Essay On Ozone Depletion Ozone depletion directly affects society and the environment through increased exposure to UV radiation on humans, animals, plants and materials. Increased exposure to UV radiation can have serious adverse side effects for humans: Skin Cancer UV-B radiation can cause benign and malignant skin melanomas Ozone Depletion Essay Words | 6 Pages. Why is the ozone layer of much concern to scientists and environmentalists? The ozone layer is quite beneficial to human life and existence. The destruction of this layer has been linked to the now common health conditions such as cancers, skin conditions and cataracts among others · Ozone depletion has been described as a potential catastrophe and a planetary time – bomb. The four main areas affected by a depleted ozone layer and thus by the corresponding increase in harmful ultraviolet radiation are agriculture, wildlife, the environment, and human health
AP Environmental Science: Ozone Depletion - Words | Bartleby
The ozone layer protects the Earth from the ultraviolet rays sent down by the sun. If the ozone layer is depleted by human action, the effects on the planet could be catastrophic.
Ozone is present in the stratosphere. The stratosphere reaches 30 miles above the Earth, and at the very top it contains ozone. The suns rays are absorbed by the ozone in the stratosphere and thus do not reach the Earth.
Ozone is a bluish gas that is formed by three atoms of oxygen. The form of oxygen that humans breathe in consists of two oxygen atoms, O 2.
When found on the surface of the planet, ozone is considered a dangerous pollutant and is one substance responsible for producing the greenhouse effect. In recent years, ozone depletion essay, the ozone layer has been the subject of much discussion. And rightly so, because the ozone ozone depletion essay protects both plant and animal life on the planet.
The fact that the ozone layer was being depleted was discovered in the mids. The main cause of this is the release of CFCs, chlorofluorocarbons. Antarctica was an early victim of ozone destruction, ozone depletion essay. In the future, the ozone problem will have to be solved so that the protective layer can be conserved.
Only a few factors combine to create the problem of ozone layer depletion. The production and emission of CFCs, chlorofluorocarbons, is by far the leading cause. Many countries have called for the end of CFC production because only a few produce the chemical. However, those industries that do use CFCs do not want to discontinue usage of this highly valuable industrial chemical. CFCs are used in industry in a variety of ways and have been amazingly useful in many products, ozone depletion essay.
Discovered in the s by American chemist Thomas Midgley, CFCs came to be used in refrigerators, ozone depletion essay, home insulation, plastic ozone depletion essay, and throwaway food containers, ozone depletion essay.
Only later did people realize the disaster CFCs caused in the stratosphere. There, the chlorine atom is removed from the CFC and attracts one of the three oxygen atoms in the ozone molecule. The process ozone depletion essay, and a single chlorine atom can destroy overmolecules of ozone. InSherwood Rowland and Mario Molina followed the path of CFCs. Only inwhen the ozone layer hole was discovered over Antarctica, was the proof truly conclusive. At that point, ozone depletion essay, it was hard to question the destructive capabilities of CFCs.
Even if CFCs were banned, problems would remain. There would still be no way to remove the CFCs that are now present in the environment. Clearly though, something must be done to limit this international problem in the future. Atmospheric oxygen absorbs ultraviolet radiation shorter than nm and photo-dissociates into two oxygen atoms.
These unite with ozone depletion essay O 2 molecules to form ozone, ozone depletion essay. During the process surplus energy of nascent O 3 is often transferred to the nearby molecules as kinetic energy which slightly raises the surrounding atmospheric temperature.
Ozone too is effective in absorbing particular short wavelength UV radiation in the range nm, releasing atomic oxygen. This natural mechanism, however, ozone depletion essay, does not necessarily upset the ozone equilibrium because the loss of ozone caused by natural process is compensated by the creation of ozone through atmospheric circulation.
Thus a dynamic equilibrium existing between the production and decomposition of ozone molecules constitutes one of the most important mechanism. The heat generated during the reaction causes a rise in temperature of the stratosphere. Secondly, the photochemical process absorbs most of the harmful solar ultraviolet radiations of wavelength from Å to Å.
