Curriculum Vitae

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  1. M.L. Dinis, A. Fiúza, “Occupational Exposure During Remediation Work At A Uranium Tailings Pile”, Environmental Radioactivity, Under Publication

  1. A. Fiúza, A. Silva, G. Carvalho, A.V. de la Fuente, C. Delerue-Matos, “Heterogeneous kinetics of the reduction of chromium (VI) by elemental iron”, Journal of Hazardous Materials 175 (2010) 1042–1047; DOI:

Zero valent iron (ZVI) has been extensively used as a reactive medium for the reduction of Cr(VI) to Cr(III) in reactive permeable barriers. The kinetic rate depends strongly on the superficial oxidation of the iron particles used and the preliminary washing of ZVI increases the rate. The reaction has been primarily modelled using a pseudo-first-order kinetics which is inappropriate for a heterogeneous reaction. We assumed a shrinking particle type model where the kinetic rate is proportional to the available iron surface area, to the initial volume of solution and to the chromium concentration raised to a power˛ which is the order of the chemical reaction occurring at surface. We assumed ˛= 2/3 based on the likeness to the shrinking particle models with spherical symmetry. Kinetics studies were performed in order to evaluate the suitability of this approach. The influence of the following parameters was experimentally studied: initial available surface area, chromium concentration, temperature and pH. The assumed order for the reaction was confirmed. In addition, the rate constant was calculated from data obtained in different operating conditions. Digital pictures of iron balls were periodically taken and the image treatment allowed for establishing the time evolution of their size distribution.

  1. António M.A. Fiúza, Aurora Silva, “Tecnologías In-Situ de Remoción del Arsénico: Análisis Crítica”, Comunicação na Conferência Arsenic Removal Technologies, Montevideo, October, 2009

Only in the last decade the in-situ technologies for the removal of arsenic from groundwater begun to be considered as a viable option in relation to the ex-situ processes, with pumping and treatment, known and used for many years.

Permeable reactive barriers (PRB) consist in walls, intercepting the aquifer, built with a higher hydraulic conductivity, where a reactive compound that can transform and retain the arsenic, is inserted together with an inert medium (generally sand) providing for permeability. Four basic types of barriers were developed for the arsenic. They distinguish by the active reactant used as well as by the corresponding mechanisms of in-situ fixation: barriers with a sorbent (for instance, activated alumina), with zero valent iron, with different types of slags and multifunctional barriers constituted by a section of a compost-based material followed by a second section based on elemental iron.

Electrokinetics is an in-situ technology that is based on the application of low density electric currents between electrodes inserted in the soil, mobilizing the arsenic in an ionic form that moves towards the anode. Coupled technologies have also been tested such as an electrokinetic process coupled with a PRB.

In-situ chemical oxidation, or in-situ chemical fixation, normally consists on the direct injection in the subsoil of an oxidant (normally potassium permanganate or oxygen) that promotes the oxidation of arsenic (III) to V followed by its co-precipitation with iron (ferric) oxides. Other alternatives have been tested using other reactants, or combination of reactants, such as FeSO4 and CaCO3.

  1. Maria de Lurdes Dinis, António Fiúza, Occupational Exposure During Remediation Works at a Uranium mining Pile, IAEA, Viena. Proceedings of the International Conference on Remediation of Land Contaminated by Radioactive Material Residues, May 2009, Astana, Kazakhstan. Em publicação.

The aim of this study is to assess the occupational exposure at an abandoned uranium mining site due to work activities involving tailings pile remediation. A hypothetical scenario has been created in which the workers involved in the remediation activities are exposed to radiation through internal and external pathways. The results indicate that occupational radiation doses may reach a significant fraction of occupational radiation protection limits. For future tailings remediations, which are planned in Portugal, individual dose levels should therefore be carefully measured, controlled and registered. Also, optimization techniques to reduce individual and collective doses in the remediation work activities should be implemented.

  1. Manuela Carvalho, António Fiúza, M. Teresa Oliva-Teles, Cristina Delerue-Matos, J.Tomás Albergaria; “Remediation of granitic soils contaminated by MTBE using SVE – A case study”; The Second International Environmental Best Practices Conference and AGFES Educational Workshop; September 2009, Cracow, Poland

  1. Aurora Silva, Olga Freitas, Sónia Figueiredo, Bie Vandervliet, Adelaide Ferreira, and António Fiúza, “Arsenic Removal Using Synthetic Adsorbents: Kinetics, Equilibrium and Column Study”, 12th EuCheMS International Conference on Chemistry and the Environment.7 June 2009, Stockholm, Sweden

