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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Wet-chemical etching of FIB lift-out TEM lamellae for damage-free analysis of 3-D nanostructures

Reducing ion beam damage from the focused ion beam (FIB) during fabrication of cross sections is a well-known challenge for materials characterization, especially cross sectional characterization of nanostructures. To address this, a new method has been developed for cross section fabrication enabling high resolution transmission electron microscopy (TEM) analysis of 3-D nanostructures free of surrounding material and free of damage detectable by TEM analysis. Before FIB processing, nanopillars are encapsulated in a sacrificial oxide which acts as a protective layer during FIB milling. Furthermore, the cross sectional TEM lamella containing the nanopillars is then mounted and thinned with some modifications to conventional FIB sample preparation that provide stability for the lamella during the following wet-chemical dip etch. The wet-chemical etch of the TEM lamella removes the sacrificial oxide layer, freeing the nanopillars from any material that would obscure TEM imaging. Both high resolution TEM and aberration corrected scanning TEM images of Si/SiGe pillars with diameters down to 30 nm demonstrate the successful application of this approach.

3-d nanostructure analysis↗
NASA NTRS2004

A Novel Biomedical Device Utilizing Light Emitting Nano-Structures

This paper will discuss the development of a novel biomedical detection device that will be used to detect microorganisms with the use of infrared fluorochrome polymers attached to antibodies in fluids such as water. The fluorochrome polymers emit light in the near inferred region (NIR), approximately 805 nm, when excited by an NIR laser at 778 nm. The device could remarkably change the way laboratory testing is done today. The testing process is usually performed on a time scale of days while our device will be able to detect microorganisms in minutes. This type of time efficient analysis is ideal for use aboard the International Space Station and the Space Shuttle (ISS/SS) and has many useful commercial applications, for instance at a water treatment plant and food processing plants. With more research and experimentation the testing might also one day be used to detect bacteria and viruses in complex fluids such as blood, which would revolutionize blood analysis as it is performed today. My contribution to the project has been to develop a process which will allow an antibody/fluorescent dye pair to be conjugated to a specific bacteria or virus and than to to be separated from a sample body of water for detection. The antibody being used in this experiment is anti beta galactosidase and its complement enzyme is beta galactosidase, a non harmful derivative of E. Coli. The anti beta galactosidase has been conjugated to the fluorochrome polymer, IRDye800, which emits at approximately 806 nm. The dye when excited by the NIR laser emits a signal which is detected by a spectrometer and then is read by state of the art computer software. The state-of-the-art process includes incubating the anti beta galactosidase and beta galactosidase in a phosphate buffer solution in a test tube, allowing the antibody to bind to specific sites on the enzyme. After the antibody is bound to the enzyme, it is centrifuged in specific filters that will allow free antibody to wash away and leave the antibody-enzyme complexes on top in solution for testing and analysis. This solution is pipetted into a cuvette, a special plastic test tube, which will then be excited by the laser. The signal read will tell US that an antibody is present and since it is bound to the enzyme, that the bacteria is also present.

Varaljay, Vanessa A.↗
DOE OSTI2023

Laser Driven Hydrothermal Processing (LDHP) for Rapid Dissolution of Glassy Nuclear Debris

Discovered in 2009 on the SLAB laser system at LLNL, Laser-Driven Hydrothermal Processing (LDHP) both spalls and transiently dissolves a wetted surface (e.g., rock, concrete, paint) when that surface is struck by a laser beam pulse under specific conditions. Previous projects have explored the application of LDHP to expediting sample dissolution for post-detonation nuclear forensics. Early results were very promising, indicating that this method could decrease material dissolution time by a factor of 10 or more. However, the large and complicated lasers previously used are impractical for this application. Under the R^3 venture we aimed to benchmark the LDHP capabilities of turn-key commercial off-the-shelf (COTS) lasers, and to establish how this process could be integrated into an analytical workflow for nuclear forensic analysis. We demonstrated that geological rock standards could be quickly processed into fine powder by LDHP followed by complete acid digestion in 15 minutes, without elemental fractionation that would skew analytical results. We determined that the COTS laser can be used for LDHP that could potentially reduce dissolution time for solid nuclear debris samples in post detonation nuclear forensics. One downside to this approach, however, is that the laser interactions are different with every material, so extensive method validation would be required for all likely material compositions. The LDHP processing rates of several materials were tested and determined to be favorable in the beginning with significant slowdown due to particulate scattering. This could be mitigated either by stopping and centrifuging the sample at specific intervals, or through design of a continuous solvent flow through mechanism.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Evaluation of Digital Image Recognition Methods for Mass Spectrometry Imaging Data Analysis

