Outline of Presentation What is the Ozone layer? How is ozone created and destroyed? What is the Ozone hole? What are the causes of Ozone Depletion? Outline of Presentation What are Ozone Depleting Substances? Effects of the depleting Ozone to humanity and all living things. Impacts of the Ozone Layer depletion to the Earth. How can the Ozone layer be saved? The Ozone Layer is a thin, fragile shield that envelops the entire earth which efficiently and effectively filters and screens almost all of the harmful ultraviolet rays. Ozone is a gas that is naturally present in the atmosphere. It is a molecule made up of three oxygen atoms. air molecules It’s chemical symbol is O3. Earth’s atmosphere is divided into four layers with different elevation and temperature profile: 1. Troposphere 2. Stratosphere 3. Mesosphere 4. Thermosphere THE GOOD AND BAD OZONE The Solar Radiation The Earth’s atmosphere is exposed to radiation from the sun. Energy is transferred from the sun to the earth in the form of electromagnetic energy. Electromagnetic energy can be divided into spectrum, in which protons that transfer energy have both a wavelength and energy level. This radiation includes ultraviolet, visible and infrared radiations. There are three categories of UV: UV-A: Most UV-A is able to reach the earth’s surface. UV-B: 90% of UV-B is blocked off by the ozone layer. UV-C: 100% of UV-C is blocked off by the ozone layer. HOW OZONE IS CREATED IN THE STRATOSPHERE How ozone is naturally destroyed in the Stratosphere UV radiation strikes ozone molecule… … releasing one oxygen atom O O O O O O What is the The depletion or the loss of the blocking effect of the ozone layer against ultraviolet rays is what we call the OZONE HOLE. The Ozone Depletion Degradation of the Ozone Layer. When even a small amount of ozone layer is lost, more ultraviolet light from the sun can reach and destroy the Earth. Caused by the chemical reaction involving chlorine and bromine which are also called Ozone Depleting Substances (ODS). OZONE DEPLETING SUBSTANCES (ODS) AND THEIR USES CHLOROFLUOROCARBONS or CFCs HALONS • Simple chemicals containing chlorine, • Contain at least one bromine atom fluorine and carbon. • CFCs are used in refrigerators, air- • Halons are primarily used in fire conditioners, spray cans, solvents, extinguishers foams, other application. OZONE DEPLETING SUBSTANCES (ODS) AND THEIR USES CARBON TETRACHLORIDE and METHYL CHLOROFORM are used as solvents. HYDROBROMOFLUOROCARBONS extinguishers. (HBFCs) HYDROCHLOROFLUOROCARBONS (HCFCs) first major CFC replacement . are used in fire were developed as the OZONE DEPLETING SUBSTANCES (ODS) AND THEIR USES • METHYL BROMIDE (CH3Br) is used as a fumigant and in quarantine treatment.