Browsing by Author "Fonseca, Rita"
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- Environmental factors and metal mobilisation in alluvial sediments: Minas Gerais, BrazilPublication . Fonseca, Rita; Pinho, Ana Catarina; Albuquerque, M.T.D.; Araújo, JoanaIn areas contaminated by potentially toxic elements (PTEs), knowledge of processes of metal mobilisation is the basis for the choice of appropriate remediation methodologies. The mobilisation of metals is a function of several factors, and the response to these factors must be well known during the planning of remediation strategies. The activity of an ore metallurgical plant in South‐East Brazil resulted in major contamination by several heavy metals. Reversing the contamination’s negative impact required geochemical assessment of the area, including the physicochemical characterisation, quantification, and delimitation of PTEs, and the rating of the solubilisation/mobilisation capacity of these elements. The definition of spatial patterns for PTEs’ distribution allowed the construction of contamination risk maps which work as a tool for the mitigation and control of the contamination plume. The chemical analysis of interstitial water and selective and sequential extraction methodologies showed that elements that occur in the environment in critical concentrations (Zn, Cd, Pb, As) are mostly associated with easily mobilised forms (soluble, exchangeable cations, associated with Mn oxides). Given the great mobility of the contamination plume, any process of removal of contaminated material becomes unfeasible, thus the strategy of remediation for the stream and associated alluvial deposits must be based on methods of in situ decontamination.
- Evaluating the effectiveness of nanotechnology in environmental remediation of a highly metal-contaminated area—Minas Gerais, BrazilPublication . Fonseca, Rita; Araújo, Joana; Pinho, Ana Catarina; Albuquerque, M.T.D.A column experiment at a laboratory level was carried out to assess the effect of the application of nanotechnology in the decontamination of soils and alluvial deposits with high levels of potentially toxic elements (PTEs). A suspension of zero-valent iron nanoparticles (nZVI) was injected at three different concentrations in selected samples (two sediments, one soil). For most of the elements, the retention by nZVI was proportional to the concentration of the suspension and the trend was similar. Metals were immobilized by adsorption on the surface layer of the nanoparticles and/or by complexation, co-precipitation, and chemical reduction. By day 60 following injection, the nZVI lost reactivity and the retained species were desorbed and back into the soluble phase. The definition of spatial patterns for PTEs’ distribution allowed for the construction of contamination risk maps using a geostatistical simulation approach. The analysis obtained from the extractable contents of five target elements (Zn, Cu, Cd, Pb, As) was cross-checked with the estimated map network to assess their retention efficiency. Data from the analysis of these elements, in the extractable phase and in the porewater of the sediments/soils, indicate the nZVI injection as a suitable technique for reducing the risk level of PTEs in contaminated Fe-rich tropical environments.
- A geostatistical approach for mercury spatial patterns assessment in sediments in an old mining region: The Caveira Mine case study, PortugalPublication . Mota, Natália; Fonseca, Rita; Araújo, Joana; Isabel Margarida Horta Ribeiro Antunes; Valente, Teresa; Barroso, Ana; Araújo, Alexandre; Albuquerque, Maria Teresa; Zanini , Andrea; D'Oria, MarcoMercury pollution is significant in many former mining communities worldwide, including in developing countries. Anthropic contributions to environmental Hg pollution are mostly connected to fuel fossil emissions, industrial and mining activities. Among mining operations, gold exploration contributes to the highest Hg contamination rates, given the processes, widely used in the past, of mixing Hg with the gold containing ore, to separate this metal from the bulk impurities. This study, as part of the GeoMaTre project, an ongoing collaborative network (2021-2024) between the Polytechnic Institute of Castelo Branco and the University of Évora, Portugal, aimed to evaluate the potential risk of mercury pollution in stream sediments in the Caveira area, an abandoned Cu, Pb, Zn, Ag, and Au mine, included in the Iberian Pyrite Belt, at South Portugal. This mine corresponds to a Gossan developed on pyrite mineralization, with high gold and silver content at the official beginning of its exploitation, in 1863, having exhausted the reserves in these precious metals in the 1920s. Until the date of its abandonment (1966) the exploitation focused on the remaining metals (Cu, Pb, Zn) and S. Currently, the surrounding area of Caveira mine is essentially composed of areas of waste accumulation, from mining activity, with little or no vegetation. Thirty-three sediment samples were collected from within 0 to 10 cm depth, in a grid of 1Km x 1Km. Hg was determined in samples preserved at about 4ºC at the time of collection, through a mercury analyzer (NIC MA 3000) based on thermal decomposition, gold amalgamation, and cold vapor atomic absorption spectroscopy detection.