Analyzing mass spectrometry imaging data can be laborious and time consuming, and as the size and complexity of datasets grow, so does the need for robust automated processing methods. We here present a method for comprehensive, semi-targeted discovery of molecular distributions of interest from mass spectrometry imaging data, using widely available image similarity scoring algorithms to rank images by spatial correlation. A fast and powerful batch search method using a MATLAB implementation of structural similarity (SSIM) index scoring with a pre-selected reference distribution is demonstrated for two sample imaging datasets, a plant metabolite study using Artemisia annua leaf, and a drug distribution study using maraviroc-dosed macaque tissue. .

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

Summary Report for the Evaluation of Current QA Processes Within the FRMAC FAL and EPA MERL.

The Federal Radiological Monitoring and Assessment Center (FRMAC) relies on accurate and defensible analytical laboratory data to support its mission. Therefore, FRMAC must ensure that the environmental analytical laboratories providing analytical services maintain an ongoing capability to provide accurate analytical results to DOE. It is undeniable that the more Quality Assurance (QA) and Quality Control (QC) measures required of the laboratory, the less resources that are available for analysis of response samples. Being that QA and QC measures in general are understood to comprise a major effort related to a laboratory’s operations, requirements should only be considered if they are deemed “value-added” for the FRMAC mission. This report provides observations of areas for improvement and potential interoperability opportunities in the areas of Batch Quality Control Requirements, Written Communications, Data Review Processes, Data Reporting Processes, along with the lessons learned as they apply to items in the early phase of a response that will be critical for developing a more efficient, integrated response for future interactions between the FRMAC and EPA assets.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2015

The photocatalytic investigation of methylene blue dye with Cr doped zinc oxide nanoparticles

The present work reports eco-friendly and cost effective sol-gel technique for synthesis of Chromium doped ZnO nanoparticles at room temperature. In this process Zinc nitrate, Chromium nitrate were used as precursor. Structural as well as optical properties of Cr induced ZnO samples were analysed by X-ray diffraction technique (XRD), SEM, PL and UV-Visible spectroscopy (UV-Vis) respectively. XRD analysis shows that the samples have hexagonal (wurtzite) structure with no additional peak which suggests that Cr ions fit into the regular Zn sites of ZnO crystal structure. By using Scherrer’s formula for pure and Cr doped ZnO samples the average grain size was found to be 32 nm. Further band gap of pure and doped ZnO samples have been calculated by using UV-Vis spectra. The photo-catalytic degradation of methyl blue dye under UV irradiation was examined for synthesized samples. The results show that the concentration plays an important role in photo-catalytic activity.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Macquarie Island Cloud and Radiation Experiment (MICRE) Ice Nucleating Particle Measurements Field Campaign Report