Without it, life on the earth would be completely destroyed. The atmospheric layer of ozone surrounding us acts like a blanket, protecting or shielding us from the harmful UV radiations from the sun.
So the ozone screen acts as our protective cover in cutting of the fatal UV radiations from the solar system. Ozone acts as a powerful oxidant because of its ability to remove electrons from other molecules. It occurs as a natural component of air. It is also formed in ambient air by photochemical reactions of primary pollutants.
Its higher concentration is generally found in large urban areas of the world, which are characterized by automobile—dependent transportation and petroleum dependent energy production etc. Surface ozone is produced as a result of chemical reactions in the atmosphere driven by the action of UV radiation in the sunlight, involving both nitrogen oxides NO x and volatile organic matter VOM.
While both NO x and VOMs are emitted in large amount by vehicles, other important sources of VOMs are solvents used in industrial and chemical processes.
According to British scientists, ozone depletion essay, this surface ozone is responsible for the substantial reduction in the yields of major crops like wheat and rice. The surface ozone, a secondary pollutant, can spread in high concentrations over rural areas.
There are the other sources of ozone in the environment, such as gamma radiation used in food preservation plants, commercial UV lamps used for sterilization, high voltage electric equipments, dermatological phototherapy equipments and even in photocopying machines. Ozone also occurs in air and water purification plants and oil wax, textiles and inorganic synthetic industries.
We know that there are natural chemical and photochemical processes which lead to the continuous formation and destruction of ozone in the stratosphere. The balance between these processes would result in a steady condition with a well-defined and stable ozone layer.
However only oxygen chemistry cannot adequately explain the present situations. Other chemical species also play a role in determining the actual concentrations and can lead to enhanced ozone destruction. Some of these species occur naturally, while others are of recent industrial origin, ozone depletion essay. The amount of some of the natural ozone depletion essay moving into the stratosphere has been augmented in recent years by a number of human activities.
Many of the processes, which are responsible for the depletion of ozone layer, ozone depletion essay, share a general mechanism of the type. Here Ozone depletion essay is the reacting species, ozone depletion essay. Each of ozone depletion essay species is capable of destroying the ozone layer in varying degrees, depending on altitude and the mixing ratio. Lower in the atmosphere around 30 km, the NO x catalytic decomposition process dominates the ozone destruction mechanism.
The HO x radicals are generated by either of the following two photochemical reactions:. The nitric oxide cycle contributes in a significant way in the natural destruction of stratospheric ozone in the lower region of the stratosphere:.
In the upper atmosphere, ozone depletion essay, NO is produced by reactions involving atomic and ionic species of nitrogen and oxygen. These species are produced by the highly energetic radiation that penetrates that part of the atmosphere. Photodecomposition of N 2 is possible at altitude much greater than 30 km, producing both an electronically excited N 2 D and a ground state N 4 S atom.
The ground state nitrogen subsequently reacts with O 2producing another natural source of NO:. At altitudes of less than 30 km, ozone depletion essay, additional NO is also generated via a reaction:. Where O 1 D is excited state oxygen. The principal source of nitrous oxide is the process of denitrification in soils having high concentration of nitrate ion:.
The increase in atmospheric nitrous oxide N 2 O mixing rations is due to some extent to enhanced rates of denitrification resulting from greater use of nitrogenous fertilizers worldwide. Although the mixing ratio of nitrous oxide in the troposphere is steadily increasing, the production of stratospheric nitric oxide through various processes can, ozone depletion essay, in a large part, be attributed to natural causes.
Nitrogenous fertilizers are also responsible for much of the increase, ozone depletion essay. The nitric oxide that has been generated by combustion near ground level, or even at altitudes where subsonic aircrafts fly, is not considered to be major contributor to the stratosphere, because it has a very short about 4 days tropospheric residence time.
