Seasonal δ¹³C_DIC sourcing and geochemical flux in telogenetic epikarst of south‐central Kentucky

Abstract

Telogenetic epikarst carbon sourcing and transport processes and their associated hydrogeochemical responses are complex and dynamic. Carbon dioxide (CO2) transport rates in the epikarst zone are often driven by hydrogeochemical responses, which influence carbonate dissolution and conduit formation. This study examines the influence of land use on carbon sourcing and carbonate dissolution kinetics through a comparative analysis of separate, but similar, epikarst systems in south‐central Kentucky. The use of high‐resolution hydrogeochemical data from multiple data loggers and isotope analysis from collected water samples reflects the processes within these epikarst aquifers, which are estimated to contribute significantly to bedrock dissolution. Results indicate that, in an agricultural setting, long‐term variability and dissolution is governed by seasonal production of CO2. In a more urbanized, shallower epikarst system, land cover may affect CO2 transport between the soil and underlying bedrock. This concentration of CO2 potentially contributes to ongoing dissolution and conduit development, irrespective of seasonality. The observed responses in telogenetic epikarst systems seem to be more similar to eogenetic settings, which is suggested to be driven by CO2 transport occurring independent of high matrix porosity. The results of this study indicate site‐specific responses with respect to both geochemical and δ13CDIC changes on a seasonal scale, despite regional geologic similarities. The results indicate that further comparative analyses between rural and urban landscapes in other karst settings is needed to delineate the impact of land use and seasonality on dissolution and carbon sourcing during karst formation processes. © 2019 John Wiley & Sons, Ltd.

Extreme Learning Machine Predicts High-Frequency Stream flow and Nitrate-N Concentrations in a Karst Agricultural Watershed

“…Findings from our study site are reflective of dynamics commonly observed for contaminants in karst and agricultural watersheds, excluding findings from heavily fertilized agricultural landscapes (Liu et al, 2007;Baran et al, 2008;Buda and DeWalle, 2009;Blaen et al, 2017;Husic et al, 2019;Yue et al, 2019;Jackson and Polk, 2020). Storm event hysteresis patterns reflect hydrologic connectivity pathways that have been commonly described.…”

“…Storm event hysteresis patterns reflect hydrologic connectivity pathways that have been commonly described. Lui et al ( 2007) and Jackson and Polk (2020) showed similar seasonal trends and storm event dilution and recharge characteristics in karst study sites when analyzing specific conductance and dissolved inorganic carbon. Likewise, numerous studies have highlighted increased nitrate-N concentration and loading during the wet season, which has been attributed to enhanced hydrologic connectivity of nitrate rich pore waters in the soil to the watershed outlet (Basu et al, 2010;Yang et al, 2017;Husic et al, 2019;Yue et al, 2019).…”