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This project focused on aluminum precipitation within the Caustic Side Solvent Extraction (CSSX) process at the Savannah River Site (SRS). The CSSX process uses a solvent to separate cesium. In the scrubbing section, the solvent containing cesium is scrubbed with 0.05 M nitric acid to remove soluble sodium and potassium ions. During scrubbing, aluminum precipitation has been observed. Solids precipitation is of concern as solids might erode centrifugal contactor internals and/or plug transfer pipelines. Hence, it is important to identify conditions under which solids precipitation may occur and identify an operating region where solids precipitation is minimized. Room temperature experiments on the CSSX scrubbing process were conducted. Experimental results were compared with predictions from ESP (Environmental Simulation Program). The order and specific rate for the reversible aluminum precipitation reaction were obtained as a function of initial stream dilution and % carryover. The reaction was first order based on regression results.

The Pen Branch Fault is a reactivated, high angle, reverse basin border fault that dips to southeast from the basement (Triassic-Paleozoic-Precambrian in age) to near vertical through the Atlantic Coastal Plain sediments (Late Cretaceous to Recent in age) of the Savannah River site in South Carolina. The fault movement has occurred through Late Cretaceous to Tertiary. Faulting might penetrate as shallow as the Dry Branch and the Tobacco Road Sand Formations (Late Eocene). An investigation with high resolution reflection seismic data is undertaken along the Pen Branch Fault. Five of the seismic lines are reprocessed to help in determining the upward depth of penetration of this fault. This is done by utilizing refracted arrivals from the multifold reflection data. The shallowest refractors (4 - 18 m) imaged have an average velocity of 1700 m/s. All of the lines exhibit events that are not flat lying across the data where the fault is believed to be. The lines possess deformation such as offsets, upwarping and channels. Deformation can be related to the Pen Branch Fault as shallow as 4 m from the surface. Displacements along the lines vary from 1 m up to 5 m. Reverse sense of motion is mainly exhibited along the fault zone that is covered by this study. The events resolved portray the Pen Branch Fault in a fault zone of subparallel faults and splays. / Master of Science

Floodplains, and the sediment accumulating naturally on them, are important to maintain stream water quality and serve as sinks for organic and inorganic carbon. Newer theories contend that land use and hydrologic connectivity (water-mediated transport of matter, energy, and/or organisms within or between elements of the hydrologic cycle) play important roles in determining sediment accumulation on floodplains. This study hypothesizes that changes in hydrologic connectivity have a greater impact on floodplain sediment accumulation than changes in land use. Nine sediment cores from seven sub-basins were collected from the Savannah River Site (SRS), South Carolina, and processed for grain-size, radionuclide dating (7Be, 137Cs, 210Pb), particulate organic carbon (POC), and microscopy. Historical records, including aerial and satellite imagery, were used to identify anthropogenic disturbances in the sub-basins, as well as to calculate the percentages of natural vegetation land cover at the SRS in 1951, and 2014. LiDAR and field survey data identified 251 flow impediments, measured elevation, and recorded standard stream characteristics (e.g., bank height) that can affect hydrologic connectivity. Radionuclide dating was used to calculate sediment mass accumulation rates (MARs) and linear accumulation rates (LARs) for each core. Results indicate that sedimentation rates have increased across all SRS sub-basins over the past 40-50 years, shortly after site restoration and recovery efforts began. Findings show that hydrologic connectivity proxies (i.e., stream characteristics and impediments) have stronger relationships to MARs and LARs than the land use proxy (i.e., vegetation cover), confirming the hypothesis. As stream channel depth and the number of impediments increase, floodplain sedimentation rates also increase. This knowledge can help future stream restoration efforts by focusing resources to more efficiently attain stated goals, particularly in terms of floodplain sediment retention.

129I is of major concern because of its biophilic nature, excessive inventory, long half-life (~16 million yrs), and high mobility in the natural environment that depends on its chemical speciation. Iodide (I-) has the highest mobility than iodate (IO3-) and is the predominant species in the terrestrial environment due to prevailing pH and Eh conditions. In order to transform I- to less mobile organo-iodine (OI), strong oxidants are necessary to activate the first electron transfer step from I- to reactive intermediates. The aim of this study was to determine the influence of naturally occurring aerobic bacteria isolated from an 129I contaminated aquifer (F-area of the Savannah River Site, SC) on I- oxidation and OI formation. It was demonstrated that 3 of 136 strains accumulated I- (0.2~2%) in the presence of H2O2, when incubated in the presence of an environmentally relevant concentration of I- (0.1 microM). The accumulation was likely through electrophilic substitution resulting in the iodination of cellular constituents. The results indicated that culturable I--accumulating bacteria are not directly responsible for the high fraction of oxidized iodine species (IO3- and OI, >50% of total I) present in the SRS F-area. Several bacterial strains were found to be capable of stimulating I- oxidation through excretion of oxidants and enzymes. Organic acids in spent liquid medium from 27 of 84 aerobic bacterial cultures enhanced H2O2-dependent I- oxidation 2-10 fold. Organic acids enhanced I- oxidation by (1) lowering the pH of the spent medium and (2) reacting with H2O2 to form peroxy carboxylic acids, which are strong oxidizing agents. In the absence of H2O2, spent medium from 44 of 84 bacteria cultures showed I- oxidizing capacities. One I- oxidizing bacterium was studied to characterize its extracellular I- oxidizing component(s). The I- oxidizing capability from the spent medium was inactive by treatments with heat and H2O2 and absent under anaerobic conditions. Conversely, NADH, NADPH and FMN additions stimulated I- oxidation in the spend medium. These results indicate an oxidase(s) catalyzed I- oxidation. Understanding the bacterial activities involved with I- oxidation and OI formation is expected to help reduce 129I mobility in water-soil systems.