Bioremediation using mercury (Hg)-volatilizing and immobilizing bacteria is an eco-friendly and cost-effective strategy for Hg-polluted farmland. However, the mechanisms controlling the ...transformation of and resistance to Hg(II) by these bacteria remain unknown. In this study, a plant-associated Pseudomonas sp. strain, AN-B15 was isolated and determined to effectively remove Hg(II) under both nutrient-poor and nutrient-rich conditions via volatilization by transforming Hg(II) to Hg(0) and immobilization by transforming Hg(II) to mercury sulfide and Hg-sulfhydryl. Genome and transcriptome analyses revealed that the molecular mechanisms involved in Hg(II) resistance in AN-B15 were a collaborative process involving multiple metabolic systems at the transcriptional level. Under Hg(II) stress, AN-B15 upregulated genes involved in the mer operon and producing the reducing power to rapidly volatilize Hg(II), thereby decreasing its toxicity. Hydroponic culture experiments also revealed that inoculation with strain AN-B15 alleviated Hg-induced toxicity and reduced the uptake of Hg(II) in the roots of wheat seedlings, as explained by the volatilization and immobilization of Hg(II) and plant growth-promoting traits of AN-B15. Overall, the results from the in vitro assays provided vital information that are essential for understanding the mechanism of Hg(II) resistance in plant-associated bacteria, which can also be applied for the bioremediation of Hg-contamination in future.
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•Strain AN-B15 immobilize Hg(II) by transforming Hg(II) to mercury sulfide and Hg-sulfhydryl.•Strain AN-B15 volatilize Hg(II) by transforming Hg(II) to Hg(0).•Strain AN-B15 reduced Hg accumulation and phytotoxicity for wheat seedlings.•Hg resistance in AN-B15 is a collaborative process involving multiple metabolic systems at the transcriptional level.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Due to mercury (Hg) is a global pollutant, the biogeochemistry of Hg in Earth's surface environment has been well studied. However, the cycling of Hg in interior reservoirs remains less clear, ...limiting our understanding of the global Hg geochemical cycle. Here, we use Hg isotopes to constrain the sources of Hg in typical alkaline lamprophyres in South China: the Early Ordovician lamprophyres in the Zhenyuan area and the Late Cretaceous lamprophyres in the Zhenfeng area. Lamprophyres from both areas are enriched in large-ion-lithophile elements (LILEs) and light rare earth elements (LREEs) but depleted in high-field-strength elements (HSFEs), typical of subduction-related igneous rocks. The Early Ordovician and Late Cretaceous lamprophyres show significantly positive to near-zero Δ199Hg values of 0.18 to 0.37‰ and − 0.08 to 0.36‰, respectively. The positive Δ199Hg values are consistent with that reported for marine sediments and seawaters, suggesting Hg in these lamprophyres was sourced from marine reservoirs. This study suggests a heterogeneous distribution of Hg in the mantle and demonstrates that subducted marine materials can have contributed a substantial amount of Hg into the mantle.
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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) alkylation and methane (CH4) emissions pose significant global concerns. Paddy soil, due to its long-term anaerobic conditions and abundant organic matter, is hotspots for soil Hg ...alkylation and CH4 emissions. However, the relevance between Hg alkylation and CH4 emissions, especially their simultaneous reduction strategies, remains poorly understood. Here, we investigated the effects of biochar (BC), selenium (Se) and rice straw (RS) amendments on Hg alkylation and CH4 emissions in paddy soil, and the accumulation of Hg speciation. Results found that both BC and RS amendments significantly increased the levels of soil organic carbon (SOC) and humification index (HIX). Furthermore, BC decreased the concentrations of Hg(II), methylmercury (MeHg) and ethylmercury (EtHg) by 63.1%, 53.6% and 100% in rice grains. However, RS increased Hg(II) concentration but decreased the total Hg (THg), MeHg and EtHg concentrations in rice grains. Compared to the CK, RS significantly increased CH4 emissions, while BC decreased CH4 emissions, and Se showed no significant difference. Se amendment increased the Hg(II) and EtHg concentrations by 20.3% and 17.0% respectively, and decreased the MeHg concentration in grains by 58.3%. Both BC and RS impacted the abundance of methanogens by enhancing SOC and HIX, subsequently modulating the relevance between Hg alkylation and CH4 emissions. These findings provide insights into the relevance between Hg alkylation and CH4 emissions and propose potential mitigation mechanisms in Hg-contaminated paddy soil.
