k/t boundary, dust and CO2

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

due to a computer glitch, this message which preceded the other one
on dust got bounced back to me instead of going to the list:

as a geochemist i am fascinated by what the k/t boundary event would
have caused (assuming a meteorite impact for a minute).  impacting a
meteorite in carbonate rocks of the yucatan would drastically increase
the CO2 in the atmosphere.  if you look at the geochemistry involved,
this produces a major INCREASE in the solubility of calcite, which may
explain the crash of the nannoplankton discused by a recent poster 
(sorry i deleted the message without noting the name).  
similarly, the meteorite would itself volatolize significantly,
adding consider quantities of other gases, like SO2, H2S, CO2, etc.
particulates might include things like heavy metal oxides of Fe, Ni,
Cu, Zn, etc, but also significant quantities of As, Se, Hg, etc.,
not to mention the Ir we all know and love.  From the added silicates
and phosphates in the meteorite, if it were a chrondritic type, we
could expect significant increases in H4SiO4 and H3PO4, meaning that
silica would also likely increase significantly in solubility.  
what does this mean for organisms?  it means they must work MUCH 
harder to precipitate their shells if they have to signficantly
change the solubility of the mineral species rather than just change
it slightly as is the case in most situations today.  even for
the dinos life might have been very difficult.  if H3PO4 increases,
apatite solubility increases.  vertebrates already have a significant
problem precipitating hydroxyapatite because it is soluble in body
fluids.  if its solubility increases significantly in water, the
solubility problem in the body is more severe, meaning the animals
might have experienced very "spongy" bones or their young may not
have been able to form bone.  (this last is speculation on my
part that flowed as this post flowed.)

food for thought anyway...
bonn