The ozone depletion phenomenon the ozone depletion. Ozone depletion consists of two related events observed since the late 1970s. What are the reactions involved for ozone layer depletion. Ozone layer depletion is the destruction of ozone gas of upper atmospheric layer stratosphere, caused by substances formed from breakdown of. Chlorofluorocarbons and ozone depletion answer guide. Pdf atmospheric ozone layer depletion and its impact. One of the main reasons for the widespread concern about depletion of the ozone layer is the anticipated increase in. The reaction of these free radicals with ozone disrupts the ozone oxygen cycle, leading to the destruction of stratospheric ozone and the depletion of the ozone layer. When a cfc is broken down, the chlorine generated is a free radical, which has an. Find out what caused the ozone hole, and how the 1989 montreal protocol sought to put an end to ozone depletion. The ozone depletion process replacing lost ozone in the stratosphere the idea is sometimes put forth that humans could compensate for lost global stratospheric ozone by replacing it.
Halogen catalysis of ozone degredation halogens are a chemical family containing fluorine, chlorine, bromine and iodine. Ozone depletion in the stratosphere and increases in greenhouse gases in the troposphere are both subjects of growing concerneven alarmamong scientists, policymakers, and the public. Ozone depletion, gradual thinning of earth s ozone layer in the upper atmosphere caused by the release of chemical compounds containing gaseous chlorine or bromine from industry and other human activities. Adapted for the internet from chlorofluorocarbons and ozone depletion, produced by the american chemical societys national historic chemical landmarks program in 2017.
Sulfuric acid decomposition chemistry above junge layer in. Chemistry of ozone depletion cfc molecules are made up of chlorine, fluorine and carbon atoms and are extremely stable. Ozone is unstable and decomposes to molecular oxygen. The ozone layer refers to a region of earths stratosphere that absorbs most of the suns uv radiation. Free astrochemistry books download ebooks online textbooks. The atomic chlorine and bromine radicals are found in certain stable organic compounds, especially cfcs, which can make their way to the stratosphere because of their low reactivity. Ozone in the stratosphere is necessary to life as we know it because it absorbs energetic uv radiation.
Assessments of ozone depletion as an author, coauthor. Ozone layer depletion definition, causes, solutions toppr. Predictions of significant increases in the incidence of skin cancer resulting from continued use of cfcs spurred international action. Ozone layer depletion is one of the major environmental issues which is getting thinner day by day as a result of increasing pollution. The thinning is most pronounced in the polar regions, especially over antarctica. The latter phenomenon is referred to as the ozone hole. Ozone depletion events odes in the springtime of the arctic have been frequently observed since the early 1980s, and the correlation between the ozone mixing ratio during the odes and the nitrogen oxides nox concentration is still unclear. Cl2g 2clg in presence of light effects of ozone depletion. Some free radicals, such as an oxygen atom, react with another atom or molecule almost immediately.
Causes of ozone layer depletion and its effects on human. The antarctic ozone hole, as it came to be known, made depletion of the ozone layer a real and present danger to lawmakers and the public at large. Atmospheric chemistry, chemical reactions, and history. The ozone layer lies approximately 1540 kilometers 1025 miles above the earths surface, in the stratosphere. The so called hole in ozone layers simply means that above some continents specifically antarctica, asia and parts of south america the mesosphere and stratosphere have lost their original level of ozone content. For their work, rowland and molina shared the 1995 nobel prize in chemistry with another atmospheric chemist, paul j. Besides carbon dioxide, other greenhouse gases are methane, water vapour, nitrous oxide, cfcs and ozone. Others, such as an no 2 molecule, are not quite so reactive and are stable enough to exist for a somewhat longer time. This was also the start of intensive research into the chemistry of the atmosphere.
The depletion of ozone layer is a global phenomena both in terms of cause and effect. Ozone depletion facts and information national geographic. This bad ozone forms when sunlight initiates chemical reac. These processes regulate a balance of ozone and form the ozone layer. The chloroflurocarbons clfc s which is used in air conditioner and a refrigerator is a major cause of ozone depletion. Additional copies may be obtained, free of charge, from. The properties of ozone layer were explored by the british. In the present study, the role of the background level of nox in odes was investigated by using a box model implementing a chemical reaction mechanism. Free chlorine cl atoms then react with ozone molecules, taking one oxygen atom to form chlorine.
