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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Mercury-Impacted Scrap Metal: Source and Nature of the Mercury

The reuse and recycling of industrial solid wastes such as scrap metal is supported and encouraged both internationally and domestically, especially when such wastes can be used as substitutes for raw material. However, scrap metal processing facilities, such as mini-mills, have been identified as a source of mercury (Hg) emissions in the United States. This research aims to better define some of the key issues related to the source and nature of mercury in the scrap metal waste stream. Overall, it is difficult to pinpoint the key mercury sources feeding into scrap metal recycling facilities, quantify their associated mercury concentrations, or determine which chemical forms are most significant. Potential sources of mercury in scrap metal include mercury switches from discarded vehicles, electronic-based scrap from household appliances and related industrial systems, and Hg-impacted scrap metal from the oil and gas industry. The form of mercury associated with scrap metal varies and depends on the source type. The specific amount of mercury that can be adsorbed and retained by steel appears to be a function of both metallurgical and environmental factors. In general, the longer the steel is in contact with a fluid or condensate that contains measurable concentrations of elemental mercury, the greater the potential for mercury accumulation in that steel. Most mercury compounds are thermally unstable at elevated temperatures (i.e., above 350°C). As such, the mercury associated with impacted scrap is expected to be volatilized out of the metal when it is heated during processing (e.g., shredding or torch cutting) or melted in a furnace. This release of fugitive gas (Hg vapor) and particulates, as well as Hg-impacted bag-house dust and control filters, could potentially pose an occupational exposure risk to workers at a scrap metal processing facility. Thus, identifying and characterizing the key sources of Hg-impacted scrap, and understanding the nature and extent of associated releases, represent a practical research need that is essential for improving the environmental management of Hg-impacted scrap and assessing measures to protect workers from potential health and safety hazards that might be posed by mercury and Hg-impacted scrap.

mercury↗
DOE OSTI2019

Determining the Reliability of Measuring Mercury Cycling Gene Abundance with Correlations with Mercury and Methylmercury Concentrations

Methylmercury (MeHg) is a bioaccumulative toxic contaminant in many ecosystems but factors governing its production are poorly understood. Recent work has shown that the anaerobic microbial conversion of mercury (Hg) to MeHg requires the Hg-methylation genes hgcAB and that these genes can be used as biomarkers in PCR-based estimators of Hg-methylator abundance. In an effort to determine reliable methods for assessing hgcA abundance and diversity and linking it to MeHg concentrations, multiple approaches were compared including metagenomic shotgun sequencing, 16S rRNA gene pyrosequencing and cloning/sequencing hgcAB gene products. Hg-methylator abundance was also determined by quantitative hgcA qPCR amplification and metaproteomics for comparison to the above measurements. Samples from eight Hg-contaminated sites were examined over a range of total Hg (HgT; 0.03–14 mg kg-1 wet wt. soil) and MeHg (0.05–27 µg kg-1 wet wt. soil) concentrations. In the metagenome and amplicon sequencing of hgcAB diversity, the Deltaproteobacteria were the dominant Hg-methylators, while Firmicutes and methanogenic Archaea were typically ~50% less abundant. This was consistent with metaproteomics estimates where the Deltaproteobacteria were consistently higher. The 16S rRNA gene pyrosequencing did not have sufficient resolution to identify hgcAB+ species. Metagenomic and hgcAB results were similar for Hg-methylator diversity and showed a tractable relationship between Hg-methylating bacteria and soil Hg concentrations among similar environmental samples. However, clade-specific qPCR-based approaches for hgcA are only appropriate when comparing the abundance of a particular clade across various samples.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

The use of a mercury biosensor to evaluate the bioavailability of mercury-thiol complexes and mechanisms of mercury uptake in bacteria

