Abstract:

Mercury (Hg) is a naturally occurring element with unique chemical and physical properties that led to its widespread use in a variety of applications over centuries. Unfortunately, inorganic Hg and its organomercurial compounds have severe negative health impacts and its continued use is heavily regulated or being phased out entirely. Hg has a complex environmental cycle that has been significantly altered by anthropogenic activity and it has become a pollutant of local, national, and global concern. Elemental Hg is the only metal that is liquid at room temperature, and it has a significant vapor pressure and long residence time in the atmosphere, facilitating long-range transport from source areas. Given that Hg mining and smelting date back over 3000 years, there are few places on the Earth’s surface that have not been affected by this altered cycle. The widespread presence of mercury is highlighted in ice core records and the findings that water bodies far from emission sources have fish consumption advisories driven by Hg concentrations.

Local to the Oak Ridge area, the Atomic Energy Commission used nearly 11 million kilograms of Hg during the 1950s and early 1960s at the Y-12 National Security Complex. About 3% of that Hg was lost to the local environment, including direct discharges to East Fork Poplar Creek (EFPC). Intense monitoring, characterization, and research on EFPC since the mid-1980s have prompted several remedial actions that have resulted in improvements to overall water quality. Nevertheless, Hg concentrations in fish tissue throughout the creek remain above the Environmental Protection Agency’s water quality criterion of 0.3 parts per million.  Over the past decade, basic and applied research programs at Oak Ridge National Laboratory (ORNL) have made significant contributions to improving our understanding of the fundamental mechanisms exerting control on Hg behavior in the environment and evaluating the efficacy of potential solutions for the remaining challenges in EFPC. The research has spanned broad spatial and temporal scales from Ångstroms and milliseconds to kilometers and decades and taken advantage of many of ORNL’s signature strengths (e.g., advanced computational hardware and software, neutron science, microbiology and genetic methods, environmental chemistry, and ecosystem studies). Selected highlights and achievements of these research efforts will be presented and discussed within the framework of our current conceptual model for the EFPC system.

ORNL mercury researchers gather samples of water from East Fork Poplar Creek.