SAMPLING AND ANALYSIS TECHNIQUES FOR DETERMINING CARBON ISOTOPE RATIOS IN ROBBER BARON CAVE

Initially the objective of this study was to gain a better of understanding of where the source of carbon dioxide originates from within Robber Baron Cave by studying the carbon dioxide isotope ratios, and how those ratios might change throughout the seasons of the year. Due to high concentrations of carbon dioxide in the cave atmosphere in the summer months, the Fischer ANalysen Instrumente GmbH (FAN) with a HeliFAN Plus sampler was used as our primary method in analyzing the air samples. However, when samples were gathered in late fall, the concentration of carbon dioxide in the cave atmosphere was much lower, and an error would occur in identifying the carbon 13 concentration for some of samples. Due to this problem, we turned to a mass spectrometer to identify the carbon 12 and carbon 13 values for the air samples with lower concentrations. Because some of our samples prior to the fall had only been run on the FAN, we ran several samples on both instruments to determine how the results would vary. The results led us to develop a protocol for future samples taken so that we would know what concentrations of carbon dioxide should be run on which instrument.