Hg Compounds Research Articles

Investigating how H2S can alter the interactions between Hg0 and corroded steel surfaces to guide future decommissioning projects

Many oil and gas developments will soon be decommissioned and, knowledge on the accumulation of mercury (Hg), throughout offshore infrastructure is limited. Any release of Hg could have a detrimental impact on marine ecosystems. To bridge this knowledge gap, a fractionation approach was taken on steel samples exposed to Hg0 and H2S, separating Hg compounds removed from the surface into polar, non-polar and insoluble fractions. Hg0 reacted on corroded surfaces to form several compounds, over 50 % of which were removed by seawater. This suggests that pipelines on the seabed could release a dramatic amount of Hg into the sea if they are left in place. Furthermore, a Cu-Hg amalgam, was identified to be a dominant species, by a combination of XFM, XANES and LA-ICP-TOFMS. Seawater-soluble and amalgam-bound Hg were present regardless of co-exposure to H2S. When H2S was present Hg nanoparticles accounted for up to 1 % of the total Hg on the steel. This investigation has shown that the Hg speciation on the surfaces of pipelines is complex and future decommissioning strategies should consider a range of Hg species beyond only Hg0 and metacinnabar (β-HgS), all of which could interact with biota and impact Hg biomagnification through the marine the food web.

Exploring mercury detoxification in fish: The role of selenium from tuna byproduct diets for sustainable aquaculture

Exposure to mercury (Hg) through fish consumption poses significant environmental and public health risks, given its status as one of the top ten hazardous chemicals. Aquaculture is expanding, driving a surge in demand for sustainable aquafeeds. Tuna byproducts, which are rich in protein, offer potential for aquafeed production, yet their use is challenged by the high content of heavy metals, particularly Hg. However, these byproducts also contain elevated levels of selenium (Se), which may counteract Hg adverse effects. This study examines the fate of dietary Hg and Se in an aquaculture model fish. Biomolecular speciation analyses through hyphenated analytical approaches were conducted on the water-soluble protein fraction of key organs of juvenile rainbow trout (Oncorhynchus mykiss) exposed to various combinations of Hg and Se species, including diets containing tuna byproducts, over a six-month period. The findings shed light on the dynamics of Hg and Se compounds in fish revealing potential Hg detoxification mechanisms through complexation with Hg-biomolecules, such as cysteine, glutathione, and metallothionein. Furthermore, the trophic transfer of selenoneine is demonstrated, revealing novel opportunities for sustainable aquafeed production. Understanding the interactions between Hg and Se in aquaculture systems is crucial for optimizing feed formulations and mitigating environmental risks. This research contributes to the broader goal of advancing sustainable practices in aquaculture while addressing food security challenges.

Efficient adsorption and desorption of elemental mercury by ordered mesoporous cerium oxide nanoparticles derived from Ce-based metal–organic frameworks

Metal oxide-based adsorbents not only exhibit effective elemental mercury (Hg0) removal capacity but also offer suitability for wet desorption, which is a green treatment method to avoid secondary contamination of deactivated adsorbents. Nevertheless, the limited dispersing capacity of the carrier restricts the loading of active substances, hindering further enhancement of adsorption capacity. The pore structure of adsorbent is also a key factor for wet desorption. In this work, we synthesized a hollow cerium-based metal–organic framework (Ce-mesoMOF) as a sacrificial precursor to obtain ordered mesoporous cerium oxide (OM-CeO₂) via a mesoporous genetic pyrolysis-oxidation mechanism. OM-CeO2 inherits the excellent structural properties of mesoporous MOF with better catalytic activity, exhibiting strong adsorption capacity in various atmospheres (97.6 % in pure N2, 98.8 % in N2 + H2S). Wet desorption of Hg compounds and reduction of the active site can be synergized in Na2S2O3 solution. The octahedral structure with an ordered mesoporous shell greatly facilitates the mass transfer process, as evidenced by the strong adsorption capacity and fast kinetic parameters of OM-CeO2. Density functional theory analysis reveals that the conversion reaction of adsorbed Hg has a low energy barrier on the pyrolytic-oxidized OM-CeO2 and the inhibitory effect of reactive S for Hg0 adsorption transforms into a facilitating effect. This study leverages the structural advantages of ordered mesoporous MOFs in the field of Hg adsorption and imparts reactivity through modification for efficient adsorption–desorption.

