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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on HgP2Xe5F22 by Materials Project

XeF2Hg(XeF2)4(PF6)2 crystallizes in the orthorhombic Pccn space group. The structure is zero-dimensional and consists of four Hg(XeF2)4 clusters, eight PF6 clusters, and four XeF2 clusters. In each Hg(XeF2)4 cluster, there are two inequivalent Xe sites. In the first Xe site, Xe is bonded in a linear geometry to two F atoms. There are one shorter (2.04 Å) and one longer (2.13 Å) Xe–F bond lengths. In the second Xe site, Xe is bonded in a linear geometry to two F atoms. There are one shorter (2.04 Å) and one longer (2.15 Å) Xe–F bond lengths. Hg is bonded in a 4-coordinate geometry to four F atoms. There are two shorter (2.30 Å) and two longer (2.36 Å) Hg–F bond lengths. There are four inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one Xe atom. In the second F site, F is bonded in a distorted bent 120 degrees geometry to one Xe and one Hg atom. In the third F site, F is bonded in a single-bond geometry to one Xe atom. In the fourth F site, F is bonded in a bent 150 degrees geometry to one Xe and one Hg atom. In each PF6 cluster, P is bonded in an octahedral geometry to six F atoms. There are a spread of P–F bond distances ranging from 1.63–1.67 Å. There are six inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one P atom. In the second F site, F is bonded in a single-bond geometry to one P atom. In the third F site, F is bonded in a single-bond geometry to one P atom. In the fourth F site, F is bonded in a single-bond geometry to one P atom. In the fifth F site, F is bonded in a single-bond geometry to one P atom. In the sixth F site, F is bonded in a single-bond geometry to one P atom. In each XeF2 cluster, Xe is bonded in a linear geometry to two equivalent F atoms. Both Xe–F bond lengths are 2.08 Å. F is bonded in a single-bond geometry to one Xe atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SmHg2 by Materials Project

SmHg2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Sm is bonded to twelve equivalent Hg atoms to form a mixture of edge and face-sharing SmHg12 cuboctahedra. All Sm–Hg bond lengths are 3.38 Å. Hg is bonded in a 9-coordinate geometry to six equivalent Sm and three equivalent Hg atoms. All Hg–Hg bond lengths are 2.87 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ag2Hg by Materials Project

Ag2Hg crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ag is bonded to nine equivalent Ag and three equivalent Hg atoms to form AgAg9Hg3 cuboctahedra that share corners with three equivalent HgAg6Hg6 cuboctahedra, corners with nine equivalent AgAg9Hg3 cuboctahedra, edges with nine equivalent HgAg6Hg6 cuboctahedra, edges with fifteen equivalent AgAg9Hg3 cuboctahedra, faces with six equivalent HgAg6Hg6 cuboctahedra, and faces with twelve equivalent AgAg9Hg3 cuboctahedra. There are three shorter (2.90 Å) and six longer (3.09 Å) Ag–Ag bond lengths. All Ag–Hg bond lengths are 3.06 Å. Hg is bonded to six equivalent Ag and six equivalent Hg atoms to form HgAg6Hg6 cuboctahedra that share corners with six equivalent AgAg9Hg3 cuboctahedra, corners with six equivalent HgAg6Hg6 cuboctahedra, edges with six equivalent HgAg6Hg6 cuboctahedra, edges with eighteen equivalent AgAg9Hg3 cuboctahedra, faces with six equivalent HgAg6Hg6 cuboctahedra, and faces with twelve equivalent AgAg9Hg3 cuboctahedra. All Hg–Hg bond lengths are 3.09 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CuHgSBr by Materials Project

