Identification of Uranyl Minerals Using Oxygen K‐Edge X‐Ray Absorption Spectroscopy          下载免费PDF全文

Jesse D. Ward  Mark Bowden  C. Tom Resch  Steven Smith  Bruce K. McNamara  Edgar C. Buck  Gregory C. Eiden  Andrew M. Duffin 《Geostandards and Geoanalytical Research》2016,40(1):135-148

Although most of the world's uranium exists as pitchblende or uraninite, this mineral can be weathered to a great variety of secondary uranium minerals, most containing the uranyl cation. Anthropogenic uranium compounds can also react in the environment, leading to spatial–chemical alterations that could be useful for nuclear forensics analyses. Soft X‐ray absorption spectroscopy (XAS) has the advantages of being non‐destructive, element‐specific and sensitive to electronic and physical structure. The soft X‐ray probe can also be focused to a spot size on the order of tens of nanometres, providing chemical information with high spatial resolution. However, before XAS can be applied at high spatial resolution, it is necessary to find spectroscopic signatures for a variety of uranium compounds in the soft X‐ray spectral region. To that end, we collected the near edge X‐ray absorption fine structure (NEXAFS) spectra of a variety of common uranyl‐bearing minerals, including uranyl carbonates, oxyhydroxides, phosphates and silicates. We find that uranyl compounds can be distinguished by class (carbonate, oxyhydroxide, phosphate or silicate) based on their oxygen K‐edge absorption spectra. This work establishes a database of reference spectra for future spatially resolved analyses. We proceed to show scanning X‐ray transmission microscopy (STXM) data from a schoepite particle in the presence of an unknown contaminant.  相似文献   

A New Generation Earth Mantle Model from Global Adjoint Tomography     

Youyi Ruan  Wenjie Lei  Matthieu Lefebvre  Ryan Modrak  James Smith  Ridvan Orsvuran  Ebru Bozdag  Judith Hill  Norbert Podhorszki  Dave Pugmire  Jeroen Tromp 《《地质学报》英文版》2018,92(Z1):140-140

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The British Palaeogene Volcanic Province - Ailsa Craig Geological Conservation Review site     

C.G. Smith  R.M.L. Wignall 《Proceedings of the Geologists' Association. Geologists' Association》2021,132(1):16-23

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When hazard avoidance is not an option: lessons learned from monitoring the postdisaster Oso landslide,USA     

Reid  Mark E.  Godt  Jonathan W.  LaHusen  Richard G.  Slaughter  Stephen L.  Badger  Thomas C.  Collins  Brian D.  Schulz  William H.  Baum  Rex L.  Coe  Jeffrey A.  Harp  Edwin L.  Schmidt  Kevin M.  Iverson  Richard M.  Smith  Joel B.  Haugerud  Ralph A.  George  David L. 《Landslides》2021,18(9):2993-3009

On 22 March 2014, a massive, catastrophic landslide occurred near Oso, Washington, USA, sweeping more than 1 km across the adjacent valley flats and killing 43 people. For the following 5 weeks, hundreds of workers engaged in an exhaustive search, rescue, and recovery effort directly in the landslide runout path. These workers could not avoid the risks posed by additional large-scale slope collapses. In an effort to ensure worker safety, multiple agencies cooperated to swiftly deploy a monitoring and alerting system consisting of sensors, automated data processing and web-based display, along with defined communication protocols and clear calls to action for emergency management and search personnel. Guided by the principle that an accelerating landslide poses a greater threat than a steadily moving or stationary mass, the system was designed to detect ground motion and vibration using complementary monitoring techniques. Near real-time information was provided by continuous GPS, seismometers/geophones, and extensometers. This information was augmented by repeat-assessment techniques such as terrestrial and aerial laser scanning and time-lapse photography. Fortunately, no major additional landsliding occurred. However, we did detect small headscarp failures as well as slow movement of the remaining landslide mass with the monitoring system. This was an exceptional response situation and the lessons learned are applicable to other landslide disaster crises. They underscore the need for cogent landslide expertise and ready-to-deploy monitoring equipment, the value of using redundant monitoring techniques with distinct goals, the benefit of clearly defined communication protocols, and the importance of continued research into forecasting landslide behavior to allow timely warning.

