Repositório Institucional da Universidade de Aveiro
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Impact of freshwater inflow on bacterial abundance and activity in the estuarine system Ria de Aveiro
No full textThe influence of freshwater flow on bacterial communities in the estuarine system Ria de Aveiro (Portugal) was investigated at two sites differently impacted by river inputs, representative of the marine and brackish water zones of the estuary. Sampling events were clustered based on hydrological features. The hydrodynamic was simulated with a Lagrangian model and related to microbiological parameters. Estuarine bacteria responded to different freshwater regimes developing distinct patterns of abundance and activity at the marine and brackish water zones. A circulation pattern induced by high river inflow produced vertical stratification in the marine zone, promoting a seaward flux of bacterioplankton, and stimulating the import of riverine phytoplankton and particle-attached bacteria to the brackish water zone. Advective transport and resuspension processes contributed to a 3-times increase in abundance of particle-attached bacteria during intense freshwater inputs. Additionally, bacterial activity in the estuary was controlled by inorganic nitrogen, responding to different freshwater inputs, which, in association with different prevailing sources of organic substrates induced significant changes in bacterial production. The dynamic and main controlling factors of bacterial communities are clearly impacted by freshwater inputs. Therefore, significant changes in the recycling of nutrients by microbial activities can be expected from alterations in freshwater inputs either related to global climate change or regional hydrological regimes
Progression of DNA damage induced by a glyphosate-based herbicide in fish (Anguilla anguilla) upon exposure and post-exposure periods - Insights into the mechanisms of genotoxicity and DNA repair
No full textRoundup(R) is a glyphosate-based herbicide widely used with both agricultural and non-agricultural purposes, which has been demonstrated to represent a risk to non-target aquatic organisms, namely fish. Among the described effects to fish, genotoxicity has been pointed out as one of the most hazardous. However, the genotoxic mechanisms of Roundup?? as well as the involvement of the oxidative DNA damage repair system are not entirely understood. Hence, this work aimed to improve the knowledge on the progression of DNA damage upon short-term exposure (3 days) and post-exposure (1-14 days) periods in association with DNA repair processes in Anguilla anguilla exposed to Roundup?? (58 and 116 ??g L- 1). DNA damage in hepatic cells was evaluated by the comet assay improved with the DNA-lesion specific endonucleases FPG and EndoIII. In order to evaluate the oxidative DNA damage repair ability, an in vitro base excision repair (BER) assay was performed, testing hepatic subcellular extracts. Besides the confirmation of the genotoxic potential of this herbicide, oxidative damage was implicit as an important mechanism of genetic damage, which showed to be transient, since DNA integrity returned to the control levels on the first day after cessation of exposure. An increased capacity to repair oxidative DNA damage emerging in the post-exposure period revealed to be a crucial pathway for the A. anguilla recovery; nevertheless, DNA repair machinery showed to be susceptible to inhibitory actions during the exposure period, disclosing another facet of the risk associated with the tested agrochemical
Combination effects of anticholinesterasics in acetylcholinesterase of a fish species: effects of a metallic compound, an organophosphate pesticide, and a pharmaceutical drug
No full textThe simultaneous presence of distinct compounds in the aquatic environment can be causative of various toxicological interactions. This scenario challenges ecotoxicologists, since the assessment of toxicological effects caused by the simultaneous presence of multiple substances is by far more complicated. An illustrative example can be given by mentioning the anticholinesterasic compounds: by studying the level of cholinesterase impairment of an exposed organism, it is possible to ascertain the level of exposure to all anticholinesterasics (despite their chemical classes and natures) that the organism was subjected to. In this work, we describe the effects of three chemically different, albeit mechanistically, and toxicologically similar compounds (copper, chlorfenvinphos, and pyridostigmine) on cholinesterases of the fish Gambusia holbrooki. The results showed that the combinatorial effects may be of considerable extent, even for levels of exposure that are close to the ones already reported in the wild, for each isolated compound
Effects of chronic exposure to lead, copper, zinc, and cadmium on biomarkers of the European eel, Anguilla anguilla
