Destruction of the ozone layer causes, process, consequences

2043
Abraham McLaughlin
Destruction of the ozone layer causes, process, consequences

The ozone layer destruction It is caused by the decrease in the levels of the ozone molecule (O3) in the terrestrial stratosphere, due to the release of polluting gases such as CFCs, solvents, halocarbon refrigerants, propellants, among others.

This hole in the ozone layer is a danger to life on Earth, since this gaseous layer is the protective shield against ultraviolet radiation. The ozone layer (ozonosphere) is a strip of ozone gas (O3) that is formed in the lower stratosphere, approximately 25 km high.

The hole in the ozone layer in 2006, with approximately 27.5 million square km. The blue and purple areas are where there is less ozone, and the green, yellow and red areas where there is more ozone.

Ozone is formed when the oxygen molecule (Otwo) by the action of ultraviolet radiation, generating two oxygen atoms. Subsequently, an oxygen atom (O) is fused with an oxygen molecule (Otwo), producing O3 (ozone).

In 1985 a hole in the ozone layer was discovered at the South Pole, which originated during the austral spring (July-September). Scientists found that ozone destruction is a consequence of the action of certain gases emitted into the environment by human activities.

The destruction of the ozone layer in high proportions triggered the alarms, promoting an international agreement to act on the causes of the phenomenon. Among the main gases that destroy the ozone layer are chlorofluorocarbons (CFCs) and nitrogen oxides (NOx).

During 1989 the Montreal Protocol came into force to reduce the use of gases that degrade the ozone layer. This has resulted in the hole in the ozone layer over Antarctica reaching its minimum extent in 2019..

On the other hand, in January 2011 a small hole was detected at the North Pole, which lasted only that month. Later, in March 2020, another hole of about 20 million km was discovered that was temporary.

Article index

  • 1 Causes of the destruction of the ozone layer
    • 1.1 - Emission of gases that destroy the ozone layer
    • 1.2 - Increase in industrial activity
    • 1.3 - Agriculture dependent on agrochemicals
    • 1.4 - Non-compliance with international agreements
    • 1.5 - Increase in environmental pollution and alteration of ecosystems
    • 1.6 - Economic development model
  • 2 Processes
    • 2.1 Case of chlorofluorocarbons (CFCs)
    • 2.2 Nitrogen oxides (NOx) case
    • 2.3 Hole in the ozone layer: Antarctic and Arctic
  • 3 Consequences of the ozone hole
    • 3.1 - Biologically harmful radiation
    • 3.2 - Global warming
    • 3.3 - Deterioration of marine ecology
    • 3.4 - Reduction of food supply
  • 4 Solutions
    • 4.1 - Restriction on the production and use of gases that destroy the ozone layer
    • 4.2 - Degradation of potentially ozone-depleting gases
    • 4.3 - Recovery and recycling
    • 4.4 - Stratospheric ozone injection
    • 4.5 - Alternative technologies
    • 4.6 - Protection of ecosystems
    • 4.7 - Change of development model
  • 5 References

Causes of the destruction of the ozone layer

It is necessary to start from the fact that ozone is an unstable form of oxygen, so it is constantly forming and decomposing again into molecular oxygen (Otwo) and free oxygen (O). This forms a delicate balance that can be affected by various factors..

- Emission of gases that destroy the ozone layer

The fundamental cause of the destruction of the ozone layer is the emission of industrial gases that dissociate the stratospheric ozone. These gases include chlorofluorocarbons (CFCs) and nitrogen oxides (NOx), as well as others such as hydrofluorocarbons (HFCs).

Others are perfluorinated hydrocarbon (PFC) and sulfur hexafluoride (SF6), methyl chloroform used in industrial processes and halon used in fire extinguishers.

- Increase in industrial activity

Industrial activity. Source: -Estormiz 08:22, 24 September 2006 (UTC) / Public domain

The increasing industrialization worldwide is not only responsible for the emission of gases that destroy the ozone layer; It also has indirect effects, because it affects crucial processes for the maintenance of the ozone layer, such as the production of oxygen by polluting water..

