Few days ago, I went to the market to buy groceries. It was almost close to mid day and the weather was too hot. I couldn't help but feel the hotness of the sun on my head, damn! I felt as if my head was on fire. I trekked for a while, hoping to see one of the commercial buses so as not to walk under the sun, but it seems like everyone had the same thing in mind. All commercial buses were filled to the brim. There wasn't even a space. I had no other option than to cover my head with my handkerchief and walk on to the market. Before then, I've also noticed that everytime I walk under the sun, my skin becomes darker.
While I walked, I couldn't stop thinking why we feel the hotness of a sun that is about 150 million kilometres from the earth (or there about). Can you imagine? the heat radiating from an object millions of miles away, so hot that I can't help but wonder if it's intention is to roast my brain. Damn, it is too hot, for crying out loud. Am quite sure that the weather wasn't as hot as this when I was a kid. What happened, what changed?
Am sure most of us have thought the same, now, for us to get to know the answer to this question, I will like us to meet, OZONE, we will also get to know why its not performing it's function properly.
OZONE
There is an unusual gas found in the atmosphere with each molecule containing about three atoms of oxygen (unlike the normal oxygen that we breath in that consist of only two atoms oxygen). This gas is called Ozone. Apart from the fact that it has a chemical symbol of O3, (unlike the breathable oxygen that has a chemical symbol of O2), the ozone can be differentiated from the oxygen gas as it is blue in colour, and also has a very strong odour while oxygen is colourless and odorless.
ATMOSPHERIC LAYERS
For us to fully understand ozone and ozone depletion, it is wise for us to get to know where it is found first, before we proceed. The earth's atmosphere is majorly divided into 5 basic layers. These layers are the stratosphere, troposphere, thermosphere, exosphere and the mesosphere.
Troposphere:-
The troposphere is the layer of the atmosphere that is closest to the earth's surface. This layer has a thickness that ranges from 4 to 12 miles and it contains up to half of the whole atmosphere. This is the layer were most of the water vapor, dust and others are found, and that's the reason why the cloud is found here. The air at this layer gets colder as one moves up.
The stratosphere:-
This is the second layer of the atmosphere, and it starts from where the troposphere stops to about 31 miles above the ground. This layer contains so much ozone and it has the function of heating up the atmosphere and also absorbing the harmful radiations like the ultraviolet rays from the sun. Since it doesn't contain water moisture, the air in this layer is quite dry and very thin (about 1000th times that of the air in the sea level). Since it's light and thin, jets and other aircrafts fly at this layer.
The mesosphere:-
This region of the atmosphere starts from where the stratosphere stopped and extends to about 53 miles above the ground. We call the upper part of the mesosphere the mesopause and it is the coldest part of the earth's atmosphere. The temperature at that top part is about -130°F. Even though that man have not really studied this layer due to the fact that satellites and space shuttles orbit are too high and balloons and jets can't go as high as that point, scientists know for sure that meteors burn up in this layer.
The Thermosphere:-
This layer starts from where the thermosphere end to up to 310-620 miles. This layer is quite hot, having temperature of up to 2700°F. Though this layer is considered as part of the earth's atmosphere, the density of the air at that layer is very low such that most times, we think of it as the outer space. This is the layer that the space shuttles fly and also where the international space station is currently orbiting the earth. Auroras occur at this layer too.
The Exosphere:-
This layer is the highest layer and also closest to the outer space. It is at this layer that the earth's atmosphere merges into the outer space. The air at this layer is extremely thin and it is majorly composed of particles of helium and hydrogen that are widely dispersed.
Note:-
As one moves from a lower layer to a higher layer, the atmosphere thins out till the gases dissipates in space. Also, there is no denoting boundary between our atmosphere and the sphere, but rather, what we have is an imaginary line called the karma line which is 62 miles from the earth's surface. Scientists have agreed that there is the point out atmosphere meets the outer space.
