This study compared the acquisition and maintenance of an Augmentative and Alternative device (iPad application, LAMP), and American Sign Language when teaching a 6th-grade student with an intellectual and developmental disability (IDD) and limited functional vocal verbal speech to make a request. A single-case alternating treatment design was applied to compare the acquisition rate between the two strategies. The system of least prompts was used to teach the student how to perform the request using the AAC device and ASL (American Sign Language). Results showed the student required fewer sessions to reach mastery when making a request using the AAC device. This study showed the system of least prompts paired with AAC was an effective and efficient strategy for the acquisition of a targeted communication request. This study provides additional evidence of an effective strategy that could be used when identifying a priority communication system for learners with limited functional speech and IDD.

As trocas complexas de água salgada, água subterrânea e água de superfície que ocorrem na região costeira afetam diretamente os ciclos biogeoquímicos globais e a aplicação de traçadores isotópicos, dentre eles radionuclídeos naturais das séries radioativas do U e do Th, se apresenta como uma ferramenta poderosa para se rastrear fontes e sumidouros de elementos-traço e nutrientes nestes ecossistemas. O comportamento único do Ra utilizado para estimar a contribuição destes fluxos é observado no estuário subterrâneo, uma zona de mistura entre a água doce subterrânea e a água salgada nos aqüíferos costeiros. Nas séries naturais de decaimento radioativo do U e do Th há quatro isótopos naturais de Ra: 223Ra (t1/2 = 11,4 d), 224Ra (t1/2 = 3,7 d), 228Ra (t1/2 = 5,7 a) e 226Ra (t1/2 = 1.600 a). As meias-vidas destes isótopos correspondem bem com a duração de muitos processos costeiros. Todos estes isótopos derivam do decaimento de um isótopo de Th precursor, que está fortemente ligado ao material particulado. Devido ao Ra ser mobilizado no ambiente marinho, os sedimentos constituem uma fonte contínua dos isótopos de Ra para as águas estuarinas em taxas estabelecidas por suas constantes de decaimento. As atividades dos isótopos de Th nos sedimentos e o coeficiente de distribuição do Ra entre os sedimentos e a água, determinam a entrada potencial de cada isótopo de Ra para um dado ambiente aquático. Como o 228Ra é regenerado mais rapidamente do que o 226Ra, estuários com altas taxas de atividade 228Ra/226Ra na água devem ter um alto grau de troca com os sedimentos na região costeira ou com a água subterrânea drenando próximo a ela. Esta informação é útil para elucidar a contribuição de sistemas estuarinos para a troca de elementos-traço, N, P e C na zona de mistura. As funções fonte combinadas para o Ra na área costeira incluem a sua entrada a partir dos rios nas formas dissolvida e particulada, das suas concentrações dissolvidas no oceano, da dessorção dos sedimentos costeiros e da água subterrânea. A importância relativa de cada uma destas fontes é geralmente uma função da hidrogeologia específica de cada local e do ambiente no qual as amostras foram coletadas em relação ao gradiente de salinidade (extensão da mistura de água doce/ água salgada). Desta forma, os isótopos de Ra fornecem informações fundamentais a respeito da interação dos sedimentos, água subterrânea e águas estuarinas. Neste projeto, a distribuição de isótopos naturais de Ra foi estudada em amostras de águas de superfície, subterrâneas e estuarinas coletadas nas estações seca e chuvosa (2009 - 2010) na região do Vale do Ribeira, litoral sul do Estado de São Paulo. O inventário permitiu utilizá-los como traçadores de descargas fluvial e subterrânea para o complexo estuarino-lagunar de Cananéia/Iguape. As trocas complexas da água subterrânea/água de superfície na bacia do Rio Ribeira de Iguape, assim como os fluxos de vários constituintes para o complexo estuarino-lagunar de Cananéia/Iguape ainda são ainda componentes pouco conhecidos nos balanços hídrico e de materiais no cenário de interesse. Os resultados obtidos mostraram que há uma predominância do isótopo de 228Ra em todas as amostras analisadas, embora as concentrações detectadas tanto no Alto Vale do Ribeira como ao longo da Planície Costeira indiquem que estes resultados representam níveis naturais de fundo, denotando pequena ou mínima intervenção humana. Nas amostras coletadas ao longo do Rio Ribeira de Iguape e nos estuários de Cananéia e de Iguape, as maiores concentrações dos isótopos de Ra foram observadas nas águas de fundo, indicando a difusão do 228Ra dos sedimentos recentemente depositados como uma fonte potencial das concentrações aumentadas deste isótopo em relação aos demais. As concentrações dos isótopos de meias-vidas curtas foram negligenciáveis, em sua maior parte menores que o limite inferior de detecção do método. Os fluxos de Ra para o sistema na Barra de Cananéia é fortemente influenciado pelas correntes e canais de maré, que modulam o aumento ou diminuição das concentrações de Ra em resposta direta ao respectivo aumento e diminuição da salinidade das águas. No estuário de Iguape e nas estações hidroquímicas realizadas no Rio Ribeira do Iguape observou-se uma correlação linear entre a quantidade de material em suspensão (MES) e o aumento da concentração de 228Ra. Quando se avaliam qualitativamente as diferenças entre o comportamento dos dois isótopos de Ra de meias-vidas longas, as concentrações de 226Ra não apresentaram distribuição idêntica aquelas do 228Ra. Isto demonstra um aporte negligenciável advectivo das águas intersticiais dos sedimentos e subterrâneas para o cenário de interesse. Os fluxos dominantes de elementos-traço, radionuclídeos e nutrientes tem suas maiores fontes centradas no compartimento fluvial, sedimentos e material em suspensão. / The complex exchange of fluvial, subsurface and seawater within a coastal area directly affects global biogeochemical cycles and the application of isotopic tracers, mainly natural radionuclides from U and Th series, is a powerful tool to track sources and sinks of trace elements and nutrients to this systems. The unique Ra signature applied to quantify the contribution of such fluxes is acquired within the subterranean estuary, a mixing zone between fresh groundwater and seawater in coastal aquifers. In the U and Th natural radioactive decay series there are four radium isotopes: 223Ra (t1/2 = 11.4 d), 224Ra (t1/2 = 3.7 d), 228Ra (t1/2 = 5.7 y) and 226Ra (t1/2 = 1,600 y). Their wide range in half-lives corresponds well with the duration of many coastal processes. All these Ra isotopes derive from decay of Th parents, which are tightly bound to particles. Because Ra is mobilized in the marine environment, sediments provide a continuous source of Ra isotopes to estuarine waters at rates set by its decay constants. The Th isotope activities in the sediments and the distribution coefficient of Ra between the sediments and water determine the potential input of each Ra isotope to the water. Because 228Ra is regenerated much faster than 226Ra, estuaries with high 228Ra/ 226Ra activity ratios in the water must have a high degree of exchange with sediments on the sea bed or with groundwater draining nearby. This information is useful to elucidate the contribution of estuarine systems to the exchange of trace elements, N, P and C in the mixing zone. The combined source functions for Ra in a coastal area include riverine particulates/ dissolved input, oceanic dissolved concentrations, input from sediments and groundwater. The relative significance of each of these sources is usually a function of the site-specific hydrogeology and where the samples are taken relative to the salinity gradient (extent of freshwater/saltwater mixing). Thus, the Ra isotopes provide fundamental information on the interaction of sediments, groundwater and estuarine waters. In this project, the distribution of natural Ra isotopes was studied in surface, groundwater and estuarine water samples collected from dry and wet seasons (2009 2010) campaigns performed in Ribeira Valley, Southern São Paulo State. The inventory allowed the application of Ra isotopes as tracers of fluvial and groundwater discharges to the Cananéia-Iguape estuarine complex. The exchange of groundwater/ surface water in Ribeira do Iguape River basin and related fluxes of several constituents for the Cananéia-Iguape estuarine complex mass balance is still not very well known. The results obtained in this research work evidenced that there is a prevalence of 228Ra isotope in all the set of samples analyzed. However, the activity concentrations of Ra isotopes determined from Higher Ribeira Valley through the Southern Coastal Plain of São Paulo are representative of natural background levels, showing low or minimal human intervention. In the set of samples collected along Ribeira do Iguape River, Cananéia and Iguape outlets, the higher concentrations of Ra were observed in bottom waters, indicating the diffusion of 228Ra from sediments recently deposited as a potential source of the increased concentrations of this isotope when compared with others. The activity concentrations of the short-lived Ra isotopes were negligible, lower than the limit of the detection. Fluxes of Ra for Cananéia outlet are strongly influenced by tidal oscillations, which modulate the increase and decrease of Ra concentrations in response of the respective increase and decrease of waters salinity. In Iguape outlet and in hydrochemical stations performed along Ribeira do Iguape River it was observed a linear relationship between the amount of suspended matter and the increase of 228Ra activity concentration. When we evaluate qualitatively the differences in behavior of both long-lived Ra isotopes, the concentrations of 226Ra have not shown similar distribution to 228Ra. This demonstrates negligible contribution from advective porewaters and groundwater to the studied scenario. Dominant fluxes of trace-elements, radionuclides and nutrients have their main sources centered on fluvial, sediments and suspended matter compartiments.

