Multi-scale Characterization and Prediction of Coupled Subsurface Biogeochemical-Hydrological Processes Page: 1 of 5
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Multi-scale Characterization and Prediction of Coupled Subsurface
PI: Susan Hubbard*l
Co-PIs & Collaborators: Ken Williams*l, Carl Steefel*1, Jill Banfield*2
Phil Long*3, Lee Slater*4, Steve Pride*l and Jinsong Chen*l
*1 LBNL; *2 UCB; *3 PNNL: *4 Rutgers Univ.
1. Research Objectives. To advance solutions needed for remediation of DOE contaminated
sites, approaches are needed that can elucidate and predict reactions associated with coupled
biological, geochemical, and hydrological processes over a variety of spatial scales and in
heterogeneous environments. Our previous laboratory experimental experiments, which were
conducted under controlled and homogeneous conditions, suggest that geophysical methods have
the potential for elucidating system transformations that often occur during remediation.
Examples include tracking the onset and aggregation of precipitates associated with sulfate
reduction using seismic and complex resistivity methods (Williams et al., 2005; Ntarlagiannis et
al., 2005) as well as estimating the volume of evolved gas associated with denitrification using
radar velocity. These exciting studies illustrated that geophysical responses correlated with
biogeochemical changes, but also that multiple factors could impact the geophysical signature
and thus a better understanding as well as integration tools were needed to advance the
techniques to the point where they can be used to provide quantitative estimates of system
Our current research includes theoretical, numerical, and experimental investigations,
performed at the laboratory and the field scales, to determine if geophysical methods can be used
to uniquely monitor system transformations. Our work is geared toward the Rifle, CO, site,
where other investigations are exploring the efficacy of electron-donor amendments for
facilitating sustainable microbial reduction of U(VI) to U(IV) through a series of local-scale field
experiments. Since the interplay between iron and sulfate reduction is believed to be of critical
importance to the sustainable reduction of U(VI) at this site, quantitative interpretation of
geophysical data in terms of redox state, exhaustion of bioavailable iron mineral phases, or onset
of sulfate reduction is expected to greatly benefit the understanding and sustained remediation of
uranium at the site.
2. Research Progress and Implications. Our project includes five key components:
laboratory and field-scale experiments; development of petrophysical relationships; development
of an estimation framework for integrating disparate, time-lapse datasets; and iteration between
the geophysical monitoring estimates with predictions from advanced reactive transport models.
This report summarizes the progress in our first year of a three year project in each of these
2a) Laboratory studies. We have utilized site-derived materials to test a number of controlled
mineralogical transformations at the laboratory scale during this year under static flow
conditions. These transformations include (1) clay mineral alteration accompanying the
reduction of structural ferric iron, (2) oxidation of FeS precipitates accompanying an increase in
groundwater oxygen concentration, and (3) reduction of structural iron in bulk sediments through
exposure to sulfide-rich groundwater. The goal of each of the three tests was to monitor the
temporal change in the complex resistivity signal accompanying the transformation and to
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Hubbard, Susan; Williams, Ken; Steefel, Carl; Banfield, Jill; Long, Phil; Slater, Lee et al. Multi-scale Characterization and Prediction of Coupled Subsurface Biogeochemical-Hydrological Processes, report, June 1, 2006; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc883197/m1/1/: accessed January 18, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.