We discuss as mercury (Hg) biosensors are sensitive to only intracellular Hg, they are useful in the investigation of Hg uptake mechanisms and the effects of speciation on Hg bioavailability to microbes. In this study, bacterial biosensors were used to evaluate the roles that several transporters such as the glutathione, cystine/cysteine, and Mer transporters play in the uptake of Hg from Hg-thiol complexes by comparing uptake rates in strains with functioning transport systems to strains where these transporters had been knocked out by deletion of key genes. The Hg uptake into the biosensors was quantified based on the intracellular conversion of inorganic mercury (Hg(II)) to elemental mercury (Hg(0)) by the enzyme MerA. It was found that uptake of Hg from Hg-cysteine (Hg(CYS) 2 ) and Hg-glutathione (Hg(GSH) 2 ) complexes occurred at the same rate as that of inorganic complexes of Hg(II) into Escherichia coli strains with and without intact Mer transport systems. However, higher rates of Hg uptake were observed in the strain with a functioning Mer transport system. These results demonstrate that thiol-bound Hg is bioavailable to E. coli and that this bioavailability is higher in Hg-resistant bacteria with a complete Mer system than in non-resistant strains. No difference in the uptake rate of Hg from Hg(GSH) 2 was observed in E. coli strains with or without functioning glutathione transport systems. There was also no difference in uptake rates between a wildtype Bacillus subtilis strain with a functioning cystine/cysteine transport system, and a mutant strain where this transport system had been knocked out. These results cast doubt on the viability of the hypothesis that the entire Hg-thiol complex is taken up into the cell by a thiol transporter. It is more likely that the Hg in the Hg-thiol complex is transferred to a transport protein on the cell membrane and is subsequently internalized.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Mercury Accumulation in a Stream Ecosystem: Linking Labile Mercury in Sediment Porewaters to Bioaccumulative Mercury in Trophic Webs

Mercury (Hg) deposition and accumulation in the abiotic and biotic environments of a stream ecosystem were studied. This study aimed to link labile Hg in porewater to bioaccumulative Hg in biota. Sediment cores, porewaters, and biota were sampled from four sites along the Fourmile Branch (SC, USA) and measured for total Hg (THg) and methyl-Hg (MHg) concentrations. Water quality parameters were also measured at the sediment–water interface (SWI) to model the Hg speciation. In general, Hg concentrations in porewaters and bulk sediment were relatively high, and most of the sediment Hg was in the solid phase as non-labile species. Surface sediment presented higher Hg concentrations than the medium and bottom layers. Mercury methylation and MHg production in the sediment was primarily influenced by sulfate levels, since positive correlations were observed between sulfate and Hg in the porewaters. The majority of Hg species at the SWI were in non-labile form, and the dominant labile Hg species was complexed with dissolved organic carbon. MHg concentrations in the aquatic food web biomagnified with trophic levels (biofilm, invertebrates, and fish), increasing by 3.31 times per trophic level. Based on the derived data, a modified MHg magnification model was established to estimate the Hg bioaccumulation at any trophic level using Hg concentrations in the abiotic environment (i.e., porewater).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Mercury Speciation via Direct Mercury Analyzer