CuHgSBr crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are two inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded to two equivalent S2- and two Br1- atoms to form CuS2Br2 trigonal pyramids that share corners with two equivalent HgS2Br4 octahedra, corners with two equivalent CuS2Br2 trigonal pyramids, edges with two equivalent HgS2Br4 octahedra, and an edgeedge with one CuS2Br2 trigonal pyramid. The corner-sharing octahedral tilt angles are 57°. Both Cu–S bond lengths are 2.25 Å. There are one shorter (2.44 Å) and one longer (3.15 Å) Cu–Br bond lengths. In the second Cu1+ site, Cu1+ is bonded to two equivalent S2- and two Br1- atoms to form CuS2Br2 trigonal pyramids that share corners with two equivalent HgS2Br4 octahedra, corners with two equivalent CuS2Br2 trigonal pyramids, edges with two equivalent HgS2Br4 octahedra, and an edgeedge with one CuS2Br2 trigonal pyramid. The corner-sharing octahedral tilt angles are 57°. Both Cu–S bond lengths are 2.25 Å. There are one shorter (2.45 Å) and one longer (3.07 Å) Cu–Br bond lengths. There are three inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded in a 4-coordinate geometry to two S2- and four Br1- atoms. Both Hg–S bond lengths are 2.44 Å. There are two shorter (3.18 Å) and two longer (3.62 Å) Hg–Br bond lengths. In the second Hg2+ site, Hg2+ is bonded to two equivalent S2- and four equivalent Br1- atoms to form distorted HgS2Br4 octahedra that share corners with four equivalent HgS2Br4 octahedra, corners with four equivalent CuS2Br2 trigonal pyramids, edges with four HgS2Br4 octahedra, and edges with four equivalent CuS2Br2 trigonal pyramids. The corner-sharing octahedral tilt angles are 13°. Both Hg–S bond lengths are 2.44 Å. All Hg–Br bond lengths are 3.28 Å. In the third Hg2+ site, Hg2+ is bonded to two equivalent S2- and four equivalent Br1- atoms to form distorted HgS2Br4 octahedra that share corners with four equivalent HgS2Br4 octahedra, corners with four equivalent CuS2Br2 trigonal pyramids, edges with four HgS2Br4 octahedra, and edges with four equivalent CuS2Br2 trigonal pyramids. The corner-sharing octahedral tilt angles are 13°. Both Hg–S bond lengths are 2.45 Å. All Hg–Br bond lengths are 3.28 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Cu1+ and two Hg2+ atoms to form corner-sharing SCu2Hg2 trigonal pyramids. In the second S2- site, S2- is bonded to two equivalent Cu1+ and two Hg2+ atoms to form corner-sharing SCu2Hg2 tetrahedra. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a 2-coordinate geometry to two Cu1+ and two equivalent Hg2+ atoms. In the second Br1- site, Br1- is bonded in a 8-coordinate geometry to two Cu1+ and six Hg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AgHg3 by Materials Project

AgHg3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ag is bonded to twelve equivalent Hg atoms to form AgHg12 cuboctahedra that share corners with twelve equivalent AgHg12 cuboctahedra, edges with twenty-four equivalent HgAg4Hg8 cuboctahedra, faces with six equivalent AgHg12 cuboctahedra, and faces with twelve equivalent HgAg4Hg8 cuboctahedra. All Ag–Hg bond lengths are 3.19 Å. Hg is bonded to four equivalent Ag and eight equivalent Hg atoms to form HgAg4Hg8 cuboctahedra that share corners with twelve equivalent HgAg4Hg8 cuboctahedra, edges with eight equivalent AgHg12 cuboctahedra, edges with sixteen equivalent HgAg4Hg8 cuboctahedra, faces with four equivalent AgHg12 cuboctahedra, and faces with fourteen equivalent HgAg4Hg8 cuboctahedra. All Hg–Hg bond lengths are 3.19 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VHg3 by Materials Project

VHg3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. V is bonded to twelve equivalent Hg atoms to form VHg12 cuboctahedra that share corners with six equivalent VHg12 cuboctahedra, corners with twelve equivalent HgV4Hg8 cuboctahedra, edges with eighteen equivalent HgV4Hg8 cuboctahedra, faces with eight equivalent VHg12 cuboctahedra, and faces with twelve equivalent HgV4Hg8 cuboctahedra. There are six shorter (3.03 Å) and six longer (3.14 Å) V–Hg bond lengths. Hg is bonded to four equivalent V and eight equivalent Hg atoms to form distorted HgV4Hg8 cuboctahedra that share corners with four equivalent VHg12 cuboctahedra, corners with fourteen equivalent HgV4Hg8 cuboctahedra, edges with six equivalent VHg12 cuboctahedra, edges with twelve equivalent HgV4Hg8 cuboctahedra, faces with four equivalent VHg12 cuboctahedra, and faces with sixteen equivalent HgV4Hg8 cuboctahedra. There are a spread of Hg–Hg bond distances ranging from 3.06–3.23 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GaHg3 by Materials Project