As trocas complexas de água salgada, água subterrânea e água de superfície que ocorrem na região costeira afetam diretamente os ciclos biogeoquímicos globais e a aplicação de traçadores isotópicos, dentre eles radionuclídeos naturais das séries radioativas do U e do Th, se apresenta como uma ferramenta poderosa para se rastrear fontes e sumidouros de elementos-traço e nutrientes nestes ecossistemas. O comportamento único do Ra utilizado para estimar a contribuição destes fluxos é observado no estuário subterrâneo, uma zona de mistura entre a água doce subterrânea e a água salgada nos aqüíferos costeiros. Nas séries naturais de decaimento radioativo do U e do Th há quatro isótopos naturais de Ra: 223Ra (t1/2 = 11,4 d), 224Ra (t1/2 = 3,7 d), 228Ra (t1/2 = 5,7 a) e 226Ra (t1/2 = 1.600 a). As meias-vidas destes isótopos correspondem bem com a duração de muitos processos costeiros. Todos estes isótopos derivam do decaimento de um isótopo de Th precursor, que está fortemente ligado ao material particulado. Devido ao Ra ser mobilizado no ambiente marinho, os sedimentos constituem uma fonte contínua dos isótopos de Ra para as águas estuarinas em taxas estabelecidas por suas constantes de decaimento. As atividades dos isótopos de Th nos sedimentos e o coeficiente de distribuição do Ra entre os sedimentos e a água, determinam a entrada potencial de cada isótopo de Ra para um dado ambiente aquático. Como o 228Ra é regenerado mais rapidamente do que o 226Ra, estuários com altas taxas de atividade 228Ra/226Ra na água devem ter um alto grau de troca com os sedimentos na região costeira ou com a água subterrânea drenando próximo a ela. Esta informação é útil para elucidar a contribuição de sistemas estuarinos para a troca de elementos-traço, N, P e C na zona de mistura. As funções fonte combinadas para o Ra na área costeira incluem a sua entrada a partir dos rios nas formas dissolvida e particulada, das suas concentrações dissolvidas no oceano, da dessorção dos sedimentos costeiros e da água subterrânea. A importância relativa de cada uma destas fontes é geralmente uma função da hidrogeologia específica de cada local e do ambiente no qual as amostras foram coletadas em relação ao gradiente de salinidade (extensão da mistura de água doce/ água salgada). Desta forma, os isótopos de Ra fornecem informações fundamentais a respeito da interação dos sedimentos, água subterrânea e águas estuarinas. Neste projeto, a distribuição de isótopos naturais de Ra foi estudada em amostras de águas de superfície, subterrâneas e estuarinas coletadas nas estações seca e chuvosa (2009 - 2010) na região do Vale do Ribeira, litoral sul do Estado de São Paulo. O inventário permitiu utilizá-los como traçadores de descargas fluvial e subterrânea para o complexo estuarino-lagunar de Cananéia/Iguape. As trocas complexas da água subterrânea/água de superfície na bacia do Rio Ribeira de Iguape, assim como os fluxos de vários constituintes para o complexo estuarino-lagunar de Cananéia/Iguape ainda são ainda componentes pouco conhecidos nos balanços hídrico e de materiais no cenário de interesse. Os resultados obtidos mostraram que há uma predominância do isótopo de 228Ra em todas as amostras analisadas, embora as concentrações detectadas tanto no Alto Vale do Ribeira como ao longo da Planície Costeira indiquem que estes resultados representam níveis naturais de fundo, denotando pequena ou mínima intervenção humana. Nas amostras coletadas ao longo do Rio Ribeira de Iguape e nos estuários de Cananéia e de Iguape, as maiores concentrações dos isótopos de Ra foram observadas nas águas de fundo, indicando a difusão do 228Ra dos sedimentos recentemente depositados como uma fonte potencial das concentrações aumentadas deste isótopo em relação aos demais. As concentrações dos isótopos de meias-vidas curtas foram negligenciáveis, em sua maior parte menores que o limite inferior de detecção do método. Os fluxos de Ra para o sistema na Barra de Cananéia é fortemente influenciado pelas correntes e canais de maré, que modulam o aumento ou diminuição das concentrações de Ra em resposta direta ao respectivo aumento e diminuição da salinidade das águas. No estuário de Iguape e nas estações hidroquímicas realizadas no Rio Ribeira do Iguape observou-se uma correlação linear entre a quantidade de material em suspensão (MES) e o aumento da concentração de 228Ra. Quando se avaliam qualitativamente as diferenças entre o comportamento dos dois isótopos de Ra de meias-vidas longas, as concentrações de 226Ra não apresentaram distribuição idêntica aquelas do 228Ra. Isto demonstra um aporte negligenciável advectivo das águas intersticiais dos sedimentos e subterrâneas para o cenário de interesse. Os fluxos dominantes de elementos-traço, radionuclídeos e nutrientes tem suas maiores fontes centradas no compartimento fluvial, sedimentos e material em suspensão. / The complex exchange of fluvial, subsurface and seawater within a coastal area directly affects global biogeochemical cycles and the application of isotopic tracers, mainly natural radionuclides from U and Th series, is a powerful tool to track sources and sinks of trace elements and nutrients to this systems. The unique Ra signature applied to quantify the contribution of such fluxes is acquired within the subterranean estuary, a mixing zone between fresh groundwater and seawater in coastal aquifers. In the U and Th natural radioactive decay series there are four radium isotopes: 223Ra (t1/2 = 11.4 d), 224Ra (t1/2 = 3.7 d), 228Ra (t1/2 = 5.7 y) and 226Ra (t1/2 = 1,600 y). Their wide range in half-lives corresponds well with the duration of many coastal processes. All these Ra isotopes derive from decay of Th parents, which are tightly bound to particles. Because Ra is mobilized in the marine environment, sediments provide a continuous source of Ra isotopes to estuarine waters at rates set by its decay constants. The Th isotope activities in the sediments and the distribution coefficient of Ra between the sediments and water determine the potential input of each Ra isotope to the water. Because 228Ra is regenerated much faster than 226Ra, estuaries with high 228Ra/ 226Ra activity ratios in the water must have a high degree of exchange with sediments on the sea bed or with groundwater draining nearby. This information is useful to elucidate the contribution of estuarine systems to the exchange of trace elements, N, P and C