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14 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ca(FeN)2 by Materials Project

Ca(FeN)2 crystallizes in the tetragonal P-4m2 space group. The structure is two-dimensional and consists of one Ca(FeN)2 sheet oriented in the (0, 0, 1) direction. Ca2+ is bonded to four equivalent N3- atoms to form distorted corner-sharing CaN4 tetrahedra. All Ca–N bond lengths are 2.46 Å. Fe2+ is bonded in a linear geometry to two equivalent N3- atoms. Both Fe–N bond lengths are 1.76 Å. N3- is bonded in a rectangular see-saw-like geometry to two equivalent Ca2+ and two equivalent Fe2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2026

AmeriFlux FLUXNET-1F CA-PB2 Polar Bear 2 - Fen

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site CA-PB2 Polar Bear 2 - Fen. This is the FLUXNET version of the carbon flux data for the site CA-PB2 Polar Bear 2 - Fen produced by applying the standard ONEFlux (1F) software. Site Description - Ontario Ministry of Environment and Climate Change's Environmental Monitoring and Reporting Branch has established five carbon flux monitoring towers in Ontario’s Far North as part of its Climate Change Modelling and Monitoring program. These long term monitoring stations measure carbon exchange and a suite of soil and meteorological parameters over peatland ecosystems to better understand carbon cycling in Ontario’s Far North. Information produced by these monitoring stations will assist the province in land use planning and the development of climate change adaptation strategies.

Humphreys, Elyn [Carleton University]↗
DOE OSTI2026

AmeriFlux FLUXNET-1F CA-CF2 Churchill Fen Site 2

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site CA-CF2 Churchill Fen Site 2. This is the FLUXNET version of the carbon flux data for the site CA-CF2 Churchill Fen Site 2 produced by applying the standard ONEFlux (1F) software. Site Description - Fen site dominated by sedges. Flat, high water table. Frozen for long periods each year. Close to Arctic Ocean coast so affected by land/sea breezes and coastal weather.

Tenuta, Mario [University of Manitoba]↗
DOE OSTI2025

AmeriFlux CA-PB2 Polar Bear 2 - Fen

This is the AmeriFlux version of the carbon flux data for the site CA-PB2 Polar Bear 2 - Fen. Site Description - Ontario Ministry of Environment and Climate Change's Environmental Monitoring and Reporting Branch has established five carbon flux monitoring towers in Ontario’s Far North as part of its Climate Change Modelling and Monitoring program. These long term monitoring stations measure carbon exchange and a suite of soil and meteorological parameters over peatland ecosystems to better understand carbon cycling in Ontario’s Far North. Information produced by these monitoring stations will assist the province in land use planning and the development of climate change adaptation strategies.

Humphreys, Elyn [Carleton University]↗
DOE OSTI2020

AmeriFlux CA-CF2 Churchill Fen Site 2

This is the AmeriFlux version of the carbon flux data for the site CA-CF2 Churchill Fen Site 2. Site Description - Fen site dominated by sedges. Flat, high water table. Frozen for long periods each year. Close to Arctic Ocean coast so affected by land/sea breezes and coastal weather.

Tenuta, Mario↗
DOE OSTI2024

AmeriFlux CA-Mer Ontario - Eastern Peatland, Mer Bleue

This is the AmeriFlux version of the carbon flux data for the site CA-Mer Ontario - Eastern Peatland, Mer Bleue. Site Description - The Mer Bleue peatland is primarily a large ombrotrophic bog located in the Ottawa River Valley, 10 km east of Ottawa, Ontario, Canada (45.40º N lat., 75.50º W long.). Mean annual temperature is 6.3ºC ranging from -10.5ºC in January to 21.0ºC in July. Mean annual precipitation is 943 mm, 268 mm of which falls during the summer months (Environment Canada; climate normals). Peat began to form approximately 8500 years ago, but the bog phase began later, about 6400 years ago (Lafleur et al., 2003; Richard, pers. comm.). The peat depth now ranges from 2 m at the edge to >5 m in the middle. Beaver ponds are found at the lagg margin of the bog. The bog is dominated by plant communities comprised primarily of the ericaceous shrubs Chamaedaphne calyculata (L.) Moench, Ledum groenlandicum Oeder, and Kalmia angustifolia L. Clusters of the deciduous shrub Vaccinium myrtilloides Michx. and the tufted sedge Eriophorum vaginatum L. are fairly common across the bog. The most common tree species found in the bog are Larix laricina (Duroi) K. Koch., Betula populifolia Marshall and Picea mariana (Miller) BSP occurring less frequently. In the poor fen, located to the north of the bog proper, community composition is primarily composed of the ericaceous shrubs listed above, including higher densities of K. angustifolia and Andromeda glaucophylla Link. The primary sedge in this area is Carex oligosperma Michx. All sites are dominated by an under story of bryophytes, mainly Sphagnum magellanicum Brid., Sphagnum capillifolium (Ehrh.) Hedw., and Polytrichum strictum Brid. in the bog, with Sphagnum papillosum Lindb., and Sphagnum fallax (Klinggr.) Klinggr. common in the wetter portions of the poor fen

