The NSS Bulletin - ISSN 1090-6924
Volume 49 Number 2: 31-49 - December 1987
A publication of the National Speleological Society

Kinetics of Calcite Dissolution and its Consequences to Karst Evolution from the Initial to the Mature State
Wolfgang Drybrodt

The dissolution rates of calcite in the system CaCO3-H2O-CO2 are determined by three processes: a) surface controlled dissolution at the solid-liquid interface, b) diffusion of the molecular and ionic species, and c) slow conversion of CO2 to H+ and HCO3-. We present a theory, which taking these processes into account, predicts dissolution rates of calcite for a) the case of a water layer flowing on a plane calcite surface with the other surface in contact to a CO2-containing atmosphere (open system), and b) for a water layer flowing between two parallel planar calcite surfaces (closed system). Both laminar and turbulent flow conditions have been considered. In the case of turbulent flow, the dissolution rates are higher by a factor of ten compared to laminar flow. The theoretically calculated dissolution rates have been asserted by experiments, the results of which are in close agreement to the theory. From the theoretical results penetration lengths are calculated for given cross sectional dimensions of water leading conduits. The distribution of flow and hydraulic gradients in simple karst systems is simulated by an electric analogue resistor network. Combining these two concepts, karst development can be explained in its scales of length and time.

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