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Effect of the metallic cleaning and oxidizing pre-treatments on the corrosion behaviour of sol-gel hybrid coated EN AW-6063 alloy
No full textThe effect of alloy surface pre-treatments on the corrosion behaviour of sol gel hybrid coated EN AW 6063 alloy was studied. Five pre-treatments were used: solvent degreasing; alkaline degreasing followed by acid etching; alkaline degreasing followed by alkaline plus acid etching, alkaline degreasing followed by acid etching and oxide growth in boiling water and alkaline degreasing followed by acid etching and anodization. Surface morphology depends on the pre-treatment: SEM/EDS analysis revealed that alkaline plus acid cleaned samples exhibited a very smooth deoxidized surface, while all the others showed a rougher surface covered with an oxide layer. This oxide layer is denser and more homogeneous in the samples subjected to the oxide growth steps. A hybrid sol-gel coating, synthesized from glycidoxypropyltrimethoxysilane (GPTMS) and zirconium n-propoxide (TPOZ) precursors, was applied to the different pre-treated metallic substrate by dip-coating. The corrosion behaviour of the coated samples was evaluated by Electrochemical Impedance Spectroscopy (EIS) and by an accelerated corrosion test. Complementarily to the corrosion study, the adhesion of the hybrid sol-gel coating was evaluated by cross-cut and bend tests. The corrosion tests revealed that the pre-treatments including the oxide growth steps lead to the best protection performance, followed by the alkaline degreasing and alkaline plus acid etching one. However, the latter exhibits the worst adhesive behaviour, attributed to the smoother and deoxidized surface of the substrate.38-43pp33, Nº 3 (2014)DM/NMMCorros. Prot. Mater
Impact of slurry management strategies on potential leaching of nutrients and pathogens in a sandy soil amended withc attle slurry
No full textFor farmers, management of cattle slurry (CS) is now a priority, in order to improve the fertilizer value of the slurry and simultaneously minimize its environmental impact. Several slurry pre-treatments and soil application methods to minimize ammonia emissions are now available to farmers, but the impact of such management strategies on groundwater is still unclear. A laboratory experiment was performed over 24 days in controlled conditions, with undisturbed soil columns (sandy soil) in PVC pipes (30 cm high and 5.7 cm in diameter). The treatments considered (4 replicates) were: a control with no amendment (CTR), injection of whole CS (WSI), and surface application of: whole CS (WSS), acidified (pH 5.5) whole CS (AWSS), the liquid fraction obtained by centrifugation of CS (LFS), and acidified (pH 5.5) liquid fraction (ALFS). An amount of CS equivalent to 240 kg N ha}1 was applied in all treatments. The first leaching event was performed 72 h after application of the treatments and then leaching events were performed weekly to give a total of four irrigation events (IEs). All the leachates obtained were analyzed for mineral and organic nitrogen, electrical conductivity (EC), pH, total carbon, and phosphorus. Total coliforms and Escherichia coli were also quantified in the leachates obtained in the first IE.