Humphreys, Elyn↗
DOE OSTI2025

AmeriFlux FLUXNET-1F CA-Mer Ontario - Eastern Peatland, Mer Bleue

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site CA-Mer Ontario - Eastern Peatland, Mer Bleue. This is the FLUXNET version of the carbon flux data for the site CA-Mer Ontario - Eastern Peatland, Mer Bleue produced by applying the standard ONEFlux (1F) software. Site Description - The Mer Bleue peatland is primarily a large ombrotrophic bog located in the Ottawa River Valley, 10 km east of Ottawa, Ontario, Canada (45.40º N lat., 75.50º W long.). Mean annual temperature is 6.3ºC ranging from -10.5ºC in January to 21.0ºC in July. Mean annual precipitation is 943 mm, 268 mm of which falls during the summer months (Environment Canada; climate normals). Peat began to form approximately 8500 years ago, but the bog phase began later, about 6400 years ago (Lafleur et al., 2003; Richard, pers. comm.). The peat depth now ranges from 2 m at the edge to >5 m in the middle. Beaver ponds are found at the lagg margin of the bog. The bog is dominated by plant communities comprised primarily of the ericaceous shrubs Chamaedaphne calyculata (L.) Moench, Ledum groenlandicum Oeder, and Kalmia angustifolia L. Clusters of the deciduous shrub Vaccinium myrtilloides Michx. and the tufted sedge Eriophorum vaginatum L. are fairly common across the bog. The most common tree species found in the bog are Larix laricina (Duroi) K. Koch., Betula populifolia Marshall and Picea mariana (Miller) BSP occurring less frequently. In the poor fen, located to the north of the bog proper, community composition is primarily composed of the ericaceous shrubs listed above, including higher densities of K. angustifolia and Andromeda glaucophylla Link. The primary sedge in this area is Carex oligosperma Michx. All sites are dominated by an under story of bryophytes, mainly Sphagnum magellanicum Brid., Sphagnum capillifolium (Ehrh.) Hedw., and Polytrichum strictum Brid. in the bog, with Sphagnum papillosum Lindb., and Sphagnum fallax (Klinggr.) Klinggr. common in the wetter portions of the poor fen

Humphreys, Elyn [Carleton University]↗
DOE OSTI2025

On the Relationship Between Methane Production in Anaerobic Incubations of Peat Material and In Situ Methane Emissions

Anaerobic incubations of peat have been widely used to explore soil processes, but this in vitro technique raises many questions as to how well it reproduces in situ conditions. To investigate this, we conducted 60–100 days (+25 days pre‐incubation) anaerobic, temperature‐controlled incubation experiments across a temperature range of 1–26°C on samples from bog and fen habitats, at two different depths (9–19 and 25–35 cm). Here, we observed exponential increases in CO 2 and methane production with temperature in all conditions. We then compared field‐based measurements of methane emission with modeled expectations by extrapolating incubation‐determined methane production rates based on (a) soil temperature profiles, (b) the observed incubation temperature‐methane production relationship, and (c) seasonal thaw depth from each site. The resulting incubation‐extrapolated methane production agreed with measured emission rates within a factor of two at both sites and corresponded to 182 ± 54% and 59 ± 14% of the measured average yearly fluxes from the field for the bog and fen, respectively. The underestimation of fen methane fluxes may be due to the lack of living plant root‐derived dissolved organic carbon inputs in incubations, a key process in fens. Conversely, the overestimation in bogs could be attributed to methane oxidation in the field, which is absent in anaerobic incubation conditions. Nonetheless incubations predicted greenhouse gas emissions from a northern peatland within a factor of two.

Biological and medical sciences,Geosciences,Enviro↗
DOE OSTI2025

Key Environmental and Ecological Variables of Wetland CH 4 and CO 2 Fluxes Change With Warming

Wetlands are important ecosystems for the global carbon cycle, impacting regional and global methane (CH 4 ) and carbon dioxide (CO 2 ) budgets. This study examines how environmental and ecological variables impact wetland CH 4 flux and net ecosystem exchange of CO 2 (NEE) across 17 sites globally. We also quantified the importance of variables for each wetland type and site at monthly scale under normal and warm temperatures using dominance analysis. We identified soil and air temperature (TS, TA, respectively) as key variables influencing wetland CH4, and latent heat (LE) and shortwave radiation (SW) for NEE under normal and warm conditions. However, the importance of some variables shifted with warming. For predicting the variability of wetland CH4 flux under warming, gross primary productivity (GPP) and LE, replacing wind direction (WD), were dominant variables for tropical swamps, while NEE was important for high-latitude fens and bogs under warm temperatures. For wetland NEE, the role of TA and TS decreased across all wetland types with warming, while vapor pressure deficit (VPD) became more important for mid and high-latitude wetlands. Our results reveal the complex responses of wetland carbon flux to environmental and ecological variables with warming and provide new insights into improving wetland models by incorporating additional variables and accounting for the changing roles of variables in carbon flux under warming.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Advancements and opportunities to improve bottom–up estimates of global wetland methane emissions