Towards Construction of the “Periodic Table” of 1-Methylbenzotriazole

Metal complexes of benzotriazole-type ligands continue to attract the intense interest of many inorganic chemistry groups around the world for a variety of reasons, including their aesthetically beautiful structures, physical properties and applications. 1-methylbenzotriazole (Mebta) is the N-substituted archetype of the parent 1H-benzotriazole. The first attempt to build a “periodic table” of Mebta, which includes its complexes with several metal ions, is described in this work. This, at first glance, trivial ligand has led to interesting results in terms of the chemistry, structures and properties of its metal complexes. This work reviews the to-date published coordination chemistry of Mebta with Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(I), Cu(II), Zn(II), Pd(II), Au(I) and {UVIO2}2+, with emphasis on their preparations, reactivity, structures and properties. Unpublished results from our group comprising other Co(II), Ni(II), Cu(II) and Zn(II) complexes, as well as Cd(II), Hg(II), Ag(I), In(III) and Sn(IV) ones are briefly reported. Mebta can also provide access to 1D and 3D heterometallic thiocyanato-bridged Co(II)/Hg(II) and Ni(II)/Hg(II) compounds. In almost all cases, Mebta behaves as a monodentate ligand with the nitrogen of position 3 of the azole ring as the donor atom. However, there are two copper complexes in which this molecule adopts a bidentate bridging coordination behavior. Our efforts to complete the “periodic table” of Mebta are continued.

Mercury compound distribution and stable isotope composition in the different compartments of seabird eggs: The case of three species breeding in East Greenland

Mercury (Hg) is a toxic contaminant of global concern and the impact on Arctic ecosystems, particularly in seabirds, is critical due to large-scale Hg transport towards polar regions and its biomagnification in marine trophic systems. While the adverse effects of Hg on reproductive processes in seabirds are established, the understanding of Hg maternal transfer pathways and their control on Hg reproductive toxicity is limited. The combination of Hg compounds speciation (inorganic mercury and monomethylmercury MMHg) and Hg stable isotope composition in the different egg compartments (yolk, albumen, membrane, and shell) before embryo development was investigated to provide information on (i) Hg maternal transfer mechanisms, (ii) influence of egg biochemical composition on Hg organotropism and (iii) proxies of inputs of Hg contamination. Eggs of three seabird species (the common eider, the black-legged kittiwake and the little auk) collected within the same breeding period (summer 2020) in East Greenland were investigated. For all seabirds, albumen and membrane, the most protein-rich compartments, were the most contaminated (from 1.2 to 2.7 μg g−1 for albumen and from 0.3 to 0.7 μg g−1 for membrane). In these two compartments, more than 82% of the total Hg amount was in the form of MMHg. Additionally, mass-dependent fractionation values (δ202Hg) were higher in albumen and membrane in the three species. This result was mainly due the organotropism of MMHg as influenced by the biochemical properties and chemical binding affinity of these proteinous compartments. Among the different egg compartments, individuals and species, mass-independent fractionation values were comparable (mean ± sd were 0.99 ± 0.11‰, 0.78 ± 0.11‰, 0.03 ± 0.05‰, 0.04 ± 0.10‰ for Δ199Hg, Δ201Hg, Δ200Hg and Δ204Hg, respectively). We conclude that initial MMHg accumulated in the three species originated from Arctic environmental reservoirs exhibiting similar and low photodemethylation extent. This result suggests a unique major source of MMHg in those ecosystems, potentially influenced by sea ice cover.

Effect of C-Cl functional groups on adsorption and desorption of elemental mercury over an ordered mesoporous carbon modified with C-Cl functional groups

Wet desorption presents an environmentally sustainable approach for the disposal of deactivated elemental mercury (Hg0) removal adsorbents. However, the prevalence of insoluble Hg compounds in the adsorption products poses a significant impediment to the wet desorption process. In this work, an ordered mesoporous carbon modified with C-Cl functional groups (OMC-Cl) was synthesized via the evaporation-induced self-assembly (EISA) method. It has a high specific surface area (∼630 m2/g), large pore volume (∼0.64 cm3/g), and uniform pore size (∼22.0 nm). The presence of C-Cl functional groups provides a remarkable adsorption capacity to the adsorbent, exhibiting high adsorption efficiency in various adsorption atmospheres (96.8 % in pure N2; 91.7 % in N2 + H2S) and promoting the prevalence of soluble HgCl2 in the adsorption product. Density functional theory analysis has elucidated that the C-Cl functional groups exerted inhibitory effects on the formation of HgO and HgS mainly by weakening the adsorption process of Hg0 on C = O and C-S. The desorption efficiencies of adsorption products in the above atmospheres in HCl solution (0.5 mol/L) achieved 95.4 % and 81.3 %, respectively. The high concentration of H+ ions serves to prevent the re-adsorption of Hg2+ by the -SH generated during the adsorption process. Furthermore, the adsorbent desorbed in HCl solution manifests substantial potential for recyclability. This study introduces a novel approach for efficient wet desorption in terms of designing active sites to modulate the adsorption products and pore structures to facilitate mass transfer.

