Numerical modelling applied to the understanding of groundwater flow and mass-transport in south Portugal - A perspective of regional hydrogeological problems affecting groundwater status

A presente dissertação agrega diferentes trabalhos referentes à hidrogeologia do Algarve com foco para a análise de alguns problemas relacionados com as águas subterrâneas identificados na região. Foram empregues várias ferramentas numéricas de forma a caracterizar algumas das questões mais sonantes das águas subterrâneas no Algarve do ponto de vista institucional. Seleccionaram-se dois casos de estudo, o aquífero Querença-Silves e o conjunto de aquíferos em contacto com a Ria Formosa. No primeiro caso de estudo apresentado, Querença-Silves, procedeu-se a uma análise de balanço com apoio de um modelo numérico de fluxo, com vista à evolução dos níveis de água subterrânea perante diferentes cenários de exploração e de Gestão da recarga de aquíferos. Adicionalmente, com recurso à relação de Ghyben-Herzberg, foi realizado um tratamento de pós processamento para identificar potenciais efeitos da evolução da interface água doce-água salgada, que resulta do contacto a Oeste deste aquífero com o estuário do Rio Arade. Apesar de nas condições actuais não se verificar ocorrência de intrusão salina, dados recolhidos e os resultados de modelação identificam que poderá haver um risco de ocorrência deste processo em cenários de seca prolongada aliados a extracções elevadas. Desta forma, procedeu-se à análise de cenários de Gestão da recarga de aquífero com injecção de água no sistema, de forma compreender como esta medida de mitigação poderá contribuir para a recuperação do sistema e recuo da interface água doce-água salgada. No que respeita ao caso de estudo dos aquíferos em contacto com a Ria Formosa, foi feita uma primeira análise relativamente à evolução da pluma de contaminação por nitratos na Zona Vulnerável de Nitratos de Faro, com vista ao cumprimento das exigências legais impostas pela Directiva Quadro da Água e da Directiva Nitratos. Desta forma, com o apoio de um modelo numérico de escoamento e transporte de massa, procedeu-se à análise de diferentes cenários de ocupação de solo no que respeita à área agrícola e, consequentemente, carga de nitratos no sistema. Os resultados obtidos pelo modelo sugerem que mesmo num cenário em que se interrompa por completo a entrada de nitratos no sistema, não se conseguem atingir os objectivos ambientais no sistema até 2040, que, neste caso, corresponde a concentrações de nitrato inferior a 50 mg/L. Este facto reforça a necessidade de adoptar medidas de mitigação alternativas às actuais para se conseguir reduzir o tempo necessário para cumprir com as exigências legais impostas pela Directiva Quadro da Água. Foi neste sentido que se apresentou uma análise de um cenário de Gestão de Recarga de Aquíferos com base na intercepção de água da chuva nas estufas, para posterior injecção no aquífero. Os resultados do modelo sugerem que este cenário não é suficiente para atingir a conformidade, mas que pode reduzir de forma algo significativa o tempo necessário para atingir a meta estabelecida. Ainda no que respeita aos aquíferos em conexão com a Ria Formosa, com os exercícios de modelação efectuados tornou-se evidente que há conexões hidráulicas entre os diferentes sistemas aquíferos na área de estudo, com trocas de fluxo e massa entre si e que por isso, a sua gestão não poderá ser feita de forma individualizada para cada massa de água subterrânea. Adicionalmente, foi feita uma análise histórica de forma a tentar replicar o processo de contaminação do aquífero por nitratos desde o seu estado mais pristino, com a inclusão de processos de retorno de rega e reciclagem de nitratos, com base nos dados conhecidos. Na maioria dos sistemas, a inclusão destes processos explica os valores de nitratos na água subterrânea actualmente observados, com a excepção do sector centro-sul do aquífero da Campina de Faro, em que se observam valores mais elevados que os simulados, o que possivelmente se deverá a valores históricos de carga de nitratos mais elevados que os que são conhecidos ou à existência de barreiras hidráulicas locais que impossibilitam a descarga de nitratos para a Ria Formosa. Este facto reflecte também que os valores actualmente observados são um reflexo das práticas agrícolas realizadas no passado, e desta forma, o problema não pode ser resolvido simplesmente com a adopção de práticas agrícolas mais sustentáveis. Para tal será necessário implementar medidas de mitigação alternativas. Nesse âmbito, foram simulados vários cenários de mitigação, que envolvem a interrupção de cargas azotadas no sistema, a transição da origem de água para rega para água superficial e dois cenários de Gestão de recarga de aquíferos, um com base na recarga artificial ao longo do leito de ribeiras, outro com base na intercepção de água da chuva em estufas como anteriormente referido. A integração de cenários climáticos no modelo de transporte de massa revela que apesar da implementação de medidas de mitigação, poderá haver um retardamento no decréscimo dos níveis de nitrato no aquífero superficial da Campina de Faro, resultado de processos de evapoconcentração associado à redução de recarga, aumento da extracção e processos de mistura incompletos no aquífero. Os resultados destes cenários reforçam o facto que a remediação de águas subterrâneas é uma tarefa ambiental complicada, especialmente no que se refere a processos de poluição difusa em áreas muito extensas e que para se atingirem as metas ambientais e o bom estado da água subterrânea, é necessário um conjunto de soluções convencionais e alternativas, de aplicação a escala local ou escala mais regional. Através de ferramentas de estatísticas procedeu-se ainda a uma análise das relações entre padrões climáticos com a oscilação dos níveis de água subterrânea nos casos de estudo. Os resultados desta análise tarefa permitiram compreender melhor como os níveis das águas subterrâneas se podem comportar em diferentes cenários climáticos, e o que se pode esperar dos efeitos de curto e médio prazo de recarga na região do Algarve. A implementação de modelos numéricos de fluxo e transporte de massa aliado à análise estatística das relações dos padrões climáticos com a oscilação dos níveis resultou numa ferramenta importante de caracterização dos sistemas aquíferos em estudo, com a redução da incerteza sobre os sistemas e a previsão de cenários de mitigação e cenários climáticos.Numerical tools were developed to investigate some of the main groundwater management issues identified in the Algarve region (south Portugal). Two study areas are considered as case-studies, one consisting of the Querença-Silves aquifer which focuses on water balance issues, the other consisting of a set of aquifers in contact with the Ria Formosa coastal lagoon, with focus on the Nitrate Vulnerable Zone of Faro and the evolution of nitrate contamination in groundwater. Groundwater flow and mass-transport numerical models were developed to assess groundwater management issues identified in the study areas. Different types of scenarios have been simulated and analyzed, which take into account changes in land-use leading to different contamination input, changes in groundwater abstraction, mitigation scenarios, with particular focus for simulation of Managed Aquifer Recharge schemes and climate change effects. The use of numerical models was shown to be a powerful tool not only characterize hydrogeological problems, but also to predict the evolution of the current observed conditions under different scenarios. One of the main outcomes of the modelling showed that the nitrate contamination in the nitrate vulnerable zone of Faro is a persistent issue, which is a result of agricultural practices in the past. The current applied solutions rely on the adoption of good agricultural practices, but this was shown not be enough to achieve compliance within the Water Framework Directive. Groundwater remediation is one of the most difficult tasks in environmental clean-up, especially when it comes to large areas. Therefore, an ensemble of solutions, some local, some more regional, including land management measures, should be considered in order to attain a significant reduction of time in achieving good quality status of groundwater bodies. Together with the time-series analysis, the implemented models allowed to have a better understanding of the aquifer dynamics in terms of flow and mass-transport.The research leading to these results has also received support from following projects: - Project LIFE Charcos, financed by the LIFE program under contract Reference: LIFE12 NAT/PT/000997; v - MARSOL project financed by the European Union Seventh Framework Programme (FP7/2007‐2013) under grant agreement GA-2013-619120; - eGROUNDWATER project, financed by the Horizon 2020 under PRIMA partnership section Research and Innovation Programme, grant greement GA n.1921; - ACORDO ESPECÍFICO DE COLABORAÇÃO ENTRE A AdA E A UALG - Execução dos Planos de Monitorização, em conformidade com o preconizado na DCAPE, no RECAPE e EIA da ETAR de Faro-Olhão (Projecto Financiado pela empresa Águas de Portugal em regime de prestação de serviços)