The results show that both acidification and separation had significant effects on the composition of the leachates: higher NO3- concentrations were observed for the LFS and ALFS relative to all the other treatments, throughout the experiment, and lower NO3- concentrations were observed for acidified relative to non-acidified treatments at IE2. Acidification of both the LF and WS led to higher NH4+ concentrations as well as an increase of EC for treatment ALFS relative to the control, in the first IE, and lower pH values in the AWSS. Furthermore, the E. coli and total coliform concentrations in AWSS, LFS, and ALFS were significantly higher than in WSI or WSS. In conclusion, none of the strategies generally used to minimize ammonia emissions impact positively on leaching potential relative to the traditional surface application of CS. Furthermore, some treatments, such as separation, might increase significantly the risk of leaching.8 pDisponível online em:journal homepage:www.elsevier.com/locate/jenvman146DHA/NESJournal of Environmental Managemen
Local scour at single piers revisited
No full textThe paper summarizes recent contributions of the authors on the effects of relative flow depth,
relative sand size, time and fluid viscosity, on the scour depth at single piers. These contributions
rely on unique experiments in the sense that they are systematically longer than the vast majority
of those found in the literature. The characterization of the effects of relative sand size and time is
further improved as compared with existing literature while the effect of the relative flow depth
confirms previous findings. New predictors are suggested. Viscous effects conveyed by the
approach flow seem non-negligible; this is a new contribution that deserves further research.ISBN 978-989-96479-2-3DHA/NRE201414 a 16 de anri
Salt damage risk prediction for porous limestone
No full textWe present a model coupling heat, moisture and salt transport, salt crystallization, deformation and damage in porous building materials with the aim of predicting crystallization-induced damage. The model performance is illustrated by simulating the damage caused by sodium chloride crystallization in a porous limestone. The results are compared with experimental observations based on neutron and X-ray imaging,
showing a good agreement. The effective stresses that can cause damage are the result of the crystallization pressure combined with a sufficient amount of precipitating salt crystals in a localized zone.49-59ppSeminário / SWBSS 2014 - 3rd International Conference on Salt Weathering of Buildings and Stone SculpturesDM/NBP
Dinâmica de trocas entre a Ria Formosa e o oceano: modelação numérica do transporte de matéria em suspensão
No full textPretende-se compreender a dinâmica de trocas de nutrientes, clorofila e material particulado entre a Ria Formosa e o oceano, e a influência dos principais forçamentos (e.g. maré) nesta dinâmica. A influência dos
forçamentos ambientais na dinâmica de trocas Ria ± oceano foi estudada com um modelo hidrodinâmico (SELFE) e um de transporte (VELApart). Foram simulados diversos cenários de vento, batimetria e descarga de efluentes de estações de tratamento de águas residuais. Os resultados sugerem uma influência significativa do vento e da batimetria na exportação de matéria em suspensão para o exterior da Ria a escalas temporais curtas. O local de descarga dos efluentes das estações de tratamento de águas residuais combinado com o efeito da maré influencia a distribuição espacial da massa no interior da Ria e os tempos de exportação para o exterior. Os padrões de transporte estimados podem contribuir para melhorar a gestão da Ria Formosa.221-224ppDHA/NEC201424 a 26 de junh
A cross-scale numerical modeling system for management support of oil spill accidents
No full textA flexible 2D/3D oil spill modeling system addressing the distinct nature of the surface and water column
fluids, major oil weathering and improved retention/reposition processes in coastal zones is presented.
The system integrates hydrodynamic, transport and oil weathering modules, which can be combined
to offer different-complexity descriptions as required by applications across the river-to-ocean continuum.
Features include accounting for different composition and reology in the surface and water column
mixtures, as well as spreading, evaporation, water-in-oil emulsification, shoreline retention, dispersion
and dissolution. The use of unstructured grids provides flexibility and efficiency in handling spills in complex
geometries and across scales. The use of high-order Eulerian–Lagrangian methods allows for computational
efficiency and for handling key processes in ways consistent with their distinct mathematical
nature and time scales. The modeling system is tested through a suite of synthetic, laboratory and realistic-
domain benchmarks, which demonstrate robust handling of key processes and of 2D/3D couplings.
The application of the modeling system to a spill scenario at the entrance of a port in a coastal lagoon
illustrates the power of the approach to represent spills that occur in coastal regions with complex
boundaries and bathymetry.132-147ppVolume 80, Issues 1–2DHA/NECMarine Pollution Bulleti
Calibração de modelos de inundação com imagens de radar de abertura sintética (SAR) no baixo Tejo
No full textAs cheias constituem 40% de todos os desastres naturais mundiais e, na última década do século XX, foram responsáveis pela perda de 100 mil vidas humanas, afetando mais de 1400 milhões de pessoas. Nos últimos cem anos têm sido o fenómeno natural mais mortífero em Portugal, sendo o Baixo Tejo o local onde ocorrem as maiores cheias em termos de área inundada, com intervalo médio de 2,5 anos. A elevada frequência de cheias torna o Baixo Tejo adequado como região piloto para um trabalho sistemático de calibração de modelos de inundação. Este artigo centra-se na calibração de modelos 2D de simulação de cheias para eventos de 2001 e 2006, no troço de 70 km do Rio Tejo entre Tramagal e Ómnias, recorrendo ao modelo numérico Tuflow, que resolve as equações bidimensionais de superfície livre em águas pouco profundas.