A review on the principles of Rasa Shastra in Indian System of Medicine and its homology with Modern Chemical Processes

Ayurveda medicine is one of the oldest holistic healing sciences it was developed around 3000 years ago. Different branches of science were nurtured by it like biology, genetics, microbiology, clinical medicine, surgery, astronomic, pharmaceutics and metallurgy etc. In Ayurveda system of medicine various formulations have been described in the traditional literature, which adopted the processes which are quite similar to the processes used today in modern medicine for formulation of various dosage forms to get the desired effect for the optimum period. Science and technology in ancient and medieval India covered all the major branches of human knowledge and activities. In any, early civilization, metallurgy has remained an activity central to all civilizations from the Bronze Age and the Iron Age, to all other civilizations that followed. Various chemicals like common salt, alkali, borax, and compounds of elements Cu, Fe, Hg and Au were used as well as techniques for making of the alloys were also very common. The applicability of natural preservatives like oil, sugar, salt were also very much known in ancient time. However, the terms used as stated in traditional literature were not similar to the modern times. Also, the acidic and alcoholic fermented products were prepared very commonly.

A simplified spectrophotometric procedure for the detection of mercury ions

The recent brief work presents the results of attempts to simplify a procedure to detect dissolved Hg(II) compounds. It is based on the performance of a procedure, after the simplification of the prescription given in literature. The simplification was performed, to avoid the use of volatile organic compounds (VOC), such as the proposed in literature isoamyl alcohol. The present study aims to verify a simplified procedure, which does not require the use of mentioned VOC and detergents, like sodium dodecyl sulfate.

Toggling Stereochemical Activity through Interstitial Positioning of Cations between 2D V2O5 Double Layers.

The 5/6s2 lone-pair electrons of p-block cations in their lower oxidation states are a versatile electronic and geometric structure motif that can underpin lattice anharmonicity and often engender electronic and structural instabilities that underpin the function of active elements in nonlinear optics, thermochromics, thermoelectrics, neuromorphic computing, and photocatalysis. In contrast to periodic solids where lone-pair-bearing cations are part of the structural framework, installing lone-pair-bearing cations in the interstitial sites of intercalation hosts provides a means of a systematically modulating electronic structure through the choice of the group and the period of the inserted cation while preserving the overall framework connectivity. The extent of stereochemical activity and the energy positioning of lone-pair-derived mid-gap states depend on the cation identity, stoichiometry, and strength of anion hybridization. V2O5 polymorphs are versatile insertion hosts that can accommodate a broad range of s-, p-, and d-block cations. However, the insertion of lone-pair-bearing cations remains largely underexplored. In this article, we examine the implications of varying the 6s2 cations situated in interlayer sites between condensed [V4O10]n double layers. Systematic modulations of lattice distortions, electronic structure, and magnetic ordering are observed with increasing strength of stereochemical activity from group 12 to group 14 cations. We compare and contrast p-block-layered MxV2O5 (M = Hg, Tl, and Pb) compounds and map the significance of local off-centering arising from the stereochemical activity of lone-pair cations to the emergence of filled antibonding lone-pair 6s2-O 2p-hybridized mid-gap states mediated by second-order Jahn-Teller distortions. Crystallographic studies of cation coordination environments and the resulting modulation of V-V interactions have been used in conjunction with variable-energy hard X-ray photoelectron spectroscopy measurements, first-principles electronic structure calculations, and crystal orbital Hamilton population analyses to decipher the origins of stereochemical activity. Magnetic susceptibility measurements reveal antiferromagnetic signatures for all the three compounds. However, the differences in V-V interactions significantly affect the energy balance of the superexchange interactions, resulting in an ordering temperature of 160 and 260 K for Hg0.5V2O5 and δ-Tl0.5V2O5, respectively, as compared to 7 K for δ-Pb0.5V2O5. In δ-Pb0.5V2O5, the strong stereochemical activity of electron lone pairs and the resulting electrostatic repulsions enforce superlattice ordering, which strongly modifies the electronic localization patterns along the [V4O10] slabs, resulting in disrupted magnetic ordering and an anomalously low ordering temperature. The results demonstrate a versatile strategy for toggling the stereochemical activity of electron lone pairs to modify the electronic structure near the Fermi level and to mediate superexchange interactions.

