orientation Presentation1

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Education

Published on March 20, 2009

Author: shivaupadhyay

Source: authorstream.com

Slide 2: 2 Ozone layer Depletion its causes And consequences Learning Objectives : Learning Objectives What is Ozone? The role ozone plays in the Earth’s system. What is ozone Depletion?& Factors causing Ozone depletion. What are its consequences? What should be done? What is ozone? : What is ozone? The ozone molecule contains three oxygen atoms, hence O3 is ozone. Ozone it occurs naturally by the sunlight. Ozone is a pale blue gas irritating to the nose and throat; it is explosive and toxic When found on the surface of the planet, ozone is considered a dangerous pollutant. Ozone in the Atmosphere : Ozone in the Atmosphere Ozone formation : Ozone formation Slide 7:  Good ozone/bad ozone : Good ozone/bad ozone Why is the ozone layer important : Why is the ozone layer important Ozone acts as the Earth’s protective shield against the Sun’s harmful Ultraviolet radiation (UV radiation). Without the ozone layer, life would not exist on Earth! The natural development of the ozone layer permitted life to evolve above water. Ozone in the Atmosphere : Ozone in the Atmosphere Ozone is mainly produced in the tropics because of the higher amounts of solar radiation. Ozone is mainly destroyed at middle and higher latitudes by chemical processes. Ozone is also largely affected by atmospheric winds. Thus, ozone naturally has large variations in space and time. Satellite Ozone Observations : Satellite Ozone Observations The ozone layer for one day : The ozone layer for one day Dobson Units (DU) as a measure of total ozone : Dobson Units (DU) as a measure of total ozone definition of ozone hole: < 220 DU Melbourne Avg. 280-380DU Darwin Avg. 260DU UV radiation : UV radiation UV radiation is emitted from the sun with wavelength from 200-400 nm (nanometers) UV radiation is divided into three ranges UV-A, 320 - 400 nm UV-B, 290 - 320 nm UV-C, 200 - 290 nm The shorter wavelength are more harmful to biological life. Ozone profile with height and UV : Ozone profile with height and UV Typical UV forecast : Typical UV forecast UV radiation : UV radiation What affects the amount of UV radiation hitting the Earth? -Location (latitude) -Time of day -Time of the year -cloud cover Thus, UV radiation naturally has large variations in space and time!!! UV changes during the day : UV changes during the day Satellite UV measurements : Satellite UV measurements July 1, 2000 January 14, 2000 Summary : Summary Ozone is produced and destroyed naturally in the atmosphere (ozone bucket picture). Ozone is responsible for absorbing much of the sun’s harmful UV radiation. UV radiation varies due to time of day, season, cloud amount, and ozone amount. Slide 21: 21 Lesson 2: "The Antarctic Ozone Hole" Learning objectives : Learning objectives To develop an understanding for the history of ozone depletion To develop an understanding for what the ozone hole is. To understanding how the ozone hole is produced. Early concerns about ozone depletion : Early concerns about ozone depletion History of Ozone Depletion : History of Ozone Depletion CFCs developed in 40’s and 50’s Refrigerants, propellants, fire retardants 1970’s CFCs detected in atmosphere. Many of these have long atmospheric lifetimes (10’s to 100’s of years) 1974 Rowland and Molina propose that CFC’s can destroy ozone in the stratosphere. CFCs broken apart by UV radiation forming chlorine which can destroy ozone quickly: O3 +Cl ? ClO+ O2 (Catalytic Reaction) ClO+O ? Cl+O2 History of ozone depletion : History of ozone depletion 1970’s Supersonic Aircraft fleet under review. 1978: CFCs used in aerosols banned. 1985: British Antarctic Survey reports 40% loss of ozone over Antarctica during spring. (NASA confirms) 1987: Signing of the Montreal Protocol International agreement to reduce CFC use Later agreements agreed to completely phase out CFC and halons. 