in the mixing zone. The combined source functions for Ra in a coastal area include riverine particulates/ dissolved input, oceanic dissolved concentrations, input from sediments and groundwater. The relative significance of each of these sources is usually a function of the site-specific hydrogeology and where the samples are taken relative to the salinity gradient (extent of freshwater/saltwater mixing). Thus, the Ra isotopes provide fundamental information on the interaction of sediments, groundwater and estuarine waters. In this project, the distribution of natural Ra isotopes was studied in surface, groundwater and estuarine water samples collected from dry and wet seasons (2009 2010) campaigns performed in Ribeira Valley, Southern São Paulo State. The inventory allowed the application of Ra isotopes as tracers of fluvial and groundwater discharges to the Cananéia-Iguape estuarine complex. The exchange of groundwater/ surface water in Ribeira do Iguape River basin and related fluxes of several constituents for the Cananéia-Iguape estuarine complex mass balance is still not very well known. The results obtained in this research work evidenced that there is a prevalence of 228Ra isotope in all the set of samples analyzed. However, the activity concentrations of Ra isotopes determined from Higher Ribeira Valley through the Southern Coastal Plain of São Paulo are representative of natural background levels, showing low or minimal human intervention. In the set of samples collected along Ribeira do Iguape River, Cananéia and Iguape outlets, the higher concentrations of Ra were observed in bottom waters, indicating the diffusion of 228Ra from sediments recently deposited as a potential source of the increased concentrations of this isotope when compared with others. The activity concentrations of the short-lived Ra isotopes were negligible, lower than the limit of the detection. Fluxes of Ra for Cananéia outlet are strongly influenced by tidal oscillations, which modulate the increase and decrease of Ra concentrations in response of the respective increase and decrease of waters salinity. In Iguape outlet and in hydrochemical stations performed along Ribeira do Iguape River it was observed a linear relationship between the amount of suspended matter and the increase of 228Ra activity concentration. When we evaluate qualitatively the differences in behavior of both long-lived Ra isotopes, the concentrations of 226Ra have not shown similar distribution to 228Ra. This demonstrates negligible contribution from advective porewaters and groundwater to the studied scenario. Dominant fluxes of trace-elements, radionuclides and nutrients have their main sources centered on fluvial, sediments and suspended matter compartiments.

A preliminary study shows that Submarine Groundwater Discharge (SGD) exists around Taiwan even though groundwater overdrawing is serious. Only five of the 20 sites studied did not record any SGD signal. Two nearly fresh SGD samples were obtained, providing strong and direct evidence for the existence of SGD in Taiwan. SGD is the submarine seepage of all fluids from coastal sediments into the overlying coastal areas. It has been well documented that SGD may contribute much nutrients to the coasts (Burnett et al.,2001, 2003; Church, 1996; Taniguchi et al., 2002; Zhang and Satake, 2002). Because of its difficulty in measurement, there are few reports on the characteristics of groundwater seepage, such as the flow rate and the water chemistry. In Taiwan, the only report was published in the Japanese journal Geochemistry (Chen et al. , 2005 ). In this study, samples were collected monthly from May, 2004 to June, 2006 at Xiziwan and Caishan in Kaohsiung. A flux chamber was also used in the observation of the SGD seepage rates. Further, samples were collected from 20 different places around Taiwan. The SGD collecting device, the SGD-Flux chamber and the Lee type seepage meter (Zhang et al., 2005) were used in this study, the latter being the first time used to explore the SGD flux in Taiwan. Salinity, dissolved oxygen saturation (%), nutrients (NO3, NO2, PO4, SiO2, NH3), total alkalinity, pH and major ions were analyzed. We averaged all seepage rate data at Xiziwan and Caishan to estimated the SGD seepage rate at about 1.32¡Ó1.57 L/m2/hr. The average concentrations of inorganic nitrogen (NO3+NO2+NH3), PO4 and SiO2 are, respectively, 48.6¡Ó86.3 (n=85), 0.78¡Ó1.26 (n=110) and 55.1¡Ó39.8

The discharge of groundwater into surface water bodies is a hidden, but significant pathway for the input of water and matter into lakes, rivers, estuaries and the coastal sea. Since groundwater is most often characterized by higher levels of nutrients or heavy metals, its discharge has often a crucial effect on the surface water body´s chemistry and the ecosystem health as well as on the related ecosystem service supply. For instance, groundwater-derived nutrient inputs are essential to fuel primary productivity, but if critical thresholds are exceeded groundwater-derived nutrient inputs can cause eutrophication, which may trigger harmful algal blooms or the creation of oxygen minimum zones – a serious threat to aquatic life. This thesis focuses on quantifying submarine and lacustrine groundwater discharge by applying environmental tracer based methods with emphasis on radionuclide (radon and radium isotopes) and stable water isotope (δ18O, δ2H) techniques. These tracers are suitable for determining groundwater discharge as they show distinct concentration and isotope ratio gradients between groundwater and the receiving surface water. Four studies are presented in this thesis: (1) The quantification of the response delay of the mobile radon detector RAD7 applied for radon-in-water mapping. The response delay of the mobile radon-in-air detector RAD7 is determined for two detection set-ups (radon extraction via RADaqua and via a membrane module) as well as for a range of water flow rates. For the membrane module the response delay is less pronounced compared to the RADaqua. For instance, at a water flow rate of 1 l min-1 the peaks of the instruments recordings lag behind the radon-in-water concentrations by ~10 min for the membrane module and by ~18 min for the RADaqua. Further, it was demonstrated that faster water flow rates decrease the response delay. An algorithm is presented that allows the inverse calculation of