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    The DOE Science News Source is a Newswise initiative to promote research news from the Office of Science of the DOE to the public and news media.
    • 2018-12-19 14:05:38
    • Article ID: 705640

    Clarifying Rates of Methylmercury Production

    New model provides more accurate estimates of how fast microbes produce a mercury-based neurotoxin.

    • Credit: Oak Ridge National Laboratory

      East Fork Poplar Creek with illustration showing transformation of inorganic mercury to methylmercury through microorganisms.

    The Science

    While volcanoes and forest fires release mercury, they are relatively small sources compared to the combustion of coal, oil, and other fuels. Mercury is toxic. Microbes turn mercury into a neurotoxin called methylmercury. They also turn the neurotoxin back into inorganic mercury. To predict the levels of inorganic mercury and methylmercury in the environment, scientists need to know how fast microbes act. Using new experiments and re-analyses of previous experiments, scientists developed a model that describes the production of methylmercury over time. The new model takes into account competing processes and results in faster rates of production than previously estimated.

    The Impact

    With the new model, scientists can simulate methylmercury production and transport. The model shows that methylmercury production is likely much larger than current estimates. Why does this matter? Methylmercury has adverse effects on young children and developing embryos. Better predicting mercury levels helps experts protect people and the environment.

    Summary

    Mercury is a toxic element that occurs naturally and as an anthropogenic pollutant in the environment. The neurotoxin monomethylmercury (MMHg) is a particular concern because it biomagnifies in aquatic environments and has adverse development effects on young children and developing embryos. MMHg is formed in the environment from inorganic mercury through the action of microorganisms in a process called mercury methylation. Because of its toxicity, scientists have attempted, numerous times, to measure mercury methylation and MMHg demethylation rates in various environmental settings with differing results. Even in laboratory experiments, rates for the methylation of mercury to MMHg often exhibit kinetics that are inconsistent with first-order kinetic models. In a new study, scientists from Oak Ridge National Laboratory used time-resolved measurements of filter-passing mercury and MMHg during methylation/demethylation assays, and they re-analyzed previous assays. Then they used a multi-site kinetic sorption model to show that competing kinetic sorption reactions can lead to apparent non-first-order kinetics in mercury methylation and MMHg demethylation. The new model can describe the range of behaviors for time-resolved methylation/demethylation data reported in the literature including those that exhibit non-first-order kinetics. Additionally, the team showed that neglecting competing sorption processes could confound analyses of methylation/demethylation assays, resulting in rate constant estimates that are systematically biased low. Simulations of MMHg production and transport in a hypothetical periphyton biofilm bed illustrate the implications of the new model and demonstrate that methylmercury production may be significantly different from projected by single-rate first-order models.

    Funding

    This work was funded by the Department of Energy, Office of Science, Biological and Environmental Research, Subsurface Biogeochemical Research Program and is a product of the Science Focus Area at Oak Ridge National Laboratory. The isotopes used in this research were supplied by the Department of Energy, Office of Science, Office of Nuclear Physics, Isotope Program.

    Publications

    T.A. Olsen, K.A. Muller, S.L. Painter, and S.C. Brook, “Kinetics of mercury methylation revisited.” Environmental Science & Technology 52(4), 2063 (2018). [DOI: 10.1021/acs.est.7b05152]

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    Peering into the Mist: How Water Vapor Changes Metal at the Atomic Level

    New insights into molecular-level processes could help prevent corrosion and improve catalytic conversion.

    Neutron science publications reach new highs at ORNL's flagship facilities

    The High Flux Isotope Reactor and the Spallation Neutron Source at the Department of Energy's Oak Ridge National Laboratory have reached new levels of increased science productivity. In 2018, a record high of more than 500 scientific instrument publications were produced between HFIR and SNS--based on neutron beamline experiments conducted by more than 1,200 US and international researchers who used the world-leading facilities.

    Fiery sighting: A new physics of eruptions that damage fusion experiments

    Feature describes first direct sighting of a trigger for bursts of heat that can disrupt fusion reactions.

    Microbial Types May Prove Key to Gas Releases from Thawing Permafrost

    Scientists discover key types of microbes that degrade organic matter and release carbon dioxide and methane into the atmosphere.

    An effect that Einstein helped discover 100 years ago offers new insight into a puzzling magnetic phenomenon

    Experiments at the Department of Energy's SLAC National Accelerator Laboratory have seen for the first time what happens when magnetic materials are demagnetized at ultrafast speeds of millionths of a billionth of a second: The atoms on the surface of the material move, much like the iron bar did. The work, done at SLAC's Linac Coherent Light Source (LCLS) X-ray laser, was published in Nature earlier this month.

    Found: A precise method for determining how waves and particles affect fusion reactions

    Like surfers catching ocean waves, particles within plasma can ride waves oscillating through the plasma during fusion energy experiments. Now a team of physicists led by PPPL has devised a faster method to determine how much this interaction contributes to efficiency loss in tokamaks.

