48 research outputs found
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