Revestimentos compatíveis para alvenarias antigas sujeitas a ação severa da água

Uma das maiores causas de degradação dos revestimentos é a presença de sais solúveis, tanto nas zonas costeiras como nas zonas continentais. Estes sais podem ter origens distintas, tais como: humidade ascensional, nevoeiro salino, inundações ou ainda estarem presentes nos próprios materiais, como é o caso da utilização de areias mal lavadas. O local onde os sais cristalizam é dependente do tipo de transporte entre a alvenaria e o revestimento, assim como da severidade da envolvente ambiental (temperatura e humidade relativa). Com esta tese pretende-se desenvolver revestimentos de substituição compatíveis, eficazes e duráveis para alvenarias antigas sujeitas à ação severa da água (humidade ascensional através das fundações com elevada concentração de NaCl); desenvolver ensaios de envelhecimento acelerado baseados em ciclos de dissolução e cristalização que permitam simular a ação severa da água; perceber a influência de revestimentos com caraterísticas extremas de permeabilidade ao vapor de água aplicados nas duas faces do mesmo suporte (argamassas de cimento e resina versus argamassas de cal), e sujeitos à ação severa da água; perceber a influência de vários fatores, tais como : rasgos verticais contínuos executados no emboço e a utilização de hidrófugo no reboco no desempenho dos vários sistemas de revestimento desenvolvidos, quando sujeitos à ação severa da água;; utilizar a remoção eletrocinética de sais, em provetes simulando a influência da alvenaria e dos revestimentos, com o objetivo de reduzir a sua concentração de NaCl, para que no futuro possa ser aplicado de forma eficaz em paredes de edifícios antigos, enquanto ação de manutenção, e desta forma aumentar a durabilidade dos revestimentos. Para atingir os objetivos descritos, foram considerados: i) o desenvolvimento de provetes que permitam considerar os sistemas de revestimento desenvolvidos nesta tese e o suporte, e que simulem uma alvenaria revestida em ambas as faces, e com os quais seja possível a simulação da ação severa da água em laboratório e, ii) o desenvolvimento ciclos de dissolução e cristalização numa parede de grandes dimensões existente em laboratório, que permitam simular a ação severa da água em condições tão reais quanto possível. O objetivo final deste estudo é o desenvolvimento de um revestimento de substituição denominado “emboço ventilado” para paredes de edifícios antigos com revestimentos degradados devido à presença de humidade ascensional e sais solúveis. Pretende-se que este sistema de revestimento, composto por duas camadas de revestimento (camada base e reboco), seja compatível, durável e eficaz, e que funcione como um sistema de acumulação no qual os sais cristalizem na camada base do sistema de revestimento (executada com rasgos verticais) e não na alvenaria ou na camada exterior.

Assessing the combined effect of land management and wildfire on runoff and soil erosion in north central Portugal

