RESEARCH
TRANSPORT, FATE, AND IMPACTS, OF CONTAMINANTS OF EMERGING CONCERN
I am broadly interested in studying contaminants of emerging concern and their effects on the environment. My recent work has focused specifically on two contaminants, microplastics and herbicides, in stormwater ponds across the Grand Strand, South Carolina. I am currently working with Dr. Stefanie Whitmire at Clemson University.
Research projects
EVALUATING THE IMPACTS OF HERBICIDES IN RESIDENTIAL STORMWATER PONDS
Coastal South Carolina has experienced rapid population growth and is projected to exceed 1.5 million people by 2030. As a result, there has been a boom in the development of new residential developments across popular coastal areas, such as in the Grand Strand (Horry and Georgetown counties). In residential developments, stormwater ponds are common best management practices (BMPs) used to protect water quality by trapping stormwater runoff from delivering environmental contaminants, such as herbicides, to local waterways. This work aims to evaluate the impacts of glyphosate, a commonly applied herbicide ingredient, on plankton dynamics in residential stormwater ponds within the Grand Strand. Ponds from new (<5 years old) residential developments will be compared to ponds from old (>20 years old) residential developments in summer 2024 and winter 2025. The concentration of glyphosate and one of its degradation products, aminomethylphosphonic acid (AMPA), along with other water quality parameters, will be measured in each pond at the beginning of the study to determine baseline concentrations and overall pond health. A passive diffusion periphytometer, housing bottles containing a gradient of glyphosate concentrations, will be deployed in each pond to measure the periphyton community response through chlorophyll-a concentration. By assessing the impacts of this herbicide ingredient on plankton dynamics, the study will evaluate water quality and pond functionality, which will inform future stormwater pond planning and management practices.
INVESTIGATING MICROPLASTIC DIST. , ABUNDANCE, AND COMP. , IN THE SURFACE WATERS OF TWO SC INLETS
This work was done by Alyssa Wentzel, a NOAA Hollings Scholar from the University of Delaware that I mentored during the summer of 2024.
Estuaries are the intersection of upland, rivers, and the sea that house a variety of unique habitats. With increasing coastal development, estuaries in the Grand Strand, South Carolina, are at risk for accumulating plastic debris, which can eventually break down into microplastics (<5mm). Murrells Inlet, SC, is characterized as an urbanized area with limited plastic policies, high rates of tourism, and high plastic consumption, making it susceptible to the influx of microplastics. In comparison, a nearby inlet, North Inlet, has little urbanization impact and limited access. We studied these two inlets to examine the impacts that urbanization has on microplastic distribution. We collected water samples at 5 different sites at each inlet (n=10) during an ebbing tide in June 2024 to analyze microplastic distributions, abundance, and composition to assess the fate and transport of microplastic pollution across these two inlets. Microplastics were analyzed and characterized on an Agilent LDIR 8700, which detected microplastics from 20-500 μm . The mean microplastics abundance across all locations in Murrells Inlet was 230.8 ± 64.77 MP/m3 while North Inlet average was 195± 78.21 MP/m3. We found that there was no statistical difference between the two inlets (p = 0.227), but patterns did emerge in distribution of abundance and particle composition across the estuaries. The most abundant particle composition was rubber, however, there was no statistical difference of rubber in these two inlets (p=0.079). Tire wear particles were most abundant in areas by boat ramps and were seen in smaller amounts in the other locations. Despite emerging similarities of microplastic abundance between these two inlets, Murrells Inlet experienced higher amounts of polytetrafluoroethylene (PTFE) (p=0.015) and polyethylene terephthalate (PET) (p= 0.054). Knowing there was limited differentiation between abundance of microplastics of pristine and urbanized inlets, these results point to a need for local mitigation and prevention efforts in order to reduce the load of microplastics into estuarine environments.
EVALUATING NONPOINT SOURCE MICROPLASTIC POLLUTION AND ITS IMPACT ON BIOTA IN THE HURON RIVER
Contaminants of emerging concern (CECs), like microplastics and pharmaceuticals, are a
growing threat to aquatic ecosystems across the globe. Microplastics can be transported into
waterways through a myriad of sources, including point sources such as wastewater treatment
plants (WWTPs) and nonpoint sources, such as runoff. Microplastics can act as vectors for other
CECs, such as non-steroidal anti-inflammatory drugs (NSAIDs), into biota. The goal of this
study was to evaluate 1) the importance of non-point sources of microplastic pollution to the
Huron River, 2) if aquatic filter feeders ingest microplastics, and 3) how the interaction of
microplastics and pharmaceuticals affect filter feeders. To address my first goal, I measured the
microplastic load of the Huron River at Waterworks Park in Ypsilanti, MI, between September
and November 2021 and May and August 2022 over a range of river discharge. There was a
strong positive relationship between river discharge and microplastic load, suggesting that runoff
is an important source of microplastic pollution to the river. To address my second and third
goals, I conducted manipulative experiments exposing zebra mussels (Dreissena polymorpha) in
microcosms to microplastics and pharmaceuticals in a factorial design. On average, mussels
ingested 57.5 ± 35.2 MP/individual during the 24-day experiment. Results from this experiment
indicate that exposure to microplastics, ibuprofen, and diclofenac for 24 days reduced mussel
feeding rate in some treatments after 19-20 days but had no detectable effects on mussel growth
and metabolism.