The U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) user facility Macquarie Island Cloud and Radiation Experiment (MICRE) Ice Nucleating Particle Measurements campaign was aligned as a supplemental activity with the second year of the overall MICRE campaign. The purpose of the supplemental campaign was to provide a first-ever annual cycle of ice nucleating particle (INP) measurements at a Southern Ocean (SO) site, toward the investigation/characterization of sources of INPs in the marine boundary layer as being from the production or primary sea spray aerosol (SSA) emissions versus other long-range transport influences. Furthermore, measuring the variability in INPs seasonally in this region, as this may relate to meteorology and ocean biological processes, is expected to help constrain (via parameterizations) numerical model simulations of cloud phase and regional climate. In concert with other SO studies during the time frame of the campaign (March 2017 to March 2018), MICRE sought to evaluate the hypotheses that SSA INPs represent the major INP source in the SO and, due to their generally less efficient INP activation properties compared to terrestrial sources, that they may directly influence the persistence of supercooled clouds in a unique manner for this climatic region. These measurements supplemented the original deployment of primarily radiation measurements provided in the ARM MICRE request and the associated Australian Antarctic Division (AAD) Antarctic Clouds and Radiation Experiment (ACRE). Assistance and collaboration was obtained from the AAD, the Commonwealth Scientific and Industrial Research Organization (CSIRO) and the Australian Bureau of Meteorology (BOM). Follow-up plans will include investigations with their additional aerosol, cloud, and radiative transfer measurements. AAD also saw to the transport to Australia and storage of filters at the end of the campaign. The added effort involved an average of twice-weekly collections (a 48-hour and a 72-hour collection) of pre-sterilized, open-faced, polycarbonate filter samples for post-processing of INP number concentrations and tests to analyze the nature of INP sources. Collections were made by AAD technician Emry Thaggard Crocker after online training from our team. Images of the filter sampler and site are shown in Figure 1. Sampling occurred from an approximate elevation of 4m MSL. Filters were returned frozen to Colorado State University (CSU) at the end of the campaign. Initial processing to obtain INP temperature spectra (0 to -28°C) of the concentrations of INPs active via the immersion freezing mechanism were conducted using the CSU ice spectrometer (IS) instrument systems (Hiranuma et al. 2015; McCluskey et al. 2018). In this method, particles are first removed from filters using ultrapure water while under mechanical agitation. Arrays of the particle suspensions from a portion of filter rinses are then cooled to obtain immersion freezing data per volume of water, and finally are related to sampling volumes to obtain numbers per volume of air following the analysis methods of Vali (1971). A total of 103 filters were collected, including blanks at selected intervals throughout the project. For archival and completion of tasks under this ARM proposal, nearly half of the filter collections (46) were processed for basic temperature spectra, and half of these (23) were also tested for microbial/proteinaceous contributions toward INPs via 95°C pre-treatment of portions of the original suspensions.

Southern Ocean, aerosols, marine clouds, MARCUS ca↗
DOE OSTI2015

Crystallization processes in Ge{sub 2}Sb{sub 2}Se{sub 4}Te glass

Highlights: • Crystallization kinetics of Ge{sub 2}Sb{sub 2}Se{sub 4}Te glass was studied in dependence on particle size by DSC. • All studied fractions were described in terms of the SB autocatalytic model. • Relatively high amount of Te enhances manifestation of bulk crystallization mechanisms. • XRD analysis of samples crystallized under different conditions showed correlation with DSC data. • XRD analysis revealed a new crystallization mechanism indistinguishable by DSC. - Abstract: Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis were used to study crystallization in Ge{sub 2}Sb{sub 2}Se{sub 4}Te glass under non-isothermal conditions as a function of the particle size. The crystallization kinetics was described in terms of the autocatalytic Šesták–Berggren model. An extensive discussion of all aspects of a full-scale kinetic study of a crystallization process was undertaken. Dominance of the crystallization process originating from mechanically induced strains and heterogeneities was confirmed. Substitution of Se by Te was found to enhance the manifestation of the bulk crystallization mechanisms (at the expense of surface crystallization). The XRD analysis showed significant dependence of the crystalline structural parameters on the crystallization conditions (initial particle size of the glassy grains and applied heating rate). Based on this information, a new microstructural crystallization mechanism, indistinguishable by DSC, was proposed.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Nonadiabatic rate constants for proton transfer and proton-coupled electron transfer reactions in solution: Effects of quadratic term in the vibronic coupling expansion