On the other hand, other gases are generated that contribute to global warming, apart from those that directly damage the ozone layer, which in turn affects atmospheric circulation patterns, facilitating the formation of holes in the ozone layer..

- Agrochemical dependent agriculture

Today's agriculture is highly dependent on the use of chemicals that directly and indirectly affect the ozone layer. Directly by the use of pesticides that are ozone layer destroyers such as methyl bromide.

Likewise, chemical fertilizers contribute to the generation of nitrous oxides. In addition, by indirectly generating eutrophication processes, oxygen production in fresh and marine waters is reduced..

- Non-compliance with international agreements

The pre-eminence of economic interests over the maintenance of planetary ecological balances is expressed in non-compliance with international agreements. Industrialized countries such as the US and China openly limit or deny their support for agreements aimed at reducing global warming, arguing their economic interests..

- Increase in environmental pollution and alteration of ecosystems

Global environmental pollution causes both directly and indirectly the destruction of the ozone layer.

- Economic development model

In general terms, what is at the base of the problem of the destruction of the ozone layer is the economic model. A model based on the growing consumption of raw materials, on unbridled industrialization, generating a high amount of waste.

Processes

The destruction of the ozone layer is produced by the confluence of a series of factors, both natural and human-induced. The main element is the emission into the atmosphere of various gases that, when interacting with ozone, decompose it.

Atmospheric vortices caused by the development of low-pressure zones over the poles during winter concentrate these gases at low temperatures. The ice crystals that form in the cold and humid air mass in the stratosphere provide the surface for the different reactions..

Then at the beginning of spring the intensification of solar radiation drives the chemical reactions involved in the destruction of ozone.

Chlorofluorocarbons (CFCs) case

It begins when chlorofluorocarbons (CFCs) are photodisocyanized, that is, they decompose, under the action of high-energy ultraviolet radiation. This produces chlorine atoms and other halogens..

These chlorine atoms interact with ozone (O3) cause their decomposition by losing an oxygen atom. This occurs by the so-called chain reaction of the chlorine cycle, in which a chlorine atom joins with one of the oxygen atoms of ozone:

Ozone depletion by CFCs. Source: Artatoele / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

This produces chlorine oxide (ClO) and dioxygen or molecular oxygen (Otwo) and the ClO reacts with an oxygen atom, forming more dioxygen. Thus, the chlorine atom is released again, repeating the cycle and a single chlorine atom is capable of destroying around 100,000 ozone molecules..

  • Cl + O3 → ClO + Otwo
  • ClO + O3 → Cl + 2 Otwo

The ClO molecule removes an oxygen from the ozone molecule and the chlorine is free to return to step 1.

Nitrogen oxides (NOx) case

In this case it is the chain reaction of the nitrogen cycle, with nitrogen monoxide (NO) interacting with ozone (O3). NO captures an oxygen (O) from ozone (O3 ), producing nitrogen dioxide (NOtwo) and molecular oxygen (Otwo).

Then nitrogen dioxide (NOtwo) reacts with free oxygen (O) and nitrogen monoxide (NO) and molecular oxygen (Otwo). In this way the cycle continues indefinitely destroying thousands of ozone molecules.

Hole in the ozone layer: Antarctic and Arctic

Evolution of the ozone hole from 1979 to 2016

Although the destruction of the ozone layer occurs throughout the stratosphere, its greatest impact is at the poles, particularly the South Pole. Although holes are also formed in the ozone layer at the north pole, they are less frequent and of shorter duration..

The basis of ozone degradation reactions is the formation of stratospheric clouds of ice crystals. These clouds form at temperatures below -85 ºC, and in the Arctic (North Pole) temperatures rarely drop below -80 ºC.

Therefore, in this region the stratospheric clouds are made of nitric acid trihydrate crystals. While Antarctica (South Pole) is much colder, with temperatures of -90 ºC, forming ice crystals.

Consequences of the ozone hole

The fundamental consequence of the destruction of the ozone layer is the increase in ultraviolet radiation that manages to penetrate towards the Earth. This in turn brings a series of negative consequences for the ecological balance and life on the planet..