Pdf causes of ozone layer depletion and its effects on. Basic ozone layer science ozone layer protection us epa. Cfc molecules are made up of chlorine, fluorine and carbon atoms and are extremely stable. Ozone depletion wikimili, the best wikipedia reader. Ozone depletion also explains much of the observed reduction in stratospheric and upper tropospheric temperatures. Environmental chemistry 401 carbon dioxide crosses the delicate proportion of 0. O 3 depletion leads to the entry of more uv radiation into the troposphere. Sep 30, 2019 chemistry of ozone depletion cfc molecules are made up of chlorine, fluorine and carbon atoms and are extremely stable. Chemistry of the ozone layer there are natural processes that create and destroy ozone in the stratosphere. Cfcs destroy the ozone in the stratosphere 15 20 km above the earths surface ozone concentrations are measure in dobsen units, 1 dobsen unit represents 1 molecule of o 3 for every 1 billion air molecules ozone loss is greatest over antarctica where the ozone depletion has been recorded and is commonly referred to as the ozone hole. Cfcs destroy the ozone in the stratosphere 15 20 km above the earths surface ozone concentrations are measure in dobsen units, 1 dobsen unit represents 1 molecule of o 3 for every 1 billion air molecules ozone loss is greatest over antarctica where the ozone depletion has been recorded and is. When highenergy ultraviolet rays uvc strike an oxygen molecule o.
Free chlorine cl atoms then react with ozone mol ecules, taking one oxygen atom to form chlorine monoxide clo and leaving an oxygen molecule. Far above earths surface, the ozone layer helps to protect life from harmful ultraviolet radiation. When chlorine nitrate, a chemical that ties up chlorine in an ozonesafe form, was added to the hypothesis, the expected amount of ozone loss decreased. It is found that the ozone layer gets affected by some natural causes that are sunspots and stratospheric winds. The earths ozone layer ozone layerthe region of the stratosphere containing the bulk of atmospheric ozone. The ozone layer is mainly found in the lower portion of the stratosphere. Carbon dioxide is the major contributor to global warming. Ozone depletion is the process of destruction of the ozone layer which can cause adverse effects on the living forms by many pollutants releases out from the vehicles, industries etc. Oct 11, 20 know we study about ozone depletion a major problem for all human being.
Atmospheric chemistry division at the national center for. A dynamic equilibrium is maintained between the formation and decomposition of ozone. Sulfuric acid h2so4 is the seed molecule for formation of stratospheric sulfate aerosol layer that assists ozone depletion by activation of halogen species. The antarctic hole now measures about 9 million square miles, nearly the. The handout, activities, and videos will help students understand the timeline and reasons for the initial development and use of chlorofluorocarbons as refrigerants, but also their eventual banning. Ozone depletion and climate change environment canada. All of us are aware of how the concern related to depletion of ozone layer and the ozone hole, which also led to the ban of many chemicals such as the chlorofluorocarbon cfc.
It contains high concentrations of ozone o3 relative to other parts of the atmosphere. Front matter ozone depletion, greenhouse gases, and. National aeronautics and the ozone hole space administratio n. The first manmade threat to the ozone layer was noted by harold johnston 1971. It has been found that this protective ozone layer is getting depleted because of the presence of cfc chlorofluorocarbon compounds. At the same time, recent data show that these atmospheric developments are interconnected and in turn profoundly affect climatic conditions. The chemistry by which cfcs break down ozone is an extremely complicated process. The ozone layer was discovered in 19 by the french physicists charles fabry and henri buisson. Depletion of this layer by ozone depleting substances ods will lead to higher uvb levels, which in turn will cause increased skin cancers and cataracts and potential damage. A seasonal decrease, or hole, in the ozone layer above antarctica, first discovered in 1982 and reported in 1985, was. Atmosphere free fulltext influence of the background. Feb 12, 2018 far above earths surface, the ozone layer helps to protect life from harmful ultraviolet radiation.
When cfc is released into the atmosphere, they mix with atmospheric. Chemistry equations for ozone depletion the student room. Effects of ozone depletion ozone depletion is affecting the human health and environment negatively, as it allows the penetration of uv radiations to reach the earth. Free environmental chemistry books download ebooks online. Mar 21, 2020 ozone depletion, gradual thinning of earth s ozone layer in the upper atmosphere caused by the release of chemical compounds containing gaseous chlorine or bromine from industry and other human activities. Looking back over the scientific investigation of ozone depletion, we can see how the molinarowland hypothesis evolved with new data. Ozone in the troposphere is toxic due to its reactive oxidizing capabilities.
