No evidence for large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet.

In the current Matters Arising we present results from verifying control measurements of dissolved mercury (Hg) in glacial meltwater from the Greenland Ice Sheet (GrIS), which significantly challenges the conclusions of the recent publication by Hawkings et al. (2021). By direct measurements of meltwater in the same glacial catchment area, we demonstrate that the input Hg concentration for the regional upscaling in Hawkings et al (2021) is likely vastly over-estimated with major implications for the validity of the asserted extreme yield of Hg from the GrIS. In addition, we present a plausible explanation for the high Hg concentration values in the study, namely hitherto unidentified cross-contamination of water samples by mercury chloride (HgCl2), which was present and used for other purposes during field work. Together, the result of our control study potentially invalidates the suggested implications of geologically sourced Hg under the southwestern margin of the GrIS on the Arctic ecosystem in both current and future climate conditions.

Interactions between atomically dispersed copper and phosphorous species are key for the hydrochlorination of acetylene

Vinyl chloride, the monomer of polyvinyl chloride (PVC), is industrially synthesized via acetylene hydrochlorination. Thereby, easy to sublimate but toxic mercury chloride catalysts are widely used. It is imperative to find environmentally friendly non-mercury catalysts to promote the green production of PVC. Low-cost copper-based catalysts are promising candidates. In this study, phosphorus-doped Cu-based catalysts are prepared. It is shown that the type of phosphorus configuration and the distribution on the surface of the carrier can be adjusted by changing the calcination temperature. Among the different phosphorus species, the formed P-C bond plays a key role. The coordination structure formed by the interaction between P-C bonds and atomically dispersed Cu2+ species results in effective and stable active sites. Insights on how P-C bonds activate the substrate may provide ideas for the design and optimization of phosphorus-doped catalysts for acetylene hydrochlorination.

Numerical Study on the Homogeneous Reactions of Mercury in a 600 MW Coal-Fired Utility Boiler

The homogeneous oxidation of elemental mercury (Hg0) can promote Hg pollution control in coal-fired power plants, while the mechanisms and quantitative contributions of homogeneous reactions in Hg0 oxidation, especially the reactions between Hg and chlorine (Cl), are still unclear. Here, a numerical study on the homogeneous reactions of Hg was conducted within a 600 MW tangentially fired boiler for the first time. A novel Hg sub-model was established by coupling the thermodynamics, reaction kinetics and fluid dynamics. The results showed that the higher Cl content in coal was beneficial to the oxidation of Hg0. The homogeneous reactions of Hg mainly occurred in the vertical flue pass at low temperature. Hg0 was still the dominant Hg-containing species at the boiler exit, and the concentration of mercury chloride (HgCl2) was the highest among the oxidized mercury. When low-Cl coal was fired, the addition of a small amount of chlorine species into the boiler at the burnout area increased the ratio of HgCl2 by over 16 times without causing serious chlorine corrosion problems.

Antioxidant Potentials of Pentaclethra macrophylla Seed (Ugba) on Mercury Toxicity Induced Hepatic, Renal and Testicular Oxidative Stress in Male Albino Rats

Aim: This study aimed to evaluate the antioxidant potentials of Pentaclethra macrophylla seed (Ugba) on mercury-induced hepatic, renal and testicular oxidative stress in male Albino Rats. Study Design: This study is an experimental study. Place and Duration of Study: Department of Animal and Environmental Biology Animal House, Rivers State University, Port Harcourt, Nigeria, between January 2019 and January 2021. Methodology: Thirty-six (36) adult male albino rats weighing approximately 135±1.5g were purchased from the University of Port Harcourt, Rivers State, Nigeria. They were housed in plastic suspended cages, placed in well-ventilated conditions and provided with rat diet and water, and acclimatized for two weeks. Fresh matured seeds of Pentaclethra macrophylla (African oil bean seed) were sourced locally from markets in Imo state, Nigeria. The maceration technique was used to carry out an ethanolic extract of the plant seed. Mercury chloride salt was purchased from Port Harcourt. A standard dose of 3.0mg/kg body weight of mercury chloride obtained from acute toxicity study dose determination was administered to the rats for 30 days after they were divided into six groups of six rats per group. After 30 days, all the animals were weighed, anesthetized using chloroform. Tissue samples of liver, kidney, and testis were collected and homogenized in phosphate-buffered saline and stored at 40C for determination of oxidative stress assessment. Malondialdehyde, Reduced Glutathione (GSH), Catalase Activity, superoxide dismutase (SOD) activity, Glutathione Peroxidase Activity were analyzed using the homogenized sample. Data were expressed as mean ±SD, and the statistical analysis was performed with the SPSS statistics 23.0, and p values less than .05 were considered statistically significant. Results: The results showed that there were significant increases (P<.05) in the liver, kidney, and testicular MDA and significant decreases (p<.05) in SOD, CAT, GSH, and GPx activities in group 2 rats versus control. However, after treatment with different concentrations of Pentaclethra macrophylla, MDA activity significantly decreased (P<.05), while SOD, CAT, GPx, and GSH significantly increased (P<.05). Conclusion: The results obtained from the study showed that mercury chloride has the potential to cause liver, kidney, and testicular toxicity to adult male albino rats, and this toxicity was exerted majorly through oxidative stress and lipid peroxidation. However, treatment with Pentaclethra macrophylla seed extract ameliorated oxidative stress.

