1,721,000 research outputs found
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
The geochemistry of outcropping rocks as the starting point for the knowledge of a territory (the Valchiavenna area)
No full textKnowledge of rock chemical composition is very important for the evaluation of soil chemistry, particularly as for the trace element content of residual soil corresponds to the characteristics of the parental rock. These elemental concentrations are known as "background values" and their contents can vary by some orders of magnitude in relation to rock chemistry composition. The evaluation of the most recent literature has allowed us to look at the geochemistry of rocks regarding those trace elements which are particularly significant from the environmental point of view, as Cr, V, Ni, Zn , Pb. The distribution of these elements in some zones of the Valchiavenna area clearly shows the relationship with the different rock types. In particular, the ophiolitic complex of Chiavenna, characterised by mafic and ultramafic rocks, shows high values of Cr (>900 ppm) and Ni (>600). On the contrary, in the Truzzo granitic complex and Roffna rhyolites, the main metals are Zn and Pb. Moreover, the comparison between the abundance sequences of the above mentioned elements clearly highlights that : 1) the various rock types have different amounts of trace elements; 2) the sequence of abundance is different as regards rock chemistry; 3) the absolute value of all trace element sums is very different in the various rock types (e.i.>2000 ppm in ophiolites and < 200 ppm in granites).
During the development of "Progetto Valchiavenna" performed by Dipartimento di Scienze della Terra "A.Desio", some new samplings of the outcropping rock types were made and the geochemical analyses of major and trace elements have increased the chemical knowledge of all the main rock types in the Valchiavenna area. Some maps of trace element distribution are presented, which are useful in making provision for the elemental amounts in soils.
A brief illustration of a case study regarding a restrict zone of the neighbourhood of Chiavenna was reported as an example of the integration of chemical knowledge on rocks, soils and vegetation.
The high Mg content of ophiolite outcrops (average 16 wt% MgO, with some values reaching up to 38 wt%) correspond to as many Cr and Ni concentrations ( up to 2000 ppm). Chromium and nickel determined in some soil sections sampled near Chiavenna, Prosto di Piuro and Uschione have shown contents between 450 e 1600 ppm and 400 and 1800 ppm, respectively. These values exceed the mean contents for soils assigned for different uses. The presence of high levels of metals in soils exerts a pressure on plant species leading to the selection of a specific flora; in particular, the ultramafic sites have an unusual flora related to the effects of Mg and Ni toxicities. On the soils of the Chiavenna area, endemic plant species and Ni-hyperaccumulators (e.i. Alyssum) have not been found. Nevertheless, some species like Hypericum perforatum , Brachypodium pinnatum , Vincetoxicum hirundinaria and Silene vulgaris typical of ofiolithic outcrops are present. Moreover, the metal content determined in some species shows higher values in roots than in aboveground part. This is a strategy that the plant displays to defend itself from the effects of element toxicities
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
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
La geochimica delle rocce come punto di partenza per la conoscenza delle caratteristiche chimiche di un territorio
No full textDeterminazione dell'Acid Mine Drainage nel cantiere Valle Giove di Rio Marina (Isola d'Elba, LI)
No full textL’attività mineraria nell’Isola d’Elba è documentata fin da epoca pre-romana ed è correlata prevalentemente all’estrazione di minerali di ferro dai distretti di Capoliveri e Rio Marina. Il cantiere Valle Giove, oggetto del presente studio, è una miniera a cielo aperto con superficie di circa 1 km2, caratterizzata da una mineralizzazione a ematite + pirite ± blenda e calcopirite in lenti e filoni metrici. Tale sito è stato coltivato dal 1950 al 1981 ed attualmente è gestito dal Parco Minerario dell’Elba e dal Parco Nazionale dell’Arcipelago Toscano che lo utilizzano a fini escursionistici. Il cantiere è ubicato a monte e a ridosso dell’abitato di Rio Marina. L’ampiezza dell’area interessata dai lavori minerari e, conseguentemente, gli ingenti volumi dei materiali di risulta, rendono necessaria la caratterizzazione ambientale del sito e la determinazione dei fenomeni di acid mine drainage (AMD), anche in considerazione del recente termine dei lavori estrattivi. Sebbene i fenomeni di AMD siano solitamente associati ad aree minerarie con paragenesi a solfuri dominanti, la presenza di laghetti acidi e con alte concentrazioni di metalli è indizio dell’instaurarsi di processi di drenaggio acido legati alla distribuzione disomogenea dei solfuri che accompagnano la paragenesi a ossidi dominanti. Il presente studio analizza le problematiche connesse al drenaggio acido di miniera del sito mediante:
1. il calcolo dei volumi di materiale estratto e dei volumi di materiale riportato in discarica mineraria attraverso digitalizzazione, georeferenziazione ed analisi 3D delle carte topografiche del cantiere relative a diversi anni; 2. il campionamento dei terreni secondo uno schema a griglia (EPA, 2002) a maglia quadrata di lato pari a 100 m; 3. la caratterizzazione chimica dei terreni mediante analisi XRF; 4. la realizzazione di carte isopotenziali dei parametri di quantificazione dei processi di AMD (MPA, ANC e NAPP) mediante procedura AMIRA (IWRI & EGI, 2002); 5. la realizzazione di carte di isoconcentrazione dei metalli determinati con analisi ICP-AES.
