Geoquímica das águas subterrâneas. Parte II - Cinética das reações e transporte reativo de massa: conceitos teóricos e exercícios de aplicação

Apontamentos para a unidade curricular de Geoquímica Ambiental - Módulo de Hidrogeoquímic

Geoquímica das águas subterrâneas. Parte I - Reacções de equilíbrio: conceitos teóricos e exercícios de aplicação

Apontamentos para a unidade cirricular de Geoquímica Ambiental - Módulo de Hidrogeoquímic

Metal(loids) bioaccessibility in road dust from the surrounding villages of an active mine

ABSTRACT: Human activities, in general, cause a significant impact on the environment and human health. The present study aims to characterize the road dust of villages located near an active mine and to assess metal(loids) bioaccessible fractions. From the collected road dust samples (<250 µm fraction), the pseudo total, gastric (G) and gastrointestinal (GI) phase (UBM assay) concentrations, mineralogical composition, enrichment factor (EF), and risk for humans were determined. The obtained results revealed that arsenic represents the highest risk to humans, with mean pseudototal values higher than the maximum reference value range. The enrichment factor pointed to As as having significant to very high enrichment in all of the villages. In addition, Cd presented the maximum EF values in all of the villages, and was thus classified as having a very high enrichment. Particles enriched in As, Ca, Fe, Cu, Al, and Ti were identified by SEM-EDS in weathered agglomerates, and were linked to mine wastes and long-distance transport through both wind and/or traffic. The arsenic bioaccessibility fraction (%BAF) presented low values in the studied samples, possibly because of the low complex solubility of Fe with adsorbed As, limiting the release of arsenic and reducing its bioaccessibility. The concentrations of bioaccessible Cd for the G and GI phases were within the reference range, while for Cu, they were above and for Pb they were lower than the reference value range. The results show that the pseudototal fraction risk is overestimated when compared with BAF%; nevertheless, the total G and GI risks were above the carcinogenic target risk (1 × 10−6) in most of the samples. The carcinogenic risk of the bioaccessible contaminants showed that As represented the higher risk for developing cancer over a lifetime, with ingestion being the main risk route.info:eu-repo/semantics/publishedVersio

An integrated investigation of the Rio tailings, Panasqueira mine, Centre Portugal

The risks associated with mine tailings have different nature and, thus, only a multiple approach can investigate and monitor comprehensively the characteristics and evolution of mine tailings impacts on the environment. Deposition at the Rio tailings (Panasqueira Mine) lasted about ninety years. Over one million cubic metres, of complex very fine to fine material, are deposited on a mountain side overlaying the Zezere river, increasing the risk of contamination of one of the most important hydrographic basins in central Portugal. Herein, a multidisciplinary study including geophysics, geochemistry and borehole information, organized in a GIS, is used to characterize the Rio tailings. The geophysical survey comprised ERT (Electrical Resistivity Tomography) and GPR (Ground Penetrating Radar) on the mud impoundment, as well as, on the slope of the tailings. The geochemical survey consisted on collecting water and tailings samples, iron coatings, arsenopyrite stockpile material and ferruginous crust. Samples collected in boreholes, drilled specifically for this project, were also analyzed. The GIS provided imaging of the geophysical, geochemical and particle size spatial distribution, so that comparisons between the different data sets are easily done. Resistivity and GPR allowed bedrock positioning. GPR was able to give layering results within the tailings. Finally, comparison and correlation between geophysical and geochemical results are carried out and evaluated on the GIS platform

Rare Earth Elements fractionation in native vegetation from the Moncorvo iron mines, NE Portugal