Wetlands are the single largest natural source of atmospheric methane (CH 4 ), contributing approximately 30% of total surface CH 4 emissions, and they have been identified as the largest source of uncertainty in the global CH 4 budget based on the most recent Global Carbon Project CH 4 report. High uncertainties in the bottom–up estimates of wetland CH 4 emissions pose significant challenges for accurately understanding their spatiotemporal variations, and for the scientific community to monitor wetland CH 4 emissions from space. In fact, there are large disagreements between bottom–up estimates versus top–down estimates inferred from inversion of atmospheric CH 4 concentrations. To address these critical gaps, we review recent development, validation, and applications of bottom–up estimates of global wetland CH 4 emissions, as well as how they are used in top–down inversions. These bottom–up estimates, using (1) empirical biogeochemical modeling (e.g. WetCHARTs: 125–208 TgCH 4 yr -1 ); (2) process-based biogeochemical modeling (e.g. WETCHIMP: 190 ± 39 TgCH 4 yr -1 ); and (3) data-driven machine learning approach (e.g. UpCH4: 146 ± 43 TgCH 4 yr -1 ). Bottom–up estimates are subject to significant uncertainties (~80 Tg CH 4 yr -1 ), and the ranges of different estimates do not overlap, further amplifying the overall uncertainty when combining multiple data products. These substantial uncertainties highlight gaps in our understanding of wetland CH 4 biogeochemistry and wetland inundation dynamics. Major tropical and arctic wetland complexes are regional hotspots of CH 4 emissions. However, the scarcity of satellite data over the tropics and northern high latitudes offer limited information for top–down inversions to improve bottom–up estimates. Recent advances in surface measurements of CH 4 fluxes (e.g. FLUXNET-CH 4 ) across a wide range of ecosystems including bogs, fens, marshes, and forest swamps provide an unprecedented opportunity to improve existing bottom–up estimates of wetland CH 4 estimates. We suggest that continuous long-term surface measurements at representative wetlands, high fidelity wetland mapping, combined with an appropriate modeling framework, will be needed to significantly improve global estimates of wetland CH 4 emissions. There is also a pressing unmet need for fine-resolution and high-precision satellite CH 4 observations directed at wetlands.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Single crystal purification reduces trace impurities in halide perovskite precursors, alters perovskite thin film performance, and improves phase stability

Impurities present in commercially available halide perovskite precursors are known to affect photovoltaic performance. Here, we employ bulk single crystal growth of FAPbI 3 using solvent orthogonality induced crystallization (SONIC) to remove a broad set of extrinsic impurities from commercially available halide perovskite precursors, as verified by detailed chemical analysis. Following SONIC purification, FAPbI 3 films made from PbI 2 of originally low purity (99%) and high purity (99.99%) show improved phase purity and stability under light and heat relative to films made from raw precursors or precursors purified via retrograde powder crystallization (RPC) in 2-methoxyethanol, a method commonly utilized in recent reports of the highest-efficiency perovskite solar cells. In conclusion, single-crystal purification of precursors improves film stability under operational stressors, and the large enhancements in material purity provide a cleaner slate for improved isolation of compositional and additive effects on perovskite phase stability.

14 SOLAR ENERGY↗
DOE OSTI2026

Balancing moisture and oxygen can match the crystallization dynamics of inert halide perovskite processing

Understanding crystallization in ambient environments is essential for scaling the fabrication of halide perovskite solar cells. Antisolvent-free perovskite deposition offers improved compatibility with high-throughput processing but introduces distinct crystallization dynamics relative to the more ubiquitous use of antisolvents in lab-scale perovskite fabrication. These dynamics are driven by interactions between solutes, solvent and the deposition environment. Using in situ wide-angle X-ray scattering during spin-coating and annealing, we demonstrate how relative humidity (RH) and oxygen, can be tuned to drive polytype evolution during ambient crystallization of formamidinium lead iodide to match that of inert synthesis and achieve comparable film and device quality. In an inert (N 2 ) environment, we find that perovskite films follow a well-established 2H → 3C phase transformation with a short period of coexistence of the 4H and 6H phase during heating. During crystallization in dry air (RH 0%), the added presence of oxygen leads to the dominance of 4H intermediate for an extended duration, establishing a 2H → 4H → 3C pathway. Introducing low humidity (RH 10%) suppresses the 4H phase to a short-lived intermediate above 100 °C, facilitating a more direct transition to the desired 3C phase and almost replicating the crystallization behavior observed under inert conditions. Interestingly, films crystallized under RH 10% show a lower onset temperature for the perovskite 3C phase than under N 2 . At higher humidity (RH 40%), the strong interaction of oxygen and moisture with iodoplumbates appears to stabilize higher order polytypes (4H and 6H). Devices fabricated under RH 10% achieve higher efficiency and enhanced stability compared to those produced under inert atmosphere. These findings provide mechanistic insight into crystallization pathways in different environments and provide a framework to transfer processes from inert to ambient conditions. The results highlight the critical role of controlled humidity in tuning antisolvent-free perovskite crystallization for scalable processing.

