Cave monitoring of La Vallina Cave (NISA): Imprint of seasonality on δ13CDIC, δ18O and trace elements and the implications for speleothems

A cave monitoring sets the basis of speleothem studies. It helps to understand changing cave conditions on seasonal scale and site-specific geochemical differences such as hydrological conditions and heterogeneities in bedrock respectively. Here we present a set of parameters measured in La Vallina Cave (NW Iberian Speleothem Archive, NISA). Over the course of 16 months cave air conditions (pCO2 and δ13C) were examined to understand calcite precipitation, ventilation processes and mixing of soil air and atmospheric air. From stalactitic soda straws the δ13CDIC of dripwater was determined to learn about the carbon cycle in the overlaying soil and karst driven by seasonal vegetation and microbial degradation changes. We capture seasonal changes in δ13CDIC independent of degassing/PCP effects. Further, the δ18O and δD composition of dripwater and hydrology help to understand water reservoir and recharge processes related to precipitation. Finally, the elemental geochemistry of dripwater was investigated by analyzing 16 elements. We present data of commonly used elements such as Mg, Sr, Ca or Ba but also elements sparsely reported in cave dripwater monitoring studies such as Y, Na or As. Controlling factors are related to bedrock leaching, particulate import and potentially redox conditions.