Hg3Ga crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Hg is bonded in a 12-coordinate geometry to eight equivalent Hg and four equivalent Ga atoms. There are a spread of Hg–Hg bond distances ranging from 3.27–3.37 Å. There are two shorter (3.25 Å) and two longer (3.32 Å) Hg–Ga bond lengths. Ga is bonded to twelve equivalent Hg atoms to form a mixture of distorted corner and face-sharing GaHg12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TbHg2 by Materials Project

TbHg2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Tb is bonded in a 10-coordinate geometry to ten equivalent Hg atoms. There are a spread of Tb–Hg bond distances ranging from 3.18–3.36 Å. Hg is bonded in a 8-coordinate geometry to five equivalent Tb and three equivalent Hg atoms. There are two shorter (3.01 Å) and one longer (3.18 Å) Hg–Hg bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hg3Rh by Materials Project

RhHg3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Rh is bonded to twelve equivalent Hg atoms to form RhHg12 cuboctahedra that share corners with six equivalent RhHg12 cuboctahedra, corners with twelve equivalent HgHg8Rh4 cuboctahedra, edges with eighteen equivalent HgHg8Rh4 cuboctahedra, faces with eight equivalent RhHg12 cuboctahedra, and faces with twelve equivalent HgHg8Rh4 cuboctahedra. There are six shorter (3.01 Å) and six longer (3.05 Å) Rh–Hg bond lengths. Hg is bonded to four equivalent Rh and eight equivalent Hg atoms to form distorted HgHg8Rh4 cuboctahedra that share corners with four equivalent RhHg12 cuboctahedra, corners with fourteen equivalent HgHg8Rh4 cuboctahedra, edges with six equivalent RhHg12 cuboctahedra, edges with twelve equivalent HgHg8Rh4 cuboctahedra, faces with four equivalent RhHg12 cuboctahedra, and faces with sixteen equivalent HgHg8Rh4 cuboctahedra. There are a spread of Hg–Hg bond distances ranging from 2.93–3.10 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeHg3 by Materials Project

FeHg3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Fe is bonded to twelve equivalent Hg atoms to form a mixture of face and corner-sharing FeHg12 cuboctahedra. There are six shorter (2.91 Å) and six longer (3.22 Å) Fe–Hg bond lengths. Hg is bonded in a 2-coordinate geometry to four equivalent Fe and six equivalent Hg atoms. There are four shorter (3.01 Å) and two longer (3.07 Å) Hg–Hg bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hg3Pd by Materials Project

PdHg3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Pd is bonded to twelve equivalent Hg atoms to form PdHg12 cuboctahedra that share corners with six equivalent PdHg12 cuboctahedra, corners with twelve equivalent HgHg8Pd4 cuboctahedra, edges with eighteen equivalent HgHg8Pd4 cuboctahedra, faces with eight equivalent PdHg12 cuboctahedra, and faces with twelve equivalent HgHg8Pd4 cuboctahedra. There are six shorter (2.97 Å) and six longer (3.23 Å) Pd–Hg bond lengths. Hg is bonded to four equivalent Pd and eight equivalent Hg atoms to form distorted HgHg8Pd4 cuboctahedra that share corners with four equivalent PdHg12 cuboctahedra, corners with fourteen equivalent HgHg8Pd4 cuboctahedra, edges with six equivalent PdHg12 cuboctahedra, edges with twelve equivalent HgHg8Pd4 cuboctahedra, faces with four equivalent PdHg12 cuboctahedra, and faces with sixteen equivalent HgHg8Pd4 cuboctahedra. There are a spread of Hg–Hg bond distances ranging from 2.93–3.25 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TbHg2 by Materials Project

