The ozone layer

THE OZONE LAYER

The ozone layer. Didn't actually know what it was until recently. The English dictionary defined it; as a region of the stratosphere, between 15 and 30 kilometres in altitude, containing a relatively high concentration of ozone; it absorbs most solar ultraviolet radiation.

Image source

In a layman's definition or term it can simply be defined as the shield, shielding the earth from the harmful rays of the sun.

The ozone layer, or as i call it the ozone shield is the absorber of 97( ninety seven) to 99 (ninety nine) percent of our Sun's ultraviolet light of a medium frequency (from about 200 nm to 315 nm wavelength), which when living things are exposed to it, will surely be harmful and be dangerous and cause damage.

Image source

     **************************************

The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet (UV) radiation. It contains high concentrations of ozone (O3) in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere. The ozone layer contains less than 10 parts per million of ozone, while the average ozone concentration in Earth's atmosphere as a whole is about 0.3 parts per million. The ozone layer is mainly found in the lower portion of the stratosphere, from approximately 20 to 30 kilometres (12 to 19 mi) above Earth, although its thickness varies seasonally and geographically.

The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri Buisson. Measurements of the sun showed that the radiation sent out from its surface and reaching the ground on Earth is usually consistent with the spectrum of a black body with a temperature in the range of 5,500–6,000 K (5,227 to 5,727 °C), except that there was no radiation below a wavelength of about 310 nm at the ultraviolet end of the spectrum. It was deduced that the missing radiation was being absorbed by something in the atmosphere. Eventually the spectrum of the missing radiation was matched to only one known chemical, ozone.Its properties were explored in detail by the British meteorologist G. M. B. Dobson, who developed a simple spectrophotometer (the Dobsonmeter) that could be used to measure stratospheric ozone from the ground.
Source 1

Below is a picture of how how the ozone layer is measured;

Image source

A picture of the dobson spectrometer;

Image source

Now that we have seen what ozone layer means. It will be most appropriate, to move to the main point and that is the ozone layer depletion.

              DEPLETION

Firstly what is depletion. The dictionary defined depletion as; to reduce by destroying the vital part of something. Mankind in one way or another as contributed to the depleting of something vital(the ozone layer)

         OZONE LAYER DEPLETION

Ozone depletion describes two related phenomena observed since the late 1970s: a steady decline of about four percent in the total amount of ozone in Earth's stratosphere (the ozone layer), and a much larger springtime decrease in stratospheric ozone around Earth's polar regions. The latter phenomenon is referred to as the ozone hole. There are also springtime polar tropospheric ozone depletion events in addition to these stratospheric phenomena.

The main cause of ozone depletion and the ozone hole is man-made chemicals, especially man-made halocarbon refrigerants, solvents, propellants, and foam-blowing agents (chlorofluorocarbon (CFCs), HCFCs, halons), referred to as ozone-depleting substances (ODS). These compounds are transported into the stratosphere by the winds after being emitted at the surface. Once in the stratosphere, they release halogen atoms through photodissociation, which catalyze the breakdown of ozone (O3) into oxygen (O2).[3] Both types of ozone depletion were observed to increase as emissions of halocarbons increased.

Ozone depletion and the ozone hole have generated worldwide concern over increased cancer risks and other negative effects. The ozone layer prevents most harmful UVB wavelengths of ultraviolet light (UV light) from passing through the Earth's atmosphere. These wavelengths cause skin cancer, sunburn, and cataracts, which were projected to increase dramatically as a result of thinning ozone, as well as harming plants and animals. These concerns led to the adoption of the Montreal Protocol in 1987, which bans the production of CFCs, halons, and other ozone-depleting chemicals.

The ban came into effect in 1989. Ozone levels stabilized by the mid-1990s and began to recover in the 2000s. Recovery is projected to continue over the next century, and the ozone hole is expected to reach pre-1980 levels by around 2075. The Montreal Protocol is considered the most successful international environmental agreement to date.
Source 2

Image source

CAUSES OF OZONE LAYER DEPLETION

What causes the ozone layer to deplete?
Most of the factors that depletes the ozone layer are man-made factors. Which is caused by their various activities. From a layman's view what causes the ozone to deplete are the activities carried out by man e.g, like the burning of fossil fuels, burning of bushes and other flammable materials e.g.
But let's look at the main cause of ozone layer depletion in an advanced level.
The ozone in the ozone layer is being broken down by chlorine atoms from chlorofluorocarbon (CFC) molecules and bromine atoms from halons. CFCs and halons are produced by humans used in many applications such as refrigerants, anaesthetics, aerosols, fire-fighting equipment and the manufacture of materials such as stryrofoam. They were thought to be completely safe, chemically inert, and environmentally neutral. However it was soon found that they were not so ideal when they reached the upper atmosphere.

When CFCs reach the upper atmosphere they are first degraded by the very high energy of UV (ultra-violet) radiation. Degradation of CFC leaves a free chlorine atom. The basic cause of ozone layer depletion is that this chlorine atom then breaks up ozone molecules. Ozone then disappears. The chlorine atoms are recreated in subsequent reactions. One chlorine atom can destroy 100,000 ozone molecules.

Chlorofluorocarbon molecules in the stratosphere release chlorine atoms which break up ozone molecules to form oxygen.

