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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Martian Cryogenic Carbonate Formation: Stable Isotope Variations Observed in Laboratory Studies

The history of water on Mars is tied to the formation of carbonates through atmospheric CO2 and its control of the climate history of the planet. Carbonate mineral formation under modern martian atmospheric conditions could be a critical factor in controlling the martian climate in a means similar to the rock weathering cycle on Earth. The combination of evidence for liquid water on the martian surface and cold surface conditions suggest fluid freezing could be very common on the surface of Mars. Cryogenic calcite forms easily from freezing solutions when carbon dioxide degasses quickly from Ca-bicarbonate-rich water, a process that has been observed in some terrestrial settings such as arctic permafrost cave deposits, lake beds of the Dry Valleys of Antarctica, and in aufeis (river icings) from rivers of N.E. Alaska. A series of laboratory experiments were conducted that simulated cryogenic carbonate formation on Mars in order to understand their isotopic systematics. The results indicate that carbonates grown under martian conditions show variable enrichments from starting bicarbonate fluids in both carbon and oxygen isotopes beyond equilibrium values.

Socki, Richard A.↗
NASA NTRS2017

Utilizing Stable Isotopes and Isotopic Anomalies to Study Early Solar System Formation Processes

Chondritic meteorites contain a diversity of particle components, i.e., chondrules and calcium-, aluminum-rich refractory inclusions (CAIs), that have survived since the formation of the Solar System. The chemical and isotopic compositions of these materials provide a record of the conditions present in the protoplanetary disk where they formed and can aid our understanding of the processes and reservoirs in which solids formed in the solar nebula, an important step leading to the accretion of planetesimals. Isotopic anomalies associated with nucleosynthetic processes are observed in these discrete materials, and can be compared to astronomical observations and astrophysical formation models of stars and more recently proplyds. The existence and size of these isotopic anomalies are typically thought to reflect a significant state of isotopic heterogeneity in the earliest Solar System, likely left over from molecular cloud heterogeneities on the grain scale, but some could also be due to late stellar injection. The homogenization of these isotopic anomalies towards planetary values can be used to track the efficiency and timescales of disk wide mixing,

Simon, Justin↗
DOE OSTI2020

Conifer water use patterns in the East River Watershed, Colorado US, based on stable water isotopes and cellulose isotopes

This data package contains a series of datasets aimed at understanding the seasonal origins of water used by the dominant conifer species, Abies lasiocarpa and Picea engelmannii, in the East River Watershed. There is a distinct difference in the stable isotopic ratio of summer rain and snowpack and thus by tracking the isotopic ratio of the xylem water in trees, it is possible to separate when a tree is using snow vs. summer rain. Following typical protocols, we sampled and extracted water from soils in the "Research Meadow" near Gothic, CO within the East River Watershed through the 2016 growing season. The stable isotopic ratio of these waters were then measured. Using values of the isotopic ratio of precipitation and snowpack from that season, we develop a mixing model to show how the trees transitioned from use of snowpack to summer in late July. We extended the information on the seasonal origins of water from 2016 back until 1980 by using measurements of the isotopic ratio of cellulose from trees in the Research Meadow. The isotopic ratio of tree ring cellulose records a signal both of the Vapor Pressure Deficit at the leaf-atmosphere boundary and also the source water for the trees. We concluded from this extended analysis that the trees underwent transitions between periods where snow was the dominant water source and summer rain was the dominant water source. More details on this analysis can be found in the publication: Persistence and Plasticity in Conifer Water Use Strategies. JGR Biogeoscience. DOI 10.1029/2018JG004845. The dataset specifically includes stable isotope measurements of xylem and soil water for Spruce and Fir trees at the Rocky Mountain Biological Lab's Research Meadow as well as snowpack and precipitation stable isotopes from nearby National Atmospheric Deposition Program sites. Associated meteorological data is included, which is needed to understand the source water for the trees based on the cellulose measurements.This dataset was updated in June 2021 also include intra-ring measurements of the d18O and d13C of cellulose these same species of trees at the Ziegler Reservoir site in Snowmass, CO. These are listed as files: "Interglaciald18OCellulose.csv", "Interglaciald13OCellulose.csv" and "Modernd13CCellulose.csv". The intent of these measurements was to assess whether common conifers (abies and picea) had undergone ecophysiological or ecohydrological changes during the last period in Earth's history was warmer than today, i.e. the last Interglacial (116,000 to 130,000 years ago). This site was chosen because it is a location where subfossil wood from this critical warm period was discovered. We measured the d18O and d13C of the subfossil trees following the same protocol as the modern samples which included chemical extraction of cellulose and isotope ratio mass spectrometry. We found that the trees showed little difference in water use efficiency but utilized more summer rain during the interglacial period. This analysis and detailed methods are provided in the following manuscript: Wetter summers mitigated temperature stress on Rocky Mountain forests during the last interglacial warm period which is in revision at GRL but is available as a preprint here: 10.1002/essoar.10506740.2

