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The interaction between mercury (Hg) and selenium (Se) is one of the best known examples of biological antagonism, yet the underlying mechanism remains unclear. This review focuses on the possible pathways leading to the Hg‐Se antagonism, with an emphasis on the potential Hg‐Se compounds that are responsible for the antagonism at the molecular level (i.e., bis[methylmercuric]selenide, methylmercury selenocysteinate, selenoprotein P‐bound HgSe clusters, and the biominerals HgSexS1−x). The presence of these compounds in biological systems has been suggested by direct or indirect evidence, and their chemical properties support their potentially key roles in alleviating the toxicity of Hg and Se (at high Hg and Se exposures, respectively) and deficiency of Se (at low Se exposures). Direct analytical evidences are needed, however, to confirm their in vivo presence and metabolic pathways, as well as to identify the roles of other potential Hg‐Se compounds. Further studies are also warranted for the determination of thermodynamic properties of these compounds under physiological conditions toward a better understanding of the Hg‐Se antagonism in biota, particularly under real world exposure scenarios.

This review covers the toxicology of mercury and its compounds. Special attention is paid to those forms of mercury of current public health concern. Human exposure to the vapor of metallic mercury dates back to antiquity but continues today in occupational settings and from dental amalgam. Health risks from methylmercury in edible tissues of fish have been the subject of several large epidemiological investigations and continue to be the subject of intense debate. Ethylmercury in the form of a preservative, thimerosal, added to certain vaccines, is the most recent form of mercury that has become a public health concern. The review leads to general discussion of evolutionary aspects of mercury, protective and toxic mechanisms, and ends on a note that mercury is still an \"element of mystery.\"

Whales accumulate mercury (Hg), but do not seem to show immediate evidence of toxic effects. Analysis of different tissues (liver, kidney, muscle) and biofluids (blood, milk) from a pod of stranded long-finned pilot whales ( Globicephala melas ) showed accumulation of Hg as a function of age, with a significant decrease in the MeHg fraction. Isotopic analysis revealed remarkable differences between juvenile and adult whales. During the first period of life, Hg in the liver became isotopically lighter (δ 202 Hg decreased) with a strongly decreasing methylmercury (MeHg) fraction. We suggest this is due to preferential demethylation of MeHg with the lighter Hg isotopes and transport of MeHg to less sensitive organs, such as the muscles. Also changes in diet, with high MeHg intake in utero and during lactation, followed by increasing consumption of solid food contribute to this behavior. Interestingly, this trend in δ 202 Hg is reversed for livers of adult whales (increasing δ 202 Hg value), accompanied by a progressive decrease of δ 202 Hg in muscle at older ages. These total Hg (THg) isotopic trends suggest changes in the Hg metabolism of the long-finned pilot whales, development of (a) detoxification mechanism(s) ( e.g ., though the formation of HgSe particles), and Hg redistribution across the different organs.

Bacterial resistance to inorganic and organic mercury compounds (HgR) is one of the most widely observed phenotypes in eubacteria. Loci conferring HgR in Gram-positive or Gram-negative bacteria typically have at minimum a mercuric reductase enzyme (MerA) that reduces reactive ionic Hg(II) to volatile, relatively inert, monoatomic Hg(0) vapor and a membrane-bound protein (MerT) for uptake of Hg(II) arranged in an operon under control of MerR, a novel metal-responsive regulator. Many HgR loci encode an additional enzyme, MerB, that degrades organomercurials by protonolysis, and one or more additional proteins apparently involved in transport. Genes conferring HgR occur on chromosomes, plasmids, and transposons and their operon arrangements can be quite diverse, frequently involving duplications of the above noted structural genes, several of which are modular themselves. How this very mobile and plastic suite of proteins protects host cells from this pervasive toxic metal, what roles it has in the biogeochemical cycling of Hg, and how it has been employed in ameliorating environmental contamination are the subjects of this review.

Mercury (Hg) has long been recognised as a global pollutant, because it can remain in the atmosphere for more than 1 year. The mercury that enters the environment is generally acknowledged to have two sources: natural and anthropogenic. Hg takes three major forms in the environment, namely methyl-Hg (MeHg), Hg⁰and Hg²⁺. All three forms of Hg adversely affect the natural environment and pose a risk to human health. In particular, they may damage the human central nervous system, leading to cardiovascular, respiratory and other diseases. MeHg is bioavailable and can be bioaccumulated within food webs. Therefore, several methods of eliminating Hg from the soil and the aquatic system have been proposed. The focus of this article is on phytoremediation, as this technique provides a low-cost and environmentally friendly alternative to traditional methods.

