Timeline of stratospheric ozone depletion and observations. It prevents the ultraviolet rays of the sun from coming to the surface of the earth. Ozonedepleting substances ods generally contain chlorine, fluorine, bromine, carbon, and hydrogen in varying proportions and are often described by the general term halocarbons. Apr 18, 2019 the ozone layer helps to protect life from harmful ultraviolet radiation. 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. Addressing ozone layer depletion ozone layer protection. B dobson inferred correctly that the cause of the warm stratosphere was heating by the absorption of ultraviolet solar radiation by ozone, and he set out to. Environmental effects of ozone depletion montreal protocol. The ozone hole and global warming union of concerned scientists. The odp is calculated on a per mass basis for each gas relative to cfc 1 1, which has an odp defined to be 1. The first is that they are not reactive chemically speaking, which means they survive long enough in the atmosphere to drift up into the. Its structure means that its much less stable than oxygen o 2, and is therefore much more reactive. The main effect of ozone depletion is an increase in uvb rays reaching the earths surface causes.
The ozone layer can be depleted by free radical catalysts, including nitric oxide no, nitrous oxide n 2 o, hydroxyl oh, atomic chlorine cl, and atomic bromine br. However, chlorine and bromine atoms can survive in the atmosphere for. These substances are effective ozonedepleters for two reasons. They are usually used as a coolant in refrigerators and air conditioners used in cars etc. But through domestic and international action, the ozone layer is healing and should fully recover by about 2065. Learn what cfcs are, how they have contributed to the ozone hole, and how the 1989 montreal. Frequently asked questions about the ozone layer us epa. This website addresses stratospheric ozone issues, including the science of ozone depletion, epas regulatory approach to protecting the ozone layer, epa. The effect of cfcs scientists first began to realize the potential for chlorine to interact destructively with ozone in the early 1970s, and sherwood rowland and mario molina warned of the danger that cfcs posed to the ozone layer in 1974. Chlorofluorocarbons cfc s, carbon tetrachloride, and methyl chloroform are important humanproduced ozonedepleting gases that have been used in many. Cfcs, composed by chlorine, fluorine, and carbon, have a long lifecycle, which favours their accumulation.
Ozone depletion potential odp c global warming potential gwp c halogen source gases chlorine gases cfc 11 45 5291 1 4750 cfc 12 100 4199 0. Causes and effects of ozone layer depletion that are. The ozone layer contains less than 10 parts per million of ozone, while the average ozone concentration in earths. Ozone, a form of oxygen consisting of three atoms of oxygen instead of two, is considered an air pollutant when found at ground levels and is a major component of smog. What emissions from human activities lead to ozone. In fact whole world is vulnerable to its after affects. A usual morning routine might include a spritz of hairspray, a spurt of shaving cream, or a spray of deodorant. The stratospheric ozone layer is a layer of gas 10 to 35 miles above the earths surface. However, both hcfcs and hfcs are green house gases.
Normally, an oxygen molecule contains 2 oxygen atoms. The ozone depletion potential of n 2 o under current atmospheric conditions is computed to be 0. Depletion to ozone layer depletion does not affect a region or a country. Oct 27, 2017 the effects of ozone depletion on plants and animals massive amounts of uvb radiation that penetrate our atmosphere do not only affect humans, but also animals and plants. Ozone molecules are made up of three atoms of oxygen instead of the usual two atoms that make up normal. Case study depletion of ozone in the atmosphere the work of g. Ozone depletion consists of two related events observed since the late 1970s.
The use of cfc s is one of the main reasons for the depletion of the layer. Ozone is a triatomic form of oxygen o 3, found in the earths atmosphere. Ozone o 3 is a gas which is present naturally within earths atmosphere. Ozone layer the ozone layer is basically naturally occurring gas in the region of stratosphere where ozone particles are accumulated 2. Ozone depletion would magnify all of the effects of uv on human health, both positive including production of vitamin d and negative including sunburn, skin cancer, and cataracts. Chlorofluorocarbons or the cfc are the main cause of ozone layer depletion. The ozone layer has historically protected the earth from the harmful uv rays, although in recent decades this protection has diminished due to stratospheric ozone depletion. The ozone layer is a deep blanket in the stratosphere made up of comparatively high concentration of the ozone. In addition, increased surface uv leads to increased tropospheric ozone, which is a health risk to humans.
For example, chlorofluorocarbons cfcs, once used in. It has accounted for less than 8% of total ozone depletion. As a result, there has been a general thinning of the ozone layer over most of the globe, including between five to nine per cent depletion over australia since the 1960s. Collaborators in atmospheric chemistry in the 1970s, chemists sherwood rowland and mario molina discovered that cfcs contribute to ozone depletion. Students will also explore the chemical reactions related to this damage and the. Aerosols are common, convenient, and harmless, right. He and rowland formed a hypothesis about their fate, which suggested that cfcs would deplete the ozone layer. The chlorofluorocarbon and the halons are potent ozone. Causes of ozone layer depletion and its effects on human.
