1,720,975 research outputs found
Geochemical hazard evaluation of sulphide-rich iron mines : the Rio Marina district (Elba Island, Italy)
No full textPotentially 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
Determinazione 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
Innovative approaches to evaluate geochemical risk related to sulphide-bearing Abandoned Mine Lands
Full text linkAbandoned Mine Lands (AML) are often perceived to have significant environmental impacts, particularly on superficial and ground waters, from water contaminated with acid and elevated metals flowing from eroding waste dumps and from underground workings. These conditions would require risk assessment and remediation in case of necessity.
However AML have heritage and historical value because of their age and the significance of their structures and the processes used. This value could be destroyed by remediation done following the environmental law in force.
Take into account the particular features of AML (terrains characterised by natural high metal and metalloid concentrations) and environmental law problems (the inability of agencies to cite or allocate clear ownership for the problems at the sites), rise the need to develop an approach that allows the right and complete geo-environmental characterisation of AML and that supports the management and/or the remediation of AML.
The main problems related to AML comprise:
the identification and characterisation of mine dumps;
the assessment of the geochemical hazard;
the persistence in time of the chemical processes which occur at the site.
Mine dumps are the waste products of exploitation, composed mainly of rocks with metal concentration too low to be economic but rather high to be a source of environmental pollution.
A preliminary low-cost identification of mine dumps could be done by means of digital elaboration of topographic maps. This operation allows to identify and to evaluate the morphology and dimension of mine dumps having bibliographic data and CAD software (Servida et al., 2009).
Mine dumps characterisation could be completed and refined by Electrical Resistivity Ground Imaging (ERGI) investigations (Mele et al., 2007) that enable to reduce direct investigation number and, consequently, to reduce costs and acquisition time. Moreover ERGI investigations supply 3D information concerning a more extended area.
Geochemical hazard related to sulphide-bearing AML could not be evaluated taking into account only the metal and metalloid concentrations of terrains, since it is high by nature. It is suggested to evaluate geochemical hazard starting from the combination of high metal and metalloid concentrations and of the acid production or neutralising potential of terrains by AMIRA procedure (IWRI & EGI, 2002). Hazard evaluation was performed by geostatistical analyses, resulting from 1) the interpolation of the terrain chemical features on the whole area, 2) the overlapping of previous results and 3) the adding of the topographic setting. This approach allows to identify the areas where the presence of metal and metalloids is really hazardous. It also supports the choice of areas that need any treatment.
Since AMD processes have a key-role in environmental damages from mining pollution, it is important to know their persistence in time. No studies about this topic have already done. In a preliminary step, the persistence of AMD processes could be calculated starting from common data as yearly rainfall, mining waters pH and acid production or neutralising potential of terrains. The following step is to consider the results of kinetic tests.
These approaches have been developed on three pilot sites with different geo-environmental setting:
Rio Marina mining district (Elba Island, LI), characterised by hematite + pyrite ore association, exploited for iron from Etruscan age till 1981;
Libiola mine (GE), characterised by chalcopyrite + pyrite ore association, exploited for copper from 1864 till 1962;
The application of the proposed methodologies and techniques allows a better geo-environmental characterisation of AML.
Moreover we think that the proposed approach for the assessment of geochemical risk related to AML could contribute to reduce the areas that need remediation. Consequently will be possible to reduce costs of remediation and impact of remediation on AML
Statistical and geostatistical analysis of heavy metals distribution in the mine waste dump of Coren del Cucì (Gromo, Val Seriana, BG)
No full textSince Roman Age and for long time in the past the Coren del Cucì mining area, located close to Gromo village in Upper Val Seriana (BG), has been exploited for Fe, Cu, Pb, Zn and Ag (Jervis, 1881). Mineralization consists of pyrite + chalcopyrite + arsenopyrite + tetrahedrite ± sphalerite ± galena (De Capitani et al., 2003) hosted into a quartz breccia at the boundary between the Crystalline Basement and the late Paleozoic Collio Formation (Servida et al., 2006). Differently from other small waste disposals in the area, the occurrence of the main dump is highlighted by a colour of the covering vegetation (Calluna Vulgaris) which is different from the other vegetation in the area. In the first stage a judgemental sampling survey (EPA, 2002) has been planned; using FOREGS sampling methods (Salminen et al., 1998) about 60 soil samples and 15 vegetation samples have been collected. All the samples have been analyzed with ICP-AES for the determination of major elements (Ca, Fe, Mg) and heavy metals (Ag, Cd, Co, Cu, Ni, Pb, Zn) concentration. Moreover, to get more information about the possible geochemical mobility of elements, pH values of soils have been determined. Starting from obtained data and by means of the calculation of statistical descriptive parameters to remove outlier values of concentration, a statistical analysis has been performed which allowed to subdivide data in populations: in particular, the outstanding features are the presence of a single population matching with the local background for Mg and Fe and the occurrence of two populations matching with local and dump background for Ca. Also for Co, Cu, Ni, Zn two populations of data have been found, while for Ag, Cd and Pb a third population emerged matching with the ore itself. The geostatistical analysis of the element distribution in the area has been performed by the elaboration of contour maps. The overall of collected data and their elaboration led to draw a geochemical profile of the dump and to establish relations between the geochemical behaviour of several elements and the geological-environmental variables. In particular Ag, Co, Cu, Ni and Zn show higher concentrations inside the dump and several anomalies located close to the main tunnel entrances, while for Cd emerges a higher concentration only in vegetation outside the dump.
