Sedimentary rocks of the Internal Hellenides, Greece: age, source, and depositional setting

Ziel der vorliegenden Dissertation war die Untersuchung der Liefergebiete und Ablagerungsräume sedimentärer Gesteine aus ausgewählten Gebieten der inneren Helleniden Griechenlands. Die untersuchten Sedimente Nordgriechenlands gehören zu den Pirgadikia und Vertiskos Einheiten des Serbo-Makedonische Massifs, zu den Examili, Melissochori und Prinochori Formationen der östlichen Vardar Zone und zur Makri Einheit und Melia Formation des östlichen Zirkum-Rhodope-Gürtels in Thrakien. In der östlichen Ägäis lag der Schwerpunkt bei den Sedimenten der Insel Chios. Der Metamorphosegrad der untersuchten Gesteine variiert von der untersten Grünschieferfazies bis hin zur Amphibolitfazies. Das stratigraphische Alter reicht vom Ordovizium bis zur Kreide. Zur Charakterisierung der Gesteine und ihrer Liefgebiete wurden Haupt- und Spurenelementgehalte der Gesamtgesteine bestimmt, mineralchemische Analysen durchgeführt und detritische Zirkone mit U–Pb datiert. An ausgewählten Proben wurden außerdem biostratigraphische Untersuchungen zur Bestimmung des Sedimentationsalters durchgeführt. Die Untersuchungsergebnisse dieser Arbeit sind von großer Bedeutung für paläogeographische Rekonstruktionen der Tethys. Die wichtigsten Ergebnisse lassen sich wie folgt zusammenfassen: Die ältesten Sedimente Nordgriechenlands gehören zur Pirgadikia Einheit des Serbo-Makedonischen Massifs. Es sind sehr reife, quarzreiche, siliziklastische Metasedimente, die auf Grund ihrer Maturität und ihrer detritischen Zirkone mit ordovizischen overlap-Sequenzen vom Nordrand Gondwanas korreliert werden können. Die Metasedimente der Vertiskos Einheit besitzen ein ähnliches stratigraphisches Alter, haben aber einen anderen Ablagerungsraum. Das Altersspektrum detritischer Zirkone lässt auf ein Liefergebiet im Raum NW Afrikas (Hun Superterrane) schließen. Die Gesteinsassoziation der Vertiskos Einheit wird als Teil einer aktiven Kontinentalrandabfolge gesehen. Die ältesten biostratigraphisch datierten Sedimente Griechenlands sind silurische bis karbonische Olistolithe aus einer spätpaläozoischen Turbidit-Olistostrom Einheit auf der Insel Chios. Die Alter detritischer Zirkone und die Liefergebietsanalyse der fossilführenden Olistolithe lassen den Schluss zu, dass die klastischen Sedimente von Chios Material vom Sakarya Mikrokontinent in der West-Türkei und faziellen Äquivalenten zu paläozoischen Gesteinen der Istanbul Zone in der Nord-Türkei und der Balkan Region erhalten haben. Während der Permotrias wurde die Examili Formation der östlichen Vardar Zone in einem intrakontinentalen, sedimentären Becken, nahe der Vertiskos Einheit abgelagert. Untergeordnet wurde auch karbonisches Grundgebirgsmaterial eingetragen. Im frühen bis mittleren Jura wurde die Melissochori Formation der östlichen Vardar Zone am Abhang eines karbonatführenden Kontinentalrandes abgelagert. Der Großteil des detritischen Materials kam von permokarbonischem Grundgebirge vulkanischen Ursprungs, vermutlich von der Pelagonischen Zone und/oder der unteren tektonischen Einheit des Rhodope Massifs. Die Makri Einheit in Thrakien besitzt vermutlich ein ähnliches Alter wie die Melissochori Formation. Beide sedimentären Abfolgen ähneln sich sehr. Der Großteil des detritischen Materials für die Makri Einheit kam vom Grundgebirge der Pelagonischen Zone oder äquivalenten Gesteinen. Während der frühen Kreide wurde die Prinochori Formation der östlichen Vardar Zone im Vorfeld eines heterogenen Deckenstapels abgelagert, der ophiolitisches Material sowie Grundgebirge ähnlich zu dem der Vertiskos Einheit enthielt. Ebenfalls während der Kreidezeit wurde in Thrakien, vermutlich im Vorfeld eines metamorphen Deckenstapels mit Affinitäten zum Grundgebirge der Rhodopen die Melia Formation abgelagert. Zusammenfassend kann festgehalten werden, dass die Subduktion eines Teiles der Paläotethys und die anschließende Akkretion vom Nordrand Gondwanas stammender Mikrokontinente (Terranes) nahe dem südlichen aktiven Kontinentalrand Eurasiens den geodynamischen Rahmen für die Schüttung des detritischen Materials der Sedimente der inneren Helleniden im späten Paläozoikum bildeten. Die darauf folgenden frühmesozoischen Riftprozesse leiteten die Bildung von Ozeanbecken der Neotethys ein. Intraozeanische Subduktion und die Obduzierung von Ophioliten prägten die Zeit des Jura. Die spätjurassische und frühkretazische tektonische Phase wurde durch die Ablagerung von mittelkretazischen Kalksteinen besiegelt. Die endgültige Schließung von Ozeanbecken der Neotethys im Bereich der inneren Helleniden erfolgte schließlich in der späten Kreide und im Tertiär.