radon-in-water concentrations from RAD7 records for the described detection set-ups and water flow rates. Thus, it allows a more precise localization of radon-in-water anomalies and, consequently a more precise localization of groundwater discharge areas. (2) Determination of submarine groundwater discharge into a large coastal bay (False Bay, South Africa) SGD consists generally of two components: (a) fresh terrestrial SGD (FSGD) driven by the inland hydraulic gradient and (b) seawater re-circulation (RSGD) through the coastal aquifer driven by seaward effects such as tidal pumping. A bay-wide radon mapping resulted in identification of a SGD site, where subsequently detailed investigations were conducted. At this SGD site a salt and a radon mass balance were applied consecutively for determining FSGD and total SGD, respectively. RSGD was inferred from the difference between FSGD and total SGD. For the radon mass balance, new approaches for calculating the radon degassing and mixing loss were proposed. The tracer mass balance revealed median FSGD of 2,300 m³ d-1 or 0.9 m³ d-1 per m coastline and median RSGD of 6,600 m³ d-1 or 2.7 m³ d-1 per m coastline. The FSGD rate was validated using (a) a hydrological model for calculating the groundwater recharge rate and (b) a groundwater flow model for delineating the subsurficial FSGD capture zone. This validation supported the tracer based findings. The relevance of this study is foremost the presentation of new methodological approaches regarding the radon mass balance as well as the validation of FSGD under consideration of hydrological and hydrogeological information. (3) Differentiation of fresh and re-circulated submarine groundwater discharge in an estuary (Knysna Estuary, South Africa) Knysna Estuary is a more complex system than False Bay since besides seawater, FSGD and RSGD also river water mixes within the estuary. Both FSGD and RSGD were differentiated by applying a mixing analysis of the estuary water. For this purpose, an end-member mixing analysis (EMMA) was conducted that simultaneously utilizes radon and salinity time series of estuary water to determine fractions of the end-members seawater, river water, FSGD and RSGD. End-member mixing ratio uncertainty was quantified by stochastic modelling (Monte Carlo simulation) under consideration of end-member characterization uncertainty. Results revealed highest FSGD and RSGD fractions in the estuary during peak low tide. Median fractions of FSGD and RSGD were 0.2 % and 0.8 % of the estuary water near the mouth over a 24 h time-series. In combi-nation with a radon mass balance median FSGD of 46,000 m³ d-1 and median RSGD of 150,000 m³ d-1 were determined. By comparison to other sources, this implies that the SGD is a significant source of dissolved inorganic nitrogen (DIN) fluxes into the estuary. This study demonstrates the ability of EMMA to determine end-member fractions in a four end-member system under consideration of end-member uncertainty. Further, the importance of SGD for the water and DIN budget of Knysna Estuary was shown. (4) Quantification of groundwater discharge and water residence time into a groundwa-ter-fed lake (Lake Ammelshainer See, Germany). The presented approach utilizes the stable isotopes of water (δ18O, δ2H) and radon for determining long-term average and short-term trends in groundwater discharge rates. The calculations were based on measurements of isotope inventories of lake and groundwater in combination with climatic and isotopic monitoring data (in precipita-tion). The results from steady-state annual isotope mass balances for both δ18O and δ2H are consistent and reveal an overall long-term average groundwater discharge that ranges from 2,800 to 3,350 m³ d-1. These findings were supported by the good agree-ment of the simulated annual cycles of δ18O and δ2H lake inventories utilizing the de-termined groundwater discharge rates with the observed lake isotope inventories. However, groundwater discharge rates derived from radon mass balances were signifi-cantly lower, which might indicate a distinct seasonal variability of the groundwater discharge rate. This application shows the benefits and limitations of combining δ18O/δ2H and radon isotope mass balances for the quantification of groundwater con-nectivity of lakes based on a relatively small amount of field data accompanied by good quality and comprehensive long-term meteorological and isotopic data (precipitation). This thesis presents important methodological achievements with respect to radon and stable water isotope mass balances, uncertainty quantification, geochemical differentia-tion between FSGD and RSGD and validation of FSGD. Further, first SGD estimates are reported for False Bay and Knysna Estuary in South Africa. / Der Austritt von Grundwasser in Oberflächengewässer stellt einen unsichtbaren Ein-tragspfad von Wasser und Stoffen in Seen, Flüsse, Ästuare und das küstennahe Meer dar. Die Konzentrationen vieler Stoffe wie beispielsweise von Nährstoffen und Schwermetallen ist im Grundwasser im Allgemeinen signifikant höher als in Oberflächengewässern. Daher können selbst volumetrisch verhältnismäßig kleine Grundwasseraustritte entscheidenden Einfluss auf Wasserchemie und den Gesundheitszustand des aquatischen Ökosystems haben, womit Auswirkungen auf die Bereitstellung von Ökosystemleistungen verbunden sein können. Beispielsweise sind grundwasserbürtige Nährstoffeinträge eine entscheidende Steuergröße für die Primärproduktivität. Überschreiten diese grundwasserbürtigen Nährstoffeinträge jedoch einen Schwellenwert, kann es zur Eutrophierung des Oberflächengewässers kommen. Dies wiederum kann toxische Algenblüten oder die Entstehung von Sauerstoffminimumzonen zur Folge haben und das aquatische Leben bedrohen. Diese Dissertation beschäftigt sich mit Methoden zur Quantifizierung von Grundwas-sereinträgen in den küstennahen Ozean, Ästuare und in Seen. Dabei stützt sich diese Arbeit primär auf Umwelttracer, vor allem auf Radionuklide (Radon- und Radium-Isotope) sowie die stabilen Isotope des Wassers (δ18O, δ2H). Diese Umwelttracer sind für die untersuchten Systeme in besonderer Weise geeignet, da zwischen Grundwasser und Oberflächenwasser ein ausgeprägter Gradient hinsichtlich Konzentration bzw. Isotopensignatur besteht. Vier Einzelstudien stellen den Kern dieser Arbeit dar: (1) Die Quantifizierung der Antwortverzögerung