IL DRAGAGGIO NEL DIVENIRE. LE MIGLIORI TECNICHE DISPONIBILI PER IL DRAGAGGIO IN SIN - SIR.

Il presente lavoro intende delineare un quadro generale delle problematiche legate alla progettazione ed esecuzione degli interventi di bonifica in ambito marino, alla luce delle vigenti disposizioni normative in ambito nazionale. Purtroppo l’attività di dragaggio attualmente è affetta da dubbi ed incertezze interpretative, disorganicità dell’attuale sistema normativo in materia ambientale, che non sono state superate neanche dopo l’emanazione del nuovo Testo Unico per l’Ambiente. Il problema ambientale, aggravatosi a causa della crescente evoluzione industriale, è ad oggi una complicata e pesante eredità da affrontare, in cui decenni di incuria e mancata vigilanza hanno consegnato alle nuove generazioni siti industriali dismessi, vecchi siti di centrali nucleari inattive, discariche abusive e rifiuti pericolosi mal gestiti, con conseguente alterazione delle caratteristiche qualitative dei terreni, delle acque superficiali e sotterranee. I siti inquinati possono essere un enorme risorsa se solo si riuscisse a promuovere la loro bonifica, assicurando la continuità delle attività produttive oppure per farne occasione di rilancio e riutilizzo del territorio. Affinché ciò possa accadere è necessario un grande sforzo pubblico e privato ed un cambiamento nell’approccio in tale disciplina. In particolare tale elaborato, vuole cercare di porre attenzione sull’azione di risanamento dei siti contaminati, che non deve limitarsi ad utilizzare esclusivamente tecnologie invadenti rapide ed onerose, ma deve perseguire come obiettivo principale l’impiego e la sperimentazione di nuove tecnologie che rispettino il naturale equilibrio dell’ambiente e la salute dell’uomo, e che conducano comunque a risultati efficienti e sostenibili. Tutto ciò dovrà passare attraverso un miglioramento dell’efficienza e della qualità dei processi produttivi, mediante il ricorso a nuove tecnologie, nuovi materiali e nuovi sistemi operativi, compatibili con la sicurezza e la salvaguardia dell’ambiente. L'Unione Europea ha emanato la Direttiva 96/61 CE con lo scopo di ottenere una prevenzione ed un controllo integrati dell'inquinamento proveniente dai diversi settori produttivi, attraverso interventi alla fonte delle attività inquinanti, con l'obiettivo di conseguire un elevato livello di protezione dell'ambiente nel suo complesso, attraverso l’utilizzo delle Migliori Tecnologie Disponibili (BAT, Best Available Techniques). Durante lo svolgimento della tesi verrà posto un confronto, su cui avanzeremo delle riflessioni, con l’attuale politica sui rifiuti. Nello specifico analizzeremo quanto affrontato dalla Commissione per le Migliori Tecnologie di gestione e smaltimento dei rifiuti, consapevole che le giuste modalità di intervento sono con tecnologie appropriate e con opportune iniziative di tipo gestionale in ogni sua fase. L’approccio con cui si attua una corretta politica di smaltimento dei rifiuti è basato sull’adozione di un preciso ordine gerarchico,che tenga conto dell’intera filiera partendo dalla loro produzione industriale, passando attraverso la raccolta, il recupero o riciclaggio, e terminando con lo smaltimento. A partire da ciò, cercheremo di comprendere perché quanto dettato dalla Direttiva Europea non venga recepito dalla normativa nazionale in campo di bonifica dei siti contaminati, analizzando in particolar modo casi pratici di bonifica di SIN presenti sul territorio italiano. Concluderemo l’elaborato con la presentazione di una valida alternativa, già esistente in campo industriale, che rappresenta come sia possibile operare con tecnologie e metodologie innovative tali da rispondere ai principi normativi da un lato e, dall’altro, conferire pregi operativi ed economici per i dragaggi in ambito portuale e per bonifiche in ambito SIN

