ALBERT

Description: The Central and South Atlantic represents a vast ocean area and is home to a diverse range of ecosystems and species. Nevertheless, and similar to the rest of the global south, the area is comparatively understudied yet exposed to increasing levels of multisectoral pressures. To counteract this, the level of scientific exploration in the Central and South Atlantic has increased in recent years and will likely continue to do so within the context of the United Nations (UN) Decade of Ocean Science for Sustainable Development. Here, we compile the literature to investigate the distribution of previous scientific exploration of offshore (30 m+) ecosystems in the Central and South Atlantic, both within and beyond national jurisdiction, allowing us to synthesise overall patterns of biodiversity. Furthermore, through the lens of sustainable management, we have reviewed the existing anthropogenic activities and associated management measures relevant to the region. Through this exercise, we have identified key knowledge gaps and undersampled regions that represent priority areas for future research and commented on how these may be best incorporated into, or enhanced through, future management measures such as those in discussion at the UN Biodiversity Beyond National Jurisdiction negotiations. This review represents a comprehensive summary for scientists and managers alike looking to understand the key topographical, biological, and legislative features of the Central and South Atlantic.

Description: Ocean ecosystems are at the forefront of the climate and biodiversity crises, yet we lack a unified approach to assess their state and inform sustainable policies. This blueprint is designed around research capabilities and cross-sectoral partnerships. We highlight priorities including integrating basin-scale observation, modelling and genomic approaches to understand Atlantic oceanography and ecosystem connectivity; improving ecosystem mapping; identifying potential tipping points in deep and open ocean ecosystems; understanding compound impacts of multiple stressors including warming, acidification and deoxygenation; enhancing spatial and temporal management and protection. We argue that these goals are best achieved through partnerships with policy-makers and community stakeholders, and promoting research groups from the South Atlantic through investment and engagement. Given the high costs of such research (€800k to €1.7M per expedition and €30–40M for a basin-scale programme), international cooperation and funding are integral to supporting science-led policies to conserve ocean ecosystems that transcend jurisdictional borders.