Strong and sometimes extreme responses in runoff and soil erosion following wildfires have been reported worldwide. However, in the case of North-Central Portugal, little research had been carried out regarding the hydrologic and erosive impacts of several land management activities in recently burnt areas (such as ground preparation, post-fire logging or post-fire mitigation treatments). This study aims to assess post-fire runoff and soil erosion response on Eucalypt and Maritime pine plantations during the first, second and third years following wildfires. The effect of several pre-fire ground preparation operations (ploughed down-slope, contour ploughed and inclined terraces), post-fire logging activities (on both the eucalypt and pine plantations), as well as the application of hydromulch (a post-fire emergency treatment) on overland flow and soil erosion were compared to burnt but undisturbed and untreated areas. The intensive monitoring of runoff, soil erosion and selected soil properties served to determine the main factors involved in post-fire runoff and soil erosion and their spatial and temporal variation. Soil water repellency deserved special attention, due to its supposed important role for overland flow generation. Repeated rainfall simulation experiments (RSE’s), micro-scale runoff plots and bounded sediment fences were carried out and/or installed immediately after the wildfire on seven burnt slopes. Micro-scale runoff plots results under natural rainfall conditions were also compared to the RSE’s results, which was useful for assessing the representativeness of the data obtained with artificial rainfall. The results showed comparable runoff coefficient (20-60%) but lower sediment losses (125-1000 g m-2) than prior studies in Portugal, but especially outside Portugal. Lower sediment losses were related with the historic intensive land use in the area. In evaluating these losses, however, the shallowness and stoniness of the soils, as well as the high organic matter fraction of the eroded sediments (50%) must not be overlooked. Sediment limited erosion was measured in all the ploughed sites, probably due to the time since ploughing (several years). The disturbance of the soil surface cover due to post-fire logging and wood extraction substantially increased sediment losses at both the pine and eucalypt sites. Hydromulch effectiveness in reducing the runoff (70%) and sediment losses (83%) was attributed to the protective high coverage provided by hydromulch. The hydromulch significantly affected the soil cover and other soil properties and these changes also reduced the soil erosion risk. The rainfall amount was the main factor explaining the variance in runoff. However, a shift from rainfall amount to rainfall intensity was detected when either the surface cover or the infiltration capacity (hydrophilic conditions) increased. Sediment losses were controlled by rainfall intensity and surface cover. The role of soil water repellency on runoff generation was not consistent; the overall repellency levels alone were not enough to assess its hydrological impact. Soil water repellency explained runoff generation in the specific-sites model better than in the overall model. Additionally, soil moisture content was a better predictor for soil water repellency than antecedent rainfall. The natural rainfall results confirmed that RSE’s were able to capture the specific sediment losses and its organic matter content as well as the differences between the ploughed and unploughed sites. Repeated RSE’s also captured the seasonal variations in runoff and sediment losses attributed to soil water repellency. These results have implications for post-fire soil erosion modelling and soil conservation practices in the region, or areas with the same land use, climate and soil characteristics. The measured sediment loss, as well as the increasing frequency of ploughing in recently burnt and unburnt eucalypt stands, suggests ploughing is not an effective as a soil conservation measure. Logging activities with less impact are recommended in order to maintain the forest litter protecting the soil surface. Due to its high effectiveness in reducing runoff and soil erosion, hydromulch is recommended for highly sensitive and vulnerable areas.

Soil erosion mitigation following forest wildfires

This study aims to measure the effectiveness of four post-fire emergency techniques for reducing overland flow and soil erosion on the central-Portugal typical forest. The selection and development of these techniques was based on the review of the scientific background, but specially after checking throughout field rainfall simulation experiments which factors were the key for runoff and soil erosion on the specific case of high repellent soils. The forest residue mulch, a new treatment never tested before, was highly effective in reducing runoff and soil erosion in recently burnt eucalypt forest. The logging slash mulch had no obvious effect, but it was attributed to the small amounts of runoff and sediments that the untreated plots produced due to the extensive needle cast following a low severity fire. The hydromulch, a mixture of water, organic fibres, seeds, nutrients and a surfactant used in cutted slopes rehabilitation was also highly successful and was specially indicated for especially sensible areas. The utilization of polyacrylamides, a chemical agent with good performance in agricultural erosion, was not successful in post-fire runoff and soil erosion control, once that did not alter the most important key factor for soil erosion: the ground cover. The development of a new fibre optic turbidity sensor was a successful development on the soil erosion determination methodology, and its patent is being processed in the mean time.

Synthesis of new Aβ-ligands useful in diagnosis of Alzheimer's disease

Alzheimer’s disease is a chronic progressive neurodegenerative disease and is the most common form of dementia (estimated 50−60% of all cases), associated with loss of memory (in particular episodic memory), cognitive decline, and behavioural and physical disability, ultimately leading to death. Alzheimer’s disease is a complex disease, mostly occurring sporadically with no apparent inheritance and being the age the main risk factor. The production and accumulation of amyloid-beta peptide in the central nervous system is a key event in the development of Alzheimer’s disease. This project is devoted to the synthesis of amyloid-beta ligands, fluorophores and blood brain barrier-transporters for diagnosis and therapy of Alzheimer’s disease. Different amyloid-beta ligands will be synthesized and their ability to interact with amyloid-beta plaques will be studied with nuclear magnetic resonance techniques and a process of lead optimization will be performed. Many natural and synthetic compounds able to interact as amyloid-beta ligands have been identified. Among them, a set of small molecules in which aromatic moieties seem to play a key role to inhibit amyloid-beta aggregation, in particular heteroaromatic polycyclic compounds such as tetracyclines. Nevertheless tetracyclines suffer from chemical instability, low water solubility and possess, in this contest, undesired anti-bacterial activity. In order to overcome these limitations, one of our goals is to synthesize tetracyclines analogues bearing a polycyclic structure with improved chemical stability and water solubility, possibly lacking antibacterial activity but conserving the ability to interact with amyloid-beta peptides. Known tetracyclines have in common a fourth cycle without an aromatic character and with different functionalisations. We aim to synthesize derivatives in which this cycle is represented by a sugar moiety, thus bearing different derivatisable positions or create derivatives in which we will increase or decrease the number of fused rings. In order to generate a potential drug-tool candidate, these molecules should also possess the correct chemical-physical characteristics. The glycidic moiety, not being directly involved in the binding, it assures further possible derivatizations, such as conjugation to others molecular entities (nanoparticles, polymeric supports, etc.), and functionalization with chemical groups able to modulate the hydro/lipophilicity. In order to be useful such compounds should perform their action within the brain, therefore they have to be able to cross the blood brain barrier, and to be somehow detected for diagnostic purposes.

