1,721,036 research outputs found
Relationship between wild trees and heavy metals on the hop waste-rock dump (Roşia Montană mining area , Romania)
No full textHeavy metal pollution from mining activities is a significant environmental problem, as mine dumps are source of dispersion of toxic elements in the nearby ecosystems. Waste-rock dumps can be colonized by metallophyte plant species, able to grow and reproduce on substrates characterised by high metal contents. In this work, the relationship between soils or earth materials and trees growing on the Hop waste-rock dump, from the Roşia Montană gold mine (Romania), were investigated using bio-geochemical analyses.On the Hop waste dump (2.5 ha area), a portion of Cetate open pit, where the waste has been piled up between 1998 and 2000, 10 plant samples, made by leaves, roots, branches and buds, belonging to Salix sp., Popolus tremula and Betula pendula species, were pulled together with the corresponding rizosphera. Results have shown that all plant species are able to grow on acid substrates, with pH values ranging from 3 to 5. Moreover, they can tolerate the presence of AMD processes, as they live on soils and earth materials characterised by positive NAPP values, which correspond to an acid production ranging from 10.8 to 79 kg H2SO4/t. Unlike a general low average content of metals in soils and earth materials, metal contents in plant tissue is always high: Cu and Zn average concentrations are 53 and 382 ppm respectively, reaching the greatest values in Betula pendula leaves (where Cu is 90 ppm and Zn 1,026 ppm). BF values are almost always >1: particularly for Cu they range from 0.8 to 4.5, while for Zn from 1.2 to 56. TF values show a preferential allocation of metals in leaves.These results appear interesting for phytoremediation purpose, also for the surrounding areas not still vegetated; on the other hand, they highlight that eco-toxic elements are actually moving from substrates to living beings, with a potential geochemical hazard
Combinationn of leaching and column test for the assessment of AMD generation from the hop waste-rock dumo (Rosia Montana, Romania)
No full textThe production of Acid Mine Drainage (AMD), as a result of the oxidative dissolution of sulphides, and the release of hazardous elements in the environment are main pollution problems affecting natural watercourses in mining areas, with sulphide-rich residues. An important tool for geochemical assessment of abandoned mine areas are kinetic tests, as they provide an insight into the behaviour of the waste-rocks during the interaction with meteoric waters, giving also useful indications of metal mobility and chemical composition of the run-off waters.
In this study two different kinetic tests were applied to assess the generation of AMD from the run-off water of the Hop waste-rock dump, at the Rosia Montana ancient mining area (Apuseni Mountains, Romania).SPLP results showed that eco-toxic elements content in filtered solutions is generally low: Cu ranges from 0 to 98 ppb (mean 14), Zn ranges from 21 to 570 ppb (mean 155) and As ranges from 1 to 7 ppb (mean 2.5). These data are in agreement with the results of bulk waste-rock material chemical composition, whose metal concentrations are in the range of tens of ppm with the exception of As, that shows a content one order of magnitude higher (Azzali et al., 2010). The pH values vary greatly from 2.9 to 8.9, according to mineralogical and geochemical composition of the waste material. The sulphate content ranges from 13.5 to 475 ppm and exceeds the European limit for drinking waters (250 ppm, EU 1998) in 6 samples. A significant positive relationship between sulphate content and EC was found.Modified column test results showed that geochemical features of the solutions tend to stabilized after 3 weeks: pH values grow from 2.5 to 2.7 (mean values) while EC values and sulphate concentration, though highly variables for the three different grain-size samples, clearly decrease
Persistence and bioaccumulation of potentially toxic elements in the Gromo-Gandellino ancient mine site (Seriana valley, northern Italy)
No full textIn this study, earth materials and plants (Calluna vulgaris and Dryopteris filix-mas) growing on three main dumps located in the Gromo-Gandellino ancient mine site (Seriana Valley, Northern Italy) were collected, in order to assess Potentially Toxic Elements (PTE) contents. Ag, As, Cd, Co, Cu, Ni, Pb and Zn concentrations in earth material and plant tissues were analyzed by ICP-AES. Bioaccumulation (BF) and Translocation Factor (TF) were calculated for plants and a multivariate statistical analysis (PCA) was applied. Results showed that in the waste rocks PTE concentration is one order of magnitude higher than in the natural soils: considering the average concentrations Zn and Pb exceed respectively 3,500 and 3,000 mg•kg-1, while As reaches 860 mg•kg-1. Calluna vulgaris shows several BF values > 1, displaying an evident predisposition to accumulate metals, especially in the roots and to tolerate high As concentrations in soil. In Dryopteris filix-mas metal concentrations are close to baseline values. These species are not hyperaccumulators, however, they are interesting for soil stabilization and could be used to re-establish a vegetative cover in those sites where natural vegetation is rare, due to high metal concentrations. In particular, Calluna vulgaris could be used in contaminated land for phytostabilization
A BIOGECHEMICAL APPROACH FOR THE ENVIRONMENTAL CHARACTERISATION OF MINE LANDS
Full text linkAbstract
The determination of PTE environmental impacts at mine lands is a complex issues, since it regards different environmental matrix, as earth material (soils and waste-rocks), superficial and underground waters and also living beings. All of these can be investigated by biogeochemical tools, as they are very useful to understand how PTE move from waste-rocks to the surrounding ecosystems and how a careful mine land management can control their impacts.
