CHARACTERIZING CO2 CONCENTRATION VARIATIONS IN TWO KARST SPRINGS AND TESTING CURRENT DISSOLUTION MODELS

The study of cave formation has relied on speleogenesis models that assume a constant rate of dissolution. However, a variable rate is expected in nature. The variability of CO₂ is a major factor in determining the saturation index (SI) of karst spring waters with respect to calcite. Here we study two karst springs, Copperhead Spring and Langle Spring, located at the Savoy Experimental Watershed in Savoy, AR. Monitoring at the sites is ongoing and includes high resolution pH, conductivity, water level, temperature, and dissolved CO₂ data. CO₂ is measured using CO₂ gas sensors encased in a waterproof breathable membrane. Discharge at the sites will be calculated based on stage/weir relationships. We will examine relationships between discharge, SI, and CO₂ in order to determine what factors control the saturation state of the water. To test karst dissolution models under the variable chemical conditions and flow conditions found in the field, limestone tablets were installed at each spring to observe actual dissolution. These tablets are weighed before and after exposure enabling estimation of dissolution rates. Over the same period the water quality parameters will be used to calculate a theoretical dissolution rate. Theoretical and observed rates will be compared against each other.