The form and location of gold in the structure of arsenopyrite and pyrite minerals, and the mechanisms for the mobility agglomeration of gold in arsenopyrite during thermal treatment, have been studied using a combination of Rietveld X-ray diffraction refinement, Convergent Beam Electron Diffraction (CBED) and Atomic Location by Channelling Enhanced Microanalysis. The basic structure of all the arsenopyrite compositions studies, has been shown to be monoclinic P2(subscript)1/c, regardless of the variation in stoichiometry. An increase in the arsenic to sulfur ratio in the natural arsenopyrites was found to be associated with an increase in unit cell dimensions accompanied by expansions within the iron-centred octahedra along the [101] direction of the monoclinic cell and concommitant contractions of the octahedra in the (101) plane. There was no obvious relationship between variation in stoichiometry and structure of arsenopyrite which could provide information as to possible substitution of gold in its structure. However, atomic displacements caused by twinning or disorder, may help to incorporate gold.The synthesis of auriferous arsenopyrites showed that gold has to be in an ionic form to be taken up in the structure. The form of the gold species affects the distribution of gold in the structure, being chemically zoned when derived from a dichloro complex and more evenly distributed when derived from a hydrosulfido complex. It is suggested that rapid crystallisation, with resultant displacement faults along the b-axis, may contribute to higher concentrations of gold in the natural arsenopyrite structure. Electron probe microanalysis showed a possible slight iron-deficiency in some of the auriferous arsenopyrite grains analysed. However, the errors in the analyses were too high to provide conclusive evidence of gold substitution in the iron sites, as has been ++ / proposed in the literature.Analyses of natural and synthetic pyrites showed no deviations in structural parameters which could indicate possible substitution of gold or other impurities within the structure.Electron channelling experiments showed that gold was located on the sulfur sites in pyrite. In arsenopyrite, there was some evidence for gold located on the iron sites, however, most gold was interstitial, probably situated between the octahedra. This location is probably facilitated by the presence of the displacement faults as observed by CBED in the synthetic auriferous arsenopyrite.Breakdown of arsenopyrite under thermal treatment was topotactic along its b-axis, which converts to the a-axis in the pyrrhotite structure, following a reconstruction mechanism based on the preferential removal of arsenic over sulfur. Gold was visually recorded exsolving from the arsenopyrite structure and agglomerating as liquid metal globules as the arsenopyrite was chemically altered during thermal treatment under the Transmission Electron Microscopy electron beam. Gold became mobile on the decomposition of arsenopyrite, but this was not observed until a temperature of approximately 470 degrees celsius was reached. Above the temperature both solid solution and particulate gold became mobile. The interaction of arsenic vapour and gold reduced the melting point of gold.The observations on the effects of arsenic residence time, and the relative mobility of solid solution and particulate gold during the thermal decomposition of auriferous arsenopyrite and pyrite, have significant implications for improved industrial extraction of gold from these minerals.

