The goals of the SFA through FY 2016 are to
- Establish understanding of
- Molecular biogeochemical transformation mechanisms of target contaminants and Fe-mineral phases
- Multi-scale coupling of physical microbiologic, and geochemical processes
- Phenomenon and properties controlling cross-scale process modulation
- The microbial ecology and biogeochemical function of the groundwater-river interaction zone.
- New concepts for up scaling from the grain/pore-scale to the field, emphasizing parameters and variables descriptive of reactive transport and microbial community attributes
- Improved pore-scale biogeochemical models that incorporate metabolic constraints and realistic physicochemical interactions with the microscopic environment
- Integrative coupled process models for the groundwater-river interaction zone.
The SFA science portfolio, investigators and collaborators, and funding are organized into three thematic areas:
- Molecular and microscopic electron transfer processes
- Pore-scale reactive transport and up-scaling
- Field-scale microbial ecology and biogeochemistry.
Each theme area has a multi-disciplinary research team that works closely to resolve a cohesive set of impactful scientific questions. This approach enhances collaborative research and scientific impact in target areas.
Theme Area 1: Molecular and microscopic electron transfer processes
We are performing research in the lab to understand and model abiotic and biotic heterogeneous electron transfer reactions at the fundamental level that modify contaminant valence, and the reactivity of Fe-containing mineral phases.
- Experimental studies of the structure, reactivity, and properties of electron transfer proteins and other biochemical reactants isolated from relevant microorganisms
- Experimental studies of the redox chemistry of Tc, Pu, and U on Fe mineral surfaces in model and sediment systems
- Molecular modeling of chemical and physical interactions to reveal mechanisms. Unique model experimental systems have been developed to unravel the details of important biotic and abiotic heterogeneous reaction systems.
Theme Area 2: Pore-scale reactive transport and up-scaling
Lab research and modeling is investigating coupled process interactions at the intragrain, grain, pore, and Darcy scale; and how the interactions and models describing them scale to the field. Physical and chemical systems representative of Hanford microenvironments and transition zones are studied in unique, micro-fluidic and other model systems.
Processes considered include electron transfer, surface complexation, precipitation and dissolution, microbe-mineral and microbe-contaminant interactions, and diffusion/advection.
The scope includes advanced structural and chemical imaging at different scales, and experimental and theoretical studies of reactive transport parameter up-scaling for U and Tc from the pore to field scale, using a reactive facies approach at the larger scale.
Theme Area 3: Field scale microbial ecology and biogeochemistry
We are investigating the microbial ecology, community structure, biogeochemical function, and contaminant transport behavior of the unconfined aquifer containing the 300 Area U plume near the Columbia River using a variety of laboratory microbiological techniques (e.g., cultivation, genomics, molecular phylogeny, proteomics); laboratory microcosms; and in situ monitoring and experimental systems.
Core samples from the vadose and saturated zones, groundwater samples, and IFRC groundwater monitoring wells provide system access. The field site contains dramatic vertical redox transition zones and a dynamic groundwater river mixing zone with transitory spatial location, temperature, and water composition.
The development of a field-scale, coupled process model that adequately describes and predicts key system behaviors and properties is a long-term goal.