The Philip M. Smith Graduate Research Grant for Cave and Karst Research

2020 Grants

Teresa Baraza ($3,000)
Ph.D. Student
Department of Earth and Atmospheric Sciences
Saint Louis University

Using Stable Isotopes and Trace Elements to Identify Microplastic Sources and Transport Mechanisms in a Karstic Cave System

Abstract: Microplastic (plastics < 5 mm) contamination is ubiquitous, and has been found in environments ranging from deep ocean floors to Artic Sea ice. Because plastics degrade slowly and are highly mobile, microplastics are one of the most concerning emerging contaminants of our time. Microplastics are dangerous to ecosystems not only because they can be ingested and cause internal issues to wildlife, but also because they can act as carriers of other contaminants such as heavy metals and organic compounds. Microplastic research has historically been focused in marine environments, and more recent studies have investigated microplastic contamination in surface freshwaters. However, currently, only one study has quantified microplastic contamination in groundwater. We propose a study that will investigate microplastic sourcing and transport in a cave system. To do so, we will collect water samples weekly under different flow conditions and more frequently during flooding events. Microplastics will be characterized by their type, size, color, and polymer type. We will perform hydrograph separations during floods, using stable water isotopes (δ18O and δ2H), to describe microplastic transport mechanisms through the cave system. Furthermore, we will use trace elements (e.g., B, Zn, As, Pb) to identify potential microplastic sources (e.g., wastewater, surface runoff). This study will provide new insight into how microplastic contamination moves through groundwater systems, which will help inform debris mitigation strategies.


Cameron de Wet ($3,000)
Ph.D. Student
Department of Earth and Environmental Sciences
Vanderbilt University

Assessing the Influence of Epikarst Hydrology and Geology on Dripwater and Speleothem Calcium Isotope Signatures

Abstract: Geochemical proxy records from speleothems provide crucial information for understanding past environments. Variations in speleothem carbon (δ13C) and oxygen isotopes (δ18O), and trace element ratios have been used to infer relative changes in paleo-rainfall across the globe. However, the complex controls on these proxy systems often preclude quantitative assessments of paleo-rainfall changes. New techniques for modeling calcium isotope cycling during prior calcite precipitation (PCP) along the seepage water flow path above a cave are yielding the first quantitative estimates of paleo-rainfall from speleothem records. However, there are open questions as to how karst geology, flow path geometry, and seasonality of rainfall affect calcium isotope cycling, as well as how best to relate PCP to specific rainfall amounts. This study stands to answer these questions by comparing modern cave system δ44/40Ca data between karst environments in California and Tennessee with differing geology, seepage water flow path geometry, and precipitation seasonality. By combining cave monitoring data with local rainfall records, I will determine the most important controls on dripwater and speleothem δ44/40Ca and use this data to constrain seepage water flow rates and their response to rainfall events. I will also collect data for other proxies that are influenced by PCP and water-rock interactions (δ13C, Mg/Ca, Sr/Ca) to cross-reference with the new δ44/40Ca datasets. Ultimately, this work will provide robust guidelines for implementing δ44/40Ca as a quantitative paleo-rainfall proxy in caves with variable background climate, host rock type, and hydrologic characteristics.


Rachel Kaiser ($3,000)
Ph.D. Student
Department of Environmental Sciences
Tennessee Technical University

An Interdisciplinary Approach to Understanding the Presence of Antibiotic Resistance and Antibiotic Resistant Bacteria in Urban Karst Groundwater Systems

Abstract: The presence of antibiotics and antibiotic resistant bacteria (ARB) in source waters, such as groundwater, is a growing global concern. Bacteria resistant to life-saving antibiotics can have detrimental impacts to environmental and human health. These emerging pathogens have recently been established as a major concern due to human health impacts and dilution of the effectiveness of available antibiotics; however, there is little to no research work done on the presence and impacts of ARB in urban karst groundwater systems. Every continent in the world has karst landscape features, with nearly a quarter of the human population living on or near karst regions and using karst groundwater aquifers as drinking water sources, which may be potentially contaminated with ARB. Therefore, the purpose of this research is to determine the presence, type of resistance, and level of resistivity of ARB in karst groundwater systems. Moreover, how the unique nature of these karst systems, their water quality, and adjoining land-use impacts the presence and level of resistivity in ARB is not well studied. Addressing these data gaps will aid in informing regulations to protect water resources and human health.

Page last updated or validated on April 14, 2020