330 research outputs found
Ecological indicators for mercury biomonitoring using fish: Insights from compound-specific nitrogen and mercury stable isotopes
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Isotopic investigation of atmospheric mercury sources and their influence in forest ecosystems
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Mercury stable isotopes for monitoring the effectiveness of the Minamata Convention on Mercury
No full textThe Minamata Convention on Mercury (MC) includes provisions for a global monitoring program (GMP) and effectiveness evaluation (EE) to provide information on changes in mercury sources in various environmental media. While conventional measurement and modeling techniques have limitations in explaining the changes in mercury concentrations, the measurements of natural abundances of mercury stable isotopes have become powerful tracers for distinguishing between mercury sources and for understanding biogeochemical processes in the environment. Unfortunately, it is uncertain whether mercury isotope ratios can provide globally comparable results on specific mercury sources for the GMP and trend analyses for the EE. We have compiled a dataset from the literature to evaluate large-scale patterns of mercury isotope ratios in various environmental samples and to summarize sample types that can be used for the GMP. Total gaseous mercury, precipitation, foliage, and litter can provide comparable source information regarding atmospheric mercury across a large spatial scale. Interpretation of spatially relevant information using sediment and fish mercury isotope ratios are challenging because they represent multiple mercury sources and contain mercury that has been subject to biogeochemical transformation leading to isotope fractionation. In regards to the EE, data that provides evidence of changes due to source regulation needs to be gathered from local point source regions to assess health impacts. We recommend that the measurements of particulate-bound mercury in the atmosphere and sediment mercury isotope ratios near mercury hotspots and in fish, are needed to identify ecosystems sensitive to atmospheric deposition and to evaluate the effectiveness of the MC.11Nsciescopu
Ecological traits of fish for mercury biomonitoring: Insights from compound-specific nitrogen and stable mercury isotopes
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Isotopic study of inorganic and methylmercury accumulation and distribution in Paralichthys olivaceus
No full textStudies of mercury bioaccumulation in fish continue to be an important scientific discipline for understanding the bioavailability and fate of mercury and for monitoring environmental levels of mercury in natural aquatic ecosystems. Many recent studies have utilized mercury stable isotope ratios in fish to monitor mercury sources and biogeochemical processes in diverse aquatic ecosystems. More experimental studies are however needed to precisely quantify the degree and mechanism(s) governing internal isotope fractionation of two mercury species, methylmercury (MMHg) and inorganic mercury (IHg), in fish. In order to better trace environmental sources of mercury using fish, we performed controlled experiments by raising Paralichthys olivaceus in captivity for 3 months and feeding them food pellets spiked with either MMHg or IHg (0.4 and 1.6 ug/g). Total mercury (THg) and MMHg concentrations and mercury isotope ratios (δ202Hg, Δ199Hg) were measured in the muscle, liver, kidney, and intestine tissues of fish. Fish fed with food pellets spiked with varying concentrations of MMHg equilibrated to the isotopic composition of the food regardless of the tissue type and MMHg concentration. In contrast, fish fed with food pellets spiked with varying concentrations of IHg showed a tissue specific variation. Kidney and muscle tissues with relatively large proportions of MMHg from THg (>60%) exhibited small isotopic shifts toward the IHg food pellets after 3 months. The mercury isotope ratios of intestine comprised mostly of IHg (>90%) equilibrated to the isotopic composition of the food. Interestingly, liver tissues comprised mostly of MMHg (~100%) showed δ202Hg value that is ~0.7 permil higher than the IHg food pellet, suggesting the presence of significant mass-dependent fractionation (MDF) in the fish liver. Our study demonstrates how the isotope ratios of different mercury species behave in the internal system of fish and that the mechanism responsible for MDF needs to be elucidated particularly for using fish tissues to monitor sites contaminated with IHg.1
Tunable solvation structures for fast charging of micron-Si anodes in energy-dense lithium-ion batteries
No full textRealization of electrification in transportation and other applications depends on lithium-ion battery performance. Although micron-silicon (mu -Si) anodes enable energy-dense batteries, their rapid charging capability must be enhanced for electric vehicles. Additionally, significant volume changes of mu -Si anodes during lithiation and delithiation hinder their use in transportation. Herein, we reveal the mechanism of fluoroethylene carbonate (FEC) in tuning the solvation structure and topology of the solid-electrolyte interphase (SEI) for fast charging mu -Si/NCM811 full cells with reduced volume changes. The weak solvating nature of FEC allows PF6- anions to participate in the primary solvation sheath, improving Li+ desolvation kinetics and facilitating anode lithiation at rapid charge rates. This interaction forms SEI nanograins that enhance mechanical integrity and provide multiple ion paths. Notably, mu -Si/NCM811 full cells, with 99.5 % Coulombic efficiency, leveraging FEC for salt dissociation retain 76.6 % of their original capacity after 100 cycles at 3C; in contrast, electrolytes utilizing FEC as a cosolvent show a significantly poor capacity-retention performance. This study offers a comprehensive understanding of solvation chemistry and SEI engineering to improve fast-charging performance in mu -Si anodes.
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