Ozone layer

Article

October 20, 2021

The ozone layer or ozonosphere is the area of ​​the Earth's stratosphere that contains a relatively high concentration of ozone. While the average concentration of ozone in the atmosphere is 0.3 ppm, in the ozone layer it can reach 15 ppm. This layer, which extends approximately 15 to 40 km in altitude, collects 90% of the ozone present in the atmosphere and absorbs 97% to 99% of high-frequency ultraviolet radiation. The ozone layer was discovered in 1913 by French physicists Charles Fabry and Henri Buisson. Its properties were examined in detail by British meteorologist G.M.B. Dobson, who developed a simple spectrophotometer (the Dobson spectrophotometer) that could be used to measure stratospheric ozone from the Earth's surface. Between 1928 and 1958 Dobson established a worldwide network of ozone monitoring stations that are still in operation today. The Dobson unit, a unit of measurement of the amount of ozone, was named in his honor.

Source of ozone

Ozone is an allotropic form of oxygen that is only stable under certain conditions of pressure and temperature. It is a gas composed of three oxygen atoms ( O 3 {\ displaystyle O_ {3}} ). The photochemical mechanisms that occur in the ozone layer were investigated by the British physicist Sidney Chapman in 1930. The formation of ozone in the Earth's stratosphere is catalyzed by photons of ultraviolet light that, when interacting with the molecules of ozone. gaseous oxygen —consisting of two oxygen atoms ( O 2 {\ displaystyle O_ {2}} ) -, separates them into the constituent oxygen atoms (atomic oxygen). Atomic oxygen combines with those molecules of O 2 {\ displaystyle O_ {2}} which still remain undissociated forming, in this way, ozone molecules, O 3 {\ displaystyle O_ {3}} . The ozone concentration is higher between 15 and 40 km, with a value of 2 to 8 particles per million, in the area known as the ozone layer. If all this ozone were compressed to air pressure at sea level, this layer would be only 3 mm thick. Ozone acts as a filter or shield to protect against harmful and high-energy radiation reaching the Earth, allowing others such as long-wave ultraviolet to pass through. This ultraviolet radiation is what allows life on the planet, as it is what allows the photosynthesis of the plant kingdom, which is located at the base of the trophic pyramid. The remaining 10% ozone that is not in the ozone layer is contained in the troposphere; it is dangerous to living things because of its strong oxidizing character. High concentrations of this compound at the surface level form the fog (photochemical fog).

The dynamic balance of ozone

Ozone is produced by the following reaction: O 2 + h ν - > O + O {\ displaystyle O_ {2} + h \ nu -> O + O} O + O 2 - > O 3 {\ displaystyle O + O_ {2} -> O_ {3}} That is, the molecular oxygen found in the upper layers of the atmosphere is bombarded by solar radiation. Of the broad spectrum of incident radiation a given fraction of photons meets the energy requirements necessary to catalyze the rupture of the chemical double bond of the oxygen atoms of the molecule

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