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The multiple chronological techniques applied to the Lake Suigetsu SG06 sediment core,central Japan     

Richard A. Staff  Takeshi Nakagawa  Gordon Schlolaut  Michael H. Marshall  Achim Brauer  Henry F. Lamb  Christopher Bronk Ramsey  Charlotte L. Bryant  Fiona Brock  Hiroyuki Kitagawa  Johannes van der Plicht  Rebecca L. Payne  Victoria C. Smith  Darren F. Mark  Alison Macleod  Simon P. E. Blockley  Jean‐Luc Schwenninger  Pavel E. Tarasov  Tsuyoshi Haraguchi  Katsuya Gotanda  Hitoshi Yonenobu  Yusuke Yokoyama  Suigetsu Project Members 《Boreas: An International Journal of Quaternary Research》2013,42(2):259-266

The varved sediment of Lake Suigetsu (central Japan) provides a valuable opportunity to obtain high‐resolution, multi‐proxy palaeoenvironmental data across the last glacial/interglacial cycle. In order to maximize the potential of this archive, a well‐constrained chronology is required. This paper outlines the multiple geochronological techniques being applied – namely varve counting, radiocarbon dating, tephrochronology (including argon–argon dating) and optically stimulated luminescence (OSL) – and the approaches by which these techniques are being integrated to form a single, coherent, robust chronology. Importantly, we also describe here the linkage of the floating Lake Suigetsu (SG06) varve chronology and the absolute (IntCal09 tree‐ring) time scale, as derived using radiocarbon data from the uppermost (non‐varved) portion of the core. This tie‐point, defined as a distinct (flood) marker horizon in SG06 (event layer B‐07–08 at 1397.4 cm composite depth), is thus derived to be 11 255 to 11 222 IntCal09 cal. years BP (68.2% probability range).  相似文献   

The effects of trophic interactions and spatial competition on algal community composition on Hawaiian coral reefs     

Mark J. A. Vermeij  Meghan L. Dailer  Sheila M. Walsh  Mary K. Donovan  Celia M. Smith 《Marine Ecology》2010,31(2):291-299

Much of coral reef ecology has focused on how human impacts change coral reefs to macroalgal reefs. However, macroalgae may not always be a good indicator of reef decline, especially on reefs with significant sea urchin populations, as found in Kenya and Hawaii. This study tests the effects of trophic interactions (i.e. herbivory by fishes and sea urchins) and spatial competition (between algae and coral) on algal community structure of reefs surrounding two Hawaiian Islands that vary in their level of human impacts. Reef‐building organisms (corals and crustose coralline algae) were less abundant and turf algae were more abundant on Maui as compared to Lanai, where human impacts are lower. In contrast to previous studies, we found no evidence that macroalgae increased with human impacts. Instead, low turf and macroalgal abundance were best explained by the interactive effects of coral cover and sea urchin abundance. Fishing sea urchin predators appeared to have cascading effects on the benthic community. The absence of sea urchin predators and high sea urchin densities correspond to a disproportionately high abundance of turf and crustose coralline algae. We propose that high turf algal abundance is a better indicator of reef decline in Hawaii than high macroalgal abundance because turf abundance was highest on reefs with low coral cover and few fish. The results of this study emphasize that understanding changes in community composition are context‐dependent and that not all degraded reefs look the same.  相似文献   

Structure and collapse of three-dimensional magnetic neutral points     

C. E. Parnell  T. Neukirch  J. M. Smith  E. R. Priest 《地球物理与天体物理流体动力学》2013,107(3-4):245-271

Abstract

The structure and collapse of linear three-dimensional magnetic neutral points is studied by varying the four parameters (p, q,j_|,j_⊥ ) that define, in general, the linear field of a neutral point. The effect of these parameters on both the skeleton structure (i.e. the fan and spine) and the actual field line structure of the null is considered. It is found that one current component (j_⊥ ) causes the skeleton structure of the null to fold up from its potential state, whereas the other current component (j _|;) causes the field lines to bend. The two other parameters (p,q) determine the potential structure of the null and cause the null to transform from a three-dimensional null to a two-dimensional null and from a positive (type B) null to a negative (type A) null.