Arsenic contaminations are seldom of anthropogenic origin (mining, wood preservatives,…) being generally caused by the natural dissolution of minerals in surface or underground waters In natural waters, arsenic is present either as As(III) or As(V) Both ions are toxic and carcinogenic High concentrations of arsenic in the groundwater (> mg/L) of natural origin have been found in some areas in countries like Bangladesh, West Bengala, India, Mexico and some areas in Argentina, Chile and U S A

The main objective of this research is to establish a comparison between the performance of different sorbents for the removal of As(V): (i) a reference sorbent commercially known as ARM- (BASF Corporation) and two synthetic sorbents prepared at the laboratory, (ii) the hydrous ferric oxide (HFO) in suspension and (iii) loaded onto granular activated carbon (GAC) The research focused in the kinetics and chemical equilibrium using batch scale testing for the three systems

  1. António Fiúza, “Impacte Ambiental Mineiro” (Environmental Mining Impact)”, Pedagogic text for the students attending the Master in Mining and Geo-Resources Engineering, May 2009.

  1. António M. A. Fiúza, “Considerações sobre Tecnologias de Reabilitação de Solos Contaminados”, Indústria e Ambiente, Nº 54, Janeiro/Fevereiro 2009, Págs. 12-16.

As consequências na saúde pública derivadas da existência de solos contaminados foram reconhecidas desde os finais dos anos 70 do século XX originando a criação de legislação específica na maior parte dos países desenvolvidos. Desde então, e especialmente nos últimos 15 anos, desenvolveram-se uma panóplia de tecnologias susceptíveis de aplicação a contaminações de diferente composição química, localizadas em vários tipos de solo e a diferentes profundidades. Referem-se as tecnologias mais utilizadas, o seu campo de aplicação e por vezes referem-se os efeitos perversos potenciais que podem originar. O projecto da reabilitação de solos e aquíferos exige a participação de equipas com conhecimentos multi-disciplinares profundos.

  1. Maria de Lurdes Dinis, António Fiúza: Methodology for Exposure and Risk Assessment in Complex Environmental Pollution Situations, 21 pags, in: “Exposure and Risk Assessment of Chemical Pollution: Contemporary Methodology”, Nato Series For Peace And Security Series, Environmental Security. Environment, Soil Science & Conservation, Analytical Chemistry and Terrestrial Pollution. Simeonov, Lubomir; Hassanien, Mahmoud (Eds). DOI: ISBN: 978-90-481-2334-6 (Print) 978-90-481-2335-3 (Online). ISI Web of Knowledge: Cited: 0, References:

Frequently environmental pollution results from different hazardous substances released in the environment, meaning that contaminated sites may have many different chemical sources and transport pathways. Problems concerning environmental pollution affect mainly physical, chemical and biological properties of air, water and soil. The relationships between the sources, exposure and effects of contaminants to human and ecological receptors are complex and many times are specific to a particular site, to certain environmental conditions and to a particular receptor. Often the methodology for exposure and risk assessment to environmental pollution is translated into sets of assessment questions. These questions are used to meet the needs of assessment, particular important in focusing the assessment during the problem formulation. Risk assessments vary widely in scope and application. Some look at single risks in a range of exposure scenarios, others are site-specific and look at the range of risks posed by a facility. In general, risk assessments are carried out to examine the effects of an agent on humans (Health Risk Assessment) and ecosystems (Ecological Risk Assessment). Environmental Risk Assessment (ERA) is the examination of risks resulting from technology that threaten ecosystems, animals and people. It includes human health risk assessments, ecological risk assessments and specific industrial applications of risk assessment that analyze identified end-points in people, biota or ecosystems.

  1. Maria de Lurdes Dinis, António Fiúza: Modelling Multimedia Pollution For Environmental Exposure, 22 pags, in: “Exposure And Risk Assessment Of Chemical Pollution: Contemporary Methodology”. Nato Series For Peace And Security Series, Environmental Security. Environment, Soil Science & Conservation, Analytical Chemistry and Terrestrial Pollution. Simeonov, Lubomir; Hassanien, Mahmoud (Eds). DOI: ISBN: 978-90-481-2334-6 (Print) 978-90-481-2335-3 (Online). Times Cited: 0, References: 11

The contaminants released into the environment can originate human exposure by the transport through the atmosphere, aquatic systems or through soil sub-compartments. The need for tools to predict environmental behavior of chemicals, contaminants and metals led to the development of mathematical models, which are designed to describe the transport and fate of substances under special environmental conditions. A multicompartment modelling approach may be used to predict contaminants concentration in predefined end-points. Each compartment may represent an environmental media: air, soil, water, flora and biota. Also each one of these compartments may be divided into several sub-compartments. For the exposure assessment from contaminants at large contaminated sites, all transfer pathways leading to the exposure of man and vulnerable ecosystems have to be taken into account. A transfer model through the food chain should also be included, whenever it is possible or relevant. For some contaminants, the uptake into vegetation is the major entry route for the transfer into the food chains: contamination of the trophic chain will be a component of human exposure by transferring the contaminants into animal products that are part of the human' diet. By means of a multicompartment model, the various release mechanisms, transport, transfer and uptake processes are described and the concentration pattern resulting from the consequent exposure is simulated.