Corrosione atmosferica in area urbana-costiera di un acciaio Cor-Ten: studio del rilascio in ambiente dei metalli di lega

Cor-Ten is a particular kind of steel, belonging to low-alloyed steel; thanks to his aesthetic features and resistance to atmospheric corrosion, this material is largely used in architectural, artistic and infrastructural applications. After environmental exposure, Cor-Ten steel exhibits the characteristic ability to self-protect from corrosion, by the development of a stable and adherent protective layer. However, some environmental factors can influence the formation and stability of the patina. In particular, exposure of Cor-Ten to polluted atmosphere (NOx, SOx, O3) or coastal areas (marine spray) may cause problems to the protective layer and, as a consequence, a release of alloying metals, which can accumulate near the structures. Some of these metals, such as Cr and Ni, could be very dangerous for soils and water because of their large toxicity. The aim of this work was to study the corrosion behavior of Cor-Ten exposed to an urban-coastal site (Rimini, Italy). Three different kinds of commercial surface finish (bare and pre-patinated, with or without a beeswax covering) were examined, both in sheltered and unsheltered exposure conditions. Wet deposition brushing the specimens surface (leaching solutions) are monthly collected and analyzed to evaluate the extent of metal release and the form in which they leave the surface, for example, as water-soluble compounds or non-adherent corrosion products. Five alloying metals (Fe, Cu, Cr, Mn and Ni) and nine ions (Cl-, NO3-, NO2-, SO42-, Na+, Ca2+, K+, Mg2+, NH4+) are determined through Atomic Absorption Spectroscopy and Ion Chromatography, respectively. Furthermore, the evolution and the behaviour of the patina are periodically followed by surface investigations (SEM-EDS and Raman Spectroscopy). After two years of exposure, the results show that Bare Cor-Ten, cheaper than the other analyzed specimens, even though undergoes the greater mass variation, his metal release is comparable to the release of the pre-patinated samples. The behavior of pre-patinated steel, with or without beeswax covering, do not show particular difference. This exposure environment doesn’t allow a completely stabilization of the patina; nevertheless an estimate of metal release after 10 years of exposure points out that the environmental impact of Cor-Ten is very low: for example, the release of chromium in the soluble fraction is less than 10 mg if we consider an exposed wall of 10 m2.

Mediterranean-type climate in the South Aegean (Eastern Mediterranean) during the Late Miocene: Evidence from isotope and element proxies