Mercury Chloride Impacts on the Development of Erythrocytes and Megakaryocytes in Mice

Inorganic mercury (Hg2+) is a highly toxic heavy metal. The aim of this study was to investigate the impact of Hg2+ on the development of erythrocytes and megakaryocytes. B10.S mice (H-2s) and DBA/2 mice (H-2d) were administrated with 10 μM HgCl2 or 50 μM HgCl2 via drinking water for four weeks, and erythro-megakaryopoiesis was evaluated thereafter. The administration of 50 μM HgCl2 increased the number of erythrocytes and platelets in B10.S mice, which was not due to a reduced clearance for mature erythrocytes. The administration of 50 μM HgCl2, but not 10 μM HgCl2, increased the number of progenitors for erythrocytes and megakaryocytes in the bone marrow (BM) of B10.S mice, including erythroid-megakaryocyte progenitors (EMPs), burst-forming unit-erythroid progenitors (BFU-Es), colony-forming unit-erythroid progenitors (CFU-Es), and megakaryocyte progenitors (MkPs). Moreover, 50 μM HgCl2 caused EMPs to be more proliferative and possess an increased potential for differentiation into committed progenies in B10.S mice. Mechanistically, 50 μM HgCl2 increased the expression of the erythropoietin receptor (EPOR) in EMPs, thus enhancing the Jak2/STAT5 signaling pathway to promote erythro-megakaryopoiesis in B10.S mice. Conversely, 50 μM HgCl2 did not impact erythro-megakaryopoiesis in DBA/2 mice. This study may extend our current understanding for hematopoietic toxicology of Hg.

The Effect of Thymol on Renal Toxicity Induced by Mercury Chloride in Rats

Background and Aims: Mercuric chloride is highly toxic once absorbed into the bloodstream, especially the kidneys in which it is collected. Mercury chloride increases hydrogen peroxide and enhances the destruction of protective enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPX), leading to oxidative stress. Besides, thymol has anti-oxidant effects and can increase the activity of SOD and GPX. This study aims to evaluate the efficacy of thymol on mercury chloride-induced toxicity. Materials and Methods: In this study, 30 rats, consisting of 6 groups of 5, were used. Control group receiving a single dose of 0.5 mg/kg mercuric chloride for 15 days, third, fourth, and fifth group received intraperitoneal injection of mercuric chloride at a dose of 0.5 mg/kg for 15 days plus thymol at a dose of 10, 30, 50 mg/kg. The sixth group received mercuric chloride at a dose of 0.5 mg/kg for 15 days plus thymol at 30 mg/kg per day for ten days. Results: Results showed a significant difference in the activity of catalase enzyme in kidney tissue samples test. According to the results of SOD, there is a significant difference between the group of corn oil and the group of mercury chloride and between the group of mercury chloride and the group that receives thymol at a dose of 10, 30, 50 mg/kg (p ≤ 0.05). Conclusions: It can be concluded that mercury chloride-induced kidney toxicity and thymol have anti-oxidant protective effects for SOD and GPX.

Sorbents of Phenols As a Components of the Nutritional Medium in Microclonal Reproduction of Plants

In the process of microclonal reproduction, plants secrete various substances into the nutrient medium, for example, phenolic compounds, which act as inhibitors of growth processes and, accordingly, prevent the normal development of explants in vitro. Plant tissues are treated with stabilizing substances, and various sorbents are also used as components of the nutrient medium to neutralize the negative effects of phenols. This paper presents an overview of the approved methods for solving the problem of sorption of phenolic compounds during microclonal propagation of plants. Various studies are considering the addition of certain components to the nutrient medium that prevent the release of harmful growth-inhibiting substances. Most often, various carbon compounds, such as activated carbon, are used as an adsorbent. The authors, based on the analysis of domestic and foreign literature on this topic, conclude that the most effective and frequently used are carbon compounds and the polymer polyvinyl pyrrolidone, less common is the use of the following inhibitory substances: ascorbic and citric acids, silver nitrate and mercury chloride. According to the results of the conducted analytical studies, the prospects of using such substances as thermally expanded graphite (TEG) and colloidal silicon dioxide as sorbents in the composition of the drug “Polysorb” were revealed. Due to the inhomogeneous porous structure, including both micropores and meso- or macropores, TEG is able to adsorb pollutants both from the solution and from the water surface, which makes it a potential sorbent for phenolic compounds. The effect of silicon dioxide, in amorphous form, on plants in vitro has already been successfully tested by some researchers, which indicates the prospects of its study.

The role of nitrosative and oxidative stress in rainbow trout (Oncorhynchus mykiss) liver tissue applied mercury chloride (HgCl2)

The aim of this study was to determine oxidative stress caused by mercury chloride (HgCl2) in rainbow trout (Oncorhynchus mykiss) liver tissue. For this purpose, the LD50 value of HgCl2 on rainbow trout was determined as 551 μg/L. In the study, 40 fish in four groups were exposed to 25% and 50% (138 and 276 µg/L) of the two subletal doses of HgCl2 for 2 and 7 days, with 10 fish (n=10) in each group. To determine oxidative stress; peroxynitrite (ONOO−), total oxidant level (TOS), total antioxidant level (TAS), oxidative stress index (OSI) and malondialdehyde (MDA) were analyzed. In the study, it was observed that the differences between the groups in terms of ONOO−, TOS, TAS and OSI levels in the liver tissues was significant (P<0.05), however, this difference was not significant (P>0.05) in terms of MDA values. As a result, it can be concluded that HgCl2 increases ONOO−, TOS, TAS, OSI and MDA levels in liver tissue and even small doses of mercury are toxic to fish.