Cfcs And Ozone Depletion

By Author: Henry Ford
Total Articles: 189
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Climate change is the most important concern for the world in the 21st century. Since the second half of the twentieth century, the world has experienced a number of changes that can be attributed to climate change. Climate change results from increase global warming which is attributed to increases emission of green house gases that destroys the ozone layer. Depletion of ozone layer can be described as two distinct but closely related observations. First, there is slow but steady decline in the total volume of the ozone layer found on the earths stratosphere which has been observed since 1970s. It is recorded that the ozone layer has decreased by 4 percent for every decade. Second, there is larger but seasonal decrease in the stratospheric ozone covering the earth’s Polar Regions which has happened during the same time period (Benedick, 1991). The latter is regarded as ozone hole that plays important role in regulation of the world’s temperature. In addition to these two common phenomena, recent studies shows that ozone depletion is complemented by troposphere ozone depletion events which mostly takes place in the polar ...
... region surface in spring.
In order to understand the mechanism of ozone depletion is important to understand the process through which ozone is depleted. The most important process that has been used to explain depletion of ozone layer is the catalytic destruction with chlorine and bromine. These are to atoms which are considered very destructive to the ozone layer. These two atoms are mainly contributed to the stratosphere through photodissociation of cholorofluorocarbon (CFC) compounds. CFC compounds are mainly found in the in freons and bromofluorocarbon compounds referred to as halons (Benedick, 1991). The catalytic reaction that destroys ozone layer takes place in stratosphere which means these compounds have to travel all the way to the stratosphere once they are released on the earth’s surface. It is has been observed that ozone depletion mechanism grow in strength with increased emission of CFS and halons in the stratosphere.
CFC and other chlorine and bromine containing compounds are the main elements that have increased ozone depletion catastrophe. CFCs were developed in 1930s and have been used for various industrial uses. They are also used in commercial and household applications like mattresses. CFCs are:
• non-toxic substances
• Non-flammable
• Non reactive
Due to the above characteristics, they have been found most suitable to make household appliances that may be threatened by the above conditions. They are also very stable as far as their thermodynamic characteristics are concerned. This makes them ideal to be used as coolants for both commercial and home refrigeration (Roan, 1989). They are also used as aerosol propellants, electronic cleaning solvents, and also as blowing agents. The production of CFCs has been fueled by the demand in the above mentioned conditions. Their increased use has continued to harm the environment by accelerating destruction of the ozone layer.
It was not until 1973 when chlorine was confirmed to be a catalytic agent that was playing a greater role in the destruction of ozone layer. The catalytic destruction process takes place when the destroyer removes an odd oxygen species. Normally ozone layer is made of three atoms of oxygen i.e. O3. Chlorine removes the extra unstable oxygen molecule but it is left unaffected which means it continues to persist in the environment. It is through this process that chorine has been confirmed to be destructive to the environment. In 1984, it was conclusively discovered that chorine was playing a major role in catalytic reactions that led to destruction of the ozone layer. The process of ozone depletion was difficult to note before this discovery was made. Scientists noted that polar ozone had been greatly depleted in Antarctica and this prompted scientists to carry out more experiments which confirmed that in deed ozone layer was being destroyed by chlorine.
The chemistry behind ozone depletion is complex and can be explained in the following ways:
CFCs can lead to complex reactions in stratosphere which leads to ozone depletions. These reactions have been found to be more common in Antarctica regions where there is an ozone hole. Scientists have discovered that there is a complex scenario in the atmosphere that pertains to ozone depletion. They discovered that complex reactions at the stratosphere which are caused by CFCs and chlorine had overall effect on solar radiation. They discovered that the process was notable in the Polar Regions in Antarctica and northern hemispheres especially when warm temperatures were more prevalent (Newman, Kawa and Nash, 2004).
The ozone layer is a allotrope of oxygen that is made up of three oxygen molecule. (O3). The ozone is poisonous if breathed by humans but it plays important role in life. It has been known to filter out and abuser short wavelengths of ultraviolet radiation which range between 280 – 320 mm. These wavelengths can cause serious harm to human skin leading to cancers and other disorders like eye disorders (Weatherhead and Andersen, 2006).
CFCs are inert and insoluble. This means that once they are released to the environment, they are not destroyed nor are they dissolved by rain. They tend to remain in the atmosphere for a very long period of time from where they can diffuse into the stratosphere.
It is in the stratosphere that CFCs contact the short wavelength ultraviolet radiation. The u.v radiation reacts with CFCs and split chlorine atoms from the CFCs in the following process –
CCl3F(g) ---------------> CCl2F(g) + Cl (g)
u.v radiation
This reaction is mediated by ultraviolet radiation
When the chlorine molecule is freed from CFCs molecule, it reacts with ozone layer to release one oxygen molecule in the following reaction –
Cl(g) + O3(g)------------->ClO(g) + O2(g)
Ozone layer is split into one oxygen molecule that reacts with chlorine and water.
The split of ozone into oxygen molecules increases the number of oxygen molecules in the stratosphere. These oxygen molecules are important in regeneration of chlorine atoms which continue with the catalytic reaction. This means that one CFC molecule which is released into the environment cha continue to destroy many ozone molecules.
Up do date, there is no formula that has been discovered that can reverse the destruction of ozone layer. The only proposed solutions include substitution of CFCs with other chemicals that are not destructive to the ozone layer (Karen, 1994). It has been proposed that use of CFCs in some compounds should be replaced with hydrochlorofluorocarbons which have only 1 hydrogen atoms. The bond between carbon and hydrogen makes the reactive in the atmosphere which means once in the atmosphere, they will be split.

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