The present-day climate in the Mediterranean region is characterized by mild, wet winters and hot, dry summers. There is contradictory evidence as to whether the present-day conditions (“Mediterranean climate”) already existed in the Late Miocene. This thesis presents seasonally-resolved isotope and element proxy data obtained from Late Miocene reef corals from Crete (Southern Aegean, Eastern Mediterranean) in order to illustrate climate conditions in the Mediterranean region during this time. There was a transition from greenhouse to icehouse conditions without a Greenland ice sheet during the Late Miocene. Since the Greenland ice sheet is predicted to melt fully within the next millennia, Late Miocene climate mechanisms can be considered as useful analogues in evaluating models of Northern Hemispheric climate conditions in the future. So far, high resolution chemical proxy data on Late Miocene environments are limited. In order to enlarge the proxy database for this time span, coral genus Tarbellastraea was evaluated as a new proxy archive, and proved reliable based on consistent oxygen isotope records of Tarbellastraea and the established paleoenvironmental archive of coral genus Porites. In combination with lithostratigraphic data, global 87Sr/86Sr seawater chronostratigraphy was used to constrain the numerical age of the coral sites, assuming the Mediterranean Sea to be equilibrated with global open ocean water. 87Sr/86Sr ratios of Tarbellastraea and Porites from eight stratigraphically different sampling sites were measured by thermal ionization mass spectrometry. The ratios range from 0.708900 to 0.708958 corresponding to ages of 10 to 7 Ma (Tortonian to Early Messinian). Spectral analyses of multi-decadal time-series yield interannual δ18O variability with periods of ~2 and ~5 years, similar to that of modern records, indicating that pressure field systems comparable to those controlling the seasonality of present-day Mediterranean climate existed, at least intermittently, already during the Late Miocene. In addition to sea surface temperature (SST), δ18O composition of coral aragonite is controlled by other parameters such as local seawater composition which as a result of precipitation and evaporation, influences sea surface salinity (SSS). The Sr/Ca ratio is considered to be independent of salinity, and was used, therefore, as an additional proxy to estimate seasonality in SST. Major and trace element concentrations in coral aragonite determined by laser ablation inductively coupled plasma mass spectrometry yield significant variations along a transect perpendicular to coral growth increments, and record varying environmental conditions. The comparison between the average SST seasonality of 7°C and 9°C, derived from average annual δ18O (1.1‰) and Sr/Ca (0.579 mmol/mol) amplitudes, respectively, indicates that the δ18O-derived SST seasonality is biased by seawater composition, reducing the δ18O amplitude by 0.3‰. This value is equivalent to a seasonal SSS variation of 1‰, as observed under present-day Aegean Sea conditions. Concentration patterns of non-lattice bound major and trace elements, related to trapped particles within the coral skeleton, reflect seasonal input of suspended load into the reef environment. δ18O, Sr/Ca and non-lattice bound element proxy records, as well as geochemical compositions of the trapped particles, provide evidence for intense precipitation in the Eastern Mediterranean during winters. Winter rain caused freshwater discharge and transport of weathering products from the hinterland into the reef environment. There is a trend in coral δ18O data to more positive mean δ18O values (–2.7‰ to –1.7‰) coupled with decreased seasonal δ18O amplitudes (1.1‰ to 0.7‰) from 10 to 7 Ma. This relationship is most easily explained in terms of more positive summer δ18O. Since coral diversity and annual growth rates indicate more or less constant average SST for the Mediterranean from the Tortonian to the Early Messinian, more positive mean and summer δ18O indicate increasing aridity during the Late Miocene, and more pronounced during summers. The analytical results implicate that winter rainfall and summer drought, the main characteristics of the present-day Mediterranean climate, were already present in the Mediterranean region during the Late Miocene. Some models have argued that the Mediterranean climate did not exist in this region prior to the Pliocene. However, the data presented here show that conditions comparable to those of the present-day existed either intermittently or permanently since at least about 10 Ma.

Neoproterozoic to middle Palaeozoic evolution of the Central Asian Orogenic Belt in south-central Mongolia: chronological and geochemical perspectives

