Toward the probabilistic forecasting of cyclone-induced marine flooding by overtopping at Reunion Island aided by a time-varying random-forest classification approach

Natural Hazards - In 2017, Irma and Maria highlighted the vulnerability of small islands to cyclonic events and the necessity of advancing the forecast techniques for cyclone-induced marine...     

Nitrogen and Phosphorus Recovery from Human Urine by Struvite Precipitation and Air Stripping in Vietnam

A “No Mix” sanitation system was installed in a dormitory at the University of CanTho in South Vietnam, with the objective of recycling nutrients from source separated wastewater streams. This paper presents the “Yellow Water” treatment plant and its efficiency in recovering phosphorus and nitrogen from human urine. The pilot plant achieved phosphorus removal efficiencies of 98% with both diluted and undiluted urine. Phosphorus was recovered in the form of struvite, a solid mineral fertilizer with heavy metal concentrations being below the German Fertilizer Regulation's threshold limits. About 110 g of struvite could be generated after one treatment cycle, during which 50 L of urine were processed. Nitrogen removal by air stripping showed best results when circulating the urine for 3 h through the stripping column at a high flow rate (80 L/h). With these settings, more than 90% of the nitrogen could be removed from the urine, and virtually 100% of this nitrogen could be recovered in the form of liquid ammonium sulfate. In the future, treatment costs could be further reduced by making use of the solar energy that is available during daytime in South Vietnam.     

X-ray absorption study of Ti-bearing silicate glasses

Ti K-edge XANES spectra have been collected on a series of Ti-bearing silicate glasses with metasilicate and tetrasilicate compositions. The intensity of the preedge feature in these spectra has been found to change with glass composition and varies from 29 to 58% (normalized intensity) suggesting a variation in structural environent around the absorbing atom. The pre-edge peak intensity increases for the alkali titanium tetrasilicate glasses from 35% to 58% in the order Li < Na < K < Rb, Cs whereas for the metasilicate compositions there is a maximum for the K-bearing glass. The pre-edge peak intensity remains constant for the alkaline earth titanium metasilicate glasses, Ca and Sr (34%) but increases slightly for Ba (41%). As the intensity of this feature is inversely correlated with coordination number, a comparison of the pre-edge intensity data for the investigated glasses with those of materials of known coordination number leads us to establish a regression equation and to infer that the average coordination number of Ti in these glasses ranges from 4.8 to 5.8. Large alkali cations appear to stabilize a relatively low average coordination number for Ti in silicate melts. The Ti structural environment results appear also to vary as a function of SiO₂ content within the K₂O-TiO₂-SiO₂ system. A number of physical properties of the melts from which these glasses were quenched and of other Ti-bearing silicate melts, have been determined in recent years. Clear evidence of a variable coordination number of Ti, consistent with the interpretation of the present XANES data is available from density measurements. These and other property determinations are compared with the present spectroscopic observations in an attempt to relate structure and properties in these melts which contain a major component with variable coordination number.     

Numerical simulation and validation of ocean waves measured by an Along-Track Interferometric Synthetic Aperture Radar

A new nonlinear integral transform of ocean wave spectra into Along-Track Interferometric Synthetic Aperture Radar （ATI-SAR） image spectra is described. ATI-SAR phase image spectra are calculated for various sea states and radar configurations based on the nonlinear integral transform. The numerical simulations show that the slant range to velocity ratio （R/V）, significant wave height to ocean wavelength ratio （Hi2）, the baseline （2B） and incident angle （0） affect ATI-SAR imaging. The ATI-SAR imaging theory is validated by means of Two X-band, HH-polarized ATI-SAR phase images of ocean waves and eight C-band, HH-polarized ATI-SAR phase image spectra of ocean waves. It is shown that ATI-SAR phase image spectra are in agreement with those calculated by forward mapping in situ directional wave spectra collected simultaneously with available ATI-SAR observations. ATI-SAR spectral correlation coefficients between observed and simulated are greater than 0.6 and are not sensitive to the degree of nonlinearity. However, the ATI-SARoPhase image spectral turns towards the range direction, even if the real ocean wave direction is 30. It is also shown that the ATI-SAR imaging mechanism is significantly affected by the degree of velocity bunching nonlinearity, especially for high values of R/V and H/2.     

Pre‐Holocene age of Humboldt's 1430 eruption of the Orotava Valley,Tenerife, Canary Islands

Errors in the interpretation of clouds, fumarolic activity and forest fires as volcanic eruptions in Tenerife, mainly in relation with Teide volcano, are common in references by passing navigators and other eyewitness accounts from the fifteenth and sixteenth centuries. In the case of the most common, historical, multiple‐vent fissure eruptions in the Canaries, vent locations provided by these accounts are frequently uncertain or are clearly erroneous and often conflict with geological evidence. Significant examples are the general association of the latest eruption of Teide volcano, dated at 1150 ± 140 bp , with the reference made by Christopher Columbus in 1492 to an eruption ‘on the flanks of Teide’, which actually corresponds to an eruptive vent (Boca Cangrejo volcano) situated in the NW Rift, dated at 400 ± 110 bp . Similar conflicting vent locations occurred in the 1730–36 eruption of Lanzarote and the 1677 eruption of La Palma. This article considers the volcanic cones located in the Orotava Valley, erroneously assigned by Chevalier de Borda and Alexander von Humboldt to a 1430 ad eruption. Geological evidence and radiocarbon dating of charcoal underlying the lapilli, and ⁴⁰Ar/³⁹Ar dating of one of the lava flows, show that these volcanic cones and lavas correspond to an eruption that took place about 30 000 yr bp . Analysis of the influence of these erroneous ages for the recent volcanism of Tenerife shows an overestimation of eruptive hazards of this island.     