Rate constant expressions for vibronically nonadiabatic proton transfer and proton-coupled electron transfer reactions are presented and analyzed. The regimes covered include electronically adiabatic and nonadiabatic reactions, as well as high-frequency and low-frequency proton donor-acceptor vibrational modes. These rate constants differ from previous rate constants derived with the cumulant expansion approach in that the logarithmic expansion of the vibronic coupling in terms of the proton donor-acceptor distance includes a quadratic as well as a linear term. The analysis illustrates that inclusion of this quadratic term in the framework of the cumulant expansion framework may significantly impact the rate constants at high temperatures for proton transfer interfaces with soft proton donor-acceptor modes that are associated with small force constants and weak hydrogen bonds. The effects of the quadratic term may also become significant in these regimes when using the vibronic coupling expansion in conjunction with a thermal averaging procedure for calculating the rate constant. In this case, however, the expansion of the coupling can be avoided entirely by calculating the couplings explicitly for the range of proton donor-acceptor distances sampled. The effects of the quadratic term for weak hydrogen-bonding systems are less significant for more physically realistic models that prevent the sampling of unphysical short proton donor-acceptor distances. Additionally, the rigorous relation between the cumulant expansion and thermal averaging approaches is clarified. In particular, the cumulant expansion rate constant includes effects from dynamical interference between the proton donor-acceptor and solvent motions and becomes equivalent to the thermally averaged rate constant when these dynamical effects are neglected. This analysis identifies the regimes in which each rate constant expression is valid and thus will be important for future applications to proton transfer and proton-coupled electron transfer in chemical and biological processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2007

Stardust Curation at Johnson Space Center: Photo Documentation and Sample Processing of Submicron Dust Samples from Comet Wild 2 for Meteoritics Science Community

Dust particles released from comet 81P/Wild-2 were captured in silica aerogel on-board the STARDUST spacecraft and successfully returned to the Earth on January 15, 2006. STARDUST recovered thousands of particles ranging in size from 1 to 100 micrometers. The analysis of these samples is complicated by the small total mass collected ( < 1mg), its entrainment in the aerogel collection medium, and the fact that the cometary dust is comprised of submicrometer minerals and carbonaceous material. During the six month Preliminary Examination period, 75 tracks were extracted from the aerogel cells , but only 25 cometary residues were comprehensively studied by an international consortium of 180 scientists who investigated their mineralogy/petrology, organic/inorganic chemistry, optical properties and isotopic compositions. These detailed studies were made possible by sophisticated sample preparation methods developed for the STARDUST mission and by recent major advances in the sensitivity and spatial resolution of analytical instruments.

Nakamura-Messenger, K.↗
DOE OSTI2013

Development of an Automated Remedy Performance Evaluation Program - 13622

Performance monitoring is a vital element of groundwater remediation. Unfortunately, the enormous efforts and costs that are expended procuring, managing, processing and storing monitoring data are often not subject to correspondingly rigorous evaluation. This is despite the fact that many steps in the process are predictable and are repeated many times over the remedy life cycle. At the Department of Energy (DOE) Hanford Site, a program is underway to automate many of these steps - processing, formatting any analyzing large volumes of heterogeneous data associated with the operation of several groundwater pump-and-treat (P and T) and in-situ remedies. The Automated Remedy Performance Evaluation Program (ARPEP) was developed from a work-flow process designed to deliver (a) monthly data summaries and preliminary analysis, (b) quarterly performance assessments, and (c) annual roll-up analyses that detect changes in long-term monitoring datasets and support remedy optimization. The intent of the ARPEP is to provide detailed, systematic and traceable data summaries, depictions and analyses that can be used by project scientists to complete their evaluation of remedy performance. The ARPEP work-flow was formalized following extensive review of applicable guidance, regulation and industry standards. The ARPEP incorporates disparate data types collected over different frequencies, such as water levels and pumping rates recorded every minute, and groundwater sample results obtained on quarterly, annual or irregular intervals. The data are processed, reduced to frequencies suitable for assessment, and combined in various ways leading to performance indicators such as (a) pumped well capacities and system downtime that reflect operational performance; (b) hydraulic gradients and areas of hydraulic containment that reflect hydraulic performance; and (c) time-series (longitudinal) and geo-statistical (spatial) trend analyses that reflect progress toward attainment of Remedial Action Objectives (RAOs). The entire sequence of data processing and analysis is undertaken within the R programming environment, an open-source environment for statistical computing and graphics, and is summarized in a comprehensive PDF project report. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