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•Soil amendments (biochar, rice straw, or Se) reduced uptake of MeHg in rice grains.•Alkylmercury reduction co-occurred with carbon increase following biochar addition.•Soil amendments decreased the relevance between Hg alkylation and CH4 emissions.•Biochar addition exhibited the best comprehensive environmental effect.•Relevance between Hg alkylation and CH4 emissions was mediated by Methanocellaceae.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effects of a model natural organic matter (NOM) on the transport of Hg(II) into diffusive gradient in thin-film devices (DGTs) was evaluated in order to better understand their ability to measure ...colloidal Hg species in porewater. The presence of NOM significantly reduced the diffusivity of the Hg(II) species and the reduction was dependent upon NOM to Hg(II) ratio. This relationship was modeled by determining the Hg(II) partition coefficients (Kd) of size fractionated NOM obtained by ultrafiltration and estimating the Hg diffusivity through the DGT for the different NOM size fractions across a range of Hg-NOM ratios. The estimated diffusivities were consistent with experimental observations of uptake into the DGT. Overall, this study indicated that Hg(II) associated with NOM passes into a DGT, however the transport is slowed in accordance with the diffusivity of the NOM to which the Hg(II) is associated. Thus, the Hg—NOM association and complex diffusivities need to be considered when relating DGT uptake to Hg porewater concentration. The results also suggest that Hg(II) associated with colloidal or larger particles of negligible diffusivity are unlikely to contribute significantly to DGT measurements.
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•Accurate interpretation of porewater Hg(II) concentrations by DGTs is needed.•Diffusion parameters were determined for labile Hg species and associated with NOM.•NOM-dominated porewater systems reduce average Hg diffusivity by a factor of 2–5.•Ultrafiltration can be used to determine apparent Hg binding to different size NOM.•A model of size dependent diffusivity describes apparent Hg diffusivity in DGTs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•First Southern Hemisphere record of end-Permian Hg reveals that Siberian Traps affected global Hg cycle.•Two new records indicate no global Hg anomaly during the protracted Early Triassic ...recovery.•First use of Hg isotopes with Early Triassic Hg chemostratigraphy.•A significant terrestrial Hg flux into the oceans resulted in less positive Δ199Hg values in Early Triassic samples.
The end-Permian mass extinction (EPME) at ∼252 Ma was the most severe extinction in the Phanerozoic. Marine ecosystems devastated by the EPME had a highly prolonged recovery, and did not substantially recover until after the Smithian–Spathian substage boundary (SSB) of the Lower Triassic (5 to 9 Ma after the EPME). While the Siberian Traps large igneous province (STLIP) has been invoked as the driver of the mass extinction, there remains controversy as to the cause of the protracted Early Triassic recovery; although renewed STLIP volcanism has been suggested. These previous studies though have drawn conclusions based on geochemical records of sediments deposited in northern latitude settings. To investigate the relationship between STLIP and extinction/recovery processes on a global base, we examined mercury chemostratigraphy, including mercury concentrations and isotopes, from high southern latitude and equatorial sections that span the Late Permian Changhsingian to Early Triassic Spathian substage successions; the Guryul Ravine section, Kashmir in northern India, and the Chaohu section in southern China. Organic and inorganic carbon-isotope data define the EPME horizon in the Chaohu section and the SSB in the Guryul Ravine section, respectively. Hg/TOC values are dramatically elevated approaching the EPME horizon and maintain high values until the lower Isarcicella Isarcica conodont zone, the base of which is believed to be the end of the mass extinction. In the stratigraphically overlying beds, Hg/TOC generally displays lower values with slight fluctuations through the two sections. These fluctuations are likely related to the increased terrestrial Hg influx associated with strong chemical weathering in the Early Triassic, as shown by a positive correlation between the contents of Hg and Al, and by less positive Δ199Hg values in Early Triassic samples. Our data, presenting the first Southern Hemisphere Hg record from Guryul Ravine, in combination with previous results, indicates that anomalous high mercury deposition at the EPME occurred globally. The generally positive Δ199Hg values at this time reflects atmospheric-derived Hg, consistent with a volcanic Hg source which we suggest indicates global impact of STLIP eruption. In contrast, there is no evidence for a global Hg/TOC anomaly during the protracted Early Triassic biotic recovery, suggesting that potentially renewed STLIP volcanism had only a northern hemisphere influence on the global Hg cycle. This more limited impact, may still have played a role in the delayed Early Triassic recovery.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Inherent radical/non-radical processes were analyzed for tetracycline degradation.•The critical role of metal–oxygen covalency and defects sites are analyzed.•Synergetic mechanism of ...dual active sites to PDS activation are declared.•Controllable synthesis of dual active sites CuyMn5-yOx/hG interfacial catalysts.•Removal of -CONH2 and C2-C3 sites ring opening are vital for TC degradation.