CLASSIFICATIONS OF OZONE
Based on the classification of the environmental scientists, we have two types of Ozone, the Good Ozone and the Bad Ozone. I will be explaining both of them below.
Good Ozone and how it is formed:-
The good Ozone is found existing naturally in the upper Stratosphere, thus it is called Stratospheric Ozone. We consider the layer of space that is between the range of 6 to 31 miles upwards above the the earth as the stratosphere. This good ozone is formed through natural means when the ultraviolet light from the sun strikes an oxygen molecules, and therefore divides this molecule into two separate oxygen atoms.
Gases in the air keeps reacting with each other, though we on earth don't really notice it. What happens next is that one of the dissociated oxygen atom combines with an 02 molecule thus forming a molecule with three oxygen which is known as Ozone. It is worth noting that even though this ozone is like a small percentage of all the gases in the stratosphere, it is called "good" because it has the most important function of shielding us from the ultraviolet ray from the sun. This ultraviolet ray is harmful to man and all that lives on earth.
Bad Ozone and how it's formed:-
The bad ozone is found in the layer that makes the immediate atmosphere, this later is the troposphere, and thus, another name for the bad ozone is the Tropospheric Ozone. This kind of ozone is not naturally found in nature, or formed due to nature's actions, rather it is as a result of Man's actions. They are usually a by-product of the chemical reaction between volatile organic compounds and oxides of nitrogen. This bad ozone is also created whenever chemicals found in factories, cars, power plants e.t.c react in the presence of ultraviolet light. This ozone is quite bad as it contaminates the air and even result to smog. Smogs are quite deadly, killing about 4000 people once in London.
WHAT IS OZONE LAYER DEPLETION
The term ozone layer depletion refer to the reduction in the amount of ozone in the stratosphere. What this means is that the there won't be any thing that would protect us from the direct ultraviolet rays of the sun, leaving us helpless to the mercy of the sun.
CAUSES OF OZONE DEPLETION
Ozone depletion is majorly by human action. These gases produced due to human actions, that causes ozone depletion are known as ozone-depleting substances (ODS). Some of these causes includes.
Production and Emissions of Chlorofluorocarbons (CFCs) :-
Factors are mostly responsible for the destruction of the ozone layer is elevated bromine and chlorine concentration and low temperatures. The concentration of chlorine and bromine in the atmosphere increases due to the production and emission of CFCs (chlorofluorocarbons) by man. When these gases gets to the atmosphere, they react, with low temperature acting as the catalyst. CFCs cause about 80% of the earth's ozone depletion.
Hydrochlorofluorocarbons (HCFCs) and Volatile Organic Compounds (VOCs) :-
Other substances that result to ozone depletion includes some volatile organic compounds and hydrochlorofluorocarbons (HCFCs). This compounds are mainly emitted as a by-product of fuel combustion in vehicles, as a result of industrial processes, aerosols, leakage of refrigerants e.t.c. Even though that these gases are known to be stable in the lower part of the atmosphere, when they get to the stratosphere, they become exposed to ultraviolet radiation resulting to them breaking to free atoms which causes ozone depletion.
Chlorine Monoxide:-
When chlorine molecules dissociate into two separate free atoms, this free atoms goes up to react with the ozone to form a molecule of oxygen and chlorine monoxide (ClO). This chlorine monoxide formed now reacts with the ozone forming a chlorine atom and 2 oxygen molecules. Just like a chain reaction, this chlorine atom formed now reacts with the ozone again to form chlorine monoxide, and the entire process repeats itself again. It is worth noting that only one atom of chlorine can break up 100,000 ozone molecules.
VOLCANOES AND ITS EFFECT ON THE OZONE LAYER
Volcanoes itself contribute to ozone depletion. When ozone erupts, it creates a very huge cloud of ashes. These ashes goes up to the troposphere and from the troposphere they drift up to the stratosphere. Remember that the stratosphere is also where the ozone layer is.