des mobilen Radon-Detektors RAD7, an-gewendet für die Radon-in-Wasser-Kartierung. Die Antwortverzögerung des mobilen Radon-in-Luft-Detektors RAD7 wurde für zwei Messanordnungen (Radonextraktion via RADaqua und via Membranmodul) sowie für einen Bereich von Wasserdurchflussraten bestimmt. Für die Radonextraktion via RADaqua ist die Antwortverzögerung stärker ausgeprägt als für das Membranmodul. Bei einer Wasserdurchflussrate von 1 l min-1 treten die Peaks der aufgezeichneten Werte ~10 min nach den Radon-in-Wasser Peaks auf, während die Verzögerung bei Radonextraktion via RADaqua ~18 min beträgt. Weiterhin wurde eine Reduktion der Antwortverzögerung mit zunehmenden Wasserdurchflussraten beobachtet. Der vorgestellte Algorithmus ermöglicht in Kombination mit den berechneten Radontransfer-Koeffizienten die inverse Modellierung der Radon-in-Wasser-Konzentrationen, basierend auf den RAD7-Messwerten. Dies ermöglicht beispielsweise eine genauere Lokalisierung von räumlichen Radon-in-Wasser Anomalien und folglich eine präzisere Bestimmung von Grundwasseraustrittsstellen. (2) Quantifizierung untermeerischer Grundwasseraustritte in eine große Meeresbucht (False Bay, Südafrika) Untermeerische Grundwasseraustritte (“Submarine Groundwater Discharge” – SGD) bestehen aus zwei Komponenten: (a) Süßwasser-SGD (“Fresh SGD” – FSGD) angetrieben durch den meerwärtsgerichteten hydraulischen Gradienten, und (b) re-zirkuliertem SGD („re-circulated SGD“ – RSGD), verursacht durch Prozesse wie gezeitengesteuerte Infiltration von Meerwasser in den Aquifer. Eine Radon-Kartierung entlang der gesamten Küstenlinie der Bucht führte zur Lokalisierung von SGD, woraufhin dort vertiefende Untersuchungen durchgeführt wurden. In diesem Bilanzgebiet wurden eine Salz- und eine Radon-Massenbilanz durchgeführt, um FSGD bzw. Gesamt-SGD zu bestimmen. RSGD wurde aus der Differenz von FSGD und SGD abgleitet. Für die Radon-Massenbilanz wurden neue Ansätze für die Berechnung der Radon-Entgasung in die Atmosphäre und des Radon-Mischungsverlustes mit küstenfernerem Wasser präsentiert. Die Tracer-Massenbilanzen ergaben einen FSGD-Median von 2.300 m³ d-1 bzw. 0,9 m³ d-1 pro Meter Küstenlinie und einen RSGD-Median von 6.600 m³ d-1 bzw. 2,7 m³ d-1 pro Meter Küstenlinie. Die FSGD-Rate wurde mit Hilfe eines hydrologischen Modells zur Abschätzung der Grundwasserneubildungsrate und eines Grundwasserströmungsmodells zur Abgrenzung des unterirdischen Einzugsgebiets des Bilanzraums bestimmt. Diese unabhängige Methode bestätigte die Tracer-basierten Ergebnisse. Die Bedeutung dieser Studie besteht zuvorderst in der Vorstellung neuer methodischer Ansätze bei der Radon-Massenbilanzierung sowie in der Validierung von FSGD unter Berücksichtigung hydrologischer und hydrogeologischer Daten. (3) Unterscheidung von FSGD und RSGD in einem Ästuar (Knysna Ästuar, Südafrika). Das Knysna-Ästuar ist hinsichtlich der Bestimmung von SGD im Vergleich zur False Bay ein komplexeres System, da sich neben Meerwasser, FSGD und RSGD auch Flusswasser in signifikanten Mengen im Ästuar mischt. FSGD- und RSGD-Anteile wurden anhand der chemischen Zusammensetzung des Ästuarwassers unterschieden. Für diesen Zweck wurde eine End-Member-Mischungsanalyse (EMMA) auf Grundlage von Radon- und Salinitätszeitreihen des Ästuarwassers durchgeführt. Durch ein Optimierungsverfahren wurde die Mischung der End-member Meerwasser, Flusswasser, FSGD und RSGD für jeden Zeitschritt mit dem Ziel der bestmöglichen Übereinstimmung mit den gemessenen Radon- und Salinitätszeitreihen bestimmt. Die Unsicherheit in der Bestimmung der End-member-Anteile wurde durch stochastische Modellierung (Monte-Carlo-Simulation) quantifiziert. Die höchsten Anteile von FSGD und RSGD traten bei Niedrigwasser auf. Die mittleren Anteile von FSGD und RSGD betrugen in der Nähe der Ästuarmündung 0,2 % und 0,8 % während einer 24-stündigen Zeitreihenmessung. Diese Informationen führten in Kombination mit einer Radon-Massenbilanz zur Bestimmung eines mittleren FSGD von 46.000 m³ d-1 sowie eines mittleren RSGD von 150.000 m³ d-1. Diese Ergebnisse implizieren unter Einbeziehung weiterer Daten, dass SGD ein bedeutender Pfad für den Eintrag von gelöstem anorganischem Stickstoff (DIN) in das Knysna-Ästuar darstellt. Diese Studie zeigt das Potenzial einer EMMA für die Bestimmung der Anteile von vier End-membern unter Nutzung von zwei gemessenen Variablen und unter Berücksichtigung der End-member-Unsicherheit. Außerdem wurde die Bedeutung von SGD für das Wasser- und DIN-Budget des Knysna-Ästuars aufgezeigt. (4) Quantifizierung von Grundwasseraustrittsrate und Wasserverweilzeit eines grundwas-sergespeisten Sees (Ammelshainer See, Deutschland). Der vorgestellte Ansatz nutzt die stabilen Isotope des Wassers (δ18O, δ2H) und von Ra-don für die Bestimmung des mittleren langfristigen sowie der aktuellen Grundwas-seraustrittsrate. Die Berechnungen beruhen auf Abschätzungen des Isotopeninventars anhand von Feldmessungen, der Isotopensignatur des Grundwassers sowie ergänzen-den Klima- und Isotopen-Daten (Niederschlag). Die Ergebnisse einer stationären Isoto-pen-Massenbilanz für δ18O und δ2H sind übereinstimmend und ergaben einen langfristigen mittleren Grundwasseraustritt von 2.800 bis 3.350 m³ d-1. Dieses Ergebnis wurde für die Modellierung des jährlichen Zyklus des Isotopeninventars im See benutzt, welches mit den gemessenen Isotopenwerten konsistent ist. Die auf Grundlage einer Radon-Massenbilanz abgeleiteten aktuellen Grundwasserzutrittsraten lagen im Gegensatz dazu deutlich niedriger, was jedoch nicht notwendigerweise einen Widerspruch darstellen muss, sondern vielmehr ein Hinweis auf eine möglicherweise ausgeprägte saisonale Variabilität des Grundwasseraustritts darstellen kann. Diese Studie zeigt Möglichkeiten und Grenzen der Anwendung von einer Kombination aus δ18O/δ2H- und Radon-Massenbilanzen für die Bestimmung der Grundwasseranbindung von Seen mit einem vergleichsweise geringen Messaufwand unter Nutzung qualitativ hochwertiger und umfangreicher Klima-und Isotopen-Daten (Niederschlag). Diese Dissertation präsentiert wichtige methodische Fortschritte hinsichtlich der An-wendung von Radon- und stabilen Isotopen-Massenbilanzen, der Quantifizierung von Unsicherheit, der Unterscheidung von FSGD und RSGD anhand geochemischer Daten und der Validierung von FSGD. Außerdem wurden erstmals SGD-Raten für Standorte in Südafrika (False Bay und Knysna-Ästuar) vorgestellt.