1996 Complete ban on industrial production of CFCs goes into effect. The Ozone Hole : The Ozone Hole First discovered in 1985: observations from Antarctica extend back into 1950’s. Characterized as a rapid depletion of ozone over Antarctica during spring. Ozone hole season, Spring (August – October) Ozone hole located over mainly over Antarctica. Ozone hole recovers by late December Ozone hole caused by human chemicals (CFC’s) Ozone hole not present in early 1970’s Total Ozone: October 14, 1997 : Total Ozone: October 14, 1997 Where is the ozone hole? : Where is the ozone hole? Ozone hole largely restricted to areas over Antarctica Ozone hole may pass over tip of South America Ozone hole seldom comes near Australia. Northern Hemisphere (NH) has no ozone hole like the Southern Hemisphere However, recently NH has experienced the occurrence of ozone ‘mini holes’. Satellite Total Ozone from 70’s and 90’s : Satellite Total Ozone from 70’s and 90’s Ozone observations over Antarctica : Ozone observations over Antarctica Is the ozone hole getting worse? : Is the ozone hole getting worse? Animation : Animation Ozone Hole Recipe : Ozone Hole Recipe Ingredients: Chlorine gas Cold Temperatures (~-80C) Instructions: Allow cold temperatures to form Polar Stratospheric Clouds (1-2 weeks). Allow time for polar stratospheric clouds to convert chlorine gas into ozone destroying chemicals. (1 month) Bake ingredients with sunlight. Presto, a delicious ozone hole! Science interpretation Chlorine gas is abundant in atmosphere due to CFC’s Cold Temperatures (~-80C) only occur over Antarctica during the cold winter. Polar Stratospheric Clouds allow ozone friendly chlorine to be transformed into ozone destroying chlorine. Ozone depletion then starts when sun returns to Antarctica in the spring Ozone hole grows from late August through till October. Slide 34: Chlorine gas Cold Temperatures T~-80C Polar Stratospheric Clouds Ozone destroying chemicals Everywhere in Atmosphere Sunlight Ozone Hole produces and Only during spring Only during winter and produces produces Ozone Hole Formation Summary : Summary The Ozone hole develops during spring over Antarctica. The Ozone hole is produced by unique combination of weather (cold temps) and chemistry (chlorine). Global ozone trends are negative except in the tropics. Slide 36: 36 Lesson 3 "Ozone Depletion, Skin Cancer and Australia" Outline : Outline How does ozone depletion affect Australia? Why does Australia have the highest rate of skin cancer globally? Skin cancer risk factors What are the consequences of an ozone depleted world? : What are the consequences of an ozone depleted world? With ozone depletion, there will be higher rates of UV radiation. More UV radiation rates mean Higher rates of skin cancer Higher amounts of cataracts Possible danger to plant and animal life Recall: Without the ozone layer, life on the Earth’s surface would not exist!!! How does ozone depletion affect Australia? : How does ozone depletion affect Australia? Global ozone trends? Ozone Hole? Global Ozone Trends : Global Ozone Trends Most of Australia does not have large negative ozone trends How does ozone depletion affect Australia? : How does ozone depletion affect Australia? Is the ozone hole over Australia? No, not even close! … then why does Australia have the highest rate of skin cancer? : … then why does Australia have the highest rate of skin cancer? Naturally high levels of UV radiation in Australia Australia has a light skin-type population Lifestyle choices (suntan, outdoor hobbies etc.) Skin Cancer Risk Factors : Skin Cancer Risk Factors High Risk Low Risk Skin type: Light skin Dark skin Environment: Tropics High Latitudes Occupation: Outdoor Indoor Social factors (i.e. hobbies etc.) Australia is in a high sunlight environment!!! : Australia is in a high sunlight environment!!! Skin Cancer and Ozone Depletion : Skin Cancer and Ozone Depletion Most skin cancer is attributed to exposure 20 or more years ago (before ozone depletion). The younger generation of today will face higher risks in the future due to current decreases in ozone levels and increases in UV (~5-10%). Ozone depletion and global warming : Ozone depletion and global warming No direct connection between these environmental issues. However: Global warming may enhance ozone depletion global warming produces Tropospheric warming & stratospheric cooling Therefore, if the stratosphere cools, then ozone destroying chemistry (e.g. ozone hole), will