  1. Maria de Lurdes Dinis, António Fiúza, “Integrated Methodology for the Environmental Risk Assessment of an Abandoned Uranium Mining Site”, Communication at: “International Conference 2008, Uranium Mining and Hydrogeology – UMH V”, Freiberg, Alemanha, 14 a 18 de Setembro de 2008.

An overview of the essential features of groundwater transport of radioactive contaminants in a saturated porous media is presented and used in an integrated bi-dimensional phenomenological model of transport and fate. The conception and the assumptions implicit in the model are described. The output results are then compared with values estimated by different mathematical space interpolation techniques applied to experimental sample measurements obtained in the surroundings of a contaminated site. These interpolation methods allowed evaluating the spatial variability of the contamination, defining the contour of the plume. These values are then compared to those produced by the transport and fate model. This methodology was applied to uranium and radium, due to their special environmental concern.

  1. Maria de Lurdes Dinis, António Fiúza, “Modelling and Assessment of Radionuclides Differential Transport in Groundwater”, Communication at: “International Conference 2008, Uranium Mining and Hydrogeology – UMH V”, Freiberg, Alemanha, 14th to 18th September 2008.

An overview of the essential features of groundwater transport of radioactive contaminants in a saturated porous media is presented and used in an integrated bi-dimensional phenomenological model of transport and fate. The conception and the assumptions implicit in the model are described. The output results are then compared with values estimated by different mathematical space interpolation techniques applied to experimental sample measurements obtained in the surroundings of a contaminated site. These interpolation methods allowed evaluating the spatial variability of the contamination, defining the contour of the plume. These values are then compared to those produced by the transport and fate model. This methodology was applied to uranium and radium, due to their special environmental concern.

  1. Maria de Lurdes Dinis, António Fiúza, “Modelling and Assessment of Radionuclides Differential Transport in Groundwater”, in “Uranium Mining and Hydrogeology”, Pags. 247-258. Editores: Broder J. Merkel, Andrea Hasche-Berger, Springer-Verlag, Berlin, 2008. ISBN: 978-3-540-87745-5.

This paper presents an overview of the essential components of groundwater water flow and contaminant transport modelling in saturated porous media. It is described the methodology used in groundwater modelling flow, the results of different mathematical interpolation techniques and software tools were used to evaluate radionuclides spatial variability and define the underground contamination plume. A contaminated site from a former uranium mine was taken as a case study. To evaluate the level of contamination in the site and in its vicinity, the radionuclides of the U-chain, in particular for uranium and radium concentration, were monitored in the groundwater of the site.

  1. Maria de Lurdes Dinis, António Fiúza, “Integrated Methodology for the Environmental Risk Assessment of an Abandoned Uranium Mining Site”, in “Uranium Mining and Hydrogeology”, Pgs. 163-176; Editores: Broder J. Merkel, Andrea Hasche-Berger, Springer-Verlag, Berlin, 2008. ISBN: 978-3-540-87745-5.

We developed an integrated approach to evaluate quantitatively the fundamental data required to perform a risk assessment induced by the existence of uranium mine tailings disposals or any other form of low activity waste storage. From the characteristics of the radioactive sources the different types of possible releases are evaluated using phenomenological models. The concentrations in the main environmental compartments are deduced. To this data we apply models of environmental transport, dispersion and fate within each environmental compartment, as well as models of inter-compartment transfer. The activity is then predicted at predefined exposition locations, in each environment compartment. Models of transfer to the food chain were also developed allowing estimate concentration of different radioisotopes in all the media. This data, complemented with an exposure scenario, allows a quantitative environmental risk assessment.

  1. Vila, M. Cristina; Fiúza, António M., “Analysis Of Bioremediation Respirometric Data Using Wavelets”, 4th European Bioremediation Conference, Chania, Crete, Greece, September 2008.

