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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Adsorption and intracellular uptake of mercuric mercury and methylmercury by methanotrophs and methylating bacteria

The cell surface adsorption and intracellular uptake of mercuric mercury Hg(II) and methylmercury (MeHg) are important in determining the fate and transformation of Hg in the environment. However, current information is limited about their interactions with two important groups of microorganisms, i.e., methanotrophs and Hg(II)-methylating bacteria, in aquatic systems. This study investigated the adsorption and uptake dynamics of Hg(II) and MeHg by three strains of methanotrophs, Methylomonas sp. strain EFPC3, Methylosinus trichosporium OB3b, and Methylococcus capsulatus Bath, and two Hg(II)-methylating bacteria, Pseudodesulfovibrio mercurii ND132 and Geobacter sulfurreducens PCA. Distinctive behaviors of these microorganisms towards Hg(II) and MeHg adsorption and intracellular uptake were observed. The methanotrophs took up 55–80% of inorganic Hg(II) inside cells after 24 h incubation, lower than methylating bacteria (>90%). Approximately 80–95% of MeHg was rapidly taken up by all the tested methanotrophs within 24 h. In contrast, after the same time, G. sulfurreducens PCA adsorbed 70% but took up <20% of MeHg, while P. mercurii ND132 adsorbed <20% but took up negligible amounts of MeHg. These results suggest that microbial surface adsorption and intracellular uptake of Hg(II) and MeHg depend on the specific types of microbes and appear to be related to microbial physiology that requires further detailed investigation. Despite being incapable of methylating Hg(II), methanotrophs play important roles in immobilizing both Hg(II) and MeHg, potentially influencing their bioavailability and trophic transfer. Furthermore, methanotrophs are not only important sinks for methane but also for Hg(II) and MeHg and can influence the global cycling of C and Hg.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Mercury Reduction, Uptake, and Species Transformation by Freshwater Alga Chlorella vulgaris under Sunlit and Dark Conditions

As a major entry point of mercury (Hg) to aquatic food webs, algae play an important role in taking up and transforming Hg species in aquatic ecosystems. However, little is known how and to what extent Hg reduction, uptake, and species transformations are mediated by algal cells and their exudates, algal organic matter (AOM), under either sunlit or dark conditions. In this study, using Chlorella vulgaris (CV) as one of the most prevalent freshwater model algal species, we show that solar irradiation could enhance the reduction of mercuric Hg(II) to elemental Hg(0) by both CV cells and AOM. AOM reduced more Hg(II) than algal cells themselves due to cell surface adsorption and uptake of Hg(II) inside the cells under solar irradiation. Synchrotron radiation X-ray absorption near-edge spectroscopy (SR-XANES) analyses indicate that sunlight facilitated the transformation of Hg to less bioavailable species, such as β-HgS and Hg-phytochelatins, compared to Hg(Cysteine) 2 -like species formed in algal cells in the dark. These findings highlight important functional roles and potential mechanisms of algae in Hg reduction and immobilization under varying lighting conditions and how these processes may modulate Hg cycling and bioavailability in the aquatic environment.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Dominance of Particulate Mercury in Stream Transport and Rapid Watershed Recovery from Wildfires in Northern California, USA

Frequency and intensity of wildfires are expected to increase due to climate change, especially in areas with a long summer drought. Forests are a major sink for the global pollutant mercury (Hg), and fluvial transport of Hg from recently burned watersheds has not been widely investigated. Here, we examined two years of fluvial transport of Hg and its speciation (total Hg, methyl-Hg, particulate, and dissolved forms) under storm events and baseflow in two recently burned watersheds with different burned proportions and one nonburned reference watershed in the Coastal Ranges of northern California. We examined postfire storm-event transport of Hg and its methylated form (methyl-Hg), addressed the importance of the “initial runoff pulse” to postfire Hg fluvial transport and its predominant association with suspended solids, and elucidated potential sources of Hg exports from the burned landscapes using geochemical indicators, which suggested that ash materials were likely the significant sources of particulates in the first high-flow season postfire but not subsequently. The maximum total suspended solid and total Hg levels in the “first pulse” at the severely burned watershed were 442 and 46 times higher, respectively, than those at the reference watershed. Stream suspended solid and Hg levels declined substantially in the burned watersheds after just a few months of rainfall likely due to the rapid regrowth of vegetation commonly observed in postfire landscapes, implying that the wildfire effects on immediate Hg inputs from the burned landscape are at most transient in nature.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

