Métodos de fitorremediação e biomonitorização com base em modelos experimentais aplicados ao ensino das ciências
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2013-11-14
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A presente dissertação de doutoramento tem como principais objetivos: identificar plantas aquáticas e semiaquáticas bioindicadoras e/ou fitorremediadoras de urânio (U), na Horta da Vilariça; reproduzir laboratorialmente ensaios de fitofiltração de plantas aquáticas; construir modelos experimentais para aplicação em sala de aula, em diferentes disciplinas, lecionadas no ensino básico, secundário e profissional.
As águas superficiais analisadas, ainda que com tendência pouco mineralizada, apresentam, no entanto, concentrações apreciáveis em Fe, Na, Zn e Mn. Todas as amostras de água apresentam uma fácies hidroquímica bicarbonatada sódica. Refletem um caráter próximo da neutralidade, ligeiramente alcalinas, contrariando a normalidade em tipologia de rochas silicatadas. Algumas amostras de água revelaram valores anómalos em algumas concentrações, nomeadamente dos parâmetros químicos PO4, As, Cr, Fe, Cu e U, evidenciando fenómenos de contaminação.
Os dados hidroquímicos permitem evidenciar: a) a influência dos macroelementos correspondentes ao quimismo natural da água, nomeadamente Ca, HCO3, Na; b) a relação química entre o PO4 e o elemento químico U (aos quais o Cr revela alguma afinidade), provenientes de minerais secundários de U, como sejam a chernikovite, o grupo da meta-autunite e a sabugalite, minerais confirmados através de microssonda eletrónica; c) o comportamento independente do Cu, que poderá estar associado à sulfatação das vinhas da região ou à alteração geoquímica de minerais secundário de U, como sejam os pertencentes ao grupo da meta-torbernite, presentes na área estudada.
As plantas que apresentam, em média, uma maior concentração de U nos seus tecidos são Fontinalis antipyretica e Rorippa sylvestris (zona aérea). Esta última é a única planta que apresenta valores de concentração de U, em média, superiores na zona aérea face à zona radicular, o que revela grande capacidade de translocação. Apresenta pois um índice de translocação elevado. As plantas que apresentam valores, em média, mais elevados do fator de bioacumulação são: Scorpiurium deflexifolium, Fontinalis antipyretica, Rorippa nasturtium (zona radicular) e Rorippa Sylvestris (zona aérea).
Os ensaios de fitofiltração evidenciam correlações positivas muito significativas, entre as concentrações de U presentes nas águas e acumuladas pelas diversas espécies estudadas. Assim, as espécies testadas (Fontinalis antipyretica, Callitriche stagnalis, Callitriche brutia, Elodea canadensis, Ranunculus trichophyllus, Rorippa nasturtium) revelam grande potencial para ações de bioindicação deste tipo de contaminação. Também os ensaios realizados com a espécie Fontinalis antipyretica, interpretados em consideração com a sua taxa de biomassa, permitem verificar o seu potencial para ações de fitorremediação de águas contaminadas com U.
A aplicação pedagógica deste estudos no processo de ensino/aprendizagem por cooperação, entre grupos de alunos e grupos disciplinares de docência, tornou-se muito motivador para alunos e professores. De notar que os resultados finais tiveram uma auto e heteroavaliação muito positivas.
Os cinco modelos experimentais concebidos e construídos podem ser utilizados para a simulação de situações alternativas de contaminação e fitorremediação. Pelo que é possível, utilizando os modelos construídos, simular fenómenos de contaminação com um elemento químico ou combinações multielementares, e sistemas de fitorremediação em monocultura ou com combinações de diversas espécies, simulando condições mais próximas das naturais.