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Quantitative Determination of Biomass-derived Renewable Carbon in Fuels from Coprocessing of Bio-oils in Refinery Using a Stable Carbon Isotopic Approach

Increasing renewable carbon incorporation into conventional fuels through coprocessing with vacuum gas oil (VGO, a petroleum refining feedstock) is a critical step in biofuels development, scaling-up, adoption and associated GHG reduction. Optimization of the co-processing parameters maximizes incorporation of the renewable carbon in the fuel products. Quantitative determination of the renewable carbon content in the co-processed products provides direct evaluation of the parameters. The co-processing bio-oil with VGO through hydrocracking (HC) or fluid catalytic cracking (FCC) system resulted in carbon isotopic fractionation that prevented the direct use of the isotope mixing model for quantifying the renewable carbon. Here, we report an algorithm of using a stable carbon isotope approach to quantify the renewable carbon content in co-processing biofuel products through high-precision ?13C analysis. A controlled experiment carried out by blending a fossil diesel (-29.013‰) with a bio-diesel (-30.099‰) at various blending levels up to 98.0/2.0 wt% is presented and has demonstrated the applicability of this approach. The carbon isotope fractionation factors for the bio-oil co-processing were obtained by using a 14C-derived isotope-mixing model. The ?13C method was tested by co-processing 13C-labeled bio-crude and natural woody biomass-derived fast pyrolysis (FP) and catalytic fast pyrolysis (CFP) bio-oils with VGO. The results were verified by 14C accelerator mass spectrometry (AMS) method (ASTM-D6866) and compared with the yield mass balance (YMB) method. Strong agreement between d13C and 14C AMS methods demonstrated the applicability of the ?13C method to quantify renewable carbon content in co-processing fuel products and guide the co-processing optimization

Li, Zhenghua↗
NASA NTRS1996

Stable light isotope biogeochemistry of hydrothermal systems

The stable isotopic composition of the elements O, H, S and C in minerals and other chemical species can indicate the existence, extent, conditions and the processes (including biological activity) of hydrothermal systems. Hydrothermal alteration of the 18O/16O and D/H values of minerals can be used to detect fossil systems and delineate their areal extent. Water-rock interactions create isotopic signatures which indicate fluid composition, temperature, water-rock ratios, etc. The 18O/16O values of silica and carbonate deposits tend to increase with declining temperature and thus help to map thermal gradients. Measurements of D/H values can help to decipher the origin(s) of hydrothermal fluids. The 34S/32S and 13C/12C values of fluids and minerals reflect the origin of the S and C as well as oxygen fugacities and key redox processes. For example, a wide range of 34S/32S values which are consistent with equilibration below 100 degrees C between sulfide and sulfate can be attributed to sulfur metabolizing bacteria. Depending on its magnitude, the difference in the 13C/12C value of CO2 and carbonates versus organic carbon might be attributed either to equilibrium at hydrothermal temperatures or, if the difference exceeds 1% (10/1000), to organic biosynthesis. Along the thermal gradients of thermal spring outflows, the 13C/12C value of carbonates and 13C-depleted microbial organic carbon increases, principally due to the outgassing of relatively 13C-depleted CO2.