Iron environment in a montmorillonite from Gola del Furlo (Marche,Italy). A synchrotron radiation XANES and a Mössbauer study

Summary The iron environment and oxidation state has been determined by XANES spectroscopy in a montmorillonite sample from Gola del Furlo (Marche, Italy). A comparison with the XANES spectra of Fe^2– in a natural hematite from Elba (Italy) and of Fe 21 in a synthetic Fe[C0₃] (the fine structures in the spectra of which have also been clarified in detail on the basis of the known crystal structures) permits recognizing that in this sheet silicate Fe is mostly in the trivalent oxidation state and in a distorted octahedral coordination. Mössbauer spectroscopy confirms the XANES assignment, but it also shows that minor octahedral Fee+ is present besides the predominant octahedral Fe^3—.

---

Zusammenfassung Synchroton Radiation XANES und Mössbauer-Studien zur Vertielung des Eisens im Montmorillonit aus Gola del Furlo(Marche, Italien) Die Verteilung und die Oxidationsstufe des Eisens eines Montmorillonites aus Gola del Furlo (Marche, Italien) wurden untersucht. Ein Vergleich der XANES Spektren dieses Schichtsilikates mit denen von FeFe³⁺ eines natürlichen Hämatites von Elba (Italien) und von Fe²⁺ eines synthetischen Fe[C0₃], wobei die Details der Spektren auf Grund der Kenntnis der bekannten Kristallstruktur geklärt werden konnten, zeigt, daß Eisen großteils in dreiwertiger Form und in verzerrter oktaedrischer Koordination vorliegt. Mössbauer-Studien bestätigen die Ergebnisse der XANES Untersuchungen, zeigen aber auch, daß untergeordnet Fe e+ an Stelle von Fe³⁺ in der oktaedrischen Position eingebaut wird.

     

Late Ordovician glaciation in southern Turkey

ABSTRACT We present a new survey of several Palaeozoic sections in both the Taurus range and the Border Folds that documents typical glacial features including a glacial pavement and striated dropstones (Halevikdere Formation) and demonstrates the former presence of an ice sheet in southern and south-eastern Turkey. Evidence for the late Ashgill (Hirnantian) age of this episode is provided by macro- and microfossils found within the glacial formation. The extension of ice-related deposits into the northernmost part of the Arabian Platform (Mardin region) implies a much wider distribution of the Ordovician ice sheet than was previously believed, and strongly suggests that southern Turkey lay close to Egypt during the Lower Palaeozoic.     

Diagenetic controls on the isotopic composition of carbonate‐associated sulphate in the Permian Capitan Reef Complex,West Texas

Late Palaeozoic‐age strata from the Capitan Reef in west Texas show facies‐dependent heterogeneity in the sulphur isotopic composition of carbonate‐associated sulphate, which is trace sulphate incorporated into carbonate minerals that is often used to reconstruct the sulphur isotopic composition of ancient seawater. However, diagenetic pore fluid processes may influence the sulphur isotopic composition of carbonate‐associated sulphate. These processes variously modify the sulphur isotopic composition of incorporated sulphate from syndepositional seawater in shelf crest, outer shelf, shelf margin and slope depositional settings. This study used a new multicollector inductively‐coupled plasma mass spectrometry technique to determine the sulphur isotopic composition of samples of individual depositional and diagenetic textures. Carbonate rocks representing peritidal facies in the Yates and Tansill formations preserve the sulphur isotopic composition of Guadalupian seawater sulphate despite alteration of the carbon and oxygen isotopic compositions by meteoric and dolomitizing diagenetic processes. However, sulphur isotopic data indicate that limestones deposited in reef and slope facies in the Capitan and Bell Canyon formations largely incorporate sulphate from anoxic marine‐phreatic pore fluids isotopically modified from seawater by microbial sulphate reduction, despite generally preserving the carbon and oxygen isotopic compositions of Permian seawater. Some early and all late meteoric calcite cements have carbonate‐associated sulphate with a sulphur isotopic composition distinct from that of Permian seawater. Detailed petrographic and sedimentary context for carbonate‐associated sulphate analyses will allow for improved reconstructions of ancient seawater composition and diagenetic conditions in ancient carbonate platforms. The results of this study indicate that carbonate rocks that diagenetically stabilize in high‐energy environments without pore fluid sulphate gradients can provide a robust archive of ancient seawater's sulphur isotopic composition.     

X‐ray tomography of tsunami deposits: Towards a new depositional model of tsunami deposits

X‐ray computed microtomography is used to obtain high resolution imagery of a historical tsunami deposit in Andalusia, Spain (1755 Lisbon tsunami). The technique allows characterization of grain‐size distribution, structures, component analysis and sedimentary fabric of fine‐grained unconsolidated tsunami deposits at resolutions down to particle scale. The results are validated by comparing to data obtained using other techniques such as laser diffraction, anisotropy of magnetic susceptibility and X‐ray microfluorescence on the same deposits. Specific technical details such as sampling, scanning and image processing methods, and further improvements are addressed. The use of X‐ray computed microtomography provides new insights into the stratigraphy of the deposits and gives access to significantly more detailed view of key sedimentary features such as mudlines, rip‐up clasts, crude laminations, convolutions, floating outsized clasts and contacts between successive units. This analysis of the 1755 tsunami deposits using X‐ray computed microtomography allows the proposal of new hypotheses for the sedimentary processes forming tsunami deposits. Deposition by settling is limited and the section analysed here is dominated by a high shear stress leading to the development of traction carpets, with laminated mudlines corresponding to the basal frictional region of these carpets. The onset of the tsunami backwash is marked by a micro‐vortex resembling Kelvin–Helmoltz instabilities.