Problem Set 2 Questions concerning Rowland’s Nobel Lecture in Chemistry (Due at beginning of class on assigned date):



1.      Describe and explain the significance of the scientific discovery that started Rowland’s work in this area.


2.      Identify the postdoctoral student who elected to work on this problem; describe their experience with atmospheric chemistry.


3.      Outline and explain the basis for the three well-established general tropospheric sinks that exist for most molecules released at ground level. Explain the effectiveness of these in removing CFCs.


Stratospheric Chemical Processes


4.      CFC’s released at the top of the earth’s atmosphere would decompose quickly in several weeks; clearly explain why this would not also happen for CFCs released at ground level.


5.      Ozone and diatomic oxygen are present in the atmosphere in what concentrations?


6.      Fully describe and explain the basis for the source of heat that creates the stratosphere.


7.      What ranges of wavelengths does the CCl3F molecule absorb; what part of the atmosphere must the molecule be located in for this to occur?


8.      How long do CFC molecules survive in the atmosphere?  Explain why that is the case.


9.      Identify the lifetime estimates for CCl3F and for CCl2F2.


Chlorine Chemistry in Stratosphere


10.  Compare the relative probability for the reaction of free chlorine atoms with ozone and with methane.


11.  What are the ultimate sinks for CCl3F and Cl respectively.  What happens to ClO?


12.  What two factors cause the depletion of stratospheric ozone by CFCs to become a global environmental problem?


13.  What three forms are identified as the temporary chlorine reservoirs?  What two forms must chlorine be in for ozone depletion to occur?


Growth of Tropospheric CFC Concentrations


14.  How, i.e. where, are CFC concentrations measured in order to obtain a reliable estimate of global tropospheric concentration of a CFC.


15.  Compare and identify the measured tropospheric CCl3F concentrations for 1971, 1979, and 1987. What evidence do these concentrations suggest for the atmospheric lifetime of this substance.


Springtime Loss of Ozone in the Antarctic


16.  Outline the events involving the discovery of this.


17.  Compare the average October ozone values over the Halley Bay during the mid 1980s with levels observed during the 1960s.


Chemistry of the Polar Stratosphere


18.  What three possible reasons for the ozone loss were identified; which of these mechanisms were found to be responsible?


19.  Explain what is meant by denitrification and outline why this is important.


Ozone Losses in the Northern Temperate Zone


20.  What do these data show?


21.  What impact on political agreements did the northern temperature zone ozone readings have?


22.  Describe the political agreements reached.


23.  Compare observed decreases in ozone with increases in UV-B radiation at ground level.


Changing O3 and CFC Concentrations in the 1990s


24.  Summarize ozone concentrations observed during the early 1990s.


25.  Summarize CFC tropospheric concentration changes observed during the early 1990s.


26.  What is the overall situation concerning this problem as of the end of 1995?