This doctoral dissertation has two main objectives: first to identify aquatic plants and semi-aquatic plants as bioindicators and phytoremediator of uranium (U), in Horta da Vilariça; second to reproduce laboratory tests for phytofiltration of aquatic plants and build experimental models for application in the classroom of different courses taught in elementary, secondary and vocational schools. The surface water analyzed contained significant concentrations of Fe, Na, Zn and Mn even though there was little tendency of mineralization present. All water samples show a sodium bicarbonate hydrochemical facies. They reflect a character close to neutral; one that is slightly alkaline and also contradicting the normal typology of silicate rocks. Some water samples showed values of abnormal concentrations in chemicals such as PO4, As, Cr, Fe, Cu and U indicating a contamination phenomenon. The hydrochemical data indicates: a) the influence of the macro elements corresponding to the composition of natural water, in particular Ca, HCO3, Na; b) the chemical relation of PO4 and U (which shows some similarities to Cr), that come from secondary minerals related to U such as chernikovite, the group of meta-autunite and sabugalite and minerals confirmed by electronic microprobe; c) the independent behavior of Cu, which may be associated with sulfur dusting of the vineyards in the region or the geochemistry alteration of U secondary minerals such as those belonging to the group of meta-torbernite present in the studied area. Plants that have, on average, a greater concentration of U in their tissues are Fontinalis antipyretica and Rorippa sylvestris (aerial zone). Rorippa sylvestris is the only plant that displays concentration values of U, on average, higher in the air area compared to against the root zone, which shows a great capacity for translocation. This shows an index of high translocation. Plants that have values, on average, with high bioaccumulation factors are: Scorpiurium deflexifolium, Fontinalis antipyretica, Rorippa nasturtium (root zone) and Rorippa sylvestris (aerial zone). The phytofiltration tests show a very significant positive correlations between U concentrations in water and accumulated by the various species. Thus, the tested species (Fontinalis antipyretica, Callitriche stagnalis, Callitriche brutia, Elodea canadensis,Ranunculus trichophyllus, Rorippa nasturtium) show great potential for bioindication actions of this type of contamination. Also tests on the species Fontinalis antipyretica, interpreted with regard to their biomass rate, allow us to verify their potential for phytoremediation actions of U contaminated water. The five experimental models that were created can be used for the simulation of alternative situations of contamination and phytoremediation. Therefore it is possible to use these models to simulate the phenomena of contamination with a chemical element, multi-element combinations and phytoremediation systems in monoculture or with combinations of various species, simulating conditions close to a natural state. The application had a great impact in the processes of teaching and learning. As a result the collaboration among groups of students and teachers generated a high level of motivation. The final evaluation was very positive. The teaching and learning process by cooperation among groups of students and teaching disciplinary groups became more motivating for students and teachers. The final results were self-evaluation and hetero-evaluation very positive.
This doctoral dissertation has two main objectives: first to identify aquatic plants and semi-aquatic plants as bioindicators and phytoremediator of uranium (U), in Horta da Vilariça; second to reproduce laboratory tests for phytofiltration of aquatic plants and build experimental models for application in the classroom of different courses taught in elementary, secondary and vocational schools. The surface water analyzed contained significant concentrations of Fe, Na, Zn and Mn even though there was little tendency of mineralization present. All water samples show a sodium bicarbonate hydrochemical facies. They reflect a character close to neutral; one that is slightly alkaline and also contradicting the normal typology of silicate rocks. Some water samples showed values of abnormal concentrations in chemicals such as PO4, As, Cr, Fe, Cu and U indicating a contamination phenomenon. The hydrochemical data indicates: a) the influence of the macro elements corresponding to the composition of natural water, in particular Ca, HCO3, Na; b) the chemical relation of PO4 and U (which shows some similarities to Cr), that come from secondary minerals related to U such as chernikovite, the group of meta-autunite and sabugalite and minerals confirmed by electronic microprobe; c) the independent behavior of Cu, which may be associated with sulfur dusting of the vineyards in the region or the geochemistry alteration of U secondary minerals such as those belonging to the group of meta-torbernite present in the studied area. Plants that have, on average, a greater concentration of U in their tissues are Fontinalis antipyretica and Rorippa sylvestris (aerial zone). Rorippa sylvestris is the only plant that displays concentration values of U, on average, higher in the air area compared to against the root zone, which shows a great capacity for translocation. This shows an index of high translocation. Plants that have values, on average, with high bioaccumulation factors are: Scorpiurium deflexifolium, Fontinalis antipyretica, Rorippa nasturtium (root zone) and Rorippa sylvestris (aerial zone). The phytofiltration tests show a very significant positive correlations between U concentrations in water and accumulated by the various species. Thus, the tested species (Fontinalis antipyretica, Callitriche stagnalis, Callitriche brutia, Elodea canadensis,Ranunculus trichophyllus, Rorippa nasturtium) show great potential for bioindication actions of this type of contamination. Also tests on the species Fontinalis antipyretica, interpreted with regard to their biomass rate, allow us to verify their potential for phytoremediation actions of U contaminated water. The five experimental models that were created can be used for the simulation of alternative situations of contamination and phytoremediation. Therefore it is possible to use these models to simulate the phenomena of contamination with a chemical element, multi-element combinations and phytoremediation systems in monoculture or with combinations of various species, simulating conditions close to a natural state. The application had a great impact in the processes of teaching and learning. As a result the collaboration among groups of students and teachers generated a high level of motivation. The final evaluation was very positive. The teaching and learning process by cooperation among groups of students and teaching disciplinary groups became more motivating for students and teachers. The final results were self-evaluation and hetero-evaluation very positive.
Descrição
Tese de Doutoramento em Ciências da Terra e da Vida.
Palavras-chave
Fitorremediação , Biomonitorização , Ensino das ciências