Mercury has no known biological role, but is present in every living thing and widespread in the environment. As mercury enters an aqueous system, it is subject to methylation or demethylation. Methylmercury selectively partitions into biota and biomagnifies through the food chain. Nearly all methylmercury exposures in the U.S. occur through eating fish and shellfish that contain higher levels of methylmercury. Methyl mercury and other organomercury compounds are more toxic than inorganic mercury. Thus, monitoring and understanding mercury speciation are key to effective environmental management. It is particularly important to be able to separate and measure bioaccumulative-toxic species of mercury such as methyl mercury. We are developing a protocol for utilizing the Direct Mercury Analyzer (DMA-80) for mercury speciation of water samples and to monitor methylmercury (meHg). Objectives: - Advance the understanding of the performance of the direct mercury analysis (DMA) under a range of DOE relevant water chemistry conditions to quantify total mercury: - Demonstrate the applicability of DMA to analysis of typical DOE high level liquid 'tank' waste samples using nonradioactive simulants; Test innovative sorbents to extend the range of the direct mercury analyzer to environmental concentration levels. - Perform scoping tests to demonstrate proof of principle for the chemical reduction amalgamation modular microcolumns for mercury speciation: Examine various microcolumn configurations and document speciation performance for typical DOE high level liquid 'tank' waste samples using nonradioactive simulants; Perform tests to examine extending the speciation paradigm to environmental concentration levels. General Method: all samples analyzed using a direct mercury analyzer (DMA 80) which automates the following steps: 1) pyrolysis to release the mercury, 2) catalysis to convert all mercury to elemental, 3) amalgamation to trap the mercury, 4) desorption to release the mercury as a pulse and 5) spectroscopy to detect the mercury.. Instrument analyzes all mercury species in solids and liquids. The DMA 'eliminates' sample preparation, reduces labor, decreases waste, and results in more practical and cost effective methods. To test the performance of the DMA for DOE relevant conditions, we analyzed samples representative of at high (mg/L) tank waste concentrations in water and in diluted tank waste simulant and analyzed samples representative of environmental (ng/L levels) in water. High concentration samples were analyzed directly in the instrument. Low concentration samples were analyzed by concentrating the mercury onto sorbents such as silica thiol or a mixture of silica thiol and copper. The concentration was performed using microcolumns and placing the columns into the DMA (see below) or by mixing the sorbent into the bulk sample and then filtering ad analyzing the filter in the DMA. Speciation Methods: The speciation tests were based on the selective reduction of inorganic mercury ions - Hg{sup (+} {sup or} {sup 2+)} - to elemental mercury - Hg(0). The elemental mercury is then trapped by amalgamation into the metal. These reactions do not impact methyl mercury allowing for separation. All reactions were performed using powdered elemental copper. To demonstrate proof-of-principle for the selective collection of inorganic mercury, samples were exposed to different amounts of powdered copper (and a control with no copper). This was done using microcolumns and a vacuum box. The columns were placed directly on the DMA for analysis. All materials and conditions were tested using solutions of both inorganic mercury and methyl mercury and all trials were in triplicate. Results and Observations: Validated DMA for high concentration Hg samples such as DOE tank waste: - Liquid inHg - samples were stable on autosampler carousel and results were accurate; - Liquid meHg - samples required a stabilizer. Si-Thiol (0.02 g) in the sample boat generated reliable meHg results. Stabilizer can be added for routine operations. Successful 'proof of principal' in extending DMA range to near environmental levels - using both microcolumns and filtration; - Filtration - Adding Si-Thiol (0.5 g) to sample extracted both inHg and meHg and preserved sample. Handling filters was labor intensive. - Microcolumns - best performance using a combination of copper and Si-Thiol - columns clogged and flowed slowly in some cases; - Practical limit may be in the range of 1 to 5 ng/L due to blanks; - Path Forward - Test additional packing materials and methods to improve flow and consistency, and approaches to minimize blanks. Successful 'proof of principal' for Hg speciation using chemical reduction and amalgamation; - Copper microcolumns (0.5 g Cu) selectively trapped inHg for high concentration mercury samples; - Copper microcolumns (0.5 g Cu selectively trapped inHg for large volume samples at environmental concentrations; - Some sorption of me Hg so that separations not quantitative; - Path Forward - test additional packing materials and alternate eluents to better trap inHg and minimize meHg retention in column.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Mercury Phase II Study - Mercury Behavior in Salt Processing Flowsheet