Rocky planet or water world? Observability of low-density lava world atmospheres

Super-Earths span a wide range of bulk densities, indicating a diversity in interior conditions beyond that seen in the solar system. In particular, an emerging population of low-density super-Earths may be explained by volatile-rich interiors. Among these, low-density lava worlds have dayside temperatures high enough to evaporate their surfaces, providing a unique opportunity to probe their interior compositions and test for the presence of volatiles. In this work, we investigate the atmospheric observability of low-density lava worlds. We use a radiative-convective model to explore the atmospheric structures and emission spectra of these planets, focusing on three case studies with high observability metrics and sub-stellar temperatures spanning $\sim$1900-2800 K: HD 86226c, HD 3167b and 55 Cnce. Given the possibility of mixed volatile and silicate interior compositions for these planets, we consider a range of mixed volatile and rock vapor atmospheric compositions. This includes a range of volatile fractions and three volatile compositions: water-rich (100% H$_2$O), water with CO$_2$ (80% H$_2$O+20% CO$_2$), and a desiccated O-rich scenario (67% O$_2$+33%CO$_2$). We find that spectral features due to H$_2$O, CO$_2$, SiO and SiO$_2$ are present in the infrared emission spectra as either emission or absorption features, depending on dayside temperature, volatile fraction and volatile composition. We further simulate JWST secondary eclipse observations for each of the three case studies, finding that H$_2$O and/or CO$_2$ could be detected with as few as $\sim$5 eclipses. Detecting volatiles in these atmospheres would provide crucial independent evidence that volatile-rich interiors exist among the super-Earth population.Comment: Accepted for publication in ApJ. 26 pages, 12 figures, 2 table

Spectroradiometry with sub-microsecond time resolution using multianode photomultiplier tube assemblies

Accurate and precise measurements of spectroradiometric temperature are crucial for many high pressure experiments that use diamond anvil cells or shock waves. In experiments with sub-millisecond timescales, specialized detectors such as streak cameras or photomultiplier tubes are required to measure temperature. High accuracy and precision are difficult to attain, especially at temperatures below 3000 K. Here we present a new spectroradiometry system based on multianode photomultiplier tube technology and passive readout circuitry that yields a 0.24 $\mu$s rise-time for each channel. Temperature is measured using five color spectroradiometry. During high pressure pulsed Joule heating experiments in a diamond anvil cell, we document measurement precision to be $\pm 30$ K at temperatures as low as 2000 K during single-shot heating experiments with $0.6$ $\mu$s time-resolution. Ambient pressure melting tests using pulsed Joule heating indicate that the accuracy is $\pm 80$ K in the temperature range 1800-2700 K.Comment: 17 pages, 18 figure

A diamond anvil microassembly for Joule heating and electrical measurements up to 150 GPa and 4000 K

When diamond anvil cell (DAC) sample chambers are outfitted with both thermal insulation and electrodes, two cutting-edge experimental methods are enabled: Joule heating with spectroradiometric temperature measurement, and electrical resistance measurements of samples heated to thousands of kelvin. The accuracy of temperature and resistance measurements, however, often suffers from poor control of the shape and location of the sample, electrodes, and thermal insulation. Here, we present a recipe for the reproducible and precise fabrication of DAC sample, electrodes, and thermal insulation using a three-layer microassembly. The microassembly contains two potassium chloride thermal insulation layers, four electrical leads, a sample, and a buttressing layer made of polycrystalline alumina. The sample, innermost electrodes, and buttress layer are fabricated by focused-ion-beam milling. Three iron samples are presented as proof of concept. Each is successfully compressed and pulsed Joule heated while maintaining a four-point probe configuration. The highest pressure-temperature condition achieved is $\sim 150$ GPa and $\sim 4000$ K.Comment: 19 pages, 15 figures, 2 table

Corrigendum: Experimental dissolution of carbonaceous materials in water at 1 GPa and 550°C: assessing the role of carbon forms and redox state on COH fluid production and composition during forearc subduction of organic matter

Biogenic carbonaceous material (CM) is the main carrier of organic carbon in the subduction zone and contributes to COH fluid production and volcanic arc gaseous emissions. Here we investigated the effect of the structural, textural and chemical heterogeneity of CM on its reactivity and redox dissolution by conducting short-lived (1 h) experiments, where synthetic analogues of CM (ordered graphite, graphite oxide (GO), mesoporous carbon (MC), Vulcan® carbon (VC) and glass-like carbon (GC)), are reacted with water at P = 1 GPa and T = 550°C—conditions typical of a warm forearc subduction—and fO2 buffered from ΔFMQ ≈ +4 to −7. We show that the amount of dissolved CM (CMdissolved) and the proportion of volatile carbon species (Cvolatile) in the fluid is related both to the structure and the peculiar surficial properties of the carbon forms, such as carbon sp2-and sp3-hybridization, amount of oxygen heteroatoms, presence of oxygenated functional groups (OFGs) and of active sites. MC and graphite (C(sp2) > 93 at%, O dissolved 2 + CO and CO2 + CH4 Cvolatile mixtures at ΔFMQ ≈ +4 and −7, respectively), while the latter has a maximum of Cvolatile production (CO2 + CH4) at ΔFMQ ≈0, which is not observed in a 10-day long run; partly-ordered GO (C(sp3) > 98 at%, O ∼31 at%, OFGs ∼41 at%) is the most reactive material at all redox conditions (CMdissolved > 2.6 mol%) and produces CO2 as the dominant Cvolatile species; disordered GC and VC (C(sp3) dissolved ∼1 mol%) and ΔFMQ ≈ –7 (CMdissolved > 1 mol%), where Cvolatile is dominantly CO2 and CH4, respectively. Besides the significant deviations from thermodynamically predicted graphite-saturated COH fluid composition and speciation, our results suggests that: 1) immature CM (disordered, rich in C(sp3), O, OFGs) is preferentially dissolved under high fluid fluxes and may buffer fluids to rather oxidizing conditions; 2) a descending flux of oxygen (and hydrogen) bond to CM may exist.</p