Tetracycline is a typical ecologically toxic antibiotic that easily causes environmental contamination. An attractive approach toward pollution control is the implementation of sulfate radical-based advanced oxidation processes (SO4·--AOPs), and in that regard, it is critical to generate and stabilize highly-oxidative species over an excellent catalytic system to degrade tetracycline antibiotics. In this work, we investigated a strategy for employing a synergetic role of CuOx to enlarge the MnsbnO covalency and tailor defect sites, which could enhance the intrinsic activity of CuyMn5-yOx/hG catalysts for boosted peroxydisulfate (PDS) activation and tetracycline degradation via radical and nonradical processes. Comprehensive characterization revealed that MnO bonds weakened, while the CuyMn5-yOx redox cycling provided the main active center for PDS activation by radical processes. Moreover, abundant defect sites of the carbon-based co-catalyst promoted the adsorption of PDS and tetracycline and, thus, their catalysis via nonradical processes. Structural characterization indicated that Cu2.5Mn2.5Ox/hG catalysts prepared using the solid-phase method significantly increased the ratio of defects sites and enlarged the MnsbnO covalency, enhancing PDS activation. Particularly, OH· and SO4·- radicals were critical reactive oxygen species, Mn(Cu) sbnO bond weakening, and defects are the key activation sites. Furthermore, degradation pathways, the toxicity of intermediate species, and the reaction mechanisms of the tetracycline degradation catalyzed by CuyMn5-yOx/hG were determined. Removing CONH2 functional groups and the C2-C3 structural sites ring-opening played a vital role in tetracycline degradation. The Cu2.5Mn2.5Ox/hG catalyst was demonstrated to be effective in tetracycline degradation with a low environmental impact, and our findings provide valuable novel insights for further development of efficient SO4·--AOPs catalysts.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Plant species for accumulating Hg studied in the past 20 years are reviewed.•The type of Hg accelerators studied in the past 20 years are reviewed.•Transgenic plants for accumulating studied in the ...past 20 years are reviewed.•Phytoremediation and assisted phytoremediation are compared and discussed.•Some significant future perspectives are proposed.
Mercury (Hg) and its compounds are one of the most dangerous environmental pollutants and Hg pollution exists in soils in different degrees over the world. Phytoremediation of Hg-contaminated soils has attracted increasing attention for the advantages of low investment, in-situ remediation, potential economic benefits and so on. Searching for the hyperaccumulator of Hg and its application in practice become a research hotspot. In this context, we review the current literatures that introduce various experimental plant species for accumulating Hg and aided techniques improving the phytoremediation of Hg-contaminated soils. Experimental plant species for accumulating Hg and accumulation or translocation factor of Hg are listed in detail. The translocation factor (TF) is greater than 1.0 for some plant species, however, the bioaccumulation factor (BAF) is greater than 1.0 for Axonopus compressus only. Plant species, soil properties, weather condition, and the bioavailability and heterogeneity of Hg in soils are the main factors affecting the phytoremediation of Hg-contaminated soils. Chemical accelerator kinds and promoting effect of chemical accelerators for accumulating and transferring Hg by various plant species are also discussed. Potassium iodide, compost, ammonium sulphate, ammonium thiosulfate, sodium sulfite, sodium thiosulfate, hydrochloric acid and sulfur fertilizer may be selected to promote the absorption of Hg by plants. The review introduces transgenic gene kinds and promoting effect of transgenic plants for accumulating and transferring Hg in detail. Some transgenic plants can accumulate more Hg than non-transgenic plants. The composition of rhizosphere microorganisms of remediation plants and the effect of rhizosphere microorganisms on the phytoremediation of Hg-contaminated soils are also introduced. Some rhizosphere microorganisms can increase the mobility of Hg in soils and are beneficial for the phytoremediation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•C, N and Hg isotopes and trace element stratigraphies across the OST are investigated.•Synchronous Hg/TOC spike and Δ199Hg ∼ 0 ‰ recorded coeval volcanism in the LOME 2.•Odd-MIF Hg ...isotope pattern shaped by volcanism/glaciation /sea-level fall in LOME 2.
