The perilous effect of ozone depletion is taking a toll on the living organisms on earth thus preservation of ozone has become our major concern.
What is ozone?
Ozone acts like a sunscreen around our planet that absorbs 93-99% of the sun’s high-frequency ultraviolet light that potentially casts damage on lives on earth. The ozone layer is present in the lower portion of the stratosphere (15-35 km from the earth). It is pale blue in colour, harsh odour and highly reactive in nature.
Ozone is an inorganic molecule that is made up of three oxygen molecules (O3) . It is produced through photo-disassociation of oxygen caused by ultraviolet radiation and it’s a reversible reaction that is balanced by nature itself.
O3_ O2 +O
Effect of ozone on earth
Thinning of ozone is affecting flora and fauna on earth. The high radiant energy of UV rays is harmful for the living creatures. It is causing serious diseases like Skin cancer, eye injuries, weaken immune system etc. Ultraviolet radiation Slows down the photosynthesis process damaging the growth of plants. Depletion of ozone is one of the cause of planet’s rising temperature. The effect may be insidious but grievous.
Cause of Ozone depletion
Nature was at its peace. Again its human intervention that has led to the depletion of ozone. The main agent of ozone depletion is CFCs (Chlorofluorocarbon). Chlorofluorocarbon is composed of Chlorine, Fluorine and Carbon. The molecule of CFCs is long surviving and non-reactive. It drifted up and globally distributed in the stratosphere. At the high altitude where the intensity of ultra-violate radiation is immensely high, CFCs split apart and released chlorine atom which is the culprit of O3 depletion. One chlorine can destroy 100,000 molecules of ozone. It destroys more quickly than O3 is created.
CL + O3 = CLO + O2
When the molecule of chlorine monoxide (CLO) combines with other molecules of oxygen it destroys another molecule of O3.
CLO + O = CL + O2
Subsequently, the chain of reaction rapidly destroys the ozone.
Besides CFCs Halon gases also deleterious for the ozone. Halons are Bromine or fluorine combined with one or two carbon atoms. Formerly Halons were in use in the aerosol spray cans and refrigerants.
Some eco-friendly cleaning products have chlorine and Bromine realising substances that find a way into the atmosphere and affects the ozone layer.
The reaction occurs in the same process in Br (Bromide), No (Nitrogen) and H (Hydrogen).
03 + Br = Bro + O2 ……
Bro + O = Br + O2 (Bromine monoxide) + Oxygen
O3 + NO = NO2 + O2 ……
O + NO2 = NO + O2 (Nitrogen monoxide) + Oxygen
O3 + H = OH + O2 ……..
O + OH = H + O2 (Hydrogen monoxide) + Oxygen
Certain natural factors cause ozone depletion like sun-spots, stratospheric winds and volcanic eruptions. But it affects only 1-2% of the total crisis.
The perilous impact of Chlorofluorocarbons on ozone first reported in 1970 by professor of chemistry at California University Dr Rowland and Irvine and Molina two postdoctoral fellow in Rowlands laboratory. Later in 1995 Rowland and Molina along with Paul J Crutzen shared Nobel Prize for their landmark research. At those time CFCs were widely used in refrigerators, air-conditioners and aerosol spray cans. For their non-toxicant and non-inflammable nature.
To this staggeringly serious report, Montreal Protocol was proposed in 1987 to phase out the production and use of ozone depletion chemicals. Hydrochloflurocarbons, HCFCs introduced and replaced the CFCs. However, CFCs are so tenacious that it will take many years to be completely erased from the atmosphere.
Hydrochloflurocarbons or HCFCs compound contains carbon, hydrogen, chlorine and fluorine. The HCFCs have shorter atmospheric life than CFCs but still delivers chlorine which has the potential to harm the ozone layer. HCFCs is only temporary substitute for CFCs. Research is in the pipeline for a more viable answer. International legislation has mandated production caps for HCFCs, production is prohibited after 2020 in developed counties and 2030 in underdeveloped countries.
What makes HCFCs adoptable over CFCs?
The carbon-hydrogen bond in HCFCs makes it a less stable compound. Hydrogen attached with Carbon quickly reacts with the hydroxyl radicals in the troposphere. So HCFCs oxidizes in the troposphere and the released chlorine soon combines with other chemicals, the freshly formed compounds get dissolve in water and ice and obliterate from the atmosphere through precipitation. Only a certain portion of HCFCs molecules reached the stratosphere and participated in an ozone depletion reaction. Because the photolysis rates of HCFCs is much slower the release of chlorine is proportionately less and these properties expected to deplete much less stratospheric ozone than CFCs.
Despite Montreal protocol, human awareness is imperative to terminate the crisis. We should put a stop to the use of dangerous gases – CFCs (chlorofluorocarbons), halogenated Hydrocarbons, methyl bromide and nitrous oxide.
NASA began measuring Earth’s stratospheric ozone in 1979. Ozone concentration has declined significantly over the Antarctic region enlarging the ozone hole. After the Montreal action, the ozone level has stabilised but restoration is still decades away.