One important issue in atmospheric chemistry is to exactly understand and quantify the OH based oxidative power of the troposphere. Not oxygen, or even ozone are directly responsible for the photochemcial breakdown of 10 billion tons of reduced gases that are emitted into the troposphere by natural processes, and increasingly through man's activities. It is the OH radical that attacks most types of reduced gases, and even reduces the lifetime of the greenhouse gas methane to less than 10 years.
The distribution of OH is calculated using complex atmospheric chemistry/transport models and verified using chemical tracers of which we know the production, and that react with OH. 14CO is such a tracer par excellence, and therefore we have attempted to reconstruct past 14CO levels using large air samples extracted form ice.
Our worst fears have become true as deeper in the firn we not only detect atmospheric 14CO, but another hard to quantify contribution from in situ production from the spallation of oxygen. We show results for 3 Antarctic sites, and discuss this ugly fact of nature destroying our beautiful hypothesis that we could use air from firn or even ice cores to reconstruct one of the most important parameters of the past atmosphere.
By using the oxygen-18 isotopic exchange rate between firn air CO2, and firn air water we may understand the process of the interaction between firn air and the matrix somewhat. The question remains if we ever can correct for this in situ component.
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See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)