The study of biodegradation using respirometry generates an enormous quantity of data, with several millions of registers for each variable. We have been treating this enormous amount of information using several mathematical techniques. The first step is always the filtration of the data in order to eliminate anomalies strange to the process, such as voltage breakages. The length of the data can be reduced using conventional statistical methodologies or by using wavelets or by combination of both. We have been applying wavelet analysis to signals generated by the respirometry of biodegradation with three different purposes: (i) as a method of data filtration or denoising that keeps the inner core structure of the information without aliasing; (ii) as an interpretation tool; (iii) to detect variation patterns at smaller scales. The synthesized signals can be subsequently used to create digital data-driven mathematical models, either single input-single output or multiple input-multiple output, using the tools of the system identification theory.

  1. Vila, M. Cristina; Fiúza, António M.; Futuro, Aurora; Carvalho, J. M. Soeiro, “The Use of Biosolids in the Attenuation of Acid Mine Drainage”, 4th European Bioremediation Conference, Chania, Crete, Greece, September 2008.

Portugal is an important tungsten producer since the last quarter of the XIX century. Metallic ores, such as copper, tin, tungsten, lead and zinc, have its main occurrence in sulphide environments.

The exhaustive exploitation during long periods of time generated huge quantities of mineral wastes containing high grades in sulphur and iron. The wastes react with air and rain water producing, with kinetics varying from short to long term, the well known acid mine drainage.

Biosolids from sewage sludge were tested as an oxygen consumer cover of the sulphide tailings, through two different experimental scales: laboratory and pilot scale tests. Laboratory scale tests allowed to predict the acid production potential as well as its kinetics. Pilot tests are more difficult to implement than those at laboratory, but they permit a better and more accurate forecast of potential releases as well as a more accurate simulation of the temporal evolution.

Aerobic microorganisms living on biosolids consume the oxygen before it reaches the mine wastes. It has two significant advantages. First, the acid potential decreases significantly; secondly, it represents an innocuous destination for the biosolids originated in the treatment of residual municipal waters and, at the same time, it allows a rapid growing of a plant green layer over the desert-like landscapes originated by the mine waste deposits.

  1. A. Silva, D. Dias, M. Miranda, C. Delerue-Matos, A. V. de la Fuente, A. Fiúza, “Trichloroethylene degradation by different types of iron”, IWA World Water Congress, Wien, Austria, September 2008

Trichloroethylene (TCE) is a small halogenated compound that has been extensively used as a metal degreaser, dry cleaning agent and all-purpose solvent. As a result of its widespread use, TCE is commonly found in the environment. Human exposure to TCE in environment is of concern because TCE has been found to be carcinogenic (Kelsh1 et al, 2005). The purpose of this work is to make a preliminary evaluation of the reduction capability (Moon et al, 2005) of different types of iron. Three different kinds of iron were used: elemental iron pellets (Sigma-Aldrich), low carbon steel spheres (commercial), nanometric iron (Toda Kogyo Corporation). The presence of degradation by-products such as Cis-1,2-dichloroethylene (cis-DCE) and trans-1,2- dichloroethylene (trans- DCE) was also investigated.

  1. António Fiúza, Cristina Vila, Aurora Silva, Alexandre Leite, Joaquim Góis, Cristina Delerue Matos, Aurora Futuro, Paula Ávila, Relatório de Execução Material do Projecto “Respirometria da Libertação de Ácidos e a Utilização de Coberturas Consumidoras de Oxigénio como Método de Prevenir Emissões a Partir de Armazenamento de Resíduos Minerais” Projecto de Investigação POCI/ECM/60438/2004.

This report is divided in six chapters. The first chapter in introductory and describes the main physical, chemical and biological phenomena involved on the generation of Acid Mine Drainage (AMD) from mining and ore processing wastes. It also refers the main type of tests that can be used to forecast both the capacity and the kinetics of acid drainage. The second chapter describes in detail the testing procedures that can be used to assess the AMD potential and describes its application to ore processing residues from the two most important Portuguese mines in activity (Neves Corvo and Panasqueira). Next chapter (3rd) describes experimental protocols to assess the accelerated dynamics of AMD and the results that were obtained with the same wastes. In the fourth part it is described how respirometry can be used to assess the relative importance and kinetics of sulphide oxidizing bacteria, using either continuous respirometry or soil bottle respirometers. The fifth chapter describes experiments conducted at pilote-scale, in an open-air experimental station conceived specially for this purpose. The measurements obtained in this installation with the wastes without cover, with a single cover and a multiple cover, are compared with the results obtained from laboratorial procedures. Finally, in the last chapter, models for diffusion of oxygen through the wastes, through an impermeable cover (clays) and through an organic cover, are presented as well an integrated model of diffusion through a multi-layer cover.