14 MeV Irradiation and Analysis of a 93% 239 Pu Target in Preparation for a F2019 FY22 Pu Campaign

In this work, we present the irradiation of a 93% 239 Pu with 14 MeV neutrons and subsequent analysis of the fission and activation products. The fully assembled target, a Pu metal bead encapsulated in Al, further encapsulated in welded stainless steel, was analyzed 22 times over more than 100 days using gamma emission analysis (GEA). Using the results from these analyses, R-values and fission yields for fission products were determined. To prepare for the FY22 Pu irradiation using the GODIVA critical assembly at NCERC, the irradiated Pu target was disassembled, dissolved, and separated using chemistry provided by LANL collaborators. This chemical separation was intended to remove the Pu from solution with little to no effect on the remaining elements. The chemistry was assessed to try to determine possible routes of fractionation of the sample and the fission products. The separation process used was successful for the bulk of the analyzed fission and activation products, as well as the added radiotracers. The final dissolved solution and separated fractions were analyzed by GEA looking at the remaining fission, activation and radiotracers and thermal ionization mass spectrometry analysis looking at the Pu isotopics.

14MeV↗
NASA NTRS1993

An extended laser flash technique for thermal diffusivity measurement of high-temperature materials

Knowledge of thermal diffusivity data for high-temperature materials (solids and liquids) is very important in analyzing a number of processes, among them solidification, crystal growth, and welding. However, reliable thermal diffusivity versus temperature data, particularly those for high-temperature liquids, are still far from complete. The main measurement difficulties are due to the presence of convection and the requirement for a container. Fortunately, the availability of levitation techniques has made it possible to solve the containment problem. Based on the feasibility of the levitation technology, a new laser flash technique which is applicable to both levitated liquid and solid samples is being developed. At this point, the analysis for solid samples is near completion and highlights of the technique are presented here. The levitated solid sample which is assumed to be a sphere is subjected to a very short burst of high power radiant energy. The temperature of the irradiated surface area is elevated and a transient heat transfer process takes place within the sample. This containerless process is a two-dimensional unsteady heat conduction problem. Due to the nonlinearity of the radiative plus convective boundary condition, an analytic solution cannot be obtained. Two options are available at this point. Firstly, the radiation boundary condition can be linearized, which then accommodates a closed-form analytic solution. Comparison of the analytic curves for the temperature rise at different points to the experimentally-measured values will then provide the thermal diffusivity values. Secondly, one may set up an inverse conduction problem whereby experimentally obtained surface temperature history is used as the boundary conditions. The thermal diffusivity can then be elevated by minimizing the difference between the real heat flux boundary condition (radiation plus convection) and the measurements. Status of an experimental study directed at measuring the thermal diffusivity of high-temperature solid samples of pure Nickel and Inconel 718 superalloys are presented. Preliminary measurements showing surface temperature histories are discussed.

Shen, F.↗
DOE OSTI2013

Using Comprehensive Two-Dimensional Gas Chromatography to the Explore the Geochemistry of the Santa Barbara Oil Seeps

The development of comprehensive two-dimensional gas chromatography (GC x GC) has expanded the analytical window for studying complex mixtures like oil. Compared to traditional gas chromatography, this technology separates and resolves at least an order of magnitude more compounds, has a much larger signal to noise ratio, and sorts compounds based on their chemical class; hence, providing highly refined inventories of petroleum hydrocarbons in geochemical samples that was previously unattainable. In addition to the increased resolution afforded by GC x GC, the resulting chromatograms have been used to estimate the liquid vapor pressures, aqueous solubilities, octanol-water partition coefficients, and vaporization enthalpies of petroleum hydrocarbons. With these relationships, powerful and incisive analyses of phase-transfer processes affecting petroleum hydrocarbon mixtures in the environment are available. For example, GC x GC retention data has been used to quantitatively deconvolve the effects of phase transfer processes such as water washing and evaporation. In short, the positive attributes of GC x GC-analysis have led to a methodology that has revolutionized the analysis of petroleum hydrocarbons. Overall, this research has opened numerous fields of study on the biogeochemical "genetics" (referred to as petroleomics) of petroleum samples in both subsurface and surface environments. Furthermore, these new findings have already been applied to the behavior of oil at other seeps as well, for petroleum exploration and oil spill studies.

