Challenging Radionuclides in Environment at the Atomic Scale: Issues in Waste Disposal and Fukushima
Monday 27th June 11:45 - 12:45 in Main Hall
Radionuclides are beneficial in many instances such as power generation, industrial, medical, and geochronological applications. Conversely, some fission products and actinides produced in nuclear reactors are radiotoxic and have long half-lives. These radionuclides need to be isolated and safely stored for geological periods; however, there have been instances where the release of these radionuclides has caused serious environmental issues. In such instances, the release of these radionuclides is governed by their interaction with inorganic, organic, and biological substances at the molecular scale in the Earth’s surface and sub-surface. Naturally-occurring nano-particles and microorganisms also play an important role in facilitating or retarding the migration of low-solubility radionuclides. The migration processes at the nano- and atomic-scales have been illustrated by atomic-resolution transmission electron microscopy (TEM). TEM is a powerful technique that enables us to investigate the structural and chemical properties of these particles at scales ranging from micron to sub-angstrom. This talk will address some of the observable microscopic phenomena that can impact the migration of radionuclides in surface and subsurface environments; physical and chemical alteration of nuclear waste and UO2+x, colloid-facilitated transport, microbial nanocrystallization of rare earth elements that are used as surrogate of trivalent actinides, the interaction between nanoparticles and microorganisms, and most recently contamination at Fukushima. At the present, 134Cs and 137Cs are important dose contributors, and their radioactivity will remain in soils, mainly fixed in the form of submicron-sized clay minerals. Some of the particles associated with Cs are transported while surface soils are run off. On the other hand, at the initial stage of Cs release from Fukushima Daiichi Nuclear Power Plant, low-solubility Cs-rich micro-particles, which contain up to ~36 wt% of Cs as Cs2O, are responsible for ~90% of the radioactivity (rather than soluble forms of Cs such as CsOH). The interior of these particles exhibit evidence of various nanoscale processes in the molten core-concrete interaction (MCCI) that occurred subsequent to melt down in the primary containment vessel. Still, these particles play an important role in the dispersion of low-volatile radionuclides into the surrounding environment. The latter half of the talk will highlight various microscopic but critical phenomena in Fukushima as unveiled by state-of-the-art TEM investigations
About the speaker, Satoshi Utsunomiya:
Satoshi Utsunomiya is an Associate Professor in the Department of Chemistry, Kyushu University. He obtained M.S. and Ph.D. degrees from the Mineralogical Institute, University of Tokyo, under the supervision of Professor Takashi Murakami. Then, he spent six and half years in the U.S. working as a post-doctoral fellow and assistant research scientist at University of Michigan with Professor Rodney C. Ewing before joining Kyushu University in 2007. His research focuses on application of advanced electron microscopy to environmental and geological materials to understand the principle mechanisms of various environmental issues. He became a fellow of Mineralogical Society of America in 2013.
The Volatile Input to Volcanoes and Eruption
Tuesday 28th June 11:45 - 12:45 in Main Hall
As of this writing, eighteen volcanoes are in a state of eruption or unrest; seventeen of those are on a convergent plate margin. The eruption of basalt to andesite at arc volcanoes is the most common global event, and yet little is understood of what controls their eruptive vigor. The obvious driver of explosivity is the volatile fuel, with H2O being the most abundant species. This plenary talk will present data on the parental abundances of H2O, and its degassing rate, as recorded in melt inclusions and chemical diffusion profiles in crystals and melt. The last fifteen years have seen intensive study of magmatic volatiles through the analysis of melt inclusions trapped largely in olivine crystals from airfall deposits. The unexpected observation is the uniformity in the water concentration of parental arc magmas: 4 +/ -1 wt% H2O (n~60 volcanoes) . Given the 4-5 orders of magnitude in eruptive intensity that produced these deposits, it does not seem likely that such a small range in H2O is the driving factor. Instead, magma decompression rate may affect explosive behavior through its control on bubble-melt separation, bubble- crystal nucleation, and/or magma supply rate. Several chronometers have been developed over the past years that capture the minutes-to-hours of magma decompression prior to explosive eruption using the diffusion of H2O in and through olivine, clinopyroxene and melt. The greatest uncertainty in this approach lies in the diffusivity of water through olivine and cpx, which varies by 5 orders of magnitude depending on the site occupancy of the hydrogen and abundance of other cations . The simultaneous application of multiple chronometers to the same eruptions provides permissible diffusivities, and demonstrates that water diffusion through olivine and cpx phenocrysts occurs at the rates comparable to the fastest measured in the laboratory, generally associated with exchange between Fe3+ and H+. Although this is bad news for the preservation of primary water in nominally anhydrous minerals, it is good news for eruptive chronometers. The application of diffusion chronometry to several eruptions thus far demonstrates a relationship between decompression rate and eruptive vigor, with magma ascending in minutes from 5-10 km depth magma storage regions in VEI 4-5 eruptions.