Photodynamic inactivation of bacteria by cationic porphyrins : their cellular targets and potential environmental applications

Photodynamic inactivation (PDI) is defined as the process of cell destruction by oxidative stress resulting from the interaction between light and a photosensitizer (PS), in the presence of molecular oxygen. PDI of bacteria has been extensively studied in recent years, proving to be a promising alternative to conventional antimicrobial agents for the treatment of superficial and localized infections. Moreover, the applicability of PDI goes far beyond the clinical field, as its potential use in water disinfection, using PS immobilized on solid supports, is currently under study. The aim of the first part of this work was to study the oxidative modifications in phospholipids, nucleic acids and proteins of Escherichia coli and Staphylococcus warneri, subjected to photodynamic treatment with cationic porphyrins. The aims of the second part of the work were to study the efficiency of PDI in aquaculture water and the influence of different physicalchemical parameters in this process, using the Gram-negative bioluminescent bacterium Vibrio fischeri, and to evaluate the possibility of recycling cationic PS immobilized on magnetic nanoparticles. To study the oxidative changes in membrane phospholipids, a lipidomic approach has been used, combining chromatographic techniques and mass spectrometry. The FOX2 assay was used to determine the concentration of lipid hydroperoxides generated after treatment. The oxidative modifications in the proteins were analyzed by one-dimensional polyacrylamide gel electrophoresis (SDS-PAGE). Changes in the intracellular nucleic acids were analyzed by agarose gel electrophoresis and the concentration of doublestranded DNA was determined by fluorimetry. The oxidative changes of bacterial PDI at the molecular level were analyzed by infrared spectroscopy. In laboratory tests, bacteria (108 CFU mL-1) were irradiated with white light (4.0 mW cm-2) after incubation with the PS (Tri-Py+-Me-PF or Tetra-Py+-Me) at concentrations of 0.5 and 5.0 μM for S. warneri and E. coli, respectively. Bacteria were irradiated with different light doses (up to 9.6 J cm-2 for S. warneri and up to 64.8 J cm-2 for E. coli) and the changes were evaluated throughout the irradiation time. In the study of phospholipids, only the porphyrin Tri-Py+-Me-PF and a light dose of 64.8 J cm-2 were tested. The efficiency of PDI in aquaculture has been evaluated in two different conditions: in buffer solution, varying temperature, pH, salinity and oxygen concentration, and in aquaculture water samples, to reproduce the conditions of PDI in situ. The kinetics of the process was determined in realtime during the experiments by measuring the bioluminescence of V. fischeri (107 CFU mL-1, corresponding to a level of bioluminescence of 105 relative light units). A concentration of 5.0 μM of Tri-Py+-Me-PF was used in the experiments with buffer solution, and 10 to 50 μM in the experiments with aquaculture water. Artificial white light (4.0 mW cm-2) and solar irradiation (40 mW cm-2) were used as light sources.

