Solar radiation ozone protecting from

Above the troposphere, temperatures increase with altitude, reaching a maximum of nearly 2°C at about 50 km. This region of the atmosphere is called the stratosphere. The stratosphere contains a layer of ozone, a gas that helps shield Earth s surface from the Sun s harmful ultraviolet radiation. Ozone protects Earth by absorbing solar radiation, which raises the temperature of the stratosphere in the process. You read about the ozone layer in Chapter 1 as you began your study of chemistry. 

Ozone (O3) is formed in the tropical stratosphere, around 12 to 30 miles above the ground, where solar radiation is intense it then migrates to the polar regions. The O3 concentration can be as high as 10 ppm in the stratosphere there, it absorbs a large part of the harmfirl ultraviolet radiation from the sun, thereby protecting life on Earth. CFCs are volatile and persist in the lower atmosphere (the troposphere) because of their inert nature they resist chemical degradation reactions. It is estimated that... 

Ozone is an important gas in the atmosphere since, although it is only present in tiny quantities, it plays a vital role in protecting mankind from the harmful effects of solar radiation and a dominant part in determining the temperature structure of the atmosphere. 

High up in the atmosphere, around 20 km from the surface of the earth, the ozone layer acts as a shield and protects the earth from the harmful UV rays present in the incoming solar radiation. But for this layer, all life on earth would have been scorched. Ozone is used to sterilize drinking water and to remove bad odours and tastes. 

Because ozone selectively absorbs these deleterious wavelengths of solar radiation, it serves as an ultraviolet shield. As such, stratospheric ozone helps to protect humans and other organisms on Earth s surface from some of the harmful effects of exposure to this high-energy electromagnetic radiation, hi fact, without the protective action of the stratospheric ozone layer, it is likely that... 

Stratospheric ozone is produced at maximum rates in equatorial regions, where solar radiation is most intense. Ozone does not really occur as a layer, but instead as a broadly distributed gas whose peak concentration occurs in midstratosphere. The total amount of ozone present in the atmosphere is small, typically between 200 and 400 Dobson units. A Dobson unit is the amount of ozone that, if gathered together in a thin layer covering Earth s surface at a pressure of 1 atm, would occupy a thickness of 1/100 of a millimeter (10 gm). The entire ozone shield, which protects life on Earth from damage by the UV-B radiation of the Sun (ultraviolet radiation in the 280-320 nm range), is equivalent to a layer of ozone only 2 to 4 mm thick at sea level pressure. 

Another important environmental parameter of the early Earth was the flux of solar ultraviolet (UV) radiation. At present UV radiation with 200-300 nm length is adsorbed by the stratospheric ozone layer. This layer protects the biota from the harmful influence of dangerous UV radiation. In the early atmosphere the ozone was absent and harmful solar radiation may have reached the Earth s surface without any adsorption and prevented the formation of large, complex molecules for life origin. 

One of the most important chemical constituents in the middle atmosphere is ozone, because it is the only atmospheric species that effectively absorbs ultraviolet solar radiation from about 250-300 nm, protecting plant and animal life from exposure to harmful radiation. Therefore, the stability of the ozone layer (located near 15 to 25 km) is a central part of the study of the middle atmosphere. 

Present photosynthetic life is protected from harmful solar radiation by oxygen and ozone. Thus we must ask how these original creatures survived and evolved to the present state even as they formed the protective shield which their descendants would enjoy. It is possible that they were a form of algae, protected by liquid water from the sun s rays. It has also been suggested that primitive microbes could have been protected by layers of purine and pyrimidine bases, which absorb in the ultraviolet range (Sagan, 1973). 

The term antiozonant denotes any additive that protects rubber against ozone deterioration. Most frequently, the protective effect results from a reaction with ozone, in which case the term used is chemical antiozonant. Ozone is generated naturally by electrical discharge and also by solar radiation in the stratosphere. These sources produce ground-level ozone concentrations of 1-5 parts per hundred million (pphm). In urban environments, however, ozone reaches much higher levels, up to 25 (pphm) due to the ultraviolet photolysis of pollutants. Only a few parts per hundred million of ozone in air can cause rubber cracking, which may destroy the usefulness of elastomer products. Some desirable properties of an antiozonant additive are as follows ... 

Ozone Triatomic form of oxygen produced when diatomic oxygen is exposed to ultraviolent radiation (its presence in a stratospheric layer protects life-forms from harmfrd solar radiation). 

Contrast the ozone cycle with the atmospheric cycles that predominate on other planets Venus has a sulfuric acid cycle from its interior sulfur dioxide volcanoes, while Mars has a peroxide cycle from solar radiation shearing the oxygens off carbon dioxide. The Martian atmosphere has a little water in it, and even a trace of ozone built from these oxygen atoms, but its reactions are uncontrolled and out of kilter, making dangerous peroxide H Oj molecules. Their chemical cycles are destructive, but ours is protective. 

Ozone protects the Earth by absorbing harmful electromagnetic rays emanating from the Sim. Without the ozone these rays can reach the earth and damage vegetation and can cause skin cancer in people. This is particularly a problem when fair-skiimed non-indigenous people move into a country that receives high levels of solar radiation, such as Australia. 

Above the troposphere is the stratosphere, which reaches a height of 50 kilometers. At an altitude of 20 to 30 kilometers in the stratosphere lies the ozone layer. Stratospheric ozone acts as a sunscreen, protecting Earths surface from harmful solar ultraviolet radiation. Stratospheric ozone also affects stratospheric temperatures. At the lowest altitudes, the temperature is coolest because of the solar screening effect of ozone air at this altitude is literally in the shade of ozone. At higher altitudes, less ozone is available for shading and temperature increases all the way to a warm 0°C at the top of the stratosphere. 

Photochemical air pollution in the troposphere results from a complex interplay between sunlight and primary air pollutants emitted in ambient air that leads to the formation of ozone and other oxidizing and cye-irritaling agents. On the other hand, pollutants injected into the stratosphere by such human activities as supersonic transports (SST s) and release ofchlorofiuoro-methancs in air by their use as aerosol propellants and refrigerants may eventually reduce the protective layer of ozone from harsh solar ultraviolet radiation. Although the full impact of injected air pollutants in the stratosphere is not apparent at present, various model calculations show conclusively that the continuous future release of chlorofluoromethanes and NO (NO and N02) would result in substantial reduction of ozone in the stratosphere. 

The role of photochemistry in nature is difficult to overestimate especially when we consider conversion of solar energy into the chemical energy in natural photosynthesis or ozone production, which protects the Earth from hazardous UV radiation. Much less is known about the role of sunlight in environmental self-cleaning processes. 

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