Structural Characterization and Bonding Analysis of [Hg{Fe(CO)5}2]2+ [SbF6]-2.

The non-classical carbonyl complex [Hg{Fe(CO)5}2]2+ [SbF6]-2 is prepared by reaction of Hg(SbF6)2 and excess Fe(CO)5 in anhydrous HF. The single-crystal X-ray structure reveals a linear Fe-Hg-Fe moiety as well as an eclipsed conformation of the eight basal CO ligands. Interestingly, the Hg-Fe bond length of 2.5745(7) Å is relatively similar to the corresponding Hg-Fe bonds in literature-known [Hg{Fe(CO)4}2]2- dianions (2.52-2.55 Å), which intrigued us to analyze the bonding situation in both the dications and dianions with the energy decomposition analysis with natural orbitals for chemical valence (EDA-NOCV) method. Both species are best described as Hg(0) compounds, which are also confirmed by the shape of the HOMO-4 and HOMO-5 of the dication and dianion, respectively, in which the electron pair is located mainly at the Hg. Furthermore, for the dication and the dianion, the σ back-donation from Hg into the [Fe(CO)5]22+ or the [Fe(CO)4]22- fragment is the most dominant orbital interaction and surprisingly these interaction energies are also very similar even in absolute values. The fact that both iron-based fragments are missing two electrons explains their prominent σ-acceptor properties.

Ecosystem Mercury Recovery and Health Benefit Under the Minamata Convention in a Changing Climate

Mercury (Hg) is a toxic metal that can be released from natural and anthropogenic processes. Gaseous elemental Hg is the main form of Hg in the atmosphere with a long residence time, allowing its long-range transport and deposition at a global scale. The deposited Hg can be transformed into methylmercuy (MeHg), which bioaccumulates and biomagnifies in aquatic ecosystems and is a known developmental neurotoxin to humans. Chronic exposure in pregnant women via fish consumption, even at the modest levels, can impact intellectual development in infants, which is considered as a global environmental health issue. To protect human health and the environment, the Minamata Convention on Mercury, a legally binding international treaty, entered into force in 2017 to reduce anthropogenic emissions and releases of Hg and Hg compounds. With the enforcement of the Convention, anthropogenic Hg emissions and releases are projected to decrease in the foreseeable future, but the recovery of the ecosystem and mitigation of health impact from Hg pollution are expected to lag behind. In this paper, we provide a critical review on the processes affecting when and to which extent Hg-affected ecosystems will recover under the Minamata Convention in the context of climate change and associated human health benefit. Our review is organized around seven major scientific questions. These seven questions covered historical Hg change in the ecosystem, major factors and processes, and future assessment. The impact of implementation of Minamata Convention and climate change on Hg emission, atmospheric transportation and deposition, biota accumulation, and human exposure should be comprehensively evaluated. The Hg stable isotope tool and process-based integrated global model should be integrated together, which also should consider future global social-economic pathways and mitigation options. We hope that the knowledge gaps and potential tools identified will assist the understanding of global biogeochemical cycling of Hg, inform policy-making on mitigation and community adaptation, and support the effectiveness evaluation and future improvement of the Minamata Convention on Mercury.Graphical Abstract

Strategies for mercury speciation with single and multi-element approaches by HPLC-ICP-MS.

Mercury (Hg) and its compounds are highly toxic for humans and ecosystems, and their chemical forms determine both their behavior and transportation as well as their potential toxicity for human beings. Determining the various species of an element is therefore more crucial than understanding its overall concentration in samples. For this reason, several studies focus on the development of new analytical techniques for the identification, characterization, and quantification of Hg compounds. Commercially available, hyphenated technology, such as HPLC-ICP-MS, supports the rapid growth of speciation analysis. This review aims to summarize and critically examine different approaches for the quantification of mercury species in different samples using HPLC-ICP-MS. The steps preceding the quantification of the analyte, namely sampling and pretreatment, will also be addressed. The scenarios evaluated comprehend single and multi-element speciation analysis to create a complete guide about mercury content quantification.