Fractionation of Rare Earth Elements (REE) and the accumulation and translocation indexes were measured and determined in the native vegetation [Halimium lasianthum (Lam.) Spach subsp. alyssoides (Lam.) Greuter; Cytisus multiflorus (L’Hér.) Sweet; and Cistus monspeliensis L.; Cistus ladanifer subsp. ladanifer; Lavandula stoechas L.] from the iron mining area of Moncorvo (NE Portugal). There is no correlation between the amounts of REE in rhizosphere and in plants. The REE concentration as the fractionation follows roots>leaves>stems in plants. A slightly enrichment in HREE were found in rhizosphere and plants (roots and stems), whereas the leaves are enriched in LREE. The accumulation and translocation depend of internal complexes ligands. The redox and pH conditions of the rhizosphere conditioned the REE uptake. Greatest bioaccumulation ability of heavy REE (HREE) was found in C. monspeliensis, followed by H. lasianthum that also, has a high capacity of the REE translocation to the aerial parts, contrary to C. monspeliensis. An M-type tetrad effect was determined mainly for HREE (Gd-Ho series) indicating a complexation of REE. The greatest differences in the REE fractionation patterns (mainly for HREE) are observed in stems, as a consequence of the transport function of this organ. Cerium anomaly indicates that the pH and redox conditions affected the uptake of Ce by plants, where the free ionic species are dominated in roots and leaves (positive anomaly), and stems (negative anomaly). Also the Eu-anomaly is greater in roots and leaves than in steams probably by participation in metabolic functions due to similarity with calcium

House dusts of a volcanic island: potential impacts on human health

ABSTRACT: Fogo island (Cape Verde), has an active volcano that last erupted in 2014-15, with melts mainly alkaline, of basanitic to tephritic composition. Dwellings dust composition is the result of natural and anthropogenic interactions. Nineteen house dusts were collected, in representative dwellings all over the island. Fractions 50 µm in diameter, suggesting that bioaccessible fraction might not be high, thus, reducing risk.N/

Dispersão de elementos vestigiais na envolvente da mina abandonada do Vale das Gatas (Sabrosa, Norte de Portugal) : implicações de ordem ambiental

