Role of Microenvironments and Transition Zones in Subsurface Reactive Contaminant Transport
EMSL Project ID
34494
Abstract
The PNNL Scientific Focus Area (SFA) will resolve critical Hanford and basic subsurface science issues through integrated, multi-disciplinary, science-theme focused research on the role of microenvironments and transition zones in the reactive transport of technetium (Tc), uranium (U), and plutonium (Pu). Microenvironments are small domains within larger ones that exert a disproportionate influence on subsurface contaminant migration. They may be internal fractures or microbiologic niches within porous media lithic fragments; grain coatings, bio-films, or micro-colonies on larger mineral particles; or compact silt/clay stringers in gravel-dominated subsurface sediments. Transition zones are field scale features where chemical, physical, or microbiologic properties change dramatically over relatively short distances (e.g., 1 m). They exhibit steep, transport-controlled gradients of system controlling chemical species such as O2, H+, or organic carbon. Microenvironments and transition zones frequently dominate subsurface contaminant reactivity, with strong effects resulting from the coupling of chemical reaction, physical transport (advection, diffusion), and microbiologic processes. Past EMSP and NABIR research has documented the importance of these zones at the Hanford site.The overall ten-year goals of the SFA are to develop: i.) an integrated conceptual model for microbial ecology in the Hanford subsurface and its influence on contaminant migration, ii.) a fundamental understanding of chemical reaction, biotransformation, and physical transport processes in microenvironments and transition zones, and iii.) quantitative biogeochemical reactive transport models for Tc, U, and Pu that integrate multi-process coupling at different spatial scales for field-scale application. Targeted contaminant chemical reaction and biotransformation processes include heterogeneous/biologic electron transfer, precipitation and dissolution, and surface complexation. The SFA will emphasize lab-based, coupled computational and experimental research using relevant physical/biologic models, and sediments and microbial isolates from various Hanford settings to explore
molecular, microscopic, and macroscopic processes underlying field-scale contaminant migration. It will also pursue the refinement of geophysical techniques to define, characterize, and map spatial structures and reactive transport properties of microenvironments and transition zones in the field. The SFA will partner with the PNNL Environmental Molecular Sciences Laboratory (EMSL) to develop molecular understandings of key processes, and the Hanford Integrated Field Challenge (IFC) for access to, and samples from subsurface environments where these zones exist and are important.
Project Details
Project type
Exploratory Research
Start Date
2009-08-31
End Date
2010-09-05
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Extracellular Reduction of Hexavalent Chromium by Cytochromes MtrC and OmcA of Shewanella oneidensis MR-1
Belchik SM, DW Kennedy, A Dohnalkova, Y Wang, PC Sevinc, HJ Wu, Y Lin, HP Lu, JK Fredrickson, and L Shi. 2011. "Extracellular Reduction of Hexavalent Chromium by Cytochromes MtrC and OmcA of Shewanella oneidensis MR-1." Applied and Environmental Microbiology 77(12):4035–4041. doi:10.1128/AEM.02463-10
Separation, characterization and initial reaction studies of magnetite particles from Hanford sediments
Baer DR, AE Grosz, ES Ilton, KM Krupka, J Liu, RL Penn, and A Pepin. 2010. "Separation, Characterization and Initial Reaction Studies of Magnetite Particles from Hanford Sediments." Physics and Chemistry of the Earth 35(6-8):233-241. doi:10.1016/j.pce.2010.04.010