High-Resolution 27Al and 133Cs NMR of Weathered Hanford Sediments
EMSL Project ID
25447
Abstract
Hanford vadose zone sediments (Hanford coarse, Hanford fine, and Ringold silt) have been weathered by reaction with a simulated Hanford tank waste leachate and examined with a wide array of analytical tools, including 27Al, 29Si, and 133Cs MAS NMR. The amounts of parent and resulting neoformed materials present as a function of reaction time vary, as does the uptake of Cs and Sr radionuclide surrogates from the simulated tank waste leachate (STWL) solution. Understanding the uptake and subsequent fate of Cs and Sr in these systems is critical for a full analysis of environmental risk from leaking waste tanks at Hanford. Due to sediment complexity, the number of unique phases in the vadose zone sediment samples severely complicates our ability to resolve each parent and daughter phase; therefore, analysis at the highest possible field strength is warranted for the sediment studies to provide resolvability while maintaining quantitative accuracy. Preliminary 21.14 T data on vadose zone sediments is very promising and, by completing further acquisitions of NMR spectra, publishable data will be forthcoming that will inform further analysis of reactive transport in the vadose zone. In this proposed work, we intend to perform ultra high-field 27Al MAS and 27Al MQMAS NMR on the 21.14 T spectrometer to study Ringold silt, Hanford coarse, and Hanford fine sediments weathered under simulated tank waste conditions. We will also couple these studies with 133Cs MAS or MQMAS analyses to follow the fate of Cs in these systems. (A separate proposal deals with our on-going investigations of 87Sr NMR). In this work, we hope to (i) resolve and quantify each of the parent minerals and neoformed phases as a function of weathering time as well as (ii) use the NMR results to calculate the kinetics of dissolution and neophase precipitation for each of these samples, and (iii) merge these data with an understanding of Cs uptake and sequestration into newly formed solid phases. We will further couple this information with our environmental kinetics database efforts, a chemical cyberinfrastructure program funded through the National Science Foundation. In this effort we are developing collaboratory tools for scientific discovery in the area of environmental kinetics, and these new data will comprise one of our initial sets for population of the database in an automated or semi-automated manner through analysis tools being developed in our laboratory. Dr. Brett Didier (Computational Biology and Bioinformatics, PNNL) is a member of the scientific advisory board for this project, and is assisting our group with advice and the sharing of collaboratory tools developed through the Collaboratory for Multi-scale Chemical Science (http://www.cmcs.org/).
Project Details
Project type
Large-Scale EMSL Research
Start Date
2007-06-01
End Date
2009-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
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