- Biologically harmful radiation

Ultraviolet radiation is part of the electromagnetic spectrum emitted by the Sun and has a high energy. This high energy deteriorates cell membranes and also affects DNA, generating mutations..

The level of damage it causes depends on the intensity with which it reaches the earth's surface and the tolerance of each living organism. This damage ranges from the destruction of leaf tissue in plants to skin cancer in humans..

In humans it also causes premature aging, cataracts, sunburns and depresses the immune system. This makes it more susceptible to disease, since this is the system that destroys viruses, bacteria and other harmful agents.

- Global warming

When the ozone layer is destroyed, the entry of ultraviolet radiation, of high energy value, increases. This causes greater global warming, which, together with the reduction in the escape of terrestrial heat due to the greenhouse effect, increases the average temperature..

- Deterioration of marine ecology

Ultraviolet radiation reaches deep layers of ocean water damaging the plankton that is the main base of marine food webs. On the other hand, plankton is the main source of oxygen, which is why the oxygen cycle is altered.

This generates a negative feedback, since the reduction of oxygen affects the formation of the ozone layer.

- Reduction of food supply

The higher incidence of ultraviolet radiation resulting from the destruction of the ozone layer negatively affects agricultural and livestock production as well as the productivity of aquatic ecosystems. Therefore, it has a decisive impact on the amount of food available, contributing to hunger in the world..

Solutions

There are several solutions to increase ozone levels:

- Restriction on the production and use of gases that destroy the ozone layer

The first thing is to attack the immediate cause of the deterioration of the ozone layer, that is to say to eliminate the use of gases that degrade ozone. This is what the Montreal Protocol has been aiming for since 1989, however its expansion is required.

Projection of recovery of the ozone layer. Source: NASA / Public domain

This is because new high impact gases are not included in said protocol, such as nitrous oxides..

- Degradation of potentially ozone-depleting gases

The use of microwave plasma sources has been experimented with to degrade gases that affect the ozone layer. By applying this technique, it has been possible to decompose the Freon HFC-134a gas by 84%, becoming smoke black, hydrogen and fluorine..

- Recovery and recycling

Another solution is to implement systems that allow the recovery and recycling of those gases that affect the ozone layer..

- Stratospheric ozone injection

Although some qualify this proposal as utopian, it is proposed to massively produce and inject fresh ozone into the stratosphere in order to compensate for its losses..

- Alternative technologies

One way to face the problem is the development of technological variants that do not require gases potentially destructive of the ozone layer. This merits the search for new technologies in areas such as refrigeration, transportation, fire extinguishers, control of agricultural pests and diversity of industrial processes..

- Protection of ecosystems

Especially relevant is the reduction of marine pollution and the loss of forests, due to the negative effect on the oxygen cycle.

- Development model change

It is essential to implement a sustainable development model, which reduces dependence on fossil fuels and the generation of waste.

References

  1. Canan, P., Andersen, S.O., Reichman, N. and Gareau, B. (2015). Introduction to the special issue on ozone layer protection and climate change: the extraordinary experience of building the Montreal Protocol, lessons learned, and hopes for future climate change efforts. Journal of Environmental Studies and Sciences.
  2. Colsa-Gómez, M.E., Heydrich, S.C. and Flores-Vklez, L.M. (1991). Causes and effects of the destruction of the ozone layer. Ecochemistry.
  3. Jasiński, M., Dors, M. and Mizeraczyk, J. (2009). Destruction of Freon HFC-134a using a nozzleless microwave plasma source. Plasma Chemistry and Plasma Processing.
  4. Kerr, R.A. (1991). Ozone destruction worsens. Science.
  5. Ravishankara, A.R., Daniel, J.S. and Portmann, R.W. (2009). Nitrous Oxide (N2O): The dominant ozone-depleting substance emitted in the 21st century. Science.
  6. Sánchez-Vega, M.V. (2008) The ozone layer. Biocenosis.
  7. Shevtsova-de Vargas, G. (1992). Heterogeneous processes in the Earth's atmosphere and their implication in the destruction of the ozone layer. Chemistry Magazine.

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