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.
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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.