I risultati ottenuti evidenziano come, anche in un sito minerario costituito prevalentemente da ossidi, i fenomeni di AMD possano creare un problema di primaria importanza a livello ambientale. L’esame complessivo dei dati ottenuti permette di eseguire: 1. la stima della durata nel tempo dei fenomeni di drenaggio acido; 2. la valutazione della composizione dei terreni e del loro possibile ruolo nei processi di AMD; 3. l’identificazione delle sorgenti di contaminazione, dei punti di produzione di acque acide e dei loro percorsi; 4. la proposta di eventuali interventi di ripristino ambientale
Ore minerals and biogeochemical characters of Piazza copper mine area (La Spezia, Italy)
No full textGeochemical hazard evaluation of sulphide-rich iron mines: The Rio Marina district (Elba Island, Italy)
No full textRio Marina mining district (Elba Island) is characterised by hematite+pyrite ore association and was
exploited for iron till 1981, leaving waste rock dumps of several millions m3. The effect of open pit mining
activity in this site is to produce acid mine drainage (AMD) processes leading to environmental pollution,
testified by all the sampled waters (Giove stream, drainage channels, superficial pools and settling basin)
which have pH values ranging from 2.08 to 3.35 and heavy metal concentrations that reach 903.16 mg/l for
Fe, 45.02 mg/l for Mn, 10.08 mg/l for Zn and 1.75 mg/l for Cu. In the present work a space and time related
approach to geochemical hazard evaluation was applied. The geochemical hazard is mainly related to high
heavy metal concentration, acid mine drainage processes development and topographic setting. As all these
parameters are related in space, hazard evaluation was performed by geostatistical methods. Fifty-four earth
material samples (residual soils, waste rocks or debris materials) were collected in a central aligned 100 m
mesh square grid. These were analysed for major elements by XRF, for Cu, Pb, Zn by ICP-AES and for AMD
potential following the AMIRA procedure. The concentration of heavy metals was compared with Italian law
limits. The overlap of Cu, Pb and Zn content maps show that at least one of these heavy metals exceed law
limits in all the area. The AMD test results show that more than 50% of samples have a positive NAPP (Net
Acid Producing Potential) that could reach 258.9 kg H2SO4/t. According to the obtained data, three main
geochemical hazard classes were established and their distribution in the mining area was assessed. About
51% of the mining area surface belongs to the major hazard class, where AMD process occurs, about 49%
belongs to an intermediate hazard class, where AMD process could occur only if certain conditions are met.