Estudo dos processos eletroquímicos: eletrooxidação e eletrocoagulação

O tratamento físico-químico de águas residuais, de origem industrial, mais comum é o tratamento baseado na adição de coagulante e floculante a um efluente. No entanto, o tratamento eletroquímico é um tipo de tratamento que tem vindo a ser explorado e estudado com mais ênfase ao longo dos últimos anos. O tratamento eletroquímico é uma tecnologia AOP (Processos de Oxidação Avançada) e divide-se em eletrólise direta (oxidação e redução) e indireta (eletrocoagulação-flotação e eletrooxidação). A eletrocoagulação e eletrooxidação divergem apenas pelo tipo de reações que ocorrem, devido ao material que constitui os elétrodos. São processos complexos com uma multiplicidade de mecanismos que operam sinergicamente para remover poluentes da água. Tendo em conta a sua complexidade e ainda dificuldade de compreensão, existem na literatura diferentes versões acerca de quais os mecanismos chave, assim como diversas configurações geométricas de reatores e elétrodos. Atualmente, este tipo de tratamento tem vindo a evoluir, tornando-se num método economicamente viável para o tratamento de uma grande variedade de águas residuais, nomeadamente, aquelas que possuem compostos recalcitrantes na sua composição. O presente trabalho foi realizado nas instalações da VentilAQUA S.A. e, tendo em conta a sua área de especialidade, o trabalho exposto focou-se no desenvolvimento de soluções técnicas de AOP, nomeadamente na área eletroquímica (eletrocoagulação e eletrooxidação),para estudo dos parâmetros operacionais numa nova configuração geométrica para os elétrodos. Tendo por base os contributos da revisão bibliográfica, o estudo incidiu num reator tubular, com elétrodos de inox dispostos de forma concêntrica, à mesma distância entre si. Com este reator foram executados variados testes, com diferentes efluentes, que permitiram obter resultados operacionais de otimização de funcionamento, tendo em vista a remoção de poluentes. O estudo financeiro associado permitiu concluir que a eletrooxidação é significativamente mais económica que o tratamento físico-químico, nas condições operacionais e para os efluentes tratados. Relativamente ao Acompanhamento e Gestão de ETAR’s (Capítulo 4) foi possível verificar que todos os casos em estudo apresentam uma boa eficiência de remoção de matéria orgânica, permitindo a descarga do seu efluente com uma carga poluente que cumpre com os requisitos legais de descarga em meio hídrico.

Alkali-free bioactive glasses for bone regeneration

Bioactive glasses and glass-ceramics are a class of third generation biomaterials which elicit a special response on their surface when in contact with biological fluids, leading to strong bonding to living tissues. The purpose of the present study was to develop diopside based alkali-free bioactive glasses in order to achieve good sintering behaviour, high bioactivity, and a dissolution/ degradation rates compatible with the target applications in bone regeneration and tissue engineering. Another aim was to understand the structure-property relationships in the investigated bioactive glasses. In this quest, various glass compositions within the Diopside (CaMgSi2O6) – Fluorapatite (Ca5(PO4)3F) – Tricalcium phosphate (3CaO•P2O5) system have been investigated. All the glasses were prepared by melt-quenching technique and characterized by a wide array of complementary characterization techniques. The glass-ceramics were produced by sintering of glass powders compacts followed by a suitable heat treatment to promote the nucleation and crystallization phenomena. Furthermore, selected parent glass compositions were doped with several functional ions and an attempt to understand their effects on the glass structure, sintering ability and on the in vitro bio-degradation and biomineralization behaviours of the glasses was made. The effects of the same variables on the devitrification (nucleation and crystallization) behaviour of glasses to form bioactive glass-ceramics were also investigated. Some of the glasses exhibited high bio-mineralization rates, expressed by the formation of a surface hydroxyapatite layer within 1–12 h of immersion in a simulated body fluid (SBF) solution. All the glasses showed relatively lower degradation rates in comparison to that of 45S5 Bioglass®. Some of the glasses showed very good in vitro behaviour and the glasses co-doped with zinc and strontium showed an in vitro dose dependent behaviour. The as-designed bioactive glasses and glass–ceramic materials are excellent candidates for applications in bone regeneration and for the fabrication of scaffolds for tissue engineering.

Metais em plantas e algas : acumulação e potencial aplicação em processos de remediação

The present work reports the study of the bioaccumulation of potentially toxic elements (cadmium, lead and mercury) by marine macroalgae (Ulva lactuca, Fucus vesiculosus and Gracilaria gracilis), abundant in the coast and estuarine systems worldwide. These organisms proved to be capable of withstanding moderate multi-metallic contamination (environmentally relevant concentrations), incorporating high amounts of metal in their tissues. The high removal percentages achieved, in particular for mercury (99%), demonstrate the potential of these algae as a basis for a new biotechnological treatment of saline waters contaminated with metals (more efficient, cost-effective and environmentally friendly than conventional methods). U. lactuca was considered the most promising due to the better performance presented. The comparison between the bioaccumulation and biosorption processes suggested that in some cases the use of the living organism will have advantages over the application of biomass, due to the simplicity of the overall process, and the lower residual concentration of metal achieved in the solution (especially for Cd). The transfer and accumulation of Hg by terrestrial plants (Brassica juncea and Lolium perenne) in agricultural fields near a contaminated industrial area was also studied. Despite the low bioaccumulation factors found (<1), there were high Hg content in plants (up to 84 mg kg-1 in roots and up 6.9 mg kg-1 in shoots, dry weight). Daily intake estimates for grazing animals (cows and sheep) pointed to the potential risk to human health derived from consumption of their meat. The results highlighted the important role that plants and algae may have in protection, risk assessment and remediation of environmental systems contaminated with metals.