Os modelos de inundação foram baseados num modelo digital de terreno (MDT) adquirido em 2008 por técnicas de radar (resolução espacial de 5 m), em medições in situ de nível de água em Ómnias (condição-fronteira a jusante) e no caudal em Tramagal e Zêzere (condições-fronteira a montante). Cinco diques foram introduzidos nos modelos. Todos os modelos têm as mesmas condições-fronteira e resolução da malha de 30 m. Um estado estacionário inicial foi garantido. Utilizaram-se classes de ocupação do solo CORINE Land Cover 2006, combinadas com coeficientes de rugosidade obtidos na literatura.
Mapas de inundação obtidos a partir da segmentação de imagens de radar de abertura sintética (SAR) nas classes água/terra permitiram a calibração dos modelos para as cheias de 2001 e 2006. Estes mapas foram comparados com os mapas de inundação simulados e os coeficientes de Manning (rugosidade) foram alterados em conformidade. Os modelos foram também calibrados pelo nível de água medido na estação hidrométrica de Almourol, a 12 km a jusante de Tramagal. Obtiveram-se, assim, mapas de coeficientes de rugosidade. E foi efetuada uma simulação para a maior cheia do século XX (fevereiro de 1979), para a qual não existe imagem de radar de abertura sintética; neste caso, a validação do modelo foi feita usando os valores de nível de água na estação de Almourol e as marcas de cheia distribuídas pela planície de inundação.
As imagens de radar de abertura sintética foram fornecidas pela Agência Espacial Europeia ao abrigo do projeto CAT–1, n.º 9441. Este estudo foi desenvolvido no âmbito do projeto RIVERSAR – “Exploração de Imagens SAR para Aperfeiçoar Modelos de Inundação no Rio Tejo” (PTDC/CTE-GIX/099085/2008), financiado pela FCT. Os resultados foram entregues à Agência Portuguesa do Ambiente, parceira do projeto, no âmbito da implementação em Portugal da Diretiva Europeia 2007/60/EC, refletindo a importância deste tipo de estudos na Geodecisão.7pDBB/NG
Avaliação da qualidade posicional. Aplicação a um levantamento realizado em Coimbra utilizando VANT
No full textA utilização de VANT (Veículos Aéreos Não Tripulados) como plataformas para a obtenção de fotografias destinadas à aquisição de informação geográfica tem despertado um interesse crescente por poder ser, em certos domínios, uma alternativa interessante aos métodos aéreos tradicionais. Na comunicação é apresentado o controlo da qualidade de um ortomosaico e de um modelo digital de superfície de uma zona central de Coimbra seguindo duas metodologias de análise: a habitual, baseada na análise da estatística “erro médio quadrático” e uma complexa que envolve métodos de inferência estatística.