No full textExposure to specific metallic compounds can cause severe deleterious modifications in organisms. Fishes are particularly prone to toxic effects from exposure to metallic compounds via their environment. Species that inhabit estuaries or freshwater environments can be chronically affected by persistent exposure to a large number of metallic compounds, particularly those released by industrial activities. In this study, we exposed yellow eels (European eel, Anguilla anguilla) for 28 days to environmentally relevant concentrations of four specific metals; lead (300, 600, and 1,200 μg/l), copper (40, 120, and 360 μg/l), zinc (30, 60, and 120 μg/l) and cadmium (50, 150, and 450 μg/l). The selected endpoints to assess the toxicological effects were neurotransmission (cholinesterasic activity in nervous tissue), antioxidant defense, and phase II metabolism (glutathione-S-transferase [GST] activity, in both gills and liver tissues), and peroxidative damage. The results showed an overall lack of effects on acetylcholinesterase for all tested metals. Lead, copper, and cadmium exposure caused a significant, dose-dependent, increase in GST activity in gill tissue. However, liver GST only significantly increased following zinc exposure. No statistically significant effects were observed for the thiobarbituric acid reactive substances assay, indicating the absence of peroxidative damage. These findings suggest that, despite the occurrence of an oxidative-based response after exposure to lead, copper, and cadmium, this had no consequence in terms of peroxidative membrane damage; furthermore, cholinergic neurotoxicity caused by lead, copper, and cadmium did not occur. The implications of these results are further discussed
Size fractionated aerosol composition at roadside and background environments in the Madrid urban atmosphere
No full textThe chemical composition of size-segregated particulate matter (PM) was studied during summer and winter sampling campaigns, at two different urban sites (roadside and urban background) in the city of Madrid, Spain. PM was sampled with high volume cascade impactors, in 4 size ranges: 10-2.5, 2.5-1, 1-0.5 and <0.5??m. The carbonaceous content (OC and EC) was determined by a thermo-optical method, whilst the water soluble ionic species were measured by ion chromatography. The most common synoptic meteorological situations, including those causing the transport of African dusty air masses, were identified in both seasons. Whether the PM10 mass or the highest concentrations of EC and OC were found predominantly in the ultrafine size fraction at both sites. In contrast with roadside, at the urban background, the particle mass concentrations for the different size ranges were statistically higher in summer than in winter. Observed inter-site differences suggest the existence of other sources and formation processes contributing in the summer period to the levels of PM at the urban background site apart from road traffic emissions. Secondary organic carbon (SOC) showed a clear seasonal pattern, with much higher concentrations in summer than in winter in both places, as well as higher relative contributions at the urban background than at the road traffic site. (NH4)2SO4 levels were at their maximum at both sites in summer in PM0.5. Differently, higher values were reached in winter for NH4NO3 in PM0.5 and for NaCl in PM2.5-10. From the ion balances, it was observed that, in summer, the formation of secondary inorganic compounds included an unusual enrichment in Ca2+ in the submicrometre fraction, either at roadside or at urban background
Oxidative stress and histological changes following exposure to diamond nanoparticles in the freshwater Asian clam Corbicula fluminea (Muller, 1774)
No full textRecently, the scientific community became aware of the potential ability of nanoparticles to cause toxicity in living organisms. Therefore, many of the implications for aquatic ecosystems and its effects on living organisms are still to be evaluated and fully understood. In this study, the toxicity of nanodiamonds (NDs) was assessed in the freshwater bivalve (Corbicula fluminea) following exposure to different nominal concentrations of NDs (0.01, 0.1, 1, and 10 mg l−1) throughout 14 days. The NDs were characterized (gravimetry, pH, zeta potential, electron microscopy, and atomic force microscopy) confirming manufacturer information and showing NDs with a size of 4–6 nm. Oxidative stress enzymes activities (glutathione-S-transferase, catalase) and lipid peroxidation were determined. The results show a trend to increase in GST activities after seven days of exposure in bivalves exposed to NDs concentrations (>0.1 mg l−1), while for catalase a significant increase was found in bivalves exposed from 0.01 to 1.0 mg l−1 following an exposure of 14 days. The histological analysis revealed alterations in digestive gland cells, such as vacuolization and thickening. The lipid peroxidation showed a trend to increase for the different tested NDs concentrations which is compatible with the observed cellular damage
O bário como indicador de paleoprodutividade em "cores" da margem continental portuguesa
No full textMestrado em GeoquímicaEsta dissertação tem como principal objectivo avaliar a utilização do Bário
como indicador de paleoprodutividade em "cores" de sedimentos da Margem
Continental Portuguesa, e identificar as características do seu sinal a N e a S de
Lisboa no período compreendido entre os O e 24ka. Com vista a atingir estes
objectivos foram estudadas 141 amostras pertencentes a 4 "cores" colhidos no
decorrer do cruzeiro POSEIDON200-10, dois em cada região (P028-1 e P021-1, a
N de Lisboa; P08-2 e P06-2, a S de Lisboa). A selecção destes "cores" teve como
base a existência de outros dados de indicadores biogénicos.
