Date of Thesis

Spring 2018

Thesis Type

Honors Thesis (Bucknell Access Only)

Degree Type

Bachelor of Science

Major

Geology & Environmental Geosciences

First Advisor

Ellen K. Herman

Keywords

Karst, Carbon Dioxide, Measurement

Abstract

Previously, many studies have used calculated carbon dioxide concentration to analyze geochemical changes in karst systems. Observing variations in carbon dioxide concentrations in karst systems can be useful in many fields, including further understanding karst as a source or sink of global [CO2], which is currently not well understood. This project utilizes non-dispersive infrared (NDIR) sensors to directly measure carbon dioxide concentrations, [CO2], at two karst springs in order to eliminate calculated [CO2] errors that arise from pH electrodes, temperature changes and degassing in storm samples. The purpose of this thesis was to assess the success of these new sensors based on comparison of data from a Vaisala GMP 221, a Vaisala GMP 251, a Csense by Turner Designs, and calculated values. The success was determined by the precision of the devices, as well as their ability to detect changes in [CO2] during storm events.

Overall, the trends in directly measured values matched well with calculated values, although the measurement of [CO2] showed higher resolution, particularly for capturing the rising limb of storms. In general, calculated [CO2] values appear to be higher than those of measured [CO2]. Measuring [CO2] directly was particularly helpful in comparing arrival times of distinct waters during different storms at the same site, which showed that there was clearly variability in flow paths and recharge processes on a storm to storm basis. Measurement was also helpful in observing differences in storm response between the two springs. Although the depth changes in response to storm events are similar at both springs, the [CO2] fluctuations on the same scale follow very different patterns.

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