- A global dataset of near-natural basins for climate change detectionPublication . Turner, Steve; Hannaford; Berker, Lucy; Dixon, Harry; Griffin, Adam; Kumar, Amit; Suman, Gayatri; Goula, Albert Bi Tié; Watson, Andrew; Pedersen, Anja Iselin; Fleig, Anne; Bodian, Ansoumana; Renard, Benjamin; Arheimer, Berit; Alvarez-Garreton, Camila; Kan, Caroline; Ekkawatpanit, Chaiwat; Murphy, Conor; Ngondondo, Cosmo; Kingston, Daniel; El Khalki,El Mahdi; Amoussou, Ernest; Formetta, Giuseppe; Hodgkins, Glenn; Laaha, Gregor; Sigurðsson,Gunnar; Boutaghson,Hammouda; Giraldo Osorio, Juan Diego; Stahl, Kerstin; Kuraji, Koichiro; Medeiro, Luis; Albuquerque, Maria Teresa; Hanel, Martin; Toucher, Michele; Piniewski,Mikołaj; Saidi, Mohamed Elmehdi; Gautam, Narayan; Venegas Cordero, Nelson; Ribeiro, Nuno de Almeida; O'Connor, Paul; Whitfield, Paul; Schmocker, Petra; Hung-Khoa, Pham Thanh; Midgley, Guy; Rachdane, Mariame; Capell, René; Fonseca, Rita; Mager,Sarah; Westra, Seth; Jain,Sharad; Takanoir,Shimizu; Horton, Sophie; Vissesri, Supattra; Berezowski, Tomasz; Lopes, Walszon; Markonis,Yannis; Asano, Yuko; Tramblay, YvesAs hydrological extremes become more severe in the warming world, impacts to livelihoods, infrastructure, and economies worsen. To attribute emerging trends to climate change, we need to remove the signal of anthropogenic activities, such as, the presence of dams, land-cover change, channelisation and the abstraction of water for public water supplies, industry and agriculture. These human disturbances can obscure climate change signals and distort trends in river flows and, in some cases, lead to a complete reversal of true, natural trends.
- Relations between river sediments and dissolved matterPublication . Egozcue, Juan José; Pawlowsky-Glahn, Vera; Fonseca, Rita; Albuquerque, Maria TeresaA typical but actually unsolved problem is relating dissolved ions in water and the chemical composition of the corresponding sediments. Our first assumption is that botH ion concentrations and the sediments are compositional in nature. Data from the 2022 and 2023 campaigns in the Trimpancho river (Mining System) (Huelva, Spain) are used to illustrate the possibilities and the challenges of such an analysis. The data consists of 23 sampling points recording both 14 dissolved ions (mg/L) and 10 elements (mg/kg) from the sediment. A first analysis of association using the proportionality index of parts (PIP) reveals that binary relations are weak, while the Aitchison-distance correlation indicates that there is some moderate correlation between dissolved ions and sediments. The relation was also examined using compositional canonical correlation. A surprising result was that up to three canonical functions exhibited very high correlations. A deeper evaluation suggested that these high correlations are due to overparametrization given the small sample size. Finally, after simplification of the canonical correlation model, some balances within dissolved ions and within sediments evidenced moderate correlations in accordance with the previous results. Results show that the main relations involve several elements and single element relations are irrelevant. For instance, the ion balance of Ca, Cu, Fe, Zn over Mg, Mn, Ni has a 0.7 Pearson correlation with the sediment balance Al, Mn over Cr.