A técnica de preparação de amostras utilizada foi uma fusão tipo alcalina.
Como técnica instrumental foi utilizada a Espectrofotometria de Emissão
Atómica de Plasma, que permitiu efectuar a determinação dos elementos maiores
e em traço na amostra total. Com o objectivo de controlar a qualidade dos
resultados analíticos foram efectuados estudos de precisão e de exactidão. Os
primeiros tiveram por base a utilização de resultados analíticos referentes a
amostras em duplicado, os quais foram projectados em gráficos de controle para
avaliação da precisão analítica com o modelo de precisão de 5% (10)
desenvolvido por Thompson et al., (1976). Este modelo indica que para todos os
elementos maiores e alguns em traço (onde se inclui o Bário) os valores de
precisão do método analítico são inferiores a 5%. No que diz respeito ao estudo
de exactidão foram utilizados os dados analíticos do material geológico de
referência (MESS-I), bem como os seus valores certificados. De modo a avaliar o
nível de significância estatística para um p=0,05% dos vários elementos
determinados foi calculado o valor do t de Student. Para o Bário não foi possível
efectuar o estudo da exactidão por não ser disponível o seu valor certificado. De
entre todos os elementos analisados foram escolhidos o Bário e os óxidos de Si e
de Al.
Ao longo dos "cores" verificou-se a existência de uma variação no
comportamento do sinal do Bário mais saliente nos "cores" localizados a S de
Lisboa. Como forma de tentar eliminar o efeito de diluição da contribuição
terrígena no sinal do Bário biogénico foram utilizados os métodos
desenvolvidos por Schmitz (1987), Dymond et al. (1992) e Rutsch et al. (1995).
Os resultados obtidos por aplicação dos métodos anteriores mostram que os
"cores" localizados a N de Lisboa apresentam um maior efeito de diluição do
sinal biogénico que os "cores" do S. Uma possível explicação para este facto, é o
da localização dos "cores" P028-1 e P021-1 se encontrar mais próxima do bordo
da plataforma aquando da ocorrência do último glaciar máximo, cerca dos 18ka,
originando uma maior e mais próxima contribuição de material teidgeno. Para além
disso, outros factores como os diferentes tipos de relevo, o número e o tipo de rios
existente podem contribuir de maneira significativa para esse efeito de diluição.
Da conjugação de todos estes resultados, é possível concluir que o Bário
pode ser utilizado como indicador de paieoprodutividade na Margem Continental
Portuguesa, sendo no entanto, de salientar a importância da quantificação da
contribuição da componente terrígena no seu sinal
Caracterização e aplicabilidade na indústria dos cimentos de lamas de rochas ornamentais transformadas na região de Pêro Pinheiro
No full textMestrado em Minerais e Rochas IndustriaisNa região de Pero Pinheiro existe a maior concentração nacional de
industrias transformadoras de rochas ornamentais, estando as lamas resultantes dos processos
de transformao na origem de graves problemas ambientais, devido a sua deposição
desordenada e incontrolada em terrenos vizinhos e pedreiras abandonadas. Importava assim,
encontrar uma solução de viabilização para o aproveitamento destes resíduos, tanto para os já
produzidos como para os que venham a ser produzidos, já que se verifica um acentuado
crescimento no sector da transformação das rochas ornamentais, o que será inevitavelmente
acompanhado por uma incrementação na produção de residuos.
De entre uma série de possiveis aplicação e, tendo em consideração a natureza e o
quantitativo destes resíduos, a industria dos cimentos foi a que se revelou mais atractiva, quer
devido a natureza das matérias-primas que utiliza (geralmente calcários e argilas ou calcários
margosos), quer pela enorme capacidade de absorver no seu processo de fabricação grandes
volumes de matérias-primas sem necessitarem de tratamentos complexos, sendo, entre todas as
industrias, a que consome maiores quantidades de matérias-primas.
