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This paper reviews the growing literature dealing with the antagonistic effect of selenium (Se) compounds on the toxicity of mercury (Hg) compounds in higher animals and organisms present in the aquatic environment. It covers both laboratory and field studies and summarizes the possible mechanisms that explain the protective action of Se compounds on mercuric mercury (Hg2+) and methylmercury (CH3Hg+) toxicity. The review is subdivided according to the molecular form of Hg and the organisms in which the antagonism has been studied. Many authors suggest that the protective effect of selenite on the toxicity of Hg2+in mammals is due mainly to the in vivo formation of mercuric selenide (HgSe), a stable and biologically inert complex. The detection of HgSe has been confirmed in several studies in support of this mechanism. Possible mechanisms that may be involved in the antagonism between Se compounds and CH3Hg+in mammals and aquatic organisms are also presented. The possibility of adding Se compounds to contaminated lakes and reservoirs as a remediation technique to limit the bioaccumulation of Hg2+and CH3Hg+is critically discussed.

Abstract Oil drilling and industrial effluent that wasted through the Bengawan Solo River estuary is a source of environmental pollution in the Sidayu and Banyu Urip district, Gresik as one that produces the blood shellfish (Anadara granosa). One of the most dangerous contaminants of heavy metals is mercury. However shellfish can accumulate more heavy metals than other aquatic animals because it settle and filter their food (filter feeder) and slow to be able to avoid the effects of pollution The Aim of this study are to determine the levels of mercury and methyl mercury predictions on blood shellfish (Anadara granosa). The process of sampling was done at coastal area of Sidayu and Banyu Urip district, Gresik then performed using Atomic Absorbance readings Spectrophotometric (AAS). This is a descriptive study and the data obtained, and then continued with stoichiometric calculations to predict the content of methyl mercury. Based on the analysis of mercury and prediction of methyl mercury in the blood shellfish (Anadara granosa) organs in coastal area of Sidayu and Banyu Urip district, Gresik, has not exceeded the threshold of SNI, the value is 0.5 ppm. Mercury contamination was high in blood clam shell with the average value of 0.273 ppm and 0.293 ppm, followed by the stomach and intestines shell with an average value of 0.226 ppm and 0.281 ppm. Lowest contamination is on the organ gill, liver, and kidneys with the average value of 0.150 ppm and 0.133 ppm.

Mercury is a potent neurotoxic substance and accounts for 250,000 intellectual disabilities annually. Worldwide, coastal fisheries contribute the majority of human exposure to mercury through fish consumption. Recent global mercury cycling and risk models attribute all the mercury loading to the ocean to atmospheric deposition. Nevertheless, new regional research has noted that the riverine mercury export to coastal oceans may also be significant to the oceanic burden of mercury. Here we construct an unprecedented high-spatial-resolution dataset estimating global river mercury and methylmercury exports. We find that rivers annually deliver 1,000 (minimum–maximum: 893–1,224) Mg mercury to coastal oceans, threefold greater than atmospheric deposition. Furthermore, high flow events, which are becoming more common with climate change, are responsible for a disproportionately large percentage of the export. Coastal oceans constitute 0.2% of the entire ocean volume but receive 27% of the external mercury input to the ocean. We estimate that the river mercury export could be responsible for a net annual export of 350 (interquartile range: 52–640) Mg mercury across the coastal–open-ocean boundary, although there is still high uncertainty around this estimate. Our results show that river export is the largest source of mercury to coastal oceans worldwide, and continued mercury risk modelling should incorporate the impact of rivers. Rivers transport about 1,000 Mg mercury annually to coastal oceans, which is threefold greater than the amount delivered by atmospheric deposition, according to a global analysis of mercury measurements in rivers.

This paper integrates several areas of the literature by more fully developing the linkage between demand estimates and the welfare effects of food labels and bans for three common survey/experimental approaches used to elicit consumer preferences. We present empirical applications related to beef cloning and methylmercury in fish where, for the same data sets, we compare each value elicitation approach in terms of the consumer surplus changes that result from two regulations. Welfare measures vary significantly across the three methodologies, but the sign of the welfare change is invariant across method.

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.