Treatment of aqueous effluents contaminated with ionic liquids

Ionic liquids are a class of solvents that, due to their unique properties, have been proposed in the past few years as alternatives to some hazardous volatile organic compounds. They are already used by industry, where it was possible to improve different processes by the incorporation of this kind of non-volatile and often liquid solvents. However, even if ionic liquids cannot contribute to air pollution, due to their negligible vapour pressures, they can be dispersed thorough aquatic streams thus contaminating the environment. Therefore, the main goals of this work are to study the mutual solubilities between water and different ionic liquids in order to infer on their environmental impact, and to propose effective methods to remove and, whenever possible, recover ionic liquids from aqueous media. The liquid-liquid phase behaviour of different ionic liquids and water was evaluated in the temperature range between (288.15 and 318.15) K. For higher melting temperature ionic liquids a narrower temperature range was studied. The gathered data allowed a deep understanding on the structural effects of the ionic liquid, namely the cation core, isomerism, symmetry, cation alkyl chain length and the anion nature through their mutual solubilities (saturation values) with water. The experimental data were also supported by the COnductor-like Screening MOdel for Real Solvents (COSMO-RS), and for some more specific systems, molecular dynamics simulations were also employed for a better comprehension of these systems at a molecular level. On the other hand, in order to remove and recover ionic liquids from aqueous solutions, two different methods were studied: one based on aqueous biphasic systems, that allowed an almost complete recovery of hydrophilic ionic liquids (those completely miscible with water at temperatures close to room temperature) by the addition of strong salting-out agents (Al2(SO4)3 or AlK(SO4)2); and the other based on the adsorption of several ionic liquids onto commercial activated carbon. The first approach, in addition to allowing the removal of ionic liquids from aqueous solutions, also makes possible to recover the ionic liquid and to recycle the remaining solution. In the adsorption process, only the removal of the ionic liquid from aqueous solutions was attempted. Nevertheless, a broad understanding of the structural effects of the ionic liquid on the adsorption process was attained, and a final improvement on the adsorption of hydrophilic ionic liquids by the addition of an inorganic salt (Na2SO4) was also achieved. Yet, the development of a recovery process that allows the reuse of the ionic liquid is still required for the development of sustainable processes.

Structural characterization and biological activity of polysaccharides from infusions used in the popular tradition