Review, Tutorial↗
DOE OSTI2026

Stable Water Isotope Data for the East River Watershed, Colorado (2014-2025)

The stable water isotope data for the East River Watershed, Colorado, consists of delta2H (hydrogen) and delta18O (oxygen) values from samples collected at multiple, long-term monitoring sites including streams, groundwater wells, springs, and a precipitation collector used to establish a local meteoric water line (LMWL) for the watershed. These locations represent important and/or unique end-member locations for which stable isotope values can be diagnostic of the connection between precipitation inputs as snow and rain and riverine export. Such locations include drainages underline entirely or largely by shale bedrock, land covered dominated by conifers, aspens, or meadows, and drainages impacted by historic mining activity and the presence of naturally mineralized rock. Developing a long-term record of water isotope values from a diversity of environments is a critical component of quantifying the impacts of both climate change and discrete climate perturbations, such as drought, forest mortality, and wildfire, on water export. Such data may be combined with stream gaging stations co-located at each surface water monitoring site to relate seasonal variations in water export to their stable isotopic signature. Data for liquid water delta2H and delta18O values are reported in units of parts per thousand (per-mil; ‰). This data package contains (1) a zip file (isotope_data_2014-2025.zip) containing a total of 95 files: 96 data files of isotope data from across the Lawrence Berkeley National Laboratory (LBNL) Watershed Function Scientific Focus Area (SFA) which is reported in .csv files per location and a locations.csv (1 file) with latitude and longitude for each location; (2) a file-level metadata (v6_20260901_flmd.csv) file that lists each file contained in the dataset with associated metadata; and (3) a data dictionary (v6_20260901_dd.csv) file that contains terms/column_headers used throughout the files along with a definition, units, and data type. Missing values within the anion data files are noted as either "-9999" or "0.0" for not detectable (N.D.) data. There are a total of 43 locations containing isotope data. Update on 2022-06-10: versioned updates to this dataset was made along with these changes: (1) updated isotope data for all locations up to 2021-12-31 and (2) the addition of the file-level metadata (flmd.csv) and data dictionary (dd.csv) were added to comply with the File-Level Metadata Reporting Format. Update on 2022-09-09: Updates were made to reporting format specific files (file-level metadata and data dictionary) to correct swapped file names, add additional details on metadata descriptions on both files, add a header_row column to enable parsing, and add version number and date to file names (v2_20220909_flmd.csv and v2_20220909_dd.csv). Update on 2023-08-08: Updates were made to both the data files and reporting format specific files. New available anion data was added, up until 2023-03-13. The file level metadata and data dictionary files were updated to reflect the additional data added. Update on 2024-03-11: Updates were made to both the data files and reporting format specific files. New available anion data was added, up until 2024-02-19. Further, revisions to the data files were made to remove incorrect data points (from 1970 and 2001). The reporting format specific files were updated to reflect the additional data added. Update on 2025-05-15: Updates were made to both the data files and reporting format specific files. New available isotope data was added, up until the end of WY2024 (September 30, 2024). International Generic Sample Numbers (IGSNs), when registered, were added to the data files. The reporting format specific files were updated to reflect the additional data added. Update on 2026-09-01: Updates were made to both the data files and reporting format specific files. New available isotope data was added, up until the end of WY2025 (September 30, 2025).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Model files for estimating snow dynamics and stable water isotopes across the East River, CO.

