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  • ddc:550.724  (15)
  • ddc:551  (11)
  • Additives
  • perovskiteferroelectricpowder neutron diffraction
  • Springer Berlin Heidelberg  (27)
  • American Chemical Society  (2)
  • International Union of Crystallography (IUCr)  (2)
  • 1
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Walsh, A. N., Reddy, C. M., Niles, S. F., McKenna, A. M., Hansel, C. M., & Ward, C. P. Plastic formulation is an emerging control of its photochemical fate in the ocean. Environmental Science & Technology, 55(18), (2021): 12383–12392, https://doi.org/10.1021/acs.est.1c02272.
    Description: Sunlight exposure is a control of long-term plastic fate in the environment that converts plastic into oxygenated products spanning the polymer, dissolved, and gas phases. However, our understanding of how plastic formulation influences the amount and composition of these photoproducts remains incomplete. Here, we characterized the initial formulations and resulting dissolved photoproducts of four single-use consumer polyethylene (PE) bags from major retailers and one pure PE film. Consumer PE bags contained 15–36% inorganic additives, primarily calcium carbonate (13–34%) and titanium dioxide (TiO2; 1–2%). Sunlight exposure consistently increased production of dissolved organic carbon (DOC) relative to leaching in the dark (3- to 80-fold). All consumer PE bags produced more DOC during sunlight exposure than the pure PE (1.2- to 2.0-fold). The DOC leached after sunlight exposure increasingly reflected the 13C and 14C isotopic composition of the plastic. Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry revealed that sunlight exposure substantially increased the number of DOC formulas detected (1.1- to 50-fold). TiO2-containing bags photochemically degraded into the most compositionally similar DOC, with 68–94% of photoproduced formulas in common with at least one other TiO2-containing bag. Conversely, only 28% of photoproduced formulas from the pure PE were detected in photoproduced DOC from the consumer PE. Overall, these findings suggest that plastic formulation, especially TiO2, plays a determining role in the amount and composition of DOC generated by sunlight. Consequently, studies on pure, unweathered polymers may not accurately represent the fates and impacts of the plastics entering the ocean.
    Description: Funding was provided by the Seaver Institute, the Gerstner Family Foundation, Woods Hole Oceanographic Institution, and the National Science Foundation Graduate Research Fellowship Program (A.N.W.). The Ion Cyclotron Resonance user facility at the National High Magnetic Field Laboratory is supported by the National Science Foundation Division of Chemistry and Division of Materials Research through DMR-1644779 and the State of Florida.
    Keywords: Plastic pollution ; Marine debris ; Additives ; Dissolved organic carbon ; Photochemical oxidation ; FT-ICR-MS ; Titanium dioxide
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2022-12-07
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in James, B., de Vos, A., Aluwihare, L., Youngs, S., Ward, C., Nelson, R., Michel, A., Hahn, M., & Reddy, C. Divergent forms of pyroplastic: lessons learned from the M/V X-Press Pearl ship fire. ACS Environmental Au, 2(5), (2022): 467–479, https://doi.org/10.1021/acsenvironau.2c00020.
    Description: In late May 2021, the M/V X-Press Pearl container ship caught fire while anchored 18 km off the coast of Colombo, Sri Lanka and spilled upward of 70 billion pieces of plastic or “nurdles” (∼1680 tons), littering the country’s coastline. Exposure to combustion, heat, chemicals, and petroleum products led to an apparent continuum of changes from no obvious effects to pieces consistent with previous reports of melted and burned plastic (pyroplastic) found on beaches. At the middle of this continuum, nurdles were discolored but appeared to retain their prefire morphology, resembling nurdles that had been weathered in the environment. We performed a detailed investigation of the physical and surface properties of discolored nurdles collected on a beach 5 days after the ship caught fire and within 24 h of their arrival onshore. The color was the most striking trait of the plastic: white for nurdles with minimal alteration from the accident, orange for nurdles containing antioxidant degradation products formed by exposure to heat, and gray for partially combusted nurdles. Our color analyses indicate that this fraction of the plastic released from the ship was not a continuum but instead diverged into distinct groups. Fire left the gray nurdles scorched, with entrained particles and pools of melted plastic, and covered in soot, representing partial pyroplastics, a new subtype of pyroplastic. Cross sections showed that the heat- and fire-induced changes were superficial, leaving the surfaces more hydrophilic but the interior relatively untouched. These results provide timely and actionable information to responders to reevaluate cleanup end points, monitor the recurrence of these spilled nurdles, gauge short- and long-term effects of the spilled nurdles to the local ecosystem, and manage the recovery of the spill. These findings underscore partially combusted plastic (pyroplastic) as a type of plastic pollution that has yet to be fully explored despite the frequency at which plastic is burned globally.
