Meteo 532  --  Atmospheric Chemistry  --  Fall 2003

 

Final Examination

 

 

assigned:      01 December 2001

due:              noon, Wednesday, 17 December 2001

 

Please keep your answers brief.  As Strunk and White say: “Omit needless words.”  Please work alone on this exam.

 

1.  (20 points)  . It is said that globally the SO2 oxidation by gas-phase reactions and by aqueous-phase reactions are comparable. 

a) Estimate the fraction of the troposphere (below 6 km) that would need to be occupied by clouds for this to be true.  Assume that most of the oxidation occurs in the lowest part of the atmosphere, below 6 km, the average pH is 5.0, [OH]midday =3x106 cm-3, H2O2 = 1 ppbv,  and O3 is not important in SO2 oxidation. 

b) The SO2 flux into the atmosphere is about 80 Tg (S) yr-1 .  Estimate how many molecules of HOx are consumed in yearly SO2 oxidation.  Remember that the reaction HO2+HO2®HOOH+O2 is the only significant HOOH atmospheric source.

 

 

2. (20 points) Give the evidence that the Antarctic ozone hole results from chlorofluorocarbons.  Is quick remediation possible by either ozone replacement or chlorine removal?  Use numerical calculations of the amount of ozone that is lost or the required amount of a chemical necessary for chlorine removal to support your position.

 

 

For the following, provide explanations that are no more than 250 words long.  An equation counts as a word.  Pictures and figures may be used.  Each description is worth 15 points.

 

3.  Using an ozone isopleth diagram, explain why the EPA has been regulating only VOC emissions in an effort to reduce O3 in urban areas.

 

 

4.   Describe the lifecycle of an aerosol that is created by gas-to-particle conversion.

 

 

5.  Describe the behaviors that low-vapor-pressure products of reactive organic gases can have when interacting with preexisting aerosols.

 

6.  Explain the chemical reasons for the variation of stratospheric ozone destruction by halogen, HOx, and NOx catalytic cycles as a function of increasing NOx, as is presented schematically in the figure below.  Where would you put the Antarctic ozone hole on this figure?