About the speaker, Terry Plank:
I am currently the Arthur D. Storke Professor of Earth Science Lamont Doherty Earth Observatory of Columbia University and my research is focused on magmas associated with the plate tectonic cycle, at both divergent and convergent plate margins. My main contributions have been to the understanding of: * Magma generation: quantifying the roles of decompression, temperature and water in driving mantle melting * Crustal recycling at subduction zones: providing global flux estimates of marine sediment subducted into oceanic trenches, and tracing sediment geochemically from the seafloor to arc volcanoes * Water content of magmas, and the effects on magma evolution and source composition. My tools are geochemical, field work has taken me to Nicaragua and the Aleutians, and to sea. I has served on the MARGINS steering committee, the editorial boards of Geology and Earth & Planetary Science Letters, the USArray Advisory Committee, the Bowen Award selection committee, NSF review panels, and as co-chief scientist on Leg 185 of the Ocean Drilling Program. I have received the Houtermans Medal from the European Association for Geochemistry, the Donath Medal from the Geological Society of America, I am a Fellow of the American Geophysical Union, the Geochemical Society, the Geological Society of America, and the Mineralogical Society of America. In 2012 I was named a MacArthur Foundation Fellow, and in 2013 elected into the National Academy of Sciences. Some of my projects include: Mantle dynamics and magmatism across the Basin and Range Volatiles In arc magmas Fast diffusion clocks of volcanic processes Pressure-temperature conditions of melting in subduction zones.
Liane G Benning
Why Greenland Melts: A Geo-Bio-Interface Perspective
Wednesday 29th June 11:45 - 12:45 in Main Hall
Concerns are growing about how fast and how much the Greenland Ice Sheet (GrIS) is melting, how this contributes to sea level rise and to what extent the released solutes and particles change the biogeochemical cycles and coastal ecosystems in the N Atlantic. Changes in the surface energy- and mass balance of the GrIS are linked to albedo, which is a response to the GrIS surface darkening through changes in snow and ice properties and the presence of light absorbing impurities (LAI). This darkening of the GrIS snow and ice surfaces is an important feedback to global temperature changes. Although, traditionally LAI were assumed to be solely Aeolian delivered black carbon and mineral dust, recently bio- albedo factors have been recognized as important, yet not well quantified parameters that affect surface albedo. Biological processes highly dynamic particularly during the ever increasing summer melt seasons. Such summer melt associated blooms of pigmented snow and ice algae will, in contrast to black carbon and mineral dust, rapidly respond to changes in the timing and duration of the annual melt seasons. As the climate warms and melt seasons become longer, such biological habitats will expand and increasingly contribute to the darkening of the GrIS, yet these bio-albedo effects are currently not included in predictive numerical models. These changes in summer melt season length and extent also dramatically affect the delivery of icebergs and meltwaters and their entrained particulates to the N-Atlantic Ocean. Such processes in turn regulate the fluxes of dissolved and particulate elements (e.g., Fe, Si, P etc.). Such processes affect not just local environments but are important on a global scale, especially in a warming climate scenario.
About the speaker, Liane G Benning:
Liane G. Benning is a Professor in Interface Geochemistry at the German Research Center for Geosciences (GFZ) and the Free University of Berlin and a Professor of Experimental Biogeochemistry at the School of Earth and Environment, University of Leeds. We focuses on quantitatively evaluating (bio) chemical reactions that shape Earth surface environments via experimental and field studies.