- Stream sediment pollution: a compositional baseline assessmentPublication . Albuquerque, M.T.D.; Fonseca, Rita; Araújo, Joana; Silva, Natália; Araújo, AntónioA high concentration of potentially toxic elements (PTEs) can affect ecosystem health in many ways. It is therefore essential that spatial trends in pollutants are assessed and monitored. Two questions must be addressed when quantifying pollution: how to define a non-polluted sample and how to reduce the problem’s dimensionality. A geochemical dataset is a composition of variables (chemical elements), where the components represent the relative importance of each part of the whole. Therefore, to comply with the compositional constraints, a compositional approach was used. A novel compositional pollution indicator (CPI) based on compositional data (CoDa) principles such as the properties of sparsity and simplicity was computed. A dataset of 12 chemical elements in 33 stream-sediment samples were collected from depths of 0–10 cm in a grid of 1 km × 1 km and analyzed. Maximum concentrations of 3.8% Pb, 750 µg g−1 As, and 340 µg g–1 Hg were obtained near the mine tailings. The methodological approach involved geological background selection in terms of a trimmed subsample that could be assumed to contain only non-pollutants (Al and Fe) and the selection of a list of pollutants (As, Zn, Pb, and Hg) based on expert knowledge criteria and previous studies. Finally, a stochastic sequential Gaussian simulation of the new CPI was performed. The results of the hundred simulations performed were summarized through the mean image map and maps of the probability of exceeding a given statistical threshold, allowing the characterization of the spatial distribution and the associated variability of the CPI. A high risk of contamination along the Grândola River was observed. As the main economic activities in this area are agricultural and involve animal stocks, it is crucial to establish two lines of intervention: the installation of a surveillance network for continuous control in all areas and the definition of mitigation actions for the northern area with high levels of contamination.
- Stream sediments pollution: A compositional baseline assessment at the Caveira mine, PortugalPublication . Araújo, Joana; Fonseca, Rita; Mota, Natália; Araújo, Alexandre; Antunes I.M.H.R.; Valente, Teresa; Barroso, Ana; Albuquerque, Maria Teresa; Zanini , Andrea; D'Oria, MarcoA high concentration of Potentially Toxic Elements (PTE) can affect ecosystem health. It is therefore essential that spatial trends of pollutants are assessed and controlled. River sediment pollution is widespread in mining communities around the world, including in developing countries. This study, as part of the GeoMaTre project, restoration of water bodies impacted by mine drainage, an ongoing collaborative project (2021-2024) between the Polytechnic Institute of Castelo Branco and the University of Évora, Portugal, aimed to evaluate the potential risk of PTEs pollution in stream sediments under the direct influence of Caveira mine, a Cu-Pb Zn-Ag-Au old mine included in the Iberian Pyrite Belt, South Portugal. Quantifying pollution implies first the understanding of pollution-free stream sediment. Often, this background, or pollution baseline, is undefined or only partially known. Given that the concentration of chemical elements is compositional, as the attributes vary together, a compositional approach was used aiming to find a compositional balance, based on Compositional Data (CoDa) principles. A dataset of 33 samples was collected from within 0 to 10 cm depth, in a grid of 1Km x 1Km and thirteen chemical elements, including PTEs of variable toxicity (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Zn, V) and major elements from lithogenic sources (Fe, Al), were analyzed in preservedsamples at about 4°C. The most extractable forms of metals (except for Hg) were obtained by partial digestion with aqua regia (HCl and HNO3) in a high-pressure microwave digestion unit, followed by ICP-OES analysis. Hg was analyzed determined by a mercury analyzer based on thermal decomposition, gold amalgamation, and cold vapor atomic absorption spectroscopy detection.