Impact of Alteration Phase Formation and Microbial Activity on the Fate and Transport of the Actinides and Fission Products: Alteration Phase Analysis

The study of the behavior and movement of radionuclides in the environment is significant to many projects of interest to Southern Nevada, especially for the proposed Yucca Mountain Repository, as well as to the nation-wide issues of radiological releases from a variety of scenarios. Understanding and predicting the release, transport, and fate of radionuclides, particularly the actinide elements, in the Mojave/Great Basin geology is an extremely challenging, multi-faceted problem. In support of the national program to deepen our understanding of the behavior of radionuclides in the environment and to better predict the performance of a geological repository at Yucca Mountain, researchers at UNLV, under a cooperative agreement between and UNLV Research Foundation and the U.S. Department of Energy (#DE-FC28-04RW12237), will examine two key fate and transport issues: the potential impact of microorganisms and the impact of the formation of alteration phases due to the corrosion of the waste package and waste forms on the chemistry, fate, and transport of radionuclides released from the site. Task ORD-RF-01 (SIP-UNLV-046) is focused on the influence of microorganisms. Task ORD-RF-02 (SIP-UNLV-045) involves surface complexation and solid dissolution studies. This task, titled Impact of Alteration Phase Formation and Microbial Activity on the Fate and Transport of the Actinides and Fission Products: Alteration Phase Analysis, entails method development and elemental characterization of select alteration phases generated in Task ORD-RF-02. All of this work is subject to QARD and University and Community College System of Nevada (UCCSN) Quality Assurance (QA) Program requirement

Determining the Redox Properties of Yucca Mountain-Related Groundwater Using Trace Element Speciation for Predicting the Mobility of Nuclear Waste

The objective of this task is to determine the principal oxidation state (redox) species of select elements in samples of groundwater in the vicinity of Yucca Mountain (YM), which is being evaluated as a site for geologic storage of the nation’s spent nuclear fuel and high-level nuclear waste. Samples to be analyzed include, but are not limited to, groundwater from wells of the Nye County Early Warning Drilling Program. Elements to be studied include arsenic (As), antimony (Sb), selenium (Se), chromium (Cr), manganese (Mn), iron (Fe), copper (Cu), molybdenum (Mo), vanadium (V), tungsten (W), rhenium (Re), and uranium (U). The purpose is to develop a more accurate and complete description of the redox properties of YM-related groundwater, which influences the solubility and consequently the transport of radionuclides. Indeed, a possible natural barrier to radionuclide migration in the saturated zone (SZ) is the presence of non-oxidizing or reducing environments. For example, the mobility of Tc-99 in oxic groundwater, ascribed to the pertechnetate ion, is greatly diminished in reducing groundwater. The containment of radionuclides away from the accessible environment is a key feature in the Yucca Mountain performance assessment

Direct analysis of solid corrosion products by laser ablation ICP-MS: Method development and the interaction of aqueous uranium, gadolinium and neodymium with Iron Shot and Iron (III) Oxide

The purpose of this report is to summarize the work and present conclusions of Project Activity Task ORD-RF-03 conducted under cooperative agreement number DE-FC28-04RW12237 between the U.S. Department of Energy and the Nevada System of Higher Education (NSHE). The work was conducted in the Harry Reid Center for Environmental Studies of the University of Nevada Las Vegas from October 1, 2004 to September 30, 2006. The purpose of the study was to develop a method using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for the direct analysis of iron corrosion products, to evaluate its capabilities, advantages, and limitations, and to apply the method to examine the interaction of actinides, and other elements relevant to the long-term geologic storage of nuclear waste, with iron corrosion products. The desired quantification is for specific (targeted) sections of the surface; elemental ratios can be determined from the data if of interest

Bomb-Pulse Chlorine-36 At The Proposed Yucca Mountain Repository Horizon: An Investigation Of Previous Conflicting Results And Collection Of New Data