    Description: This work was supported by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution (WHOI), with funding provided by the Weston Howland Jr. Postdoctoral Scholarship. Additional support was provided by the WHOI Marine Microplastics Catalyst Program, the WHOI Marine Microplastics Innovation Accelerator Program, the WHOI Investment in Science Fund, the March Marine Initiative (a program of March Limited, Bermuda), The Seaver Institute, Gerstner Philanthropies, the Wallace Research Foundation, the Richard Saltonstall Charitable Foundation, the Harrison Foundation, Hollis and Ermine Lovell Charitable Foundation, and the Richard Grand Foundation. AdV was supported by funding from the Schmidt Foundation.
    Keywords: Microplastic ; Resin pellets ; Pollution ; Additives ; Open burning ; Weathering ; Maritime accident
    Repository Name: Woods Hole Open Access Server
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  • 3
    Publication Date: 2023-06-20
    Description: Aufgrund deutlich erhöhter Wärmebedarfsdichten urbaner Räume besteht in besonderem Maße hier die Möglichkeit und Erfordernis, durch eine nachhaltige Wärmeversorgung und saisonale Wärmespeicherung im geologischen Untergrund einen wesentlichen Beitrag zu den national und international gesetzten Klimaschutzzielen zu liefern. Eine effiziente Möglichkeit zur Wärmegewinnung und -speicherung bieten hierfür Erdwärmesonden, die jedoch aus Gründen des vorbeugenden Grundwasserschutzes in Bereichen der Trinkwassernutzung heutzutage meist nicht oder nur beschränkt genehmigt werden. Numerische Simulationen einer Erdwärmesondenleckage für Randbedingungen eines zur Trinkwassergewinnung genutzten norddeutschen Aquifers auf Grundlage von aufgearbeiteten stoffspezifischen Abbauratenkonstanten zeigen, dass Grenzwerte für die meisten handelsüblichen Wärmeträgerfluid-Inhaltsstoffe bereits bei einem Abstand von nur 100 m zwischen Erdwärmesonde und Trinkwasserentnahme aufgrund starker Verdünnung und mikrobiellen Abbaus mit einem Faktor 〉 10 unterschritten werden. Vor dem Hintergrund dieser Ergebnisse und angesichts der Zielsetzung einer Reduktion fossiler Primärenergiequellen um 80–95 % bis 2050, erscheinen pauschale Abstandsvorgaben (von zurzeit 〉 1000 m) daher zumindest hinsichtlich der Trinkwassergefährdung durch Erdwärmesondenleckagen diskussionswürdig.
    Description: Christian-Albrechts-Universität zu Kiel (3094)
    Keywords: ddc:549 ; Borehole heat exchanger ; Heat transfer fluids ; Additives ; Groundwater ; Risk assessment
    Language: German
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  • 4
    Publication Date: 2023-06-23
    Description: Magmas vesiculate during ascent, producing complex interconnected pore networks, which can act as outgassing pathways and then deflate or compact to volcanic plugs. Similarly, in-conduit fragmentation events during dome-forming eruptions create open systems transiently, before welding causes pore sealing. The percolation threshold is the first-order transition between closed- and open-system degassing dynamics. Here, we use time-resolved, synchrotron-source X-ray tomography to image synthetic magmas that go through cycles of opening and closing, to constrain the percolation threshold ΦC at a range of melt crystallinity, viscosity and overpressure pertinent to shallow magma ascent. During vesiculation, we observed different percolative regimes for the same initial bulk crystallinity depending on melt viscosity and gas overpressure. At high viscosity (〉 106 Pa s) and high overpressure (~ 1–4 MPa), we found that a brittle-viscous regime dominates in which brittle rupture allows system-spanning coalescence at a low percolation threshold (ΦC~0.17) via the formation of fracture-like bubble chains. Percolation was followed by outgassing and bubble collapse causing densification and isolation of the bubble network, resulting in a hysteresis in the evolution of connectivity with porosity. At low melt viscosity and overpressure, we observed a viscous regime with much higher percolation threshold (ΦC 〉 0.37) due to spherical bubble growth and lower degree of crystal connection. Finally, our results also show that sintering of crystal-free and crystal-bearing magma analogues is characterised by low percolation thresholds (ΦC = 0.04 – 0.10). We conclude that the presence of crystals lowers the percolation threshold during vesiculation and may promote outgassing in shallow, crystal-rich magma at initial stages of Vulcanian and Strombolian eruptions.