The chlorofluorocarbons cfc refrigerants containing chlorine have been found to be one of the major causes of the destruction of the ozone layer. The production and emission of chlorofluorocarbons cfcs, is the leading cause of ozone layer depletion. The ozone layer depletion is a major concern and is associated with a number of factors. The latest ozone layer depletion news is included at the foot of the page. Cfcs and other ozone depleting substances odss in the stratosphere releases chlorine cl and bromine br atoms that destroy ozone. Ozone layer is also naturally broken down but there is a balance between its formation and natural depletion. The ozone layer lies approximately 1540 kilometers 1025 miles above the earths surface, in the stratosphere.
Refrigerants and cfcs a major cause of ozone layer depletion. We do these things almost automatically, not really even thinking about it. A combination of low temperatures, elevated chlorine, and bromine concentrations in the upper stratosphere are responsible for the destruction of ozone. The introduction of ozone into the stratosphere occurs through cfcs chlorofluorocarbons. It is also one of the prime reasons which are leading to global warming. Cfc s and ozone depletion key concepts ozone in the atmosphere ozone in the lower atmosphere troposphere about 10% of all ozone o 3 in the atmosphere is found in the troposhere up to 16km above the earths surface. The emission of ozone depleting substances has been damaging the ozone layer. Cfcs affect the ozone layer by destroying ozone molecules. Ozone is also used commercially as a bleaching agent and to purify municipal water supplies. The thinning of the ozone layer has increased the risk that australians already face from overexposure to. The atmosphere acts like a multilayer shield that protects earth from dangerous. Ozone layer depletion causes, effects and solutions 7.
Depletion of o3 can increase uv radiation entering earth surface. The ozone depletion resulted in secondary production of an ozone layer near the ground terrestrial ozone layer, which is responsible for adverse effects on plants, humans and environment with. Pollution from ground level all the way up to the highest levels of the atmosphere is neutralized by ozone, which then turns back into pure oxygen. Ozone depletion facts and information national geographic. But in the upper atmosphere, there exists an oxygen molecule which contains 3 oxygen atoms. There are natural processes that create and destroy ozone in the stratosphere. Causes, effects and solutions of ozone layer depletion. What emissions from human activities lead to ozone depletion. Ozone molecules are made up of three atoms of oxygen instead of the usual two atoms that make up normal atmospheric oxygen. Consumption of ozone depleting substances expressed as million tonnes of ozone depletion potential odp, 19892009. In humans, a depleted ozone layer would likely mean high. There are also springtime polar tropospheric ozone depletion. Ozonedepleting substances ods contain various combinations of the chemical elements chlorine, fluorine, bromine, carbon, and hydrogen and are often described by the general term halocarbons.
Ozone in the troposhere has harmful effects on many living things because it is toxic. Chlorofluorocarbons and ozone depletion answer guide. One chlorine molecule from a cfc can destroy up to 100,000 ozone molecules. Ozone layer is located in the earths stratosphere at the distance of 11 km from the surface of the earth. Ozone in the stratospherea layer of the atmosphere between 15 and 50 kilometers 10 and. Ozone layer depletion cause, effects, and solutions. It is formed of three oxygen atoms giving it the chemical formula, o 3.
In 1987, signatories to the montreal protocol on substances that deplete the ozone layer agreed to a 50% reduction in cfc production from 1986 levels by 1998 and a freeze in halon production at. Pdf causes of ozone layer depletion and its effects on. These then react with the ozone molecules, resulting in their removal. The latter phenomenon is referred to as the ozone hole. Predictions of significant increases in the incidence of skin cancer resulting from continued use of cfcs spurred international action. The rest of the molecules are mostly nitrogen and oxygen, like the air we breathe. Ozone depleting substances ods how do ods deplete the ozone layer. The cfcs release free radicals of chlorine, fluorine or bromine.
What are the causes and effects of ozone depletion. The first one has been a slow, but steady ozone depletion of 4% per decade of the earths. There isnt much of it, but ozone is powerful, able to block the most. Ozone holes sources of cfcs, ozone depletion, effects of.
While there are natural sources for all of these species, the concentrations of chlorine and bromine increased markedly in recent decades because of the release of large quantities of manmade organohalogen compounds. Cfcs have a lifetime in the atmosphere of about 20 to 100 years, and consequently one free chlorine atom from a cfc molecule can do a lot of damage, destroying ozone molecules for a long time. The use of carbon tetrachloride in developed countries however, has been prohibited since the beginning of 1996 under the montreal protocol. Executive summary, wmounep scientific assessment of ozone depletion. The ozone layer helps to protect life from harmful ultraviolet radiation. During the 1970s and 1980s, the depletion of the ozone layer was linked to these gases, and countries around the world signed treaties to limit or eliminate their use. It contains high concentration of ozone o 3 in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere. These are referred to as ozone depletion chemicals. The first chlorofluorocarbon was cfc 12, a single carbon with two chlorines and two fluorines attached to it. Far above earths surface, the ozone layer helps to protect life from harmful ultraviolet radiation.
