Plasmid size determines adsorption to clay and breakthrough in a saturated sand column.

Horizontal gene transfer (HGT) is a major factor in the spread of antibiotic resistant genes (ARG). Transformation, one mode of HGT, involves the acquisition and expression of extracellular DNA (eDNA). eDNA in soils is degraded rapidly by extracellular nucleases.

Bioremediation of copper in sediments from a constructed wetland ex situ with the novel bacterium Cupriavidus basilensis SRS.

The H-02 constructed wetland was designed to remove metals (primarily copper and zinc) to treat building process water and storm water runoff from multiple sources associated with the Tritium Facility at the DOE-Savannah River Site, Aiken, SC. The concentration of Cu and Zn in the sediments has increased over the lifetime of the wetland and is a concern. A bioremediation option was investigated at the laboratory scale utilizing a newly isolated bacterium of the copper metabolizing genus Cupriavidus isolated from Tim's Branch Creek, a second-order stream that eventually serves as a tributary to the Savannah River, contaminated with uranium and other metals including copper, nickel, and mercury.

The impact of tritium phytoremediation on plant health as measured by fluorescence.

Phytoremediation, using plants for soil, sediment, or water contaminant clean-up, is an established technology dependent on plant health. Tritium (3H), a radioactive isotope of hydrogen that is generally found in the environment as tritiated water (HTO), is a low-level beta emitter with a half-life of 12.32 years.

Unveiling the Gut Microbiota and Resistome of Wild Cotton Mice, , from Heavy Metal- and Radionuclide-Contaminated Sites in the Southeastern United States.

The prevalence of antibiotic resistance genes (ARGs) can be driven by direct selection from antibiotic use and indirect selection from substances such as heavy metals (HMs). While significant progress has been made to characterize the influence of HMs on the enrichment and dissemination of ARGs in the environment, there is still much we do not know. To fill this knowledge gap, we present a comprehensive analysis of gut bacteria associated with wild cotton mice (Peromyscus gossypinus) trapped from several areas affected by legacies of HM and radionuclide contamination.

Removal, distribution and retention of metals in a constructed wetland over 20 years.

The A-01 wetland treatment system (WTS) was designed to remove metals (primarily copper) from the effluent at the A-01 National Pollution Discharge Elimination System (NPDES) outfall at the Savannah River Site, Aiken, SC. This research investigated metal removal, distribution and retention in the A-01 WTS over a period of 20 years. The findings are important for ensuring continued metal sequestration in the A-01 WTSs over time, providing management guidance for constructed wetlands, and investigating changes in metal remediation effectiveness as a wetland ages.

Co-occurrence of antibiotic, biocide, and heavy metal resistance genes in bacteria from metal and radionuclide contaminated soils at the Savannah River Site.

Contaminants such as heavy metals may contribute to the dissemination of antimicrobial resistance (AMR) by enriching resistance gene determinants via co-selection mechanisms. In the present study, a survey was performed on soils collected from four areas at the Savannah River Site (SRS), South Carolina, USA, with varying contaminant profiles: relatively pristine (Upper Three Runs), heavy metals (Ash Basins), radionuclides (Pond B) and heavy metal and radionuclides (Tim's Branch). Using 16S rRNA gene amplicon sequencing, we explored the structure and diversity of soil bacterial communities.

Legacy Contaminants in Aquatic Biota in a Stream Associated with Nuclear Weapons Material Production on the Savannah River Site.

Former nuclear weapons material production at the U.S. Department of Energy's Savannah River Site (SRS) has resulted in contamination of certain terrestrial and aquatic ecosystems on site with legacy wastes such as radiocesium (Cs), tritium (H), and metals.

Basins, beaver ponds, and the storage and redistribution of trace elements in an industrially impacted coastal plain stream on the Savannah River Site, SC, USA.

Accumulation of eleven trace elements in sediment was evaluated throughout an industrially disturbed headwater stream on the Savannah River Site, SC, USA. Sampling began at upstream sedimentation basins at the margins of industrial areas, continued longitudinally downstream to a beaver pond representing a potential sink in the mid-reaches, and ended in downstream reaches. Additionally, sediment from beaver impacted areas in another industrially disturbed stream and a reference stream were analyzed to assess the natural tendency of these depositional features to settle out trace elements.

Phosphate amendments for chemical immobilization of uranium in contaminated soil.

Uranium (U) contamination is a major environmental problem associated with the mining and processing of nuclear materials for both weapons and power production. When possible, in situ soil remediation techniques are preferable for reducing the risk associated with diffuse low-level U contamination. Uranium is known to form sparingly soluble phosphate compounds that persist in the environment.

Using porous iron composite (PIC) material to immobilize rhenium as an analogue for technetium.

Technetium (Tc), a uranium-235 (U) and plutonium-239 (Pu) fission product, is a primary risk driver in low level radioactive liquid waste at U.S. Department of Energy sites.

Metagenomics-Guided Survey, Isolation, and Characterization of Uranium Resistant Microbiota from the Savannah River Site, USA.

Despite the recent advancements in culturomics, isolation of the majority of environmental microbiota performing critical ecosystem services, such as bioremediation of contaminants, remains elusive. Towards this end, we conducted a metagenomics-guided comparative assessment of soil microbial diversity and functions present in uraniferous soils relative to those that grew in diffusion chambers (DC) or microbial traps (MT), followed by isolation of uranium (U) resistant microbiota. Shotgun metagenomic analysis performed on the soils used to establish the DC/MT chambers revealed Proteobacterial phyla and genus to be the most abundant among bacteria.

Porous iron material for TcO- and ReO- sequestration from groundwater under ambient oxic conditions.