The Greenland Ice Sheet is currently not accounted for in Arctic mercury budgets, despite large and increasing annual runoff to the ocean and the socio-economic concerns of high mercury levels in Arctic organisms. Here we present concentrations of mercury in meltwaters from three glacial catchments on the southwestern margin of the Greenland Ice Sheet and evaluate the export of mercury to downstream fjords based on samples collected during summer ablation seasons. We show that concentrations of dissolved mercury are among the highest recorded in natural waters and mercury yields from these glacial catchments (521–3,300 mmol km −2 year −1 ) are two orders of magnitude higher than from Arctic rivers (4–20 mmol km −2 year −1 ). Fluxes of dissolved mercury from the southwestern region of Greenland are estimated to be globally significant (15.4–212 kmol year −1 ), accounting for about 10% of the estimated global riverine flux, and include export of bioaccumulating methylmercury (0.31–1.97 kmol year −1 ). High dissolved mercury concentrations (~20 pM inorganic mercury and ~2 pM methylmercury) were found to persist across salinity gradients of fjords. Mean particulate mercury concentrations were among the highest recorded in the literature (~51,000 pM), and dissolved mercury concentrations in runoff exceed reported surface snow and ice values. These results suggest a geological source of mercury at the ice sheet bed. The high concentrations of mercury and its large export to the downstream fjords have important implications for Arctic ecosystems, highlighting an urgent need to better understand mercury dynamics in ice sheet runoff under global warming. Meltwaters from the southwestern margin of the Greenland Ice Sheet contain exceptionally high concentrations of mercury, exporting up to more than 200 kmol of dissolved mercury every year, suggest mercury measurements from three glacial catchments.

Two sites of the Colombian Amazon region with different levels of human intervention and mercury pollution were selected for the collection of samples of river and lake water, sediments, and associated forest soils. The Tarapacá region, affected mainly by barrage mining, showed low mercury concentrations, whilst in the Taraira region, affected by underground mining, there were several points with high mercury pollution levels. A collection of 72 bacterial and 10 yeast strains with different levels of mercury resistance was isolated and characterized. Most of the highly resistant bacterial strains (MIC > 40 mg L −1 HgCl 2 ) were isolated from soil and sediment samples and belonged to either Pseudomonas (60%) or Bacillus (20%). Most of highly resistant bacterial strains were positive for the presence of the merA gene, suggesting an active mercury resistance mechanism. This was confirmed in the two most resistant strains, Pseudomonas sp. TP30 and Burkholderia contaminans TR100 (MIC = 64 and 71 mg L −1 HgCl 2 , respectively), which in the presence of increasing mercury concentrations expressed the merA gene at increasing levels, concomitant with a significant mercury reduction activity. Analysis of the MerA sequences present in the different isolates suggested a high gene conservation within the taxonomic groups but also several horizontal gene transfer events between taxonomically distant genera. We also observed a positive correspondence between the presence of the merA gene and the number of antibiotics to which the strains were resistant to. The most resistant strains are good candidates for future applications in the bioremediation of mercury-contaminated sites in the Amazon. Key points • Amazon sediments affected by underground gold mining have higher Hg levels. • Highly Hg-resistant isolates belonged to Pseudomonas and Bacillus genera. • TR100 and TP30 strains showed remediation potential to be used in the Amazon region. Graphical abstract

An important provision of the Minamata Convention on Mercury is to monitor and evaluate the effectiveness of the adopted measures and its implementation. Here, we describe for the first time currently available biotic mercury (Hg) data on a global scale to improve the understanding of global efforts to reduce the impact of Hg pollution on people and the environment. Data from the peer-reviewed literature were compiled in the Global Biotic Mercury Synthesis (GBMS) database (>550,000 data points). These data provide a foundation for establishing a biomonitoring framework needed to track Hg concentrations in biota globally. We describe Hg exposure in the taxa identified by the Minamata Convention: fish, sea turtles, birds, and marine mammals. Based on the GBMS database, Hg concentrations are presented at relevant geographic scales for continents and oceanic basins. We identify some effective regional templates for monitoring methylmercury (MeHg) availability in the environment, but overall illustrate that there is a general lack of regional biomonitoring initiatives around the world, especially in Africa, Australia, Indo-Pacific, Middle East, and South Atlantic and Pacific Oceans. Temporal trend data for Hg in biota are generally limited. Ecologically sensitive sites (where biota have above average MeHg tissue concentrations) have been identified throughout the world. Efforts to model and quantify ecosystem sensitivity locally, regionally, and globally could help establish effective and efficient biomonitoring programs. We present a framework for a global Hg biomonitoring network that includes a three-step continental and oceanic approach to integrate existing biomonitoring efforts and prioritize filling regional data gaps linked with key Hg sources. We describe a standardized approach that builds on an evidence-based evaluation to assess the Minamata Convention’s progress to reduce the impact of global Hg pollution on people and the environment.