TbHg2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Tb is bonded to twelve equivalent Hg atoms to form a mixture of distorted edge and face-sharing TbHg12 cuboctahedra. There are six shorter (3.33 Å) and six longer (3.38 Å) Tb–Hg bond lengths. Hg is bonded in a 9-coordinate geometry to six equivalent Tb and three equivalent Hg atoms. All Hg–Hg bond lengths are 2.87 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CrHg3 by Materials Project

CrHg3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Cr is bonded to twelve equivalent Hg atoms to form CrHg12 cuboctahedra that share corners with twelve equivalent CrHg12 cuboctahedra, edges with twenty-four equivalent HgCr4Hg8 cuboctahedra, faces with six equivalent CrHg12 cuboctahedra, and faces with twelve equivalent HgCr4Hg8 cuboctahedra. All Cr–Hg bond lengths are 3.14 Å. Hg is bonded to four equivalent Cr and eight equivalent Hg atoms to form HgCr4Hg8 cuboctahedra that share corners with twelve equivalent HgCr4Hg8 cuboctahedra, edges with eight equivalent CrHg12 cuboctahedra, edges with sixteen equivalent HgCr4Hg8 cuboctahedra, faces with four equivalent CrHg12 cuboctahedra, and faces with fourteen equivalent HgCr4Hg8 cuboctahedra. All Hg–Hg bond lengths are 3.14 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Multi-decadal trends in mercury and methylmercury concentrations in the brown watersnake (Nerodia taxispilota)

Mercury (Hg) is an environmental contaminant that poses a threat to aquatic systems globally. Temporal evaluations of Hg contamination have increased in recent years, with studies focusing on how anthropogenic activities impact Hg bioavailability in a variety of aquatic systems. While it is common for these studies and ecological risk assessments to evaluate Hg bioaccumulation and effects in wildlife, there is a paucity of information regarding Hg dynamics in reptiles. The goal of this study was to investigate temporal patterns in total mercury (THg) and methylmercury (MeHg) concentrations across a 36-year period, as well as evaluate relationships among and between destructive (kidney, liver, muscle) and non-destructive (blood, tail) tissue types in a common watersnake species. To accomplish this, we measured THg and MeHg concentrations in multiple tissues from brown watersnakes (Nerodia taxispilota) collected from Steel Creek on the Savannah River Site (SRS; Aiken, SC, USA) from two time periods (1983–1986 and 2019). We discovered significant and positive relationships between tail tips and destructive tissues. In both time periods, THg concentrations varied significantly by tissue type, and destructive tissues exhibited higher but predictable THg values relative to tail tissue. Methylmercury concentrations did not differ among tissues from the 1980s but was significantly higher in muscle compared to other tissues from snakes collected in 2019. Percent MeHg of THg in N. taxispilota tissues mirrored patterns reported in other reptiles, although the range of % MeHg in liver and kidney differed between time periods. Both THg and MeHg concentrations in N. taxispilota declined significantly from the 1980s to 2019, with average values 1.6 to 4-fold lower in contemporary samples. Overall, our data add further evidence to the utility of watersnakes to monitor Hg pollution in aquatic environments and suggest attenuation of this contaminant in watersnakes in our study system.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Plastispheres as hotspots of microbially-driven methylmercury production in paddy soils

Microplastics (MPs) as emerging contaminants have accumulated extensively in agricultural ecosystems and are known to exert important effects on biogeochemical processes. However, how MPs in paddy soils influence the conversion of mercury (Hg) to neurotoxic methylmercury (MeHg) remains poorly understood. Here, in this study, we evaluated the effects of MPs on Hg methylation and associated microbial communities in microcosms using two typical paddy soils in China (i.e., yellow and red soils). Results showed that the addition of MPs significantly increased MeHg production in both soils, which could be related to higher Hg methylation potential in the plastisphere than in the bulk soil. We found significant divergences in the community composition of Hg methylators between the plastisphere and the bulk soil. In addition, the plastisphere had higher proportions of Geobacterales in the yellow soil and Methanomicrobia in the red soil compared with the bulk soil, respectively; and plastisphere also had more densely connected microbial groups between non-Hg methylators and Hg methylators. These microbiota in the plastisphere are different from those in the bulk soil, which could partially account for their distinct MeHg production ability. Our findings suggest plastisphere as a unique biotope for MeHg production and provide new insights into the environment risks of MP accumulation in agricultural soils.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Pectin methyltransferase QUASIMODO2 functions in the formation of seed coat mucilage in Arabidopsis