A coupled hydrologic and snowpack stable water isotope model is used to assesses controls on isotopic inputs across the East River, Colorado, a large, mountainous basin. The hydrologic model uses the semi-empirical, spatially distributed and publicly available U.S. Geological Survey numerical code Precipitation-Modelling Runoff System (PRMS). Water and energy are tracked daily through the atmosphere, canopy and subsurface at a 100-m grid resolution. The isotope mass balance model follows previous work by Ala-aho et al. (2017) to track stable isotopes entering the soil system as snowmelt or rain. Water stores and fluxes needed for the isotope model use hydrologic model output for each timestep and model modeled grid location. This data package provides all files related to the hydrologic model (executable, input and output files), the isotopic model calibration and the historic isotopic model (water years 2015-2020). The isotope model source code and executable are provided. The file "readme.txt" includes information on the file structure, steps to run the model, and description of included folders.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Ecological Traits of Fish for Mercury Biomonitoring: Insights from Compound-Specific Nitrogen and Stable Mercury Isotopes

Here we coupled compound-specific isotopic analyses of nitrogen (N) in amino acids (δ 15 N Glu , δ 15 N Phe ) and mercury stable isotopes (δ 202 Hg, Δ 199 Hg) to quantify ecological traits governing the concentration, variability, and source of Hg in largemouth bass (LB) and pike gudgeon (PG) across four rivers, South Korea. PG displayed uniform Hg concentration (56–137 ng/g), trophic position (TP corrected ; 2.6–3.0, n = 9), and N isotopes in the source amino acid (δ 15 N Phe ; 7–13‰), consistent with their specialist feeding on benthic insects. LB showed wide ranges in Hg concentration (45–693 ng/g), TP corrected (2.8–3.8, n = 14), and δ 15 N Phe (1.3–16‰), reflecting their opportunistic feeding behavior. Hg sources assessed using Hg isotopes reveal low and uniform Δ 199 Hg in PG (0.20–0.49‰), similar to Δ 199 Hg reported in sediments. LB displayed site-specific δ 202 Hg (-0.61 to -0.04‰) and Δ 199 Hg (0.53–1.09‰). At the Yeongsan River, LB displayed elevated Δ 199 Hg and low δ 15 N Phe , consistent with Hg and N sourced from the atmosphere. LB at the Geum River displayed low Δ 199 Hg and high δ 15 N Phe , both similar to the isotope values of anthropogenic sources. Our results suggest that a specialist fish (PG) with consistent ecological traits and Hg concentration is an effective bioindicator species for Hg. When accounting for Hg sources, however, LB better captures site-specific Hg sources.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Use of Stable Mercury Isotopes to Assess Mercury and Methylmercury Transformation and Transport across Critical Interfaces from the Molecular to the Watershed Scale (Final Report)