Previous studies by scientists at Los Alamos National Laboratory (LANL) found elevated ratios of chlorine-36 to total chloride ({sup 36}Cl/Cl) in samples of rock collected from the Exploratory Studies Facility (ESF) and the Enhanced Characterization of the Repository Block (ECRB) at Yucca Mountain as the tunnels were excavated. The data were interpreted as an indication that fluids containing 'bomb-pulse' {sup 36}Cl reached the repository horizon in the {approx}50 years since the peak period of above-ground nuclear testing. Moreover, the data support the concept that so-called fast pathways for infiltration not only exist but are active, possibly through a combination of porous media, faults and/or other geologic features. Due to the significance of {sup 36}Cl data to conceptual models of unsaturated zone flow and transport, the United States Geological Survey (USGS) was requested by the Department of Energy (DOE) to design and implement a study to validate the LANL findings. The USGS chose to drill new boreholes at select locations across zones where bomb-pulse ratios had previously been identified. The drill cores were analyzed at Lawrence Livermore National Laboratory (LLNL) for {sup 36}Cl/Cl using both active and passive leaches, with the USGS/LLNL concluding that the active leach extracted too much rock-Cl and the passive leach did not show bomb-pulse ratios. Because consensus was not reached between the USGS/LLNL and LANL on several fundamental points, including the conceptual strategy for sampling, interpretation and use of tritium ({sup 3}H) data, and the importance and interpretation of blanks, in addition to the presence or absence of bomb-pulse {sup 36}Cl, an evaluation by an independent entity, the University of Nevada, Las Vegas (UNLV), using new samples was initiated. This report is the result of that study. The overall objectives of the UNLV study were to investigate the source or sources of the conflicting results from the previous validation study, and to obtain additional data to determine whether or not there are bomb-pulse isotopes at the repository horizon. To that en4 we have engaged in discussions with previous investigators, reviewed reports, and analyzed archived samples. We have also collected new samples of rock from the ESF, soil profiles from the surface of Yucca Mountain, and opportunistic samples of seep water from inside the south ramp of the ESF

Air/surface exchange of gaseous elemental mercury at different landscapes in Mississippi, USA

© 2019 by the authors. Mercury (Hg) is a global pollutant with human health and ecological impacts. Gas exchange between terrestrial surfaces and the atmosphere is an important route for Hg to enter and exit ecosystems. Here, we used a dynamic flux chamber to measure gaseous elemental Hg (GEM) exchange over different landscapes in Mississippi, including in situ measurements for a wetland (soil and water), forest floor, pond, mowed field and grass-covered lawn, as well as mesocosm experiments for three different agricultural soils. Fluxes were measured during both the summer and winter. Mean ambient levels of GEM ranged between 0.93-1.57 ng m-3. GEM emission fluxes varied diurnally with higher daytime fluxes, driven primarily by solar radiation, and lower and more stable nighttime fluxes, dependent mostly on temperature. GEM fluxes (ng m-2 h-1) were seasonally dependent with net emission during the summer (mean 2.15, range 0.32 to 4.92) and net deposition during the winter (-0.12, range -0.32 to 0.12). Total Hg concentrations in the soil ranged from 17.1 ng g-1 to 127 ng g-1 but were not a good predictor of GEM emissions. GEM flux and soil temperature were correlated over the forest floor, and the corresponding activation energy for Hg emission was ~31 kcal mol-1 using the Arrhenius equation. There were significant differences in GEM fluxes between the habitats with emissions for grass \u3e wetland soil \u3e mowed field \u3e pond \u3e wetland water ≈ forest ≈ agriculture soils. Overall, we demonstrate that these diverse landscapes serve as both sources and sinks for airborne Hg depending on the season and meteorological factors

Bomb-pulse Chlorine-36 at the proposed Yucca Mountain repository horizon: An investigation of previous conflicting results and collection of new data