  1. António Fiúza, Antonio Fuente, Aurora Silva, Cristina Vila, Cristina Delerue Matos, Aurora Futuro, Alexandre Leite, Relatório de Execução Material do Projecto “Protocolos Experimentais Para Determinação dos Parâmetros de Dimensionamento de Barreiras Reactivas Permeáveis “, Projecto de Investigação POCI/ECM/59779/2004

This report is divided into three sections:

- Section 1: Research conducted with chlorinated organic compounds;

- Section 2: Research developed for metallic anions, specially chromium;

- Section 3: Design and simulation of reactive permeable barriers.

The first Section describes the research performed in relation to the destruction of trichloroethylene in reactive permeable barriers (RPB) using iron chips: preliminary tests, batch tests, continuous tests in columns. The results obtained are also compared with alternative technologies, namely oxidation-in-situ and reduction-in-situ using nanoparticulate iron. Efficiencies obtained with different types of iron are also compared. The methods, procedures and equipped used are described in detail.

The second section concerns the research accomplished relatively to the reduction of Cr(VI) to Cr(III) done by iron granules. The results obtained in batch tests and in columns are described in detail. An interpretation for the phenomenology of the reaction could be done through the usage of sophisticated methodologies, namely using an electronic scanning microscope. A new kinetic model was developed based on the heterogeneous nature of the reaction occurring. The experimental procedures are also described.

Finally, in the last section it is presented an integrated methodology for designing and simulating the behaviour of the RPB, considering simultaneously the hydrogeology and the chemical reaction. First, the hydrogeological behaviour of the aquifer is compared for different geometric configuration of the funnel and gate barriers. Next, a kinetic model relating the chemical behaviour and the residence time to the properties of the water flow, both through the aquifer and the barrier, is considered leading to a methodology for designing a RPB. Finally, for a case study, a barrier is designed and its behaviour is simulated in steady and transient conditions.

  1. A. Vega de la Fuente, A. Silva, G. Carvalho, C. Delerue-Matos, A. Fiúza, “Pretreatment Of Zero-Valent Iron For Reactive Permeable Barriers In Chromium (Vi) Remediation”, Consoil 2008, Milano, Italy, 3-6 June 2008

Chromium is identified as one of the major pollutants detected in groundwater and soils. It can be detected in all the environmental compartments, with concentrations between 0.1 g/m3 in the air and 4 g/kg in soils (Merian, 1985).

The higher oxidation state Cr6+ is far more toxic, carcinogenic and mobile in the groundwater than the reduced form (Puls, 1997).

Permeable reactive Barriers (PRBs) are passive systems for treatment of groundwater that remove the contaminants by chemical reactions inside the barrier. It is an alternative suitable for heavy metals occurring in water in an anionic form (such as Cr6+,As6+, As3+ and Se6+), (Blowes, at al.,1999), (Wilkin, at al., 2003).

In recent years researchers demonstrated that, Cr6+ can be effectively reduced by granular iron.

  1. António Fiúza, Abílio Cavalheiro, Aurora Silva, “Tratamento De Um Aquífero Contaminado Com TCE Utilizando Oxidação In-Situ”, 5º Congresso Luso-Moçambicano de Engenharia, Setembro de 2008

O tricloroeteno (TCE) é um composto orgânico halogenado volátil que foi utilizado durante muitos anos como desengordurante de peças metálicos e como produto de limpezas nas lavandarias. Sob o ponto de vista tóxico é um composto classificado como tóxico por ingestão e cancerígeno por ingestão e inalação. A sua utilização apenas agora passará a estar restringida na Comunidade Europeia, existindo um amplo passivo ambiental derivado da sua ampla utilização no século XX.

Detectada a existência de um aquífero profundo contaminado com o referido composto, seleccionou-se, após teste preliminares, a tecnologia da oxidação in-situ como a mais apropriada para reabilitação nesta situação específica. No entanto, foram testadas outro tipo de reacções como a desalogenação redutiva utilizando ferro nanoparticulado.

A operação de recolha sistemática de amostras permitiu inferir que o contaminante, dada a sua pouca solubilidade na água e a sua densidade superior, se destribui em profundidade com um gradiente de concentração que varia desde concentrações relativamente baixas nas zonas superficiais do aquífero até à provável existência de uma fase autónoma em profundidade.

Foram estudados laboratorialmente, em testes descontínuos, dois reagente oxidantes: o permanganato de potássio e o reagente de Fenton; os resultados foram comparados com testes idênticos utilizando o ferro nanoparticulado. Realizaram-se de seguida ensaios contínuos em coluna preenchida com material de composição petrológica e granulométrica idêntica à que se supõe existir no aquífero. Estes testes implicaram procedimentos experimentais específicos muito cuidadosos dada a elevada volatilidade do TCE, tendo sido realizados em colunas fechadas em ambas as extremidades, num ambiente termostatizado.