To investigate the collapse of three-dimensional nulls, solutions to the linear, low-β ideal magnetohydrodynamic equations are found. It is found that three-dimensional null points can collapse if the field line foot-points are free and energy can propagate into the system.  相似文献   

MinIdent: An application to the identification and classification of amphiboles     

Dr. Ronald J. Goble  Dorian G. W. Smith 《Mineralogy and Petrology》1988,38(3):213-227

Summary Amphibole data in the MinIdent database (Smith andLeibovitz, 1986) were initially entered using species names quoted in the original source. The database has been updated by reclassifying these early data using the program AMPHTAB supplied by N. M. S. Rock and by adding supplemental data from the more recent literature, with the species names again checked using AMPHTAB. Associated MinIdent mineral identification software was utilized to determine which minerals in the database most closely resemble a series of unknown specimens chemically, as expressed in the Chemical Matching Index, CM, a relative figure-of-merit. Chemical data fromMogessie and Tessadri (1982) and Hawthorne (1983) were used to check the agreement between MinIdent and AMPHTAB for the classification of 221 unknown amphiboles.With 450 amphibole analyses entered and compiled in MinIdent, the name assigned by AMPHTAB showed the highest value of CM in MinIdent for 127 of the 221 unknown amphiboles (57.5°/x) and the second highest value for another 32 (14.5%). A chemically adjacent amphibole field had the highest value of CM for 59 of the 221 unknowns (26.7%), where chemically adjacent refers to a change in one chemical parameter. The greatest discrepancy between the two programs occurred in the hornblendes, with an agreement of just 20%, although for 58% of the unknowns the species with the highest CM in MinIdent was in a chemical field adjacent to the species name assigned by AMPHTAB. In many cases the disagreement between MinIdent and AMPHTAB could be ascribed to a lack of data in MinIdent.A comparison of the two programs suggests that the assignment of a single name to an unknown amphibole by AMPHTAB with no direct indication of its reliability may be; misleading. Standard analytical errors are frequently sufficient to overlap the arbitrary boundaries between amphibole species fields. In such cases it may be preferable to use a program such as MinIdent which, rather than assigning an arbitrary amphibole name, presents a list of 20 amphiboles with the degree of similarity between them and the unknown amphibole indicated. MinIdent offers the additional benefit of allowing input of other than chemical data and bases the match between unknown and standard data upon all input data. This will become more of an advantage as instruments such as automated refractometers become available for routine use.