Mercury (Hg) in the Savannah River Site Liquid Waste System (LWS) originated from decades of canyon processing where it was used as a catalyst for dissolving the aluminum cladding of reactor fuel. Approximately 60 metric tons of mercury is currently present throughout the LWS. Mercury has long been a consideration in the LWS, from both hazard and processing perspectives. In February 2015, a Mercury Program Team was established at the request of the Department of Energy to develop a comprehensive action plan for long-term management and removal of mercury. Evaluation was focused in two Phases. Phase I activities assessed the Liquid Waste inventory and chemical processing behavior using a system-by-system review methodology, and determined the speciation of the different mercury forms (Hg+, Hg++, elemental Hg, organomercury, and soluble versus insoluble mercury) within the LWS. Phase II activities are building on the Phase I activities, and results of the LWS flowsheet evaluations will be summarized in three reports: Mercury Behavior in the Salt Processing Flowsheet (i.e. this report); Mercury Behavior in the Defense Waste Processing Facility (DWPF) Flowsheet; and Mercury behavior in the Tank Farm Flowsheet (Evaporator Operations). The evaluation of the mercury behavior in the salt processing flowsheet indicates, inter alia, the following: (1) In the assembled Salt Batches 7, 8 and 9 in Tank 21, the total mercury is mostly soluble with methylmercury (MHg) contributing over 50% of the total mercury. Based on the analyses of samples from 2H Evaporator feed and drop tanks (Tanks 38/43), the source of MHg in Salt Batches 7, 8 and 9 can be attributed to the 2H evaporator concentrate used in assembling the salt batches. The 2H Evaporator is used to evaporate DWPF recycle water. (2) Comparison of data between Tank 21/49, Salt Solution Feed Tank (SSFT), Decontaminated Salt Solution Hold Tank (DSSHT), and Tank 50 samples suggests that the total mercury as well as speciated forms in the assembled salt batches in Tanks 21/49 pass through the Actinide Removal Process (ARP) / Modular Caustic Side Solvent Extraction Unit (MCU) process to Tank 50 with no significant change in the mercury chemistry. (3) In Tank 50, Decontaminated Salt Solution (DSS) from ARP/MCU is the major contributor to the total mercury including MHg. (4) Speciation analyses of TCLP leached solutions of the grout samples prepared from Tank 21, as well as Tank 50 samples, show the majority of the mercury released in the solution is MHg.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Mercury speciation using microcolumns with a direct mercury analyzer (DMA). Development of analytical method for the Savannah River Site liquid system

Mercury in the Savannah River Site (SRS) Liquid Waste System (LWS) exists in various forms, including: a) ionic inorganic mercury, organomercury (e.g., methyl Hg), and other less abundant species dissolved in LWS fluids, b) mercury solids such as oxides, hydroxides, amalgams, sulfides, and sorbed mercury, c) accumulations of dense liquid elemental mercury, and d) vapor phase elemental and organomercury mercury in tank headspace gas and in evaporators. Strategic and proactive management of the estimated 60,000 Kg mercury in the LWS requires deployment of efficient and effective paradigms for sampling and analysis of the total quantity of mercury in the various physical-chemical forms. Scoping tests of selective gas-phase sorbents for mercury speciation were performed to support LWS objectives. This research specifically focused on developing and testing streamlined methods to obtain high-quality analytical results for gaseous mercury species. The proposed methods are straightforward, using small columns (microcolumns) filled with materials that selectively sorb one or more target forms of mercury. Simple differentiation of mercury species and quantification is then achieved using an efficient thermal-desorption-based total mercury analyzer as the final step. Benefits associated with transitioning from multistep procedures such as EPA Methods 245.1, 1630 and 1631to streamlined microcolumn approaches include reduced analysis time, labor, and waste generation. Such transitioning would maximize the value of the current deployment of direct mercury analysis (EPA Method 7473) at SRS. This work has two target end uses: 1) simplifying the analysis steps and reducing costs for liquid samples (e.g., developing a total organic mercury (TOM) method), and 2) providing options for high-quality onsite analysis and rapid turnaround for gas samples in support of SRS LWS industrial hygiene (IH) objectives.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Results of the Analyses of SMECT Mercury Sample Collected During Mercury Pump (MB1) Functional Check

A pump added to remove mercury from the sump of the Slurry Mix Evaporator Condensate Tank (SMECT) in DWPF was successfully tested in 2020, resulting in a sample of contaminated mercury obtained from the Mercury Purification Process (MPP) cell. The mercury in the sump of the SMECT was present as a result of steam stripping of sludge slurry in the Sludge Receipt and Adjustment Tank (SRAT) at DWPF. A schematic of the MPP system provided by DWPF personnel is shown in Appendix A. DWPF personnel supplied the following detailed description of the Hg sampling: “The sample provided is the result of DWPF extraction of mercury by means of the Mercury Pump-Water Cart. The Mercury Pump extracted the sample from the SMECT mercury sump. The pump uses pressurized water to transfer a small amount of mercury to a leachate bucket located at the Lab Mercury cell. The mercury and water were allowed to be self separated, and mercury was gravity decanted from the leachate bucket.” DWPF personnel indicate that the leachate bucket is equipped with both a top stopcock/drain and a lower/bottom stopcock/drain from which the mercury was decanted or drained out, while the separated water layer remained above the mercury during draining. The DWPF customer requested SRNL to analyze the sample for the following: gross alpha/nonvolatile beta analysis and perform a Toxicity Characteristic Leaching Procedure (TCLP) per the Environmental Protection Agency's Test Methods for Evaluating Solid Waste: Physical/Chemical Methods, SW-846. While the TCLP was preferred, a Total Metals analysis of the eight Resource Conservation and Recovery Act (RCRA) metals was deemed acceptable.2 The analytical data collected on this mercury sample will be used in planning for sample disposition as well to start a profile for future Hg disposition of Hg collected from steam stripping.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

