Answers%20to%2020%20questions - Q1 What is ozone and where...

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Q1: What is ozone and where is it in the atmosphere? Ozone is a gas that is naturally present in our atmosphere. Each ozone molecule contains three atoms of oxygen and is denoted chemically as O 3 . Ozone is found primarily in two regions of the atmosphere. About 10% of atmospheric ozone is in the troposphere, the region closest to Earth (from the surface to about 10- 16 kilometers (6-10 miles)). The remaining ozone (90%) resides in the stratosphere, primarily between the top of the troposphere and about 50 kilometers (31 miles) altitude. The large amount of ozone in the stratosphere is often referred to as the “ozone layer.” Q2: How is ozone formed in the atmosphere? Ozone is formed throughout the atmosphere in multistep chemical processes that require sunlight. In the stratosphere, the process begins with the breaking apart of an oxygen molecule (O 2 ) by ultraviolet radiation from the Sun. In the lower atmosphere (troposphere), ozone is formed in a different set of chemical reactions involving hydrocarbons and nitrogen-containing gases. Q3: Why do we care about atmospheric ozone? Ozone in the stratosphere absorbs some of the Sun’s biologically harmful ultraviolet radiation. Because of this beneficial role, stratospheric ozone is considered good ozone.” In contrast, ozone at Earth’s surface that is formed from pollutants is considered “bad ozone” because it can be harmful to humans and plant and animal life. Some ozone occurs naturally in the lower atmosphere where it is beneficial because ozone helps remove pollutants from the atmosphere. Q4: Is total ozone uniform over the globe? No, the total amount of ozone above the surface of Earth varies with location on time scales that range from daily to seasonal. The variations are caused by stratospheric winds and the chemical production and destruction of ozone. Total ozone is generally lowest at the equator and highest near the poles because of the seasonal wind patterns in the stratosphere. Q5: How is ozone measured in the atmosphere? The amount of ozone in the atmosphere is measured by instruments on the ground and carried aloft in balloons, aircraft, and satellites. Some measurements involve drawing air into an instrument that contains a system for detecting ozone. Other measurements are based on ozone’s unique absorption of light in the atmosphere. In that case, sunlight or laser light is carefully measured after passing through a portion of the atmosphere containing ozone. Q6: What are the principal steps in stratospheric ozone depletion caused by human activities? The initial step in the depletion of stratospheric ozone by human activities is the emission of ozone- depleting gases containing chlorine and bromine at Earth’s surface. Most of these gases accumulate in the lower atmosphere because they are unreactive and do not dissolve readily in rain or snow. Eventually, the emitted gases are transported to the stratosphere where they are converted to more reactive gases
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This note was uploaded on 09/29/2010 for the course ECON 100A taught by Professor Smith during the Spring '08 term at Alabama.

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Answers%20to%2020%20questions - Q1 What is ozone and where...

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