Earthhas a natural sunscreen that shields it from the harmful radiationfrom the sun. The ozone layer is the natural sunscreen, a fragileband of gases that is about fifteen kilometres to forty kilometresabove the earth surface. However, due to human activities, there havebeen a substantial thinning of the ozone layer hence, ozonedepletion. Ozone depletion is the reduction of the ozone layer in thestratosphere. It can be explained in two but distinct relatedphenomena that scientist have observed since 1970s. Firstly, it canbe described as a steady ozone decline of about four percent of thetotal ozone available in the earth’s stratosphere. Secondly, it canbe explained as a decrease of springtime in the stratospheric ozonearound the Polar Regions (ozone hole). This essay discusses ozonedepletion, its causes, consequences, and strategies to minimize itseffects.
Ozonedepletion starts when CFCs are released into the atmosphere mostly byindustries. The CFC gases raises up to the stratosphere. Theultraviolet radiation breaks down the CFC gases to release chlorineatoms. Correspondingly, the realised chorine reacts with the ozoneand destroys it. The process repeat itself continuously causing moredepletion. Three forms of oxygen are involved in ozone layerdepletion. They include ozone gas, also triatomic oxygen (O3), oxygengas, also diatomic oxygen (O2), and oxygen atoms, also atomic oxygen(O). Ozone is formed when oxygen molecules photodissociate with thephoton. It converts single oxygen into two radicals of atomic oxygen.Next, the radicals of atomic oxygen combine with O2molecule creating two O3molecules. According to EW Team (n.p), one chlorine atom can breakdown more than one hundred thousand molecules of ozone. Thiscan be illustrated in the following equations. The radiation from thesun strikes the stratosphere to form Ozone. It splits oxygenmolecules (O2)into two oxygen molecules (O).
O2+hv → O+O
Then,the atomic oxygen further reacts with the oxygen molecule to formozone.
O+ O2 → O3
Theozone is then deflected by reacting with atomic oxygen.
O+ O3→ O2+O2
Thethree above chemical reactions are referred to as Chapman reaction.In other words, the ozone formation reaction is slower while ozonedecomposition is faster with an increase in altitude. The balance ofthe two complimentary reactions gives the concentration of the ozone.
TheMain Ozone-Depleting Substance
Themain causes of ozone depletion are pollution from chlorine andbromine chemicals, and human activities. Apart fromchlorofluorocarbons, (CFCs), other Ozone Depleting Substance (ODS)includes halons, carbon tetrachloride, methyl bromide, methylchloroform, and Hydrofluorocarbons. Chlorofluorocarbons (CFCs) andOzone Depleting Substances (ODS) are the main man-made chemicals thatare responsible for ozone depletion (McKenzie89).
CFCsaccounts up to eighty percent of the total stratospheric ozonedepletion. Before 1995, CFCs were used as coolants in freezers andrefrigerators, and as air conditioners in cars and buildings. CFCsare used in foam products such as rigid foam in home insulation orsoft-foam padding in cushions and mattresses.
Halonsare used in fire extinguishers where other equipment and materialscan be destroyed by water and other chemicals used in fireextinguishers. According to Gillespie(26),in B.C, halon caused a significant consequence of ozone depletioncompared to CFCs from automobile air conditioners.
Carbontetrachloride is commonly used in fire extinguishers and as solvents
Methylchloroform is used in industries for vapour degreasing, coldcleaning, and chemical processing. In addition, it is used inadhesives and aerosols.
Hydrofluorocarbonsare substitutes for CFCs. Although they are less harmful, they stillcause ozone deflection though not as much as CFCs. They are used invehicle air conditioning.
Further,other chemicals that deplete ozone are Hox, Noy, and Clx that belongsto the hydrogen, nitrogen, and chlorine families respectively.Unfortunately, human beings can do less to replenish the destroyedozone. All that they can do is to minimize CFCs in the air, as wellas be more responsible with manufacturing needs.
Consequencesof Ozone Layer Depletion
Ozonedepletion has increased the amount of ultraviolet radiation in theatmosphere. There are three categories of (UV) based on their energy:UV-A, UV-B and UV-C.UV-A has low energy hence, has low minimalbiological effects. On the other hand, UV-B has a higher energycompared to UV-A, and it is responsible for most damages in theliving organisms. UV-C never reaches the earth surface as it isabsorbed by oxygen in the atmosphere.
