The Experts below are selected from a list of 2103 Experts worldwide ranked by ideXlab platform

Tong Zhang - One of the best experts on this subject based on the ideXlab platform.

  • microbial methylation potential of Mercury Sulfide particles dictated by surface structure
    Nature Geoscience, 2021
    Co-Authors: Li Tian, Wenyu Guan, Wei Chen, Pedro J J Alvarez, Tong Zhang
    Abstract:

    Environmental contamination by Mercury in its organometallic form, methylMercury, remains a major global concern due to its neurotoxicity, environmental persistence and biomagnification through the food chain. Accurate prediction of Mercury methylation cannot be achieved based on aqueous speciation alone, and there remains limited mechanistic understanding of microbial methylation of particulate-phase Mercury. Here we assess the time-dependent changes in structural properties and methylation potential of nanoparticulate Mercury using microscopic and spectroscopic analyses, microcosm bioassays and theoretical calculations. We show that the methylation potential of a Mercury Sulfide mineral ubiquitous in contaminated soils and sediments (nanoparticulate metacinnabar) is determined by its crystal structure. MethylMercury production increases when more of nano-metacinnabar’s exposed surfaces occur as the (111) facet, due to its large binding affinity to methylating bacteria, likely via the protein transporter responsible for Mercury cellular uptake prior to methylation. During nanocrystal growth, the (111) facet diminishes, lessening methylation of nano-metacinnabar. However, natural ligands alleviate this process by preferentially adsorbing to the (111) facet, and consequently hinder natural attenuation of Mercury methylation. We show that the methylation potential of nanoparticulate Mercury is independent of surface area. Instead, the nano-scale surface structure of nanoparticulate Mercury is crucial for understanding the environmental behaviour of Mercury and other nutrient or toxic soft elements. The environmental behaviour of Mercury and other toxic soft elements is in part dictated by the surface structure of nanoparticulates, according to a combination of microcosm bioassays and theoretical calculations.

  • effects of extracellular polymeric substances on the formation and methylation of Mercury Sulfide nanoparticles
    Environmental Science & Technology, 2020
    Co-Authors: Zhanhua Zhang, Wenshan Chen, Wenyu Guan, Yuxiao Cui, Tong Zhang
    Abstract:

    Growing evidence has suggested that microbial biofilms are potential environmental "hotspots" for the production and accumulation of a bioaccumulative neurotoxin, methylMercury. Here, we demonstrate that extracellular polymeric substances (EPS), the main components of biofilm matrices, significantly interfere with Mercury Sulfide precipitation and lead to the formation of nanoparticulate metacinnabar available for microbial methylation, a natural process predominantly responsible for the environmental occurrence of methylMercury. EPS derived from Mercury methylating bacteria, particularly Desulfovibrio desulfuricans ND132, substantially increase the methylation potential of nanoparticulate Mercury. This is likely due to the abundant aromatic biomolecules in EPS that strongly interact with Mercury Sulfide via inner-sphere complexation and consequently enhance the short-range structural disorder while mitigating the aggregation of nanoparticulate Mercury. The EPS-elevated bioavailability of nanoparticulate Mercury to D. desulfuricans ND132 is not induced by dissolution of these nanoparticles in aqueous phase, and may be dictated by cell-nanoparticle interfacial reactions. Our discovery is the first step of mechanistically understanding methylMercury production in biofilms. These new mechanistic insights will help incorporate microbial EPS and particulate-phase Mercury into Mercury methylation models, and may facilitate the assessment of biogeochemical cycling of other nutrient or toxic elements driven by EPS-producing microorganisms that are prevalent in nature.

  • effects of extracellular polymeric substances on the formation and methylation of Mercury Sulfide nanoparticles
    Environmental Science & Technology, 2020
    Co-Authors: Zhanhua Zhang, Wenshan Chen, Wenyu Guan, Yuxiao Cui, Tong Zhang
    Abstract:

    Growing evidence has suggested that microbial biofilms are potential environmental “hotspots” for the production and accumulation of a bioaccumulative neurotoxin, methylMercury. Here, we demonstrat...