Modelling the fate of oxidisable organic contaminants in groundwater

Subsurface contamination by organic chemicals is a pervasive environmental problem, susceptible to remediation by natural or enhanced attenuation approaches or more highly engineered methods such as pump-and-treat, amongst others. Such remediation approaches, along with risk assessment or the pressing need to address complex scientific questions, have driven the development of integrated modelling tools that incorporate physical, biological and geochemical processes. We provide a comprehensive modelling framework, including geochemical reactions and interphase mass transfer processes such as sorption/desorption, non-aqueous phase liquid dissolution and mineral precipitatation/dissolution, all of which can be in equilibrium or kinetically controlled. This framework is used to simulate microbially mediated transformation/degradation processes and the attendant microbial population growth and decay. Solution algorithms, particularly the split-operator (SO) approach, are described, along with a brief résumé of numerical solution methods. Some of the available numerical models are described, mainly those constructed using available flow, transport and geochemical reaction packages. The general modelling framework is illustrated by pertinent examples, showing the degradation of dissolved organics by microbial activity limited by the availability of nutrients or electron acceptors (i.e., changing redox states), as well as concomitant secondary reactions. Two field-scale modelling examples are discussed, the Vejen landfill (Denmark) and an example where metal contamination is remediated by redox changes wrought by injection of a dissolved organic compound. A summary is provided of current and likely future challenges to modelling of oxidisable organics in the subsurface