Hossain, Maimur [Univ. of California, San Diego, C↗
DOE OSTI2025

Tunturi virus isolates and metagenome-assembled viral genomes provide insights into the virome of Acidobacteriota in Arctic tundra soils

Arctic soils are climate-critical areas, where microorganisms play crucial roles in nutrient cycling processes. Acidobacteriota are phylogenetically and physiologically diverse bacteria that are abundant and active in Arctic tundra soils. Still, surprisingly little is known about acidobacterial viruses in general and those residing in the Arctic in particular. Here, we applied both culture-dependent and -independent methods to study the virome of Acidobacteriota in Arctic soils. Five virus isolates, Tunturi 1–5, were obtained from Arctic tundra soils, Kilpisjärvi, Finland (69°N), using Tunturiibacter spp. strains originating from the same area as hosts. The new virus isolates have tailed particles with podo- (Tunturi 1, 2, 3), sipho- (Tunturi 4), or myovirus-like (Tunturi 5) morphologies. The dsDNA genomes of the viral isolates are 63–98 kbp long, except Tunturi 5, which is a jumbo phage with a 309-kbp genome. Tunturi 1 and Tunturi 2 share 88% overall nucleotide identity, while the other three are not related to one another. For over half of the open reading frames in Tunturi genomes, no functions could be predicted. To further assess the Acidobacteriota-associated viral diversity in Kilpisjärvi soils, bulk metagenomes from the same soils were explored and a total of 1881 viral operational taxonomic units (vOTUs) were bioinformatically predicted. Almost all vOTUs (98%) were assigned to the class Caudoviricetes. For 125 vOTUs, including five (near-)complete ones, Acidobacteriota hosts were predicted. Acidobacteriota-linked vOTUs were abundant across sites, especially in fens. Terriglobia-associated proviruses were observed in Kilpisjärvi soils, being related to proviruses from distant soils and other biomes. Approximately genus- or higher-level similarities were found between the Tunturi viruses, Kilpisjärvi vOTUs, and other soil vOTUs, suggesting some shared groups of Acidobacteriota viruses across soils. This study provides acidobacterial virus isolates as laboratory models for future research and adds insights into the diversity of viral communities associated with Acidobacteriota in tundra soils. Predicted virus-host links and viral gene functions suggest various interactions between viruses and their host microorganisms. Largely unknown sequences in the isolates and metagenome-assembled viral genomes highlight a need for more extensive sampling of Arctic soils to better understand viral functions and contributions to ecosystem-wide cycling processes in the Arctic.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Nanoscale Strain and Octahedral Tilting Removes Structural and Nonradiative Defects in 2D-Templated FAPbI 3

The halide perovskite formamidinium lead iodide (FAPbI 3 ) is a prime candidate for photovoltaics due to its excellent optoelectronic properties, but its application has been limited due to its structural instability. The large size of the FA cation results in metastability of the photoactive cubic phase and a facile degradation into thermodynamically stable hexagonal phases at room temperature. Recently, the incorporation of two-dimensional (2D) Ruddlesden-Popper halide perovskite seeds into a FAPbI 3 precursor solution was shown to template the growth of and stabilize cubic FAPbI 3 . Here, in this study, we investigate the nanoscale structural and optoelectronic mechanisms behind the observed bulk stabilization using synchrotron-based X-ray microscopies. Nanoprobe X-ray diffraction reveals 2D-templated FAPbI 3 films exhibit an average compressive strain normal to the substrate of -3.3%, 2-fold larger than that of MACl-stabilized FAPbI 3 . This compression creates locally templated regions composed of tetragonal-phase FAPbI 3 distributed nonuniformly throughout the film with fewer crystalline defects than purely cubic regions. Scanning X-ray excited optical luminescence (X-ray analog of photoluminescence) reveals that this local templating results in increased radiative recombination and red-shifted band edge and emission. Our results provide insight into the microscopic mechanism for the phase stabilization of FAPbI 3 using 2D perovskites as templates.

X-ray diffraction↗