Description: Elevated levels of arsenic (As) in soils and groundwaters remain a pressing global challenge due to its widespread occurrence and distribution, high toxicity and mobility. In oxygen-limited subsurface conditions, redox-active mineral phases can be important substrates in controlling the fate and mobility of As in the environment. Among these redox-active minerals, green rust (GR) phases, an Fe(II)-Fe(III)-bearing layered double hydroxide, have been shown to be able to sequester a wide range of toxic metals and metalloids, including As. However, very little is known regarding how GR phases interact with As species and what is the fate of the immobilized As under dynamic geochemical conditions. GR phases are suggested to form through the transformation of metastable iron mineral phases in non-sulfidic, reducing environments. However, the exact mechanism and pathway of this transformation, as well as the fate of mineral-associated As (i.e. whether it is re-released back into the groundwater by desorption, dissolution or redox transformation) is not yet known but critically needed for modelling As cycling in contaminated environments. To address these knowledge gaps, I conducted a series of experimental geochemical studies and combined them with various laboratory- and synchrotron-based solid and liquid phase characterization methods to examine the interaction between GR sulfate (GRSO4) and As species [As(III) and As(V)]. Specifically, I performed several batch experiments under anoxic and near-neutral pH conditions to determine As-GR interaction mechanisms during GR formation and transformation. Moreover, I also quantified how these transformation reactions affect the toxicity and mobility of As species in contaminated environments. From the batch adsorption experiments, I showed that synthetic GRSO4 can adsorb up to 160 and 105 mg of As(III) and As(V) per g of solid, respectively. These adsorption capacities are among the highest reported for iron (oxyhydr)oxides that form in soils and groundwaters. Results from this study also show that As removal by GRSO4 can be inhibited by several geochemical parameters such as pH, high ionic strength, presence of co-existing inorganic ions (e.g., Mg2+, PO43-, Si) and low temperature. I also employed an integrated nano-scale solid-state characterization approach to elucidate As-GRSO4 interactions. Specifically, I combined scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray (EDX) spectroscopy together with bulk synchrotron-based X-ray techniques including high energy X-ray total scattering, pair distribution function (PDF) analysis and X-ray absorption spectroscopy (XAS). With these, I was able to directly visualize and pinpoint As binding sites at the GR surface sites and to identify the binding mechanism for both As(III) and As(V). In the case of As(III)-reacted GR, STEM-EDX maps showed that As(III) were preferentially adsorbed at the GR crystal edges, primarily as bidentate binuclear (2C) inner-sphere surface complexes based from the differential PDF and As K-edge XAS data. For the As(V)-reacted GR, As(V) was sequestered as a newly-formed As-bearing mineral phase parasymplesite and as adsorbed As(V) species at the GR edges (in 2C geometry). To assess the fate of As in subsurface environments, I studied As during GR formation and transformation to quantify As uptake and/or its potential release back into solution and the stability of GR and other Fe (oxhydr)oxide phases in this process. During the Fe2+-induced transformation of As(V)-bearing ferrihydrite, I followed the changes in aqueous behavior and speciation of As, as well as the changes in composition of the Fe mineral phases, as a function of varying Fe2+(aq)/Fe(III)solid ratios (0.5, 1 ,2). In all the ratios tested, GRSO4, goethite and lepidocrocite formed in the early stages of transformation (≤ 2h). However, at low ratios (〈2), the initially formed GRSo4 and/or lepidocrocite disappeared as the reaction progressed, leaving goethite and unreacted ferrihydrite after 24 h. At an Fe2+(aq)/Fe(III)solid ratio of 2, GRSO4 was formed and remained in the solids until the end of the 24-h transformation, with goethite and unreacted ferrihydrite. The initial As(V) was partially reduced to As(III) by the surface-associated Fe2+-GT redox couple, and extent of reduction increased from 34 to 44% as Fe2+(aq)/Fe(III)solid ratios increased. Despite this reduction to the more mobile and more toxic As(III) species, no significant As release was observed during the mineral transformation reactions. Finally, I tested the long-term stability and reactivity of GR by aging synthetic GRSO4 in pristine and As-spiked natural groundwater at ambient (25 °C) and low (4 °C) temperatures. The spiked As in the groundwater was completely removed after 120 days at 25 °C while the removal rate was ~2 times slower at 4 °C with only ~66% As removal after 120 days. On the other hand, the stability of synthetic GRSO4 in groundwater was strongly affected by the presence of adsorbed As species and temperature. At ambient temperature, the initial GRSO4 aged in As-free groundwater was converted to GRCO3 by ion exchange within a few days and both GR phases eventually transformed to magnetite after 120 days. Remarkably, both the addition of As species in groundwater and lowering the temperature increased long-term GRSO4 stability through the inhibition of (a) ion exchange in the GRSO4 interlayer (i.e., slower conversion to GRCO3) and (b) transformation of GR to magnetite. Moreover, a synergistic stabilization effect was observed with both As addition and low temperature, significantly enhancing GR stability up to a year. Overall, the work presented in this thesis clearly emphasizes the potential role of GR phases in controlling the mobility and toxicity of As species in subsurface environments. Specifically, I contributed to the fundamental understanding of the reactions involving As(III) and As(V) at GR surfaces, elucidating the relevant binding mechanisms and visualizing specific binding sites of immobilized As species. This work also identified critical geochemical factors that affect As removal and GR formation and transformation under anoxic and circum-neutral pH conditions. More importantly, I was able to show the enhanced long-term stability of GR in natural groundwaters and its prolonged reactivity for As sequestration.

Description: The dithiol functionalized UiO-66-(SH)2 is developed as an efficient adsorbent for the removal of mercury in aqueous media. Important parameters for the application of MOFs in real-life circumstances include: stability and recyclability of the adsorbents, selectivity for the targeted Hg species in the presence of much higher concentrations of interfering species, and ability to purify wastewater below international environmental limits within a short time. We show that UiO-66-(SH)2 meets all these criteria.

Description: This dataset contains petrophysical, geochemical, and mineralogical data from a drilling core from the Coastal Cordillera, Chile. The drilling campaign in the semi-arid field site Reserve Santa Gracia was conducted in the framework of the “EarthShape” project (DFG SPP1803) to study deep weathering along a climate gradient. Previous studies in this area found that the weathering front is located much deeper than expected (Oeser et al., 2018). To explore the weathering profile and the depth of the weathering front, we performed various geochemical, petrophysical, and mineralogical analyses. The drilling campaign was conducted in March and April 2019, using the wireline drilling method with a standard industry truck-mounted PQ3-sized (85 mm core diameter, 123 mm hole diameter) rotary drilling rig (Sondajes Araos E.I.R.L.). A detailed description of the drilling activities is given in Krone et al. (2021). The retrieved core runs with a maximum length of 1.5 m were drilled using potable water, with added contamination control tracer for further microbiological analyses of the rock. As basis for our detailed study of deep weathering we determined the porosity, density, specific surface area, elemental composition, mineralogical composition, Fe oxidation, and the degree of weathering from chemical depletion, volumetric strain, and the weathering rate using the in situ cosmogenic nuclide beryllium-10 (10Be).

