Name: Loni Matthew
Date: 07/21/2026
Time (EST/EDT): 1:00 pm
Location: AREL Lecture Hall
Remote Access: mees@umd.edu

Committee Chair: Dr. Elizabeth North
Committee Members: Dr. Heath Kelsey Dr. Christine Knauss Dr. Eric Schott

Title: Modelling Microplastic Transport from Wastewater Treatment Plants in
the Chesapeake Bay

Abstract: Microplastics are widespread in aquatic environments, with
wastewater treatment plants (WWTPs) being a significant contributor to their
environmental output. Estuaries, such as the Chesapeake Bay, have been observed
to retain microplastics, yet the factors that influence the prediction of
microplastics transport from WWTPs in Chesapeake Bay have not been assessed.
Our objective used the three-dimensional hydrodynamic model ChesROMS and the
particle tracking model LTRANS to determine what factors are critical for
simulation of microplastic particles from WWTPs in Chesapeake Bay. Simulations
were conducted with particles that originated from three regional WWTPs that
release effluent into Chesapeake tributaries (Potomac River, Patapsco River,
Choptank River). Simulated microplastic particles were characterized by size
(125 μm), shape (fiber and fragment), and polymer type with different densities
(polyethylene and polystyrene) that correspond with microplastic particles that
are commonly observed in WWTP effluent. Model simulations were run to determine
the sensitivity of model predictions to shape, density, subgrid-scale
turbulence parameterizations, environmental conditions, stickiness with land
boundaries (aka “beaching”) and biofilm formation. Particles with realistic
microplastic shape and polymer density had spatial and depth distributions that
were markedly different from those of passive particles, indicating that using
passive particles is insufficient to understand microplastic transport in
estuaries. Sub-grid scale turbulence caused particles to be realistically
distributed more broadly both horizontally and vertically than without
turbulence, while biofilmed particles were retained closer to their origin WWTP
than those without biofilm growth. Beaching also was a parameterization that
had a strong influence on predicted transport. This project is one of few
microplastic modelling simulation studies in the Chesapeake Bay and builds upon
previous information about microplastic transport by focusing on microplastics
from WWTPs in the region and by identifying which model parameterizations are
important for understanding microplastic transport in estuaries.