Technetium-99 (Tc) is a major contaminant at nuclear power plants and several US Department of Energy sites. Its most common aqueous species, pertechnetate (TcO), is very mobile in the environment, and currently there are no effective technologies for its sequestration. In this work, a porous iron (pFe) material was investigated for TcO and perrhenate (ReO) sequestration from artificial groundwater.

Removal of low levels of Cu from ongoing sources in the presence of other elements - Implications for remediated contaminated sediments.

Mesocosms were used to investigate the effects of Cu influx, alone and in the presence of other elements, on sediments remediated by active caps, passive caps, and in situ treatment. Competitive interactions between Cu and other elements were investigated because contaminants often co-occur. Elements in surface water remained at significantly lower concentrations in mesocosms with apatite and mixed amendment caps than in mesocosms with passive sand caps or uncapped sediment.

Iodine speciation in a silver-amended cementitious system.

Silver-impregnated zeolite (AgIZ) has been used for removing radioiodine from contaminated groundwater and nuclear waste streams and the worldwide inventory of such secondary waste is rapidly increasing. The objective of this study was to 1) quantify the effectiveness of two grout waste forms for disposing of the used AgIZ, and 2) determine the I speciation leached from AgIZ encapsulated in grout. A 60-day kinetics batch experiment demonstrated that AgIZ encapsulated in slag-free grout was extremely effective at immobilizing I and Ag, a potential non-radioactive carcinogen.

Sediment and biota trace element distribution in streams disturbed by upland industrial activity.

Extensive industrial areas in headwater stream watersheds can severely impact the physical condition of streams and introduce contaminants. We compared 3 streams that received stormwater runoff and industrial effluents from industrial complexes to 2 reference streams. Reference streams provide a benchmark of comparison of geomorphic form and stability in coastal plain, sandy-bottomed streams as well as concentrations of trace elements in sediment and biota in the absence of industrial disturbance.

Sequestration of U(VI) from Acidic, Alkaline, and High Ionic-Strength Aqueous Media by Functionalized Magnetic Mesoporous Silica Nanoparticles: Capacity and Binding Mechanisms.

Uranium(VI) exhibits little adsorption onto sediment minerals in acidic, alkaline or high ionic-strength aqueous media that often occur in U mining or contaminated sites, which makes U(VI) very mobile and difficult to sequester. In this work, magnetic mesoporous silica nanoparticles (MMSNs) were functionalized with several organic ligands. The functionalized MMSNs were highly effective and had large binding capacity for U sequestration from high salt water (HSW) simulant (54 mg U/g sorbent).

Uranium fate in wetland mesocosms: Effects of plants at two iron loadings with different pH values.

Small-scale continuous flow wetland mesocosms (∼0.8 L) were used to evaluate how plant roots under different iron loadings affect uranium (U) mobility. When significant concentrations of ferrous iron (Fe) were present at circumneutral pH values, U concentrations in root exposed sediments were an order of magnitude greater than concentrations in root excluded sediments.

Functionalized magnetic mesoporous silica nanoparticles for U removal from low and high pH groundwater.

U(VI) species display limited adsorption onto sediment minerals and synthetic sorbents in pH <4 or pH >8 groundwater. In this work, magnetic mesoporous silica nanoparticles (MMSNs) with magnetite nanoparticle cores were functionalized with various organic molecules using post-synthetic methods. The functionalized MMSNs were characterized using N2 adsorption-desorption isotherms, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), (13)C cross polarization and magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectroscopy, and powder X-ray diffraction (XRD), which indicated that mesoporous silica (MCM-41) particles of 100-200nm formed around a core of magnetic iron oxide, and the functional groups were primarily grafted into the mesopores of ∼3.

Iron mineralogy and uranium-binding environment in the rhizosphere of a wetland soil.

Wetlands mitigate the migration of groundwater contaminants through a series of biogeochemical gradients that enhance multiple contaminant-binding processes. The hypothesis of this study was that wetland plant roots contribute organic carbon and release O2 within the rhizosphere (plant-impact soil zone) that promote the formation of Fe(III)-(oxyhydr)oxides. In turn, these Fe(III)-(oxyhydr)oxides stabilize organic matter that together contribute to contaminant immobilization.

Spectroscopic evidence of uranium immobilization in acidic wetlands by natural organic matter and plant roots.

Biogeochemistry of uranium in wetlands plays important roles in U immobilization in storage ponds of U mining and processing facilities but has not been well understood. The objective of this work was to study molecular mechanisms responsible for high U retention by Savannah River Site (SRS) wetland sediments under varying redox and acidic (pH = 2.6-5.

Uranium immobilization in an iron-rich rhizosphere of a native wetland plant from the Savannah River Site under reducing conditions.

The hypothesis of this study was that iron plaques formed on the roots of wetland plants and their rhizospheres create environmental conditions favorable for iron reducing bacteria that promote the in situ immobilization of uranium. Greenhouse microcosm studies were conducted using native plants (Sparganium americanum) from a wetland located on the Savannah River Site, Aiken, SC. After iron plaques were established during a 73-day period by using an anoxic Fe(II)-rich nutrient solution, a U(VI) amended nutrient solution was added to the system for an additional two months.

Retention and chemical speciation of uranium in an oxidized wetland sediment from the Savannah River Site.

Uranium speciation and retention mechanisms onto Savannah River Site (SRS) wetland sediments was studied using batch (ad)sorption experiments, sequential extraction, U L3-edge X-ray absorption near-edge structure (XANES) spectroscopy, fluorescence mapping and μ-XANES. Under oxidized conditions, U was highly retained by the SRS wetland sediments. In contrast to other similar but much lower natural organic matter (NOM) sediments, significant sorption of U onto the SRS sediments was observed at pH < 4 and pH > 8.