Chemical Form Matters: Differential Accumulation of Mercury Following Inorganic and Organic Mercury Exposures in Zebrafish Larvae

Mercury, one of the most toxic elements, exists in various chemical forms each with different toxicities and health implications. Some methylated mercury forms, one of which exists in fish and other seafood products, pose a potential threat, especially during embryonic and early postnatal development. Despite global concerns, little is known about the mechanisms underlying transport and toxicity of different mercury species. To investigate the impact of different mercury chemical forms on vertebrate development, we have successfully combined the zebrafish, a well-established developmental biology model system, with synchrotron-based X-ray fluorescence imaging. Our work revealed substantial differences in tissue-specific accumulation patterns of mercury in zebrafish larvae exposed to four different mercury formulations in water. Methylmercury species not only resulted in overall higher mercury burdens but also targeted different cells and tissues than their inorganic counterparts, thus revealing a significant role of speciation in cellular and molecular targeting and mercury sequestration. For methylmercury species, the highest mercury concentrations were in the eye lens epithelial cells, independent of the formulation ligand (chloride versus L-cysteine). For inorganic mercury species, in absence of L-cysteine, the olfactory epithelium and kidney accumulated the greatest amounts of mercury. However, with L-cysteine present in the treatment solution, mercuric bis-L-cysteineate species dominated the treatment, significantly decreasing uptake. Our results clearly demonstrate that the common differentiation between organic and inorganic mercury is not sufficient to determine the toxicity of various mercury species.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Bench Scale Study of Coating Formulations for Abatement of Mercury Vapor and Recovery of Mercury Spills

A sealant formulation has been developed that effectively mitigates human exposure to elemental mercury vapor evolving from spilled mercury. The sealant may be dispensed using a fogging methodology (for industrial settings) or a common spray bottle (for home or school settings). In parallel, the potential for Hg recovery using strippable coatings was evaluated. Four liquid coatings were evaluated: one fogging fixative (FX2) developed at INL for the containment of surface and airborne contamination and three commercially available strippable decontamination gels (Carboset 441, Encor 449, and Stripcoat TLC Free). Bench scale mercury vapor abatement tests were conducted in an enclosure using FX2 with the addition of a mercury absorbent and a mercury reactant. Testing with FX2 showed the reactant contributed significantly to reducing the rate of mercury evaporation. The reactant had a minimal impact on the mercury evaporation rate for the strippable coatings. The potential of strippable coatings to remove/recover mercury was inferred from the adhesive and cohesive performance of sprayable dilutions of the coatings applied to porous and non-porous surfaces. Testing provided the following results: • Mercury vapor concentration was reduced by a factor of 40 using the reactant enhanced FX2 solution, as well as with dilutions of Carboset and Encor. Dilute Stripcoat was less effective at reducing Hg evaporation. • A 100× reduction in Hg evaporation rate was achieved using a coating of FX + the Hg reactant (a.k.a. FX Hg), compared to uncoated Hg. • A 2× reduction in the Hg vapor accumulation rate was achieved using FX Hg, compared to the strippable coatings. • Strippability and adhesion tests show that dilutions of Carboset and Stripcoat can be stripped from a variety of indoor surfaces. Dilute Encor was not strippable. Results suggest FX Hg and dilute Carboset will likely reduce Hg vapor concentrations, in an indoor setting, to a level at or below the Occupational Safety and Health Administration 8-hour human exposure limit (0.1 mg/m3). FX Hg dispensed via fogging would increase worker safety during remediation and demolition of industrial facilities with high levels of elemental mercury contamination. When applied via spray bottle, FX Hg may provide a safe and convenient method for the mitigation of Hg vapor in residential or commercial settings (e.g., offices, homes, schools). This approach would be most beneficial where recovery of the spilled Hg is impractical. A sprayed then stripped application of dilute Carboset may provide a safe and convenient method for recovery of small Hg spills in residential and commercial settings. Further testing is required to determine if liquid Hg sufficiently adheres to the strippable coating to be recovered in this way. If it can be dispensed as a fog, dilute Carboset could be employed to recover Hg contamination in industrial settings. Testing of the foggability of dilute Carboset is required to assess this potential.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2012