Global geological processes that occurred during the Ordovician–Silurian transition (OST) were investigated exploring sections from the Argentine Precordillera (Cerro La Chilca, Baños de Talacasto and Villicum) which were deposited close to polar zones of Gondwana during the oldest Phanerozoic glaciation. C-N-Hg isotopes and redox-sensitive trace metal chemostratigraphy allowed to assess the relative importance of volcanism, glaciation, post-glacial sedimentation and extinction events during the OST. At Cerro La Chilca and Baños de Talacasto sections, Katian and early Hirnantian strata are missing. Hirnantian and Rhuddanian strata occur in the all three sections. At Cerro La Chilca, coeval positive δ13Corg shift, Hg spike and Δ199Hg ∼ 0 ‰ were recorded in the Sandbian Los Azules Formation, suggesting volcanic Hg loading. Coeval Hg/TOC spikes at the Baños de Talacasto and Villicum sections and Δ199Hg ∼ 0 ‰ in the late Hirnantian (M. persculptus Zone) recorded the second pulse of the Late Ordovician mass extinction (LOME 2), for which volcanism was postulated as the cause of warming and anoxia. Another Hg/TOC spike in the early Rhuddanian at Baños de Talacasto and Villicum is coeval with slightly positive Δ199Hg values, an enrichment related, perhaps, to an enhanced continental runoff that followed the Late Ordovician glacial cycle (LOGC-3). At the Cerro La Chilca, positive δ15N values in the Sandbian suggest less intense water-column denitrification while negative nitrogen isotope values in the LOME 2 period indicate denitrifying conditions. At the Baños de Talacasto and Villicum sections, sea-level fluctuations and nitrogen upwelling helped shaping the δ15N pathway within the LOME 2 and early Rhuddanian intervals, with negative δ15N values attesting that conditions became less reducing closer to the OST. The odd-MIF Hg isotope pattern within the LOME 2 time interval was probably induced by coeval volcanism, glaciation and sea-level fall, and in the early Rhuddanian by deglaciation and sea-level rise.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This Special Issue reprint includes one review and fifteen research articles. The review by Palyanova et al. (2023) summarized the available information on the palladian gold and proposed classifying ...the types of deposits based on the fineness, content, and set of impurities in palladian gold and minerals intergrown with it. Fifteen articles focused on the typomorphic features of native gold from gold deposits in Russia, India, Chile, Scotland, and Canada. This Special Issue aims to identify and generalize the reasons for variations in the compositions of native gold. I hope all the articles in this Special Issue will be helpful and valuable resources for anyone who is interested in native gold and gold deposits. I thank the Authors and Reviewers for their efforts and contributions. I am also grateful to the Editor-in-Chief, Editors and Assistant Editors of Minerals for their help.
Fluorescent chitosan-based hydrogel for the selective detection and adsorption of Hg2+/Hg+ in aqueous environment was prepared through three-step synthesis strategy. NO2-Boron-dipyrrolemethene ...(BODIPY) was prepared firstly, and then the -NO2 group was reduced to -NH2 group. Finally, the NH2-BODIPY was introduced to chitosan by Schiff base formation reaction through bi-aldehyde. Eventually, fluorescent chitosan hydrogel was obtained. The as-prepared fluorescent hydrogel probe could detect Hg2+/Hg+ through PET mechanism with the detection limit of 0.3 μM. The recognition site which combines Hg2+/Hg+ is CN, it is just formed in the reaction with chitosan and the amino group on BODIPY. Adsorption capacity of the fluorescent hydrogel is 121 mg·g−1, which is almost seven times of the original chitosan. The isotherm and kinetics of Hg2+/Hg+ removal follows Langmuir isotherm and pseudo-second order kinetics, respectively. Besides, a series of fluorescent hydrogels were prepared to compare the elasticity, hydropHilicity, fluorescence intensity and adsorption capacity.
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•Chitosan-based fluorescent hydrogel probe was prepared.•The hydrogel probe could selectively recognize Hg2+/Hg+ with the LOD of 0.3 μM•The hydrogel is also an effective adsorbent of Hg2+•The hydrogel exhibits better elasticity, hydrophilicity and adsorption capacity
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