A oxidação in-situ é uma tecnologia de reabilitação relativamente recente que se fundamenta na injecção de um oxidante no aquífero contaminado através de furos. Em torno destes furos de injecção colocam-se furos de captação que bombeam a água do aquífero cumprindo assim duas funções: manter a contaminação num espaço físico confinado e retirar a água tratada para a superfície. Parte desta será utilizada na preparação da solução oxidante e re-injectada. Outra parte poderá sofrer um tratamento complementar à superfície

  1. António Fiúza, Cristina Vila, Rocio Martinez, “Métodos de Previsão da Geração de Ácido a Partir de Resíduos Mineiros” ; 5º Congresso Luso-Moçambicano de Engenharia, Setembro de 2008

Os testes laboratoriais utilizados para determinar o potencial de geração de ácido podem ser de natureza estática ou dinâmica. Um teste estático determina simultaneamente, a partir de uma amostra, a capacidade total de geração de ácido bem como o potencial total de neutralização desse ácido. A capacidade total de geração de ácido é determinada ou como a diferença entre estes valores ou como o seu quociente. A partir desses resultados pretende-se inferir se existirá ou não geração de ácido quando da exposição dos resíduos aos agentes meteóricos. Estes testes não determinam a cinética da geração de ácido mas apenas o potencial de produção. Os testes estáticos são conduzidos de forma expedita e apresentam custos pouco relevantes. Os testes cinéticos pretendem simular, a uma velocidade acelerada, o que acontece nos locais mineiros. Exigem um tempo de realização superior e têm um custo superior. Os dados obtidos a partir destes testes podem ser utilizados para classificar os resíduos de acordo com o seu potencial de geração de ácido. Esta informação, quando recolhida e avaliada durante o próprio estudo de viabilidade de um novo empreendimento mineiro ou de construyção civil, permite projectar medidas de mitigação desde o início do projecto. A principal distinção operatória, a nível laboratorial, entre os dois tipos de testes reside no facto que os ensaios estáticos correspondem a uma única determinação temporal enquanto que os ensaios cinéticos recorrem a vários ciclos repetitivos de exposição da amostra a várias cargas de soluções aquosas. Os testes cinéticos permitem simultaneamente inferir a composição iónica dos lixiviados. De uma modo genérico pode-se afirmar que sob o ponto de vista metodológico os ensaios estáticos, devido à sua rapidez e baixo custo, podem ser efectuados com um grande número de amostras constituintes de várias unidades litológicas representativas, enquanto que os ensaios dinâmicos serão efectuados sobre uma ou duas amostras, geralmente compósitas e com uma composição sugerida pelos resultados obtidos com os testes estáticos. Os autores submeterem amostras dos resíduos do tratamento de minérios de duas explorações mineiras portuguesas em actividade a vários destes testes estáticos e dinâmicos, comparando-os entre si.

  1. M. M. M. Ribeiro, E. V. Soares, M. M. L. Guimarães, and A. M. A. Fiúza, “Stability of the Dispersed Band in a Shallow Layer Settler”, International Solvent Extraction Conference 2008, Proceedings of the 18th International Solvent Extraction Conference, Tucson, Arizona from September 15 to 19, 2008.

The present study is aimed at shallow-layer settlers, involving pilot plant data collecting about the thickness of the dispersion band at different points along its length and its use in simulation work. At steady state, after step inputs in the agitation power, the length of the dispersed band varied in time, and didn’t return to its initial condition. Although clean, pure fluids were used, crud formation was observed and acquired relevance especially for long period experiments. This behavior brought out the fact that crud formed during the experimentation disturbed the stability of the dispersed band. Crud analysis, performed by fluorescence microscopy, suggested the presence of bacteria. This bacterial nature of the crud was confirmed and biocide utilization seemed to be adequate for its minimization.

  1. M. Cristina Vila, J. Soeiro de Carvalho, A. Futuro da Silva, A. Fiúza, “Preventing acid mine drainage from mine tailings”, Waste Management and the Environment IV, Pgs. 729 to 738, Editors: M. Zamorano, C.A. Brebbia, A.G. Kongolos, V.Popov & H. Itoh, WIT Transactions in Ecology and the Environment, Volume 109, WIT Press, 2008. ISI Web of Knowledge: Times Cited: 0, References: 5

Mining activity always has high impact on its surroundings, being waste deposition the cause of multiple and complex problems to the environment. One of them is Acid Mine Drainage (AMD), causing acid water percolation through large areas in the mine site. Portugal was a prosper tungsten producer from the beginning of

the XX century, having its apogee during World War II. Nowadays there are millions of tons of mine residues deposited in either stock piles or in tailing dams, most of them abandoned, and only one mine still producing tungsten. Available experimental tests to evaluate the acid production potential are listed and commented.