This project titled “Use of Stable Mercury Isotopes to Assess Mercury and Methylmercury Transformation and Transport across Critical Interfaces from the Molecular to the Watershed Scale” represents a collaborative effort between the University of Michigan (Jason Demers, PI) and Oak Ridge National Laboratory (Scott Brooks, co-I). Much has been learned about mercury (Hg) cycling in stream ecosystems, and East Fork Poplar Creek (EFPC) in particular, through decades of previous research. Nevertheless, some of the most fundamental questions regarding the sources of bioavailable Hg and its transformation to toxic methylmercury (MeHg) have remained unanswered. These fundamental questions include: (1) what are the sources and biogeochemical processes that lead to the input of dissolved Hg to stream water across critical subsurface interfaces within stream ecosystems, and EFPC in particular? and (2) what are the sources and biogeochemical processes that control the production and fate of bioaccumulative MeHg within stream ecosystems, and in EFPC in particular? To address these fundamental questions, our project aimed to couple laboratory experiments and field observations, both utilizing natural abundance Hg stable isotope techniques, to identify the processes responsible for generating mobile, bioavailable dissolved Hg from recalcitrant legacy sources within critical subsurface zones (e.g., streambed hyporheic zone, riparian floodplain subsurface). We used the isotopic signature of this bioavailable dissolved Hg to track its mobilization across these critical interfaces in order to link diffuse subsurface sources of dissolved Hg with increases in surface water dissolved Hg flux measured at the watershed scale. Additionally, our research aimed to determine the isotopic composition of MeHg within these same critical subsurface zones. We directly assessed the isotopic composition of MeHg within biota in order to gain insight into which subsurface sources of inorganic Hg and toxic MeHg are available for bioaccumulation within the EFPC ecosystem. Net fluxes of dissolved Hg along the flow path of EFPC were shown to vary spatially and temporally. In the Upper EFPC, within the Y12 boundary, stream water flux of dissolved Hg consistently decreased between the outfall and the downstream boundary of Y12 (57% ± 29%, 1SD). Within the Upper EFPC, an assessment of Hg isotopic composition suggested that losses were strongly reaction-driven, although isotopic diagnostics did not conform to any known processes. Downstream of Y12, in the upper reach of the Lower EFPC, dissolved Hg fluxes tended to increase during the dormant season (net gain of 11-120%), and decrease during the growing season (net loss of 23% +/- 18%, 1SD). In the downstream-most reach of Lower EFPC, dissolved Hg fluxes increased by 12-108% in 9 out of 10 monthly assessments. Overall, diffuse fluxes from the non-Y12 watershed accounted for 34% (+/- 17%, 1SD) of all dissolved Hg exported during base flow. Within Lower EFPC, an assessment of Hg isotopic composition was consistent with the contribution of diffuse Hg inputs from high-concentration hotspots within riparian floodplains and streambed hyporheic pore water. To investigate remobilization of recalcitrant Hg from legacy sediment sources, we developed procedures that coupled isotopic analysis with sequential extractions of streambed sediment. We found that the proportion of weakly-bound Hg within EFPC streambed sediment was relatively small, but could still account for a large proportion of the annual flux of dissolved Hg from EFPC. These sequential extractions also showed that this weakly-bound Hg fraction could be replenished from the much larger fraction of recalcitrant Hg in sediment. The isotopic composition of these weakly-bound and remobilized recalcitrant Hg fractions within the sediment was consistent with high-concentration dissolved Hg hotspots within hyporheic pore water. Thus, this research provided novel evidence that legacy mercury sources within streambed sediment could provide an ongoing contribution of dissolved Hg to surface waters. Finally, we developed new methods for the direct determination of the MeHg isotopic composition of organisms, which allowed a more direct evaluation of inorganic Hg and MeHg sources accumulating in the food web. We found that fish and aquatic invertebrates in both EFPC and a regional background site obtained inorganic Hg and MeHg from multiple isotopically distinct sources, including sediment, suspended particulates, and periphyton. Photodemethylation was found to be an important reaction influencing MeHg dynamics at both sites. However, the balance of microbial methylation and demethylation processes differed between the two streams, with fractionation resulting from methylation and demethylation processes being relatively in balance within the regional background site, whereas microbial methylation appeared to be dominant over microbial demethylation within the EFPC ecosystem. Broadly, the application of Hg isotopic analysis in this study led to numerous novel insights regarding the biogeochemical cycling of Hg in stream ecosystems. This research project promoted the development of two new approaches, including the coupling of sequential extractions with Hg isotopic analysis to assess remobilization of recalcitrant Hg within sediments, and a new method for the isotopic analysis of MeHg isolated from environmental samples. Both of these efforts represent advances in capacity for the field of mercury isotopic analysis and environmental assessment. Overall, this study demonstrates that the application of Hg stable isotope techniques continues to provide new insights into the biogeochemical cycling of Hg in complex aquatic environments, both within the EFPC and beyond.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Capillary absorption spectroscopy for high temporal resolution measurements of stable carbon isotopes in soil and plant-based systems