Finally, the persistence of the AMD process in the Rio Marina area was evaluated on the basis of yearly
rainfall, mining waters pH and NAPP values. A complete leaching of the first 0.25 m of the earth materials can
retain the current environmental conditions for several centuries
Trivariate Burr-III copula with applications to income data
No full textIn this work, Bivariate Burr-III copula is extended to the trivariate case. This copula seems to be very general and analytically manageable and it provides an alternative to the commonly employed elliptical copulas (such as the Gaussian or the Stutent's t ones) since they have, roughly, the same number of parameters. Several applications to income and wine data are described in the paper. They show that the Trivariate Burr-III copula is, in general, able to capture the dependence structure implicit in observed trivariate data. Moreover, they show that the third-order interaction parameter results, in some cases, significant at 1\% 1 % significance level while, in other cases, it can be removed from the fitted model. The ability of the Trivariate Burr-III copula in representing the dependence structure implicit in the considered data is compared with the ones of other well known copulas: the Clayton copula, the t copula, and the Skew-t copula. It results that the Trivariate Burr-III copula provides a good fitting and turns out to be the best performer in fitting the considered wine data but, on income data, the best performers are the t and Skew-t copulas. The over-performance of the last two copulas on income data is probably due to their ability in representing right-tail dependence (a kind of dependence that is not taken into account by the Trivariate Burr-III copula)
Caratterizzazione geochimica e biogeochimica della discarica mineraria del Coren del Cucì di Gromo (Alta Val Seriana, BG)
No full textLa discarica mineraria del Coren del Cucì è, insieme ad alcune gallerie, quanto rimane a testimonianza dell’antica attività mineraria che si svolse in passato nei pressi dell’abitato di Gromo. Essa è costituita da un accumulo di frammenti di roccia eterometrici più o meno mineralizzati (waste rocks) e dai loro prodotti di lavorazione (tailings) che occupano una superficie di circa 40.000 m2 e hanno un volume stimato di 20.000 m3. La coltivazione del giacimento era volta all’estrazione di metalli pesanti quali Fe, Cu, Pb, Zn e Ag da una mineralizzazione costituita prevalentemente da pirite, calcopirite, tetraedrite, arsenopirite, blenda e galena, ospitata in una breccia di basamento silicizzata posta al contatto fra Basamento Cristallino e Formazione di Collio. Per quanto in concentrazioni molto inferiori a quelle della mineralizzazione vera e propria, la presenza diffusa di metalli al di sopra delle concentrazioni di soglia di contaminazione (CSC) fissate dal D.Lgs. 152/2006 crea una situazione di potenziale rischio ambientale che deve essere valutata.
Per la caratterizzazione del sito, in una prima fase, sono state raccolte informazioni riguardanti gli aspetti giacimentologici, geomorfologici, geologici e idrogeologici.
Successivamente è stato svolto un campionamento ragionato (EPA, 2002) di oltre 60 campioni di terreno distribuiti sia all’interno che all’esterno del corpo di discarica mineraria seguendo la metodologia FOREGS (Salminen et al., 1998). La concentrazione dei metalli nei campioni di terreno è stata determinata mediante analisi ICP-AES, e la loro dispersione nello spazio è stata ricavata dalla georeferenziazione dei dati e dall’elaborazione geostatistica degli stessi, dai quali si evince come: - Pb (massima concentrazione: 9444 ppm) e Zn (19889 ppm) siano concentrati ubiquitariamente sia all’interno che all’esterno del corpo di discarica con dei massimi di concentrazione in corrispondenza di imbocchi di miniera; - Ag (72 ppm), Co (424 ppm), Cu (2861 ppm) e Ni (255 ppm) presentino concentrazioni più elevate in corrispondenza del corpo di discarica mineraria rispetto ai terreni circostanti.
Dal confronto con le CSC del D.Lgs. 152/2006 è possibile osservare come: - Ni superi solo in aree ristrette il limite previsto per i terreni ad uso residenziale; - Cd, Co, Pb e Zn superino diffusamente i limiti per i terreni ad uso residenziale e in due aree ristrette quelli per i terreni ad uso commerciale ed industriale; - Cu superi in una vasta area il limite per i terreni ad uso commerciale ed industriale. Inoltre, è stata osservata una stretta relazione tra i depositi di discarica mineraria e Calluna Vulgaris (De Capitani et al., 2003), unica specie che cresce su questo terreno. A tal proposito alcuni arbusti sono stati campionati ed analizzati per determinare il loro coefficiente di assorbimento per i diversi metalli: i risultati hanno confermato che Calluna Vulgaris è capace di crescere su substrati acidi e poveri di macronutrienti nei quali siano presenti anche alte concentrazioni di elementi tossici, senza però bioaccumularli.
L’acquisizione completa e ordinata dei dati sovraelencati porta ad individuare i punti sorgente dei metalli pesanti e i loro possibili percorsi di trasporto, i possibili recettori della contaminazione, il rischio ambientale correlato al sito e le migliori metodologie di ripristino ambientale
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