Electrochemical methods, surface spectroscopy and flotation tests have been used to study the influence of the oxidation of arsenopyrite on its floatability with xahthate. Cyclic voltammetric studies indicated that the oxidation of arsenopyrite at pH greater than 7 results in the formation of ferric hydroxide deposits on the surface of the mineral. Arsenic is oxidized to arsenate and sulphur is oxidized to sulphate. The arsenate is incorporated in the ferric hydroxide deposits while sulphate diffuses into solution. Below pH=7, soluble iron species are formed and the surface becomes increasingly covered with elemental sulphur with decreasing pH. Increasing temperature has no influence on the quantity of hydroxide formed over the range 30° to 45°C but results in thick, porous films at temperature greater than 45°C. The oxidation of arsenopyrite was demonstrated to occur at lower oxidation potentials than for pyrite although this effect decreased with increasing temperature. Mixed potential studies indicated that the potentials required for arsenopyrite oxidation could be achieved with common oxidizing agents. Selective oxidation of arsenopyrite in a bulk pyrite-arsenopyrite concentrate was indicated to be possible. The formation of iron hydroxide deposits on the surface of arsenopyrite resulted in the inhibition of subsequent oxidation of xanthate to dixanthogen at the mineral's surface. ESCA studies confirmed the formation of oxidized iron layers at the surface of arsenopyrite and revealed that essentially all the arsenate which was formed was incorporated in these layers. Sulphur became oxidized at the pH studied and to a large extent went into solution. Flotation studies demonstrated the use of oxidation for arsenopyrite depression. In the presence of oxidation, increasing pH above pH=7 resulted in increased arsenopyrite depression while increasing temperature had little effect until a temperature of 40°C was exceeded. Previously activated arsenopyrite could be depressed through the use of oxidizing agents. Arsenopyrite could be selectively depressed from a bulk pyrite-arsenopyrite concentrate through the use of oxidizing agents. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

The objective of this study is to use a mixed flow reactor system to determine the dissolution rate and infer potential mechanisms of arsenopyrite (FeAsS) oxidation by dissolved oxygen at 25°C and circumneutral pH. Release rates for iron, arsenic and sulfur are calculated for a variety of initial dissolved oxygen (DO) concentrations. Results indicate that the rate of arsenopyrite oxidation, represented by the rate law r = A(6.76 x 10-11) where the rate, r, is in mol/s and surface area, A, is in m2, is not significantly dependent on DO concentration. Arsenic and sulfur are released in a 1:1 molar ratio while iron is released more slowly due to precipitation of iron oxyhydroxides. Our results suggest that the rate determining step in arsenopyrite oxidation is determined by the attachment of oxygen at the anodic site in the mineral, and not the transfer of electrons from the cathodic site to oxygen, as is suggested for other sulfide minerals such as pyrite. Previous work on FeAsS oxidation has been limited to low pH conditions with ferric iron as the oxidant. However, not all arsenopyrite weathering occurs exclusively in acidic environments. For example, at an abandoned arsenopyrite mine in Virginia, the pH of ground and surface waters is consistently between 4 and 7. Results of this study provide important insight to arsenic mobilization processes and rates, at field-relevant conditions, consequently aiding in the effort to understand arsenic release and retention in the environment. / Master of Science

The oxidation of refractory gold concentrates containing arsenopyrite and pyrite and the simultaneous dissolution of gold in aerated alkaline solutions at ambient temperatures and pressures without the addition of cyanide has been studied. It involves the following aspects: the chemistry of the oxidation of pure arsenopyrite and pyrite minerals in aerated alkaline solutions; the kinetics of oxidation of arsenopyrite and the simultaneous dissolution of gold in such solutions; the kinetics of simultaneous dissolution of gold during the alkaline oxidation of refractory gold concentrates; the electrochemistry of gold in alkaline solutions containing thiosulfate or monothioarsenate; the effect of copper on the leaching of gold in alkaline thiosulfate solutions; and the leaching of gold in alkaline solutions with thioarsenites. The nature and proportions of the products of the oxidation of arsenopyrite in aerated alkaline solutions have been studied using high pressure ion chromatography techniques that have shown that thiosulfate and a new species, monothioarsenate, are the main oxidation products of arsenopyrite apart from arsenate and sulfite. The alkaline oxidation of pyrite primarily yields thiosulfate and sulfite. A kinetic investigation of the oxidation of arsenopyrite with air or oxygen has shown that the initial rate of arsenopyrite oxidation is proportional to the concentration of dissolved oxygen. A reaction mechanism for the oxidation of arsenopyrite has been proposed, which involves an anodic oxidation of the mineral involving hydroxyl ions coupled to a cathodic process for oxygen reduction which is partially controlled by mass transfer of dissolved oxygen to the mineral surface. Detailed studies of the dissolution behaviour of gold in aerated alkaline solutions in the presence of thiosulfate or monothioarsenate by electrochemical and leaching methods have demonstrated that the dissolution rate is very low as compared to that of gold in alkaline cyanide or ammoniacal thiosulfate solutions. It has been found that copper ions catalyze the dissolution of gold in the thiosulfate solutions in the absence of ammonia. The leaching experiments also have shown that gold may dissolve in alkaline thioarsenite solutions, which provides a possible new process option for the leaching of gold. The oxidation of refractory arsenical gold concentrates in aerated alkaline solutions results in the formation of thiosulfate, arsenate and sulfate as well as the dissolution of gold, copper and iron. It appears that the dissolution of gold is due to the complex reactions of gold with thiosulfate ions promoted by the catalytic effect of copper ions. Up to 80% of the gold may be extracted during the oxidation of selected refractory arsenical

No description available.

