ATMOSPHERIC CARBON MONOXIDE 143 



DISCUSSION BY ATTENDEES 



Stevens: We have been working on the carbon and oxygen isotopic 

 composition of carbon monoxide in unpolluted atmospheres and find the 

 predominant species has a light oxygen isotopic composition that is quite 

 different from the isotopic composition of engine-produced carbon monoxide. 

 The estimated production rate is 10 to 30 times greater than annual engine 

 emissions, and this estimate agrees with Weinstock's value. We also find a burst 

 of carbon monoxide in the autumn which may be from the degradation of 

 chlorophyll at the end of the growing season. 



Muckerman: A factor that complicates Reaction No. 4 (OH + CO -> 

 C0 2 + H) is the possibility that the intermediate formic acid radical (COOH) is 

 stable. This radical has been isolated in a solid matrix and characterized by IR 

 spectroscopy by A. Milligan. Molecular orbital calculations by M. Newton at 

 Brookhaven National Laboratory predict that COOH is more stable than 

 C0 2 + H. It seems to me that, at pressures of about an atmosphere, the COOH 



intermediate in reaction 4 could be stabilized and then undergo a chemistry 

 of its own. None of the various experimental studies of the kinetics of Reaction 

 No. 4 has reported this COOH product, but those experiments which have 

 analyzed products have been carried out at pressures where one would not 

 expect the necessary collisional stabilization. 



Cadle: It has been the history of gas phase rate constants that, as more 

 sophisticated work is done, rate constants tend to be lowered. The reason often 

 is that the early studies have overlooked such things as hetergeneous reactions on 

 the walls. 



