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Baum, Steven R.

Publications and source records attributed to Baum, Steven R..

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

200-DV-1 Laboratory Treatability Study: Proof-of-Principle Results

This document presents the Phase 1 technical approach and results of laboratory-scale treatability testing of nine in situ remedial technologies for their consideration in a future Feasibility Study (FS) for the 200-DV-1 OU. The primary objective of this initial assessment was a proof-of-principle testing evaluation primarily via batch experiments to determine the potential reduction and sequestration of primary contaminants of interest with and without potential co-contaminants of interest. An effectiveness rate of 35% transformation to immobile or nontoxic end products, along with other experimental indicators, was used by the project team to determine the technologies that advanced to Phase 2 for further evaluations. For most technologies, the performance was evaluated based on a series of sequential extractions designed to evaluate the mobility of contaminants before and after treatment, with each subsequent extraction representing a relative decrease in mobility. The results of this study will be used to inform testing for Phase 2 of the treatability study for further evaluation of selected technologies. The final results from the treatability study, following the completion of remaining experimental phases, will be used to determine whether the technologies tested can be appropriately evaluated in a FS to expand on the limited number of viable DVZ remediation technologies. After completion of the laboratory treatability study and the 200-DV-1 OU Remedial Investigation (RI) and Resource Conservation and Recovery Act Facility Investigation (RFI) of the waste sites, results will be evaluated to determine whether field studies are needed to provide additional information on effectiveness, implementability, or costs for evaluating these technologies in the FS for their site-specific application.

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DOE OSTI2023

Sample Preparation Method for Low-Level Total 129 I Measurements by ICP-MS

Trace-level measurements of iodine’s isotopic ( 129 I and 127 I) and chemical species distributions are needed for an accurate understanding of radioiodine migration in the Hanford subsurface. Pacific Northwest National Laboratory (PNNL) previously developed a novel analytical method for iodine characterization that uses ion chromatography (IC) coupled to inductively coupled mass spectrometry (ICP-MS). While the method can measure speciated forms of 129 I at levels below the drinking water standard, an interference from molybdenum (Mo) prevents the assay from quantifying the $\underline{total}$ 129 I concentration in many Hanford sample matrices. In this work, solvent extraction was evaluated as a sample preparation method for eliminating the Mo interference. A series of 10 experiments was conducted in which solutions containing known amounts of iodate or iodide were treated by solvent extraction, and the extracted solutions were analyzed for total iodine concentrations by ICP MS. Several extraction parameters such as reagent concentrations and chemical reaction times were systematically adjusted in attempts to optimize the extraction process. While solvent extraction was shown to be effective at removing Mo, there was a consistent inability to recover more than approximately 75% of the total iodine in most experiments. This would reduce the ability to detect 129 I at levels near the drinking water standard. Additionally, the extraction efficiencies in several experiments were highly variable, suggesting that solvent extraction could add significant uncertainty to radioiodine measurements. We recommend evaluating ion exchange as an alternative sample preparation approach in fiscal year (FY) 2024.

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DOE OSTI2022

Characterization of Contaminants and Mobility in WMA A-AX Boreholes D0006 and D0008

This study was initiated to determine if subsurface contaminants in the A-AX vadose zone at the Hanford site (boreholes D0006 and D0008) caused corrosion of nearby stainless steel well casings (299-E-24-19, 299-E25-46, and 299-E25-236) and, based on the type and distribution of contaminants, determine if contaminants are from one or more sources including a) the A-104 and/or A-105 tanks, b) the 242A evaporator, and c) the 200-E-286 ditch. A tiered approach was used for characterizing contaminants in vadose zone sediments starting with mobile and total contaminant concentrations (Tier 1), characterizing contaminant speciation (Tier 2), and measuring contaminant leaching (Tier 3). Total and mobile contaminant measurements at seven depths showed elevated sulfate and nitrate in all samples (130 to 280 ft depth), elevated chloride in five depths, and no elevated radionuclides except I-129 in D0006 at 206 to 208 ft depth. If these contaminants were initially acidic, stainless-steel corrosion would occur. However, because sediments likely have a high acid neutralization capacity, an acidic spill would have been neutralized within tens of feet, so casing corrosion would likely occur in shallow sediments. GEL labs data also shows low (but above natural) chromate from shallow to 170 ft depth, then higher chromate to 280 ft, suggesting a surface Cr spill or casing corrosion. GEL labs data also showed evidence of more than one plume, with deep nitrate, sulfate, and chloride migration, but only shallow tritium migration. Tritium should migrate nearly unretarded in the subsurface like nitrate and chloride. Elevated aqueous cations and anions in the D0006 206 to 208' depth pore water (SO 4 2- , NO 3 - , Na + , K + , Ca 2+ , Mg 2+ , Si) could be the result of acid disposal and calcite dissolution at shallow depth, with deeper migration of SO 4 2- , NO 3 - from acids and Ca 2+ and Mg 2+ from calcite. Elevated Si (160 mg/L) indicates dissolution of clays or other silicates, which can also occur in acids. Acid extractable metals did show elevated Cr (but not Fe, Ni, Mo, and Mn) above natural levels, which may indicate stainless-steel well corrosion or transport of metals from a shallow spill. The elevated I-129 in D0006 at 206 to 208' depth was low with 0.34 μg/g in pore water and 1.5 μg/g total extractable I-129 in the sediment, which indicates significant fraction of I-129 was bound in one or more precipitates. Although total I-129 was below detection limits in most extractions due to high molybdate interference, I-127 analysis provided some insight into potential precipitate phases. Total I-127 was mainly extracted by acetate or acetic acid (67%), which may be iodine in calcite. Inorganic carbon measurement identified 1.65% calcite, and total organic carbon (TOC) was below detection limits, so iodine was not associated with organic matter. Nearly all the I-127 was present as iodide. In 1-D leach experiments, I-127 as iodide leached from the sediment within 2 pore volumes. Due to high and dynamic molybdate leaching from the sediment and interference with I-129 analysis, there were few quantifiable I-129 measurements. The calculated molybdate release rates from the sediment suggested Mo was being released from the same precipitate phase, such as molybdate incorporated into calcite. Overall, because there was little radioactive contamination measured in D0006 and D0008 boreholes, potential releases from A-104 and A-105 did not reach this location south of the A tank farm. Elevated cations and anions found in D0006 and D0008 at depth as the result of acidic disposal could cause shallow stainless steel casing corrosion. The nearby 242A evaporator generally contained alkaline waste and tritium, but the nearby 200-E-286 ditch generally contained high Cl - liquid effluent, so these are unlikely to be acidic sources.

