Hg and Cd are rare chemical elements found in magmatic PGE and Au mineralization and typical of this mineralization in the Late Riphean Yoko-Dovyren plagioperidotite–troctolite–gabbronorite intrusion ...hosted in the Baikalides of the Baikal area. The paper discusses variations in the composition, associations, and distribution traits of the Hg- and Cd-bearing Pt, Pd, Au, and Ag minerals. Many of the precious-metal minerals are Pt, Pd, and Au chalcogenides and intermetallic compounds of postmagmatic genesis and occur as single crystals and stringers in sulfides and silicate matrix and at their contacts. The minerals were formed with the participation of fluids from the crystallizing Fe–Cu–Ni sulfide melts. They are constrained to the central part of the intrusion and found in sulfide-bearing plagiolherzolite (PL) in the lower part of the intrusion, in sulfide-bearing pegmatoid troctolite (T) in the bottom portion of the troctolite unit, and in sulfide-bearing pegmatoid anorthosite (A) in the top part of the troctolite unit. From PL to T and further to A, the content and diversity of the Hg-bearing minerals remarkably increase, with Hg distributed in these minerals very unevenly, and with Cd-bearing minerals identified only in A. The leading Hg concentrators in T and A are pneumatolytic (fluid–metasomatic) moncheite and, particularly, later telargpalite (Pd,Ag)
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(Te,Pd,Hg), which contains up to 11 wt % Hg. The latter mineral is sometimes found in association with Hg-electrum, kustelite, and potarite. Potarite in T is Pb-rich, and this mineral in A is Pb-free. Appreciable Hg concentrations in precious-metal minerals in the Yoko-Dovyren intrusion suggest that these minerals crystallized in a closed system at high temperatures. Potarite content in A is much higher, and Hg concentration in telargpalite in A is notably lower (2.9 wt % Hg on average) than in this mineral in T (5.9 wt % Hg on average). The potarite might have been produced by epigenetic serpentinization processes (low-grade metamorphism) at the expense of the material of pneumatolytic Hg-bearing telatgpalite, kotulskite, and zvyagentsivite. This corresponds to specifics in Hg distribution in the telatgpalite, kotulskite, and zvyagentsivite in T and A and much higher intensity of metamorphism.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Corn is a crucial crop in China and is widely cultivated in the mercury (Hg) mining region of Guizhou. This study analyzed the Hg content in soil and corn plant samples from the Wuchuan Hg mining ...area (WCMA) and the surrounding non-Hg mining regions (SNMR). The findings suggest that ongoing ecological rehabilitation and environmental conservation measures in the WCMA have significantly decreased the Hg content in corn kernels. The Hg concentration in different parts of the corn plant varied, being higher in the roots, tassels, and leaves and lower in kernels and stalks. Hg stored in corn plant growing in the WCMA primarily originates from the soil (55.4%), while in the SNMR, it mainly comes from the atmosphere (74.9%). Despite counted only about 7% of the total plant mass, corn roots play a crucial role in soil Hg pollution remediation when corn is used for remediation. Household corn residues burning release about 58.5% and 66.9% of the stored Hg in corn plants growing in the WCMA and the SNMR, respectively, into the atmosphere. Our findings indicate that corn cultivation acts as a reservoir for both soil and atmospheric Hg in the SNMR, while in the WCMA, it serves as a source of atmospheric Hg.
•Ecological restoration in the WCMA significantly reduced mercury levels in corn kernels.•In WCMA, soil is the primary source of Hg in corn plants, while in the SNMR, the atmosphere dominates.•Proper handling the corn roots is crucial for using corn as a phytoremediation plant.•Corn cultivation serves as a Hg sink in the SNMR and a source of atmospheric Hg in the WCMA.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Past industrial activities have generated many contaminated lands from which Mercury (Hg) escapes, primarily by volatilization. Current phytomanagement techniques aim to limit Hg dispersion by ...increasing its stabilization in soil. Although soil fungi represent a source of Hg emission associated with biovolatilization mechanisms, there is limited knowledge about how dead fungal residues (i.e., fungal necromass) interact with soil Hg. This study determined the Hg biosorption potential of fungal necromass and the chemical drivers of passive Hg binding with dead mycelia. Fungal necromass was incubated under field conditions with contrasting chemical properties at a well-characterized Hg phytomanagement experimental site in France. After four months of incubation in soil, fungal residues passively accumulated substantial quantities of Hg in their recalcitrant fractions ranging from 400 to 4500 μg Hg/kg. In addition, infrared spectroscopy revealed that lipid compounds explained the amount of Hg biosorption to fungal necromass. Based on these findings, we propose that fungal necromass is likely an important factor in Hg immobilization in soil.