Remediation of Mercury-Contaminated Storm Sewer Sediments from the West End Mercury Area at the Y-12 National Security Complex in Oak Ridge, Tennessee - 12061

The Y-12 National Security Complex in Oak Ridge, TN has faced an ongoing challenge from mercury entrapped in soils beneath and adjacent to buildings, storm sewers, and process pipelines. Previous actions to reduce the quantity and/or mobilization of mercury-contaminated media have included plugging of building floor drains, cleaning of sediment and sludge from sumps, manholes, drain lines, and storm sewers, lining/relining of storm sewers and replacement of a portion of the storm sewer trunk line, re-routing and removal of process piping, and installation of the Central Mercury Treatment System to capture and treat contaminated sump water. Despite the success of these actions, mercury flux in the storm sewer out-falls that discharge to Upper East Fork Poplar Creek (UEFPC) continues to pose a threat to long-term water quality. A video camera survey of the storm sewer network revealed several sections of storm sewer that had large cracks, separations, swells, and accumulations of sediment/sludge and debris. The selected remedy was to clean and line the sections of storm sewer pipe that were determined to be primary contributors to the mercury flux in the storm sewer out-falls. The project, referred to as the West End Mercury Area (WEMA) Storm Sewer Remediation Project, included cleaning sediment and debris from over 2,460 meters of storm sewer pipe followed by the installation of nearly 366 meters of cure-in-place pipe (CIPP) liner. One of the greatest challenges to the success of this project was the high cost of disposal associated with the mercury-contaminated sludge and wastewater generated from the storm sewer cleaning process. A contractor designed and operated an on-site wastewater pre-treatment system that successfully reduced mercury levels in 191 cubic meters of sludge to levels that allowed it to be disposed at Nevada Nuclear Security Site (NNSS) disposal cell as a non-hazardous, low-level waste. The system was also effective at pre-treating over 1,514,000 liters of wastewater to levels that met the waste acceptance criteria for the on-site West End [wastewater] Treatment Facility (WETF). This paper describes the storm sewer cleaning and lining process and the methods used to process the mercury-contaminated sludge and wastewater, as well as several 'lessons learned' that would be relevant to any future projects involving storm sewer cleaning and debris remediation. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2012

Potential Moderating Effects of Selenium on Mercury Uptake and Selenium:Mercury Molar Ratios in Fish From Oak Ridge and Savannah River Site - 12086

Mercury contamination is an important remediation issue at the U.S. Department of Energy's (DOE) Oak Ridge Reservation and to a lesser extent at other DOE sites because of the hazard it presents, potential consequences to humans and eco-receptors, and completed pathways, to offsite receptors. Recent work has emphasized that selenium might ameliorate the toxicity of mercury, and we examine the selenium:mercury (Se:Hg) molar ratios in fish from Oak Ridge, and compare them to Se:Hg molar ratios in fish from the Savannah River. Selenium/mercury molar ratios varied considerably among and within fish species. There was considerable variation in the molar ratios for individual fish (as opposed to mean ratios by species) for freshwater fish from both sites. The inter-individual variation in molar ratios indicates that such that the molar ratios of mean Se and Hg concentrations may not be representative. Even for fish species with relatively low mercury levels, some individual fish have molar ratios less than unity, the value sometime thought to be protective. Selenium levels varied narrowly regardless of fish size, consistent with homeostatic regulation of this essential trace element. The data indicate that considerable attention will need to be directed toward variations and variances, as well as the mechanisms of the interaction of selenium and mercury, before risk assessment and risk management policies can use this information to manage mercury pollution and risk. Even so, if there are high levels of selenium in the fish from Poplar Creek on Oak Ridge, then the potential exists for some amelioration of adverse health effects, on the fish themselves, predators that eat them, and people who consume them. This work will aid DOE because it will allow managers and scientists to understand another aspect that affects fate and transport of mercury, as well as the potential effects of methylmercury in fish for human and ecological receptors. The variability within fish species, however, suggests that the relative Se:Hg molar ratios in fish are not stable enough to be used in risk assessment at this time. Nor is it known how much excess selenium is required to confer any degree of protectiveness. That is, in conducting risk assessments, it is not possible to determine the spread of ratios, which would be needed for probabilistic risk assessment. Significantly more fish samples per species are required to begin to generate data that would allow it use in risk assessment. Adding Se:Hg molar ratios seems to complicate risk assessment for the potential adverse effects of mercury exposure, and using mercury levels at this time remains the most viable option. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Efficient Mercury Capture Using Functionalized Porous Organic Polymer