The discharge of groundwater into surface water bodies is a hidden, but significant pathway for the input of water and matter into lakes, rivers, estuaries and the coastal sea. Since groundwater is most often characterized by higher levels of nutrients or heavy metals, its discharge has often a crucial effect on the surface water body´s chemistry and the ecosystem health as well as on the related ecosystem service supply. For instance, groundwater-derived nutrient inputs are essential to fuel primary productivity, but if critical thresholds are exceeded groundwater-derived nutrient inputs can cause eutrophication, which may trigger harmful algal blooms or the creation of oxygen minimum zones – a serious threat to aquatic life. This thesis focuses on quantifying submarine and lacustrine groundwater discharge by applying environmental tracer based methods with emphasis on radionuclide (radon and radium isotopes) and stable water isotope (δ18O, δ2H) techniques. These tracers are suitable for determining groundwater discharge as they show distinct concentration and isotope ratio gradients between groundwater and the receiving surface water. Four studies are presented in this thesis: (1) The quantification of the response delay of the mobile radon detector RAD7 applied for radon-in-water mapping. The response delay of the mobile radon-in-air detector RAD7 is determined for two detection set-ups (radon extraction via RADaqua and via a membrane module) as well as for a range of water flow rates. For the membrane module the response delay is less pronounced compared to the RADaqua. For instance, at a water flow rate of 1 l min-1 the peaks of the instruments recordings lag behind the radon-in-water concentrations by ~10 min for the membrane module and by ~18 min for the RADaqua. Further, it was demonstrated that faster water flow rates decrease the response delay. An algorithm is presented that allows the inverse calculation of radon-in-water concentrations from RAD7 records for the described detection set-ups and water flow rates. Thus, it allows a more precise localization of radon-in-water anomalies and, consequently a more precise localization of groundwater discharge areas. (2) Determination of submarine groundwater discharge into a large coastal bay (False Bay, South Africa) SGD consists generally of two components: (a) fresh terrestrial SGD (FSGD) driven by the inland hydraulic gradient and (b) seawater re-circulation (RSGD) through the coastal aquifer driven by seaward effects such as tidal pumping. A bay-wide radon mapping resulted in identification of a SGD site, where subsequently detailed investigations were conducted. At this SGD site a salt and a radon mass balance were applied consecutively for determining FSGD and total SGD, respectively. RSGD was inferred from the difference between FSGD and total SGD. For the radon mass balance, new approaches for calculating the radon degassing and mixing loss were proposed. The tracer mass balance revealed median FSGD of 2,300 m³ d-1 or 0.9 m³ d-1 per m coastline and median RSGD of 6,600 m³ d-1 or 2.7 m³ d-1 per m coastline. The FSGD rate was validated using (a) a hydrological model for calculating the groundwater recharge rate and (b) a groundwater flow model for delineating the subsurficial FSGD capture zone. This validation supported the tracer based findings. The relevance of this study is foremost the presentation of new methodological approaches regarding the radon mass balance as well as the validation of FSGD under consideration of hydrological and hydrogeological information. (3) Differentiation of fresh and re-circulated submarine groundwater discharge in an estuary (Knysna Estuary, South Africa) Knysna Estuary is a more complex system than False Bay since besides seawater, FSGD and RSGD also river water mixes within the estuary. Both FSGD and RSGD were differentiated by applying a mixing analysis of the estuary water. For this purpose, an end-member mixing analysis (EMMA) was conducted that simultaneously utilizes radon and salinity time series of estuary water to determine fractions of the end-members seawater, river water, FSGD and RSGD. End-member mixing ratio uncertainty was quantified by stochastic modelling (Monte Carlo simulation) under consideration of end-member characterization uncertainty. Results revealed highest FSGD and RSGD fractions in the estuary during peak low tide. Median fractions of FSGD and RSGD were 0.2 % and 0.8 % of the estuary water near the mouth over a 24 h time-series. In combi-nation with a radon mass balance median FSGD of 46,000 m³ d-1 and median RSGD of 150,000 m³ d-1 were determined. By comparison to other sources, this implies that the SGD is a significant source of dissolved inorganic nitrogen (DIN) fluxes into the estuary. This study demonstrates the ability of EMMA to determine end-member fractions in a four end-member system under consideration of end-member uncertainty. Further, the importance of SGD for the water and DIN budget of Knysna Estuary was shown. (4) Quantification of groundwater discharge and water residence time into a groundwa-ter-fed lake (Lake Ammelshainer See, Germany). The presented approach utilizes the stable isotopes of water (δ18O, δ2H) and radon for determining long-term average and short-term trends in groundwater discharge rates. The calculations were based on measurements of isotope inventories of lake and groundwater in combination with climatic and isotopic monitoring data (in precipita-tion). The results from steady-state annual isotope mass balances for both δ18O and δ2H are consistent and reveal an overall long-term average groundwater discharge that ranges from 2,800 to 3,350 m³ d-1. These findings were supported by the good agree-ment of the simulated annual cycles of δ18O and δ2H lake inventories utilizing the de-termined groundwater discharge rates with the observed lake isotope inventories. However, groundwater discharge rates derived from radon mass balances were signifi-cantly lower, which might indicate a distinct seasonal variability of the groundwater discharge rate. This application shows the benefits and limitations of combining δ18O/δ2H and radon isotope mass balances for the quantification of groundwater con-nectivity of lakes based on a relatively small amount of field data accompanied by good quality and comprehensive long-term meteorological and isotopic data (precipitation). This thesis presents important methodological achievements with respect to radon and stable water isotope mass balances, uncertainty quantification, geochemical differentia-tion between FSGD and RSGD and validation of FSGD. Further, first SGD estimates are reported for False Bay and Knysna Estuary in South Africa. / Der Austritt von Grundwasser in Oberflächengewässer stellt einen unsichtbaren Ein-tragspfad von Wasser und Stoffen in Seen, Flüsse, Ästuare und das küstennahe Meer dar. Die Konzentrationen vieler Stoffe wie beispielsweise von Nährstoffen und Schwermetallen ist im Grundwasser im Allgemeinen signifikant höher als in Oberflächengewässern. Daher können selbst volumetrisch verhältnismäßig kleine Grundwasseraustritte entscheidenden Einfluss auf Wasserchemie und den Gesundheitszustand des aquatischen Ökosystems haben, womit Auswirkungen auf die Bereitstellung von Ökosystemleistungen verbunden sein können. Beispielsweise sind grundwasserbürtige