MadSci Network: Environment & Ecology

Re: Do high flying aircraft increase/decrease damage caused by aerosols

Date: Wed Oct 13 11:35:06 1999
Posted By: In Koo Kim, Grad student, Atmospheric Physical Chemistry, University of Colorado @ Boulder
Area of science: Environment & Ecology
ID: 938466482.En

  There is currently much debate about the effects of high flying aircraft.  
On the one hand, these aircraft introduce NOx into the stratosphere (NO and 
NO2).  While NOx themselves are involved in catalytic ozone depletion, they 
also combine with Cl and ClO to form Chlorine Nitrate, a reservoir of 
stratospherinc inorganic chlorine.  So whether or not NOx introduction would 
increase or decrease overall ozone depletion depends on temperature, the 
rates of the individual reactions, and the relative abundance of the NOx and 
chlorine species.
  I think, perhaps, you might misunderstand what an atmospheric aerosol is.  
An aerosol is pretty much any particle in the gas phase.  This might include 
things as big as hail or meteors or things as small as cloud particles or 
molecules.  The reason aerosol sprays are bad is because they often containt 
CFC's.  These chlorine containing compounds dissociate in the stratosphere 
and release chlorine there.  This chlorine does not turn into chlorine 
nitrate until it reacts with NO2.  But before it does turn to NO2, bot the 
NO2 and Chlorine compound (ClO) are involved in catalytic ozone destruction.  
And even after ClONO2 forms, it can photolyze back to their constituents.
  So the answer to your questions is, it depends.  The other concern of high 
flying aircrafts is their release of particulates (aerosols) like soot and 
other combustion products.  Heterogeneous reactions (reactions on more than 
one phase liquid-gas, gas-solid...) can then take place.  One of the 
important heterogeneous reaction is the one between Chlorine Nitrate and 
HCl.  Both are reservoirs for inorganic chlorine.  But, they can react with 
each other on surfaces and return chlorine to their active ozone destructive 
  Hope this helps.

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