The primary challenge in materials design and synthesis is achieving the balance between performance and economy for real-world application. Here, this issue is addressed by creating a thiol functionalized porous organic polymer (POP) using simple free radical polymerization techniques to prepare a cost-effective material with a high density of chelating sites designed for mercury capture and therefore environmental remediation. The resulting POP is able to remove aqueous and airborne mercury with uptake capacities of 1216 and 630 mg g -1 , respectively. The material demonstrates rapid kinetics, capable of dropping the mercury concentration from 5 ppm to 1 ppb, lower than the US Environmental Protection Agency's drinking water limit (2 ppb), within 10 min. Furthermore, the material has the added benefits of recyclability, stability in a broad pH range, and selectivity for toxic metals. These results are attributed to the material's physical properties, which include hierarchical porosity, a high density of chelating sites, and the material's robustness, which improve the thiol availability to bind with mercury as determined by X-ray photoelectron spectroscopy and X-ray absorption fine structure studies. Finally, the work provides promising results for POPs as an economical material for multiple environmental remediation applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Formation of soluble mercury oxide coatings: Transformation of elemental mercury in soils

In this study, the impact of mercury (Hg) on human and ecological health has been known for decades. Although a treaty signed in 2013 by 147 nations regulates future large-scale mercury emissions, legacy Hg contamination exists worldwide and small-scale releases will continue. The fate of elemental mercury, Hg(0), lost to the subsurface and its potential chemical transformation that can lead to changes in speciation and mobility are poorly understood. Here, we show that Hg(0) beads interact with soil or manganese oxide solids and X-ray spectroscopic analysis indicates that the soluble mercury coatings are HgO. Dissolution studies show that, after reacting with a composite soil, >20 times more Hg is released into water from the coated beads than from a pure liquid mercury bead. An even larger, >700 times, release occurs from coated Hg(0) beads that have been reacted with manganese oxide, suggesting that manganese oxides are involved in the transformation of the Hg(0) beads and creation of the soluble mercury coatings. Although the coatings may inhibit Hg(0) evaporation, the high solubility of the coatings can enhance Hg(II) migration away from the Hg(0)-spill site and result in potential changes in mercury speciation in the soil and increased mercury mobility.

58 GEOSCIENCES↗
DOE OSTI2019

Extraction of Mercury Utilizing 3D Printed Media-Mercury Extraction Coalescer (MEC)

This project was undertaken to address the concern of mercury species present in chemical reprocessing facilities and environmental remediation sites. Typical elemental mercury removal is performed by steam stripping. As efficient as this process is, the vaporized elemental mercury is often condensed along with acidic condensate. The acidic conditions re-dissolve the elemental mercury, transferring it back into the aqueous stream, and undoing the energy-intensive steam stripping process. This project looked to design and produce a 3D printed component to act as a mercury vapor/liquid coalescer utilizing structural and chemical features to segregate elemental mercury from an aqueous solution or process offgas and improving elemental mercury retention and removal from the recirculated condensate stream. The aim of this project is to take inspiration from nature, for example the lotus leaf, and the advantage of advanced manufacturing techniques, in this case 3D printing, to produce a functional solution to a serious environmental issue, the accumulation of elemental mercury in aqueous environments.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