Production of amorphous hydrated impure magnesium carbonate through ex situ carbonation

The evaluation of the feasibility of ex situ carbonation in landfills utilizing raw natural substances (namely serpentinites as Mg-source and the CO₂-rich fraction of biogas as C-source) was tested through a laboratory procedure comprising three steps. The first step is the acid attack of a serpentinite at 70 °C, by means of HCl 2 M, to get MgCl₂-rich solutions. Attacks of different durations were performed to evaluate the time needed. The second step is the neutralization of the MgCl₂-rich solution by addition of concentrated ammonia. The third (carbonation) step is mixing of the neutralized MgCl₂-rich solution with a solution of ammonium carbonate. This was produced in a landfill by absorption of CO₂ contained in biogas in a solution of ammonia. The neutralization of acid MgCl₂-rich solutions caused the precipitation of ferrihydrite with secondary ammonium carnallite and salammoniac, whereas abundant precipitation of Amorphous Hydrated Impure Magnesium Carbonate (AHIMC), sometimes with minor nesquehonite, occurred in the third step. This solid carbonate acts as a stable CO₂ sink up to 380 °C. The geochemical behavior of some minor elements was also investigated during the experimental processes revealing that Al, Cr and Ni were removed during neutralization (second step), in contrast to Ca which remained in the circumneutral MgCl₂-rich solution and entered into the structure of AHIMC. During the carbonation step, precipitation of artinite, hydromagnesite, lansfordite, magnesite and nesquehonite was thermodynamically impossible as the aqueous phase was undersaturated with respect to these solid phases upon separation of AHIMC.     

Some results of coastal defences monitoring by ground laser scanning technology

A general coastal retreat affects almost all the beaches of the Apulia region (southern Italy). In particular, the coastal strip of the Gulf of Manfredonia shows an evident retreat due to human activity. To control coastal erosion, several defence interventions have been realised: breakwaters, shore parallel defences, and, above all, several types of groynes (rectilinear, hook-shaped, T-shaped) were built along the shoreline in accordance with local request. Nowadays, there are about 300 coastal defences built up to protect against human activities. A laser scanner survey of these defences, using a Leica Geosystems HDS3000, was carried out between April 2006 and September 2008 to collect data about the beach profiles and changes occurring in the defence framework. The survey work consists of 3D rendering of defences in order to make comparisons between scans of different periods. Overlap between the points cloud of the whole coastline showed that defences preserved their own profile when no human interventions took place. Moreover, throughout the length of the investigated area, not a single trend occurred in the beach profile: according to the defence framework, some stretches of coast display advancing trend, while others are stable or retreating. Therefore, this preliminary study indicated that the changes that occurred in the beach profiles and defence structures are mainly due to human interventions.     

Laboratory Studies on Silicates Relevant for the Physics of TNOs

Silicates are one of the principal components present in Solar System objects.Silicates evolve in space modifying their physical properties according to theastronomical environments they go through. To characterise the nature of TNOsin the framework of the formation and evolution of the Solar System, experimentson structural transitions of silicates have been performed in the laboratoryto simulate some of the processing suffered by the dust. The infrared spectralproperties of possible silicate candidates thought to be present in TNOs have beenstudied. The results of thermal annealing of amorphous silicates and amorphisationof crystalline forsterite (pure-Mg olivine) by ion irradiation are presented. Theobservable properties of TNOs surfaces are inferred.     

Shock metamorphism and impact melting in small impact craters on Earth: Evidence from Kamil crater,Egypt

Kamil is a 45 m diameter impact crater identified in 2008 in southern Egypt. It was generated by the hypervelocity impact of the Gebel Kamil iron meteorite on a sedimentary target, namely layered sandstones with subhorizontal bedding. We have carried out a petrographic study of samples from the crater wall and ejecta deposits collected during our first geophysical campaign (February 2010) in order to investigate shock effects recorded in these rocks. Ejecta samples reveal a wide range of shock features common in quartz‐rich target rocks. They have been divided into two categories, as a function of their abundance at thin section scale: (1) pervasive shock features (the most abundant), including fracturing, planar deformation features, and impact melt lapilli and bombs, and (2) localized shock features (the least abundant) including high‐pressure phases and localized impact melting in the form of intergranular melt, melt veins, and melt films in shatter cones. In particular, Kamil crater is the smallest impact crater where shatter cones, coesite, stishovite, diamond, and melt veins have been reported. Based on experimental calibrations reported in the literature, pervasive shock features suggest that the maximum shock pressure was between 30 and 60 GPa. Using the planar impact approximation, we calculate a vertical component of the impact velocity of at least 3.5 km s^?1. The wide range of shock features and their freshness make Kamil a natural laboratory for studying impact cratering and shock deformation processes in small impact structures.     