Unfortunately, this gives them plenty of time to find their way to the ozone layer. The layer of ozone gas is what which protects us from the harmful ultraviolet radiations of the sun. In fact, they break up only through sunlight, which divides their molecules, causing the release of. Protecting the ozone layer department of the environment. The ozone layer protects earth from dangerous uv radiation fig. Chemicals called chlorofluorocarbons, or cfcs and other ozone depleting. Questions and answers about the environmental effects of the ozone layer depletion and. It is formed by the reaction of various air pollutants in the presence of sunlight.
These halogenated hydrocarbons, notably trichlorofluoromethane cfc 11, or f11 and dichlorodifluoromethane cfc 12, or f12, have been used extensively as aerosolspray propellants, refrigerants, solvents, and foamblowing agents. 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. 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 to some marine organisms, plants, and plastics. Uncovering the hidden hazard of hairspray a usual morning routine might include a spritz of hair. The ozone layer or ozone shield is a region of earths stratosphere that absorbs most of the suns ultraviolet radiation. Halogenated hydrocarbons, especially chlorofluorocarbons cfcs, are a major cause of ozone layer depletion because of the amounts of chlorine atoms that are part of their makeup. The destruction of ozone is accelerated by certain trace gases containing nitrogen, hydrogen, bromine, and chlorine. The ozone layer is about 300 to 500 du thick on average, which is about the thickness of two stacked pennies. Chlorofluorocarbons and other gases that have the potential to damage the ozone layer are highly regulated. Uvb radiation damages aquatic organisms, especially small creatures such as plankton, aquatic plants and crabs. The most important is the chlorofluorocarbons, in the atmosphere. These free radicals destroy the stratospheric ozone as a result of which the ozone layer is thinned. Causes of ozone depletion there are two different types of ozone depletion, both are very similar. The richness of the ozone layer that makes the hole so significant and the science behind the hole is far less popular.
Ozone forms a protective layer in the stratosphere and shields earth from the damaging rays of the sun, namely the suns ultraviolet rays. The ozone layer is a belt of the naturallyoccuring gas ozone that sits at an altitude of between 15 and 30 kilometers above the earth. Recently it has also been used in the production of cfc 11 and cfc 12. Ozone layer depletion is one of the most serious problems faced by our planet earth. Where there is no ozone, there is generally pollution.
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. Although emissions of cfcs around the developed world have largely ceased due to international control agreements, the damage to the stratospheric ozone. The ozone depletion potential represents the amount of stratospheric ozone destroyed by the release of a unit mass of a chemical at earth. Find out what caused the ozone hole, and how the 1989 montreal protocol sought to put an end to ozone depletion. The word ozone means smelly in greek because the gas has a strong odor. The ozone layer, in the stratosphere, is where about 90% of the ozone in the earth system is found. Researchers indicate that many of the effects of ozone depletion on human health tend to apply for animals, too. A gas with a larger odp has a greater potential to destroy ozone over its lifetime in the atmosphere. Ozone depletion is primarily caused by human activities. The patches of the thinned ozone layer are known as ozone holes. The increase in the levels of uv rays lead to high rate of skin cancer and eye related problems. The main causes responsible for the depletion of the ozone layer are listed below. Almost always the ozone has only been correlated with the hole in the ozone layer and the damages it has caused to the environment. Cfc molecules are highly stable and can last for up to 100 years.
As a result of its chemical composition, ozone is regarded as a special type of oxygen as it contains three oxygen molecules o3 as opposed to the usual two oxygen molecules o2. The reason behind ozone layer depletion is mainly due to the extensive use of ozonedepleting substances ods. Chlorine interacts with ozone, converting it into oxygen and taking away its beneficial properties. Ozone depletion potential an overview sciencedirect topics. The thinning is most pronounced in the polar regions, especially over antarctica. Ozone depletion occurs when chlorofluorocarbons cfcs and. But ozone makes up only one to ten out of every million molecules in the ozone layer. Feb 12, 2018 far above earths surface, the ozone layer helps to protect life from harmful ultraviolet radiation. These chemicals are found in cleaning agents, aerosols, insulating foam, and refrigerants. Ozone is a colourless gas which is found in the stratosphere of our upper atmosphere. 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. Ozone depletion is largely a result of manmade substances. About the ozone layer 2 international conventions for the 3 protection of the ozone layer chinas commitment about the ozone layer the ozone layer acts as a fi lter to protect the earth from harmful ultraviolet radiation, but it is gradually depleted through the process of industrialization. Chlorofluorocarbons and ozone depletion american chemical.
B dobson and other scientists in measuring concentrations of chloride and ozone in the atmosphere g. Ozone protection and accelerated phaseout of hcfcs in china. Cfcs, or chlorofluorocarbons, are normally stable molecules, but when uv rays strike them, they are broken down. 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. Most of the gases responsible for these ozone holes are released as a result of human industrial or agricultural activity. The ozone hole stratospheric ozone protection and cfcs nh des.
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