Phase transition kinetics revealed by <i>in situ</i> x-ray diffraction in laser-heated dynamic diamond anvil cells

We report successful coupling of dynamic loading in a diamond anvil cell and stable laser heating, which enables compression rates up to 500 GPa/s along high-temperature isotherms. Dynamic loading in a diamond-anvil cell allows exploration of a wider range of pathways in the pressure-temperature space compared to conventional dynamic compression techniques. By in situ x-ray diffraction, we are able to characterize and monitor the structural transitions with the appropriate time resolution i.e., millisecond timescales. Using this method, we investigate the γ−ε phase transition of iron under dynamic compression, reaching compression rates of hundreds of GPa/s and temperatures of 2000 K. Our results demonstrate a distinct response of the γ−ε and α− ε transitions to the high compression rates achieved, possibly due to the different transition mechanisms. These findings open up new avenues to study tailored dynamic compression pathways in the pressure-temperature space and highlight the potential of this platform to capture kinetic effects (over ms time scales) in a diamond anvil cell

Phase transition kinetics revealed in laser-heated dynamic diamond anvil cells

We report on a novel approach to dynamic compression of materials that bridges the gap between previous static- and dynamic- compression techniques, allowing to explore a wide range of pathways in the pressure-temperature space. By combining a dynamic-diamond anvil cell setup with double-sided laser-heating and in situ X-ray diffraction, we are able to perform dynamic compression at high temperature and characterize structural transitions with unprecedented time resolution. Using this method, we investigate the $\gamma-\epsilon$ phase transition of iron under dynamic compression for the first time, reaching compression rates of hundreds of GPa/s and temperatures of 2000 K. Our results demonstrate a distinct response of the $\gamma-\epsilon$ and $\alpha-\epsilon$ transitions to the high compression rates achieved. These findings open up new avenues to study tailored dynamic compression pathways in the pressure-temperature space and highlight the potential of this platform to capture kinetic effects in a diamond anvil cell.Comment: Reworked the text and figures to be more in line with the format of PR

Étude expérimentale du système Fe-Si-C et application aux exoplanètes riches en carbone

