Sulfur and iron speciation in surface sediments along the northwestern margin of the Black Sea

The speciation of sedimentary sulfur (pyrite, acid volatile sulfides (AVS), S⁰, H₂S, and sulfate) was analyzed in surface sediments recovered at different water depths from the northwestern margin of the Black Sea. Additionally, dissolved and dithionite-extractable iron were quantified, and the sulfur isotope ratios in pyrite were measured. Sulfur and iron cycling in surface sediments of the northwestern part of the Black Sea is largely influenced by (1) organic matter supply to the sediment, (2) availability of reactive iron compounds and (3) oxygen concentrations in the bottom waters. Biologically active, accumulating sediments just in front of the river deltas were characterized by high AVS contents and a fast depletion of sulfate concentration with depth, most likely due to high sulfate reduction rates (SRR). The δ³⁴S values of pyrite in these sediments were relatively heavy (−8‰ to −21‰ vs. V-CDT). On the central shelf, where benthic mineralization rates are lower, re-oxidation processes may become more important and result in pyrite extremely depleted in δ³⁴S (−39‰ to −46‰ vs. V-CDT). A high variability in δ³⁴S values of pyrite in sediments from the shelf-edge (−6‰ to −46‰ vs. V-CDT) reflects characteristic fluctuations in the oxygen concentrations of bottom waters or varying sediment accumulation rates. During periods of oxic conditions or low sediment accumulation rates, re-oxidation processes became important resulting in low AVS concentrations and light δ³⁴S values. Anoxic conditions in the bottom waters overlying shelf-edge sediments or periods of high accumulation rates are reflected in enhanced AVS contents and heavier sulfur isotope values. The sulfur and iron contents and the light and uniform pyrite isotopic composition (−37‰ to −39‰ vs. V-CDT) of sediments in the permanently anoxic deep sea (1494 m water depth) reflect the formation of pyrite in the upper part of the sulfidic water column and the anoxic surface sediment. The present study demonstrates that pyrite, which is extremely depleted in ³⁴S, can be found in the Black Sea surface sediments that are positioned both above and below the chemocline, despite differences in biogeochemical and microbial controlling factors.     

Numerical modelling of regional faults in land subsidence prediction above gas/oil reservoirs

The stress variation induced by gas/oil production may activate pre‐existing regional faults. This may enhance the expected land subsidence due to the generation of mechanically weak points close to the producing field. A class of elasto‐plastic interface elements (IE), specifically designed to address the mechanical behaviour of faults over a regional scale, is integrated into a finite element (FE) geomechanical model and used to investigate the role exerted by active faults in anthropogenic land subsidence. The importance of regional faults depends on a variety of factors including depth of the depleted reservoir, fault number, orientation and size, geomechanical properties of porous medium, pore pressure drawdown induced by fluid production, etc. With the aid of some representative examples, a useful indication is provided as to where and how fault activation may influence both magnitude and extent of the land subsidence bowl above producing gas/oil reservoirs, pointing to a generally limited impact on the ground surface. The simulation of a real faulted gas reservoir in a complex 3‐D setting shows that the proposed IE can be simply and efficiently incorporated into a FE geomechanical model, thus improving the quality of the stress and displacement prediction. Copyright © 2007 John Wiley & Sons, Ltd.     

Large-Eddy Simulations of Pollutant Removal Enhancement from Urban Canyons

Boundary-Layer Meteorology - Techniques for improving the removal of pollution from urban canyons are crucial for air quality control in cities. The removal mainly occurs at the building roof...     

Building damage assessment after the <Emphasis Type="Italic">Riviera del Brenta</Emphasis> tornado,northeast Italy

A tornado with severe intensity hit the municipalities of Pianiga, Dolo and Mira close to Venice, northeast Italy, causing damages on a wide number of residential and industrial buildings and destroying some historical villas. In this study, the authors show the results of the damage assessment survey performed in the first days after the occurrence of the extreme event. Limited literature deals with damage assessment of European building types due to wind actions, and the available one does not consider building vulnerability as key factor in the structural response of existing structures subject to tornado hazard. In this paper, structural damages surveyed in reinforced concrete frame structures and masonry buildings, representative of common Italian building types, are critically discussed. Additionally, this work provides a database of past tornado events in northeast Italy, evidencing how the analyzed area has been found to be quite prone to tornado hazard.     

Carte geografiche secondo il modello della membrana elastica

Riassunto Quando una membrana elastica ed isotropa che riveste parzialmente una sfera viene distesa su un piano, la rete dei meridiani e paralleli stampata sulla membrana stessa si deforma secondo il principio della minima energia. L'Autore illustra con alcuni esempi la possibilità di ottenere buone proiezioni cartografiche fruendo del principio medesimo.

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Summary Whenever an elastic and isotropic diaphragm partially coating a sphere is spread on a plane, the net of the meridians and parallels loses the proper shape according to the principle of the lowest energy. The Author explains through some examples how to get cartographic projections by using the same principle.