Nährstoffeinträge eine entscheidende Steuergröße für die Primärproduktivität. Überschreiten diese grundwasserbürtigen Nährstoffeinträge jedoch einen Schwellenwert, kann es zur Eutrophierung des Oberflächengewässers kommen. Dies wiederum kann toxische Algenblüten oder die Entstehung von Sauerstoffminimumzonen zur Folge haben und das aquatische Leben bedrohen. Diese Dissertation beschäftigt sich mit Methoden zur Quantifizierung von Grundwas-sereinträgen in den küstennahen Ozean, Ästuare und in Seen. Dabei stützt sich diese Arbeit primär auf Umwelttracer, vor allem auf Radionuklide (Radon- und Radium-Isotope) sowie die stabilen Isotope des Wassers (δ18O, δ2H). Diese Umwelttracer sind für die untersuchten Systeme in besonderer Weise geeignet, da zwischen Grundwasser und Oberflächenwasser ein ausgeprägter Gradient hinsichtlich Konzentration bzw. Isotopensignatur besteht. Vier Einzelstudien stellen den Kern dieser Arbeit dar: (1) Die Quantifizierung der Antwortverzögerung des mobilen Radon-Detektors RAD7, an-gewendet für die Radon-in-Wasser-Kartierung. Die Antwortverzögerung des mobilen Radon-in-Luft-Detektors RAD7 wurde für zwei Messanordnungen (Radonextraktion via RADaqua und via Membranmodul) sowie für einen Bereich von Wasserdurchflussraten bestimmt. Für die Radonextraktion via RADaqua ist die Antwortverzögerung stärker ausgeprägt als für das Membranmodul. Bei einer Wasserdurchflussrate von 1 l min-1 treten die Peaks der aufgezeichneten Werte ~10 min nach den Radon-in-Wasser Peaks auf, während die Verzögerung bei Radonextraktion via RADaqua ~18 min beträgt. Weiterhin wurde eine Reduktion der Antwortverzögerung mit zunehmenden Wasserdurchflussraten beobachtet. Der vorgestellte Algorithmus ermöglicht in Kombination mit den berechneten Radontransfer-Koeffizienten die inverse Modellierung der Radon-in-Wasser-Konzentrationen, basierend auf den RAD7-Messwerten. Dies ermöglicht beispielsweise eine genauere Lokalisierung von räumlichen Radon-in-Wasser Anomalien und folglich eine präzisere Bestimmung von Grundwasseraustrittsstellen. (2) Quantifizierung untermeerischer Grundwasseraustritte in eine große Meeresbucht (False Bay, Südafrika) Untermeerische Grundwasseraustritte (“Submarine Groundwater Discharge” – SGD) bestehen aus zwei Komponenten: (a) Süßwasser-SGD (“Fresh SGD” – FSGD) angetrieben durch den meerwärtsgerichteten hydraulischen Gradienten, und (b) re-zirkuliertem SGD („re-circulated SGD“ – RSGD), verursacht durch Prozesse wie gezeitengesteuerte Infiltration von Meerwasser in den Aquifer. Eine Radon-Kartierung entlang der gesamten Küstenlinie der Bucht führte zur Lokalisierung von SGD, woraufhin dort vertiefende Untersuchungen durchgeführt wurden. In diesem Bilanzgebiet wurden eine Salz- und eine Radon-Massenbilanz durchgeführt, um FSGD bzw. Gesamt-SGD zu bestimmen. RSGD wurde aus der Differenz von FSGD und SGD abgleitet. Für die Radon-Massenbilanz wurden neue Ansätze für die Berechnung der Radon-Entgasung in die Atmosphäre und des Radon-Mischungsverlustes mit küstenfernerem Wasser präsentiert. Die Tracer-Massenbilanzen ergaben einen FSGD-Median von 2.300 m³ d-1 bzw. 0,9 m³ d-1 pro Meter Küstenlinie und einen RSGD-Median von 6.600 m³ d-1 bzw. 2,7 m³ d-1 pro Meter Küstenlinie. Die FSGD-Rate wurde mit Hilfe eines hydrologischen Modells zur Abschätzung der Grundwasserneubildungsrate und eines Grundwasserströmungsmodells zur Abgrenzung des unterirdischen Einzugsgebiets des Bilanzraums bestimmt. Diese unabhängige Methode bestätigte die Tracer-basierten Ergebnisse. Die Bedeutung dieser Studie besteht zuvorderst in der Vorstellung neuer methodischer Ansätze bei der Radon-Massenbilanzierung sowie in der Validierung von FSGD unter Berücksichtigung hydrologischer und hydrogeologischer Daten. (3) Unterscheidung von FSGD und RSGD in einem Ästuar (Knysna Ästuar, Südafrika). Das Knysna-Ästuar ist hinsichtlich der Bestimmung von SGD im Vergleich zur False Bay ein komplexeres System, da sich neben Meerwasser, FSGD und RSGD auch Flusswasser in signifikanten Mengen im Ästuar mischt. FSGD- und RSGD-Anteile wurden anhand der chemischen Zusammensetzung des Ästuarwassers unterschieden. Für diesen Zweck wurde eine End-Member-Mischungsanalyse (EMMA) auf Grundlage von Radon- und Salinitätszeitreihen des Ästuarwassers durchgeführt. Durch ein Optimierungsverfahren wurde die Mischung der End-member Meerwasser, Flusswasser, FSGD und RSGD für jeden Zeitschritt mit dem Ziel der bestmöglichen Übereinstimmung mit den gemessenen Radon- und Salinitätszeitreihen bestimmt. Die Unsicherheit in der Bestimmung der End-member-Anteile wurde durch stochastische Modellierung (Monte-Carlo-Simulation) quantifiziert. Die höchsten Anteile von FSGD und RSGD traten bei Niedrigwasser auf. Die mittleren Anteile von FSGD und RSGD betrugen in der Nähe der Ästuarmündung 0,2 % und 0,8 % während einer 24-stündigen Zeitreihenmessung. Diese Informationen führten in Kombination mit einer Radon-Massenbilanz zur Bestimmung eines mittleren FSGD von 46.000 m³ d-1 sowie eines mittleren RSGD von 150.000 m³ d-1. Diese Ergebnisse implizieren unter Einbeziehung weiterer Daten, dass SGD ein bedeutender Pfad für den Eintrag von gelöstem anorganischem Stickstoff (DIN) in das Knysna-Ästuar darstellt. Diese Studie zeigt das Potenzial einer EMMA für die Bestimmung der Anteile von vier End-membern unter Nutzung von zwei gemessenen Variablen und unter Berücksichtigung der End-member-Unsicherheit. Außerdem wurde die Bedeutung von SGD für das Wasser- und DIN-Budget des Knysna-Ästuars aufgezeigt. (4) Quantifizierung von Grundwasseraustrittsrate und Wasserverweilzeit eines grundwas-sergespeisten Sees (Ammelshainer See, Deutschland). Der vorgestellte Ansatz nutzt die stabilen Isotope des Wassers (δ18O, δ2H) und von Ra-don für die Bestimmung des mittleren langfristigen sowie der aktuellen Grundwas-seraustrittsrate. Die Berechnungen beruhen auf Abschätzungen des Isotopeninventars anhand von Feldmessungen, der Isotopensignatur des Grundwassers sowie ergänzen-den Klima- und Isotopen-Daten (Niederschlag). Die Ergebnisse einer stationären Isoto-pen-Massenbilanz für δ18O und δ2H sind übereinstimmend und ergaben einen langfristigen mittleren Grundwasseraustritt von 2.800 bis 3.350 m³ d-1. Dieses Ergebnis wurde für die Modellierung des jährlichen Zyklus des Isotopeninventars im See benutzt, welches mit den gemessenen Isotopenwerten konsistent ist. Die auf Grundlage einer Radon-Massenbilanz abgeleiteten aktuellen Grundwasserzutrittsraten lagen im Gegensatz dazu deutlich niedriger, was jedoch nicht notwendigerweise einen Widerspruch darstellen muss, sondern vielmehr ein Hinweis auf eine möglicherweise ausgeprägte saisonale Variabilität des Grundwasseraustritts darstellen kann. Diese Studie zeigt Möglichkeiten und Grenzen der Anwendung von einer Kombination aus δ18O/δ2H- und Radon-Massenbilanzen für die Bestimmung der Grundwasseranbindung von Seen mit einem vergleichsweise geringen Messaufwand unter Nutzung qualitativ hochwertiger und umfangreicher Klima-und Isotopen-Daten (Niederschlag). Diese Dissertation präsentiert wichtige methodische Fortschritte hinsichtlich der An-wendung von Radon- und stabilen Isotopen-Massenbilanzen, der Quantifizierung von Unsicherheit, der Unterscheidung von FSGD und RSGD anhand geochemischer Daten und der Validierung von FSGD. Außerdem wurden erstmals SGD-Raten für Standorte in Südafrika (False Bay und Knysna-Ästuar) vorgestellt.