Concluiu-se que um ortofotomapa ou uma planta, produtos com grande escala (pois é nesta área que se integram os ortomosaicos produzidos pelos VANT da gama dos utilizados em Coimbra), produzidos a partir de fotografias recolhidas por equipamento fotogramétrico de elevada qualidade, numa plataforma altamente estável e com equipamento de posicionamento muito preciso, complementados com edição rigorosa são elementos de suporte, que se considera insubstituíveis em diversas atividades de gestão do território. No entanto, para trabalhos de atualização, planeamento ou verificação, um ortomosaico e a nuvem de pontos produzidos pelos VANT são fontes de informação que, localmente, em áreas mais restritas, podem incluir informação mais completa e nalguns casos até mais rigorosa que a obtida a partir de métodos clássicos de produção cartográfica.20pDBB/NG
Levantamento térmico de paramentos de barragens de betão para apoio ao acompanhamento da evolução de patologias
No full textAs câmaras termográficas, também designadas por câmaras de infravermelho ou simplesmente câmaras térmicas, formam uma imagem do objeto “fotografado” com base na radiação infravermelha incidente. Podem assim ser utilizadas na monitorização de estruturas desde que o fenómeno que se quer detetar tenha reflexos na temperatura superficial da estrutura. No caso das barragens de betão, um levantamento térmico do paramento, que pode ser realizado em poucos minutos e sem exigências especiais, permite detetar variações da temperatura superficial do betão o que possibilita a deteção de zonas de repasses de água, em geral associadas à existência de fendas. Se o levantamento for efetuado de forma regular e desde o início da obra, a deteção pode ser feita precocemente, antes do aparecimento de depósitos de carbonatos à superfície. Na presente comunicação apresenta-se o resultado da avaliação da aplicabilidade deste método na deteção de repasses em barragens de betão com base nos levantamentos térmicos do paramento de jusante de três barragens.2215DBB/NGA201426 a 28 de novembr
Deliverable 4.3.5 Real-time monitoring and forecast platform to support early warning of faecal contamination in recreational waters
No full textEste registo pertence ao Repositório Científico do LNECControlling urban floods and managing direct discharges of effluents into
receiving waters from combined sewer overflows (CSO) are two major
challenges faced by urban water management utilities. Discharges from large
cities can have significant environmental impacts on marginal water bodies,
affecting the quality of life in general, and recreational activities in particular
(Marsalek and Rochfort, 2004; David and Matos, 2005; Passerat et al., 2011).
These impacts can be exacerbated by climate change. First, the growing
magnitude and frequency of extreme precipitation events (Groisman et al.,
2005; Frei et al., 2006) will increase the number and severity of the discharges.
Secondly, sea level rise and the resulting increase of salinity intrusion into the
sewers can degrade the performance of wastewater infrastructures, affecting
gate and pump operations and advanced biological wastewater treatment
procedures.
The ability to jointly manage an entire urban drainage and treatment system,
towards an efficient and environmental-friendly operation of these
infrastructures in a climate-change context, is often limited by the lack of
reliable real-time information. Existing information systems are frequently
devoted to specific parts of the network, lacking synoptic and cross-domain
data. In addition, data and prediction tools are usually focused on physical
variables alone. Water quality information is, at best, supported by very
simple modelling approaches and limited sensors. More often, this
information is sparse and not organized to provide efficient command and
control procedures, taking into account climate change effects in the various
domains.
Timely prediction and monitoring of environmental conditions, as well as
anticipation of hazardous events, are essential parts of recreational waters
management. Monitoring and forecasting platforms can provide the necessary
information for safe and efficient economic activities, and the protection of
valuable natural assets, including the preservation of ecosystems and
recreational areas.
To this end, an innovative, real-time, coupled urban and estuarine platform
was developed to support the integrated water quality management of
wastewater systems, from the upstream catchment to the receiving waters.
The platform efficiently integrates the monitoring and modelling of the
different physical and water quality processes from the catchment to the
receiving waters, at the appropriate spatial and temporal scales. It provides
real-time web access to on-line hydrodynamic and water quality monitoring
networks and short-term model predictions, based on a coupled modelling
system that includes relevant interactions between the urban drainage system
and the receiving waters, automatically compared with available on-line
network data. This innovative decision support tool for urban drainage
systems management is organized to provide tailor-made, automatic services
to support the major operation tasks, drilled-down to the necessary details for
decision support.The forecasting engine behind the platform provides hydrodynamic and
faecal contamination predictions in all components of the systems (drainage
network, wastewater treatment plant and estuary), accounting for all
interactions between them. Prediction models are forced by regional forecasts
whenever possible, and by real-time data otherwise. The accuracy of the
predictions is verified through continuous, automatic comparison with data
from the innovative on-line monitoring network, including both physical and
water quality sensors (Rodrigues et al., 2014).
Based on the platform’s data and model forecasts, an early-warning system is
being proposed, supported by alert triggers both on the sewer network
information and estuarine conditions. The system is being applied to the
Lisbon demo, accounting for the impact of the combined sewage outfall from
the Alcântara catchment on the Tagus estuary (David et al., 2014).F9P18DHA/GT