National‐Scale Assessment of Total Gaseous Mercury Isotopes Across the United States

Abstract With the 2011 promulgation of the Mercury and Air Toxics Standards by the U.S. Environmental Protection Agency, and the successful negotiation by the United Nations Environment Program of the Minamata Convention, emissions of mercury (Hg) have declined in the United States. While the declines in atmospheric Hg concentrations in North America are encouraging, linking the declines to changing domestic and global source portfolios remains challenging. To address these research gaps, the U.S. Geological Survey initiated the first national‐scale effort to establish a baseline of total gaseous mercury stable isotope values at 31 sites distributed across the United States. Results indicated that unique Hg sources, such as Hg evasion from an elemental Hg contaminated site or free tropospheric intrusions in high altitude sites, were distinguishable from background atmospheric values. Minor gradients were observed across the nation, with regions of heavy industrial activity demonstrating lower δ 202 Hg, but no consistent changes in other isotopes such as Δ 199 Hg and Δ 200 Hg were observed. Furthermore, δ 202 Hg was impacted by foliar uptake and senescence but trends varied between forested regions in the northeastern and midwestern United States. These data demonstrate regional emission sources and other environmental variables can impact total gaseous Hg (TGM) isotope values, highlighting the need to characterize atmospheric Hg isotopes over larger geographical areas to evaluate changes related to national and international Hg regulations.

Tate, Michael T.↗
DOE OSTI2024

Horizontal gene transfer of the Mer operon is associated with large effects on the transcriptome and increased tolerance to mercury in nitrogen-fixing bacteria

Abstract Background Mercury (Hg) is highly toxic and has the potential to cause severe health problems for humans and foraging animals when transported into edible plant parts. Soil rhizobia that form symbiosis with legumes may possess mechanisms to prevent heavy metal translocation from roots to shoots in plants by exporting metals from nodules or compartmentalizing metal ions inside nodules. Horizontal gene transfer has potential to confer immediate de novo adaptations to stress. We used comparative genomics of high quality de novo assemblies to identify structural differences in the genomes of nitrogen-fixing rhizobia that were isolated from a mercury (Hg) mine site that show high variation in their tolerance to Hg. Results Our analyses identified multiple structurally conserved merA homologs in the genomes of Sinorhizobium medicae and Rhizobium leguminosarum but only the strains that possessed a Mer operon exhibited 10-fold increased tolerance to Hg. RNAseq analysis revealed nearly all genes in the Mer operon were significantly up-regulated in response to Hg stress in free-living conditions and in nodules. In both free-living and nodule environments, we found the Hg-tolerant strains with a Mer operon exhibited the fewest number of differentially expressed genes (DEGs) in the genome, indicating a rapid and efficient detoxification of Hg from the cells that reduced general stress responses to the Hg-treatment. Expression changes in S. medicae while in bacteroids showed that both rhizobia strain and host-plant tolerance affected the number of DEGs. Aside from Mer operon genes, nif genes which are involved in nitrogenase activity in S. medicae showed significant up-regulation in the most Hg-tolerant strain while inside the most Hg-accumulating host-plant. Transfer of a plasmid containing the Mer operon from the most tolerant strain to low-tolerant strains resulted in an immediate increase in Hg tolerance, indicating that the Mer operon is able to confer hyper tolerance to Hg. Conclusions Mer operons have not been previously reported in nitrogen-fixing rhizobia. This study demonstrates a pivotal role of the Mer operon in effective mercury detoxification and hypertolerance in nitrogen-fixing rhizobia. This finding has major implications not only for soil bioremediation, but also host plants growing in mercury contaminated soils.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Materials Data on TaHg2F6 by Materials Project

TaHg2F6 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Ta3+ is bonded in an octahedral geometry to six F1- atoms. There are a spread of Ta–F bond distances ranging from 1.92–1.94 Å. There are two inequivalent Hg+1.50+ sites. In the first Hg+1.50+ site, Hg+1.50+ is bonded in a distorted rectangular see-saw-like geometry to four F1- atoms. There are two shorter (2.92 Å) and two longer (2.99 Å) Hg–F bond lengths. In the second Hg+1.50+ site, Hg+1.50+ is bonded in a 6-coordinate geometry to four F1- atoms. There are two shorter (2.88 Å) and two longer (2.97 Å) Hg–F bond lengths. There are five inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted single-bond geometry to one Ta3+ and two Hg+1.50+ atoms. In the second F1- site, F1- is bonded in a distorted single-bond geometry to one Ta3+ and two equivalent Hg+1.50+ atoms. In the third F1- site, F1- is bonded in a single-bond geometry to one Ta3+ atom. In the fourth F1- site, F1- is bonded in a distorted single-bond geometry to one Ta3+ and two equivalent Hg+1.50+ atoms. In the fifth F1- site, F1- is bonded in a distorted single-bond geometry to one Ta3+ and two equivalent Hg+1.50+ atoms. The F–Ta bond length is 1.92 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ZnHg3 by Materials Project

