Reactivity of primary soil minerals and secondary precipitates beneath leaking Hanford waste tanks
EMSL Project ID
2543
Abstract
Objectives The primary goals of this project are to (1) quantify reaction kinetics for the dominant mineral dissolution and precipitation reactions that will occur when tank fluids mix with the Hanford soil and soil solutions, (2) obtain a mechanistic understanding of nucleation mechanisms and nucleation sites of secondary Al-bearing solids that should comprise the most abundant surface area for contaminant sorption reactions, and (3) integrate the kinetic data obtained from the proposed experimental studies with reactive/transport modeling to identify and refine our quantitative understanding of the key parameters that control contaminant mobility and migration pathways. See the attached file for further proposal Approach and necessary equipments Preliminary batch dissolution experiments of quartz and biotite has been done and doing now in the University of Colorado leaded by Kathryn L. Nagy. In PNNL, we are now conducting the column experiments to understand the dissolution or secondary precipitates in three different solids (e.g., quartz, quartz (85%) + biotite (15%), and Hanford sediments (Warden silt loam)) under flow conditions. The effluent will be analyzed as a function of time and the data will be used to predict the dissolution or combined dissolution and precipitation reaction rates. Column experiments with different conditions such as residence time, flow rate, and input solution are now in the progress. After experiments, the columns will be dissected and the sediments will be analyzed. R.Jeff Serne at PNNL is responsible for carrying out saturated and unsaturated flow column experiments. S.B. Yabusaki of PNNL guides the experimental work through application of reactive/transport models to the experimental mineral/solution systems. Since mineral dissolution and secondary precipitation are very sensitive to the mineral surfaces, X-ray Photoelectron Spectroscopy (XPS), a surface sensitive technique, will be the best to determine the changes at the mineral surfaces. Using XPS, different chemical composition or changes at the mineral surfaces resulted from dissolution or secondary precipitates by caustic tank waste solution will be revealed. In addition to XPS, analytical equipment such as ICP-MS or ICP-OES will be used to analyze the chemical composition of the effluents in the column experiments. Even though we can use the ICP-MS and -OES in our group (Applied Geology and Geochemistry), there are lots of samples still waiting so that we cannot guarantee the exact time to use that machine. If we can use one of those analytical equipments in EMSL, it will be great helpful to save the time. For use of ICP-MS, Wietsma, Thomas W. will be a preferred contacting staff in EMSL.
Project Details
Project type
Exploratory Research
Start Date
2002-06-20
End Date
2005-06-26
Status
Closed
Released Data Link
Team
Principal Investigator