A PRELIMINARY EVALUATION OF RARE EARTH ELEMENTS IN KARST SPRING WATER AND THEIR POTENTIAL AS INDICATORS OF WATER SOURCE

Although many municipalities and homeowners rely on karst springs for water, few effective techniques exist for evaluating the sustainability of water flow in a karst spring. We propose that springs with greater sustainability of flow have a greater component of deep flow that can be identified by its biogeochemical signature. For the chemical signature, our hypothesis is that springs with greater surface influence and shorter water residence time can be identified by anomalous concentrations within the rare earth elements (REE) series. Specifically, these springs should have large negative Ce and Eu anomalies, consistent with a more oxidizing setting. Two sets of samples were collected from three sets of springs. The first samples were collected during baseflow, the second two days after a 2.84-cm storm event. The storm influence on REE chemistry can be seen in JSF spring which had a dramatic increase in REE concentration and a change in the relative concentrations across the series after a storm event. The baseflow pattern at JSF was similar to other springs in the region. After the storm, the spring water was enriched in the middle and heavy REE in comparison with the light REE. At the nearby, more-stable NWM spring, there was little change in the REE geochemistry between the two sampling dates. KMR Spring, a water supply spring located further downstream and likely to have a significant flow component, had REE concentrations midway between those measured at JSF and NWM. Temperature variability was also examined for each of the springs on the assumption that greater variability ties to more surface influence and shorter water residence time. Based on our preliminary data, the temperature variability was not well correlated to either the Ce or Eu anomaly. However, the data from JSF spring suggests that REE may be a possible tool for identifying surface versus ground water contribution to spring water.