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•Fungal necromass accumulates large quantities of Mercury (Hg) in soil.•Hg biosorption depends on the chemical properties of fungal residues.•Lipid acyl chains are positively related to Hg adsorption on fungal necromass.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Waterfowl wintering along the lower Penobscot River, Maine continue to be exposed to elevated Hg concentrations from the HoltraChem chlor-alkali plant that operated along the river between 1967 and ...2000. In American black ducks (Anas rubripes) total Hg in duck breast muscle increased with residence time on contaminated marshes, reaching means of 0.82±0.21μg/g ww (wet weight) by the end of the fall hunting season, and prompting Maine to issue a human consumption advisory on duck breast muscle. Methyl Hg comprised over 99% of the total Hg in breast muscle. The ratio of Hg concentrations in blood and muscle were strongly correlated and approached 1:1 after extended residence times. Primary feather (P1) total Hg concentrations averaged 2.2±1.3μg/g fw (fresh weight), verifying low Hg exposure during feather growth on distant breeding grounds the preceding summer. Mercury concentrations in black ducks, following winter residence along the lower Penobscot exceeded levels associated with reproductive toxicity. Carry-over of Hg to summer breeding grounds may limit the subsequent reproductive success of black ducks.
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•Mercury (Hg) exceeds safe consumption limits in waterfowl during the fall hunting season along the lower Penobscot River, Maine•Primary feather Hg concentrations document low mercury exposure on breeding grounds•Mercury concentrations increase with residence time during fall and winter•Mercury concentrations in duck blood and breast muscle are strongly correlated•By spring, Hg concentrations in ducks exceed levels associated with reproductive toxicity and may carry-over to summer breeding grounds
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Mercury (Hg) is a volatile, bioaccumulative, and toxic heavy metal, and its global distribution is controlled by the Hg biogeochemical cycle in the atmosphere-land-ocean systems and the deep Hg cycle ...in interior reservoirs (e.g., mantle and crust). The biogeochemical cycle has been relatively well studied, but the deep Hg cycle remains relatively poorly constrained. Mercury isotopes undergo mass-dependent fractionation (MDF) and unique mass-independent fractionation (MIF) which can provide good constraints on large-scale Hg cycling. In this review, we provide a summary of available results on Hg abundance and isotopic composition in the atmosphere-land-ocean systems and interior reservoirs, with a focus on linking the Hg biogeochemical cycle to the deep Hg cycle. Through this effort, a few key points can be pointed out: (1) Natural and anthropogenic activities release large amounts of Hg into the atmosphere, which is transported on a global scale and deposited in terrestrial and marine systems; (2) Major constituents of the mantle and crust, e.g., mid-ocean ridge basalts (MORBs) and granites, show much lower Hg abundance than the atmosphere-land-ocean systems due to volcanic Hg(0) degassing and the formation of Hg-bearing ore deposits; (3) Mercury isotopes, especially Δ199Hg values, are useful in tracing surface Hg recycling into mantle and crust; (4) Hg(II) photo-reduction in the atmosphere yields negative Δ199Hg values in gaseous Hg(0) and positive Δ199Hg values in Hg(II) species, which results in negative Δ199Hg values in terrestrial systems (dominant deposition of Hg(0)) and positive Δ199Hg values in marine systems (dominant deposition of Hg(II); (5) MORBs and arc-related basalts (IABs) show positive Δ199Hg values, suggesting marine Hg recycling into the oceanic crust and upper mantle via plate subduction. Oceanic island basalts (OIBs) and continental flood basalts (CFBs) mostly display near-zero Δ199Hg values, suggesting