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    In a recent study from the U.S. Department of Energy's (DOE) Argonne National Laboratory, scientists have combined two membrane-bound protein complexes to perform a complete conversion of water molecules to hydrogen and oxygen.

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    Scientists Identify Gene Cluster in Budding Yeasts with Major Implications for Renewable Energy

    How yeast partition carbon into a metabolite may offer insights into boosting production for biofuels.

    Nanocrystals Get Better When They Double Up With MOFs

    Researchers from Lawrence Berkeley National Laboratory (Berkeley Lab) have designed a dual-purpose material out of a self-assembling MOF (metal-organic framework)-nanocrystal hybrid that could one day be used to store carbon dioxide gas molecules for the manufacture of new chemicals and fuels.


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    Top 10 Discoveries of 2018

    Every year, the U.S. Department of Energy's (DOE) Brookhaven National Laboratory compiles a list of the biggest advances made by the Lab's staff scientists, engineers, and visiting researchers. From uncovering mysteries of the universe to building better batteries, here, in no particular order, are our picks for the top 10 discoveries of 2018.

    U.S. Department of Energy Announces $33 Million for Small Business Research and Development Grants

    The U.S. Department of Energy announced it will award 189 grants totaling $33 million to 149 small businesses in 32 states.

    DOE to Provide $16 Million for New Research into Atmospheric and Terrestrial Processes

    The U.S. Department of Energy (DOE) announced a plan to provide $16 million for new observational research aimed at improving the accuracy of today's climate and earth system models.

    Machine learning award powers Argonne leadership in engine design

    When attempting to design engines to be more fuel-efficient and emissions-free, automotive manufacturers have to take into account all the complexity inherent in the combustion process.

    ORNL partners with industry to address multiple nuclear technology challenges

    The Department of Energy's Oak Ridge National Laboratory is collaborating with industry on six new projects focused on advancing commercial nuclear energy technologies that offer potential improvements to current nuclear reactors and move new reactor designs closer to deployment.

    Lithium earns honors for three physicists working to bring the energy that powers the sun to Earth

    Feature describes research of three PPPL physicists who have won the laboratory's 2018 outstanding research awards

    DOE approves technical plan and cost estimate to upgrade Argonne facility; Project will create X-rays that illuminate the atomic scale, in 3D

    The U.S. Department of Energy has approved the technical scope, cost estimate and plan of work for an upgrade of the Advanced Photon Source, a major storage-ring X-ray source at Argonne.

    Costas Soukoulis elected to National Academy of Inventors

    Costas Soukoulis, Ames Laboratory senior scientist and Iowa State University Frances M. Craig Endowed Chair and Distinguished Professor, has been named as a 2018 National Academy of Inventors (NAI) Fellow.

    Biophysicist F. William Studier Elected Fellow of the National Academy of Inventors

    F. William Studier, a Senior Biophysicist Emeritus at the U.S. Department of Energy's Brookhaven National Laboratory and Adjunct Professor of Biochemistry at Stony Brook University, has been elected as a Fellow of the National Academy of Inventors (NAI). He is among 148 renowned academic inventors being recognized by NAI for 2018.

    Blast to the future

    A grant from DOE's Technology Commercialization Fund will help researchers at Argonne and industry partners seek improvements to U.S. manufacturing by making discovery and design of new materials more efficient.


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    Peering into the Mist: How Water Vapor Changes Metal at the Atomic Level

    New insights into molecular-level processes could help prevent corrosion and improve catalytic conversion.

    Microbial Types May Prove Key to Gas Releases from Thawing Permafrost

    Scientists discover key types of microbes that degrade organic matter and release carbon dioxide and methane into the atmosphere.

    New Method Knocks Out Yeast Genes with Single-Point Precision

    Researchers can precisely study how different genes affect key properties in a yeast used industrially to produce fuel and chemicals.

    How Plants Regulate Sugar Deposition in Cell Walls

    Identified genes involved in plant cell wall polysaccharide production and restructuring could aid in engineering bioenergy crops.

    Scientists Identify Gene Cluster in Budding Yeasts with Major Implications for Renewable Energy

    How yeast partition carbon into a metabolite may offer insights into boosting production for biofuels.

    More Designer Peptides, More Possibilities

    A combined experimental and modeling approach contributes to understanding small proteins with potential use in industrial, therapeutic applications.

    Deep Learning for Electron Microscopy

    Artificial intelligence on Summit to discover atomic-scale structures.

    Clarifying Rates of Methylmercury Production

    New model provides more accurate estimates of how fast microbes produce a mercury-based neurotoxin.

    Drought Stress Changes Microbes Living at Sorghum's Roots

    Scientists explore how drought-tolerant plants communicate to nearby microorganisms, suggesting ways to engineer more resilient bioenergy crops.

    How to Best Predict Chemical Reactions of Contaminants in Water

    Scientists determine the accuracy of computational methods used to study the sulfate radical approach to purifying water.


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