Experimentelle Bestimmung der Lösungskinetik synthetischen Calciumcarbonats und natürlicher Kalkgesteine

Abstract

Within the scope of this work dissolution rates of synthetic calcite and natural limestone (freshly and etched surface) were measured under different boundary conditions. Experiments were conducted with the objective to determine the influence of initial pCO2, temperature, dissolved foreign ions and material on the dissolution kinetics of calcium carbonate. A dataset emerged, which can be implemented into models of karst evolution accounting for different chemical boundary conditions. The batch experiment using the free drift method was chosen for measuring dissolution rates in closed system conditions with respect to CO2. The dissolution kinetics of the studied materials react differently to the presence of foreign ions in solution. Sulfate, phosphate and magnesium inhibit the dissolution rates of synthetic Baker Calcite. The resulting dissolution kinetics resembles that of natural limestone in pure H2O-CO2-solutions. In contrast to this sulfate has no influence on the dissolution rates of Jura Limestone, whereas magnesium and phosphate do inhibit the dissolution. The different dissolution kinetics can be attributed to the various lithologies. For the first time mixing corrosion in freshwater and freshwater-saltwater mixtures was reproduced in the laboratory. Under these boundary conditions the linear kinetics of Baker Calcite and nonlinear of natural limestone could be confirmed. Model calculations on the evolution of karst systems were conducted for two different chemical boundary conditions (pCO2i = 0.001 atm, 0.05 atm; 10°C) using the kinetic parameters of Jura Limestone in one- and two-dimensional models.