Previous studies by scientists at Los Alamos National Laboratory (LANL) found elevated ratios of chlorine-36 to total chloride (36C1/C1) in samples of rock collected from the Exploratory Studies Facility (ESF) and the Enhanced Characterization of the Repository Block (ECRB) at Yucca Mountain as the tunnels were excavated. The data were interpreted as an indication that fluids containing bomb-pulse 36C1 reached the repository horizon in the -50 years since the peak period of above-ground nuclear testing. Moreover, the data support the concept that so-called fast pathways for infiltration not only exist but are active, possibly through a combination of porous media, faults and/or other geologic features. Due to the significance of 36C1 data to conceptual models of unsaturated zone flow and transport, the United States Geological Survey (USGS) was requested by the Department of Energy (DOE) to design and implement a study to validate the LANL findings. The USGS chose to drill new boreholes at select locations across zones where bomb-pulse ratios had previously been identified. The drill cores were analyzed at Lawrence Livermore National Laboratory (LLNL) for 36C1/C1 using both active and passive leaches, with the USGS/LLNL concluding that the active leach extracted too much rock-Cl and the passive leach did not show bomb-pulse ratios. Because consensus was not reached between the USGS/LLNL and LANL on several fundamental points, including the conceptual strategy for sampling, interpretation and use of tritium (3H) data, and the importance and interpretation of blanks, in addition to the presence or absence of bomb-pulse 36C1, an evaluation by an independent entity, the University of Nevada, Las Vegas (UNLV), using new samples was initiated. This report is the result of that study. The overall objectives of the UNLV study were to investigate the source or sources of the conflicting results from the previous validation study, and to obtain additional data to determine whether or not there are bomb-pulse isotopes at the repository horizon. To that end, we have engaged in discussions with previous investigators, reviewed reports, and analyzed archived samples. We have also collected new samples of rock from the ESF, soil profiles from the surface of Yucca Mountain, and opportunistic samples of seep water from inside the south ramp of the ESF. Our sampling strategy in the ESF was to collect new rock samples in a manner that would optimize our chances of finding a 36C1 bomb-pulse signature, if one was present. Therefore the sampling and analytical methodology that yielded prior bomb-pulse ratios was replicated (to the extent possible). Specific geologic features (e.g., faults, cooling joints) and strategic locations (including the Ghost Dance, Sundance, Bow Ridge and Drill Hole Wash faults) were targeted. Moreover, extreme precautions were taken to collect samples, excavating a meter into the tunnel wall in some cases. Experiments were performed measuring trace elements and anions in leachates as a function of time to help guide our leaching conditions. Samples were analyzed for 36C1/C1 ratios, as well as 99Tc and 129I, two other radionuclides that can be associated with the bomb-pulse, in select samples. Finally, a column experiment was conducted mimicking the passage of bomb-pulse 36C1 through Yucca Mountain tuff (Topopah Spring Tuff middle nonlithophysal unit (Tptpmn)). The work faced several obstacles including an extended shutdown of the tunnel. In addition, some of the data collected early in the study were suspect because of unreasonably high 36C1/C1 ratios. Attempts to pinpoint the cause of the seemingly random and spurious results were unsuccessful. After moving to a different laboratory in a separate building and employing new supplies, control was gained over the background and blank results were consistent and acceptably small. Because of the setbacks only half (seven) of the ESF samples, but all of the soil and column-study samples, were analyzed in the favorable laboratory setting before the project ended. Overall, the experience highlights the challenging nature of the work and the high sensitivity of accelerator mass spectrometry (AMS) for 36C1