This project was carried out in order to check and develop analytical methodologies for the evaluation of:
1. PTE contamination of earth materials (soil or waste rock), with a special care for arsenic, one of the most dangerous elements for human health;
2. AMD evaluation, by the application of different analytical methodologies (static and kinetic tests);
3. biogeochemical features of wild flora growing on mine sites, in order to collect useful information for mine lands remediation.
AMD evaluation was done by the applications of AMIRA procedure (IWRI & EGI, 2002), that allowed to identify the acid production or neutralising potential of earth materials. Moreover, an important tool for geochemical assessment of abandoned mine-waste dumps was applied, as it is a quick, cost-effective and qualitative leach procedure, designed by the Environmental Protection Agency (1994) to evaluate the impact of contaminated earth material on groundwaters. This kinetic test provides an insight into the behaviour of the waste-rocks during the interaction with meteoric water and gives useful indication of the potential chemical composition of the run-off from the weathered surface of mining areas.
Moreover, the relationship between earth materials and plants growing on mine areas were investigated and metal tolerance strategies were identify by the calculation of the appropriate biogeochemical parameters as Bioaccumulation Factor and Traslocation Factor.
These approaches have been developed on two ancient mine sites, with different geo-environmental setting: Rosia Montana mining area (Romania) and Gromo-Gandellino mining area (Valseriana, Northern Italy).
Rosia Montana mining area (Romania) is a hydrothermal gold deposit hosted in andesites and dacites of Neogene age, piercing the pre-volcanic sedimentary basement as breccia pipes, that host polymetallic sulphides and Au-Ag-Te mineralisations. Century of exploitation caused a significant environmental damage and the excavation and exploitation of tunnels and open pits has generated a large amount of waste-rocks dumps, some of them located close to villages. Private company provided remediation plans for the past mining activity and mitigation plans for reopening.
Gromo-Gandellino ancient mining area is a Ag – Fe ore deposit made up mainly by sulphide, sulphosalts and carbonate, intensely exploited in the medieval epoch and abandoned in the early decades of 20th century. The area is not exploited at the present time, but the numerous underground cavities and waste-rock dumps, some of them located very closed to villages, testify the historical activities linked to the exploitation of Fe, Zn, Pb, Ag and Cu mineralisations.
At Hop waste-rock dump (Rosia Montana mine site, Romania) the spatial heterogeneity is well represented. Earth material is composed by two different rock types: (1) the so-called WR1 samples, a source of acid drainage ; and (2) the WR2 samples, able to buffer the production of acidic water. On the whole, Hop waste rock dump is however a source of acid drainage, as showed both by static and kinetic tests. These last have confirmed to be an important tools for geochemical assessment of abandoned mine-waste dumps, as they are a quick, cost-effective and qualitative leach procedure to evaluate the impact of contaminated earth material on groundwater and to assess metal mobilisation from waste-rocks.
The tree species growing on Hop waste-rock dump, belonging to Salix spp., B. pendula and P. tremula, are able to tolerate limiting conditions (such as acid pH values and mean As content of 80 mg/kg), as known from the literature. They actively accumulate Cu and Zn in their tissues, specially in leaves, although they can not be considered as hyper-accumulators. On the other hand, the same species act as excluders for As, whose concentration in plant tissues are lower than in soils, exceeding however toxic values.Salix spp. represents the species more able to tolerate different environmental situations and to grow on strong acid substrates, acting as a pioneer species that could be used for revegetation of mine lands and stabilization of dump slopes, even on the area still not vegetated.
