Ozone Layer It is the part of Earth’s atmosphere that contains ozone gas extensively.^[1][2][3] It is highly localized in the lower stratosphere of Earth’s atmosphere and is blue in colour.

Part of the oxygen gas turns into ozone gas due to the strong ultraviolet radiation emitted by the sun and affects this part of the atmosphere due to the absence of thick layers of air above it to protect it. This layer is of vital importance to us, as it prevents short ultraviolet waves from reaching the Earth’s surface in high concentration.

The ozone layer was discovered by Charles Fabry and Henri Poisson in 1913, and details were learned about it through Gordon Dobson, who developed an instrument to measure ozone present in the stratosphere from the Earth’s surface.

Between 1928 and 1958, Dobson created a global network for monitoring ozone, which is still in operation today. The Dobson unit, a unit of measurement for total column ozone, is named in his honour.

Especially if we know that ozone gas, which consists of three oxygen atoms, has a greenish color, and that one of the most important functions of the ozone layer is to protect the earth’s surface from the harmful rays of the sun from reaching its surface, especially ultraviolet rays, which cause severe damage to humans, especially skin cancers .. and also to animals. and plant both.

UV rays and ozone[عدل]

The role of the ozone layer:
Although the concentration of ozone in the ozone layer is low, it is vitally important to life on Earth, as it blocks harmful ultraviolet (UV) radiation from the sun. It is classified according to its wavelengths into UV-A, UV-B and UV-C, the latter being considered very dangerous to humans and is completely purified by ozone at an altitude of 35 km. However, ozone gas is toxic at low altitudes, as it causes bleeding and others.

Exposure to UV-B rays can burn the skin (severe redness); And severe exposure to it may lead to a change in the genetic code that results in skin cancer. Although the ozone layer prevents the arrival of UV-B rays, some of them reach the Earth’s surface. Most of the UV-A rays reach the earth and are not very harmful, but they can cause a change in the genetic code as well.

The depletion of the ozone layer allows ultraviolet radiation, in particular the more harmful wavelengths, to reach the surface of the Earth, which leads to an increase in the possibility of changes in the genetic genes of living things on Earth.

DNA sensitivity to ultraviolet light[عدل]

To appreciate the importance of protection from ultraviolet radiation, we can avoid damage from exposure to radiation in an action spectrum, which shows us the effect of biological radiation according to wavelength. The effect could be a skin burn, a change in plant growth or a change in DNA. Change damage from radiation exposure depending on the length of the waves. Fortunately, the structure of DNA changes at wavelengths below 290 nanometers, which are largely blocked by the ozone layer. At longer wavelengths, which are slightly blocked by ozone, DNA is not severely damaged. If the ozone decreases by 10%, there will be a change of 22% in the DNA from the effect of ultraviolet radiation. For science, changes in DNA lead to diseases such as skin cancer, and this shows the importance of the ozone layer on our lives.

Where is ozone distributed?[عدل]

The thickness of ozone is the total amount in a vertical column of air, and it varies for many reasons, as it is less at the equator and greater with passage at the poles. They also differ in seasons, being thicker in the spring and thinner in the fall. The reasons for this are complex, including the atmospheric cycle and the power of the sun.

Since ozone in the stratosphere is produced due to ultraviolet radiation from the sun, it is expected that the highest levels of ozone will be at the equator and the lowest at the poles. For the same reason, it is possible to conclude that the highest levels of ozone are in summer and lowest in winter. However, this is not true, as the highest levels of ozone are found in the north and south poles, as they are higher in the spring, not in the summer, and the lowest in the fall, not in the winter. During the winter, the ozone layer gets thicker. This puzzle is explained by the wind cycle in the stratosphere known as the Brewer-Dobson cycle. Most of the ozone is produced over the poles, and the wind cycle in the stratosphere moves from the poles towards and back to a lower altitude in the stratosphere.

The ozone layer is higher at the equator and lower at distance from the equator, especially at the poles. The altitude variation in ozone is caused by the slow air circulation that lifts ozone from the troposphere to the stratosphere.

The farther we move from the equator, the thicker the ozone towards the poles. In general, the amount of ozone is more in the North Pole than in the South Pole. In addition, the thickness of ozone in the Arctic is greater in the spring (March-April) than in the Antarctic, while in the Antarctic it is greater in the autumn (September-October) than in the Arctic during the same period. In fact, the largest amounts of ozone worldwide are found in the Arctic during the spring period, and during the same period, the lowest amounts of ozone worldwide are found in the Antarctic during the Antarctic spring period in September and October, due to the phenomenon of the ozone hole.

Ozone depletion[عدل]

The ozone layer can deplete hydroxyl (OH), chlorine (Cl) and bromine (Br). Where there are natural sources for all the elements mentioned, however, the concentration of chlorine gas and bromine gas has increased significantly in recent years due to human production of some compound substances, especially chlorofluorocarbons (CFCs) and also bromofluorocarbons.

These chemically stable compounds can reach the stratosphere where ultraviolet rays break down both chlorine and fluorine. Each of them starts to catalyze a chain reaction capable of breaking down more than 100,000 ozone molecules. Ozone in the northern hemisphere is declining by 4% per decade. Roughly more than 5% of the Earth’s surface around the North Pole and Antarctica, more (but seasonally) may decrease; This is called Ozone whole.

Proposed solutions to reduce ozone depletion[عدل]

Sweden became the first country to ban the use of insecticide sprays (such as insecticides) that contain ozone-destroying chlorofluorocarbons (CFCs) on January 23, 1978. Other countries such as the United States of America, Canada, and Norway followed suit. And the European Community has blocked a similar proposal. Even in the United States, CFCs were still used in other places such as refrigerators and industrial cleaners even after the discovery of the Antarctic ozone layer hole in 1985. After talks and an international treaty (the Montreal Protocol), CFC production was largely halted starting in 1987. And completely in 1996.

On August 2, 2003, scientists announced that the depletion of the ozone layer had begun to slow after the ban on the use of chlorofluorocarbons (CFCs).

Three satellites and three ground stations have shown that the depletion of the upper ozone layer has slowed dramatically over the past decade. The study was conducted by the American Geophysical Union. Some decomposition still exists in the ozone layer due to the failure of some countries to prevent the use of chlorofluorocarbon (CFC) in addition to its presence in the stratosphere before its use was banned, as it has a long decomposition period from 50 to more than 100 years, and therefore the ozone layer needs its full return for several decades.

Currently, components containing (CH) are installed to replace the use of chlorofluorocarbons (CFCs) such as hydrochlorofluorocarbons (HCFCs), as these compounds are more active and fortunately do not remain long enough in the atmosphere to reach the stratosphere where they affect the ozone layer.

See also[عدل]

• Ozone gas
• Dobson spectrometer for measuring ozone

Reference[عدل]

external links[عدل]

• Stratospheric Ozone: E-Book (English)
• NASA Study of Earth from Space, June 2000 (English)
• [علوم: أساسيات الأوزون http://www.ozonelayer.noaa.gov/science/basics.htm]. (Einglish). Retrieved January 29, 2007
• Report on the ozone hole

• Ecology portal
• Space portal
• Chemistry portal
• Earth Sciences Portal

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