Evaluation of the Effects of Microbes on Autunite Dissolution and the Spectral Induced Polarization Response in Hanford Vadose Zone Sediment - 18440

Conference · Sun Jul 01 00:00:00 EDT 2018

OSTI ID:22977735

Garcia, Alejandro; Katsenovich, Yelena ^[1]; Lee, Brady ^[2]

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1. Applied Research Center, Florida International University, 10555 W Flagler Str., Miami, FL 33174 (United States)
2. Pacific Northwest National Laboratory, PO Box 999, K3-62, Richland, WA 99352 (United States)

As a result of the U.S. nuclear weapons program during the second World War and throughout the Cold War, there now exists a significant amount of uranium contamination at the U.S. Department of Energy Hanford site located in Washington State. Much of this contamination is in the form of mobile uranyl carbonates species within the vadose zone, which at Hanford varies up to 100 m thick in the Central Plateau. In-situ immobilization of mobile uranium via injections of a soluble sodium tripolyphosphate amendment may prove effective in the formation of low-solubility uranyl phosphate solid phases, autunite. However, the injected polyphosphate undergoes hydrolysis in aqueous solutions to form orthophosphate, which serves as a readily available nutrient for the various microorganisms in the sediment. Sediment-filled column experiments conducted under saturated oxygen restricted conditions using a geophysical technique known as spectral induced polarization (SIP) have shown the impact of microbes on the dissolution of synthetic autunite. Two sets of experiments were conducted using test columns. Each experiment had a pair of columns inoculated with microbes (with a glucose solution acting as a nutrient source) which were monitored using SIP in conjunction with regular sampling of pore-water. Columns were built with two silver/silver chloride (Ag/AgCl) coiled current electrodes at either end and four Ag potential electrodes along the side, which allowed the measurement of three distinct points along the length of the column. SIP measures phase which is the time delay between an injected current and measured voltage, in this case measured in radians. Three sampling ports were added to correspond with the geophysical measurements. Pore-water samples taken over the course of the experiment were analyzed for dissolved elements including uranium, iron, phosphorous, calcium, and magnesium. SIP results were plotted over time in order to determine correlations between changes in electrical phase and changes in pore-water chemistry. It was determined that changes in the phase and bulk resistivity detected with SIP corresponded to changes in the pore-water chemistry due to the growth of microbes. The first experiment ran for five months and had measurements done once a week, the second only ran one month but had measurements taken five times a week in order to understand initial changes in column chemistry in greater detail. SIP may be an effective way to remotely track changes indicative of bacterial activities on the surrounding environment. This method has the potential for field application at a larger scale for the purpose of tracking microbe growth in response to tripolyphosphate amendment. (authors)

• Research Organization: WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
• OSTI ID: 22977735
• Report Number(s): INIS-US-20-WM-18440; TRN: US21V0363017780
• Resource Relation: Conference: WM2018: 44. Annual Waste Management Conference, Phoenix, AZ (United States), 18-22 Mar 2018; Other Information: Country of input: France; 12 refs.; Available online at: https://www.xcdsystem.com/wmsym/2018/index.html
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
AQUEOUS SOLUTIONS
AUTUNITE
GAS SATURATION
GLUCOSE
HANFORD RESERVATION
HYDROLYSIS
MICROORGANISMS
OXYGEN
POLARIZATION
SAMPLING
SEDIMENTS
SILVER
SILVER CHLORIDES
SOLIDIFICATION
SURFACE CONTAMINATION
URANYL CARBONATES
URANYL PHOSPHATES
WATER CHEMISTRY