3.) OZONE a) shows global ozone change compared to the 1964-1980 average. b) sho

Question

3.) OZONE a) shows global ozone change compared to the 1964-1980 average. b) shows total column ozone at the South Pole in 2010 and 2011 compared to the 1986-2009 average. a) Changes b) TOTAL OZONE 2010 - 2011 -~nual wages Range of obserwars 1970 1980 1990 2000 2010 Year a) What role did chlorofluorocarbons (Freons) play in determining the shape of the graph on the left (a)? Specifically, why did Total Global Ozone start decreasing around 1980? Why did it level off in the early 1990s? (4 points) b.) Why did the total column ozone drop significantly in September and October of 2010 and 2011? Explain the processes that destroy ozone during Antarctic spring. (4 points) 30 25 20 15 15 20 10 OZONE PARTIAL PRESSURE ImPa

Explanation / Answer

3.

a) Chlorofluorocarbons are being added to the environment in steadily increasing amounts. These compounds are chemically inert and may remain in the atmosphere for 40-150 years, and concentrations can be expected to reach 10 to 30 times present levels. And these CFCs destroy the ozone layer so the graph shapes like that.

Depletion of the global ozone layer began gradually in the 1980s and reached a maximum of about 5% in the early 1990s.Global total ozone has decreased beginning in the 1980s . The decreases have occurred in the stratospheric ozone layer where most ozone resides. In the early 1990s, the depletion of global total ozone reached a maximum of about 5% below the 1964–1980 average.The observed global ozone depletion in the last three decades is attributable to increases in reactive halogen gases in the stratosphere. The lowest global total ozone values since 1980 have occurred in the years following the eruption of Mt.Pinatubo in 1991, which temporarily increased the number of sulfuric acid-containing particles throughout the stratosphere. These particles significantly increased the effectiveness of reactive halogen gases in destroying ozone and, thereby, increased global ozone depletion by 1–2% for several years following the eruption.

b)Antarctic ozone depletion is associated with enhanced chlorine from anthropogenic chlorofluorocarbons and heterogeneous chemistry under cold conditions. This accounts for the phenomenon of Antarctic spring.

The ozone hole is formed each year in the Southern Hemisphere spring (September-November) when there is a sharp decline (currently up to 60%) in the total ozone over most of Antarctica. During the cold dark Antarctic winter, stratospheric ice clouds (PSCs, polar stratospheric clouds) form when temperatures drop below -78C. These clouds are responsible for chemical changes that promote production of chemically active chlorine and bromine. When sunlight returns to the Antarctic in the Southern Hemisphere spring, this chlorine and bromine activation leads to rapid ozone loss, which then results in the Antarctic ozone hole.

c)Stratospheric ozone is formed naturally by chemical reactions involving solar ultraviolet radiation (sunlight) and oxygen molecules, which make up 21% of the atmosphere. In the first step, solar ultraviolet radiation breaks apart one oxygen molecule to produce two oxygen atoms. In the second step,each of these highly reactive atoms combines with an oxygen molecule to produce an ozone molecule. These reactions occur continually whenever solar ultraviolet radiation is present in the stratosphere. As a result, the largest ozone production occurs in the tropical stratosphere.

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