Fresh tailings from the still active Panasqueira mine were used as a case study. Laboratory scale tests allowed us to predict the AMD potential as well as its kinetics, which constitutes a very important tool in tailings management. Pilot scale experiments tested the effect of different cover types, including an organic compound host of oxygen consumer microorganisms, in preventing and reducing AMD.

  1. Aurora Silva, Adelaide Ferreira , Paula Freire Ávila, Cristina Delerue-Matos and António Fiúza, “Arsenic leaching in the tailing materials of Vale das Gatas abandoned mine (Northern Portugal) – a case study”, Arsenic in the Environment, 2nd International Conference, Valencia 21-23 May.

In the Vale das Gatas mine a tin–tungsten mineralization occurs associated to numerous quartz veins. The mineral paragenesis comprises cassiterite, wolframite, scheelite, sulphides, particularly arsenopyrite, among others. Mining activities were developed from 1883 until 1986. After the mine closure the tailings remained deposited nearby the mine plant, in spite of its high As contents (Ávila, 2005). The tailings have been disposed of for approximately 100 years. These leftovers are classified as coarse mine waste, coarse from the heavy media separation, sand, shale and clays. Climate, which is aggressive in this region, with hot and dry summers and cold and rainy winters, affected the exposed materials during the deposition phases in the active mine life.

The samples were collected in depth, along three grooves with approximately 4m each, in the tailing slopes, one of them drains directly to a small creek. Surface runoff and water percolation leach the tailing materials and form acid mine drainage. In order to reproduce the natural acid generation and according to the steps of sulphides oxidation defined by Kleinman et al. (1981), an acid sequential extraction was made. In the first step, simulating rain action, water at pH 6 was added, in the second acid was added until different pH values to simulate the natural acid generation. The procedure was repeated in the presence of 10% humic acid. The extracted liquids were analyzed for As by ICP-OES.

Results showed high contents of arsenic extracted in both steps, mainly associated to shale and clays materials, some with intercalated scorodite minerals (electron microprobe analysis revealed the presence of Fe arsenates and hydrated Fe-As oxides). Tests also evidenced that dissolved organic matter promotes the As mobility. This results lead to the conclusion that the tailing material is strongly altered and As has a high local environmental mobility.

  1. Cristina Delerue-Matos, Aurora Silva, Teresa Silva, Elizabeth Vieira, António Fiúza, “Trichloroethylene quantification in polluted Groundwater”, Comunicação ao Euroanalysis XIV- European Conference on Analytical Chemistry, 51-S17, Antwerp, 2007.

  1. M. L. Dinis, A. Fiúza, “Simulation of Radon Flux Attenuation in Uranium Tailings”, in: “Methods and Techniques for Cleaning-up Contaminated Sites”. Series: NATO Science for Peace and Security Series; Subseries: NATO Science for Peace and Security Series C: Environmental Security, Annable, M. D.; Teodorescu, M.; Hlavinek, P.; Diels, L. (Eds.) 2007, V, 280 p., Softcover, ISBN: 978-1-4020-6874-4, ISI Web of Knowledge: Times Cited: 0, References: 5

Tailings wastes are generated during the milling of certain ores to extract uranium and thorium. In a recent past uranium mill tailings consisted of fine-grained sand and silt materials, usually disposed in large piles in an open air area. Radium is probably the most hazardous constituent of uranium tailings. It produces radon, a radioactive gas which can easily spread into the environment. Airborne radon decays into a series of short half-life products that are hazardous if inhaled. Tailings also emit gamma radiation which can increase the incidence of cancer and genetic risks. Post closure and site rehabilitation involves, among other situations, controlling and estimating radon release from the surface of the tailings pile. Generally the primary cleanup method consists of enclosing the tailings with compacted clay or native soil to prevent the release of radon and then covering this layer with rocks and vegetation. This implies a cover design and placement which will give long term stability and control to acceptable levels of radon emission and gamma radiation, preventing also erosion and water infiltration into the tailings.

An algorithm based on the theoretical approach of diffusion was developed to estimate radon attenuation originated by a cover system placed over the tailings pile and subsequently the resulting concentration in the breathing atmosphere. The one dimensional steady-state radon diffusion equation was applied to a porous and multiphase system to estimate the radon flux from the tailings to the surface. The thickness of a cover that limits the radon flux to a stipulated value was performed in a particular contaminated site. The efficiency of the cover attenuation was evaluated from the comparison with the resulting radon concentration in the absence of any cover system.