increase. Summary : Summary Many factors influence skin cancer such as A sun smart lifestyle! Slide 48: Ozone Depletion Significant concentrations of ozone (O3) exist in the lower elevations of the stratosphere. Ozone in the stratosphere absorbs UV B radiation from sunlight. UV B radiation damages DNA molecules and can cause genetic defects on the outer surfaces of plants and animals, including human skin (skin cancer) Slide 49: Ozone Depletion Results Each 1% loss of ozone leads to a 2% increase in UV radiation striking the earth. A 2% increase in UV radiation results in a 5% to 7% increase in skin cancer, including a 1% increase in deadly malignant melanoma Slide 50: A 5% Ozone Depletion would cause: An additional 940,000 cases annually of basal-cell and squamous-cell skin cancer (disfiguring, but not usually deadly) An additional 30,000 cases annually of melanoma skin cancer (often fatal). There are 9,000 American deaths per year from this now. A sharp increase in eye cataracts and severe sunburn in people, cataracts in cattle. Suppression of the human immune system An increase in smog. The EPA estimates a 1% decrease in stratospheric ozone causes a 2% increase in ozone near the ground Reduced yields from crops like corn, rice, beans, and wheat Reduction in ocean phytoplankton growth Loss of $2 billion per year from materials degradation Increased global warming Slide 52: Causes of Depletion Chlorine and Bromine in the Stratosphere CFC-11 (chlorofluoromethane) and CFC-12 (dichlorofluoromethane) are the most widely used as coolants for refrigerators and air conditioners Slide 53: CFC-11 (chlorofluoromethane) and CFC-12 (dichlorofluoromethane) are the most widely used as coolants for refrigerators and air conditioners Sources Chlorofluorocarbons (CFC’s) Commonly called Freons (a Du Pont Chemical tradename) Also used as propellant in aerosol cans, industrial cleaner, hospital sterilant, fumigant, and to create bubbles in polystyrene plastic foam used for insulation and packaging. Halons Bromine containing compounds used in fire extinguishers Carbon Tetrachloride An industrial solvent Methyl Chloroform Solvent, correction fluid, dry cleaning spray, spray adhesive Slide 54: United States accounts for largest part of world-wide consumption o CFC’s 29% of global consumption is from US Americans use six times more CFC’s than global average Vehicle air conditioners accounted for about 75% of annual CFC emissions in the US in 1990 Since 1978 the use of CFC’s in aerosol cans has been banned in many countries; however, worldwide, aerosol cans still account of 25% of CFC emissions Slide 55: What do these compounds do? Spray cans, discarded and/or leaking refrigeration and air conditioning units, the production and burning of plastic foam products, and the use of solvents result in the release of these compounds into the environment. Most of these compounds are non-reactive and have lives of 22 to 111 years in the atmosphere. They circulate in the atmosphere until they reach the stratosphere. In the stratosphere they are broken down by UV radiation to release chlorine and bromine atoms Chemical reactions between chlorine or bromine and ozone cause ozone to degrade to O2 and O. Over time a single chlorine atom can cause the breakdown of as many as 100,000 molecules of ozone. Slide 56: The Ozone Hole In the 1980’s researchers discovered that up to 50% of the ozone in the stratosphere over Antartica is destroyed between September and October (Arctic Spring). An area larger than the US Cause Vortexing winds with ice crystals that have absorbed CFC’s on the surface that lift CFC’s into the stratosphere and destroy the ozone at a fast rate. The vortex breaks up in a couple of months and large masses of ozone depleted air flow northward over parts of Australia, New Zealand and southern South America. During this time UV levels increase by as much as 20% there. A similar phenomenon has recently been observed in the Arctic regions Slide 57: Satellite photo of south pole. Purple shade shows the extent of the ozone hole. Slide 58: Ozone Depletion Observations Average drops in Ozone levels between 1969 and 1986 Slide 59: Protecting the Ozone Layer Ban the use of CFC’s Have to replace with