CO2 DYNAMICS IN A CARBONATE CRITICAL ZONE SYSTEM, SAVOY EXPERIMENTAL WATERSHED, ARKANSAS, USA

CO₂ dynamics within the Earth’s critical zone drive spatial and temporal variations of carbonate dissolution and precipitation and are fundamental to understanding subsurface porosity and permeability development. We explore these dynamics within a mantled karst terrain at the Savoy Experimental Watershed (SEW) in Northwest Arkansas. Prior monitoring of dissolved CO₂ concentrations and dissolution rates at a pair of underflow (perennial) and overflow (high flow) springs at the SEW have helped shed light on the temporal variations in CO₂ within a carbonate critical zone system. However, we still know little about patterns of CO₂ transport and production within the carbonate critical zone. We hypothesize that both CO₂ production and advective transport of fluids through the vadose zone influence spatial patterns of CO₂ in karst landscapes. To better constrain spatial variation in CO₂ and production and transport processes, we have instrumented six additional sites that span a range of subsurface depths, which include a “deep” groundwater well (~10 meters), “intermediate” vadose zone (~3 meters), and “shallow” soil zone wells (< 1 meters). These data will be compared with synoptic to seasonal hydrometeorological changes to examine how these parameters impact CO₂ concentrations. In addition, simultaneous CO₂ and O₂ measurements help us further explore how coupled biotic (e.g., soil respiration) and abiotic (e.g., calcite dissolution and precipitation) processes control CO₂ dynamics—understanding the spatial and temporal dynamics of CO₂ in the carbonate critical zone will further our understanding of karst’s role in the global carbon cycle.