Doutoramento em GeociênciasO Couto Mineiro do Vale das Gatas situa-se em Trás -os-Montes, nas freguesias de S. Lourenço de Riba Pinhão e Souto Maior, concelho de Sabrosa, distrito de Vila Real e possui uma área aproximada de 8 Km2. A exploração deste couto mineiro, que possui 15 concessões, iniciou-se por volta de 1883, tendo os trabalhos mineiros sido suspensos em 1986. O abandono da mina, sem quaisquer medidas de controlo e reabilitação ambientais, tornou- -a num foco de poluição antrópica, constituindo um factor de risco para a segurança e saúde públicas que tende a crescer em função do tempo de abandono da actividade industrial. Os factores de natureza química inscrevem- -se nos de maior preocupação, uma vez que se detectaram, desde logo, situações de evidente contaminação metálica em materiais geológicos de alteração secundária (sedimentos de linhas de água e solos) e nas próprias águas provocadas, em grande medida, pelas escombreiras e outros resíduos provenientes da actividade mineira. Para além do conhecimento que possa existir sobre as concentrações dos elementos químicos nos diversos materiais da crusta e sabendo-se que o ambiente geoquímico é um sistema continuamente dinâmico e dotado de permanente instabilidade físico-química, tornar-se-á fundamental conhecer os mecanismos que presidem às reacções de dispersão, transporte e redeposição desses mesmos elementos. Com o presente trabalho, pretendeu- -se identificar e caracterizar os principais problemas ambientais provocados pela exploração mineira, em particular de alguns metais/metalóides (Cu, Pb, Zn, Cd e As) nas várias fases químicas e mineralógicas. Para tal, recorreu-se a meios amostrais diversos, tais como: sedimentos de linhas de água, águas superficiais e de mina e material de escombreira, com recurso a metodologias de análise química total e de Extracção Química Selectiva Sequencial. Para a interpretação dos resultados obtidos recorreu-se ao apoio de técnicas mineralógicas e de análise estatística (univariada e multivariada). Foi, assim, possível relacionar os padrões de distribuição dos metais indicados nos diferentes meios amostrais com processos de contaminação e dispersão desses mesmos metais, os quais participam num ciclo onde as águas adquirem o principal papel de agente de dissolução e transporte e os sedimentos o meio de retenção. Para atingir os objectivos propostos, perfilhou-se uma estratégia de amostragem, baseada no facto de que, num possível cenário de contaminação, os sedimentos de corrente são bons indicadores das fontes poluidoras antropogénicas na medida em que revelam a presença de contaminantes que não se encontrem na forma dissolvida. Utilizando-se depois, uma amostragem de águas superficiais, material de escombreira, “coatings”, carapaças ferruginosas e espécies vegetais. Neste estudo, visou-se obter a identificação, no terreno, de anomalias geoquímicas e a consequente inventariação de zonas contaminadas associadas à exploração e aos produtos dela resultantes (estéreis ou rejeitados que não possam ser considerados inertes, isto é, nos quais as condições de passividade química não são nulas). Com base nesses resultados, abordou-se a problemática relacionada com medidas de natureza ambiental tendo em vista a elaboração de estratégias de diagnóstico ambiental e o desenvolvimento de planos de acções de monitorização mais ou menos contínua. Os principais resultados apontam no sentido de que as escombreiras surgem como principal fonte de contaminação química, afectando os vários meios amostrados, facto confirmado pelos resultados obtidos em “coatings” e em águas colhidas na ribeira de Vale das Gatas. Os teores nos elementos associados à paragénese mineral são elevados denunciando que, a maioria dos metais tem sofrido processos de remobilização química com a forte contribuição de águas ácidas; esses metais são transportados para a fase água ou formam “coatings” com coprecipitação com Fe. A dispersão de metais existentes na região mineira de Vale das Gatas processa-se por duas vias: mecânica (comprovada pela composição químicomineralógica dos sedimentos de corrente e pelas extensas anomalias geoquímicas identificadas) e química (comprovada pela caracterização química das águas e composição dos minerais de neoformação). O decaimento irregular dos teores anómalos, os resultados provenientes da microssonda electrónica e da extracção química sequencial selectiva sugerem a prevalência da dispersão mecânica nos sedimentos de linhas de água.The Vale das Gatas Mine is located in the province of Trás-os-Montes district of Vila Real occupying an area of approximately 8 Km2. The exploitation of this mining area, which regards 15 concessions, began about 1883 and the mining works were suspended in 1986. The mine abandonment without any measures of control or environmental rehabilitation turned it in a focus of pollution constituting a risk factor for the safety and public health that tends to grow in function of the time of abandonment of the industrial activity. Factors of greater concern seem to be chemical as far as situations of evident contamination metallic in materials of secondary environment (sediments and soils) and in the waters were detected. In great extense, these were originated by existence of tailings and other mining residues. Beyond the knowledge than can exist about the concentrations of the chemical elements in various materials of the earth’s crust and taking in account that the geochemical environment is continuously a dynamic system and it is essential to know the mechanisms that govern the dispersion, transport and redeposition of those same elements. With the present work, we intend to identify and to characterize the main environmental problems that can arise from the mining exploration, namely by related with the dispersion of selected metals/metalloids (Cu, Pb, Zn, Cd and As) in some chemical and mineralogical phases. To achieve this, different media, sediments, superficial waters and tailing material, were sampled. Methods and techniques of total chemical analyses and chemical selective extraction, as well as mineralogical techniques (electron microprobe) were used; data interpretation was supported by statistical analysis. With this methodology it was possible to relate the distribution patterns of the metals in the different sample media, with the contamination and dispersion of those metals, which participate in a cycle where the waters play the main role of carriers and the sediments constitute the retention site. To reach the proposed objectives, a sampling strategy was based on the fact that, the sediments are good indicators of the sources of pollution in a possible scenery of contamination as far as they can reveal the presence of pollutants. A regional stream sediment survey was then followed the sampling of superficial waters, tailings, coatings, shells and vegetable species. In this study it was sought to identify geochemical anomalies and the consequent delineation of polluted zones associated to the mining. More over, with the results obtained some measures were proposed having in mind the rehabilitation of the area and for the monitoring. The results obtained demonstrate that the tailings appear to be the main source of chemical contamination, affecting different geological/biological media which is confirmed by the metals content of coatings, algae and waters collected in Vale das Gatas. The values for the elements associated to the mineral paragenesis are high. Most of the metals suffered processes of chemical remobilization with a strong contribution of the acid waters being transported by the water or forming coatings with coprecipitation with iron. Metal dispersion in the mining area of Vale das Gatas mainly follows in two ways: mechanic (confirmed by the chemical and mineralogical composition of the sediments and for broad geochemical anomalies) and chemical (confirmed by the water and neoformation minerals composition). The irregular decay of the anomalous elements, the results of microprobe and the chemical selective extraction suggest that processes of mechanical dispersion prevail for metal dispersion in the stream sediments