Geosciences
The study of pits, skylights, and sinkholes on terrestrial bodies is vital for mapping subsurface voids, geological evolution, and potentially habitable zones. Feature identification remains constrained by sensor resolution and the complexities of radar analysis. This research explores deep learning computer vision to automate landform mapping and evaluates detecting subsurface voids using orbital radar.
To address mapping challenges, this work introduces DeepLandforms, a toolkit developed to automate detection using You Only Look Once (YOLO), Detectron 2, and the Segment Anything Model (SAM). Built on Docker, it includes modules for data preparation, training, and inference, generating outputs compatible with GIS software. Validation against a dataset from the Mars Global Cave Candidate (MGC³) catalog demonstrates capacity for consistent, large-scale surveys.
This research also introduces EchoTerraeTrace, an all-in-one toolkit providing workflows for SHARAD (Mars Reconnaissance Orbiter) and MARSIS (Mars Express) data. During validation North-West of Ascraeus Mons, three unmapped volcanic vents were identified, and the regional paleotopography was refined.
Finally, this research assesses planetary software against FAIR principles. A web-based service built on a dockerized JupyterHub was developed as an all-in-one environment for standardized data processing. This service provides scalability without requiring local high-end resources, supporting reproducible research by moving the code to the data rather than the data to the code.
Rare earth elements (REE, or REY including yttrium) are widely used in modern technologies and are increasingly released into aquatic environments. Their environmental behaviour and bioaccumulation in aquatic ecosystems remain poorly understood. This thesis investigates the bioavailability, bioaccumulation, and trophic transfer of both geogenic and anthropogenic REY using aquatic organisms and environmental samples from European freshwater and marine systems.
Shells of three invasive freshwater bivalves (Corbicula fluminea, Dreissena polymorpha, and Dreissena bugensis) collected from seven major European rivers show strong REY bioaccumulation, with concentrations up to five orders of magnitude higher than in ambient water. Anthropogenic lanthanum contamination from the Rhine River was recorded in mussel shells, whereas no enrichment of anthropogenic gadolinium from MRI contrast agents was observed, suggesting its stability in freshwater systems.
Further analyses of freshwater (Anodonta anatina) and marine (Mytilus edulis) mussels reveal higher REY concentrations in internal organs than in muscle tissues and shells, while biological processes exert only minor influence on REY fractionation. A trophic-level study along the Rhine River shows a general biodilution trend from primary producers to fish, while shale-normalised REY patterns remain consistent across trophic levels. These results indicate that mussels can serve as effective biomonitors for environmental REY contamination.
Our modern society relies heavily on the availability and utilisation of rare earth elements and yttrium (REY) for high-tech products and processes, which provokes a growing release of these metals into the environment and draws attention to biological and ecotoxicological consequences of their increasing concentrations in the environment. However, research has long neglected the environmental behaviour of REY. Coupled with publications including incomplete REY sets or data of questionable analytical quality, many open questions remain.
This dissertation investigates samples from the biosphere and from the hydrosphere to shed light on the REY transfer at their interface. Duckweeds, widely occurring small water plants, and Norwegian fjord waters together with Baltic Sea outflow samples were chosen as main study objects from the biosphere and the hydrosphere, respectively.
The findings of the biosphere-focused part improve the characterisation of the duckweed reference material BCR-670 (Lemna minor) and highlight the necessity of comparable sample processing for validation of data quality.
All naturally grown duckweeds investigated are REY quasi-hyperaccumulators and share similarly shaped, mildly fractionated shale-normalised REY patterns without positive anthropogenic Gd anomalies, regardless of whether they grew in waters with or without anomalous Gd enrichment.
The hydrosphere-focused part presents the first evidence for constant anthropogenic Gd input into the Baltic Sea outflow. The data combined with literature data further suggest that this signal is transported to southern Norway. In future, it may reach fjord waters further north along the Norwegian coast.
Overall, this dissertation provides important new information about the fate of geogenic and anthropogenic REY at the hydrosphere-biosphere interface and highlights the relevance of basic research as the basis for understanding the complex REY transfer mechanisms across environmental compartments.