Hg3Zn is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent Hg sites. In the first Hg site, Hg is bonded in a distorted body-centered cubic geometry to four equivalent Hg and four equivalent Zn atoms. All Hg–Hg bond lengths are 3.21 Å. All Hg–Zn bond lengths are 3.21 Å. In the second Hg site, Hg is bonded in a body-centered cubic geometry to eight equivalent Hg atoms. Zn is bonded in a body-centered cubic geometry to eight equivalent Hg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiHg3 by Materials Project

LiHg3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Li is bonded in a body-centered cubic geometry to eight equivalent Hg atoms. All Li–Hg bond lengths are 3.10 Å. There are two inequivalent Hg sites. In the first Hg site, Hg is bonded to four equivalent Li and four equivalent Hg atoms to form a mixture of distorted corner, edge, and face-sharing HgLi4Hg4 tetrahedra. All Hg–Hg bond lengths are 3.10 Å. In the second Hg site, Hg is bonded in a body-centered cubic geometry to eight equivalent Hg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hg3Rh by Materials Project

RhHg3 is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Rh is bonded to twelve Hg atoms to form RhHg12 cuboctahedra that share corners with four equivalent RhHg12 cuboctahedra, edges with eight equivalent RhHg12 cuboctahedra, edges with sixteen equivalent HgHg8Rh4 cuboctahedra, faces with four equivalent RhHg12 cuboctahedra, and faces with eight equivalent HgHg8Rh4 cuboctahedra. There are four shorter (2.94 Å) and eight longer (3.10 Å) Rh–Hg bond lengths. There are two inequivalent Hg sites. In the first Hg site, Hg is bonded to four equivalent Rh and eight Hg atoms to form HgHg8Rh4 cuboctahedra that share corners with twelve equivalent HgHg8Rh4 cuboctahedra, edges with eight equivalent RhHg12 cuboctahedra, edges with eight equivalent HgHg8Rh4 cuboctahedra, faces with four equivalent RhHg12 cuboctahedra, and faces with ten equivalent HgHg8Rh4 cuboctahedra. There are four shorter (2.94 Å) and four longer (3.10 Å) Hg–Hg bond lengths. In the second Hg site, Hg is bonded in a distorted square co-planar geometry to four equivalent Rh and eight equivalent Hg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hg3Ir by Materials Project

IrHg3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ir is bonded to twelve Hg atoms to form IrHg12 cuboctahedra that share corners with four equivalent IrHg12 cuboctahedra, corners with eight equivalent HgHg8Ir4 cuboctahedra, edges with eight equivalent IrHg12 cuboctahedra, edges with sixteen equivalent HgHg8Ir4 cuboctahedra, faces with four equivalent IrHg12 cuboctahedra, and faces with fourteen HgHg8Ir4 cuboctahedra. There are four shorter (2.94 Å) and eight longer (3.10 Å) Ir–Hg bond lengths. There are two inequivalent Hg sites. In the first Hg site, Hg is bonded to four equivalent Ir and eight Hg atoms to form HgHg8Ir4 cuboctahedra that share corners with twelve equivalent HgHg8Ir4 cuboctahedra, edges with eight equivalent IrHg12 cuboctahedra, edges with sixteen HgHg8Ir4 cuboctahedra, faces with four equivalent IrHg12 cuboctahedra, and faces with fourteen HgHg8Ir4 cuboctahedra. There are four shorter (2.94 Å) and four longer (3.10 Å) Hg–Hg bond lengths. In the second Hg site, Hg is bonded to four equivalent Ir and eight equivalent Hg atoms to form distorted HgHg8Ir4 cuboctahedra that share corners with four equivalent HgHg8Ir4 cuboctahedra, corners with eight equivalent IrHg12 cuboctahedra, edges with twenty-four HgHg8Ir4 cuboctahedra, faces with six equivalent IrHg12 cuboctahedra, and faces with twelve HgHg8Ir4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cd2Hg2H(SO5)2 by Materials Project

