This book provides a detailed examination of the concentration, form and cycling of trace metals and metalloids through the aquatic biosphere, and has sections dealing with the atmosphere, the ocean, ...lakes and rivers. It discusses exchanges at the water interface (air/water and sediment/water) and the major drivers of the cycling, concentration and form of trace metals in aquatic systems. The initial chapters focus on the fundamental principles and modelling approaches needed to understand metal concentration, speciation and fate in the aquatic environment, while the later chapters focus on specific environments, with case studies and research highlights.Specific examples deal with metals that are of particular scientific interest, such as mercury, iron, arsenic and zinc, and the book deals with both pollutant and required (nutrient) metals and metalloids. The underlying chemical principles controlling toxicity and bioavailability of these elements to microorganisms and to the aquatic food chain are also discussed. Readership: Graduate students studying environmental chemistry and related topics, as well as scientists and managers interested in the cycling of trace substances in aqueous systemsAdditional resources for this book can be found at: www.wiley.com/go/mason/tracemetals.
Despite lack of paediatric labelling, contributions to the literature on paediatric applications of dexmedetomidine have increased over recent years. Dexmedetomidine possesses many properties that ...are advantageous for a sedative and anaesthetic; it has been reported to provide sedation that parallels natural sleep, anxiolysis, analgesia, sympatholysis, and an anaesthetic-sparing effect with minimal respiratory depression. In addition, there is increasing evidence supporting its organ-protective effects against ischaemic and hypoxic injury. These favourable physiological effects combined with a limited adverse effect profile make dexmedetomidine an attractive adjunct to anaesthesia (general and regional) for a variety of procedures in paediatric operating rooms. A comprehensive understanding of the pharmacological, pharmacokinetic, and pharmacodynamic effects of dexmedetomidine is critical to maximize its safe, efficacious, and efficient paediatric perioperative applications. This review focuses on the current paediatric perioperative and periprocedural applications of dexmedetomidine and its limitations, with a consideration for the future.
There remain unanswered questions and implications related to emergence delirium in children. Although we know that there are some predisposing factors to emergence delirium, we still are unable to ...predict accurately those who are at greatest risk. Emergence delirium should be considered as a ‘vital sign’, which should be followed and documented in every child in the postanaesthesia recovery period. Standardized screening tools should be adopted for paediatric emergence delirium.
Mercury (Hg) is a global pollutant that affects human and ecosystem health. We synthesize understanding of sources, atmosphere-land-ocean Hg dynamics and health effects, and consider the implications ...of Hg-control policies. Primary anthropogenic Hg emissions greatly exceed natural geogenic sources, resulting in increases in Hg reservoirs and subsequent secondary Hg emissions that facilitate its global distribution. The ultimate fate of emitted Hg is primarily recalcitrant soil pools and deep ocean waters and sediments. Transfers of Hg emissions to largely unavailable reservoirs occur over the time scale of centuries, and are primarily mediated through atmospheric exchanges of wet/dry deposition and evasion from vegetation, soil organic matter and ocean surfaces. A key link between inorganic Hg inputs and exposure of humans and wildlife is the net production of methylmercury, which occurs mainly in reducing zones in freshwater, terrestrial, and coastal environments, and the subsurface ocean. Elevated human exposure to methylmercury primarily results from consumption of estuarine and marine fish. Developing fetuses are most at risk from this neurotoxin but health effects of highly exposed populations and wildlife are also a concern. Integration of Hg science with national and international policy efforts is needed to target efforts and evaluate efficacy.
