Multiscale Investigations on the Rates and Mechanisms of Targeted...

Full Title: Multiscale Investigations on the Rates and Mechanisms of Targeted Immobilization and Natural Attenuation of Metal,Radionuclide and Co-Contaminants in the SubsurfaceThis project is a DOE ERSD funded Integrated Field Challenge (IRC) locatedonthe Oak Ridge Reservation in eastern Tennessee. The project encompasses an integrated multi-disciplinary, multi-institutionalresearch program that provides an improved scientific understanding and predictive capability of subsurface contaminant fate andtransport at scales ranging from the molecular to the watershed. The Oak Ridge Field Research Facility (ORFRC) is being used by theIFC as the field laboratory for investigations of contaminant attenuation rates and mechanisms using a combination of geophysical,chemical, microbial, and hydrological analytical tools. The influence of coupled processes on contaminant migration are beingquantified along numerous distinct flow pathways and within transition zones throughout the watershed particularly processesassociated with natural attenuation of contaminant nitrate by denitrification and of U/Tc by natural immobilization onsoil/rock.These investigations are being integrated with on-going numerical studies to provide an accurate predictive capabilityfor long-term site performance and to determine if targeted manipulation is required. Pilot scale manipulations are therefore beingtested which include sustained in situ bioreduction for U/Tc immobilization, adjustment of soil-groundwater pH to precipitateU/Tc with aluminum hydroxides, and organophosphate and oleate amendments to enhance U/Tc adsorption/precipitation.Theinfluence of groundwater recharge on contaminant fate and transport is also being investigated at a variety of scales. Activeparticipation in the DOE ORR Closure Project Team will assure that technical insights are transferred into DOE remediation efforts.