The chemical work of Thomas Graham

Thomas Graham (1805-1869) was taught Chemistry at the Universities of Glasgow and Edinburgh by the students of Joseph Black: Thomas Thomson and Thomas Charles Hope. Graham devoted himself to Chemistry, despite opposition from his father, and became one of the foremost British chemists of his age. Essentially inductive in his research work, Graham investigated molecular movements in gases and liquids and the role of water in the constitution of acids and salts. Graham made use of analogy in directing his researches. Thus, he believed that there was a partial analogy between gaseous and liquid diffusion; both processes depended ultimately on inherent molecular motions. The chemical affinity of water for different substances connected his studies of acids and salts with the liquid state. His first chemical investigations of 1825 were concerned with the absorption of gases by liquids. Inspired by Faraday's liquefaction experiments, Graham emphasised the continuity of the states of matter and suggested an analogy between liquefaction and gaseous absorption. Heat was an important consideration in these changes of state. Graham was cautious in drawing conclusions from his experiments although he speculated imaginatively. It is possible that Graham's belief in atoms of primary matter, endowed with different, unalterable motions for each element, was conceived at the time of his first studies of gaseous diffusion. However, he slid not express this view openly until 1863. In this thesis, I have traced the development of Graham's chemical work by exploiting: unpublished manuscript material and the views of Graham and his contemporaries. Graham responded to criticisms of his work. When Berzelius dismissed the polybasic nature of the phosphoric acids, Graham countered by rejecting inorganic isomerism and he subsequently investigated polymerism. Bunsen's denial of the diffusion law and the rejection of Graham's first explanation of osmosis were spurs to further creative experimental investigations

Age-related macular degeneration: interventional tissue engineering and predictive modeling of disease progression

Thesis (Ph.D.)--Boston UniversityAge-related macular degeneration (AMD) is the leading cause of irreversible blindness in people over the age of 50. As many as 50 million people are affected by AMD worldwide and prevalence is expected to continue to rise due to an aging population. There are two forms of the disease, dry (geographic atrophy) and wet (choroidal neovascularization), both of which result in retinal degeneration and central vision loss. Although anti-vascular endothelial growth factor therapies are moderately successful at treating the wet form, there are no treatments currently available for the more common dry form. Pharmacological therapies have been extensively explored for the treatment of dry AMD, but have achieved little success because the pathogenesis underlying AMD is unknown and likely varies among patients . Recently, tissue engineering has emerged as a promising approach to restore function by replacing diseased retinal tissue with healthy retinal pigment epithelium (RPE). While AMD-associated vision loss occurs when photoreceptors degenerate, this process arises as a consequence of earlier RPE dysfunction. In the healthy retina, the RPE acts as a critical regulator of the microenvironment for both photoreceptors and the nearby vasculature. However in AMD, the RPE no longer performs these essential homeostatic functions leading to photoreceptor apoptosis and vision loss. This dissertation describes the development and in vitro characterization of a tissue engineering scaffold for RPE delivery as potential treatment for dry AMD. First, a novel microfabrication-based method termed "pore casting" was developed to produce thin scaffolds with highly controlled pore size, shape, and spacing. Next, human RPE were cultured on pore-cast poly(c-caprolactone) (PCL) scaffolds and compared to cells on track-etched polyester, the standard RPE culture substrate. RPE on porous PCL demonstrated enhanced maturation and function compared to track-etched polyester including improved pigmentation, barrier formation, gene expression, growth factor secretion, and phagocytic degradation. Lastly, this study established a patient-specific method for predicting AMD progression using retinal oxygen concentration. This approach differs from current diagnosis techniques because it uses physiologically-relevant mechanisms rather than generalized clinical associations which have little, if any, prognostic value

Modelling and Monitoring of Phosphorus Transport and Speciation in Soil

Merged with duplicate record 10026.1/1270 on 08.03.2017 by CS (TIS)Flow through soil into groundwater has been classically conceptualised as taking place through a set of aligned capillary tubes. In solute transport models these approximations are also present. Pore-Cor (a network model) has been used to model the void structure of soil by using water retention and mercury porosimetry curves. The model successfully predicts trends in saturated hydraulic conductivity. The effect of the assumptions used in the Pore-Cor geometry have been investigated by comparing of two dimensional slices of the simulated networks with two dimensional image analysis data. The geometric limitations of the model cause packing inefficiencies which prevent the model from representing the size distribution of voids found in real samples. The observation of environmental events is dependent upon the implementation of rapid and reliable analytical techniques. This work presents an adaptation of an FI method for the determination of dissolved reactive phosphorus (DRP) and a new method for the determination of total dissolved phosphorus (TDP). Both are ideally suited to the detection of phosphorus species in soil leachate and runoff waters over the concentration range 3 to 1000 ng 1-1. The effect of compaction on solute transport is described and the experimental data have been modelled using a modified form of the convection dispersion equation (CDE). The parameters of the CDE have been given structural interpretation by the network model. The model was used to interpret a change in dispersivity and the behaviour of reactive phosphorus species on compaction.The Institute of Grassland and Environmental Research, North Wyke, Devo

Integrated Geophysical Methods for Shallow Aquifers Characterization and Modelling

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