Description: Hybrid simulations of tail dynamics created with the Auburn Global Hybrid Code in 3-D (ANGIE3D) suggest that tail flows caused by reconnection events are closely related to the dynamics of Alfvén waves propagating from the magnetotail to the ionosphere. To understand the dynamical coupling process described by the simulations, we consider a simulated time series of plasma sheet structures associated with tail flows. As these structures drift inward, they appear to cause responses in the Poynting flux into the ionosphere. We utilize transfer entropy to identify causal, non-linear relationships between the tail flows and the Poynting flux into the ionosphere. We present 2-D and 3-D plots showing these relationships over time and the locations at which they occur. Results suggest that flows in the plasma sheet are the primary driver of the Poynting flux, which is consistent with expectations. They also illustrate the behaviors and relative locations of simulated structures on small and large timescales. This work demonstrates how system science tools such as transfer entropy can be used in conjunction with complex simulations to describe the underlying system dynamics and provide a framework for understanding the interrelated components, functions, and causalities in the system.

Description: In recent decades, the Mar Menor coastal lagoon has experienced a significant deterioration in the quality of its waters. The first source is the intensive agriculture in its watershed, with poor or non-application of soil conservation measures and excessive nitrogenous fertilizers. The second source are the abandoned open-pit mining zones.The aim of this study is, on one hand, to estimate the current nitrogen and sediment inputs to the lagoon and, in the other hand, to evaluate the impact of different control measures in order to select and prioritize the most effective ones. In this way, it will be possible to improve the ecological status of the lagoon. The distributed eco-hydrological model TETIS was used for these two objectives, activating the sediment, nitrogen and crop modules. The model was implemented with a spatial discretization was 5 m at daily time step.The evaluated measures are: reforestation of the mineral extraction zone with coniferous, use of support practices like hedgerows and contouring, adjustment of the applied fertilizer, zones where irrigated intensive crops are replaced by olive trees, shrubs and terracing, and finally, sediment retention ponds.Reforestation and terracing are crucial to reduce the sediment yield and the high erosion rates. Support practices and crop replacements shows a significant reduction in the case of the nitrogen associated to the runoff (water and sediments) which discharges directly into the lagoon. Finally, fertilizer adjustment is the more effective measure to reduce the nitrogen input to runoff and percolation.

Description: The Eddy Driven Jet (EDJ) is a major driver of extreme weather events occurring in the mid-latitudes in the Northern Hemisphere. A ubiquitous approach to quantifying the variability of the North Atlantic EDJ, is to locate the position of the maximum zonal wind over the North Atlantic sector. This identifies three ‘regimes’ of the jet representing a Southern, Northern and Central jet position.However, the process of zonal averaging leads to smoothing of distinct features, such as the tilted structure of the jet, seen in the winter climatology.In this work we propose a new feature-based method to diagnose the North Atlantic EDJ and its variability, based on 2-D maps of the low-level zonal wind field. We identify jet ‘objects’ based on contours of a minimum zonal wind threshold. By calculating moments of the objects, we can compute the jet latitude, tilt, intensity, and size. We show this method characterizes the North Atlantic jet structure more accurately and more robustly than the jet latitude index. We discuss insights into the morphology of the jet, brought to light by this new method. Most significantly, the distribution of jet latitudes shows a unimodal distribution rather than a trimodal structure, casting doubt on earlier interpretations of regime behavior in the North Atlantic EDJ. We further examine relationships between teleconnections and EOF-based circulation regimes with the jet morphology. Our approach provides a new, insightful diagnostic for EDJ dynamics.

Description: The fundamental processes of nucleation and crystallization are widely observed in systems relevant to material synthesis and biomineralization; yet most often, their mechanism remains unclear. In this study, we unravel the discrete stages of nucleation and crystallization of Fe3(PO4)2·8H2O (vivianite). We experimentally monitored the formation and transformation from ions to solid products by employing correlated, time-resolved in situ and ex situ approaches. We show that vivianite crystallization occurs in distinct stages via a transient amorphous precursor phase. The metastable amorphous ferrous phosphate (AFEP) intermediate could be isolated and stabilized. We resolved the differences in bonding environments, structure, and symmetric changes of the Fe site during the transformation of AFEP to crystalline vivianite through synchrotron X-ray absorption spectroscopy at the Fe K-edge. This intermediate AFEP phase has a lower water content and less distorted local symmetry, compared to the crystalline end product vivianite. Our combined results indicate that a nonclassical, hydration-induced nucleation and transformation driven by the incorporation and rearrangement of water molecules and ions (Fe2+ and PO43–) within the AFEP is the dominating mechanism of vivianite formation at moderately high to low vivianite supersaturations (saturation index ≤ 10.19). We offer fundamental insights into the aqueous, amorphous-to-crystalline transformations in the Fe2+–PO4 system and highlight the different attributes of the AFEP, compared to its crystalline counterpart.