limited surface Hg recycling into the lower mantle. Granites show positive to negative Δ199Hg values, suggesting the continental crust receives Hg from the metasomatized mantle and remelted terrestrial material. Opposing Δ199Hg values in arc-related and intracontinental hydrothermal systems highlights the great potential of using Hg isotopes for metallogenic tracing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A mercury resistant bacterial strain, SA2, was isolated from soil contaminated with mercury. The 16S rRNA gene sequence of this isolate showed 99% sequence similarity to the genera Sphingobium and ...Sphingomonas of α-proteobacteria group. However, the isolate formed a distinct phyletic line with the genus Sphingobium suggesting the strain belongs to Sphingobium sp. Toxicity studies indicated resistance to high levels of mercury with estimated EC50 values 4.5 mg L−1 and 44.15 mg L−1 and MIC values 5.1 mg L−1 and 48.48 mg L−1 in minimal and rich media, respectively. The strain SA2 was able to volatilize mercury by producing mercuric reductase enzyme which makes it potential candidate for remediating mercury. ICP-QQQ-MS analysis of Hg supplemented culture solutions confirmed that almost 79% mercury in the culture suspension was volatilized in 6 h. A very small amount of mercury was observed to accumulate in cell pellets which was also evident according to ESEM-EDX analysis. The mercuric reductase gene merA was amplified and sequenced. The deduced amino acid sequence demonstrated sequence homology with α-proteobacteria and Ascomycota group.
•First report on Sphingobium with high mercury true tolerance and volatilization.•80% of mercury is volatilized in six hours which has bioremediation potential.•The merA gene from SA2 shows homology with α-proteobacteria and Ascomycota fungi.•The mercury reductase enzyme, MerA could be employed in bioremediation process.•Bacteria grown in complex media does not reflect true tolerance to mercury.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The formation of neurotoxic methylmercury (MeHg) in paddy fields and its accumulation by rice plants is of high environmental concern. The contribution of different geochemical mercury (Hg) pools in ...paddy soils to MeHg production and its accumulation by rice seedlings is not well-studied up to now. Therefore, we investigated the impact of different inorganic Hg forms, including HgCl2, nano-particulated HgS (nano-HgS), Hg bound with dissolved organic matter (Hg-DOM), β-HgS, and α-HgS, at levels of 5 mg Hg/kg soil and 50 mg Hg/kg soil, on the production of MeHg in the soil during rice growing season. Further, we studied the uptake of MeHg by the roots, stalks, leaves, and grains of rice in the tillering, panicle formation, and ripening growth stages, and compared these treatments to a non-polluted soil (control). MeHg contents in HgCl2 polluted soil were the highest, and were 13.5 times and 36.1 times higher than control in 5 and 50 mg/kg Hg treatments, respectively. MeHg contents in α-HgS, β-HgS, nano-HgS, and Hg-DOM polluted soil were 3.9, 2.6, 2.4, and 1.7 times, and 4.4, 15.1, 6.7, and 10.9 times higher than control in 5 and 50 mg/kg Hg treatments, respectively, suggesting the mobilization and methylation of these Hg complexes. The ratio of MeHg to total Hg in the pore water (indication of methylation potential) in HgCl2 and β-HgS treatments were higher than in Hg-DOM, α-HgS, and nano-HgS treatments. HgCl2 treatment resulted in significantly higher MeHg contents in the root, stalk, leaf, and brown rice than nano-HgS, Hg-DOM, β-HgS, and α-HgS treatments both in 5 and 50 mg/kg Hg polluted soils. Rice grain in HgCl2 treatment showed a potential hazard to human health, as indicated by high health risk index (HRI > 1) of MeHg. Current results improve our understanding of MeHg production in soil polluted with different Hg forms, and the assessment of human health risks from consumption of MeHg-laden rice grain at Hg polluted sites with different Hg forms in soils.
