ozone depletion

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  • OZONE DEPLETION Adriana Orjuela, Ansar Mustafa, Yohana Shum (Francis Lewis High School), Adam de Delva, Nandini Seepersaud (Math, Science Research, And Technology High school )This project has the objective of informing the audience about why the ozone layer is so important to preserve life on Earth and why we must remain committed to protecting it.Ozone layer arose naturally as a by-product of the evolution of photosynthesis and the rise of atmospheric oxygen. It is very fragile which can be destroyed by various catalytic cycles involving elements such as nitrogen, chlorine and bromine. Today it is being threatened by chemicals released into the atmosphere by anthropogenic activities. It is a serious problem and significant steps have been taken to reduce the impact.Effects on life UVA/UVB & UVC rays- Mechanisms for halting ozone depletion: Ratification by the international community of treaties designed to reduce Freon and halon emissions Development of ozone friendly substitutes for Freons by the chemical industry.The tropospheric ozone layer is a vital part of the earths atmosphere that helps life flourish on earth. Its effect is relatively straightforward: absorbing harmful UVB and UVC rays before they make it to the earths surface. Numerous atmospheric researchers have concluded that anthropogenic ozone depleting sources are at fault for recent ozone depth decreases. This poster covers exactly what has been happening to the ozone layer within recent decades and how it specifically affects life on earth. The ozone layer consists of O3 molecules that are created by UV photons in a special part of the troposphere. Scenarios in which the ozone layer is nonexistent will be discussed as well as what we can do to stop ozone depletion from occurring.Humans can quickly make crucial adaptations to increased UV-B radiation by staying out of the sun, protecting their skin with clothing, and applying sunscreens. However, plants and other animals that help support us and other forms of life cant make such changes except through the long process of biological evolution. The Montreal Protocol and many others wanted to lower the abundance of stratospheric chlorine; it shows the concentrations under the various international agreements and the absence of them (No protocol). With no protocol, stratospheric chlorine would have been expected to have risen quite rapidly over the new few decades.With the Beijing 1999 Accord the outlook is much more improved. Scientists and experts expect that the hole will disappear by 2060, when the stratospheric chlorine should be back down to about 2 ppb. They hope that within the following century, stratospheric chlorine should reach the background level of 0.6 ppb Montreal Protocol in 1987: placed strict limits on amount of Freons and halons that could be realeased into the atmosphere by any country.Sources & Sinks of Ozone depleting compoundsAtmospheric chemists have been searching for reasons as to why the amounts of Ozone in the atmosphere have been depleting and now feel that they have found the main culprits to this phenomenon. The gasses that damage the ozone layer by using O3) as a catalyst which reduces the availability of Ozone. Two Catalytic cycles known as the Nitrogen and Chlorine catalytic cycles react with ozone to break it back down into O2. The Nitrogen Catalytic cycle quickly reacts with O3) to create Nitric oxide and Oxygen as well as nitrogen dioxide. The Chlorine catalytic cycle is one that humans directly contribute to with industrial activity. This cycle is much faster than the nitrogen cycle because it shoots the Chlorine directly into the troposphere and is shifted upward to the stratosphere by winds and eddies. The usage of Freons rapidly damaged the Ozone layer because of its reactivity with O3 molecules. Bromine has a very similar effect to O3 molecules because of the way that they break down O3 into O2 Professor: Kimmy Szeto (Queens College) Classification of UV Radiation

    Range (nm)NameBiological Effects320-400UVARelatively harmless; causes tanning but not burning290-320UVBHarmful; causes sunburn, skin cancer and other disorders200-290UVCExtremely harmful but almost completely absorbed by the ozone

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    Course Textbook: Third Edition THE EARTH SYSTEM