Graduate Student Speaker Series - Jada Damond

Fall 2021 CBEE Graduate Student Speaker Series

Speaker: Jada Damond, ENEN PhD

Novel Equilibrium-based Passive Sampling Device for the Measurement of Methylmercury (MeHg) in Water and Porewater of a Sediment Microcosm, and the Kinetic Evaluation of an Isotopically Labeled MeHg for Use as a Performance Reference Compound

Jada Damond^[1], Spencer Washburn^[2], Cynthia Gilmour^[2], Upal Ghosh^[1]

^[1]University of Maryland, Baltimore County

^[2]Smithsonian Environmental Research Center, Edgewater, MD 

Abstract:

Mercury is a global pollutant that can undergo methylation in natural systems to form the more toxic and bioaccumulative form, methylmercury (MeHg). MeHg will biomagnify within aquatic biota to levels unsafe for human consumption, making accurate determination of its concentration in aquatic environments crucial for adequate risk assessment and remediation. However, MeHg concentrations in waters and porewaters can be low (concentrations in unimpacted waters at the pM level) and highly variable through time, making accurate measurement with traditional field sampling methods challenging. Passive sampling can provide measurable and time-integrative aqueous MeHg concentrations, and has thus been explored in this work. Our novel equilibrium-based passive sampler comprised of activated carbon suspended in agarose gel (ag+AC) has provided robust and detectable MeHg concentrations in controlled, environmentally relevant settings. A single ag+AC polymer inserted across the sediment-water interface of a sediment microcosm predicted porewater and surface water concentrations within a factor of 4, forecasting the ability to provide spatially dependent aqueous concentration gradients critical for flux calculations. Additionally, we explored the use of isotopically labelled MeHg species as a performance reference compound (PRC), which is used to predict aqueous concentrations before equilibrium is reached. An ag+AC sampler preloaded with Me¹⁹⁹Hg was inserted into a solution containing Me¹⁹⁸Hg, after which sampler and solution concentrations were measured over a 14-day time course. A simple first-order kinetic model can describe the sampler uptake of Me¹⁹⁸Hg and desorption of Me¹⁹⁹Hg, with comparable rate constants between the two isotopic species, demonstrating the applicability of an isotopically labelled MeHg spike as a PRC. Future work will explore using PRCs in an environmentally relevant setting.

Join via WEBEX (see link above)

or Join by phone

+1-202-860-2110 United States Toll (Washington D.C.)

Access code: 262 296 85722