    Description: Paul Scherrer Institut http://dx.doi.org/10.13039/501100004219
    Description: European Research Council http://dx.doi.org/10.13039/501100000781
    Description: NERC
    Description: Deutsche Forschungsgemeinschaft
    Keywords: ddc:550.724 ; Effusive-explosive transition ; Percolation threshold ; Outgassing ; Crystal-rich magma ; Magma viscosity ; Gas overpressure ; Porosity ; Pore connectivity ; Hysteresis ; Strombolian/Vulcanian eruptions ; Dome-forming eruptions
    Language: English
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  • 5
    Publication Date: 2023-06-23
    Description: Magma ascent during silicic dome-forming eruptions is characterized by significant changes in magma viscosity, permeability, and gas overpressure in the conduit. These changes depend on a set of parameters such as ascent rate, outgassing and crystallization efficiency, and magma viscosity, which in turn may influence the prevailing conditions for effusive versus explosive activity. Here, we combine chemical and textural analyses of tephra with viscosity models to provide a better understanding of the effusive-explosive transitions during Vulcanian phases of the 9.4 ka eruption of Kilian Volcano, Chaîne des Puys, France. Our results suggest that effusive activity at the onset of Vulcanian episodes at Kilian Volcano was promoted by (i) rapid ascent of initially crystal-poor and volatile-rich trachytic magma, (ii) a substantial bulk and melt viscosity increase driven by extensive volatile loss and crystallization, and (iii) efficient degassing/outgassing in a crystal-rich magma at shallow depths. Trachytic magma repeatedly replenished the upper conduit, and variations in the amount of decompression and cooling caused vertical textural stratification, leading to variable degrees of crystallization and outgassing. Outgassing promoted effusive dome growth and occurred via gas percolation through large interconnected vesicles, fractures, and tuffisite veins, fostering the formation of cristobalite in the carapace and talus regions. Build-up of overpressure was likely caused by closing of pore space (bubbles and fractures) in the dome through a combination of pore collapse, cristobalite formation, sintering in tuffisite veins, and limited pre-fragmentation coalescence in the dome or underlying hot vesicular magma. Sealing of the carapace may have caused a transition from open- to closed- system degassing and to renewed explosive activity. We generalize our findings to propose that the broad spectrum of eruptive styles for trachytic magmas may be inherited from a combination of characteristics of trachytic melts that include high water solubility and diffusivity, rapid microlite growth, and low melt viscosity compared to their more evolved subalkaline dacitic and rhyolitic equivalents. We show that trachytes may erupt with a similar style (e.g., Vulcanian) but at significantly higher ascent rates than their andesitic, dacitic, and rhyolitic counterparts. This suggests that the periodicity of effusive-explosive transitions at trachytic volcanoes may differ from that observed at the well-monitored andesitic, dacitic, and rhyolitic volcanoes, which has implications for hazard assessment associated with trachytic eruptions.