Hg2Cd2H(SO5)2 crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. there are two inequivalent Hg+1.50+ sites. In the first Hg+1.50+ site, Hg+1.50+ is bonded to six O2- atoms to form distorted HgO6 octahedra that share corners with two equivalent CdHO5 square pyramids, corners with four equivalent SO4 tetrahedra, and edges with two equivalent CdHO5 square pyramids. There are a spread of Hg–O bond distances ranging from 2.10–2.74 Å. In the second Hg+1.50+ site, Hg+1.50+ is bonded in a distorted linear geometry to four O2- atoms. There are two shorter (2.06 Å) and two longer (2.80 Å) Hg–O bond lengths. Cd2+ is bonded to one H1+ and five O2- atoms to form distorted CdHO5 square pyramids that share a cornercorner with one HgO6 octahedra, a cornercorner with one CdHO5 square pyramid, corners with three equivalent SO4 tetrahedra, an edgeedge with one HgO6 octahedra, and an edgeedge with one CdHO5 square pyramid. The corner-sharing octahedral tilt angles are 67°. The Cd–H bond length is 2.48 Å. There are a spread of Cd–O bond distances ranging from 2.24–2.36 Å. H1+ is bonded in a distorted water-like geometry to two equivalent Cd2+ atoms. S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with two equivalent HgO6 octahedra and corners with three equivalent CdHO5 square pyramids. The corner-sharing octahedra tilt angles range from 44–47°. There are a spread of S–O bond distances ranging from 1.47–1.51 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one Hg+1.50+, one Cd2+, and one S6+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cd2+ and one S6+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one Hg+1.50+ and one S6+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to one Hg+1.50+, one Cd2+, and one S6+ atom. In the fifth O2- site, O2- is bonded to two Hg+1.50+ and two equivalent Cd2+ atoms to form a mixture of edge and corner-sharing OCd2Hg2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiHg3 by Materials Project

LiHg3 is alpha bismuth trifluoride structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Li is bonded to twelve Hg atoms to form LiHg12 cuboctahedra that share corners with four equivalent LiHg12 cuboctahedra, corners with eight equivalent HgLi4Hg8 cuboctahedra, edges with eight equivalent LiHg12 cuboctahedra, faces with four equivalent LiHg12 cuboctahedra, and faces with six equivalent HgLi4Hg8 cuboctahedra. There are eight shorter (3.16 Å) and four longer (3.28 Å) Li–Hg bond lengths. There are two inequivalent Hg sites. In the first Hg site, Hg is bonded in a 4-coordinate geometry to four equivalent Li and four equivalent Hg atoms. All Hg–Hg bond lengths are 3.16 Å. In the second Hg site, Hg is bonded to four equivalent Li and eight equivalent Hg atoms to form distorted HgLi4Hg8 cuboctahedra that share corners with four equivalent HgLi4Hg8 cuboctahedra, corners with eight equivalent LiHg12 cuboctahedra, edges with eight equivalent HgLi4Hg8 cuboctahedra, faces with four equivalent HgLi4Hg8 cuboctahedra, and faces with six equivalent LiHg12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hg3S2O11 by Materials Project

(Hg3(SO5)2)2O2 crystallizes in the monoclinic C2/c space group. The structure is two-dimensional and consists of four water molecules and two Hg3(SO5)2 sheets oriented in the (0, 0, 1) direction. In each Hg3(SO5)2 sheet, there are two inequivalent Hg sites. In the first Hg site, Hg is bonded to six O atoms to form HgO6 octahedra that share corners with four equivalent SO4 tetrahedra. There are a spread of Hg–O bond distances ranging from 2.11–2.60 Å. In the second Hg site, Hg is bonded in a distorted linear geometry to two O atoms. There are one shorter (2.05 Å) and one longer (2.09 Å) Hg–O bond lengths. S is bonded to four O atoms to form SO4 tetrahedra that share corners with two equivalent HgO6 octahedra. The corner-sharing octahedra tilt angles range from 47–64°. There are a spread of S–O bond distances ranging from 1.47–1.54 Å. There are five inequivalent O sites. In the first O site, O is bonded in a distorted single-bond geometry to one Hg and one S atom. In the second O site, O is bonded in a bent 120 degrees geometry to two Hg atoms. In the third O site, O is bonded in a bent 120 degrees geometry to one Hg and one S atom. In the fourth O site, O is bonded in a single-bond geometry to one S atom. In the fifth O site, O is bonded in a distorted bent 120 degrees geometry to one Hg and one S atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuHg3 by Materials Project