Development of selective mercury recovery technology by using iron iodide from waste sludge of non-ferrous metal smelting process

The waste sludge from non-ferrous metal smelter contains high concentrations of mercury (Hg), arsenic (As) and sulfur (S). The Article 11 of the Minamata Convention on Mercury mandates the recovery of Hg before the disposal stage of Hg waste. However, As compounds have similar boiling points with Hg compounds, and they are considered interfering substances in the recovery of Hg. Moreover, a high concentration of S requires significant energy to volatilize Hg. This study examined the optimal conditions for selective recovery of Hg and energy reduction by introducing FeI2 as an additive during thermal treatment. Thermogravimetric analysis was utilized to evaluate the conversion of HgS to HgI2 under the influence of FeI2. The optimal conditions for thermal treatment such as temperature, treatment time, and molar ratio of [Hg]:[As]:[FeI2] were explored. The simulated waste indicated that the maximum separation efficiency of Hg was ∼95%, thereby allowing a selective separation of 81.5% of Hg from waste sludge with an Hg content of 0.33%, As content of 23.8%, and S content of 30.7%. Sequential extraction procedure was applied to evaluate the stability of Hg and As for residues. As a result, most Hg was vaporized and As was stabilized in sulfide, crystalline, and amorphous forms.

10-year time course of Hg and organic compounds in Augusta Bay: Bioavailability and biological effects in marine organisms.

In the last century, many Mediterranean coastal areas have been subjected to anthropogenic disturbances from industrial activities, uncontrolled landfills, shipyards, and high maritime traffic. The Augusta Bay (eastern Sicily, Italy) represents an example of a strongly impacted coastal environment with an elevated level of sediments contamination due to the presence of one of the largest European petrochemical plants, combined with an extensive commercial and military harbor. The most significant contaminants were represented by mercury (Hg) and hexachlorobenzene (HCB), derived from a former chlor-alkali plant, and other organic compounds like polycyclic aromatic hydrocarbons (PAHs) and polychlorobiphenyls (PCBs). Since the 1970s, Augusta Bay has become internationally recognized as a contaminated marine environment, although very little information is available regarding the temporal trend of contaminants bioavailability and biological impacts on aquatic organisms. In this study, the Hg and HCB concentrations were investigated over 10 years (from 2003 to 2013) in sediments and invertebrate and vertebrate organisms; these two contaminants' ecotoxicity was further evaluated at a biochemical and cellular level by analyzing the induction of organic biotransformation processes and DNA damages. The results showed high concentrations of Hg and HCB in sediments and their strong bioaccumulation in different species with significantly higher values than those measured in reference sites. This trend was paralleled by increased micronuclei frequency (DNA damage biomarker) and activity of the biotransformation system. While levels of chemicals in sediments remained elevated during the time course, their bioavailability and biological effects showed a gradual decrease after 2003, when the chlor-alkali plant was closed. Environmental persistence of Hg and HCB availability facilitates their bioaccumulation and affects the health status of marine organisms, with possible implications for environmental risk, pollutants transfer, and human health.

Effect of methylmercury on fetal neurobehavioral development: an overview of the possible mechanisms of toxicity and the neuroprotective effect of phytochemicals.

Methylmercury (MeHg) is a global environmental pollutant with neurotoxic effects. Exposure to MeHg via consumption of seafood and fish can severely impact fetal neurobehavioral development even when MeHg levels in maternal blood are as low as about 5μg/L, which the mother tolerates well. Persistent motor dysfunctions and cognitive deficits may result from trans-placental exposure. The present review summarizes current knowledge on the mechanisms of MeHg toxicity during the period of nervous system development. Although cerebellar Purkinje cells are MeHg targets, the actions of MeHg on thiol components in the neuronal cytoskeleton as well as on mitochondrial enzymes and induction of disturbances of glutamate signaling can impair extra-cerebellar functions, also at levels well tolerated by adult individuals. Numerous herbal substances possess neuroprotective effects, predominantly represented by natural polyphenolic molecules that might be utilized to develop natural drugs to alleviate neurotoxicity symptoms caused by MeHg or other Hg compounds.