No description available.

Lenka Soukupová, Zvětrávání arsenopyritu v lesních půdách v acidifikovaném prostředí SUMMARY The weathering of arsenopyrite (FeAsS) has been studied at the experimental site Načetín in the Ore Mountains, Czech Republic. There were chosen three areas with different vegetation (beech, spruce a unforested areas) at this site. The arsenopyrite samples were placed in all soil horizons (litter, horizons A, B and C for forest areas; horizons A, B and C for unforested area), where they were exposed to ambient conditions for one year. After one-year weathering, the newly formed secondary minerals were identified and the rate of surface oxidation was determined, both depending on the environment of oxidation. Although physical-chemical parameters and content of main and trace elements of the studied soils varied, the only detected crystalline secondary mineral of arsenic was scorodite (FeAsO4∙2H2O). Nevertheless, this differences affected amount of formed scorodite. The highest concentrations were determined on the surface of the arsenopyrite grains that oxidized in the beech stand, conversely the lowest concentrations were determined on the arsenopyrite grains from the unforested area.

Foram realizados estudos do comportamento eletroquímico de eletrodos de pinta, pirrotita e arsenopirita em meio ácido. A investigação incluiu tanto a dissolução dos minerais (isolados ou combinados dois a dois) como o estudo da deposição de íons prata sobre eles, levando em consideração as propriedades semicondutoras de cada um. Com base nos dados obtidos, empregando voltametria cíclica, medidas de capacitância, medidas fotoeletroquímicas e microscopia eletrônica de varredura, foram propostos mecanismos de dissolução para cada mineral. A oxidação dos três minerais em função dos produtos obtidos foi avaliada a partir das quantidades relativas de SO42-, S e Fe(OH)3 e constatou-se que a quantidade relativa de sulfato produzida pela pirita é maior que a quantidade obtida do eletrodo de pirrotita. A arsenopirita apresenta comportamento intermediário. O hidróxido de ferro produzido pela pirrotita é maior que o obtido da pirita e da arsenopirita. A presença do As2S3 na superfície do eletrodo de arsenopirita dificulta a redução do enxofre. Os dados obtidos com os eletrodos mistos mostram que, em potenciais próximos de Eca, as reações que produzem enxofre e Fe(III) predominam. Acima de 0,8 V, tem início a oxidação de S e/ou S2O32- gerando sulfato para os três eletrodos, além da oxidação do As2S3 nos eletrodos que contém arsenopirita. A presença da pirita na mistura dos minerais, em quantidade maior que 60%, pode abaixar o pH local favorecendo a decomposição do tiossulfato. Os valores dos potenciais de bandas planas foram estimados com base nos modelos de Gärtner e Mott-Shottky e o valor da energia de banda proibida, de cada mineral e dos eletrodos mistos, foi avaliado. Foi estabelecido que, em meio de solução tampão de ácido acético/acetato de sódio, pH = 4,5, o nível de Fermi dos minerais está vinculado ao potencial de óxido redução do eletrólito. O potencial de circuito aberto é determinado pela presença de óxidos/hidróxidos de ferro na superfície dos eletrodos. Sob iluminação todos os eletrodos apresentaram fotoefeitos. Com o aumento da porcentagem de pirrotita ocorre uma diminuição na fotocorrente registrada. Já a adição de arsenopirita, provoca um aumento nos fotoefeitos observados. A adição de pirrotita faz diminuir a eficiência quântica dos eletrodos enquanto que a adição de arsenopirita favorece a resposta fotoeletroquímica das superfícies. O aumento da quantidade de pirrotita na superfície faz com que a energia de banda proibida diminua. A mistura pirita/pirrotita para qualquer composição deve favorecer a produção de enxofre em detrimento da de sulfato. Quando se utilizam eletrodos de pirita/arsenopirita não se observam variações a circuito aberto. A investigação sobre a deposição de íons prata sobre os eletrodos mostrou que o contato com os íons metálicos em solução não produz modificações morfológicas significativas na superfície dos eletrodos. A prata metálica e os sulfetos de prata formados são incorporados em pequenos núcleos espalhados pela superfície. Ficou demonstrado que sulfeto de prata e prata elementar podem ser identificados pela análise dos voltamogramas. Nos eletrodos construídos com combinações de minerais as interações com os íons prata ocorrem, preferencialmente, nos grãos de pirrotita ou arsenopirita para todas as composições. A interação mineral/prata ocorre mediante a competição