QUANTIFYING CARBON DIOXIDE FLUXES IN THE AIR AND WATER OF BLOWING SPRINGS CAVE, ARKANSAS

Prior work has shown that the concentration of carbon dioxide (CO₂) within cave atmospheres is a strong function of cave airflow patterns. The dynamics of CO₂ within karst systems are of increasing interest as they can control periods of precipitation or dissolution in speleothems and influence potential interpretations of paleoclimate records. Similarly, CO₂ is an important driver of speleogenesis, and air-water CO₂ dynamics can control patterns of cave passage evolution. Karst also plays an uncertain role in the global carbon cycle, and understanding CO₂ dynamics within karst systems will aid the development of carbon budgets. Here, we have deployed a monitoring station to study the temporal variations of dissolved and gaseous CO₂ concentrations in Blowing Springs Cave in Bella Vista, Arkansas. Results show fluctuations in CO₂ concentrations are controlled by density driven chimney effect airflow. The chimney effect is driven by outside temperature changes, which influence the relative density of cave air and outside air. During the winter months, air is pulled into the lower, main entrance resulting in low CO₂ concentrations within the cave. During the summer months, cool air from the cave flows out the entrance and CO₂ levels in the cave rise. The CO₂ concentration in the air is immediately affected by the reversals in airflow. However, in the water we see delayed response to changes in airflow direction. Airflow velocity and discharge are also being measured, so that CO₂ fluxes within both the air and water can be quantified. Longitudinal profiles of gaseous and dissolved CO₂ within the cave were constructed from spot measurements of CO₂ during different seasons and airflow regimes. Ultimately, the observations are used to quantify CO₂ fluxes, to examine the diurnal and seasonal changes in gaseous and dissolved CO₂ and to quantify interactions between the air and water systems interact.