Pectin, cellulose, and hemicelluloses are major components of primary cell walls in plants. In addition to cell adhesion and expansion, pectin plays a central role in seed mucilage. Seed mucilage contains abundant pectic rhamnogalacturonan-I (RG-I) and lower amounts of homogalacturonan (HG), cellulose, and hemicelluloses. Previously, accumulated evidence has addressed the role of pectin RG-I in mucilage production and adherence. However, less is known about the function of pectin HG in seed coat mucilage formation. In this study, we analyzed a novel mutant, designated things fall apart2 (tfa2), which contains a mutation in HG methyltransferase QUASIMODO2 (QUA2). Etiolated tfa2 seedlings display short hypocotyls and adhesion defects similar to qua2 and tumorous shoot development2 (tsd2) alleles, and show seed mucilage defects. Here, the diminished uronic acid content and methylesterification degree of HG in mutant seed mucilage indicate the role of HG in the formation of seed mucilage. Cellulosic rays in mutant mucilage are collapsed. The epidermal cells of seed coat in tfa2 and tsd2 display deformed columellae and reduced radial wall thickness. Under polyethylene glycol treatment, seeds from these three mutant alleles exhibit reduced germination rates. Together, these data emphasize the requirement of pectic HG biosynthesis for the synthesis of seed mucilage, and the functions of different pectin domains together with cellulose in regulating its formation, expansion, and release.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Mercury methylation potential in a sand dune on Lake Michigan's eastern shoreline

Lake Michigan hosts the largest freshwater sand dune system in the world and is economically important for the fishery industry and tourism. Due to industrial pollution and atmospheric mercury (Hg) deposition, toxic levels of methylmercury (MeHg) have been found in the Lake biota, but little information is known regarding MeHg sources and Hg methylation potential in the shoreline sand dunes. In this study, we conducted anaerobic incubation experiments with beach sands collected from Ludington, Michigan, and examined the effects of organic carbon substrate addition, inorganic nitrogen, and mineral magnetite on Hg methylation. Despite nutrient poor and low-organic carbon conditions, appreciable Hg methylation activity coupled with carbon degradation was observed in the sands. Addition of acetate as a carbon source substantially increased MeHg production from 2 to 380 ng/kg sediment while acetate was rapidly degraded in the first 19 days of incubation. Ammonium addition showed little influence on carbon degradation or Hg methylation, whereas iron oxide addition (~1% dry weight) significantly inhibited both carbon degradation and MeHg production (by up to 90%), highlighting strongly coupled interactions between microbes, carbon substrates, and minerals. This research demonstrates the potential of microbial Hg methylation in the sand dunes, which may play a role in MeHg input and bioaccumulation in the Lake Michigan ecosystem.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Potential impacts of mercury released from thawing permafrost

Abstract Mercury (Hg) is a naturally occurring element that bonds with organic matter and, when converted to methylmercury, is a potent neurotoxicant. Here we estimate potential future releases of Hg from thawing permafrost for low and high greenhouse gas emissions scenarios using a mechanistic model. By 2200, the high emissions scenario shows annual permafrost Hg emissions to the atmosphere comparable to current global anthropogenic emissions. By 2100, simulated Hg concentrations in the Yukon River increase by 14% for the low emissions scenario, but double for the high emissions scenario. Fish Hg concentrations do not exceed United States Environmental Protection Agency guidelines for the low emissions scenario by 2300, but for the high emissions scenario, fish in the Yukon River exceed EPA guidelines by 2050. Our results indicate minimal impacts to Hg concentrations in water and fish for the low emissions scenario and high impacts for the high emissions scenario.

54 ENVIRONMENTAL SCIENCES↗