Normally, ashes from volcanoes contain very high amount of bromine and chlorine, and when these ashes gets to the atmosphere, they are not easily removed. In fact, they can stay up to two to five years in the stratosphere, and while they are there, they react with the ozone molecules.
The reason for this reaction is because these gases contained in the volcanic ash are members of the halogens. The halogens have 7 electrons in their outermost shell, which means that they just need only one electron to achieve the octate state of the noble gases. When these elements get to the atmosphere, they get this needed electron from the ozone gas.
Some other gases found in volcanic ashes that result to ozone depletion includes the hydrogen chloride, but that one posses little threat since it gets easily flush down by rain. Yet still, some escape into the stratosphere and cause their own havoc. Volcanoes are even more dangerous as it can spread its ashes over a wide range of area, leading to a quicker and broader ozone depletion. Yet still, volcanoes only contribute to about 20% of chlorine addition to the atmosphere, while the rest 80% is due to man's activities.
WHAT IS OZONE HOLE
Unlike what people think, ozone hole is not really a whole in the atmosphere where there is no ozone at all, rather, it is a region in the stratosphere where the ozone layer is exceptionally depleted. It was observed first in 1979, when there was an exceptional depletion of the ozone over Arctic and Antarctic. This "hole" formed is said to be as big as America. This phenomenon is mostly observed every year, during spring season over the Antarctic.
The reason for this is that, during the winter in Antarctic the temperature of that region drops as low as -109°F leading to the formation of ice which is a mixture of sulphuric acid amd nitric acid in the cloud.This mixture formed then reacts with other substances in the cloud causing the release of CFCs which results to massive ozone depletion.
Ozone depletion doesn't occur only in Antarctic, rather it occurs in places where the population is very dense. But whenever it is spring, the "hole" covers as the ozone layer gets replenished through natural means.
CONSEQUENCES OF OZONE LAYER DEPLETION
Before we get to understand the consequences of ozone depletion, we need to know that there are basically two harmful ultraviolet rays that reaches the earth. Those rays are the ultraviolet A rays known for its long wavelength and the short Ultraviolet B rays. Both of them are very dangerous.
Those consequences includes
Increase in amount of ultraviolet radiation:-
As I said earlier, the ozone layer is the part of the earth's atmosphere that is responsible for the absorption of ultraviolet radiation. If this ozone layer gets depleted, there is surely going to be an increase in the amount of ultraviolet radiation on earth. Thus, man and everything living on earth will be left to face these rays.
UVB which has a low wavelength can be easily blocked by the ozone layer, but with the ozone layer depleting, it can easily penetrate and cause serious harm on earth.
Effects on crops:-
Whenever there is an increase in the amount of ultraviolet radiation, crops are seriously affected. This is because, most of these plants of great economic importance like rice depend greatly on a bacteria known as the cyanobacteria for the retention of nitrogen.
This cyanobacteria, though it resides on the root of these plants are very sensitive to ultraviolet radiation, thus, if there is an increase in ultraviolet radiation they might die.
Another effect is that, an increase in ultraviolet radiation can really limit the growth of a plant and even alter timing of plants production. In some plants, an increase in ultraviolet radiation can result to a change in the time of flowering of the plant. It even reduces the number of flowers produced by a plant.
Effects on Marine Ecosystem:-
These two organisms, phytoplankton and bacterioplankton really play a major role in food chain and also in carbon cycle. These marine organisms, are responsible for converting atmospheric carbon dioxide to oxygen. It is unfortunate that their existence is been threatened by UV radiation. Ultraviolet rays affects their mobility and also their orientation, and since these microorganisms behavior are disturbed, the whole order of the entire ecosystem gets affected too.
Effects on Animals, both land and sea:-
An increase in the ultraviolet radiation results to sun burns in the body of animals. In the Gulf of California, More than 150 whales have been found to be suffer epidermal damage, and this damage can only be associated to serious sunburn. Amphibians themselves have been highly affected by this ozone depletion. In fact, the reduction in the number of amphibian species in the world have also been attributed to an increase in the ultraviolet rays.