de vários sítios da superfície pelos íons em solução. A quantidade de íons prata em solução tem um papel importante no aumento da velocidade de dissolução dos sulfetos. O consumo de H2S e de S2O32- deve causar o aumento na velocidade de dissolução dos minerais. De uma maneira geral, pode-se concluir que as combinações pirita-pirrotita otimizam as interações com os íons Ag+, tanto por oferecer maior quantidade de sítios de enxofre/intermediários para as interações químicas como por apresentar maior quantidade de elétrons na superfície a circuito aberto. Por outro lado, a presença de arsenopirita prejudica as interações com a prata já que causa uma diminuição na concentração efetiva de elétrons na superfície. Além disto, a formação de sulfetos de arsênio limita a quantidade de enxofre disponível para as interações químicas com os íons em solução. / The electrochemical behavior of iron sulfides, pyrite, pyrrhotite and arsenopyrite was studied in acetic acid/sodium acetate buffer, pH = 4.5. The investigations included the dissolution of minerals (isolated and mixed in pairs) and the studies of the deposition of silver ions on the electrode surfaces, taking into account the semiconducting properties of each one. Based on the data obtained using cyclic voltammetry, capacitance and photoelectrochemical measurements and scanning electron microscopy, mechanisms of dissolution for each mineral were proposed. The dissolution of the three minerals was evaluated taking into account the relative amounts of SO42-, S and Fe(OH)3 obtained and evidenced that the relative amount of sulfate formed from pyrite is greater that from pyrrhotite. Arsenopyrite presents intermediate behavior. The quantity of iron hydroxide produced by pyrrhotite is greater that produced by pyrite and arsenopyrite. The presence of the As2S3 in the surface of the arsenopyrite electrode inhibits the reduction of sulfur. The results obtained with the electrodes constructed with two minerals show that, in potentials next to Eoc, the reactions producing sulfur and Fe(III) predominate. Above 0.8 V, the oxidation of S and/or S2O32- occurs, generating sulfate for all electrodes. On the electrodes, containing arsenopyrite, the oxidation of As2S3 also takes place. The presence of pyrite in the mixture of minerals (more than 40% in weight) causes a decrease of the local pH, favoring the thiosulfate decomposition. The values of the flat band potentials have been estimated based on Gartner\'s and Mott-Shottky \'s models. The value of the band gap energy, of each mineral and of the mixed electrodes, was evaluated. It was established that, in the working solution, the Fermi level of the minerals coincided with the redox potential of the electrolyte. The open circuit potential is determined by the presence of oxides/hydroxides on the electrode surface. The pyrrhotite addition reduces the quantum efficiency while the presence of arsenopyrite favors the photoelectrochemical yield of the electrodes. An increase of the amount of pyrrhotite produces a decrease in the value of the bandgap energy of the electrodes. The pyrite/pyrrhotite mixture, for any composition, favors the sulfur production in detriment of the sulfate one. At open circuit conditions, the mixture pyrite/arsenopyrite does not present any variation. The study of the deposition of silver ions showed that the contact with the metallic ions in solution does not produce significant morphologic modifications on the electrode surfaces. The metallic silver and the silver sulfide formed are incorporated in small grains spread along the surface. It was demonstrated that silver sulfide and elemental silver might be identified by the inspection of the voltammograms. In the electrodes constructed with mineral combinations the interactions with silver ions occur, specially, in the grains of pyrrhotite or arsenopyrite for all compositions. The silver concentration in solution plays an important role increasing the dissolution rate of the sulfides. The S2O32- and H2S consumption may intensify the dissolution rate of the minerals. The mixture pyrite-pyrrhotite improves the interactions with Ag+ ions, at open circuit, by producing more S2O32-/S for the chemical interactions and by increasing the electron concentration at the surface. On the other hand, the presence of arsenopyrite disfavors the interactions with silver as it reduces the number of charge carriers on the electrode surface. Moreover, the formation of arsenic sulfides limits the reduction of sulfur and the chemical interactions with ions in solution.