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Zusammenfassung Ausgangspunkt war das Amphibol-Datenmaterial (Smith und Leibovitz, 1986) mit den dort verwendeten Artnamen. Diese Basisdaten wurden vervollständigt und erneuert durch Reklassifizierung mittels des AMPHTAB Programms, ergänzt durch N. M. S. Rock, und durch Hinzufügung weiterer Daten aus der neuesten Literatur, deren Speciesnamen wiederum mit AMPHTAB überprüft wurden. Außerdem wurde eine MinIdent Mineralidentifizierungs-Software verwendet, um die Minerale zu bestimmen, die in ihrem Chemismus am ehesten einer Serie von unbekannten Amphibol-Species entsprechen, wie sie im Chemical Matching Index (CM) aufscheinen. Zur Klassifikation von 221 unbekannten Amphibolen wurden chemische Daten von Mogessie und Tessadri (1982) verwendet um die Übereinstimmung zwischen MinIdent und AMPHTAB zu überprüfen.Unter den 450 in MinIdent zusammengestellten und eingegebenen Amphibolanalysen zeigen die bei AMPHTAB angegebenen die höchsten CM Werte, nämlich 127 von 221 unbekannten Amphibolen (57,5%) und weitere 32 (14,5%) die zweithöchsten Werte. Innerhalb eines chemisch benachbarten Amphibolfeldes hatten 59 der 221 unbekannten Amphibole (26,7%) die höchsten CM Werte, wobei unter achemisch benachbart die Änderung eines chemischen Parameters zu verstehen ist. Die größten Unterschiede zwischen den beiden Programmen traten bei den Hornblenden auf. Die Übereinstimmung lag bei nur 20%, obwohl bei 58% der unbekannten Amphibole die Species mit dem höchsten CM Wert in MinIdent in ein chemisches Feld zu liegen kamen, welches zu den bei AMPHTAB angegebenen Speciesnamen eine benachbarte Position einnimmt. Die Unterschiede zwischen MinIdent und AMPHTAB könnten in vielen Fällen auf ein Fehlen von Daten in MinIdent zurükzuführen sein.Ein Vergleich beider Programme deutet an, daß die Angabe eines Einzelnamens für ein unbekanntes Amphibol im AMPHTAB Programm ohne Angaben über die Zuverlässigkeit zu Mißverständnissen führen kann. Normale analytische Fehler können bereits dazu führen, daß die Grenzen zweier willkürlicher Amphibolfelder überlappen. In derartigen Fällen emphiehlt sich die Anwendung des MinIdent Programmes, welches eben nicht einen willkürlichen Amphibolnamen angibt, sondern eine Liste von 20 Amphibolen mit dem Grad ihrer Ähnlichkeit, und einem Hinweis auf den unbekannten Amphibol. MinIdent bietet den zusätzlichen Vorteil, daß man außer chemischen auch andere Daten eingeben kann, und stellt dann sämtliche Daten des unbekannten Amphibols den Standard Daten gegenüber. Dieser Klassifizierungsvorgang wird mit der zunehmenden Routineanwendung von automatischen Refraktometern verstärkte Anwendung finden.

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Generation of correlated properties in heterogeneous porous media   总被引：1，自引：0，他引：1  

P. R. King  P. J. Smith 《Mathematical Geology》1988,20(7):863-877

The spatial distribution of rock properties in porous media, such as permeability and porosity, often is strongly variable. Therefore, these properties usefully may be considered as a random field. However, this variability is correlated frequently on length scales comparable to geological lengths (for example, scales of sand bodies or facies). To solve various engineering problems (for example, in the oil recovery process) numerical models of a porous medium often are used. A need exists then to understand correlated random fields and to generate them over discretized numerical grids. The paper describes the general mathematical methods required to do this, with one particular method (the nearest neighbor model) described in detail. How parameters of the mathematical model may be related to rock property statistics for the nearest neighbor model is shown. The method is described in detail in one, two, and three dimensions. Examples are given of how model parameters may be determined from real data.  相似文献   

Leaching characteristics of a high-calcium fly ash as a function of pH: a potential source of selenium toxicity     

David A. Grisafe  Ernest E. Angino  Stephen M. Smith 《Applied Geochemistry》1988,3(6)

Using a modified extraction procedure, the effect of pH on the leaching of selected elements from Ca-rich (Type C) power plant fly ash was studied. Continuous additions of acetic acid were used to maintain pH values of fly ash slurries at 4.0, 6.0 and 8.0 for 24 h and an additional set was leached at its natural pH (average 11.8) value. Analyses for Se, As, Ca, Cd, Cr, Fe, Na and Pb showed that the highest concentrations occur in the leachate at pH 4.0 and decline with increasing pH. Concentrations of Cr and Fe increased slightly between neutral and high pH. Arsenic, Cd, Cr, Pb and Se concentrations exceeded the Environmental Protection Agency's toxicity criteria at pH 4.0. Selenium was above its toxicity level at pH values near 7 but the other elements were below their respective toxicity levels near neutral pH. Because recent studies show adverse effects of Se on aquatic life at far lower concentrations than the current Environmental Protection Agency's standard, high-Ca, power plant fly ashes represent a potentially hazardous pollutant to surface and subsurface waters.  相似文献