Mongolia occupies a central position within the eastern branch of the large accretionary Central Asian Orogenic Belt (CAOB) or Altaids. The present work aims to outline the geodynamic environment and possible evolution of this part of the eastern CAOB, predominantly from the Cambrian to the middle Palaeozoic. The investigation primarily focussed on zircon geochronology as well as whole-rock geochemical and Sm–Nd isotopic analyses for a variety of metaigneous rocks from the southern Hangay and Gobi-Altai regions in south-central Mongolia. The southern slope of the Hangay Mountains in central Mongolia exposes a large NWSE-trending middle Neoproterozoic ophiolitic complex (c. 650 Ma), which is tectonically integrated within an accretionary complex developed between the Precambrian Baydrag and Hangay crustal blocks. Formation of the entire accretionary system along the north-eastern margin of the Baydrag block mainly occurred during the early Cambrian, but convergence within this orogenic zone continued until the early Ordovician, because of on-going southward subduction-accretion of the Baydrag block. An important discovery is the identification of a late Mesoproterozoic to early Neoproterozoic belt within the northern Gobi-Altai that was reworked during the late Cambrian and throughout the late Ordovician/Devonian. Early Silurian low-grade mafic and felsic metavolcanic rocks from the northern Gobi-Altai display subduction-related geochemical features and highly heterogeneous Nd isotopic compositions, which suggest an origin at a mature active continental margin. Early Devonian protoliths of granodioritic and mafic gneisses from the southern Gobi-Altai display geochemical and Nd isotopic compositions compatible with derivation and evolution from predominantly juvenile crustal and mantel sources and these rocks may have been emplaced within the outboard portion of the late Ordovician/early Silurian active continental margin. Moreover, middle Devonian low-grade metavolcanic rocks from the southwestern Gobi-Altai yielded geochemical and Nd isotopic data consistent with emplacement in a transitional arc-backarc setting. The combined U–Pb zircon ages and geochemical data obtained from the Gobi-Altai region suggest that magmatism across an active continental margin migrated oceanwards through time by way of subduction zone retreat throughout the Devonian. Progressive extension of the continental margin was associated with the opening of a backarc basin and culminated in the late Devonian with the formation of a Japan-type arc front facing a southward open oceanic realm (present-day coordinates).

Copper and zinc stable isotope ratios as tracers of biogeochemical processes, sources and transport of Cu and Zn in soils

Copper and Zn are essential micronutrients for plants, animals, and humans; however, they may also be pollutants if they occur at high concentrations in soil. Therefore, knowledge of Cu and Zn cycling in soils is required both for guaranteeing proper nutrition and to control possible risks arising from pollution.rnThe overall objective of my study was to test if Cu and Zn stable isotope ratios can be used to investigate into the biogeochemistry, source and transport of these metals in soils. The use of stable isotope ratios might be especially suitable to trace long-term processes occurring during soil genesis and transport of pollutants through the soil. In detail, I aimed to answer the questions, whether (1) Cu stable isotopes are fractionated during complexation with humic acid, (2) 65Cu values can be a tracer for soil genetic processes in redoximorphic soils (3) 65Cu values can help to understand soil genetic processes under oxic weathering conditions, and (4) 65Cu and 66Zn values can act as tracers of sources and transport of Cu and Zn in polluted soils.rnTo answer these questions, I ran adsorption experiments at different pH values in the laboratory and modelled Cu adsorption to humic acid. Furthermore, eight soils were sampled representing different redox and weathering regimes of which two were influenced by stagnic water, two by groundwater, two by oxic weathering (Cambisols), and two by podzolation. In all horizons of these soils, I determined selected basic soil properties, partitioned Cu into seven operationally defined fractions and determined Cu concentrations and Cu isotope ratios (65Cu values). Finally, three additional soils were sampled along a deposition gradient at different distances to a Cu smelter in Slovakia and analyzed together with bedrock and waste material from the smelter for selected basic soil properties, Cu and Zn concentrations and 65Cu and 66Zn values.rnMy results demonstrated that (1) Copper was fractionated during adsorption on humic acid resulting in an isotope fractionation between the immobilized humic acid and the solution (65CuIHA-solution) of 0.26 ± 0.11‰ (2SD) and that the extent of fractionation was independent of pH and involved functional groups of the humic acid. (2) Soil genesis and plant cycling causes measurable Cu isotope fractionation in hydromorphic soils. The results suggested that an increasing number of redox cycles depleted 63Cu with increasing depth resulting in heavier 65Cu values. (3) Organic horizons usually had isotopically lighter Cu than mineral soils presumably because of the preferred uptake and recycling of 63Cu by plants. (4) In a strongly developed Podzol, eluviation zones had lighter and illuviation zones heavier 65Cu values because of the higher stability of organo-65Cu complexes compared to organo-63Cu complexes. In the Cambisols and a little developed Podzol, oxic weathering caused increasingly lighter 65Cu values with increasing depth, resulting in the opposite depth trend as in redoximorphic soils, because of the preferential vertical transport of 63Cu. (5) The 66Zn values were fractionated during the smelting process and isotopically light Zn was emitted allowing source identification of Zn pollution while 65Cu values were unaffected by the smelting and Cu emissions isotopically indistinguishable from soil. The 65Cu values in polluted soils became lighter down to a depth of 0.4 m indicating isotope fractionation during transport and a transport depth of 0.4 m in 60 years. 66Zn values had an opposite depth trend becoming heavier with depth because of fractionation by plant cycling, speciation changes, and mixing of native and smelter-derived Zn. rnCopper showed measurable isotope fractionation of approximately 1‰ in unpolluted soils, allowing to draw conclusions on plant cycling, transport, and redox processes occurring during soil genesis and 65Cu and 66Zn values in contaminated soils allow for conclusions on sources (in my study only possible for Zn), biogeochemical behavior, and depth of dislocation of Cu and Zn pollution in soil. I conclude that stable Cu and Zn isotope ratios are a suitable novel tool to trace long-term processes in soils which are difficult to assess otherwise.rn