something Current replacements are greenhouse gases and do not eliminate ozone depletion, just slow it down Slide 60: Indoor Air Pollution Slide 61: Air Quality Standards Emission Standards Limit amounts of pollutants that can be emitted by pollution sources Generally set by State Air Quality Offices Slide 62: Ambient Air Quality Standards The Clean Air Act, which was last amended in 1990, requires EPA to set National Ambient Air Quality Standards for pollutants considered harmful to public health and the environment. The Clean Air Act established two types of national air quality standards. Primary standards set limits to protect public health, including the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings.   The EPA Office of Air Quality Planning and Standards (OAQPS) has set National Ambient Air Quality Standards for six principal pollutants, which are called "criteria" pollutants. They are listed below. Units of measure for the standards are parts per million (ppm) by volume, milligrams per cubic meter of air (mg/m3), and micrograms per cubic meter of air (µg/m3). Slide 64: http://www.epa.gov/oar/oaqps/peg_caa/pegcaain.html#index A guide to the Clean Air Act may be found at the EPA website: Slide 66: 66 Lesson 4 "Ozone Depletion:  The future?" Outline : Outline What are current levels of ozone depletion? Is the ozone hole getting worse? What has been done about ozone depletion? What is going to happen in the future? Global Ozone Trends : Global Ozone Trends Most of Australia does not have large negative ozone trends How has ozone changed over other parts of the Earth? : How has ozone changed over other parts of the Earth? Globally, ozone has been decreasing over the last 15 years. Largest ozone change over Antarctica ~ -8% per decade or more No ozone change over Tropics Over Australia Melbourne: decreasing at 2-3%/decade Darwin: No significant change Is the ozone hole getting worse? : Is the ozone hole getting worse? What is being done about ozone depletion? : What is being done about ozone depletion? Montreal Protocol (1988): international agreement to phase out ozone depleting chemicals Further amendments accelerated the phase out. Developed countries have switched to HCFC’s (more ozone friendly) instead of CFC’s. Developing countries has until 2010 to phase out CFC’s. Is the Montreal Protocol working? : Is the Montreal Protocol working? Observations indicate that chlorine is beginning to decline in the atmosphere. (Good news!) Still large uncertainties about illegal trade/use of CFC’s (??’s) Future Atmospheric models suggest that: atmospheric chlorine will return to pre-80’s in next 50 to 100 years. a slow ozone recovery will follow decreasing chlorine concentrations What is going to happen in the future? : What is going to happen in the future? Model simulations suggest: atmospheric chlorine will return to pre-80’s in next 50 or more years. a slow ozone recovery will follow decreasing chlorine concentrations Still many questions!!! Phase out and use of CFC’s Contribution from global warming Graph of CFC’s levels starting to fall off : Graph of CFC’s levels starting to fall off Chlorine in the future? : Chlorine in the future? Potential Chlorine growth : Potential Chlorine growth Ozone depletion and global warming : Ozone depletion and global warming No direct connection between these environmental issues. However: Global warming may enhance ozone depletion global warming produces Tropospheric warming & stratospheric cooling Therefore, if the stratosphere cools, then ozone destroying chemistry (e.g. ozone hole), will increase. What are the consequences of an ozone depleted world? : What are the consequences of an ozone depleted world? With ozone depletion, there will be higher rates of UV radiation. More UV radiation rates mean Higher rates of skin cancer Higher amounts of cataracts Possible danger to plant and animal life Recall: Without the ozone layer, life on the Earth’s surface would not exist!!! Summary : Summary The international community has a plan to phase out CFC’s in the atmosphere. So far, it looks like it’s working! Current predictions indicate that ozone will recover in next 50-100 years.

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