Keywords: radon, cover system, tailings, radium, flux, diffusion.

  1. M. L. Dinis, A. Fiúza, “Exposure assessment to radionuclides transfer in food chain”, in: “Multiple Stressors: A Challenge for the Future”. Series: NATO Science for Peace and Security Series, Subseries: NATO Science for Peace and Security Series C: Environmental Security, pages 309-323, Mothersill, Carmel; Mosse, Irma; Seymour, Colin (Eds.), 2007, Approx. 375 p., Softcover, ISBN: 978-1-4020-6334-3, ISI Web of Knowledge: Times Cited: 0, References: 12

Generally sites with radioactive contamination are also simultaneously polluted with many other different toxics, especially heavy metals. Besides the radioactivity, these wastes may also hold different amounts of chemicals, toxic pollutants and precipitates. The radionuclides released into the environment can give rise to human exposure by the transport through the atmosphere, aquatic systems or through soil sub-compartments. The exposure may result from direct inhalation of contaminated air or ingestion of contaminated water, or from a less direct pathway, the ingestion of contaminated food products. Contamination of the trophic chain by radionuclides released into the environment will be a component of human exposure to ionizing radiations by transferring the radionuclides into animal products that are components of the human diet. This can occur by first ingestion of contaminated pasture by animals and then by ingestion of animal products contaminated. The relevant incorporation of the radionuclides into

cow’s milk is usually due to the ingestion of contaminated pasture. This transfer process is often called the pasture-cow-milk exposure route. A compartment dynamic model is presented to describe mathematically the radium Behaviour in the pasture-cow-milk exposure route and predict the activity concentration in each compartment. The dynamic model is defined by a system of linear differential equations with constant coefficients based in a mass balance concept. For each compartment a transient mass balance equation defines the relations between the inner transformations and the input and output fluxes. The concentration within each compartment is then transcribed to doses values based on a simplified exposure pathway and a pre-defined critical group.

Keywords: exposure assessment, radium, dynamic model, differential equations

  1. M.L. Dinis, A. Fiúza, Models for the transfer of radionuclides in the food chain”, in: "International Conference on Environmental Radioactivity from Measurements and Assessments to Regulation”, 23-27 April 2007, Vienna, Austria, Book of Extended Synopses, pages 323-323, IAEA-CN-145.

A dynamic compartment model is proposed to describe mathematically the radionuclide transfer to the food chain, following an initial radionuclide deposition. It predicts the activity within each sub-compartment considered for the pasture-cow-milk exposure route. The generic model is divided in two main sub-models allowing for the possibility of considering the animal as a global compartment being the concentration estimated for the whole body, or alternatively considering the inner distribution within the cow.

The conception of the models is based in first-order transfer rates from one compartment to the next using simple mass balance and rate equations. The dynamic model is defined by a system of linear differential equations with constant coefficients describing the mass balances in the different compartments, taking into account the fluxes in and out and the radionuclides decay inside each compartment. The fluxes between the compartments are estimated considering transfer rates proportional to the amount of the radionuclide in the compartment. The transfer coefficients for the sub-compartments within the cow are combined with the respective biological half-lives.

The first model considered for the radionuclide transport through the food chain considers as initial state a contaminated pasture that is consumed by a cow that produces a certain quantity of milk. A more sophisticated model is also described taking into account the spread of radionuclides within the cow by including the sub-compartments related to the organs involved in the distribution: The scheme for the conceptual model describing the radionuclide transfer within the cow was adapted from the International Commission on Radiological Protection biokinetic models [2].

The system of differential equations was written in the standard matrix form used in the space state approach and solved numerically using Matlab. The continuous time models are composed by the state vector and by the input and output vectors. The outputs of the system are quantities that can be measured or observed and the output vector is a linear combination of the state and of the input, often called the observation vector that is represented by the observation equation.

A simulation was done for a constant radionuclide input in a specific case study [1]. The necessary parameters were adopted from different sources: some parameters were adopted from measurements referring to a particular contaminated site [1] and others were adopted from published data on radionuclide behavior in animals, such as distribution or retention in different organs and tissues and subsequent excretion routes [3]. The unknown parameters were estimated from available data. Radionuclides transfer rates within the cow were selected from specialized literature [2, 3 and 4].

The exploration of the model can be applied to uranium, thorium, lead and polonium considering the available data for the necessary model parameters. The model output represents the time variation for the considered radionuclide in the pasture-cow-milk exposure route and also its distribution within the cow. A complete simulation was already done for radium and will be published elsewhere [5].

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