Abstract
AbstractUnexpected shifts of 13C concentrations observed with carbondioxide emerging from the water close to the eastern shore of Lake Laach could be explained by kinetic C isotopefractionation. This was caused by preferential 12C incorporation into HCO3‐ions as long as no saturation of CO2 was reached and time was not sufficient for establishing isotopic equilibrium. – Laboratory experiments with tank carbon‐dioxide bubbling through triple distilled water in columns up to 4 m high provided fractionations as large as 7.2‰. 13Carbon was found to be enriched in the passing carbondioxide. The effect decreased with time (i.e. with increasing saturation). – The fractionation becomes larger the higher the water column is. It depends also on the size of the carbondioxide bubbles and the water temperature. – These shifts of isotope ratios which occur frequently in nature invalidate fast conclusions regarding the origin of carbondioxide. Careful investigations of the degree of saturation and time available for equilibration are required before genetic conclusions from C isotope ratios are allowed.
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