Les cycles océaniques du carbone et des principaux nutriments sont mal connus car ils sont affectés par de nombreux puits et sources physiques, chimiques ou biologiques difficiles à estimer par des mesures directes. Une manière de mieux contraindre ces processus importants est d’utiliser l’information contenue dans des traceurs plus simples : les proxies. Le radium 228 (228Ra), émis par les plateaux continentaux, est utilisé comme proxy des flux d’eau et d’éléments minéraux de la côte vers l’océan ouvert. Il permet en particulier d’estimer les flux d’eau souterraine ou SGDs (Submarine Groundwater Discharge). Le thorium 234(234Th), insoluble, permet quant à lui de contraindre la dynamique des particules par lesquelles il est adsorbé. Il est régulièrement utilisé pour estimer la pompe biologique du carbone (PBC), c’est-à-dire le flux de carbone de la surface vers l’océan profond.Au cours de cette thèse, un modèle numérique à une résolution de 2° a été construit pour chacun de ces deux radio-isotopes, en s’appuyant sur la circulation du modèle NEMO-OPA et les champs de particules du modèle PISCES. Plusieurs paramètres inconnus des modèles ont été contraints par des observations dans le cadre d’une méthode inverse.La modélisation inverse du 228Ra a permis d’estimer les flux de 228Ra venant de 38 régions côtières. En revanche, l’estimation des SGDs est imprécise, car les SGDs sont difficiles à distinguer d’une autre source de 228Ra: la diffusion par les sédiments.La modélisation inverse du 234Th a permis d’estimer les coefficients de partage du 234Th, qui représentent l’affinité de différents types de particules pour cet isotope. Elle a aussi permis d’estimer les erreurs associées à quelques simplifications courantes dans les études de la PBC fondées sur le 234Th. / The oceanic cycles of carbon and the main nutrients are poorly known since they are affected by many physical, chemical or biological sources and sinks that are difficult to estimate by direct measurements.One way to better constrain these important processes is to use the information contained in more simple tracers called "proxies". As radium 228 (228Ra) flows from the continental shelves, it is used as a proxy of water and mineral elements fluxes from the coast to the open ocean. In particular, it is often used to estimate the SGD (Submarine Groundwater Discharge). For its part, thorium 234 (234Th), an insoluble radio-isotope, is used to constrain the dynamics of the solid particles onto which it is adsorbed. The carbon flux from the surface to the deep ocean, called "biological carbon pump" (BCP), is often estimated by a 234Th-based method.During this PhD, a numerical model with a resolution of 2°, based on the circulation of the NEMO-OPA model and the particle fields of the PISCES model, was built for each of the two radioisotopes.Several unknown model parameters were constrained by observations using an inverse technique.The inverse modeling of 228Ra was used to constrain 228Ra fluxes from 38 coastal regions.However, the SGD fluxes are poorly constrained by this method, because SGD can be confused with another source of 228Ra: diffusion from sediments.The inverse modeling of 234Th produced estimates of partition coefficients, representing the affinity of different particle types for this isotope. It was also used to estimate the errors associated with some common simplifications made in 234Th-based BCP studies.

This thesis investigates the effectiveness of Tabular Variational Auto Encoders (TVAEs) in generating high-quality synthetic tabular data and assesses their compliance with differential privacy principles. The study shows that while TVAEs are better than VAEs at generating synthetic data that faithfully reproduces the distribution of real data as measured by the Synthetic Data Vault (SDV) metrics, the latter does not guarantee that the synthetic data is up to the task in practical industrial applications. In particular, models trained on TVAE-generated data from the Creditcards dataset are ineffective. The author also explores various optimisation methods on TVAE, such as Gumbel Max Trick, Drop Out (DO) and Batch Normalization, while pointing out that techniques frequently used to improve two-dimensional TVAE, such as Kullback–Leibler Warm-Up and B Disentanglement, are not directly transferable to the one-dimensional context. However, differential privacy to TVAE was not implemented due to time constraints and inconclusive results. The study nevertheless highlights the benefits of stabilising training with the Differential Privacy - Stochastic Gradient Descent (DP-SGD), as with a dropout, and the existence of an optimal equilibrium point between the constraints of differential privacy and the number of training epochs in the model. / Denna avhandling undersöker hur effektiva Tabular Variational AutoEncoders (TVAE) är när det gäller att generera högkvalitativa syntetiska tabelldata och utvärderar deras överensstämmelse med differentierade integritetsprinciper. Studien visar att även om TVAE är bättre än VAE på att generera syntetiska data som troget återger fördelningen av verkliga data mätt med Synthetic Data Vault (SDV), garanterar det senare inte att de syntetiska data är upp till uppgiften i praktiska industriella tillämpningar. I synnerhet är modeller som tränats på TVAE-genererade data från Creditcards-datasetet ineffektiva. Författaren undersöker också olika optimeringsmetoder för TVAE, såsom Gumbel Max Trick, DO och Batch Normalization, samtidigt som han påpekar att tekniker som ofta används för att förbättra tvådimensionell TVAE, såsom Kullback-Leibler Warm-Up och B Disentanglement, inte är direkt överförbara till det endimensionella sammanhanget. På grund av tidsbegränsningar och redan ofullständiga resultat implementerades dock inte differentierad integritet för TVAE. Studien belyser ändå fördelarna med att stabilisera träningen med Differential Privacy - Stochastic Gradient Descent (DP-SGD), som med en drop-out, och förekomsten av en optimal jämviktspunkt mellan begränsningarna för differential privacy och antalet träningsepoker i modellen.

Having a meaningful system for expressing common needs and thoughts is important for overall quality of life for students with intellectual disability and limited expressive language. The current study was conducted to evaluate whether one communication system, Proloquo2Go ($249.99) or SwiftKey Symbols (FREE), is more effective in the acquisition of targeted expressive phrases in one student with intellectual disability who exhibited expressive communication difficulties. The student was provided with instruction in both systems using task analytic instruction and system of least prompting and encouraged to use each system at different times in a single case, alternating treatment design. Results indicated that Proloquo2Go led to faster acquisition of targeted phrases, although gains were shown with both devices. Although, given the cost difference, teachers and parents may want to consider free options, like SwiftKeys, given the student made gains with this device. Future research is needed to provide generalizability of these results.

Trabalho realizado na SOTNOR, Lda., orientado pelo Eng. Rui Oliveira / Tese de Mestrado Integrado. Engenharia Electrotécnica e de Computadores (Automação). Faculdade de Engenharia. Universidade do Porto. 2012