Depletion of the Ozone Layer – its Mechanism and Effects

Introduction:

The ozone layer, or ozone shield, is the region of Earth’s stratosphere that absorbs most of the sun’s ultraviolet radiation. It is still low compared to other gases in the stratosphere, but contains higher concentrations of ozone O3 than other parts of the atmosphere. The ozone layer contains less than 10 ppm of ozone, but the average total ozone concentration in the Earth’s atmosphere  is about 0.3 ppm. The ozone layer is primarily in the lower  stratosphere, about 15-35 kilometres  above Earth, but its thickness varies seasonally and geographically. 

Discovery of the ozone layer:

The discovery of the ozone layer in 1913 was done first by the French physicists Charles Fabry and Henri Buisson. Sun measurements show that radiation emitted from the surface of the Sun and reaching the Earth’s ground  is  consistent with a blackbody spectrum at temperatures typically in the range 5,500 to 6,000 K (5,230 to 5,730 ° C). Radiation below a wavelength of about 310 nm at the UV edge of the spectrum. It was concluded that the lost radiation was  absorbed by something in the atmosphere. 

Creation of ozone layer:

The photochemical mechanisms that deliver upward thrust to the ozone layer have been located with the aid of using the British physicist Sydney Chapman in 1930. Ozone withinside the Earth’s stratosphere is created with the aid of using ultraviolet light striking normal oxygen molecules containing  oxygen atoms (O₂), splitting them into individual oxygen atoms (atomic oxygen); the atomic oxygen afterwards come together with unbroken O₂ to form ozone, O₃. The ozone molecule is unstable (although, withinside the stratosphere, long-lived) and while ultraviolet light hits ozone it splits right into a molecule of O₂ and an individual atom of oxygen, a persevering with procedure known as the ozone-oxygen cycle.

Distribution of ozone layer in the stratosphere:

The thickness of the ozone layer varies globally and is commonly thinner close to the equator and thicker close to the poles. Thickness refers to how a great deal ozone is in a column over a given region and varies from season to season. The motives for those versions are because of atmospheric circulation patterns and sun intensity. The highest ozone levels are in the Arctic Circle in the spring  of March and April, while Antarctica has the  lowest  ozone levels in the summer months of September and October. 

Ozone layer depletion:

Ozone depletion includes  associated occasions determined for the reason that past due 1970s: a regular reduction of approximately 4% withinside the general quantity of ozone in Earth’s atmosphere, and a far larger springtime lower in stratospheric ozone (the ozone layer) round Earth’s polar regions. The second process is known as the ozone hole. There also are springtime polar tropospheric ozone depletion occasions further to those stratospheric occasions. 

Causes of depletion:

The main cause of ozone depletion and  ozone hole formation is called ozone depleting substances (ODS) due to industrial chemicals, especially manufactured halocarbon refrigerants, solvents, propellants and blowing agents (chlorofluorocarbons (CFCs), HCFCs, halons). These compounds are ejected from the surface and transported into the stratosphere by turbulent mixing, where the molecules mix much faster than they can settle. Upon reaching the stratosphere, they release atoms of halogen groups through photodissociation, which catalyses the breakdown of ozone (O₃) into oxygen (O₂). 

Effects of depletion:

Ozone depletion and the ozone hole have generated global problems that have expanded most cancers, dangers and different poor effects. The ozone layer prevents dangerous wavelengths of ultraviolet (UVB) light from passing the Earth’s atmosphere. These wavelengths motivate pores and skin cancers, sunburn, everlasting blindness, and cataracts, which have been projected to boom dramatically because of thinning ozone, in addition to harming flowers and animals. 

Ozone layer recovery:

The 1987 Montreal Protocol on Substances That Deplete the Ozone Layer commenced the phaseout of CFCs in 1993 and sought to reap a 50 percentage discount in international intake from 1986 stages with the aid of using 1998. A collection of amendments to the Montreal Protocol withinside the following years changed into designed to reinforce the controls on CFCs and different halocarbons. By 2005 the intake of ozone-depleting chemical compounds managed with the aid of using the settlement had fallen with the aid of using 90–ninety five percent withinside the nations that have been events to the protocol. 

Conclusion:

Global intake of ozone-depleting materials has been decreased by means of a few 98% considering international locations started out taking motion beneath the Montreal Protocol. As a result, the atmospheric attention of the maximum competitive styles of ozone-depleting materials is falling and the ozone layer is displaying the primary symptoms of recovery.

Nevertheless, the ozone layer isn’t predicted to get better absolutely earlier than the second half of this century. 

Much remains to be done to ensure the ongoing healing of the ozone layer and to lessen the effect of ozone-depleting materials on the Earth’s climate.