosphere when coal, gas, and oil are burned to generate electricity or to run our cars. These gases spread around the planet like a blanket, capturing the solar heat that would otherwise be radiated out into space Both of these environmental problems do, however, have a common cause—human activities that release gases into and alter the atmosphere. Because our atmosphere is one connected system, it is not surprising that ozone depletion and global warming are related in other ways. For example, evidence suggests that climate change may contribute to thinning of the protective ozone layer. Health Facts: Health Facts UV plusses: produces vitamin D in the skin - necessary to maintain levels of calcium and phosphorus (~10-15 minutes twice a week) UV minuses: Eye damage: cataracts, photokerititus (snow blinding), ocular cancers Skin cancers: basal, squalors, melanoma photo aging Damage to various land species Damage to aquatic species Increased pollution levels in urban environments Troposphere ozone is a pollutant: aggravates asthma, reduces lung capacity, and increases susceptibility to respiratory illnesses like pneumonia and bronchitis Can sunlight harm us?: Can sunlight harm us? ‘ Too much of even a good thing is bad’ -- goes an old adage. All of us need a little exposure to sunlight. This helps synthesize Vitamin D, essential for the absorption of calcium in the human body. But too much exposure to sunlight does not translate into heaps of Vitamin D, which the body can store and use. Excess exposure damages the skin and results in blisters, pain and some other symptoms. The possibility of skin cancer: The possibility of skin cancer Damages the DNA of the exposed skin cells. People with lighter skins are more susceptible to skin cancer their skins contain less melanin, which is the skin’s natural way of protecting itself. Genetics also play a role and people with a family history of skin cancer are at a higher risk. REGULATION: REGULATION IN 1978 THE United states Canada and No rway enacted bans on CFCs containing aerosol sprays . After negotiation of an international treaty(the Montreal Protocol) CFC production was sharply limited beginning in 1987 and phased out completely by 1996. since that time the treaty has been amended to ban CFC production after 1995 in the developed countries and later in developing. Today over 160 countries have signed the treaty. What shall we do?: What shall we do? Individually as well we can start eco-drives wherein trees are planted in and around the city. People are made aware of the environmental issues. Saying no to harmful substances by the consumers will limit its production majorly, the perfumes which have CFC as an ingredient should be refused by the consumers. Thus older generation of mankind involved itself with finding the mysteries of Nature and exploiting it. Now after having known the repercussions of the same the new generation has to cut down upon it and preserve the environment for themselves as well as their future generations. What shall we do?: What shall we do? Mahatma Gandhi said,’ Nature can provide for man’s need, but not for his greed’, The world today is stormed with self-inflicted environmental problems. From the emissions of the major industries to a mere starting of a car, the environment is degraded inch by inch. According to a survey, 80% of the people are aware of the environmental problems and out of them only 10% have taken initiatives individually PowerPoint Presentation: References  Staehelin, J., et al. (2001). Ozone Trends: A Review. Reviews of Geophysics 39, 231-290.  Solomon, S. (1999) Stratospheric Ozone Depletion: A Review of Concepts and History. Revs. Geophysics. 37, 275-316.  World Meteorological Organization: Scientific Assessment of Ozone Depletion, 2002: http:// ozone.unep.org /Publications/ index.asp ) (2003)  Farman, J. et al (1985) Large Losses of Total Ozone in Antarctica Reveal Seasonal ClOx/ NOx Interaction. Nature 315, 207. Thank you..: Thank you..