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Ozone layer is a thin layer of gas above the earth’s surface which acts as a shield from the harmful ultraviolet B radiation emitted by the sun. It is formed 15 to 30 kilometers above the earth. Ozone is known to be a particular gas present both in the Earth’s upper atmosphere and at ground level. There are two discrete types of ozone; the Stratospheric Ozone (or “good” ozone) and the Ground-level Ozone (or “bad” ozone layer). Ozone is highly reactive molecule consisting of three oxygen atoms bound together. Due to its high reaction with the molecules it displays a destructive side when it comes into direct contact with the life forms. Today, one of the most discussed and serious environmental issues are ozone depletion.
Causes of Ozone depletion
The reduction in the amount of ozone present in stratosphere is known to be ozone depletion. From 1979 to 1990 there was approximately a reduction of 5%. This reduction of ozone is caused by increase in the level of free radicals such as hydroxyl radicals, nitric oxide radicals and atomic chlorine and bromine. Almost 80% of the total depletion of ozone in the stratosphere is caused due to chlorofluorocarbons (CFC). CFC’s cannot destroy with the reaction of other chemicals and it is not washed away by the rain. They can stick in the atmosphere for 20 to 120 years or more.
One important cause or reason for the ozone depletion is global warming and climate change. Scientists believe that Global Warming will lead to a weaker Ozone layer. Global warming may increase the atmospheric heat distribution. This leads to increase the cooling of the stratosphere. This cooling increases ozone depletion in polar areas. Cooling of stratosphere means stratosphere will be observing less UV rays from the sun causing the troposphere to warm. If this continues, the recovery of ozone would not take place though the chlorine and bromine starts to decrease. In 1980’s researchers first discovered the “ozone hole”. This was found above the Antarctica. The “ozone hole” refers to a large area of stratosphere with relatively low amount of ozone. The Antarctic hole now measures around 9 million square miles. It is almost the size of North America.
Effects of ozone depletion on health
Ozone layer prevents the earth from sun’s harmful ultraviolet rays. When the ozone depletes, amount of UVB rays reaching the earth will increase. Ultraviolet rays of the Sun are familiar with a number of health related issues on humans and as well as on animals. The most important of these are the increased risk of developing several types of skin cancers including malignant melanoma, basal and squamous cell carcinoma. The incidences of cataract and skin cancers continue to rise in many countries, with significant societal impacts and costs to health care systems. These UV rays cause adverse effect on eyes. It causes infectious diseases and it damages the respiratory system as well.
Effects of ozone depletion on environment
Ozone depletion affects climate, and climate affects ozone. Increases in the concentration of green house gases will affect the amount of ozone present in the stratosphere. It leads to decrease the temperature in the stratosphere and it accelerates circulation patterns. As a result total amount of ozone present in tropics will decrease and at mid and high latitude total amount of ozone increases. Therefore this will affect the planet's climate. Wind patterns and rainfall could change, resulting in climatic changes throughout the world.
An important component of the marine food chain known as phytoplankton can also be affected by ozone depletion. The ultraviolet rays can affect the survival of these microscopic organisms by affecting their orientation and mobility. If this happened, it will affect the other animals that are above plankton in the food chain. As a result oceans will be hit hard. Researchers also have attested changes in the reproductive rates of young fish, shrimp, and crabs as well as frogs and salamanders overt to excess ultraviolet B.
Conclusion
Ozone layer depletes due to natural reasons even and it varies geographically and by season. Each natural reduction in ozone level has got its own recovery too. However, recently the scientific evidence shows that the ozone shield is being depleted beyond changes due to natural causes. Increasing concern for the causes and effects of ozone depletion led to adopt the Montreal Protocol, in the year 1987. This was adopted in order to decrease and control the industrial emission of CFC. This international agreement showed a positive effect. It has succeeded to a great extent. In order to mitigate the problem, more cooperation and understanding among all the countries of the world is required.
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