a few more words on dust

["Bonnie Blackwell, Dept of Geology, (718) 997-3332"@lepomis.psych.upenn.edu (718) (718)]

by the way, the dust likely stayed airborn for a long time (not the
months suggested by a recent poster).  dust from volcanic eruptions
of el chicon and mt st helens have shown to be remain airborn for 5-10
years.  with something the size of the meteorite impact, the dust
likely stayed up much longer.  as for the gases in the atmosphere,
i would like to know how long they might take to return to normal
levels.  i dont believe we really have any idea of how long the 
CCD takes to respond to increased CO2 levels, or how long it might
take to reequilibrate the S, P, and Si species to "normal" levels.
but given residence times for the atmosphere and oceans for some
species, it might take a long time.  the fact that the boundary
clay seems to exist almost everywhere there is a recognized boundary
suggests a major geochemical catastrophe.  the question is how much
(how acidic) and for how long.  without knowing one of the two the
other is hard to estimate.
b