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CONTEMPORARY ISSUES IN ENVIRONMENTAL SCIENCE EXAM II STUDY GUIDE- Fall 2008 45 questions covering lectures 9-17 and associated chapters (Ozone, Global Warming, Deforestation, Biodiversity)—and including the Food lecture that is not associated with any chapter and the Cuba Video 17 matching 6 short answers (mandatory answer) 2 short answer (choose from 5) 14 multiple choice 7 true/false (correct the false) Atmosphere/Ozone Know characteristics of each layer o Troposphere: Thickest at Tropics, Thinnest at Poles 80% of mass of atmosphere Most weather occurs here Environmental Lapse Rate: decrease in temperature in correlation to increase in height of trop. -6.5 C/1000 m Top of troposphere is reached at average -56.5 C o Stratosphere: Immediately above the troposphere 19.9% of atmosphere Gets warmer because of stratospheric ozone, it blocks UV rays from hitting the earth which increases the temperature o Mesosphere: Temperature at coldest in atmosphere -90 C Widest function in temperature o Thermosphere: Can be as great as 1200 C (absorption of solar energy by O2 molecules) Tropospheric and stratospheric ozone and the differences between them o Stratospheric Ozone: Contains 90% of Atmospheric Ozone Beneficial Role: Acts as primary UV radiation shield Current Issues: Long-term global downward trend Annual springtime Antarctica Ozone hole Annual springtime Arctic ozone loss in recent years In stratosphere, the ozone is formed by breaking of O2 molecules by the sun, and then recombining them to form ozone o Tropospheric Ozone: Contains 10% of atmospheric ozone Toxic effect on humans and vegetation Though there are small amounts of ozone in troposphere, it still has a high impact Current Issue Episode of high surface ozone in rural and urban areas PSCs and its role in ozone depletion
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o Polar Stratospheric Clouds Not actually clouds, not made of water vapor, its made of Nitric Acid They are clouds in the winter polar stratosphere at altitudes of 15,000- 25,000m They are implicated with the formation of ozone holes Solid and liquid PSCs form when temperatures drops below -78 C, nitric acid and sulfur-containing gases condense with water vapor. They support chemical reactions that produce active chlorine which catalyzes ozone destruction o Winter’s recipe for ozone loss: The polar winter leads to the formation of the polar vortex which isolates the air with it Cold temperatures form inside the vortex; cold enough for the formation of PSCs. As the vortex air is isolated, the cold temperatures and the PSCs persist Reactions take place converting inactive chlorine reservoirs to more active forms of chlorine Inactive chlorine reservoirs: o Chlorine nitrate (ClNo2) o Hydrogen Chloride (HCl) No ozone loss occurs until sunlight returns to the air inside the polar vortex and allows the production of active (or free) chlorine and initiates the
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