Rapidly expanding anthropogenic activities are generating increasing volumes of wastewater globally each year, the majority of which remains inadequately treated before being released into aquatic ecosystems. Microalgal technologies offer a promising alternative for nutrient recovery in wastewater treatment, demonstrating significant advantages over conventional methods that are often energy-intensive and costly. Inadequate treatment not only leads to environmental pollution but also results in the irreversible loss of valuable nutrients, thereby disrupting the nutrient cycle. In recent years, the extraction of bioactive compounds from microalgae has attracted substantial attention. However, much of the research has remained confined to laboratory-scale studies with a focus on either energy efficiency or bioproduct synthesis, limiting their practical applicability. A major bottleneck in the scalability of algal-based systems is the energy- and cost-intensive nature of biomass harvesting, which can contribute up to 20–30% of total downstream processing costs. Additionally, the dependence on sunlight and large land areas further restricts the feasibility of microalgae-based wastewater treatment technologies in diverse environments. This study addresses three critical challenges associated with algae-based wastewater treatment. First, an innovative cultivation approach was developed to enable continuous wastewater treatment across two contrasting seasonal conditions—summer and winter. Second, the characteristics of wastewater post-treatment were analysed to identify fouling factors affecting the harvesting process. Third, a novel strategy was implemented to induce “hyper compensation” and “luxury uptake” of inorganic phosphorus by microalgae, achieving an exceptional phosphorus recovery rate of nearly 96%. To fully capitalize on the treated biomass, a novel bioplastic/bio-composite was developed by combining polylactic acid with phosphorus-enriched microalgae.
In this research, I explored the geology of igneous intrusive domes in the Moon and Mars. These structures have not been widely investigated outside Earth, mainly due to the difficulty in locating them. I decided to do a detailed analysis of two systems: the Valentine Domes on the Moon, and the Utopia Planitia Dome field on Mars, focusing on their properties at the surface. I followed a cartographic approach in this research, using geostratigraphic units to characterize the locations and define their geological evolution. While analyzing the Valentine Domes, I noticed the lack of an open-source tool to work with the spectral data of the Moon, this led to the creation of the MoonIndex library, a tool to process spectral cubes and generate spectral indexes for the Moon. With the aid of MoonIndex, I performed the geological analysis of the Valentine Domes. The first result was the discovery of a new dome, which was detected by using the aspect parameter. I also found that several smaller structures such as rilles, dykes, and secondary domes are associated with the main domes. The dome field in Utopia Planitia is different from the lunar location, hundreds of domes were emplaced in a large area. The study of the domes showed they originated from an intrusive-to-extrusive system, since their shapes range from cryptodomes to volcanic domes. The lunar and Martian domes show some similarities, they are basaltic, have a small incidence in the surface morphology, and their parental magmas took advantage of structural features to reach the surface. However, the genesis of the system is different. The Valentine Domes formed under a polygenetic style, while the dome field in Utopia Planitia originated in a monogenetic system. This research will open the door to discovering new intrusive systems and to better understand the ones already known.
The Amazon is the largest River on earth, accounting for 15–20% of the global river freshwater discharge, and making it an important source of trace metals, nutrients and organic matter to the Atlantic Ocean. The nearby Pará River is the 5th largest river and converges to mix in the Amazon Estuary. Trace metals in the ocean (e.g., Mn, Co, Fe, Ni, Cu, Zn, Cd and Pb) act as important nutrients and/or toxins to marine organisms. However, no data exists for these trace metals in the Amazon Estuary after 1976. Therefore, it is of urgent importance to establish a baseline for trace metals in the Amazon estuary. A GEOTRACES process study (cruise GApr11) was conducted in the Amazon estuary during the wet season (April–May) of 2018. Herein we present data for dissolved trace metals and organic matter from samples collected from this cruise. Chapter 1 focuses on copper (Cu), a micronutrient and potential toxin, and its complexation to organic ligands. Chapter 2 discusses two other micronutrients, cobalt (Co) and nickel (Ni), in surface and depth samples analyzed by two different methods. Chapter 3 brings together all trace metals from this study (Al, Mn, Co, Fe, Ni, Cu, Zn, Cd, Pb and U) to calculate the fluxes from the Amazon and Pará Rivers into the Atlantic Ocean. Finally, chapter 4 describes depth profiles of bioactive metals in different size fractions. Trace metal cycling in the estuary was influenced by complex biogeochemical processes, including ligand complexation, particle adsorption-desorption, colloidal flocculation, physical mixing and biological activity. In addition, we observed distinct influences from the Amazon and Pará Rivers, which draw from distinct catchment areas. Cu was mostly conservative with respect to salinity, while Fe and Pb were highly particle reactive during early mixing and experienced the greatest estuary removal. We estimated that the Amazon and Pará Rivers account for ~21% and 18% of the global riverine Cu and Ni to the oceans.
Marine chemical sedimentary rocks, like banded iron formations (BIFs), ferromanganese (Fe-Mn) crusts and nodules, marine carbonates or cherts, are of great scientific interest because they can preserve primary information on the physico-chemical conditions of ambient seawater. Especially for research on the Precambrian, marine chemical sedimentary rocks are invaluable archives as they are the only remaining access point to the geochemical conditions of the Archaean and Palaeoproterozoic marine environment. This PhD thesis investigates the geochemical partner couples of gallium, aluminium (Ga-Al), germanium, and silicon (Ge-Si). Those two couples show mostly coherent geochemical behaviour in igneous and clastic sedimentary processes. However, in (low- low-temperature) aqueous environments, both partners decouple from each other. This thesis aims to investigate the behaviour of Ga-Al and Ge-Si during the precipitation of Fe (oxyhydr)oxides in the natural environment and to elaborate on whether characteristic distributions of Ga/Al and Ge/Si ratios in marine chemical sedimentary rocks can be applied as geochemical proxies.