The use of plants with medicinal purposes is an ancient practice still very common in developing regions, and is rapidly spreading in industrialized countries. This fact is evidenced by the large number of ethnobotanical studies found in the literature referring that these plants are often used as decoctions and infusions. In most studies the reported biological activities are attributed to the presence of phenolic compounds, due to their antioxidant properties, and to polysaccharides, with its anti-tumoral properties. In “Trás-os-Montes” region, some of the most popular infusions used by the popular medicine are prepared with the dried leaves of Fraxinus angustifolia, the dried shoots of Mentha suaveolens, and the dried inflorescences of Pterospartum tridentatum. However, there are no studies about the polysaccharides present in these infusions. Thus, through the structural characterization of the polysaccharides present in the infusions of F. angustifolia, M. suaveolens, and P. tridentatum, the present PhD thesis intends to evaluate the possible relation between polysaccharides and the immunostimulatory activity that these infusions might present. In a preliminary phase, infusions of F. angustifolia were prepared according to the popular tradition, and it was observed that the obtained water soluble material contained approximately 85% of material non-retained in C18 cartridges, with hydrophilic characteristics, with the remaining 15% comprising retained-material with hydrophobic characteristics. It was also shown that the infusions only contained between 2 and 4% of high molecular weight material (HMWM), which comprised approximately 30% of carbohydrate material. Sugar and methylation analysis of the HMWM suggested the presence of pectic polysaccharides, together with type II arabinogalactans, mannans, and xyloglucans. However, the amount of material obtained is to low for the fractionation, and structural analysis of the polysaccharides present. The 4 h decoction, divided in two periods of 2 h, with water renewal, allowed to increase the HMWM yield, relatively to the infusions traditional infusions. It was also observed that the decoction also allowed to increase the HMWM proportion of carbohydrate material, due to an increase in the proportion of uronic acid present, although the neutral sugar residues seemed to be detected in similar proportions. Therefore, in all the experiments subsequently performed, the HMWM used was obtained through the decoction of F. angustifolia dried leaves, M. suaveolens dried shoots, and P. tridentatum dried inflorescences. x After the fractionation, through ethanol precipitation, and anion exchange chromatography, of the polysaccharides from the HMWM obtained by the decoction of the vegetable material of the distinct studied plants, it was observed the presence of high proportions of pectic polysaccharides, containing type I arabinogalactans, together with minor proportions of type II arabinogalactans, mannans, and xyloglucans. The presence of pectic polysaccharides in the extracts from F. angustifolia was also evidenced through endo-polygalacturonase treatment, and ESI-MS and ESI-MS/MS experiments. The detection of linked pentose and uronic acid residues, also seemed to suggest the presence of xylogalacturonan domains in the pectic polysaccharides from F. angustifolia. The extracts from F. angustifolia dried leaves also contained type II arabinogalactans that exhibited a higher structural diversity than those detected in the M. suaveolens, and P. tridentatum extracts, particularly in the substitution degree of the galactan backbone, and in the extension of the (1→5)-Araf side chains. Moreover, for all the plants studied, it was also observed that the type II arabinogalactans, extracted during the 2nd 2h of the extraction process, exhibited a substitution degree of the galactan backbone higher than those extracted during the 1st 2h. The extracts from P. tridentatum dried inflorescences contained higher proportions of mannans, and also of xyloglucans, both presenting a substitution degree higher than those, which were detected in lower proportion in the extracts of F. angustifolia and M. suaveolens. Through ESI-MS and ESI-MS/MS it was possible to evidence that the mannans present in the extracts of P. tridentatum presented acetyl groups on the O-2 of the mannosyl residues. It was also evidenced that the P. tridentatum mannans were more extensively acetylated than the mannans detected in the coffee infusion, LBG, and other non-conventional mannan sources. Moreover, it was detected the presence of oligosaccharides comprising hexose residues linked to non acetylated pentose residues, suggesting the possible presence of arabinose residues in the mannans from P. tridentatum extracts. The immunostimulatory activity of three fractions isolated from the extracts of F. angustifolia, M. suaveolens, and P. tridentatum, was tested and an increase in the NO production by macrophages, without compromising their cellular viability, was observed. The type I, and type II arabinogalactans detected in the extracts from F. angustifolia, and M. suaveolens seem to have contributed for the observed immunostimulatory activity. For the fraction from P. tridentatum, the mannans acetylation, and the presence of type I, and type II arabinogalactans seemed to contribute for the macrophage immunostimulatory activity observed. The possible presence of storage xyloglucans from the inflorescences seeds, also seems to have contributed for the immunostimulatory activity registered when the macrophages were stimulated with higher extract concentrations. The results obtained allow to conclude that the extracts of F. angustifolia dried leaves, M. suaveolens dried shoots, and P. tridentatum dried inflorescences contained high proportions of pectic polysaccharides, exhibiting type I arabinogalactans, together with other polysaccharides, such as type II arabinogalactans, mannans, and xyloglucans. This polysaccharide mixture seems to have contributed to the immunostimulatory activity of fractions isolated from the extracts of the studied plants. Therefore, as the same type of polysaccharides seem to be present in the decoctions and in the infusions, it seems possible that the polysaccharides might contribute for the therapeutic properties frequently associated by the popular tradition to the infusions of these plants.