At Gromo-Gandellino mine site, the occurrence of waste-rock dumps represents an environmental hazard for the area: soil heavy metal concentrations is about one order of magnitude higher than in natural soils, specially at Coren del Cucì site, located in the vicinity of Gromo village.
The mining area is colonised by the metal tolerant species C. vulgaris and D. filix-mas. These plants behave as excluders and accumulation occurs only in roots, where internal metal detoxification mechanisms might exist in addition to exclusion strategies. So, they can be used surely as slope dump “stabilizators” and, in particular, C. vulgaris appears interesting for mine land restoration and soil stabilization of Cu, Zn, Pb, Ni, Cd and As.
The biogeochemical characterisation of these mine lands gave useful information to support their management, as it provided information for the choice of sites that need priority remediation activities, and identified, within these sites, the areas responsible for contamination. Moreover, the identification of metal tolerance species and their strategies provided useful information for project of rehabilitation, but also highlighted how PTE move through food webs
Potentially toxic element contamination in earth material and wild flora at the Roşia Montană ancient mining area (Romania)
No full textPotentially Toxic Element (PTE) pollution from mining activities is a significant environmental problem, as mine dumps are source of heavy metal dispersion in the nearby ecosystems. In this work PTE contamination in the mining area of Roşia Montană (Romania) was investigated by bio-geochemical analyses that have affected both the Hop waste-rock dump and the valley of Roşia River. The Roşia Montană hydrothermal ore deposit is hosted in andesites and dacites of Neogene age piercing the prevolcanic sedimentary basement as breccia pipes. They host polymetallic sulphides and Au-Ag-Te mineralizations that present in epithermal veins, mineralizing phreatomagmatic breccias and stockworks (WALLIER et al., 2006). On the Hop waste dump (2.5 ha) 10 plant samples, belonging to Salix spp., Popolus tremula and Betula pendula species, were collected with the corresponding rizosphera. Moreover, other 12 mixed soil and plant samples, belonging to Alnus glutinosa, were collected, starting from the adit of the SF. Cruci din Orlea gallery up to the confluence between Roşia and Abrud Rivers. Results show that the plant species growing on the Hop waste-rock dump can tolerate acid substrates, with pH values ranging from 3 to 5. Results appear interesting for phytoremediation purpose, also for the surrounding areas still not vegetated. On the other hand, they highlight that ecotoxic elements are actually moving from substrates to living beings, resulting in a potential geochemical hazard
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Persistence and bioaccumulation of heavy metals around an ancient mine site at Gromo-Gandellino (Valseriana, Northern Italy)
No full textThe land surface is damaged by mining activities and waste rocks often become sources of pollution. Near Gromo village, on both sides of the Valseriana in the Central Orobic Alps (Bergamo, Italy), several proofs of historical mining activities are present. Since XIth century these mines, exploited specifically for Fe and Ag, historically played an important rule for the economic development of the valley. The ore deposits, made up mainly by sulphide, sulphosalts and carbonate were intensely exploited in the medieval epoch and abandoned in the early decades of XXth century. The ore mineralization, represented by a complex and polyphase association of sulfides and sulfosalts containing Cu, Fe, Zn, Pb, Co, Ni, Ag, Sb, As with dominant chalcopyrite and tetrahedrite, is hosted in quartz breccia bodies that crop out along contacts between South Alpine basement and Permo-Triassic cover rocks. Mining activities generated a large amount of waste rocks dumps located near some villages. Three dumps (Coren del Cucì, Pradel and Vedriol) were investigated in details: an amount of 75 earth samples were collected from 15 to 40 cm depth and the fraction 1 displaying an evident tendency to accumulate metals, especially in roots. In aerial parts BF value for Cd reaches 2.90. Range of TF values uphold the behaviour of this species as a metal bio-accumulator, when present around mine sites (Wilson and Pyatt, 2007). In Dryopteris filix-mas metals concentrations are like to normal and exceed a bit the toxic levels only for As and Pb (Kabata Pendias, 2001). BF values are low and < 1 for all elements. Evaluation of trace-element concentrations shows that this two species are not hyperaccumulators; however they appear interesting for soil stabilization and could be use to re-establish a vegetative cover at sites where natural vegetation is scarce due to high metal concentrations, such as contaminated habitats. Especially Calluna vulgaris is able to grow on acid, ore-characterized and nutrients-poor substrates by employing a metal exclusion-strategy and it could be use to contaminated land phytostabilization
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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