This PhD thesis focuses on the investigation of high-temperature hydrothermal vent fluids from multiple vent sites between the North-Eastern Lau Spreading Center and the Tofua arc.
The sampling area is located in the northeastern part of the Lau Basin which is affected by some of earths’ highest subduction rate, a highly complex microplate tectonic, an influence of hot spot material from the Samoan mantle plume as well as the subduction of the Louisville Seamount Chain. This study extends our knowledge of high-temperature hydrothermal systems in the North-East Lau Basin, in that it reports for the first time on the chemical and isotopic composition of vent fluids from Maka volcano and Niuatahi volcano. This cumulative PhD thesis highlights the compositional variability of hydrothermal fluids associated with different geologic settings. The newly reported vent fluid data as well as systematic spatial distribution of trace metals and metalloids adds to our understanding of hydrothermal processes and in the future may help improve the estimates of element specific fluxes associated with seafloor hydrothermalism.
This thesis focuses on the biogeochemical interactions and behaviors of dissolved organic matter (DOM), metal bioaccumulations, and iron species in the Kairei and Pelagia hydrothermal vent fields in the Indian Ocean. Deep-sea vents have recently been identified as sources of DOM and dissolved metals in the ocean but the knowledge of their fates and their roles in global geochemical cycles is still scarce.
DOM compositions show that both vents are sources of DOS and reduced DOM in the Indian Ocean deep water. DOM compositions of both vent hot fluids were different than those which had undergone thermal abiotic alteration/degradation in previous experiments. This implies that additional processes and/or chemical reactions are involved during hydrothermal circulations.
In term of Fe stabilization and transportation, the results indicate that Fe(II) is the dominant Fe species in all hot fluid samples. Fe(III) becomes prominent in all diffuse fluids which indicates sub-seafloor mixing of endmember fluids with seawater. High [DFe] were observed in both vent plume samples. The voltammetric titrations reveal that Fe organic ligand complexes found in the plumes play a significant role in driving Fe mobilization and bioavailability in the deep water.
In both vents, dense benthic communities were found. Four ubiquitous benthic species were selected i.e., mussels (Bathymodolus septemdierum), scaly-foot snails (Chrysomallon squamiferum), shrimps (Rimicaris kairei) and crabs (Austinograea rodriguezensis) for the metal bioaccumulation study in the different tissue types. Most chalcophile elements are mainly accumulated in the organic tissues of the animals. Different degrees of metal partitioning were also observed between the various tissues and organs. High accumulations found in both vent benthic organisms suggest that the animals possess a similar advanced ability to acclimatize to high-and steady metal exposures like vent organisms in the Atlantic and Pacific Oceans.
For my PhD project I investigated the surface characteristics and
tested a possible formation mechanism of two Martian chaotic terrains: Arsinoes and Pyrrhae Chaos. These regions on Mars are characterized by the disruption of the basaltic bedrock into polygonal blocks, later covered by post-collapse sedimentary units. Such investigation included spectral analyses, that revealed the occurrence of basaltic mineralogies in the bedrock and hydrated minerals within and right outside Arsinoes Chaos, structural observations, that showed a prevalence of volcano-tectonic features in the area, and morpho-stratigraphic mapping, that allowed to have a clearer view on the geological history of these two chaotic terrains. Given the paucity of aqueous-related evidence, I developed a hypothesis for the formation mechanism that generated the collapse of chaotic terrain: a piecemeal caldera collapse. This particular type of collapse, known as chaotic caldera collapse, consists of multiple cycles of inflation and deflation of a buried magma chamber, resulting in the disruption of the overlying brittle materials into polygonal blocks, bounded by intersecting radial and concentric faults. This hypothesis was tested in an analog experiment in laboratory, where the process was reproduced, and the results suggest that piecemeal caldera collapse could in fact explain the peculiar characteristics of chaotic terrains, without involving water (either liquid or ice): this would justify the formation of those chaotic terrains where outflow channels and any fluvial feature are not present, and hydrated minerals are exiguous. In the experiment, the comparison was made also with a similar type of terrain, occurring both on Mars and on the Moon (where aquifers do not exist), the Floor-Fractured craters (FFCs). The last part of my project was dedicated to structural analyses on the faults within Lunar FFCs, providing more insights on the complex geological history of these heavily fractured terrains.