PuHg3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Pu is bonded in a distorted body-centered cubic geometry to fourteen Hg atoms. There are eight shorter (3.19 Å) and six longer (3.68 Å) Pu–Hg bond lengths. There are two inequivalent Hg sites. In the first Hg site, Hg is bonded in a distorted body-centered cubic geometry to four equivalent Pu and four equivalent Hg atoms. All Hg–Hg bond lengths are 3.19 Å. In the second Hg site, Hg is bonded in a 8-coordinate geometry to six equivalent Pu and eight equivalent Hg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThHg3 by Materials Project

ThHg3 crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Th is bonded in a 12-coordinate geometry to six equivalent Hg atoms. All Th–Hg bond lengths are 3.32 Å. There are two inequivalent Hg sites. In the first Hg site, Hg is bonded in a 6-coordinate geometry to six equivalent Hg atoms. All Hg–Hg bond lengths are 3.14 Å. In the second Hg site, Hg is bonded in a 6-coordinate geometry to three equivalent Th and three equivalent Hg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg5Hg by Materials Project

Mg5Hg crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are five inequivalent Mg sites. In the first Mg site, Mg is bonded to ten Mg and two equivalent Hg atoms to form distorted MgMg10Hg2 cuboctahedra that share corners with fourteen MgMg10Hg2 cuboctahedra, edges with five MgMg4Hg2 cuboctahedra, and faces with six MgMg10Hg2 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.02–3.27 Å. Both Mg–Hg bond lengths are 3.20 Å. In the second Mg site, Mg is bonded in a distorted single-bond geometry to four Mg and one Hg atom. Both Mg–Mg bond lengths are 3.16 Å. The Mg–Hg bond length is 3.09 Å. In the third Mg site, Mg is bonded to four Mg and two equivalent Hg atoms to form distorted MgMg4Hg2 cuboctahedra that share corners with fourteen MgMg10Hg2 cuboctahedra, edges with four MgMg10Hg2 cuboctahedra, and faces with two equivalent MgMg4Hg2 cuboctahedra. Both Mg–Mg bond lengths are 3.13 Å. Both Mg–Hg bond lengths are 3.10 Å. In the fourth Mg site, Mg is bonded to nine Mg and three equivalent Hg atoms to form distorted MgMg9Hg3 cuboctahedra that share corners with twelve MgMg4Hg2 cuboctahedra, edges with seven MgMg10Hg2 cuboctahedra, and faces with six MgMg10Hg2 cuboctahedra. There are two shorter (3.20 Å) and two longer (3.27 Å) Mg–Mg bond lengths. There are two shorter (3.11 Å) and one longer (3.21 Å) Mg–Hg bond lengths. In the fifth Mg site, Mg is bonded in a 12-coordinate geometry to five Mg and two equivalent Hg atoms. Both Mg–Hg bond lengths are 3.06 Å. Hg is bonded in a 12-coordinate geometry to ten Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgHg6(N3O13)2 by Materials Project

MgO6(Hg3O)2(NO3)6 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of one magnesium;dihydroxide;tetrahydrate molecule, six nitric acid molecules, and two Hg3O clusters. In each Hg3O cluster, there are three inequivalent Hg sites. In the first Hg site, Hg is bonded in a single-bond geometry to one O atom. The Hg–O bond length is 2.15 Å. In the second Hg site, Hg is bonded in a single-bond geometry to one O atom. The Hg–O bond length is 2.15 Å. In the third Hg site, Hg is bonded in a single-bond geometry to one O atom. The Hg–O bond length is 2.15 Å. O is bonded in a trigonal planar geometry to three Hg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PmHg3 by Materials Project

PmHg3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Pm is bonded in a distorted body-centered cubic geometry to fourteen Hg atoms. There are eight shorter (3.18 Å) and six longer (3.68 Å) Pm–Hg bond lengths. There are two inequivalent Hg sites. In the first Hg site, Hg is bonded to four equivalent Pm and four equivalent Hg atoms to form a mixture of distorted edge, face, and corner-sharing HgPm4Hg4 tetrahedra. All Hg–Hg bond lengths are 3.18 Å. In the second Hg site, Hg is bonded in a 8-coordinate geometry to six equivalent Pm and eight equivalent Hg atoms.

36 MATERIALS SCIENCE↗