Corrosion and mass transport processes in Carbon steel miniature waste packages

In this study, we have systematically investigated corrosion and mass transport processes in carbon steel miniature waste packages (MWP) in dynamic systems (water in, water out) under varying chemical conditions. The MWP were fabricated to have similar configuration to the DOE Spent Nuclear Fuel (SNF) waste package and that individual components to be in scale with each other compare to the SNF waste package. Two MWP configurations were studied: a bathtub model and a flow-through model. By slowly dripping 4 different solutions (groundwater obtained from well water J-13 located near Yucca Mountain, and J-13 water adjusted to low-pH, high-salinity, and high salinity-high nitrate) into the MWP, we were able to investigate the manner of oxidation, identify transported minerals contained in the effluent, and characterize the mass transport in terms of particle size. Manner of oxidation. Through time-lapse digital photography, we were able to document the process of corrosion within a glass walled MWP. Formation of colored corrosion products including short-lived colored complexes was noted. A sequence of possible corrosion products was proposed. The availability of oxygen and limitation of diffusion through corrosion products lowers the rate of the corrosion process. In most cases the MWP exit hole sealed within 4 weeks of water introduction, resulting in overflow from the top of the MWP. This self-sealing is likely due to the larger molar volume of the corrosion products. The overflow water traveled on the outer surface of the MWP and hung at bottom before dripping out. Under these conditions corrosion to the bottom of the MWP was observed and eventual bottom failure is likely. It is recommended an addition of a skirt to the actual waste packages to deflect water away from the waste package. Identification of Transported Minerals. Through X-Ray Diffraction and Scanning Electron Microscopy studies of solids in the MWP effluent, we discovered that secondary minerals, such as goethite were prevalent. Many of these corrosion products were amorphous and would expect to have different properties (buffering, sorption) compared to more crystalline minerals. Individual particles ranged from about 0.2 to 0.8 (J,m in diameter and larger conglomerates of particles up to several um in diameter were also present. Mass Transport of Solids. The greatest mass of solids transported out of the MWP occurred under acidic conditions followed by the control (J-13) solution. The salt (high ionic strength) solutions were more variable due to experimental difficulties but appear not to enhance the corrosion process. The nature of the transported material also differed by solution-type. As expected, most of the iron (\u3e80%) was found in the dissolved state under acidic conditions, while solids (\u3e0.45um in diameter) dominated in the effluent of the other solutions

Gaseous elemental mercury concentrations along the northern gulf of mexico using passive air sampling, with a comparison to active sampling

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Mercury is a toxic element that is dispersed globally through the atmosphere. Accurately measuring airborne mercury concentrations aids understanding of the pollutant’s sources, distribution, cycling, and trends. We deployed MerPAS® passive air samplers (PAS) for ~4 weeks during each season, from spring 2019 to winter 2020, to determine gaseous elemental mercury (GEM) levels at six locations along the northern Gulf of Mexico, where the pollutant is of particular concern due to high mercury wet deposition rates and high concentrations in local seafood. The objective was to (1) evaluate spatial and seasonal trends along the Mississippi and Alabama coast, and (2) compare active and passive sampling methods for GEM at Grand Bay National Estuarine Research Reserve, an Atmospheric Mercury Network site. We observed higher GEM levels (p \u3c 0.05) in the winter (1.53 ± 0.03 ng m−3) compared to other seasons at all sites; with the general pattern being: winter \u3e spring \u3e summer ≈ fall. Average GEM levels (all deployment combined) were highest at Bay St. Louis (1.36 ± 0.05 ng m−3), the western-most site nearest the New Orleans metropolitan area, and lowest at Cedar Point (1.07 ± 0.09 ng m−3), a coastal marsh with extensive vegetation that can uptake GEM. The MerPAS units compared reasonably well with the established active monitoring system, but gave slightly lower concentrations, except in the winter when the two methods were statistically similar. Both the passive and active sampling methods showed the same seasonal trends and the difference between them for each season was \u3c15%, acceptable for evaluating larger spatial and temporal trends. Overall, this work demonstrates that PASs can provide insight into GEM levels and the factors affecting them along coastal regions

Microsatellite Markers for Red Drum, Sciaenops ocellatus

Polymerase chain reaction (PCR) primers are reported for 68 nuclear-encoded microsatellites developed during the past several years from genomic libraries of red drum (Sciaenops ocelwtus). All68 microsatellites were tested for reproducibility and polymorphism on a sample of five to 12 red drum; 60 of the microsatellites were found to be polymorphic. Estimates of observed and expected heterozygos- ity (gene diversity) and tests of conformity of genotypes to Hardy-Weinberg equi- librium were carried out for a subset of 31 microsatellites on a larger sample of 45 adults provided by Texas Parks and Wildlife. Levels of allelic and gene diversity were average relative to values observed for marine and anadromous fishes. The set of genetic markers should be useful for a variety of studies, including moni- toring and assessment of red drum stock enhancement