    Description: ERC ADV 2018
    Keywords: ddc:550.724 ; Effusive-explosive transitions ; Trachytic magma ; Vulcanian eruption ; Magma Viscosity ; Crystallization ; Degassing ; Nanolites ; Cristobalite
    Language: English
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  • 6
    Publication Date: 2023-06-23
    Description: Subsurface magmatic–hydrothermal systems are often associated with elevated electrical conductivities in the Earthʼs crust. To facilitate the interpretation of these data and to allow distinguishing between the effects of silicate melts and fluids, the electrical conductivity of aqueous fluids in the system H 2 O–HCl was measured in an externally heated diamond anvil cell. Data were collected to 700 °C and 1 GPa, for HCl concentrations equivalent to 0.01, 0.1, and 1 mol/l at ambient conditions. The data, therefore, more than double the pressure range of previous measurements and extend them to geologically realistic HCl concentrations. The conductivities 𝜎 (in S/m) are well reproduced by a numerical model log 𝜎 = −2.032 + 205.8 T−1 + 0.895 log c + 3.888 log 𝜌 + logΛ0(T,𝜌), where T is the temperature in K, c is the HCl concentration in wt. %, and 𝜌 is the density of pure water at the corresponding pressure and temperature conditions. Λ0(T,𝜌) is the limiting molar conductivity (in S cm2 mol −1 ) at infinite dilution, Λ0(T,𝜌) = 2550.14 − 505.10𝜌 − 429,437 T−1 . A regression fit of more than 800 data points to this model yielded R2 = 0.95. Conductivities increase with pressure and fluid densities due to an enhanced dissociation of HCl. However, at constant pressures, conductivities decrease with temperature because of reduced dissociation. This effect is particularly strong at shallow crustal pressures of 100–200 MPa and can reduce conductivities by two orders of magnitude. We, therefore, suggest that the low conductivities sometimes observed at shallow depths below the volcanic centers in magmatic–hydrothermal systems may simply reflect elevated temperatures. The strong negative temperature effect on fluid conductivities may offer a possibility for the remote sensing of temperature variations in such systems and may allow distinguishing the effects of magma intrusions from changes in hydrothermal circulation. The generally very high conductivities of HCl–NaCl–H 2 O fluids at deep crustal pressures (500 MPa–1 GPa) imply that electrical conductors in the deep crust, as in the Altiplano magmatic province and elsewhere, may at least partially be due to hydrothermal activity.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Universität Bayreuth (3145)
    Keywords: ddc:550.724 ; Electrical conductivity ; Fluid ; HCl ; Hydrothermal systems ; Magnetotelluric data
    Language: English
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  • 7
    Publication Date: 2023-06-23
    Description: Hydrothermal eruptions are characterised by violent explosions ejecting steam, water, mud, and rock. They pose a risk to tourism and the operation of power plants in geothermal areas around the world. Large events with a severe destructive threat are often intensified by the injection of magmatic fluids along faults and fractures within volcano-tectonic rifting environments, such as the Taupo Volcanic Zone. How these hydrothermal eruptions progress, how craters form and the scale of ejecta impacts, are all influenced by the local geology and reservoir hydrology. By analysing breccia lithology, undisturbed strata proximal to the explosion sites, and conducting tailored decompression experiments, we elucidate the eruption sequence that formed Champagne Pool, Wai-o-tapu, New Zealand. This iconic touristic site was formed by a violent hydrothermal eruption at ~ 700 years B.P. Samples from undisturbed drill cores and blocks ejected in the eruption were fragmented in shock-tube experiments under the moderate pressure/temperature conditions estimated for this system (3–4 MPa, 210–220 °C). Our results show that this was a two-phase eruption. It started with an initial narrow jetting of deep-sourced lithologies, ejecting fragments from at least a 110-m depth. This event was overtaken by a larger, broader, and dominantly shallower eruption driven by decompression of much more geothermal fluid within a soft and porous ignimbrite horizon. The second phase was triggered once the initial, deeper-sourced eruption broke through a strong silicified aquitard cap. The soft ignimbrite collapsed during the second-phase eruption into the crater, to repeatedly choke the explosions causing short-term pressure rises that triggered ongoing deeper-sourced eruptions. The eruption spread laterally also by exploiting a local fault. These results are relevant for hydrothermal eruption hazard scenarios in environments where strong vertical variations in rock strength and porosity occur.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Ministry of Business, Innovation and Employment http://dx.doi.org/10.13039/501100003524
    Keywords: ddc:550.724 ; Hydrothermal eruptions ; Geothermal ; Champagne pool ; Experimental ; Eruption dynamics
    Language: English
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  • 8
    Publication Date: 2023-06-23
    Description: While Terzaghi justified his principle of effective stress for water-saturated soil empirically, it can be derived by means of the neutrality of the mineral with respect to changes of the pore water pressure p w. This principle works also with dilating shear bands arising beyond critical points of saturated grain fabrics, and with patterns of shear bands as relics of critical phenomena. The shear strength of over-consolidated clay is explained without effective cohesion, which results also from swelling up to decay, while rapid shearing of water-saturated clay can lead to a cavitation of pore water. The p w-neutrality is also confirmed by triaxial tests with sandstone samples, while Biot’s relation with a reduction factor for p w is contestable. An effective stress tensor is heuristically legitimate also for soil and rock with relics of critical phenomena, particularly for critical points with a Mohr–Coulomb condition. Therein, the p w-neutrality of the solid mineral determines the interaction of solid fabric and pore water, but numerical models are questionable due to fractal features.