The above reaction leads to the formation of chlorine and begins a chain reaction thereby causing ozone depletion. However, these cause a very nominal contribution to the ozone layer depletion which is near about 1 to 2 percent and therefore these. Environmental chemistry lecture notes by asoka marasinghe. What are the reactions involved for ozone layer depletion in. Uv radiations are very harmful and can cause health issues such as skin cancer, ageing. A seasonal decrease, or hole, in the ozone layer above antarctica, first discovered in 1982 and reported in 1985, was the first confirmation of a thinning of the layer.
There, sunlight could free the chlorine or bromine atoms to form chlorine monoxide or other chemicals, which would deplete upperatmospheric ozone. These advances add to the scientific basis for decisions made by the parties to the montreal protocol. The evaporation of surface water through the stomata of leaves increases, which results in the decreased moisture content of the soil. List of books and articles about ozone layer online. Ozone layer and causes, effects and solutions to ozone. This extreme stability allows cfcs to slowly make their way into the stratosphere most molecules decompose before they can. Chemistry of ozone depletion fire protection association nz. The ozone layer helps to protect life from harmful ultraviolet radiation. There are also springtime polar tropospheric ozone depletion.
Sherwood rowland, mario molina rowlands postdoc at the time, and paul crutzen and in 1995 they received the nobel prize for their work. But ozone depleting substances ods are being released in the atmosphere by highflying jets and rockets. There are also springtime polar tropospheric ozone. The proteins cells in plants undergo harmful mutations, all due to ultraviolet radiations. Free chlorine cl atoms then react with ozone molecules, taking one oxygen atom to form chlo. When chloroflurocarbons go upward and reach at ozone layer the ultraviolet radiation of sun break them and cfcl 3 and chlorine radical is form. It was only until recently, 1990s in fact, that the chemistry of ozone creation and destruction was developed by f. The chemical reactions causing this ozone depletion are primarily based on atomic. The earths stratospheric ozone layer plays a critical role in. The composition of our air, air pollutants, concentration terms, protecting the ozone layer, the chapman cycle, antarctic seasonal ozone depletion, energy from combustion, first law of thermodynamics, heat of combustion, catalytic reforming, fuel alternatives, water for life, neutralizing the. Ozone could be manufactured, stored, transported to the stratosphere, and released in depleted regions. The global exchange between ozone and oxygen is on the order of 300 million tons per day.
The following inquirybased student activities are designed for use in high school lesson planning. Learn what cfcs are, how they have contributed to the ozone hole, and how the 1989 montreal. Know we study about ozone depletion a major problem for all human being. It is based on longer observational records, new chemistry. Actually, two types of compounds like nitric oxide and chlorofluorocarbons are responsible for depleting the. Compare ozone formation in the free troposphere, in photochemical smog and in the stratosphere. Chlorofluorocarbons and ozone depletion american chemical. This timeline highlights the average area of the ozone hole between september 7th and october th as observed by nasa spacedbased instruments see colored bars and scale. Apr 18, 2019 the ozone layer helps to protect life from harmful ultraviolet radiation. Other less common compounds with an odd number of electronsknown as free radicalsreadily undergo chemical reactions and do not.
Scientific assessment of ozone depletion montreal protocol. The chlorofluorocarbon and the halons are potent ozone depletors. Ozone depletion over india with so much worry about the rapid ozone depletion taking place in various parts of the earth, indian scientists are closely monitoring the ozone layer over india for possible depletion trends. Like an infection that grows more and more virulent, the continentsize hole in earths ozone layer keeps ge. These radiations can cause severe diseases in humans such as skin cancer, eye damage and genetic mutations etc 9. Ozone formation, ozone depletion studies in the ozone depletion studies in the ultra violet, monoterpenes, the citrus smell. A presentation about the chemistry of the ozone layer and how cfc affects the thin layer of atmosphere that contains ozone produced by the interaction of ultraviolet light. Depletion of o3 can increase uv radiation entering earth surface. Evidence of ozone depletion in the stratosphere began to appear in the 1980s. This extreme stability allows cfcs to slowly make their way into the stratosphere most molecules decompose before they can cross into the stratosphere from the troposphere. Front matter ozone depletion, greenhouse gases, and climate. Like an infection that grows more and more virulent, the continentsize hole in earths ozone layer keeps getting bigger and bigger each year since the late 1970s, much of the protective layer of stratospheric ozone above antarctica has disappeared during september, creating what is popularly known as the ozone hole. Astrochemistry basic processes pdf 63p this note covers the following topics.
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