Comparison of Biochemical Composition and Non-Volatile Taste Active Compounds of Back and Abdominal Muscles in Three Marine Perciform Fishes, Chromileptes altivelis, Epinephelus akaara and Acanthopagrus schlegelii.

Humpback grouper Chromileptes altivelis (HG), red-spotted grouper Epinephelus akaara (RG) and black seabream Acanthopagrus schlegelii (BS) are three popular perciform fishes with an increasingly important farming industry. The prices of BS are much lower than other grouper species; however, the differences in the nutritive values of these three perciform fishes with commercial specifications have not been reported. In this study, the biochemical composition and non-volatile taste active compounds of adult HG, RG and BS were investigated. Moisture contents in BS were significantly higher than in HG and RG (p < 0.05), and relatively lower crude protein contents in BS were observed. Lipid contents of back muscle were lower than that of abdomen muscle in the three fish species. C22:6n-3 (DHA) was the major poly-unsaturated fatty acid (PUFA) in HG and BS, while the main PUFA in RG was C18:2n-6. The total healthy omega-3 fatty acid (Σn-3) profiles in HG were the highest (24.08–24.59%), followed by RG (18.24–19.06%) and BS (13.63–15.91%) (p < 0.05). Glycine was the most abundant free amino acid (FAA) in HG and RG, while lysine was the major FAA in BS. Equivalent umami concentration (EUC) values in BS were the highest, followed by HG and RG (p < 0.05). Lactic acid and PO43− were the major organic acids and inorganic ions, respectively. In conclusion, HG and RG provided more protein and healthy omega-3 fatty acids than BS, while BS had a stronger umami taste according to the EUC values.

Rapid thermoscanning technique for direct analysis of mercury species in contaminated sediments: From pure compounds to real sample application

Mercury (Hg) in aquatic environments accumulates in sediments in several chemical forms, both inorganic and organic, which are often determined through time-consuming selective and sequential extraction procedures. Thermal desorption technique (pyrolysis) coupled with continuous determination by atomic absorption spectrometry (AAS) may be an easy-to-use alternative technique for the rapid identification and quantification of Hg species in the solid matrix. This technique is based on the gradual heating of a sample that releases Hg at different temperature intervals depending on its chemical form. Thus, a single Hg species that desorbs at a specific temperature may be identified via a thermogram of the sample.In this work, several commercial pure Hg compounds, natural Hg mineral species (red cinnabar, α-HgS) and one compound synthesised in the lab (α-FeOOHHg) were mixed with synthetic calcium carbonate (CaCO3), silica (SiO2) and natural matrices (silicate and carbonate marine sediments) which were then desorbed in order to determine the desorption peak temperatures corresponding to each Hg species. Moreover, possible interference caused by the matrix was also considered. The results obtained from 52 desorbed MIX samples displayed different desorption temperatures for the same Hg species depending on the matrix used. Indeed, Hg species mixed with synthetic SiO2 desorbed at a temperature lower than the same species mixed with synthetic CaCO3 with a difference of approximately 100 °C.The analytical approach was applied to selected coastal sediments from the Gulf of Trieste (Northern Adriatic Sea, Italy), contaminated by Hg from the five centuries of cinnabar (α-HgS) mining activity from Idrija (Slovenia), in order to identify the unknown Hg species. The results revealed the presence of two peaks with a distinct temperature of desorption (∼250 and 350 °C). The highest temperature corresponds to the mostly refractory red cinnabar (α-HgS) compound, whereas the lowest temperature is related to other species (e.g. β-HgS) that may also include Hg associated with more mobile and potentially bio-accessible species (e.g. α-FeOOHHg) if compared to α-HgS. This methodological approach is a rapid and cost-effective technique useful to preliminarily quantify more stable Hg species (mainly α-HgS), underlining the relevance in considering the chemical form of the element rather than merely the total concentration for simplifying the environmental management of Hg-contaminated sediments.

Thioredoxin Reductase Inhibitors as Potential Antitumors: Mercury Compounds Efficacy in Glioma Cells.

