Fog!                                               12/8

     1.  What was the pollutant that killed the 4000 people in England that led to their clean air act?
             The knowledge of particular irritants in pollution at that time (1952) was not adequate for identification of those
                irritants causing the most problems.  Certainly those irritants were emitted in the burning of coal, much of which
                was high in sulfur, leading to the suspicion that sulfur oxides were the main problem.

    2.  Are there documented excess deaths attributable to air pollution in the US like those in 1952 in the UK?
             Yes.  During a similar 5-day pollution episode in Pennsylvania's Monongahela River Valley in 1948 more than 20
                persons died and thousands became ill.

    3.  Isn't CO₂ one of the major gases that depletes the ozone layer?
             No.

     4.  Is it true that global warming is having a greater effect in increasing nighttime minimum temperatures than
         in increasing daytime maximum temperatures?
                That is true, especially in the most polluted areas.

    5.  Does CO "sink" or "float" in the atmosphere?  If I crawl on the ground in a CO-filled room will I be safer?
                The CO molecule is a bit less massive than the N₂ and O₂ molecules which are most abundant in the atmosphere. 
                Therefore it has a very slight tendency to "float."  However that tendency is almost certainly too feeble to make a
                significant difference if you were to crawl.  In fact the difference in the weights of the heavier O₂ molecule and the
                lighter N₂ molecule is twice as great as the difference in the heavier N₂ molecule and the lighter CO molecule. 
                The motions of these molecules keep them well mixed so they have little tendency to separate by weight.

    6.  Given the large number of atmospheric [pollutant] chemical reaction possibilities, is there a way to predict
         the reactions which will occur?  Are they random?
                If sufficient information is available, i.e., temperature, concentration of all gases present in the atmosphere, sunlight
                intensity, atmospheric pressure and reaction rates for each of the possible reactions involving the gases present, it is
                possible to predict the reactions which will occur and the final concentrations of all the interacting gases.  Often,
                however, some of the needed information is not known so there is some uncertainty in the outcome, especially in
                reactions involving some of the more exotic gases such as VOCs.  There is randomness in the sense that the fates of
                individual molecules cannot be predicted, but one can calculate the probabilities of various outcomes for a
                particular molecule.  It is much like predicting outcomes for groups of people, e.g., it can be predicted, with fair
                accuracy, the number of traffic accidents which will occur in Utah in a particular time period, but it is not possible to
                predict the specific individuals who will be involved in those accidents.

    7.  What specifically causes CFC pollution?  Do CFCs always migrate to the stratosphere where they can
         destroy the ozone layer?
                The principal sources of CFCs are propellents in spray cans, some insulating materials, refrigerants such as freon,
                and some solvents and cleaning solutions.  All do not migrate to the stratosphere, but a substantial fraction do.

     8.  Have you enjoyed teaching our class?
                Yes.  I always enjoy teaching Physics 137, but this semester's class has been one I have particularly enjoyed.  Thank
                you for being such a delightful class.