Plus de 4000 exoplanètes ont été découvertes, orbitant autour d’étoiles ayant différentes compositions. Ces exoplanètes sont détectées et étudiées par observations indirectes qui, dans de nombreux cas, donnent accès aux propriétés principales des planètes: leurs masses et leurs rayons. Ces paramètres peuvent être calculés à partir d’un modèle et comparés à ceux observés. Toutefois, cela est plus difficile pour des planètes qui orbitent autour d’étoiles ayant une composition chimique différente du Soleil, par exemple enrichie en carbone, car les propriétés physiques des carbures (i.e. carbures de silicium ou de fer) sont inconnues. Dans cette étude les systèmes Si-C et Fe-Si-C ont été étudiés entre 20 et 200 GPa et 300-3000 K, en utilisant la diffraction de rayons x et l’analyse chimique des échantillons récupérés pour déterminer les propriétés physiques dans des conditions extrêmes. Dans le système Si-C les équations d’états et les modèles thermiques pour les deux phases de basse et haute pression ont été déterminés. Les résultats ont ensuite été utilisé pour calculer la relation masse-rayon de planètes synthétiques ayant un noyau de fer et un manteau de SiC. Concernant le système Fe-Si-C le diagramme de phase ternaire a été reconstruit. En faisant l’hypothèse d’une composition Fe-Si-C pour un noyau planétaire, quatre différentes séquences de cristallisation ont été démontrées, déterminant des comportements dynamiques très diffèrent. En conclusion la relation masse-rayon n’est pas suffisante pour déterminer la composition et la structure interne des exoplanètes observées mais des données relatives à la chimie du système planétaire sont requises.More than 4000 exoplanets have been discovered, orbiting around stars with a wide variety of composition. Such planets are detected and studied through indirect methods that in many cases give access to the main properties of the planets: mass and radius. The same parameters can be calculated from a chosen model and compared to the observed ones. However it is difficult for planets orbiting around stars with compositions very different from our Sun, for example carbon enriched, as the physical properties carbides (i.e. silicon carbides and iron carbides) at extreme pressure are unknown. In this work the Si-C and Fe-Si-C systems were studied in the range between 20 and 200 GPa and 300-3000 K employing X-ray diffraction and chemical analyses on the recovered samples were used to determine the physical properties at extreme conditions. In the Si-C system the equations of state and thermal model for both the low pressure and high pressure phases were determined. The results were then used to model a mass radius plot for different archetypal planets with a Fe core and SiC mantle. Regarding the Fe-Si-C system a ternary phase diagram was reconstructed up to 200 GPa and 3000 K. Assuming Fe-Si-C as main component of planetary cores, four different crystallization paths are individuated, giving rise to way different dynamical behaviour. We conclude that using only mass radius relations is not sufficient to determine the interior composition and structure of an observed exoplanet and further data relative to the chemistry are needed, for example the composition of the host star

Étude expérimentale du système Fe-Si-C et application aux exoplanètes riches en carbone

More than 4000 exoplanets have been discovered, orbiting around stars with a wide variety of composition. Such planets are detected and studied through indirect methods that in many cases give access to the main properties of the planets: mass and radius. The same parameters can be calculated from a chosen model and compared to the observed ones. However it is difficult for planets orbiting around stars with compositions very different from our Sun, for example carbon enriched, as the physical properties carbides (i.e. silicon carbides and iron carbides) at extreme pressure are unknown. In this work the Si-C and Fe-Si-C systems were studied in the range between 20 and 200 GPa and 300-3000 K employing X-ray diffraction and chemical analyses on the recovered samples were used to determine the physical properties at extreme conditions. In the Si-C system the equations of state and thermal model for both the low pressure and high pressure phases were determined. The results were then used to model a mass radius plot for different archetypal planets with a Fe core and SiC mantle. Regarding the Fe-Si-C system a ternary phase diagram was reconstructed up to 200 GPa and 3000 K. Assuming Fe-Si-C as main component of planetary cores, four different crystallization paths are individuated, giving rise to way different dynamical behaviour. We conclude that using only mass radius relations is not sufficient to determine the interior composition and structure of an observed exoplanet and further data relative to the chemistry are needed, for example the composition of the host star.Plus de 4000 exoplanètes ont été découvertes, orbitant autour d’étoiles ayant différentes compositions. Ces exoplanètes sont détectées et étudiées par observations indirectes qui, dans de nombreux cas, donnent accès aux propriétés principales des planètes: leurs masses et leurs rayons. Ces paramètres peuvent être calculés à partir d’un modèle et comparés à ceux observés. Toutefois, cela est plus difficile pour des planètes qui orbitent autour d’étoiles ayant une composition chimique différente du Soleil, par exemple enrichie en carbone, car les propriétés physiques des carbures (i.e. carbures de silicium ou de fer) sont inconnues. Dans cette étude les systèmes Si-C et Fe-Si-C ont été étudiés entre 20 et 200 GPa et 300-3000 K, en utilisant la diffraction de rayons x et l’analyse chimique des échantillons récupérés pour déterminer les propriétés physiques dans des conditions extrêmes. Dans le système Si-C les équations d’états et les modèles thermiques pour les deux phases de basse et haute pression ont été déterminés. Les résultats ont ensuite été utilisé pour calculer la relation masse-rayon de planètes synthétiques ayant un noyau de fer et un manteau de SiC. Concernant le système Fe-Si-C le diagramme de phase ternaire a été reconstruit. En faisant l’hypothèse d’une composition Fe-Si-C pour un noyau planétaire, quatre différentes séquences de cristallisation ont été démontrées, déterminant des comportements dynamiques très diffèrent. En conclusion la relation masse-rayon n’est pas suffisante pour déterminer la composition et la structure interne des exoplanètes observées mais des données relatives à la chimie du système planétaire sont requises