Chemical Evolution of the Solar System: Laboratory Experiments and Small-Body Explorations
Thursday 30th June 11:45 - 12:45 in Main Hall
The Solar System formed by the collapse of the Sun’s parent molecular cloud, containing nuclides synthesized in ancestor stars, ∼4.57 billion years ago. The infant Sun was surrounded by a protosolar disk. Silicate dust, ice and organic materials, which are heritages from the interstellar medium, were thermally processed in the protosolar disk (evaporation/condensation, melting/crystallization, gas-solid reaction, annealing, and so on), resulting in the formation of chondritic components and elemental/isotopic fractionations recorded in chondrites and terrestrial planets. Chemically- processed solid components accumulated to form planetesimals, where metamorphism and aqueous alteration subsequently tool place. Planet formation followed in the final stage of the disk evolution. Gas giants captured disk gas prior to the disk dissipation. Terrestrial planets formed in the dry inner region of the disk inside the snow line, but volatiles including water were delivered at some point. A key to understand the origin and early evolution of the Solar System is undoubtedly the analysis of extraterrestrial samples. However, in order to extract the quantitative information on physical and chemical conditions and the timescale of chemical evolution, laboratory experiments simulating chemical reactions in astronomical environments are critical elements. In this talk, I will address laboratory experiments on circumstellar dust formation, molecular cloud chemistry, formation of chondritic components, and dust evolution in the protosolar disk [e.g., 1-3]. Another key element is to expand our collection of extraterrestrial materials without any collection bias and terrestrial contamination. New sets of samples will be delivered in early 2020’s from two primitive near-Earth asteroids, Ryugu and Bennu, by Hayabusa2 (2014–2020)  and OSIRIS-REx (2016– 2023) . The scientific significance of small-body explorations to understand the Solar-System evolution will also be addressed in the talk.
About the speaker, Shogo Tachibana:
My primary research interests are the origin and evolution of the solar system and the chemical diversity within planets. I conduct laboratory experiments to simulate chemical reactions occurring around evolved stars, in protoplanetary disks, and within asteroids and planets. I compare my experimental results with observations, analyses of natural samples, and models to elucidate the chemical evolution of the solar system, planets, and the Earth.
Deep Time, Deep Earth: Revealing Earth's Early History
Friday 1st July 11:45 - 12:45 in Main Hall
The last 20 years has produced a revolution in our understanding of the first billion years of Earth history, moving from the exciting field discoveries of surviving rock and mineral relicts to increasingly sophisticated reconstructions of the timing and processes that shaped the young planet. The most direct information comes from chemical information contained in the ancient rock and mineral record such that identification of new localities of >3,600 Ma rocks and minerals combined with advances in analytical approaches continues to illuminate the formerly “dark ages” of Earth history. At least ten Eoarchean to Hadean terranes are now known worldwide. In all cases however, these terranes have undergone a range of thermal and tectonic processes since they formed, requiring integrated field, petrologic and geochemical studies to accurately recover and interpret an increasingly rich and diverse suite of geochemical signatures. Ultra-precise measurement of subtle isotopic differences produced from now extinct nuclides provides undisputed evidence of Hadean geological events. These small isotopic anomalies, as compared with signatures in modern rocks, not only constrain the timing of differentiation events in the first 500 million years of Earth history and enable direct comparisons with lunar and meteorite events, but also serve as tracers of mantle dynamics through time. The types of tectonic processes operative on the early Earth are debated, with some emerging observations used to argue that plate tectonic processes were producing new crust by at least 3.8 Ga, but that only limited amounts of Hadean continental crust were preserved into the Archean. Increased recognition and understanding of potential life habitats strengthens the case for ancient life. Key outstanding questions increasingly focus on how early life might have interacted with the geodynamic regime on the evolving Earth and what feedbacks were necessary to maintain habitability. In this talk we will take a modern look at the ancient rock record and highlight emerging work in this rapidly developing field.
About the speaker, Vickie Bennett:
Vickie C. Bennett is the Head of the Isotope Geochemistry Group and Associate Director at the Research School of Earth Sciences, Australian National University. Her activities are focussed on the application of mass spectrometry and radiogenic and stable isotope geochemistry to solving key questions about the early Earth, including: What was the origin and evolution of the Earth's continental crust? How and when did the various mantle chemical reservoirs form and evolve? How have the lithosphere and biosphere co-evolved? Answering these questions entails integrating geologic observations with a range of isotopic investigations preserved in Earth’s oldest (>3,500 million years old) rock record. Her main field focus is on the Archean terranes of southwest Greenland, but she has also worked in Western Australia, southwest U.S. and Antarctica. Dr. Bennett is a Fellow of the Geological Society of America and the Geochemical Society.