The reason for that is because, this radiation affects their life growth, leads to deformities in some species of this animal, causes a reduction in the immunity resulting to a higher tendency of falling sick e.t.c. Other effects includes, changes in behaviours and patterns of these animals, hampering of growth and even blindness in some species.
Effects on Human:-
Humans also receive their own fair share of the consequences of ozone depletion. One of the effects is the skin cancer. Other include eye damage, immune system damage e.t.c.
Skin Cancer:- This is one of the most noticeable effects of ultraviolet radiation after sun burn. Due to the excessive exposure to these harmful rays, humans develop skin cancers like the basal and squamous cell carcinoma, and the malignant melanoma.
Eye damage:-Excessive exposure to ultraviolet radiation can also cause either total blindness, photokeratitis (snow blindness) or even cataracts.
Pixabay.com: Exposure to Ultraviolet radiation causes blindness
Immune system damage:- Just as what happens in animal, ultra violet radiation also affects humans immune system, making it very weak and prone to diseases.
Accelerated aging of skin:- This effect is more easily noticed in fair-skinned people than the dark-skinned people. When people get exposed so much to ultraviolet radiation, they develop an allergy known as photoallergy which is responsible for the rashes in fair-skinned people.
Other effects on human:- Other effects of ozone depletion on man is noticed when man breaths in ozone gas, as it causes chest pain, throat irritation, difficulty in breathing e.t.c.
Increased tropospheric Ozone:-
An increase in ultraviolet radiation results to an increase in the amount of tropospheric ozone. Remember the Tropospheric ozone? The bad ozone? I guess you remember now. Bad ozone are not good since they are very toxic and have a very high oxidant properties. They are produced as a result of the action of ultraviolet radiation on gases produced by vehicle exhaust. Bad ozone is very harmful, especially for children with asthma and other respiratory problems, as it makes breathing very hard for them.
Increased production of vitamin D:-
Ultraviolet light produces Vitamin D in the skin. Thus, an increase in ultraviolet radiation equals an increase in the production of vitamin D in the skin. Even though this looks like a good news, it is quite a very bad one. The reason is that the body doesn't need vitamin D so much, in fact, it even prevents it's production if it's exceeds the body requirement. If there is so much vitamin D in the body, it causes an excessive increase in the blood calcium and also increases one's mortality.
IN CONCLUSION / WHAT CAN WE DO
We have seen the terrible effects of ozone depletion, and how serious the danger we are in right now is, it is of utmost importance for us to do something to prevent further ozone depletion. If we can find a way and put a stop to these causes of ozone depletion, we won't suffer these effects anymore as the ozone layer will replenish itself through natural means.
But what can we do? Most people have came up with the idea that man should produce ozone gas in a very large quantity and then inject it into the stratosphere so as to replenish the lost ozone layer quickly. Though it sounds brilliant, it is not feasible. The reason why it it isn't a good idea is because an immense amount of energy is required to produce ozone. The one naturally occurring in the stratosphere is produced due to the energy supply from the sun. If man decides to replicate that act, we will need about two times the energy used by the whole United States.
Thus, the best way to stop ozone depletion is by preventing the introduction of the halogens and the CFCs into the stratosphere. We can achieve that by putting an end to the production and the usage of CFCs and even find a way to prevent these halogens from escaping into the stratosphere.
One of the ways we can do that is by putting an end to the use of olden refrigerators and air conditioners as they make use of these harmful chemicals as refrigerant.Also, we should think of a better way for killing of pest as some of these pesticides contain some of these gases that causes ozone depletion.
Finally, there is a need for our cars and power plants to run on other clean and renewable sources of energy and not fossil fuels, since these fuels releases some of these harmful gases. If man will finally actualize his dream of powering all his machines with only renewable source of energy, it will be the last we will hear of Ozone depletion.
REFERENCES
Causes and effects of ozone depletion