  • microbial and thiosulfate mediated dissolution of Mercury Sulfide minerals and transformation to gaseous Mercury
    Frontiers in Microbiology, 2015
    Co-Authors: Adiari I Vazquezrodriguez, Tong Zhang, Colleen M Hansel, Carl H Lamborg, Cara M Santelli, Samuel M Webb, Scott C Brooks
    Abstract:

    Mercury (Hg) is a toxic heavy metal that poses significant environmental and human health risks. Soils and sediments, where Hg can exist as the Hg Sulfide mineral metacinnabar (β-HgS), represent major Hg reservoirs in aquatic environments. Metacinnabar has historically been considered a sink for Hg in all but severely acidic environments, and thus disregarded as a potential source of Hg back to aqueous or gaseous pools. Here, we conducted a combination of field and laboratory incubations to identify the potential for metacinnabar as a source of dissolved Hg within near neutral pH environments and the underpinning (a)biotic mechanisms at play. We show that the abundant and widespread sulfur-oxidizing bacteria of the genus Thiobacillus extensively colonized metacinnabar chips incubated within aerobic, near neutral pH creek sediments. Laboratory incubations of axenic Thiobacillus thioparus cultures led to the release of metacinnabar-hosted Hg(II) and subsequent volatilization to Hg(0). This dissolution and volatilization was greatly enhanced in the presence of thiosulfate, which served a dual role by enhancing HgS dissolution through Hg complexation and providing an additional metabolic substrate for Thiobacillus. These findings reveal a new coupled abiotic-biotic pathway for the transformation of metacinnabar-bound Hg(II) to Hg(0), while expanding the Sulfide substrates available for neutrophilic chemosynthetic bacteria to Hg-laden Sulfides. They also point to mineral-hosted Hg as an underappreciated source of gaseous elemental Hg to the environment.

  • microbial and thiosulfate mediated dissolution of Mercury Sulfide minerals and transformation to gaseous Mercury
    Frontiers in Microbiology, 2015
    Co-Authors: Adiari I Vazquezrodriguez, Tong Zhang, Colleen M Hansel, Carl H Lamborg, Cara M Santelli, Samuel M Webb, Scott C Brooks
    Abstract:

    Mercury (Hg) is a toxic heavy metal that poses significant human and environmental health risks. Soils and sediments, where Hg can exist as the Hg Sulfide mineral metacinnabar (β-HgS), represent major Hg reservoirs in aquatic environments. Metacinnabar has historically been considered a sink for Hg in all but severely acidic environments, and thus disregarded as a potential source of Hg back to aqueous or gaseous pools. Here, we conducted a combination of field and laboratory incubations to identify the potential for metacinnabar as a source of dissolved Hg within near neutral pH environments and the underpinning (a)biotic mechanisms at play. We show that the abundant and widespread sulfur-oxidizing bacterium Thiobacillus extensively colonized metacinnabar chips incubated within aerobic, near neutral pH creek sediments. Laboratory incubations of axenic Thiobacillus cultures lead to the release of metacinnabar-hosted Hg(II) and subsequent volatilization to Hg(0). This dissolution and volatilization was greatly enhanced in the presence of the sulfur intermediate, thiosulfate, which served a dual role by enhancing HgS dissolution and providing an additional metabolic substrate for Thiobacillus. These findings reveal a new coupled abiotic-biotic pathway for the transformation of metacinnabar-bound Hg(II) to Hg(0), while expanding the Sulfide substrates available for neutrophilic chemosynthetic bacteria to Hg-laden Sulfides. They also point to mineral-hosted Hg as an underappreciated source of gaseous elemental Hg to the environment.

Scott C Brooks - One of the best experts on this subject based on the ideXlab platform.

  • microbial and thiosulfate mediated dissolution of Mercury Sulfide minerals and transformation to gaseous Mercury
    Frontiers in Microbiology, 2015
    Co-Authors: Adiari I Vazquezrodriguez, Tong Zhang, Colleen M Hansel, Carl H Lamborg, Cara M Santelli, Samuel M Webb, Scott C Brooks
    Abstract:

    Mercury (Hg) is a toxic heavy metal that poses significant environmental and human health risks. Soils and sediments, where Hg can exist as the Hg Sulfide mineral metacinnabar (β-HgS), represent major Hg reservoirs in aquatic environments. Metacinnabar has historically been considered a sink for Hg in all but severely acidic environments, and thus disregarded as a potential source of Hg back to aqueous or gaseous pools. Here, we conducted a combination of field and laboratory incubations to identify the potential for metacinnabar as a source of dissolved Hg within near neutral pH environments and the underpinning (a)biotic mechanisms at play. We show that the abundant and widespread sulfur-oxidizing bacteria of the genus Thiobacillus extensively colonized metacinnabar chips incubated within aerobic, near neutral pH creek sediments. Laboratory incubations of axenic Thiobacillus thioparus cultures led to the release of metacinnabar-hosted Hg(II) and subsequent volatilization to Hg(0). This dissolution and volatilization was greatly enhanced in the presence of thiosulfate, which served a dual role by enhancing HgS dissolution through Hg complexation and providing an additional metabolic substrate for Thiobacillus. These findings reveal a new coupled abiotic-biotic pathway for the transformation of metacinnabar-bound Hg(II) to Hg(0), while expanding the Sulfide substrates available for neutrophilic chemosynthetic bacteria to Hg-laden Sulfides. They also point to mineral-hosted Hg as an underappreciated source of gaseous elemental Hg to the environment.

  • microbial and thiosulfate mediated dissolution of Mercury Sulfide minerals and transformation to gaseous Mercury
    Frontiers in Microbiology, 2015
    Co-Authors: Adiari I Vazquezrodriguez, Tong Zhang, Colleen M Hansel, Carl H Lamborg, Cara M Santelli, Samuel M Webb, Scott C Brooks
    Abstract:

    Mercury (Hg) is a toxic heavy metal that poses significant human and environmental health risks. Soils and sediments, where Hg can exist as the Hg Sulfide mineral metacinnabar (β-HgS), represent major Hg reservoirs in aquatic environments. Metacinnabar has historically been considered a sink for Hg in all but severely acidic environments, and thus disregarded as a potential source of Hg back to aqueous or gaseous pools. Here, we conducted a combination of field and laboratory incubations to identify the potential for metacinnabar as a source of dissolved Hg within near neutral pH environments and the underpinning (a)biotic mechanisms at play. We show that the abundant and widespread sulfur-oxidizing bacterium Thiobacillus extensively colonized metacinnabar chips incubated within aerobic, near neutral pH creek sediments. Laboratory incubations of axenic Thiobacillus cultures lead to the release of metacinnabar-hosted Hg(II) and subsequent volatilization to Hg(0). This dissolution and volatilization was greatly enhanced in the presence of the sulfur intermediate, thiosulfate, which served a dual role by enhancing HgS dissolution and providing an additional metabolic substrate for Thiobacillus. These findings reveal a new coupled abiotic-biotic pathway for the transformation of metacinnabar-bound Hg(II) to Hg(0), while expanding the Sulfide substrates available for neutrophilic chemosynthetic bacteria to Hg-laden Sulfides. They also point to mineral-hosted Hg as an underappreciated source of gaseous elemental Hg to the environment.

Joel D Blum - One of the best experts on this subject based on the ideXlab platform.

  • Chronic Mercury exposure in Late Neolithic/Chalcolithic populations in Portugal from the cultural use of cinnabar
    2020
    Co-Authors: Steven D Emslie, Rebecka L Brasso, William P Patterson, Antonio Carlos Valera, Ashley Mckenzie, Ana Maria Silva, James D Gleason, Joel D Blum
    Abstract:

    Cinnabar is a natural Mercury Sulfide (HgS) mineral of volcanic or hydrothermal origin that is found worldwide. It has been mined prehistorically and historically in China, Japan, Europe, and the Americas to extract metallic Mercury (Hg 0 ) for use in metallurgy, as a medicinal, a preservative, and as a red pigment for body paint and ceramics. Processing cinnabar via combustion releases Hg 0 vapor that can be toxic if inhaled. Mercury from cinnabar can also be absorbed through the gut and skin, where it can accumulate in organs and bone. Here, we report moderate to high levels of total Mercury (THg) in human bone from three Late Neolithic/Chalcolithic (5400-4100 B.P.) sites in southern Portugal that were likely caused by cultural use of cinnabar. We use light stable isotope and Hg stable isotope tracking to test three hypotheses on the origin of Mercury in this prehistoric human bone. We traced Hg in two individuals to cinnabar deposits near Almadén, Spain, and conclude that use of this mineral likely caused mild to severe Mercury poisoning in the prehistoric population. Our methods have applications to bioarchaeological investigations worldwide, and for tracking trade routes and mobility of prehistoric populations where cinnabar use is documented

  • chronic Mercury exposure in late neolithic chalcolithic populations in portugal from the cultural use of cinnabar
    Scientific Reports, 2015
    Co-Authors: Steven D Emslie, Rebecka L Brasso, William P Patterson, Antonio Carlos Valera, Ashley Mckenzie, Ana Maria Silva, James D Gleason, Joel D Blum
    Abstract:

    Cinnabar is a natural Mercury Sulfide (HgS) mineral of volcanic or hydrothermal origin that is found worldwide. It has been mined prehistorically and historically in China, Japan, Europe, and the Americas to extract metallic Mercury (Hg(0)) for use in metallurgy, as a medicinal, a preservative, and as a red pigment for body paint and ceramics. Processing cinnabar via combustion releases Hg(0) vapor that can be toxic if inhaled. Mercury from cinnabar can also be absorbed through the gut and skin, where it can accumulate in organs and bone. Here, we report moderate to high levels of total Mercury (THg) in human bone from three Late Neolithic/Chalcolithic (5400-4100 B.P.) sites in southern Portugal that were likely caused by cultural use of cinnabar. We use light stable isotope and Hg stable isotope tracking to test three hypotheses on the origin of Mercury in this prehistoric human bone. We traced Hg in two individuals to cinnabar deposits near Almaden, Spain, and conclude that use of this mineral likely caused mild to severe Mercury poisoning in the prehistoric population. Our methods have applications to bioarchaeological investigations worldwide, and for tracking trade routes and mobility of prehistoric populations where cinnabar use is documented.

Horst Weller - One of the best experts on this subject based on the ideXlab platform.

  • preparation characterization and photophysics of the quantum dot quantum well system cadmium Sulfide Mercury Sulfide cadmium Sulfide
    The Journal of Physical Chemistry, 1994
    Co-Authors: Alf Mews, Alexander Eychmueller, Michael Giersig, Detlef Schooss, Horst Weller
    Abstract:

    The synthetic procedure, the characterization, and some photophysical properties of a quantum dot quantum well (QDQW) system are described in detail. The novel structures prepared via wet chemical methods consist of a core of size-quantized CdS and a well of 1-3 monolayers of HgS capped by 1-5 monolayers of CdS acting as the outermost shell. Additionally, theoretical calculations based on the effective mass approximation appropriate to describe the 1s-1s electronic transition of the composite particles are presented

  • chemistry and photophysics of mixed cadmium Sulfide Mercury Sulfide colloids
    The Journal of Physical Chemistry, 1993
    Co-Authors: A. Haesselbarth, Alexander Eychmueller, R. Eichberger, Michael Giersig, Alf Mews, Horst Weller
    Abstract:

    Some interesting phenomena have been described recently and attempts were made to understand them mechanistically. The keywords of these studies are, for example, excitonic, trapped, and delayed fluorescence.10-14 Beyond that, attention has been drawn to nonlinear optical effects,'s20 transitions to higher excited electron transfer from the conduction band of CdS to quenching molecule^^^-^^ or from one colloidal particle to others such as AgI," ZnO,= AB~S,~~ or solid, and colloidal Ti02.31J2,3436 CdS is a very attractive model substance due to its stability, easy preparation and handling, and last, but not least, its distinct band gap that enables one to easily detect a number of optical properties. All the performed experiments underline the importance of the surface condition of the respective CdS particles. This is due to their very small size

Pavel Ginzburg - One of the best experts on this subject based on the ideXlab platform.

  • circular dichroism enhancement in plasmonic nanorod metamaterials
    Optics Express, 2018
    Co-Authors: Daniel Vestler, Ivan I Shishkin, Egor A Gurvitz, Mazhar E Nasir, Assaf Benmoshe, Alexey P Slobozhanyuk, Alexey V Krasavin, Tatyana Levibelenkova, Alexander S Shalin, Pavel Ginzburg
    Abstract:

    Optical activity is a fundamental phenomenon originating from the chiral nature of crystals and molecules. While intrinsic chiroptical responses of ordinary chiral materials to circularly polarized light are relatively weak, they can be enhanced by specially tailored nanostructures. Here, nanorod metamaterials, comprising a dense array of vertically aligned gold nanorods, is shown to provide a significant enhancement of the circular dichroism response of an embedded material. A nanorod composite, acting as an artificial uniaxial crystal, is filled with chiral Mercury Sulfide nanocrystals embedded in a transparent polymer. The metamaterial, being inherently achiral, enables optical activity enhancement or suppression. Unique properties of inherently achiral structures to tailor optical activities pave a way for flexible characterization of optical activity of molecules and nanocrystal-based compounds.