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Apr5

Calculus Olympiad 2025

Apr 5, 2025, 9:00 AM - 3:00 PM

George Mason University, Fairfax Virginia campus

Merten Hall

Apr8

STEM (& Pre-Med/Pre-Health) Virtual Transfer Info Sessions

Apr 8, 2025, 5:00 - 6:00 PM

online, link provided at registration.

Apr9

9 Apr (CLIM) Zeng, Burying Woody Biomass

Apr 9, 2025, 1:30 - 2:30 PM

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PhD Dissertation Defense - Environmental Science & Policy

Apr 10, 2025, 10:30 AM - 12:30 PM

HYBRID 
In person at Potomac Science Center 3102 and
Virtual on Zoom (contact espgrad@gmu.edu for Zoom meeting info)

PhD Dissertation
Department of Environmental Science and Policy
College of Science
George Mason University

 

Candidate: Doreen Sechak Peters
Defense Date and Time: April 10, 2025, 10:30am
Defense Location: Potomac Science Center 3102 and virtual on Zoom
Title: Of tides and skins: Using dragonfly exuviae as a non-lethal approach to monitor mercury along the nontidal and tidal freshwater Potomac River from Monocacy to Mount Vernon

 

Thesis Director: Dr. Dann Sklarew 
Committee: Dr. Greg Foster, Dr. Amy Fowler, Dr. Richard Groover

 

ABSTRACT

 

Dragonfly nymphs live from months to years in rivers where they may be exposed to mercury through prey ingestion, respiration, and physical contact with contaminated water and sediment. Analyses of exuviae (shed skins of nymphs) collected from nontidal and tidal freshwater reaches of the Potomac River showed that abundance, species richness, and diversity of dragonflies were consistently higher at nontidal sites, but evenness was higher at tidal freshwater sites. Mercury concentrations detected in exuviae positively correlated with concentrations in sediment and porewater. Exuviae offer a novel, non-lethal means to identify resident species and monitor mercury concentrations along the Potomac River.

 

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