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. Recent technological advances have enabled high-resolution timeseries measurements of dissolved CO₂ using a CO₂ gas sensor coated in a waterproof breathable membrane. In order to better understand the dynamics of CO₂ in karst systems, we will employ this new technology to study the temporal variations of dissolved and gaseous CO₂ concentrations in Blowing Springs Cave in Bella Vista, Arkansas. Airflow within the cave is driven by the chimney effect, such that outside seasonal temperature changes influence cave airflow velocity and direction. The main cave entrance, which is the only known human-sized entrance to the cave, acts as a lower entrance. During the winter months, outside air is pulled into the cave entrance, and much of the cave reaches typical CO₂ concentrations of outside air. During the summer months, cool air from the cave flows out the entrance, and CO₂ levels in the cave rise. In this study, we will collect time-series measurements of the CO₂ concentrations of air and water in Blowing Springs Cave. Airflow velocity and water discharge will also be measured, so that CO₂ fluxes within both the air and water can be quantified. Additionally, air temperature and relative humidity will be measured both inside and outside of the cave. Ultimately, the observations will be used to examine the diurnal and seasonal changes in gaseous and dissolved CO₂ and explore the extent to which the air and water systems interact.