Mercury is a volatile heavy element with no known biological function. It is present in trace amounts (on average, ∼ 80 ppb) but is not geochemically well blended in the Earth's crust. As a result, it occurs in extremely high concentrations (up to a few percent) in certain locations. It is found along tectonic plate faults in deposits of sulfide ores (cinnabar), and it has been extensively mobilized during the Anthropocene. Mercury is currently one of the most targeted global pollutants, with methylmercury compounds being particularly neurotoxic. Over 5000 t of mercury is released into the atmosphere annually through primary emissions and secondary re-emissions. Much of the re-emitted mercury resulting from exchanges with surface reservoirs is related to (legacy) human activities, such as direct releases. Understanding the dynamics of the global Hg cycle is critical for assessing the impact of emission reductions under the UN Minamata Convention, which became legally binding in 2017. This review of atmospheric mercury focuses on fundamental advances in field, laboratory, and theoretical studies, including six stable Hg isotope analytical methods, which have contributed recently to a more mature understanding of the complexity of the atmospheric Hg cycle and its interactions with the Earth's surface ecosystem.

The deposition of different atmospheric mercury (Hg) species into oceans determines the atmospheric Hg lifetime and the production of neurotoxin methylmercury. Yet, the relative contribution of atmospheric Hg(II) and Hg(0) is largely unconstrained. Here, we report the concentrations of total Hg and methylmercury, as well as Hg isotope composition in living corals collected from the tropical South China Sea (SCS). The results show that the Hg in corals is mainly present as inorganic Hg, exhibiting slightly negative δ202Hg and small yet significant Δ199Hg and Δ200Hg. These isotope features closely resemble those of pelagic waters, suggesting that shallow‐water corals that are widely distributed in oligotrophic waters could be used to trace atmospheric Hg deposition pathways. A mixture model based on coral Δ200Hg indicates that approximately 49% of the seawater Hg in the tropical SCS, a region characterized by high rainfall, originates from atmospheric gaseous Hg(0), much larger than previous estimates. Plain Language Summary Mercury (Hg) is a toxic heavy metal pollutant that has significant impacts on the environment. The ocean plays a crucial role in the global Hg cycle, with atmospheric Hg deposition being a major source of Hg in seawater. By elucidating the sources, transport, and transformations of Hg in the marine environment, we can develop effective strategies for its mitigation and environmental management. However, our current understanding of how atmospheric mercury enters the open sea is limited, due to challenges in directly measuring trace amounts of mercury in seawater. The widely distributed shallow‐water coral could be an important supplement. Here we present the first‐ever examination of mercury isotope compositions in coral polyps and their symbiotic zooxanthellae from the tropical South China Sea to investigate atmospheric Hg sources into the open ocean. The result shows that the ratio of atmospheric divalent Hg(II) to elemental Hg(0) deposition derived from coral isotopes is only about one quarter of the estimate based on current observations. Our study presents a novel approach to constrain atmospheric Hg deposition pathways into the ocean and challenges the prevailing viewpoint that Hg in tropical oceans mainly originates from precipitation. Key Points First study of Hg isotope compositions in coral polyps and their symbiotic zooxanthellae Shallow‐water coral tissue can serve as an archive for Hg isotopic compositions of the surface seawater Coral Δ200Hg reveals that ∼49% of seawater Hg in the tropical South China Sea is derived from atmospheric gaseous elemental Hg