PhD Proposal: Jada Damond

Mercury (Hg) is a global pollutant that is microbially transformed into its more toxic and bioaccumulative form, methylmercury (MeHg) in anaerobic sediments. After its production, MeHg is introduced to aquatic organisms and subsequently biomagnified through the food web, putting fish consumers at risk for adverse health effects. Understanding the fate and transport of Hg and MeHg in aquatic sediments is required to determine the risk of a contaminated site and to design and evaluate site remedies. Difficulties with measuring aqueous MeHg, however, impede this understanding. Low MeHg concentrations, complex redox and biogeochemical interactions, temporal fluctuations, and spatial variability in sediment porewaters make traditional grab sampling methods difficult. To overcome these sampling difficulties, our group developed an equilibrium-based passive sampler (PS) comprising activated carbon (AC) suspended in agarose gel (ag+AC). In this sampling regime, the PS is deployed in an aqueous matrix until MeHg PS-water equilibrium is reached, after which the concentration in the aqueous phase is derived from the PS concentration using a PS partitioning coefficient. Thus far, the novel ag+AC sampler produced robust, detectable, time integrative aqueous MeHg measurements in laboratory sediment microcosms and in situ surface waters. Notably, the PS demonstrated the ability to measure a porewater depth profile at a fine resolution (0.5 cm) in a sediment microcosm (Figure 1), which is essential for locating where MeHg is produced in the sediments and evaluating its transport.

Field-scale additions of AC to sediments has shown great success in reducing the bioavailability of hydrophobic organic contaminants, which in many cases co-contaminate with Hg. However, its use for Hg remediation is still under development. Hg fate and transport – and consequently, the performance of remedial practice designed to reduce MeHg production and uptake to the aquatic food web – is heavily influenced by site biogeochemistry. Therefore, understanding these biogeochemical impacts is crucial for remedy design and evaluation. This research aims to improve ag+AC sampling efforts in the field, derive a spatially dependent fate and transport model, identify biogeochemical impacts on remedy performance, and test several remedial applications.

Agenda:

WEBEX Meeting for virtual attendance

https://umbc.webex.com/umbc/j.php?MTID=mfb0ef90911d111b6d0c5389bc71641bc 

Meeting number (access code): 2621 169 6213