Possible zones in danger of heavy metals pollution have been highlighted through the elaboration of comparison maps between the concentration of heavy metals and the threshold values of soils pollution according to the law in force (D.M. 471/99, D.Lgs. 152/2006), allowing thus to estimate the hazard related to the site. Finally, a strong relation has been observed between mine waste disposal and Calluna Vulgaris (De Capitani et al., 2003), the only vegetation growing on this terrain. The analysis performed on Calluna Vulgaris samples allowed to determine Biological Absorption Coefficient (BAC) for different metals; analytical results confirmed the capability of this species of growing on acid substrates with occurrence of toxic elements and poor of macro-nutrients, but without bioaccumulation
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
Geochemical 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
Phreatic Sulfide-bearing Quartz Breccias (SQB) between Crystalline Basement and Collio Formation (Southern Alps, Italy)
No full textIn questo lavoro vengono presentate le caratteristiche geologiche, petrografiche e minerografiche di alcune brecce quarzose mineralizzate a solfuri che affiorano in un’area complessa delle Alpi Orobie (Subalpino), nei pressi dell’area uranifera di Novazza. Sebbene poco studiate, queste brecce sono state attribuite in passato a differenti processi genetici e/o formazioni geologiche (es: Basamento Cristallino, Conglomerato Basale), ma i caratteri riscontrati sembrano confermare una loro origine idrotermale, probabilmente legata allo stesso processo che ha generato il giacimento di U a Novazza
Characterisation of sulphide-bearing waste-rock dumps using electrical resistivity imaging: the case study of the Rio Marina mining district (Elba Island, Italy)
No full textSulphide-bearing mine dumps are potential sources of pollution when acid mine drainage (AMD) occurs. Because the generation of AMD depends on the volume and composition of waste materials, their characterisation is crucial for the evaluation of geochemical hazards and for the design of remediation strategies to minimise their environmental impact. In this paper, a cost-effective strategy for the characterisation of an inactive mine dump in the Rio Marina mining district (Elba Island, Italy) using earth resistivity imaging (ERI) is presented. As no information regarding the nature of waste rocks is found in reports for the mine, five ERI profiles were acquired at the top of the waste pile. The results show that waste rocks are heterogeneous with a maximum thickness of 30 m. Due to the large amounts of dispersed sulphide minerals,
the waste rocks are characterised by an electrically conductive geophysical signature in comparison to the surrounding resistive metamorphic bedrock. A geostatistical approach was adopted to estimate the elevation of the edges of the mine dump, and the net
volume of the waste rocks was computed through a raster analysis of the elevations of the upper and lower boundaries of the mine dump. High-conductivity anomalies were detected within the core of the mine
dump. The integration of the hydrogeological, geochemical
and geological framework of the Rio
Marina mining district suggests that these anomalies could be a geophysical signature of subsurface regions
where AMD is currently generated or stored, thus representing sources of environmental pollution
Hazard and persistence evaluation of Acid Mine Drainage (AMD) process in Valle Giove mining area (Rio Marina district, Elba Island)
No full textElba island mining activity has been documented since Roman times and was related mainly to iron exploration and exploitation in three districts: Rio Marina, Rio Albano and Capoliveri. Valle Giove is the greatest open pit of the Rio Marina district with 0.5 km2 and is characterized by a hematite + pyrite ± magnetite ± sphalerite ± chalcopyrite ± galena ± bismuthinite ± anglesite ± cerussite ± native sulfur ore association (Tanelli et al., 2001) occurring in strata, lens or vein deposits (Zuffardi, 1990). The effect of open pit mining and other mining-related activities is that sulfides previously isolated from the atmosphere are exposed to oxygen. The oxidation of sulfides acidifies flowing waters that leach ore minerals and dissolve elements such as arsenic, copper, lead, manganese, iron and zinc (Blowes et al., 2003). All these steps, leading to environmental pollution, are known as Acid Mine Drainage (AMD). At Valle Giove AMD process occurs as testified by all the sampled waters (Giove stream, drainage channels, surficial pools and settling basin) which have pH values ranging from 2.08 to 3.35 and an heavy metals content that reaches 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. For a preliminary AMD hazard evaluation a central aligned 100 m mesh square grid sampling (EPA, 2002) was performed and fifty-four different terrain samples (residual soils, waste rocks or debris materials) were collected. They were analysed for major elements by XRF and for trace elements by ICP-AES. Net Acid Producing Potential (NAPP) of terrains was determined following AMIRA procedure (IWRI & EGI, 2002). In addition, spatial distribution of heavy metals and hazard assessment of AMD process were investigated using statistical and geostatistical techniques. Moreover, 3-D Digital Terrain Model (DTM) of the mining area at the beginning (1954) and close to the end (1979) of exploitation were developed using AutoCAD 2004 and SURFER 8 software. The comparison between the two periods shows the distribution of topographical positive (mining waste disposals) and negative variations (quarrying areas) and leads to estimate the volume of the material removed from the mining area in the order of 1.38*106 m3 and the volume of material discharged in the same area in the order of 1.57*103 m3. The latter value must be adjusted with additional investigations since the first-mined open pits next to Valle Giove were used as mine waste dumps (Servida et al., in progress). According to the obtained data three main hazard classes were established and their distribution in the mining area was assessed. About 46% of the mining area surface belongs to class I, where AMD process occurs (NAPP>0 and heavy metals content exceeds law limits), about 52% belongs to class II, where AMD process could occur only if some conditions are satisfied (NAPP>0 and heavy metals content is lower than law limits or NAPP<0 and heavy metals content exceeds law limits), only 2% belongs to class III, where AMD process cannot occurs (NAPP<0 and heavy metals content under law limits). Finally, the persistence of AMD process at Valle Giove was evaluated starting from yearly rainfall, mining waters pH and NAPP values. A complete leaching of the first 0.25 m of the terrains can retain the current environmental conditions for several centuries
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