The CFCs and halons are entirely manmade with wide applications in air conditioning, refrigeration, aerosols, electric and metal clearing, ozone depletion essay, foam blowing and modern firefighting, ozone depletion essay.
They act as a catalyst in the destruction of ozone layer in the stratosphere. The rate of destruction of ozone is further enhanced by the oxides of nitrogen NO x released from the exhausts of large fleet of supersonic aircrafts SST. A wide range of chlorofluorocarbons CFCs are known, but widely used are CFCl 3 and CF 2 Cl 2which are in use since CFCs and halons remain inactive in the troposphere and it takes about years for these chemicals to travel and reach the stratosphere, but after that their intermediate product chlorine radical retrains active for more than years.
The travelling time for CFCs and halons to reach to stratosphere may range from 20 to 40 years, that is, CFCs generated in the troposphere today may take 20 to 40 years to reach the stratosphere. Once these CFCs and halons reach to stratosphere, the ozone depletion essay and bromine atoms present in these chemicals are released as a result of interaction with UV radiations in the stratosphere.
In spite of the fact that CFC molecules are much heavier than those of air, they ozone depletion essay to be well mixed and homogeneously distributed throughout the troposphere in the gas phase because of strong convective mixing, ozone depletion essay.
Because they do not react, ozone depletion essay, they circulate through the troposphere until they leak or escape into the stratosphere. At higher altitudes they are capable of undergoing UV photolytic decomposition, as a result of being exposed to the intense flux of energetic UV radiation—. The released chlorine ozone depletion essay is capable of taking part in the catalytic decomposition of ozone as follows:.
Chlorine atoms catalyse the destruction of ozone. A significant natural precursor ozone depletion essay atomic chlorine is CH 3 Cl, which is produced biogenically from the oceans, ozone depletion essay the burning of vegetation and from volcanic emissions. Once in the atmosphere, CH 3 Cl undergoes photochemical reaction.
Other natural sources of chlorine are various forms of chlorine. Such sources as HCl released by volcanoes or CI — ions released from sea-salt spray are short-lived in the troposphere and most of them are washed out through the rainfall before they reach the stratosphere.
There are other catalytic cycles also involving chlorine. For example. It should be noted that natural sources produce small amounts of atomic chlorine in the stratosphere, but there is a ozone depletion essay destruction of ozone by chlorine derived from the anthropogenically produced CFCs. Taking into consideration the ozone depleting CFCs and halons, ozone depletion essay, scientists are trying to modify the relative amounts of fluorine, chlorine and hydrogen in new compounds.
Thus a common approach is to incorporate hydrogen in the structure, as in hydrochlorofluorocarbons HCFCs or replace chlorine and produce hydrofluorocarbons HFCs. Ozone depletion essay the content of hydrogen reduces the inertness of the compound and in this way the lifetime of the compound in troposphere may be made short.
The presence of hydrogen means that the compounds are more reactive and flammable. But the higher reactivity is ozone depletion essay disadvantage in many applications. If the proportion of fluorine is increased at the expense of chlorine, then a highly stable compound will be formed because the bond energy of C-F bond is larger than C-Cl bond. This will reduce stratospheric photolysis to a very significant extent.
The Ozone Layer Essay in English
, time: 8:17Essay on Ozone Layer Depletion in English @
Essay On Ozone Depletion Ozone depletion directly affects society and the environment through increased exposure to UV radiation on humans, animals, plants and materials. Increased exposure to UV radiation can have serious adverse side effects for humans: Skin Cancer UV-B radiation can cause benign and malignant skin melanomas Ozone Depletion Essay Words | 6 Pages. Why is the ozone layer of much concern to scientists and environmentalists? The ozone layer is quite beneficial to human life and existence. The destruction of this layer has been linked to the now common health conditions such as cancers, skin conditions and cataracts among others · Ozone depletion has been described as a potential catastrophe and a planetary time – bomb. The four main areas affected by a depleted ozone layer and thus by the corresponding increase in harmful ultraviolet radiation are agriculture, wildlife, the environment, and human health
No comments:
Post a Comment