HR: 0800h
AN: B11B-0413    [Abstracts]
TI: Adding to the Mercury Speciation Toolbox
AU: * Fitts, J P
EM: fitts@bnl.gov
AF: Brookhaven National Lab, PO 5000, Upton, NY 11973, United States
AU: Northrup, P A
EM: northrup@bnl.gov
AF: Brookhaven National Lab, PO 5000, Upton, NY 11973, United States
AU: Chidambaram, D
EM: devc@bnl.gov
AF: Brookhaven National Lab, PO 5000, Upton, NY 11973, United States
AU: Kalb, P D
EM: kalb@bnl.gov
AF: Brookhaven National Lab, PO 5000, Upton, NY 11973, United States
AB: Mercury was used to separate lithium-6 isotope for weapons production at the Y-12 Plant in Oak Ridge, TN in the 1950s and 1960s. A large portion of the waste Hg entered the environment and continues to move throughout the sub-surface and surface waters in the area. Environmental management of Hg contamination within this complex hydrologic system, where Hg speciation and the mobile fraction have been found to vary widely, will require ongoing characterization and predictive modeling of Hg speciation. State-of-the-art spectroscopic tools that can directly probe Hg speciation in preserved aqueous and sediment samples with greater sensitivity, however, are required to determine rates and mechanisms of biogeochemical reactions. We will present the first results demonstrating the use of x-ray absorption spectroscopy (XAS) at the Hg M5 edge (2295 eV) to fingerprint Hg species. Heavy-metal M5 absorption edges can have very sharp features due to local electron transitions, and therefore, we are developing this edge as a tool for quantitative measurement of Hg species. In addition, sulfur speciation using the sulfur K absorption edge, which is at a similar energy (2472 eV), can be measured in the same scan as the Hg M5 edge. Potentially important organic and inorganic sulfur species (sulfide, disulfide, elemental sulfur, sulfite and sulfate) are readily differentiated, and thereby, provides an independent method for monitoring the redox state of the system along with changes in S-Hg bonding. We will also present x-ray microprobe 2-D concentration maps of Hg and other elements at the grain and pore scales to identify its microscopic distribution and chemical associations. When used in combination with established sequential extraction and direct spectroscopic methods, the addition of XAS at the Hg M5 edge should provide a significant advancement in the determination of Hg speciation in complex biogeochemical environments.
DE: 0409 Bioavailability: chemical speciation and complexation
DE: 0452 Instruments and techniques
DE: 0461 Metals
DE: 0488 Sulfur cycling
SC: Biogeosciences [B]
MN: 2007 Fall Meeting