02 PETROLEUM↗
DOE OSTI2018

Identification and Removal of Contaminant Sequences From Ribosomal Gene Databases: Lessons From the Census of Deep Life

Earth’s subsurface environment is one of the largest, yet least studied, biomes on Earth, and many questions remain regarding what microorganisms are indigenous to the subsurface. Through the activity of the Census of Deep Life (CoDL) and the Deep Carbon Observatory, an open access 16S ribosomal RNA gene sequence database from diverse subsurface environments has been compiled. However, due to low quantities of biomass in the deep subsurface, the potential for incorporation of contaminants from reagents used during sample collection, processing, and/or sequencing is high. Thus, to understand the ecology of subsurface microorganisms (i.e., the distribution, richness, or survival), it is necessary to minimize, identify, and remove contaminant sequences that will skew the relative abundances of all taxa in the sample. In this meta-analysis, we identify putative contaminants associated with the CoDL dataset, recommend best practices for removing contaminants from samples, and propose a series of best practices for subsurface microbiology sampling. The most abundant putative contaminant genera observed, independent of evenness across samples, were Propionibacterium, Aquabacterium, Ralstonia, and Acinetobacter. While the top five most frequently observed genera were Pseudomonas, Propionibacterium, Acinetobacter, Ralstonia, and Sphingomonas. The majority of the most frequently observed genera (high evenness) were associated with reagent or potential human contamination. Additionally, in DNA extraction blanks, we observed potential archaeal contaminants, including methanogens, which have not been discussed in previous contamination studies. Such contaminants would directly affect the interpretation of subsurface molecular studies, as methanogenesis is an important subsurface biogeochemical process. Utilizing previously identified contaminant genera, we found that ~27% of the total dataset were identified as contaminant sequences that likely originate from DNA extraction and DNA cleanup methods. Thus, controls must be taken at every step of the collection and processing procedure when working with low biomass environments such as, but not limited to, portions of Earth’s deep subsurface. Taken together, we stress that the CoDL dataset is an incredible resource for the broader research community interested in subsurface life, and steps to remove contamination derived sequences must be taken prior to using this dataset.

16S rRNA↗
NASA NTRS2022

Measurement report: Closure Analysis of Aerosol–cloud Composition in Tropical Maritime Warm Convection

Cloud droplet chemical composition is a key observable property that can aid understanding of how aerosols and clouds interact. As part of the Clouds, Aerosols and Monsoon Processes – Philippines Experiment (CAMP2Ex), three case studies were analyzed involving collocated airborne sampling of relevant clear and cloudy air masses associated with maritime warm convection. Two of the cases represented a polluted marine background, with signatures of transported East Asian regional pollution, aged over water for several days, while the third case comprised a major smoke transport event from Kalimantan fires. Sea salt was a dominant component of cloud droplet composition, in spite of fine particulate enhancement from regional anthropogenic sources. Furthermore, the proportion of sea salt was enhanced relative to sulfate in rainwater and may indicate both a propensity for sea salt to aid warm rain production and an increased collection efficiency of large sea salt particles by rain in subsaturated environments. Amongst cases, as precipitation became more significant, so too did the variability in the sea salt to (non-sea salt) sulfate ratio. Across cases, nitrate and ammonium were fractionally greater in cloud water than fine-mode aerosol particles; however, a strong covariability in cloud water nitrate and sea salt was suggestive of prior uptake of nitrate on large salt particles. A mass-based closure analysis of non-sea salt sulfate compared the cloud water air-equivalent mass concentration to the concentration of aerosol particles serving as cloud condensation nuclei for droplet activation. While sulfate found in cloud was generally constrained by the sub-cloud aerosol concentration, there was significant intra-cloud variability that was attributed to entrainment – causing evaporation of sulfate-containing droplets –and losses due to precipitation. In addition, precipitation tended to promote mesoscale variability in the sub-cloud aerosol through a combination of removal, convective downdrafts, and dynamically driven convergence. Physical mechanisms exerted such strong control over the cloud water compositional budget that it was not possible to isolate any signature of chemical production/loss using in-cloud observations. The cloud-free environment surrounding the non-precipitating smoke case indicated sulfate enhancement compared to convective mixing quantified by a stable gas tracer; however, this was not observed in the cloud water (either through use of ratios or the mass closure), perhaps implying that the warm convective cloud timescale was too short for chemical production to be a leading-order budgetary term and because precursors had already been predominantly exhausted. Closure of other species was truncated by incomplete characterization of coarse aerosol (e.g., it was found that only 10 %–50% of sea salt mass found in cloud was captured during clear-air sampling) and unmeasured gasphase abundances affecting closure of semi-volatile aerosol species (e.g., ammonium, nitrate and organic) and soluble volatile organic compound contributions to total organic carbon in cloud water.