Capillary Absorption Spectroscopy (CAS) is a relatively new analytical technique for performing stable isotope analysis. Here, we demonstrate the utility of CAS by recording and quantifying variation in 13C in controlled and biologically relevant applications. We calibrated CAS system response to increased 13CO2, with an observed ~4‰ increase in measured Δ13C for each 0.03 ppm shift in 13CO2 concentration. We leveraged this calibration to quantify rates of biogeochemical processes using a 13C tracer. For example, we monitored microbial respiration of 13C-glucose within an agricultural soil at 10 s quantification intervals and results demonstrated 8.6% ± 0.4 of added glucose was converted to 13CO2 within 1.5 h of incubation. We expanded the demonstration by adapting a rhizobox to permit continuous monitoring of 13CO2 in a soil (as distinct from plant) headspace to track the timing and quantify respiration rates of fresh plant photosynthate and observed a 3.5 h delay between plant exposure to a13CO2 tracer and the first signs of respiration by soil biota. These experiments highlight CAS is effective in producing high temporal resolution quantification of 13CO2 and demonstrate potential applications.

13CO2↗
DOE OSTI2022

Stable carbon isotope values of syndepositional carbonate spherules and micrite record spatial and temporal changes in photosynthesis intensity

Marine and lacustrine carbonate minerals preserve carbon cycle information, and their stable carbon isotope values (δ 13 C) are frequently used to infer and reconstruct paleoenvironmental changes. However, multiple processes can influence the δ 13 C values of bulk carbonates, confounding the interpretation of these values in terms of conditions at the time of mineral precipitation. Co-existing carbonate forms may represent different environmental conditions, yet few studies have analyzed δ 13 C values of syndepositional carbonate grains of varying morphologies to investigate their origins. Here, we combine stable isotope analyses, metagenomics, and geochemical modeling to interpret δ 13 C values of syndepositional carbonate spherules (>500 μm) and fine-grained micrite (<63 μm) from a ~1600-year-long sediment record of a hypersaline lake located on the coral atoll of Kiritimati, Republic of Kiribati (1.9°N, 157.4°W). Petrographic, mineralogic, and stable isotope results suggest that both carbonate fractions precipitate in situ with minor diagenetic alterations. The δ 13 C values of spherules are high compared to the syndepositional micrite and cannot be explained by mineral differences or external perturbations, suggesting a role for local biological processes. We use geochemical modeling to test the hypothesis that the spherules form in the surface microbial mat during peak diurnal photosynthesis when the δ 13 C value of dissolved inorganic carbon is elevated. In contrast, we hypothesize that the micrite may precipitate more continuously in the water as well as in sub-surface, heterotrophic layers of the microbial mat. Both metagenome and geochemical model results support a critical role for photosynthesis in influencing carbonate δ 13 C values. The down-core spherule–micrite offset in δ 13 C values also aligns with total organic carbon values, suggesting that the difference in the δ13C values of spherules and micrite may be a more robust, inorganic indicator of variability in productivity and local biological processes through time than the δ 13 C values of individual carbonate forms.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

East River Watershed Stable Water Isotope Data in Precipitation, Snowpack and Snowmelt 2016-2020

Stable water isotopes (d18O, d2H and d-excess) are important tracers in hydrologic research to understand water partitioning between vegetation, groundwater, and runoff but are rarely applied to large watersheds with persistent snowpack and complex topopgraphy. Data were collected for the Lawrence Berkeley National Laboratory Watershed Function Science Focus Area supported by the U.S Department of Energy in the East River, CO Hydrologic Unit Code (140200010) with limited data also collected in adjacent watersheds Ohio Creek and Taylor River. Data are provided in csv and includes isotopic information for precipitation (years 2014-2016), snowmelt (years 2016-2017) and snowpits (years 2016-2020). Snowpit data contain depth resolved information at 10 cm intervals for density, snow water equivalent (SWE) and stable water isotopes. Bulk isotopic data for 86 snowpits contain depth, SWE, density and SWE-weighted isotope values. Sampling locations and elevations are provided within the data files, while kmz files are provided to view sampling locations using Google Earth software.

54 ENVIRONMENTAL SCIENCES↗