Glioblastoma multiforme (GBM) is the most aggressive and common form of glioma. GBM, like many other tumors, expresses high levels of redox proteins, such as thioredoxin (Trx) and thioredoxin reductase (TrxR), allowing tumor cells to cope with high levels of reactive oxygen species (ROS) and resist chemotherapy and radiotherapy. Thus, tackling the activity of these enzymes is a strategy to reduce cell viability and proliferation and most importantly achieve tumor cell death. Mercury (Hg) compounds are among the most effective inhibitors of TrxR and Trx due to their high affinity for binding thiols and selenols. Moreover, organomercurials such as thimerosal, have a history of clinical use in humans. Thimerosal effectively crosses the blood–brain barrier (BBB), thus reaching effective concentrations for the treatment of GBM. Therefore, this study evaluated the effects of thimerosal (TmHg) and its metabolite ethylmercury (EtHg) over the mouse glioma cell line (GL261), namely, the inhibition of the thioredoxin system and the occurrence of oxidative cellular stress. The results showed that both TmHg and EtHg increased oxidative events and triggered cell death primarily by apoptosis, leading to a significant reduction in GL261 cell viability. Moreover, the cytotoxicity of TmHg and ETHg in GL261 was significantly higher when compared to temozolomide (TMZ). These results indicate that EtHg and TmHg have the potential to be used in GBM therapy since they strongly reduce the redox capability of tumor cells at exceedingly low exposure levels.

Simultaneous measurements of Cr, Cd, Hg and Pb species in ng L−1 levels by interfacing high performance liquid chromatography and inductively coupled plasma mass spectrometry

Toxicity, mobility, bioavailability and biofunctions of chromium, cadmium, mercury and lead are heavily dependent upon their specific chemical forms, leading to a high demand to metal speciation analysis rather than total quantification. Simultaneous speciation analysis of multiple metal(loid)s is attractive to a large sample capacity containing unstable analytes due to its economic and environmental advantages over the conventional single elemental strategies. In this work, an analytical method integrating online solid phase extraction into high performance liquid chromatography interfaced with inductively coupled plasma mass spectrometry (ICP-MS) to simultaneously preconcentrate and quantify Cr, Cd, Hg and Pb forms in pg L−1 levels in water was developed. Cr(III + VI), Cd(II), Hg(II), Pb(II), methylmercury (MeHg), ethylmercury (EtHg), and trimethyl (TML) and triethyl lead (TEL) were captured by the C18 adsorbent (equilibrated with 10 mL of 1.0 mM 2-hydroxyethanethiol at 10 mL min−1) and eluted by mobile phase (5.0 mM Cys at pH 2.0), then completely separated on the C18 column within 8.0 min and eventually determined by ICP-MS. Low limits of detection (0.001–0.007 ng L−1) and quantification (0.003–0.023 ng L−1), good relative standard deviations (<4%) and high enrichment factors (827–2656 folds) were obtained with good linearities. Three reference materials of total cadmium (GBW08602), total mercury (GBW08603) and total lead (GBW08601) in water were analyzed by the developed method to validate the accuracy with good agreement with certified values and satisfactory recoveries (92–100%). This method was proved feasible by the determination of Cr, Cd, Hg and Pb compounds in drinking water, river water, pond water and tap water.

Concentrations and Species of Mercury in Municipal Sludge of Selected Chinese Cities and Potential Mercury Emissions From Sludge Treatment and Disposal

Municipal sewage has been identified as an important source of mercury (Hg) to the environment, and sewage sludge is the major sink of sewage-borne Hg. Knowledge of Hg species in sludge and potential Hg emissions during sludge treatment/disposal is still limited. A survey on Hg concentrations and species in sewage sludge of 16 provinces and municipalities in China was conducted. Hg was detected in all sewage sludge samples, with total Hg (THg) concentrations ranging from 0.3 to 7.7 mg/kg. Results from sequential chemical extractions (SCE) indicated that sludge-borne Hg mainly occurred in the form of Hg sulfide, with a small amount of organo-chelated Hg (Hg-OM) and HgO, and a negligible amount of soluble Hg. Thermal decomposition results indicated that Hg is generally released from sludge at a temperature range of 200–400°C, with the highest release at 250–350°C (38%–86%), consistent with the thermal decomposition of HgS, Hg-OM, and HgO. THg in sewage samples under ventilation at room temperature remained constant over a month period, indicating negligible Hg emission under such conditions. The mass loading of sludge-borne THg in China for year 2019 was estimated to be 30 tons, about 3.6% of the total anthropogenic THg released (including direct and secondary anthropogenic releases) in China. At the temperature range for sludge incineration, sludge carbonization, and sludge/brick/cement production, most of the Hg in sludge will be released to air due to thermal decomposition of Hg compounds. As such, Hg-capture systems are essential in sludge treatment processes involving high temperatures.