> 	Here are a couple of quick technical questions.  When the you ask
> for the 4 most abundant gases in the atmo, are you looking for (in order
> from most abundant) N2, O2, Argon, Neon; or are you looking for N2,
> O2, CO2, H2O?

If you were to take several samples of air and count the # of different
types of molecules in each sample you would find that the # of H2O
molecules varied from sample to sample, but would still be the fourth most
abundant on average.  The book lists a range of 0-4% and in general the
fraction of H2O is about 1%.  This is considerably more than the 0.04% for
CO2 and the 0.002 for Ne listed in table 1.1.  One might argue that the
amount of H2O is sometimes larger than that of Ar in the samples, but the
top 4 would be N2,O2,Ar,H2O (not in order of abundance).


> 	Also, the definition of aerosol is impurities (solid, liquid, or
> gas), natural or man-made, in the atmosphere.  So, does this include
> pollutants?  Or is that a separate category?

Actually, aerosols are only liquid or solid (not gas).  Yes they can be
either man-made or natural in origin.  Pollutants can be any phase and be
anything in the atmosphere that occurs in concentrations significantly
above ambient levels AND are the result of human activity.  So, I'd say
that some aerosols can be pollutants, but not all pollutants are
aerosols.