Ultravioletradiations have several negative consequences on the human being.Firstly, research confirms that the ultraviolet radiation causenon-melanoma skin cancer. Despite, it also plays a significant rolein malignant melanoma development. Secondly, the high levels ofultraviolet radiation have been associated with cataract illness (aneye ailment that covers the lens of the eye), blindness, and othereye diseases. In conjunction, it can cause damage to several parts ofthe eye such as the retina, conjunctiva, and retina, among others.According to McKenzie(190),cataracts are the world major causes of blindness. EW Team (n.p),urges that a sustained ten percent of thinning ozone layer result intwo million cases of cataracts annually, globally. Thirdly, theresearch proves that UV radiation causes premature aging of the skinand sunburns. Further, ultraviolet radiation weakens human immunesystem (immunosuppressant). Research show people with albinodisability have a low immune system when they are subjected to thesun for a long period.
Althoughthe damage that UV radiation on the plant cannot be seen, humans canfeel the impact. Just like human beings, UV radiation has negativelyaffected the plant growth, developmental and physiological processes.These include timing of development and growth of the plant, the waythe plant form, metabolism, and distribution of plant nutrients. As aresult, these have implications on the animals that feed on theseplants, plant competitive balance, biogeochemical cycles, and plantdiseases. Further, UV radiations also have negative impacts on themarine ecosystems. For instance, the phytoplankton is the mainfoundation of aquatic food. It grows closer to the water surfacewhere there is sufficient sunlight. According to Muller(115),the change of UV levels affects the growth and development ofphytoplankton hence, the aquatic life that feeds on them.Correspondingly, UV radiations affect the development of shrimp,fish, amphibians, crab, and other animals. Further, all other animalsthat feed on these animals are also affected. Plankton is the firstsignificant step in an aquatic food chain, and once affected, itaffects whole food chain. Despite, a decrease of phytoplanktondisrupts saltwater and fresh food chains leading to species shifts.Loss of biodiversity in the lakes, rivers, and oceans reduce fishyields for sports fisheries and commercial needs.
Accordingto Parker,Larry, and Wayne (156),excess exposure to UV radiation cause skin and eye cancer amonganimals. According to research conducted in United States, manyspecies of animals in the animal kingdom were found to suffer fromsunburn because of excess UV light. Besides, UV-B has been proved tocause cancer in the domestic animals similarly to the human beings.Nevertheless, animals are more protected compared to human beings dueto their skin pigmentation and heavy coats.
Impactson Agriculture, Forestry, and Natural Ecosystems
Mostof the major crop species are vulnerable to high ultravioletradiation. UV radiation causes reduced growth, flowering, andphotosynthesis. In addition, UV radiation reduces water-useefficiency, leaf area, leaf conductance, and dry matter production.As a result, the plant has growth limitation, yield reduction,enhanced fragility, and drought stress sensitivity. Some of thesespecies include barley, corns, soybeans, tomatoes, cauliflower,carrots, broccoli, cucumbers, peas, oats, wheat, and rice, amongothers. Additionally, ozone depletion has an adverse impact on theCanadian agricultural sector. According to the test conducted on theUV sensitivity of trees, UV negatively affects plant growth includingthe seedling.
Accordingto research, UV radiation degrades materials such as plastic, wood,fabric, rubber, and other construction materials. Parkeret. al. (160),argues that synthetic polymers are greatly affected by adverse solarUV radiation. Accordingly, an increase of UV-B accelerates theirbreakdown, as well as limits their lifetime while used in outdoors.Fortunately, people are now using special additives to protect themfrom UV-B.
Asthe result of the negative impacts of ozone depletion, almost twohundred nations have signed an international agreement (MontrealProtocol on Substance That Deplete the Ozone Layer) to end theproduction of CFCs, halons, and ODS. Since radiation, always reachthe earth surface, it is reasonable for every individual to takereasonable precaution to protect him or herself. For instance, avoidprolonged exposure when the sun is high and always sit in the shade.Additionally, one should wear protective clothing, sunglasses, andbroad-brimmed sunhat while basking in the sun. Furthermore, oneshould apply an effective sunscreen liberally especially afterswimming. As medics say, protection is better than cure, it is betterto protect ourselves from UV radiation rather than treat ailmentsthat result from them.
EWTeam. "ESRL Global Monitoring Division – ."ESRL Global Monitoring Division – . Web. 2 May 2015. .
Gillespie,Alexander. ClimateChange, and Air Pollution: Legal Commentaries Withinthe Context of Science and Policy.Leiden [u.a.: Nijhoff, 2006. Print.
McKenzie,Richard L., et al. "Ozone depletion and climate change: impactson UV radiation." Photochemical& Photobiological Sciences 10.2(2011): 182-198
Muller,Rolf. Stratospheric and Climate Change.S.l.: Royal Soc. of Chemistry, 2010. Print.
Parker,Larry, and Wayne A. Morrissey. Stratospheric.New York: Novinka books, 2003. Print.