Resistance to last-resort antibiotics in natural environments

Last-resort antibiotics are the final line of action for treating serious infections caused by multiresistant strains. Over the years the prevalence of resistant bacteria has been increasing. Natural environments are reservoirs of antibiotic resistance, highly influenced by human-driven activities. The importance of aquatic systems on the evolution of antibiotic resistance is highlighted from the assumption that clinically-relevant resistance genes have originated in strains ubiquitous in these environments. We hypothesize that: a) rivers are reservoirs and disseminators of antibiotic resistance; b) anthropogenic activities potentiate dissemination of resistance to last-resort antibiotics. Hence, the main goal of the work is to compare the last-resort antibiotics resistome, in polluted and unpolluted water. Rivers from the Vouga basin, exposed to different anthropogenic impacts, were sampled. Water quality parameters were determined to classify rivers as unpolluted or polluted. Two bacterial collections were established enclosing bacteria resistant to cefotaxime (3rd generation cephalosporin) and to imipenem (carbapenem). Each collection was characterized regarding: phylogenetic diversity, antibiotic susceptibility, resistance mechanisms and mobile genetic elements. The prevalence of cefotaxime- and imipenem-resistant bacteria was higher in polluted water. Results suggested an important role in the dissemination of antibiotic resistance for Enterobacteriaceae, Pseudomonas and Aeromonas. The occurrence of bacteria resistant to non-beta-lactams was higher among isolates from polluted water as also the number of multiresistant strains. Among strains resistant to cefotaxime, extended-spectrum beta-lactamase (ESBL) genes were detected (predominantly blaCTX-M-like) associated to mobile genetic elements previously described in clinical strains. ESBL-producers were often multiresistant as a result of co-selection mechanisms. Culture-independent methods showed clear differences between blaCTX-M-like sequences found in unpolluted water (similar to ancestral genes) and polluted water (sequences identical to those reported in clinical settings). Carbapenem resistance was mostly related to the presence of intrinsically resistant bacteria. Yet, relevant carbapenemase genes were detected as blaOXA-48-like in Shewanella spp. (the putative origin of these genes), and blaVIM-2 in Pseudomonas spp. isolated from polluted rivers. Culture-independent methods showed an higher than the previously reported diversity of blaOXA-48-like genes in rivers. Overall, clear differences between polluted and unpolluted systems were observed, regarding prevalence, phylogenetic diversity and susceptibility profiles of resistant bacteria and occurrence of clinically relevant antibiotic resistance genes, thus validating our hypotheses. In this way, rivers act as disseminators of resistance genes, and anthropogenic activities potentiate horizontal gene transfer and promote the constitution of genetic platforms that combine several resistance determinants, leading to multiresistance phenotypes that may persist even in the absence of antibiotics.

Assessing the effectiveness of chemical treatment with nanomaterials in improving the quality of different industrial effluents

Industrial activities are the major sources of pollution in all environments. Depending on the type of industry, various levels of organic and inorganic pollutants are being continuously discharged into the environment. Although, several kinds of physical, chemical, biological or the combination of methods have been proposed and applied to minimize the impact of industrial effluents, few have proved to be totally effective in terms of removal rates of several contaminants, toxicity reduction or amelioration of physical and chemical properties. Hence, it is imperative to develop new and innovative methodologies for industrial wastewater treatment. In this context nanotechnology arises announcing the offer of new possibilities for the treatment of wastewaters mainly based on the enhanced physical and chemical proprieties of nanomaterials (NMs), which can remarkably increase their adsorption and oxidation potential. Although applications of NMs may bring benefits, their widespread use will also contribute for their introduction into the environment and concerns have been raised about the intentional use of these materials. Further, the same properties that make NMs so appealing can also be responsible for producing ecotoxicological effects. In a first stage, with the objective of selecting NMs for the treatment of organic and inorganic effluents we first assessed the potential toxicity of nanoparticles of nickel oxide (NiO) with two different sizes (100 and 10-20 nm), titanium dioxide (TiO2, < 25 nm) and iron oxide (Fe2O3, ≈ 85x425 nm). The ecotoxicological assessment was performed with a battery of assays using aquatic organisms from different trophic levels. Since TiO2 and Fe2O3 were the NMs that presented lower risks to the aquatic systems, they were selected for the second stage of this work. Thus, the two NMs pre-selected were tested for the treatment of olive mill wastewater (OMW). They were used as catalyst in photodegradation systems (TiO2/UV, Fe2O3/UV, TiO2/H2O2/UV and Fe2O3/H2O2/UV). The treatments with TiO2 or Fe2O3 combined with H2O2 were the most efficient in ameliorating some chemical properties of the effluent. Regarding the toxicity to V. fischeri the highest reduction was recorded for the H2O2/UV system, without NMs. Afterwards a sequential treatment using photocatalytic oxidation with NMs and degradation with white-rot fungi was applied to OMW. This new approach increased the reduction of chemical oxygen demand, phenolic content and ecotoxicity to V. fischeri. However, no reduction in color and aromatic compounds was achieved after 21 days of biological treatment. The photodegradation systems were also applied to treat the kraft pulp mill and mining effluents. For the organic effluent the combination NMs and H2O2 had the best performances in reduction the chemical parameters as well in terms of toxicity reduction. However, for the mine effluent the best (TiO2/UV and Fe2O3/UV) were only able to significantly remove three metals (Zn, Al and Cd). Nonetheless the treatments were able of reducing the toxicity of the effluent. As a final stage, the toxicity of solid wastes formed during wastewater treatment with NMs was assessed with Chironomus riparius larvae, a representative species of the sediment compartment. Certain solid wastes showed the potential to negatively affect C. riparius survival and growth, depending on the type of effluent treated. This work also brings new insights to the use of NMs for the treatment of industrial wastewaters. Although some potential applications have been announced, many evaluations have to be performed before the upscaling of the chemical treatments with NMs.