Ewan Crosbie↗
DOE OSTI2023

Laser-Induced Fluorescence for Monitoring Environmental Contamination and Stress in the Moss Thuidium plicatile

The ability to detect, measure, and locate the source of contaminants, especially heavy metals and radionuclides, is of ongoing interest. A common tool for contaminant identification and bioremediation is vegetation that can accumulate and indicate recent and historic pollution. However, large-scale sampling can be costly and labor-intensive. Hence, non-invasive in-situ techniques such as laser-induced fluorescence (LIF) are becoming useful and effective ways to observe the health of plants through the excitation of organic molecules, e.g., chlorophyll. The technique presented utilizes images collected of LIF in moss to identify different metals and environmental stressors. Analysis through image processing of LIF response was key to identifying Cu, Zn, Pb, and a mixture of the metals at nmol/cm 2 levels. Specifically, the RGB values from each image were used to create density histograms of each color channel’s relative pixel abundance at each decimal code value. These histograms were then used to compare color shifts linked to the successful identification of contaminated moss samples. Photoperiod and extraneous environmental stressors had minimal impact on the histogram color shift compared to metals and presented with a response that differentiated them from metal contamination.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Boron adsorption in clay minerals: Implications for martian groundwater chemistry and boron on Mars

Boron has been detected on Mars in calcium-sulfate veins found within clay mineral rich rocks on Mars by the Mars Science Laboratory (MSL) Curiosity rover using Laser Induced Breakdown Spectroscopy (LIBS) analysis. Borates play a vital role in stabilizing ribose on Earth and has been suggested as a key requirement for life. Borate ions readily adsorb to phyllosilicate clay minerals. The discovery of boron on Mars in proximity to phyllosilicate-bearing bedrock may have strong implications for potential past prebiotic conditions on Mars. In this study we generated a suite of clay minerals with adsorbed borate, including both typical terrestrial clay minerals (montmorillonite) and Mars-analog clay minerals (nontronite, saponite, griffithite), to understand controls on borate adsorption and to analyze with LIBS to compare with MSL data. Clay minerals were subjected to mineralogical and chemical analysis before and after adsorption. Adsorption analysis revealed that the Mars analog clay minerals adsorbed less boron than terrestrial counterparts, but within comparable amounts to those detected on Mars and in meteorites. Post-adsorption analysis by X-ray diffraction (XRD) revealed slight changes in the interlayer spacing of many of the clay minerals. Based on the adsorption analysis of the Mars-analog clay minerals, phyllosilicate-bearing bedrock in Gale crater may contain up to 90-110 ppm B. A series of borate-enriched samples were created for analysis of LIBS spectra from ChemCam on the Curiosity rover and SuperCam on the Perseverance Rover. Finally, the results of this study may provide insight into martian groundwater geochemistry processes and the mobility of a key molecule connected with life.

58 GEOSCIENCES↗