Ozone depletion is a phenomenon that reduces the amount of ozone in the stratosphere more precisely, in the ozonosphere. This is a very dangerous process because the ozone layer protects us from ultraviolet radiation by absorbing a large part of the rays that reach the Earth from the sun.
Ozone is formed and decomposed under the influence of sunlight, therefore its fluctuations over the year are noted. Nevertheless, scientists noticed a marked decrease in the ozone content in the stratosphere in the s and proved that this is an anthropogenic loss.
This means that people are to blame for this state of affairs, and more specifically the increased emission of freons used in the production of aerosols. Stratospheric ozone is produced by the action of UV rays on oxygen molecules. Ozone reacts with the chlorine atoms and breaks down into ordinary diatomic oxygen. These reactions continue until the chlorine is completely removed or … the ozone particles are depleted. Unfortunately, the freon particles do not break down in the troposphere and do not react with other substances; they can circulate in the atmosphere for up to years without any damage.
They only decompose when they enter the ozonosphere. It was calculated that the ozone content decreased at an alarming pace — at the equator by about 0. Why are the polar regions particularly vulnerable?
Unfortunately, gases, including CFCs, travel throughout the atmosphere and reach the poles as well. Even though Antarctica is very far from the largest emission sources, Europe and the United States, it still reaps a toll on mistakes made in highly developed countries. The problem is made even more difficult by the polar night — due to the long period of underexposure, ozone is produced much slower, while its decomposition caused by pollution does not stop at all.
Ozone is destroyed faster than produced, and this heralds a systematic reduction of the ozone layer and … an ecological catastrophe. Why is the ozone hole such a pressing problem?
It turns out that it can have very serious consequences for life as we know it. The main task of stratospheric ozone is to absorb UV rays, which can be very harmful to living organisms. This process, known as convection, means there are huge air movements that mix the troposphere very efficiently.
Virtually all human activities occur in the troposphere. Everest, the tallest mountain on the planet, is only about 5.
The next layer, the stratosphere stratosphere The region of the atmosphere above the troposphere. The stratosphere extends from about 10km to about 50km in altitude. Commercial airlines fly in the lower stratosphere. The stratosphere gets warmer at higher altitudes. In fact, this warming is caused by ozone absorbing ultraviolet radiation.
Warm air remains in the upper stratosphere, and cool air remains lower, so there is much less vertical mixing in this region than in the troposphere. Most commercial airplanes fly in the lower part of the stratosphere. Health and Environmental Effects of Ozone Depletion. Ozone Layer Research and Technical Resources.
Information for students about the Ozone Layer. Addressing Ozone Layer Depletion. Adapting to a Changed Ozone Layer. Phasing Out Ozone-Depleting Substances. Managing Refrigerant Emissions. Most atmospheric ozone is concentrated in a layer in the stratosphere, about 9 to 18 miles 15 to 30 km above the Earth's surface see the figure below. Ozone is a molecule that contains three oxygen atoms. At any given time, ozone molecules are constantly formed and destroyed in the stratosphere.
The total amount has remained relatively stable during the decades that it has been measured. The ozone layer in the stratosphere absorbs a portion of the radiation from the sun, preventing it from reaching the planet's surface.
UVB is a kind of ultraviolet light from the sun and sun lamps that has several harmful effects. It is a cause of melanoma and other types of skin cancer.
It has also been linked to damage to some materials, crops, and marine organisms. The ozone layer protects the Earth against most UVB coming from the sun. It is always important to protect oneself against UVB, even in the absence of ozone depletion, by wearing hats, sunglasses, and sunscreen. However, these precautions will become more important as ozone depletion worsens.
UVB has been linked to many harmful effects , including skin cancers, cataracts, and harm to some crops and marine life. Scientists have established records spanning several decades that detail normal ozone levels during natural cycles.
Ozone concentrations in the atmosphere vary naturally with sunspots, seasons, and latitude. These processes are well understood and predictable. Each natural reduction in ozone levels has been followed by a recovery. Beginning in the s, however, scientific evidence showed that the ozone shield was being depleted well beyond natural processes. When chlorine and bromine atoms come into contact with ozone in the stratosphere, they destroy ozone molecules.
One chlorine atom can destroy over , ozone molecules before it is removed from the stratosphere. Ozone can be destroyed more quickly than it is naturally created.
Atmospheric ozone is sometimes labeled as the "good" ozone, because of its protective role, and shouldn't be confused with tropospheric, or ground-level, "bad" ozone, a key component of air pollution that is linked with respiratory disease. Ozone O 3 is a highly reactive gas whose molecules are comprised of three oxygen atoms. Its concentration in the atmosphere naturally fluctuates depending on seasons and latitudes, but it generally was stable when global measurements began in Groundbreaking research in the s and s revealed signs of trouble.
In , Mario Molina and Sherwood Rowland , two chemists at the University of California, Irvine, published an article in Nature detailing threats to the ozone layer from chlorofluorocarbon CFC gases.
At the time, CFCs were commonly used in aerosol sprays and as coolants in many refrigerators. As they reach the stratosphere, the sun's UV rays break CFCs down into substances that include chlorine. One atom of chlorine can destroy more than , ozone molecules, according to the U. Environmental Protection Agency, eradicating ozone much more quickly than it can be replaced.
The "hole" is actually an area of the stratosphere with extremely low concentrations of ozone that reoccurs every year at the beginning of the Southern Hemisphere spring August to October. Spring brings sunlight, which releases chlorine into the stratospheric clouds.
Recognition of the harmful effects of CFCs and other ozone-depleting substances led to the Montreal Protocol on Substances That Deplete the Ozone Layer in , a landmark agreement to phase out those substances that has been ratified by all UN member countries. Without the pact, the U.
More than 30 years after the Montreal Protocol, NASA scientists documented the first direct proof that Antarctic ozone is recovering because of the CFC phase-down: Ozone depletion in the region has declined 20 percent since And at the end of , the United Nations confirmed in a scientific assessment that the ozone layer is recovering, projecting that it would heal completely in the non-polar Northern Hemisphere by the s, followed by the Southern Hemisphere in the s and polar regions by A study in early found that ozone in the lower stratosphere unexpectedly and inexplicably has dropped since , while another pointed to possible ongoing violations of the Montreal pact.
The world is not yet in the clear when it comes to harmful gases from coolants. Some hydrochlorofluorocarbons HCFCs , transitional substitutes that are less damaging but still harmful to ozone, are still in use.
Developing countries need funding from the Montreal Protocol's Multilateral Fund to eliminate the most widely used of these, the refrigerant R The next generation of coolants, hydrofluorocarbons HFCs , do not deplete ozone, but they are powerful greenhouse gases that trap heat, contributing to climate change.
Though HFCs represent a small fraction of emissions compared with carbon dioxide and other greenhouse gases , their planet-warming effect prompted an addition to the Montreal Protocol, the Kigali Amendment , in
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