Diversity of lithologic components at Meridiani Planum, Mars: Insights from Mössbauer spectroscopic investigations

The two Mars Exploration Rovers (MER), Spirit and Opportunity, landed on the Martian surface in January 2004 and have since collected a wealth of information about their landing sites. As part of their payload, the miniaturised Mössbauer spectrometer MIMOS II contributes to the success of the mission by identifying Iron-bearing minerals and by determining Iron oxidation states in them. The basis of this work is the data set obtained at Opportunity’s landing site at Meridiani Planum. A portion of this data set is evaluated with different methods, with the aim to thoroughly characterize lithologic components at Meridiani Planum and possible relations between them.rnMIMOS II is able to measure Mössbauer spectra at different energies simultaneously, bearing information from different sampling depths of the investigated target. The ability of depth-selective Mössbauer spectroscopy to characterize weathered surface layers is illustrated through its application to two suitable rock targets that were investigated on Mars. In both cases, an enhanced concentration of Iron oxides at the rock surface was detected, pointing to a low degree of aqueous alteration. rnThe mineral hematite (α-Fe2O3) is present in the matrix of outcrop rocks and in spherules weathering from the outcrop. Simultaneous fitting of Mössbauer spectra was applied to data sets obtained on both target types to characterize the hematite component in detail. This approach reveals that two hematite populations are present, both in the outcrop matrix as well as in spherules. The hematite component with a comparably high degree of crystallinity and/or chemical purity is present in the outcrop matrix. The investigation of hematite at Meridiani Planum has shown that simultaneous fitting is a suitable and useful method to evaluate a large, correlated set of Mössbauer spectra.rnOpportunity encountered loose, cm-sized rocks along its traverse. Based on their composition and texture, these “cobbles” can be divided into three different groups. Outcrop fragments are impact-derived ejecta from local outcrop rocks. Cobbles of meteoritic origin contain the minerals kamacite (Fe,Ni) and troilite (FeS) and exhibit high Ni contents. Melt-bearing impact breccias bear similarities to local outcrop rocks and basaltic soil, with a phase composition and texture consistent with a formation scenario involving partial melting and inclusion of small, bright outcrop clasts. rnIron meteorites on the Martian surface experience weathering through the presence of even trace amounts of water due to their metallic nature. Opportunity encountered and investigated four Iron meteorites, which exhibit evidence for physical and chemical weathering. Discontinuous coatings contain Iron oxides, pointing to the influence of limited amounts of water. rnA terrestrial analogue site for Meridiani Planum is the Rio Tinto basin in south-west Spain. With its deposits of sulfate- and iron-oxide-bearing minerals, the region provides an adequate test bed for instrumentation for future Mars missions. In-situ investigations at Rio Tinto were carried out with a special focus on the combined use of Mössbauer spectroscopy with MIMOS II and Raman spectroscopy with a field-portable instrument. The results demonstrate that the two instruments provide complementary information about investigated samples.

Speleogenesis and secondary cave minerals in quartz-sandstone and quartzite environment

The main objective of this research is to improve the comprehension of the processes controlling the formation of caves and karst-like morphologies in quartz-rich lithologies (more than 90% quartz), like quartz-sandstones and metamorphic quartzites. In the scientific community the processes actually most retained to be responsible of these formations are explained in the “Arenisation Theory”. This implies a slow but pervasive dissolution of the quartz grain/mineral boundaries increasing the general porosity until the rock becomes incohesive and can be easily eroded by running waters. The loose sands produced by the weathering processes are then evacuated to the surface through processes of piping due to the infiltration of waters from the fracture network or the bedding planes. To deal with these problems we adopted a multidisciplinary approach through the exploration and the study of several cave systems in different tepuis. The first step was to build a theoretical model of the arenisation process, considering the most recent knowledge about the dissolution kinetics of quartz, the intergranular/grain boundaries diffusion processes, the primary diffusion porosity, in the simplified conditions of an open fracture crossed by a continuous flow of undersatured water. The results of the model were then compared with the world’s widest dataset (more than 150 analyses) of water geochemistry collected till now on the tepui, in superficial and cave settings. All these studies allowed verifying the importance and the effectiveness of the arenisation process that is confirmed to be the main process responsible of the primary formation of these caves and of the karst-like superficial morphologies. The numerical modelling and the field observations allowed evaluating a possible age of the cave systems around 20-30 million of years.