Acute toxicity of inorganic mercury [Hg(II)] and methylmercury (MeHg) to Daphnia magna was characterized using a 48-h static, non-renewal acute toxicity test, in which we compared the toxicity of Hg(II) and MeHg in the absence (water-only) and presence of diet [green alga ( Raphidocelis subcapitata ), yeast, Cerophyll, and trout chow (YCT), or both]. Overall, Hg(II) is more toxic to D. magna than MeHg, with 48-h median lethal concentrations (LC50s) being 4.3 µg/L (95% confidence interval: 4.1–4.5 µg/L) for Hg(II) and 14.3 µg/L (13.2–15.3 µg/L) for MeHg. For Hg(II), the addition of any diet would significantly increase its 48-h LC50, but the 48-h LC50 for MeHg decreased significantly to 7.1 µg/L (6.4–7.8 µg/L) with the algal addition. We also show that the addition of diets significantly influenced the levels and speciation (dissolved vs. particulate) of both Hg forms in the test solution. The bioaccumulation of Hg(II) and MeHg was impacted by the dietary addition, and it appears that the body residue level triggering mortality varied widely among treatments. The results suggest that standard short-term toxicity tests (water-only) should be supplemented with extra tests with dietary addition to provide a more environmentally relevant estimation of short-term toxicity of chemical compounds.

The chemical behavior of mercury (Hg) and its interactions with naturally occurring ligands shape its environmental fate and impact. The neurotoxic properties of Hg are widely known and studied both in vitro and in vivo . However, there continues to be limited information on the influence of chelation with large organic ligands on the toxicity to marine macro-organisms. This work examined the effect of Hg complexed with various types of dissolved organic matter (DOM) on the mortality and hatching success of Artemia sp. nauplii under varying marine media conditions. The results confirmed both, an alleviating as well as additive, DOM-specific, effect on mortality. DOM coexposure resulted in a compound specific decreased or increased toxicity in comparison with single exposure in artificial seawater, with LC 50 values ranging from 2.11 to 62.89 µM. Hatching success under conditions of Hg exposure was almost two orders of magnitude more sensitive than toxicity in hatched individuals. Elevated DOM concentrations had no statistically significant impact on hatching success with computed EC 50 values ranging from 196 to 324 nM. Graphical 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.

We report an extremely sensitive and specific detection of mercuric ions (Hg 2+ ) based on graphene assisted laser desorption/ionization mass spectrometry (GALDI-MS). Combining the highly selective coordination interactions between thymine (T) and Hg 2+ , we present a simple, effective, and novel approach, based on π–π interactions of the T-Hg 2+ -T complex and G that can serve as a platform and matrix for GALDI-MS. The present sensor not only exhibits high selectivity and sensitivity (picomolar) to Hg 2+ in aqueous solution, but also can elucidate the chemical structures of the metal complexes. The significant advantage in the current approach is that there is no need for a sophisticated instrument, and no sample pretreatment is required to detect the Hg 2+ ions. Figure ᅟ

Reducing mercury emission is hot topic for international society. The first step for controlling mercury in fuel gas is to investigate mercury distribution and during the flue gas treatment process. The mercury transport and transformation in wet flue gas cleaning process of nonferrous smelting industry was studied in the paper with critical important parameters, such as the solution temperature, Hg 0 concentration, SO 2 concentration, and Hg 2+ concentration at the laboratory scale. The mass ratio of the mercury distribution in the solution, flue gas, sludge, and acid fog from the simulated flue gas containing Hg 2+ and Hg 0 was 49.12~65.54, 18.34~35.42, 11.89~14.47, and 1.74~3.54%, respectively. The primary mercury species in the flue gas and acid fog were gaseous Hg 0 and dissolved Hg 2+ . The mercury species in the cleaning solution were dissolved Hg 2+ and colloidal mercury, which accounted for 56.56 and 7.34% of the total mercury, respectively. Various mercury compounds, including Hg 2 Cl 2 , HgS, HgCl 2 , HgSO 4 , and HgO, existed in the sludge. These results for mercury distribution and speciation are highly useful in understanding mercury transport and transformation during the wet flue gas cleaning process. This research is conducive for controlling mercury emissions from nonferrous smelting flue gas and by-products.