    Description: Karlsruher Institut für Technologie (KIT) (4220)
    Keywords: ddc:550.724 ; Effective stress ; Interaction of solid fabric and pore water ; Pore pressure neutrality of mineral ; Shear bands and cracks
    Language: English
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  • 9
    Publication Date: 2023-06-23
    Description: In this work, a constitutive model able to capture the strain rate dependency, small strain effects and the inherent anisotropy is proposed considering the influence of the overconsolidation ratio (OCR). Small strain effects are captured by using an extended ISA plasticity formulation (Fuentes and Triantafyllidis in Int J Numer Anal Methods Geomech 39(11):1235–1254, 2015). The strain rate dependency is reproduced by incorporating a third strain rate mechanism (in addition to the elastic and hypoplastic strain rate). A loading surface has been incorporated to define a three-dimensional (3D) overconsolidation ratio and to account for its effects on the simulations. Experimental investigations using Kaolin Clay and Lower Rhine Clay with horizontal bedding plane have shown that under undrained cycles of small strain amplitudes (\10-4 ), the effective stress path in the p–q space is significantly inclined towards the left upper corner of the p - q plane. Consequently, a transversely (hypo)elastic stiffness has been successfully formulated to capture this behaviour. The performance of the model has been inspected by simulating the database of approximately 50 cyclic undrained triaxial (CUT) tests on low-plasticity Kaolin Clay (Wichtmann and Triantafyllidis) considering different deviatoric stress amplitudes, initial stress ratios, displacement rate, overconsolidation ratio and cutting direction. Furthermore, 4 CUT tests conducted on high-plasticity Lower Rhine Clay were simulated, whereby the influence of the displacement rate, as well as the deviatoric stress amplitude, has been analysed. The simulations showed a good congruence with the experimental observations.
    Keywords: ddc:550.724 ; Anisotropy ; Clay ; Cyclic loading ; Excessive pore water pressure ; Rate dependency ; Soft soils ; Silt ; Time dependency ; Viscosity
    Language: English
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  • 10
    Publication Date: 2023-06-17
    Description: Paleo-shorelines on continental shelves give insights into the complex development of coastlines during sealevel cycles. This study investigates the geologic development of the Limpopo Shelf during the last sealevel cycle using multichannel seismic and acoustic datasets acquired on the shelf in front of the Limpopo River mouth. A detailed investigation of seismic facies, shelf bathymetry, and a correlation to sea level revealed the presence of numerous submerged shorelines on the shelf. These shorelines are characterized by distinct topographic ridges and are interpreted as coastal dune ridges that formed in periods of intermittent sealevel still-/slowstand during transgression. The shorelines are preserved due to periods of rapid sealevel rise (melt water pulses) that led to the overstepping of the dune ridges as well as due to early cementation of accumulated sediments that increased the erosive resistance of the ridges. The high along-shelf variability of the submerged dune ridges is interpreted as a result of pre-existing topography affecting shoreline positions during transgression. The pre-existing topography is controlled by the underlying sedimentary deposits that are linked to varying fluvial sediment input at different points on the shelf. The numerous prominent submerged dune ridges form barriers for the modern fluvial sediment from the Limpopo River and dam sediment on the inner shelf. They may also facilitate along-shelf current-induced sediment transport.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551 ; Limpopo Shelf ; Geology
    Language: English
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