Teos-based consolidants for stone conservation: evaluation of the effects and testing by x-ray imaging

Natural stones have been widely used in the construction field since antiquity. Building materials undergo decay processes due to mechanical,chemical, physical and biological causes that can act together. Therefore an interdisciplinary approach is required in order to understand the interaction between the stone and the surrounding environment. Utilization of buildings, inadequate restoration activities and in general anthropogenic weathering factors may contribute to this degradation process. For this reasons, in the last few decades new technologies and techniques have been developed and introduced in the restoration field. Consolidants are largely used in restoration and conservation of cultural heritage in order to improve the internal cohesion and to reduce the weathering rate of building materials. It is important to define the penetration depth of a consolidant for determining its efficacy. Impregnation mainly depends on the microstructure of the stone (i.e. porosity) and on the properties of the product itself. Throughout this study, tetraethoxysilane (TEOS) applied on globigerina limestone samples has been chosen as object of investigation. After hydrolysis and condensation, TEOS deposits silica gel inside the pores, improving the cohesion of the grains. X-ray computed tomography has been used to characterize the internal structure of the limestone samples,treated and untreated with a TEOS-based consolidant. The aim of this work is to investigate the penetration depth and the distribution of the TEOS inside the porosity, using both traditional approaches and advanced X-ray tomographic techniques, the latter allowing the internal visualization in three dimensions of the materials. Fluid transport properties and porosity have been studied both at macroscopic scale, by means of capillary uptake tests and radiography, and at microscopic scale,investigated with X-ray Tomographic Microscopy (XTM). This allows identifying changes in the porosity, by comparison of the images before and after the treatment, and locating the consolidant inside the stone. Tests were initially run at University of Bologna, where characterization of the stone was carried out. Then the research continued in Switzerland: X-ray tomography and radiography were performed at Empa, Swiss Federal Laboratories for Materials Science and Technology, while XTM measurements with synchrotron radiation were run at Paul Scherrer Institute in Villigen.

Process-based modelling of lichens and bryophytes and their role in global biogeochemical cycles

This thesis presents a process-based modelling approach to quantify carbon uptake by lichens and bryophytes at the global scale. Based on the modelled carbon uptake, potential global rates of nitrogen fixation, phosphorus uptake and chemical weathering by the organisms are estimated. In this way, the significance of lichens and bryophytes for global biogeochemical cycles can be assessed. The model uses gridded climate data and key properties of the habitat (e.g. disturbance intervals) to predict processes which control net carbon uptake, namely photosynthesis, respiration, water uptake and evaporation. It relies on equations used in many dynamical vegetation models, which are combined with concepts specific to lichens and bryophytes, such as poikilohydry or the effect of water content on CO2 diffusivity. To incorporate the great functional variation of lichens and bryophytes at the global scale, the model parameters are characterised by broad ranges of possible values instead of a single, globally uniform value. The predicted terrestrial net uptake of 0.34 to 3.3 Gt / yr of carbon and global patterns of productivity are in accordance with empirically-derived estimates. Based on the simulated estimates of net carbon uptake, further impacts of lichens and bryophytes on biogeochemical cycles are quantified at the global scale. Thereby the focus is on three processes, namely nitrogen fixation, phosphorus uptake and chemical weathering. The presented estimates have the form of potential rates, which means that the amount of nitrogen and phosphorus is quantified which is needed by the organisms to build up biomass, also accounting for resorption and leaching of nutrients. Subsequently, the potential phosphorus uptake on bare ground is used to estimate chemical weathering by the organisms, assuming that they release weathering agents to obtain phosphorus. The predicted requirement for nitrogen ranges from 3.5 to 34 Tg / yr and for phosphorus it ranges from 0.46 to 4.6 Tg / yr. Estimates of chemical weathering are between 0.058 and 1.1 km³ / yr of rock. These values seem to have a realistic order of magnitude and they support the notion that lichens and bryophytes have the potential to play an important role for global biogeochemical cycles.

