10/05/2022
By Erica Gavin

The University of Massachusetts Lowell, Kennedy College of Sciences, Graduate Program of Marine Science and Technology and Department of Environmental, Earth and Atmospheric Sciences, invites you to attend a doctoral dissertation defense by Ting Wang on “Mercury Cycling in the Salt Marsh of the Parker River Wildlife Estuary in Massachusetts, US.”

Candidate Name: Ting Wang
Defense Date: Tuesday, Oct. 18, 2022
Time: 1:30 to 4:30 p.m.
Location: 212 Olney Science Center, North Campus
Thesis/Dissertation Title: Mercury Cycling in the Salt Marsh of the Parker River Wildlife Estuary in Massachusetts, US

Advisor: Daniel Obrist, Professor, Department of Environmental, Earth and Atmospheric Sciences, University of Massachusetts Lowell

Committee Members:

  • David Ryan, Professor, Department of Chemistry, University of Massachusetts Lowell
  • James Heiss, Assistant Professor, Department of Environmental, Earth and Atmospheric Sciences & Department of Climate Change Initiative, University of Massachusetts Lowell
  • Celia Y. Chen, Research Professor, Department of Biological Sciences, Dartmouth College

Brief Abstract:
The goals of my dissertation research were to quantify sources, sinks, and dynamics of mercury (Hg) in the Plum Island Sound estuary salt marsh in Massachusetts, a hot spot of biological Hg exposure, through comprehensive quantification of major Hg inputs and outputs. A particular emphasis of the study addresses the importance of lateral tidal exchanges of Hg between salt marsh soils and the estuary, and the role of plants in controlling Hg dynamics in this densely vegetated ecosystem. I hypothesize that salt marsh vegetation provides a main source of Hg inputs driven by plant uptake of atmospheric gaseous elemental Hg (GEM), similar to observations in terrestrial ecosystems.

In this dissertation, four subchapters are addressing these goals with the following major results. (I) The salt marsh ecosystem currently serves as a lateral Hg source to intertidal water and the nearby coastal ocean, via export of dissolved and particulate Hg along with Hg export by floating plant debris (wrack). (II) Atmospheric GEM uptake by plants only constitutes about 30% of total plant Hg and hence provides relatively little external atmospheric deposition, with most plant Hg representing an internal salt marsh cycling of Hg between soils and plants. (III) Direct measurements of surface-atmosphere GEM exchange fluxes by means of a large micrometeorological tower are in support of small role of atmospheric GEM deposition and plant GEM uptake in this marsh ecosystem. Finally, (IV) salt marsh soils contain very large Hg pool sizes and soil depth profiles show substantial Hg enhancements during the peak industrial periods in the mid-1900s, suggesting large impacts by regional industrial pollution sources. I complete my thesis with estimated mass balance and mass accumulation rates of Hg combining all major sources and sinks measured in this study.