•The methylation of Hg(II), nano-HgS, Hg-DOM, β-HgS, and α-HgS in soil was studied.•The Hg(II) treatment resulted in the highest MeHg content in soil, pore water, rice.•The nano HgS, Hg-DOM, β-HgS, and α-HgS were more mobilized relative to control.•Hg-DOM and nano HgS polluted soils showed the highest THg in pore water.•Hg(II) polluted soils showed a hazard to human health.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Mercury (Hg) methylation, methylmercury (MeHg) demethylation, and inorganic redox transformations of Hg are microbe-mediating processes that determine the fate and cycling of Hg and MeHg in many ...environments, and by doing so influence the health of humans and wild life. The discovery of the Hg methylation genes, hgcAB, in the last decade together with advances in high throughput and genome sequencing methods, have resulted in an expanded appreciation of the diversity of Hg methylating microbes. This review aims to describe experimentally confirmed and recently discovered hgcAB gene-carrying Hg methylating microbes; phylogenetic and taxonomic analyses are presented. In addition, the current knowledge on transformation mechanisms, the organisms that carry them out, and the impact of environmental parameters on Hg methylation, MeHg demethylation, and inorganic Hg reduction and oxidation is summarized. This knowledge provides a foundation for future action toward mitigating the impact of environmental Hg pollution.
Atmosphere–surface exchange of elemental mercury (Hg(0)) is a vital component in global Hg cycling; however, Hg isotope fractionation remains largely unknown. Here, we report Hg isotope fractionation ...during air–surface exchange from terrestrial surfaces at sites of background (two) and urban (two) character and at five sites contaminated by Hg mining. Atmospheric Hg(0) deposition to soils followed kinetic isotope fractionation with a mass-dependent (MDF) enrichment factor of −4.32‰, and negligible mass-independent fractionation (MIF). Net Hg(0) emission generated average MDF enrichment factors (ε202Hg) of −0.91, −0.59, 1.64, and −0.42‰ and average MIF enrichment factors (E 199Hg) of 0.07, −0.20, −0.14, and 0.21‰ for urban, background, and Hg mining soils and cinnabar tailing, respectively. Positive correlations between ε202Hg and ambient Hg(0) concentration indicate that the co-occurring Hg(0) deposition (accounting for 10–39%) in a regime of net soil emission grows with ambient Hg(0). The MIF of Hg(0) emission from soils (E 199Hg range −0.27 to 0.14‰, n = 8) appears to be overall controlled by the photochemical reduction of kinetically constrained Hg(II) bonded to O ligands in background soils, while S ligands may have been more important in Hg mining area soils. In contrast, the small positive MIF of Hg(0) emission from cinnabar ore tailing (mean E 199Hg = 0.21‰) was likely controlled by abiotic nonphotochemical reduction and liquid Hg(0) evaporation. This research provides critical observational constraints on understanding the Hg(0) isotope signatures released from and deposited to terrestrial surfaces and highlight stable Hg isotopes as a powerful tool for resolving atmosphere–surface exchange processes.
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IJS, KILJ, NUK, PNG, UL, UM
The re-emission and subsurface migration of legacy mercury (Hg) are not well understood due to limited knowledge of the driving processes. To investigate these processes at a decommissioned ...chlor-alkali plant, we used mercury stable isotopes and chemical speciation analysis. The isotopic composition of volatilized Hg(0) was lighter compared to the bulk total Hg (THg) pool in salt-sludge and adjacent surface soil with mean ε202HgHg(0)‑THg values of −3.29 and −2.35‰, respectively. Hg(0) exhibited dichotomous directions (E 199HgHg(0)‑THg = 0.17 and −0.16‰) of mass-independent fractionation (MIF) depending on the substrate from which it was emitted. We suggest that the positive MIF enrichment during Hg(0) re-emission from salt-sludge was overall controlled by the photoreduction of Hg(II) primarily ligated by Cl– and/or the evaporation of liquid Hg(0). In contrast, O-bonded Hg(II) species were more important in the adjacent surface soils. The migration of Hg from salt-sludge to subsurface soil associated with selective Hg(II) partitioning and speciation transformation resulted in deep soils depleted in heavy isotopes (δ202Hg = −2.5‰) and slightly enriched in odd isotopes (Δ199Hg = 0.1‰). When tracing sources using Hg isotopes, it is important to exercise caution, particularly when dealing with mobilized Hg, as this fraction represents only a small portion of the sources.
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IJS, KILJ, NUK, PNG, UL, UM
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