Approccio metodologico per la valutazione del rischio dovuto agli sversamenti accidentali di petrolio in mare

Il trasporto del petrolio via mare tramite navi petroliere è molto utilizzato per congiungere i paesi produttori con quelli consumatori. Durante il trasporto possono avvenire rilasci accidentali di petrolio in mare, con contaminazione anche estesa dell’ambiente marino. La stima del rischio di contaminazione ambientale imputabile alle attività di trasporto via mare è fondamentale al fine di ridurre il rischio stesso. Per prevedere il destino degli sversamenti di olio in mare, sono stati sviluppati diversi software che simulano lo spostamento della chiazza di olio rilasciato e le trasformazioni chimico-fisiche cui essa è soggetta, dette fenomeni di oil weathering. L’obiettivo del presente lavoro di tesi è stato quello di individuare un software per la simulazione del destino dei rilasci di olio in mare idoneo ad essere utilizzato nell’ambito di una innovativa metodologia di valutazione del rischio per l’ambiente marino. A tal fine sono stati studiati e confrontati, sia da un punto di vista teorico sia tramite l’applicazione a casi di studio, i software GNOME, ADIOS e OSCAR; dal confronto è emerso che GNOME e ADIOS contengono modelli semplificati per simulare i fenomeni di oil weathering subiti da una chiazza di olio formatasi a seguito di un rilascio. Rispetto ai software GNOME e ADIOS, OSCAR è molto più complesso e articolato; richiede numerosi dati in ingresso, ma fornisce in uscita una descrizione dello scenario più aderente alla realtà. Un’importante peculiarità di OSCAR, che lo rende estremamente vantaggioso nell’ambito di una metodologia di valutazione del rischio, consiste nel fatto che esso dispone di una modalità di funzionamento stocastica. Per validare l’utilizzo di OSCAR nell’ambito di una metodologia di valutazione del rischio, se ne è effettuata l’applicazione ad un caso di studio, ovvero alla rotta da Suez a Porto Marghera. Si è pertanto osservato che il rischio derivante da un rilascio di olio in mare è dipendente dal punto in cui questo rilascio avviene. È dunque possibile concludere che il software OSCAR è uno strumento valido nell’analisi del rischio ambientale derivante da sversamenti di olio in mare. Il lavoro di tesi è strutturato come descritto nel seguito. Il Capitolo 1 è introduttivo e, dopo aver descritto la problematica legata agli sversamenti di idrocarburi in mare, elenca e spiega i fenomeni di oil weathering. Il Capitolo 2 è incentrato sulle caratteristiche e sul confronto dei software dell’ente americano NOAA, ossia ADIOS e GNOME. Il Capitolo 3 si occupa della descrizione del software OSCAR dell’ente norvegese SINTEF. Il Capitolo 4 riporta la metodologia seguita per il calcolo del rischio di contaminazione del mare, ripresa da una metodologia per il calcolo del rischio già consolidata nell’industria di processo relativa all’uomo. Il Capitolo 5 introduce il caso di studio, ovvero l’applicazione della metodologia alla rotta da Suez a Marghera. Il Capitolo 6 riporta alcune considerazioni conclusive.

Attività fotocatalitica del biossido di titanio applicato ai materiali da costruzione. Analisi delle prestazioni in funzione della tipologia di supporto e della tecnica di deposizione