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DOE OSTI2020

Long-term Accumulation, Depth Distribution, and Speciation of Silver Nanoparticles in Biosolids-Amended Soils

Biosolids, when applied to soil, can be a source of metals and metal nanoparticles. One of the metals that forms nanoparticles is silver (Ag), which is commonly used in elemental (Ag(0)) form as an engineered nanomaterial in industrial or consumer products. The objective of this study was to quantify and characterize the accumulation and transport of Ag in a natural soil that has received agronomically-recommended rates of biosolids as fertilizer for the past 23 years (1994{2017). Total Ag concentrations were measured in biosolids and soil samples collected from 0 to 10 cm between 1996 and 2017. In addition, the depth distribution of Ag in the soil down to 60-cm depth was measured in 2017. Electron microscopy, in combination with X-ray spectroscopy, and X-ray absorption spectroscopy were used to identify the elemental association and oxidation state of the Ag in the samples. The Ag concentrations in the biosolids-amended soil increased steadily from 1996 until 2007, after which the concentrations leveled off at about 1.25 mg Ag kg-1 soil. This corresponded with a decrease of Ag concentrations in the biosolids over time. The majority of the Ag (82%) was confined to the top 10 cm of the soil, small amounts (14%) were detected in 10 to 20-cm depth, and trace amounts (4%) in 30 to 40-cm depth. The Ag in the biosolids and soil was identified as Ag-containing nanoparticles with a diameter of 10 to 12 nm. Ag was associated with S suggest that these 19 nanoparticles are Ag2S. This could be corroborated in biosolids with X-ray absorption spectroscopy (XANES); however, the Ag concentrations in the soil samples were too low to allow identification with XANES. Biosolids, when applied at agronomic rates in dryland cropping systems, represent an economically viable source of crop nutrients. In our study, long-term application of biosolids did not increase the concentration of total Ag in soil above a maximum of 1.5 mg Ag kg-1, and the Ag is present in the sulfide form. This concentration is below ecotoxicity limits for Ag2S in soil.

Taylor, Stephen E.↗
DOE OSTI2020

Evaluation of the Change in Uranium Mobility in Sediments from the Hanford 300-FF-5 Stage B Polyphosphate Field Injection

The purpose of this study was to evaluate the change in uranium mobility in the periodically re-wetted zone (PRZ) and upper unconfined aquifer of the Hanford Site’s 300-FF-5 operable unit as a result of Stage B polyphosphate (PO 4 ) injections. These 300 Area sediments are beneath or near the former North Process Pond, which has previously been shown to contain metatorbernite [Cu(UO 2 ) 2 (PO 4 ) 2 •8H 2 O] and uranophane [Ca(UO 2 ) 2 (SiO 3 OH) 2 •5H 2 O], along with aqueous and adsorbed uranium (U), and small amounts of U in calcite as a result of acidic disposal with a significant number of co-contaminants. Previous laboratory-scale studies have identified multiple mechanisms that decrease uranium mobility with polyphosphate injection: (a) precipitation of a low-solubility uranium-phosphate mineral (autunite); (b) precipitation of a Ca-phosphate solid that incorporates U; (c) precipitation of Ca-phosphate mineral (apatite group minerals) that coats existing uranium phases (i.e., U in calcite, U in Fe-oxides), reducing uranium leaching; and (d) aqueous Ca-U-carbonate species adsorption onto apatite. Given the significant amount of apatite precipitation, other U phases such as carbonates could also coprecipitate with apatite. To quantify differences in solubility, leachability, and phases of uranium between pre- and post-PO 4 -treated sediments, different types of analyses were conducted, including analysis of uranium in (a) a carbonate solution extraction from sediment over 1000 h (41.67 days), (b) six sequential liquid extractions from sediment over approximately 1 week, (c) leaching of uranium from sediments in one dimensional (1-D) column experiments over 2 months, and (d) solid phase characterization of select sediments. An additional extraction and solid phase measurements were conducted to evaluate phosphate precipitate formation. Metals were also analyzed in sequential liquid extractions as indicators of (a) amendment injection delivery, (b) co-contaminant movement, and (c) changes in solid phases. Aqueous and solid phase carbonate measurements were also conducted to evaluate changes in carbonates.

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