Abstract
Historical use of liquid elemental mercury (Hg(0)l) at the Y-12 National Security Complex in Oak Ridge, TN, USA, resulted in large deposits of Hg(0)l in the soils. The fate and distribution of the spilled Hg(0) are not well characterized. In this study we evaluated analytical tools for characterizing the speciation of Hg in the contaminated soils and then used the analytical techniques to examine the speciation of Hg in two soil cores collected at the site. These include x-ray fluorescence (XRF), soil Hg(0) headspace analysis, and total Hg determination by acid digestion coupled with cold vapor atomic absorption (HgT). XRF was not found to be suitable for evaluating Hg concentrations in heterogeneous soils containing low concentration of Hg or Hg(0) because Hg concentrations determined using this method were lower than those determined by HgT analysis and the XRF detection limit is 20 mg/kg. Hg(0)g headspace analysis coupled with HgT measurements yielded good results for examining the presence of Hg(0)l in soils and the speciation of Hg. The two soil cores are highly heterogeneous in both the depth and extent of Hg contamination, with Hg concentrations ranging from 0.05 to 8400mg/kg. In the first core, Hg(0)l was distributed throughout the 3.2m depth, whereas the second core, from a location 12m away, contained Hg(0)l in a 0.3m zone only. Sequential extractions showed organically associated Hg dominant at depths with low Hg concentration. Soil from the zone of groundwater saturation showed reducing conditions and the Hg is likely present as Hg-sulfide species. At this depth, lateral Hg transport in the groundwater may be a source of Hg detected in the soil at the deeper soil depths. Overall, characterization of soils containing Hg(0)l is difficult because of the heterogeneous distribution of Hg within the soils. This is exacerbated in industrial facilities where fill materials make up much of the soils and historical and continued reworking of the subsurface has remobilized the Hg.
| Original language | English |
|---|---|
| Pages (from-to) | 20-29 |
| Number of pages | 10 |
| Journal | Environmental Research |
| Volume | 125 |
| DOIs | |
| State | Published - Aug 2013 |
Funding
Funding for this project was provided by the US Department of Energy, Office of Environmental Management, Technology Innovation and Development Office, as part of the Remediation of Mercury and Industrial Contaminants Applied Field Research Initiative. This work was conducted at ORNL, operated by UT-Battelle, LLC, for the US Department of Energy under contract DE-AC05-00OR22725. We would like to thank Steve Field and Terry Cothron for assistance in coordinating field samples at the Y-12 facility and David King for providing split soil samples and facilitating the transfer of samples collected at the 81-10 locations at Y-12 to ORNL.
Keywords
- Analytical methods
- Elemental mercury
- Industrial contamination
- Soil