Por outro lado, o aumento no consumo de cimento que se tem verificado nos últimos
anos, requerendo cada vez maiores volumes de matérias-primas, acarreta a destruição de
recursos minerais, afigurando-se tambem importante que se promova a poupança destes
recursos, já que são ilimitados e não renováveis.
A tendência seria, consequentemente, a utilização de subprodutos e de resíduos de
outras industrias, como matérias-primas para a produção de cimento, conduzindo a que o
residuo de uma industria se torne matária-prima de outra.
Neste contexto, importava averiguar a possibilidade de produção de clinquer de
cimento Portland, utilizando como matérias-primas as lamas de natureza carbonatada e
silicatada, resultantes dos processos de transformação de rochas ornamentais. 0s resultados
das investigações realizadas confirmaram essa possibilidade.In Pero Pinheiro's region stands the biggest Portuguese concentration of
ornamental rocks transformation plants. The waste muds that result fiom the transformation
processes are at the origin of serious environmental problems, that result 50m their
uncontrolled and random disposal in terrains and abandomned quarries. Therefore, it's of the
upmost importance to find a solution that makes these residues usable. The ones that had been
already produced and those that are to be produced. This need is enhanced in face of the
occuring accentuated growth in the sector of ornamental rocks transformation, that will
inevitably be accompaigned by an increase in the residues production.
Of a series of possible applications, and taking into consideration the nature and the
quantity of these residues, the cement industry was the one to reveal itself as being the most
attractive. This was a consequence of, in one hand, the nature of the raw materials it uses
(usualy limestones and shales or marly limestones), on the other hand, the enourmous capacity
to absorb in its fabrication process, big volumes of raw materials without the need for complex
treatments. Within all the industries that could use these wastes the cement industry is the one
that consumes larger amounts of raw materials. On the other hand, the increase in cement
consumption that is being verified, requires increasing volumes of raw materials that, implies
the destruction of natural resources. This fact enhances the importance of promoting the
maintainance of these resources, that are limited and unrenewable, through input alternatives.
The tendency, therefore, will be the usage of sub-products and of residues of other
industries, that can function as raw materials in the production of cement, transforming one
industry residue into other industry raw material.
In this context, it was important to check the possibility of Portland clinker cement
production, with the usage, as raw materials, of the carbonated and silicated waste muds, that
are produced as a result from the transformation process of ornamental rocks. The research
being carried out confirmed that possibly referred to
Science education practices in the framework of secondary school curricular restructuring in East Timor
No full textEducation in East Timor is facing enormous challenges and struggling under harsh conditions in all aspects of education reconstruction, namely infrastructure, human and material resources, the curriculum and the dilemma of language learning.
Like other developing countries, East Timor has given great importance to reform of the secondary school curriculum. This chapter reports on the findings of a study to investigate the status of and challenges to current science practices in East Timorese secondary schools, after the curricular reforms, and the impact of evaluation on these practices (2013 to 2015). A multi-method approach using
qualitative data with quantitative analysis was implemented. Research data was obtained through focus group discussions and interviews with teachers, teacher trainers, students and school directors from schools selected for the study. The study also drew on observations of science classes and key curricular documents, allowing the data to be triangulated. Bearing this in mind, this work is divided into two main parts. After the introduction, there is a presentation of what the new secondary school science curricula suggest, in curricular, scientific
and didactic terms. Next, based on the opinions of interviewees,(a) the diversity of strategies, including didactic resources used in science disciplines, (b) the relevance for their users and also (c) any limitations are described and analysed. Finally, the conclusions are presented. One of the findings of this study is that most science teachers in secondary schools in East Timor have never done any laboratory work and do not carry out demonstrations. Many of them have
never been given any training in practical activities but, in the opinion of some Portuguese teacher trainers, it is possible to do so using simple and existing materials on site. Teachers recognized their lack of skills in this area, and attributed their low motivation to factors such as large classes, length of lessons, lack of physical space in schools and a lack of in-service
training. With respect to what students think of the learning of science, they feel they are passive learners with the teacher merely imparting knowledge. Concerning infrastructure and resources, as in many countries with a low level of development and with transitional societies, all of the interviewees thought that quite a few schools function with barely minimal resources: they have no roofs, desks or chairs, no electricity or water, and the sanitation facilities are extremely poor