     

Pliocene and Pleistocene magnetic stratigraphy in Le Castella area,Southern Italy—A preliminary report

A preliminary study was made of the magnetic stratigraphy of the Pliocene and Lower Pleistocene marine sediments in Le Castella area, Calabria, Southern Italy. Microbiostratigraphic evidence of the measured sediments provides a basis for tentative correlation with the standard magnetic chronology. The Gilsa Event in the Matuyama Reversed Polarity Epoch is estimated to be a little older than the lower limit of the Calabrian in Le Castella area.     

Nuovo metodo di registrazione dello stato del mare e primi risultati ottenuti a Genova

Riassunto Viene descritto ed illustrato un nuovo procedimento di registrazione del moto ondoso marino, il quale consiste sostanzialmente nel trasformare l'escursione verticale che subisce la superficie del mare nella compressione o dilatazione di una massa d'aria sovrastante racchiusa in un tubo verticale munito superiormente di opportuna membrana sensibile. Un tale apparecchio, installato a Prà (Genova) dal-l'Istituto Geofisico dell'Università di Genova, funziona con successo da alcuni mesi. Segue un esame dei primi risultati ivi conseguiti, dal quale appare l'importanza del passaggio dei fronti freddi sul moto ondoso del mare.

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Summary A new method for the recording of sea-wave motion is described and explained. It consists in having the vertical movement of the sea surface transformed into compression or expansion of a volume of air enclosed in a tube which is carrying on its upper part a sensitive membrane. This self-recording instrument, set up at Prà (Genoa) by the Istituto Geofisico dell'Università di Genova is functioning since several months already without giving rise to objections. Some first results obtained up now are also examided, from which it appears the importance of the passage of cold fronts.

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Zusammenfassung Es wird ein neues Verfahren für die Registrierung der Meereswellenbewegung beschrieben und erläutert. Es besteht darin, dass der vertikale Gang der Meeresoberfläche umgewandelt wird in Kompression oder Expansion einer in einem Rohre befindlichen Luftmasse, welche am oberen Teil von einer empfindlichen Membran geschlossen ist. Dieser Gerät, vom Istituto Geofisico dell'Università di Genova in Prà (Genua) aufgestellt, arbeitet bereits seit einigen Monaten einwandfrei. Einige vorläufige Ergebnisse werden dann erläutert, wofür auf die Bedeutung des Durchganges von Kaltfronten hingewiesen wird.

     

Middle-Late Jurassic syndepositional tectonics recorded in the Ligurian Briançonnais succession (Marguareis–Mongioie area,Ligurian Alps,NW Italy)

The Middle–Upper Jurassic succession of the Marguareis–Mongioie area (Ligurian Briançonnais Domain), developed in a protected shelf environment evolving into a pelagic plateau, bears clear evidence of synsedimentary tectonics such as: growth fault-related structures; neptunian dykes; marked lateral variations in stratigraphic thicknesses testifying to the juxtaposition of sectors characterized by different sedimentation and subsidence rates; discordant, anomalous stratigraphic contacts corresponding to paleoescarpments; nodular beds showing evidence of fluidification interpreted as seismites; and the occurrence of sand-sized quartz grains pointing to denudation of Permo-Triassic quartz-rich rocks. Such evidence documents an important Middle-Late Jurassic post-breakup tectonic activity, which was more effective in controlling the basin topography than the Early Jurassic syn-rift tectonic phase. Two main tectono-sedimentary stages, one occurring during the Bathonian, the other falling within the Callovian–Kimmeridgian interval, were reconstructed. The first stage can be referred to a fault-related activity occurring shortly after the initial stages of oceanic spreading of the Ligurian Tethys; the second can be genetically related to the far effects of the first rifting stage of the Bay of Biscay and the Valais basin.     

Measurement of field-saturated hydraulic conductivity on fractured rock outcrops near Altamura (Southern Italy) with an adjustable large ring infiltrometer

Up to now, field studies set up to measure field-saturated hydraulic conductivity to evaluate contamination risks, have employed small cylinders that may not be representative of the scale of measurements in heterogeneous media. In this study, a large adjustable ring infiltrometer was designed to be installed on-site directly on rock to measure its field-saturated hydraulic conductivity. The proposed device is inexpensive and simple to implement, yet also very versatile, due to its large adjustable diameter that can be fixed on-site. It thus allows an improved representation of the natural system’s heterogeneity, while also taking into consideration irregularities in the soil/rock surface. The new apparatus was tested on an outcrop of karstic fractured limestone overlying the deep Murge aquifer in the South of Italy, which has recently been affected by untreated sludge disposal, derived from municipal and industrial wastewater treatment plants. The quasi-steady vertical flow into the unsaturated fractures was investigated by measuring water levels during infiltrometer tests. Simultaneously, subsurface electrical resistivity measurements were used to visualize the infiltration of water in the subsoil, due to unsaturated water flow in the fractures. The proposed experimental apparatus works well on rock outcrops, and allows the repetition of infiltration tests at many locations in order to reduce model uncertainties in heterogeneous media.