Degradation of halons leaves a free bromine atom that destroys ozone in the same way as chlorine. CFCs and halons last a long time (100 years on average). After it was confirmed that an environmentally disastrous side-effect was taking place in the upper atmosphere, plans and agreements were made to phase out CFCs and halons. However, at the moment CFCs and halons are still being produced and are being put into the stratosphere about 5 times as fast as they can be removed naturally.
Source 3

Image source

When the ozone layer, that is the ozone shield , is destroyed or removed gradually the earth is left bare and unshielded to the sun's rays, thus affecting all living things negatively.

EFFECTS OF THE OZONE LAYER ON HUMANS
Ozone layer depletion increases the amount of UVB that reaches the Earth’s surface. Laboratory and epidemiological studies demonstrate that UVB causes non-melanoma skin cancer and plays a major role in malignant melanoma development. In addition, UVB has been linked to the development of cataracts, a clouding of the eye’s lens.
Because all sunlight contains some UVB, even with normal stratospheric ozone levels, it is always important to protect your skin and eyes from the sun. It also causes skin cancer and skin irritation
Source 4

IT'S EFFECTS ON MARINE ECOSYSTEMS
Phytoplankton form the foundation of aquatic food webs. Phytoplankton productivity is limited to the euphotic zone, the upper layer of the water column in which there is sufficient sunlight to support net productivity. Exposure to solar UVB radiation has been shown to affect both orientation and motility in phytoplankton, resulting in reduced survival rates for these organisms. Scientists have demonstrated a direct reduction in phytoplankton production due to ozone depletion-related increases in UVB.
UVB radiation has been found to cause damage to early developmental stages of fish, shrimp, crab, amphibians, and other marine animals. The most severe effects are decreased reproductive capacity and impaired larval development. Small increases in UVB exposure could result in population reductions for small marine organisms with implications for the whole marine food chain.
Source 5

IT'S EFFECTS ON PLANTS
UVB radiation affects the physiological and developmental processes of plants. Despite mechanisms to reduce or repair these effects and an ability to adapt to increased levels of UVB, plant growth can be directly affected by UVB radiation.
Indirect changes caused by UVB (such as changes in plant form, how nutrients are distributed within the plant, timing of developmental phases and secondary metabolism) may be equally or sometimes more important than damaging effects of UVB. These changes can have important implications for plant competitive balance, herbivory, plant diseases, and biogeochemical cycles.
Source 6

IT'S EFFECTS ON VARIOUS MATERIALS
Synthetic polymers, naturally occurring biopolymers, as well as some other materials of commercial interest are adversely affected by UVB radiation. Today's materials are somewhat protected from UVB by special additives. Yet, increases in UVB levels will accelerate their breakdown, limiting the length of time for which they are useful outdoors.
Source 7

IT'S EFFECTS ON BIOGEOCHEMICAL CYCLES
Increases in UVB radiation could affect terrestrial and aquatic biogeochemical cycles, thus altering both sources and sinks of greenhouse and chemically important trace gases (e.g., carbon dioxide, carbon monoxide, carbonyl sulfide, ozone, and possibly other gases). These potential changes would contribute to biosphere-atmosphere feedbacks that mitigate or amplify the atmospheric concentrations of these gases.
source 8

THE SOLUTIONS TO OZONE LAYER DEPLETION
during the years different and drastic measures have been taken to reduce the depletion of the ozone layer, and some of these measures are proven to be useful. Here are some of the solutions to ozone layer depletion.

Avoid products that results in ozone depletion

If you are out for shopping, don’t buy aerosol products with chlorofluorocarbons. Do check your fire extinguishers if “halon” or “halogenated hydrocarbon” is the main ingredient. Dispose of old air conditioning units, refrigerators that use chlorofluorocarbons to function. This could release the toxic chemicals into the atmosphere.

Advocate for ozone protection

Fertilizers and pesticides are extensively used in agriculture and are also a source of nitrous oxide production which is the main culprit in depletion of ozone layer. Encourage local political representatives to raise a campaign to put forth laws governing fertilizer use.

Speak to your family, friends, colleagues

Ozone layer depletion is something that could prove hazardous for the entire human community. Speak to your friends, family members, colleagues and encourage them to drive less, eat local, to dispose of fire extinguishers and air conditioning units containing ODS (ozone depleting substances).
Source 9

SOME OF THE PREVENTIVE MEASURES TO TAKE AGAINST OZONE LAYER DEPLETION

Replace halon-based fire extinguishers with others using foam.
Check on the label of the products, which we buy at the supermarket, to report that they do not damage the ozone layer.
Use your car only when necessary. The less we use our cars, the less pollutants we will emit into the atmosphere. Remember that burning fossil fuels breeds many substances that damage the ozone layer.
Do not buy refrigerators or air conditioner equipment that use CFCs as refrigerant. Look for this information in the labels, or ask the supplier of the product directly.
Do not use cleaning solvents containing CFCs or ammonia.
Do not use sprays, and do not buy objects made of plastic foam (dry ice or freezer). If you receive these products as a fill of your mail packages, return them immediately to the sender. Low consumption of these products will discourage plastic foam manufacturers.
Source 10

Image source

The movie industry has done many movies to remind people of thy dangers of ozone layer depletion and global warming. One of those films is; THE MAZE RUNNER

Image source

With all these if man respects his environment they won't be any cause to fear the ozone layer depleting.

Thanks for reading!!