The Minamata Convention to reduce anthropogenic mercury (Hg) emissions entered into force in 2017, and attention is now focused on how to best monitor its effectiveness at reducing Hg exposure to ...humans. A key question is how closely Hg concentrations in the human food chain, especially in fish and other aquatic wildlife, will track the changes in atmospheric Hg that are expected to occur following anthropogenic emission reductions. We investigated this question by evaluating several regional groups of case studies where Hg concentrations in aquatic biota have been monitored continuously or intermittently for several decades. Our analysis shows that in most cases Hg time trends in biota did not agree with concurrent Hg trends in atmospheric deposition or concentrations, and the divergence between the two trends has become more apparent over the past two decades. An over-arching general explanation for these results is that the impact of changing atmospheric inputs on biotic Hg is masked by two factors: 1) The aquatic environment contains a large inventory of legacy emitted Hg that remains available for bio-uptake leading to a substantial lag in biotic response time to a change in external inputs; and 2) Biotic Hg trends reflect the dominant effects of changes in multi-causal, local and regional processes (e.g., aquatic or terrestrial biogeochemical processes, feeding ecology, climate) that control the speciation, bioavailability, and bio-uptake of both present-day and legacy emitted Hg. Globally, climate change has become the most prevalent contributor to the divergence. A wide range of biotic Hg outcomes can thus be expected as anthropogenic atmospheric Hg emissions decline, depending on how these processes operate on specific regions and specific organisms. Therefore, evaluating the effectiveness of the Minamata Convention will require biomonitoring of multiple species that represent different trophic and ecological niches in multiple regions of the world.
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•Mercury time-trends in aquatic biota often do not agree with atmospheric trends.•Divergence between the two trends has become more apparent in the past two decades.•The divergence is due to legacy mercury and changing biogeochemical processes.•Globally climate change has become the most prevalent contributor to the divergence.•Thus, the efforts of the Minamata Convention may be countered by climate change.
Underlying formation pathways of dimethylmercury ((CH3)2Hg) in the ocean are unknown. Early work proposed reactions of inorganic Hg (Hg(II)) with methyl cobalamin or of dissolved monomethylmercury ...(CH3Hg) with hydrogen sulfide as possible bacterial mediated or abiotic pathways. A significant fraction (up to 90%) of CH3Hg in natural waters is however adsorbed to reduced sulfur groups on mineral or organic surfaces. We show that binding of CH3Hg to such reactive sites facilitates the formation of (CH3)2Hg by degradation of the adsorbed CH3Hg. We demonstrate that the reaction can be mediated by different sulfide minerals, as well as by dithiols suggesting that e.g. reduced sulfur groups on mineral particles or on protein surfaces could mediate the reaction. The observed fraction of CH3Hg methylated on sulfide mineral surfaces exceeded previously observed methylation rates of CH3Hg to (CH3)2Hg in seawaters and we suggest the pathway demonstrated here could account for much of the (CH3)2Hg found in the ocean.
The forms of inorganic mercury (HgII) taken up and methylated by bacteria in sediments still remain largely unknown. From pure cultures studies, it has been suggested that dissolved organic matter ...(DOM) may facilitate the uptake either by acting as a shuttle molecule, transporting the HgII atom to divalent metal transporters, or by binding HgII and then being transported into the cell as a carbon source. Enhanced availability of Hg complexed to DOM has however not yet been demonstrated in natural systems. Here, we show that HgII complexed with DOM of marine origin was up to 2.7times more available for methylation in sediments than HgII added as a dissolved inorganic complex (HgII(aq)). We argue that the DOM used to complex HgII directly facilitated the bacterial uptake of HgII whereas the inorganic dissolved HgII complex adsorbed to the sediment matrix before forming bioavailable dissolved HgII complexes. We further demonstrate that differences in net methylation in sediments with high and low organic carbon content may be explained by differences in the availability of carbon to stimulate the activity of Hg methylating bacteria rather than, as previously proposed, be due to differences in HgII binding capacities between sediments.
Currently, there are no established definitions or terminology for sedation-related adverse events (AEs). With clear terminology and definitions, sedation events may be accurately identified and ...tracked, providing a benchmark for defining the occurrence of AEs, ranging from minimal to severe. This terminology could apply to sedation performed in any location and by any provider. We present a consensus document from the International Sedation Task Force (ISTF) of the World Society of Intravenous Anaesthesia (World SIVA). The ISTF is composed of adult and paediatric sedation practitioners from multiple disciplines throughout the world.
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