STRATOSPHERIC OZONE PROTECTS EARTH FROM ULTRAVIOLET RADIATION

Stratospheric Ozone Protects Earth from Ultraviolet Radiation... 

STRATOSPHERIC OZONE PROTECTS EARTH FROM ULTRAVIOLET RADIATION... 

Ozone is an important component of the upper atmosphere, where it screens out ultraviolet radiation. In this way ozone protects Earth from the effects of these high-energy rays. For fhis reason, depletion of stratospheric ozone is a major scientific concern. (Section 18.3) In the lower atmosphere, however, ozone is considered an air pollutant. It is a major constituent of smog. (Section 18.4) Because of its oxidizing power, it damages living systems and structural materials, especially rubber. 

A chemical is any substance that has a definite composition. Ozone is a chemical that is made up of three particles of oxygen. Ozone forms a thick blanket above the clouds in the stratosphere. This layer of ozone protects Earth from overexposure to ultraviolet radiation from the Sun. You are probably familiar with the damage that exposure to ultraviolet radiation can do to your skin in the form of sunburn. Ultraviolet radiation can also harm other animals and plants. In the 1980s, scientists documented that the ozone layer arovmd Earth was becoming measurably thinner in some spots. 

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. 

Measurements of ozone (O3) concentrations in the atmosphere are of particular importance. Ozone absorbs strongly in the ultraviolet region and it is this absorption which protects us from a dangerously high dose of ultraviolet radiation from the sun. The vitally important ozone layer lies in the stratosphere and is typically about 10 km thick with a maximum concentration about 25 km above the surface of the earth. Extreme depletion of ozone in a localised part of the atmosphere creates what is known as an ozone hole. 

A particularly important property of ozone is its strong absorption in the ultraviolet region of the spectrum between 220-290 nm ( max255.3nm) this protects the surface of the earth and its inhabitants from the intense ultraviolet radiation of the sun. Indeed, it is this absorption of energy, and the consequent rise in temperature, which is the main cause for the existence of the stratosphere in the first place. 

Located several kilometres above the Earth s surface is the stratosphere. Here the ozone layer acts as a filter, protecting life on Earth from harmful low-wavelength ultraviolet radiation known as UV-C, which damages biological macromolecules such as proteins and DNA. In order to understand the effects of anthropogenic input into the stratosphere, the production and destruction of the ozone layer has been studied by a variety of photochemical models and experimental methods. 

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... 

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. 

The protective effects of an ozone layer in tile stratosphere of the earth have been known for many years. Ozone prohibits full penetration of ultraviolet radiation from the sun to the surface of the earth. Much research has been conducted and is still underway to determine the extent to which certain chemical pollutants may be destroying the ozone layer gradually and. among other factors, causing marked warming of the earth. 

Ozone A molecule made up of three atoms of oxygen. It occurs naturally in the stratosphere and provides a protective layer shielding the Earth from harmful ultraviolet radiation. In the troposphere, it is a chemical oxidant, a greenhouse gas and a major component of photochemical smog. 

Ozone depletion Destruction of the stratospheric ozone layer that protects the Earth from harmful effects of ultraviolet radiation. Depletion of the ozone layer is due to the breakdown of certain chlorine- or bromine-containing compounds (chlorofluorocarbons or halons), which break down when they reach the stratosphere and then catalytically destroy ozone molecules. 

Oxidizer Chemical substance that causes oxygen to combine with another chemical substance examples include oxygen and hydrogen peroxide Ozone depletion Destruction of the stratospheric ozone layer that protects the Earth from harmful effects of ultraviolet radiation. Depletion of ozone layer is due to the breakdown of certain chlorine- and/or bromine-containing compounds (chlorofluorocarbons or halons), which break down when they reach the stratosphere and then catalytically destroy ozone molecules Ozone layer Protective layer in the atmosphere, about 15 miles above the ground. The ozone layer absorbs some of the sun s ultraviolet rays, thereby reducing the amount of potentially harmful radiation that reaches the Earth s surface PAHs Polycyclic aromatic hydrocarbons... 

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. 

Earth s ozone layer plays a critical role in protecting Earth s surface from the Sun s harmful ultraviolet (UV) radiation. Every ozone molecule, which consists of three oxygen atoms, has the abihty to absorb a certain amount of UV radiation. Under normal circumstances, the ozone layer, which is located in the stratosphere between 15 and 50 kilometers (9 and 31 miles) above Earth, remains in a continuous balance between natural processes that both produce and destroy ozone. 

Oxygen is element number 8 and the most abundant element in Earth s crust. The pure element exists in two allotropic forms and O3 (ozone), which are both gaseous species under average atmospheric conditions. Diatomic oxygen gas, O, composes 21 percent of the atmosphere and is an essential biological element. Ozone composes a thin layer of the stratosphere and is essential to protecting life on the surface of Earth from otherwise harmful ultraviolet radiation. Unfortunately, in the troposphere, ozone is an air pollutant. 

The ozone layer protects Earth s surface from damaging ultraviolet (UV) radiation. Therefore, if the concentration of ozone in the stratosphere decreases substantially, more UV radiation wiU reach Earth s surface, causing unwanted photochemical reactions, including reactions correlated with skin cancer. Satellite monitoring of ozone, which began in 1978, has revealed a depletion of ozone in the stratosphere that is particularly severe over Antarctica, a phenomenon known as the ozone hole ( FIGURE 18.6). The first scientific paper on this phenomenon appeared in 1985, and the National Aeronautics and Space Administration (NASA) maintains an Ozone Hole Watch website with daily updates and data from 1999 to the present. 

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