Photodegradation of sertraline by solar radiation and influencing factors

Photodegradation is considered to be one of the most important processes of elimination of pharmaceutical drugs from natural water matrices. The high consumption and discharge of these substances, in particular antidepressants, to the aquatic environment supports the need to study degradation processes. This dissertation aimed at studying the direct and indirect photodegradation of sertraline, an antidepressant known for its persistence in the environment, and the evaluation of the influence of environmentally relevant factors in its photodegradation. The photodegradation experiments were developed under simulated solar light and the irradiation times converted to summer sunny days (SSD), an equivalent time in natural environmental conditions. The direct photodegradation was evaluated in solutions of sertraline prepared in ultrapure water and the indirect photodegradation was studied through the addition of photosensitizers (humic substances, Fe(III), nitrates and oxygen). Further irradiation studies were perfomed in aqueous samples collected from two wastewater treatment plants, Vouga river and Ria de Aveiro. The samples were chemically characterized (dissolved organic carbon, nitrates and nitrites and iron determination and UV/Vis spectroscopy). The quantification of sertraline was done by HPLC-UV and photoproducts from direct photodegradation were identified by electrospray mass spectrometry. An observed direct photodegradation rate of sertraline of 0.0062 h-1 was determined, corresponding to a half-life time of 111 h (equivalent to 29 SSD). A significant influence of photosensitizers was observed, the best results being achieved in irradiations of sertraline with humic acids, obtaining a half-life time of 12 h. This was attributed to the hydrophobicity of this substance and higher absortivity in the UV/Vis wavelength, which promote processes of indirect photodegradation. The degradation of sertraline in natural samples was also enhanced comparatively to the direct photodegradation, achieving half-life times between 10 and 25h; the best results were achieved in samples from the primary treatment of a wastewater treatment plant and Ria de Aveiro, with half-life times of 10 and 16 h, respectively. A total of six photoproducts formed during the direct photodegradation of sertraline were identified, three of which were not yet identified in the literature. The main factors contributing to the degradation of sertraline were analysed but this was not fully accomplished, requiring further studies of the composition of the natural matrices and the combined influence of distinct photosensitizers during the irradiation. Nevertheless, it was concluded that the photodegradation of sertraline is greatly influenced by indirect photodegradation processes, promoted by the presence of photosensitizers.

Modelação da qualidade microbiológica da água na Ria Formosa

Este estudo integra-se numa avaliação hidrodinâmica e monitorização microbiológica da qualidade da água da Ria Formosa. A monitorização foi implementada pela DRAOT Algarve com a colaboração da EST, da FCMA e do IST. A metodologia utilizada consiste na aplicação de um modelo matemático para simulação das variáveis hidrodinâmicas e da qualidade da água. Utilizam-se como traçadores os coliformes fecais (CF), considerados indicadores de contaminação fecal pelo Dec-Lei 236/98 de 1 de Agosto, relativo à qualidade de águas do litoral e salobras para fins aquícolas- águas conquícolas. As águas da ria são usadas para cultura de diversas espécies conquícolas de bivalves. Estes são organismos que filtram e retêm no seu interior material particulado existente em suspensão na água tais como os CF entre outros microorganismos presentes na água. Para avaliar a concentração de coliformes nos bivalves e gastrópodes foi desenvolvido um modelo que simula a bioacumulação desta propriedade por parte do bivalve. Da sua aplicação permite classificar a Ria em várias classes conforme o estabelecido no Dec. Lei nº 293/98 de 18 de Setembro.

O ensaio pressiométrico: tratamento e interpretação dos resultados do ensaio

Este artigo vem no seguimento de um trabalho anteriormente apresentado, designado por “O ensaio pressiométrico: Metodologia de Ensaio e Calibração do Equipamento”, pretendendo-se agora fornecer as bases para a interpretação dos resultados que dele provêm. No entanto, adverte-se desde já, para o facto de que estes carecem de correcção antes de serem utilizados para qualquer outro fim.