INTRODUCTION:

1. μm Se As Fe Cr Mn Cr S GEOCHEMICAL SPECIATION OF SELENIUM AND OTHER HEAVY METALS IN COAL FLY ASH AFTER PROLONGED SUBMERSION IN THE EMORY RIVER AT THE KINGSTON FOSSIL PLANT SITE Jennifer M. Seiter, Mark A. Chappell, Anthony J. Bednar, Jacob K. Stanley, Alan J. Kennedy, Daniel E. Averett, Sara H. Hendrix, Jeffery A. Steevens U.S. Army Engineer Research and Development Center, Environmental Laboratory INTRODUCTION: On December 22, 2008, over 5 million cubic yards of fly ash were released to the Emory River, TN from the Tennessee Valley Authority (TVA) Kingston Fossil Plant. Remediation and recovery efforts for this event are currently underway. This study was conducted in order to determine concentration and metal species in the fly ash, and to predict potential for significant metals release from fly ash particles during remediation strategies.Objectives: To determine metal content and speciation in fly ash materials. Arsenic and selenium were the focus of these studies. Determining Elemental Distribution Using XRF RESULTS AND DISCUSSION: Iron and Manganese Speciation Using XANES Spectroscopy Fe Mn Mn(II) Mn(IV) Fe(II) Mn Fe(III) Fe • METHODS: • Field Collection: • All field samples collected on June 12, 2009 • Fly ash was collected from the source pile and from the Emory River at five discrete locations approximately 2.2 miles upstream of the confluence of the Emory and Clinch Rivers and composited • Fly ash and water also collected from the Ash Recovery Ditch (Sluice Channel) on site at the TVA Kingston Fossil Plant • Reference water for use in preparing elutriates was collected from the Emory River approximately 12 miles upstream of the Kingston Fossil Plant Figure 3. Solid state speciation of Fe and Mn in fly ash and elutriate samples • Iron speciation in the fly ash was not affected by submersion at the bottom of the Emory River. • Manganese was reduced to Mn(II) after ash submersion. Table 1. Total elemental composition of the fly ash Figure 2. XRF maps depicting elemental distribution of Se, As, Fe, Cr, Mn, and S of fly ash that has been submerged at the bottom of the Emory River • As, Se, Ba, and Cu are above the background levels in the reference sediment • Both liquid and solid state speciation data indicates that As(V) is the dominant form of arsenic in all fly ash sediments and elutriates • Elements follow similar trends most likely due to metal sorption to Mn and Fe oxides Fig. 1a Sequential Extractions Fig. 1b Arsenic and Selenium Speciation Using XANES Spectroscopy • CONCLUSION: • The results show that the fly ash exhibits geochemical stability, but it is undergoing kinetically slow transformations while submerged in the Emory River • Selenate was not a major Se species found in any of the ash samples • Organo-selenium was found in the sluice channel and the Emory River ash samples. • The major elements of concern are found in the less toxic forms: Se(IV) and As(V) • FUTURE STUDIES: • We just returned to the site to collect additional fly ash samples to look at Se and As speciation after long-term dredging. Studies will include: photo-oxidation and stability of Se, and As speciation of dredged materials. • ACKNOWLEDGMENT • Permission was granted by the Chief of Engineers to publish this material. We thank Jonathan Burr (TDEC) for assistance in field sampling. Figure 1a. Aerial image of the TVA site on 12/23/2008 Figure 1b. Sampling locations A www.tva.gov B • Metal Speciation Techniques: • Metal concentrations for all solid and aqueous samples were analyzed using ICP–AES or ICP–MS as appropriate for the concentration ranges observed for major and trace using a Perkin Elmer (Wellesley, MA) Optima 5300DV ICP-AES or Elan DRC-II ICP-MS, respectively. • Solid state metal speciation was conducted using X-ray absorption near edge structure (XANES) spectroscopy. This work was conducted at the Stanford Synchrotron Radiation Lightsource, National Synchrotron Light Source, and Center for Advanced Molecular Devices. • Linear Combination Fitting was done using Athena and 6pack data manipulation • programs. • Selenium is primarily in the Selenite (Se(IV)) form • Submersion of the fly ash affects Se speciation. Reduced Se species and/or organo-selenium are found in river and sluice channel samples Table 2. Elemental Concentrations after Sequential Extraction • The ash does not contain significant amounts of soluble As and Se. • A significant portion of the Se is in the Organic/Sulfide portion. • Most of the As and Se are in the more resilient forms.