The star formation history of redshift z~2 galaxies:the role of the infrared prior

We build a sample of 298 spectroscopically-confirmed galaxies at redshift z~2,selected in the z850-band from the GOODS-MUSIC catalog.By utilizing the rest frame 8μm luminosity as a proxy of the star formation rate(SFR),we check the accuracy of the standard SED-fitting technique,finding it is not accurate enough to provide reliable estimates of the physical parameters of galaxies.We then develop a new SED-fitting method that includes the IR luminosity as a prior and a generalized Calzetti law with a variable RV.Then we exploit the new method to re-analyze our galaxy sample,and to robustly determine SFRs,stellar masses and ages.We find that there is a general trend of increasing attenuation with the SFR.Moreover,we find that the SFRs range between a few to 103M yr 1,the masses from 109to 4×1011M,and the ages from a few tens of Myr to more than 1 Gyr.We discuss how individual age measurements of highly attenuated objects indicate that dust must have formed within a few tens of Myr and already been copious at≤100 Myr.In addition,we find that low luminosity galaxies harbor,on average,significantly older stellar populations and are also less massive than brighter ones;we discuss how these findings and the well known‘downsizing’scenario are consistent in a framework where less massive galaxies form first,but their star formation lasts longer.Finally,we find that the near-IR attenuation is not scarce for luminous objects,contrary to what is customarily assumed;we discuss how this affects the interpretation of the observed M/L ratios.     

Importance of oceanic resolution and mean state on the extra-tropical response to El Niño in a matrix of coupled models

The extra-tropical response to El Niño in configurations of a coupled model with increased horizontal resolution in the oceanic component is shown to be more realistic than in configurations with a low resolution oceanic component. This general conclusion is independent of the atmospheric resolution. Resolving small-scale processes in the ocean produces a more realistic oceanic mean state, with a reduced cold tongue bias, which in turn allows the atmospheric model component to be forced more realistically. A realistic atmospheric basic state is critical in order to represent Rossby wave propagation in response to El Niño, and hence the extra-tropical response to El Niño. Through the use of high and low resolution configurations of the forced atmospheric-only model component we show that, in isolation, atmospheric resolution does not significantly affect the simulation of the extra-tropical response to El Niño. It is demonstrated, through perturbations to the SST forcing of the atmospheric model component, that biases in the climatological SST field typical of coupled model configurations with low oceanic resolution can account for the erroneous atmospheric basic state seen in these coupled model configurations. These results highlight the importance of resolving small-scale oceanic processes in producing a realistic large-scale mean climate in coupled models, and suggest that it might may be possible to “squeeze out” valuable extra performance from coupled models through increases to oceanic resolution alone.     

Vestoid cosmic spherules from the South Pole Water Well and Transantarctic Mountains (Antarctica): A major and trace element study

We present major and trace element data of five glass cosmic spherules (CS) with differentiated compositions recovered in the South Pole Water Well and the Transantarctic Mountains, Antarctica. The differentiated CS were first identified using Fe/Mg and Fe/Mn ratios and we have now added high Rare Earth Element concentrations (5 < REE_N < 14), and low siderophile element abundances (e.g. Ni = 25 ± 27 ppm) as characteristics. We propose that the siderophile depletions observed in differentiated CS result from the segregation of these elements into the core of their parent body during differentiation. Then, the high Fe/Mg ratios of differentiated CS result from their low MgO contents. Combined with their high level of REE enrichment, this indicates that the precursors formed through basaltic melt extraction from the asteroid/planetary source. As Fe/Mn and Fe/Mg ratios cannot distinguish between a Martian or Vestoid origin, we measured trace elements (zinc, cobalt, and vanadium) whose chemical behavior depends on oxidation state, known to be higher in the Martian than in the Vestoid environment. The compositions of the differentiated CS studied in this work share the characteristics of eucrites for all these indicators, providing further evidence that these differentiated CS are samples of a Vesta-like asteroid. However, their precursors show a considerable diversity in their mineralogy when compared to eucrites, that results in a wider range of major (Ca and Al) and trace element (Ba, Sr, Sc, and V) composition in differentiated CS.     

A Hercynian suture zone in Sardinia : geological and geochemical evidence

Abstract

The Hereynian basement of Northern Sardinia consists of two main teetonometamorphic complexes : the Southern Paleozoic Low to Medium Grade Metamorphic Complex (LMGMC) and the Northern (Precaimbrian ?) High Grade Metamorphic Complex (HGMC). These complexes are separateli bu the “Posada-Asinara Line” which is a several kilometer-wide mylonitie belt consisting of micaschist. parag-neiss and quartzite that cuts across all Northern Sardinia and contains scattered hodies of amphibolites with granulile and eclogite facies relies.

Major element composition of ampbibolites indicates they were derived from metamorphosed basalts of tholciitie affinity. REE and the relative abundances of HKS elements strongly suggest an oceanic basaltie prololith (N- and T-typc MORB). A whole-rock Sm-Nd isochron for the amphibolite protoliths yields an age of ea. 960 Ma.

The Northern Sardinia basement can he interpreted as a continental collisional zone with the “Posada-Asinara Line” representing a suture zone squeezed between a crustal nappe (HGMC), which represents the overthrust continental margin. and (he inner portion of the Varisean orogenie wedge, which represents the underthrust continental margin with its Paleozoic cover (LMGMC).

Geological and geochemical evidence indicate that the “Posada-Asinara Line” may he considered as part of the South European Hereynian Suture Zone.