I materiali fotocatalitici, se opportunamente irradiati con luce di una opportuna lunghezza d'onda, consentono un maggior abbattimento delle sostanze organiche e inorganiche nocive con le quali vengono a contatto. Essi sono in grado inoltre grazie alla loro spiccata idrofilia di conservare inalterato nel tempo il loro aspetto estetico. Il connubio ingegneria e chimica ha creato dunque materiali fotocatalitici contenenti al loro interno particelle di TiO2, il principale fotocatalizzatore in commercio, che, applicati in ambiti urbani ed edilizi come rivestimenti, pitture, rimescolato in pasta di malte o masselli autobloccanti, pitture o piastrelle antisettiche e vetri autopulenti, possono generare effetti positivi in termini sia di antinquinamento che di antibattericità. La tesi parte dalla descrizione delle reazioni chimiche che stanno alla base della fotocatalisi e prosegue descrivendo il fotocatalizzatore più attivo ed efficace fino ad ora scoperto, il TiO2. Nella seconda parte della tesi si citano le principali aziende italiane e mondiali che si sono impegnate nella produzione di materiali fotocatalitici, riportando le loro opere e i loro prodotti. Nella parte terza si vogliono invece fornire le informazioni generali attualmente conosciute sulla minaccia alla salute che può costituire l'utilizzo di materiali nanometrici come il TiO2. Nella parte quarta invece si risponde alle ancora frequenti domande riguardanti l'efficacia del TiO2 nelle applicazioni reali al variare del materiale di supporto, la sua efficacia nel lungo termine, il reale effetto autopulente nell'ambiente reale e nel suo impatto sull'ambiente. Si riportano i risultati di laboratorio riguardanti l'efficacia fotocatalitica in termini di degradazione di tinte e di angolo di contatto, direttamente applicati alla realtà delle costruzioni: su supporti diversi in termini di permeabilità e idrorepellenza, è stata applicata una sospensione acquosa fotocatalitica applicata sia a pennello che tramite getto spray HVLP. Alcuni campioni sono poi stati dilavati simulando l'azione atmosferica di weathering dell'area bolognese.

Geochimica dei sedimenti del Golfo di Tigullio antistanti Sestri Levante (GE)

I metalli pesanti sono presenti in natura come costituenti della crosta terrestre associati a diversi minerali. Attività antropiche possono determinare un arricchimento del loro contenuto in ambiente: nel caso della miniera di Libiola, da cui era estratto Cu fino agli anni ‘60, le fasi di estrazione e raffinazione del minerale hanno portato all’esposizione di una maggior quantità di materiale all’azione di weathering atmosferico e delle acque dei fiumi, accumulandosi in ambiente marino. Il presente studio ha l’obiettivo di caratterizzare i sedimenti del Golfo di Tigullio antistanti Sestri Levante per acquisire informazioni sulle caratteristiche e proprietà dell’ambiente, individuando e determinando l’effetto di quanto proviene del Torrente Gromolo e da altri corpi idrici affluenti. Per raggiungere questo obiettivo i campioni di sedimento, una volta prelevati, sono stati trattati in laboratorio tramite setacciatura, essiccamento e macinatura a cui sono seguite analisi in XRF, XRD e del contenuto di materia organica tramite calcolo della LOI. I dati raccolti sono stati poi studiati tramite elaborazioni statistiche (indici, matrice di correlazione, analisi fattoriale) e grafiche (QGIS). Dallo studio dei risultati ottenuti è stato possibile verificare una diversa ripartizione degli analiti in distinte fasi granulometriche del sedimento, l’effettivo contributo di quanto è drenato dai fiumi e la presenza di una corrente idrodinamica che influisce sulla distribuzione degli elementi stessi.

Integrated Geophysical Investigation of the St. James Fault Complex: A Case Study

We noninvasively detected the characteristics and location of a regional fault in an area of poor bedrock exposure complicated by karst weathering features in the subsurface. Because this regional fault is associated with sinkhole formation, its location is important for hazard avoidance. The bedrock lithologies on either side of the fault trace are similar; hence, we chose an approach that capitalized on the complementary strengths of very low frequency (VLF) electromagnetic, resistivity, and gravity methods. VLF proved most useful as a first-order reconnaissance tool, allowing us to define a narrow target area for further geophysical exploration. Fault-related epikarst was delineated using resistivity. Ultimately, a high-resolution gravity survey and subsequent inverse modeling using the results of the resistivity survey helped to further constrain the location and approximate orientation of the fault. The combined results indicated that the location of the fault trace needed to be adjusted 53 m south of the current published location and was consistent with a north-dipping thrust fault. Additionally, a gravity low south of the fault trace agreed with the location of conductive material from the resistivity and VLF surveys. We interpreted these anomalies to represent enhanced epikarst in the fault footwall. We clearly found that a staged approach involving a progression of methods beginning with a reconnaissance VLF survey, followed by high-resolution gravity and electrical resistivity surveys, can be used to characterize a fault and fault-related karst in an area of poor bedrock surface exposure.