Foram realizados estudos do comportamento eletroquímico de eletrodos de pinta, pirrotita e arsenopirita em meio ácido. A investigação incluiu tanto a dissolução dos minerais (isolados ou combinados dois a dois) como o estudo da deposição de íons prata sobre eles, levando em consideração as propriedades semicondutoras de cada um. Com base nos dados obtidos, empregando voltametria cíclica, medidas de capacitância, medidas fotoeletroquímicas e microscopia eletrônica de varredura, foram propostos mecanismos de dissolução para cada mineral. A oxidação dos três minerais em função dos produtos obtidos foi avaliada a partir das quantidades relativas de SO42-, S e Fe(OH)3 e constatou-se que a quantidade relativa de sulfato produzida pela pirita é maior que a quantidade obtida do eletrodo de pirrotita. A arsenopirita apresenta comportamento intermediário. O hidróxido de ferro produzido pela pirrotita é maior que o obtido da pirita e da arsenopirita. A presença do As2S3 na superfície do eletrodo de arsenopirita dificulta a redução do enxofre. Os dados obtidos com os eletrodos mistos mostram que, em potenciais próximos de Eca, as reações que produzem enxofre e Fe(III) predominam. Acima de 0,8 V, tem início a oxidação de S e/ou S2O32- gerando sulfato para os três eletrodos, além da oxidação do As2S3 nos eletrodos que contém arsenopirita. A presença da pirita na mistura dos minerais, em quantidade maior que 60%, pode abaixar o pH local favorecendo a decomposição do tiossulfato. Os valores dos potenciais de bandas planas foram estimados com base nos modelos de Gärtner e Mott-Shottky e o valor da energia de banda proibida, de cada mineral e dos eletrodos mistos, foi avaliado. Foi estabelecido que, em meio de solução tampão de ácido acético/acetato de sódio, pH = 4,5, o nível de Fermi dos minerais está vinculado ao potencial de óxido redução do eletrólito. O potencial de circuito aberto é determinado pela presença de óxidos/hidróxidos de ferro na superfície dos eletrodos. Sob iluminação todos os eletrodos apresentaram fotoefeitos. Com o aumento da porcentagem de pirrotita ocorre uma diminuição na fotocorrente registrada. Já a adição de arsenopirita, provoca um aumento nos fotoefeitos observados. A adição de pirrotita faz diminuir a eficiência quântica dos eletrodos enquanto que a adição de arsenopirita favorece a resposta fotoeletroquímica das superfícies. O aumento da quantidade de pirrotita na superfície faz com que a energia de banda proibida diminua. A mistura pirita/pirrotita para qualquer composição deve favorecer a produção de enxofre em detrimento da de sulfato. Quando se utilizam eletrodos de pirita/arsenopirita não se observam variações a circuito aberto. A investigação sobre a deposição de íons prata sobre os eletrodos mostrou que o contato com os íons metálicos em solução não produz modificações morfológicas significativas na superfície dos eletrodos. A prata metálica e os sulfetos de prata formados são incorporados em pequenos núcleos espalhados pela superfície. Ficou demonstrado que sulfeto de prata e prata elementar podem ser identificados pela análise dos voltamogramas. Nos eletrodos construídos com combinações de minerais as interações com os íons prata ocorrem, preferencialmente, nos grãos de pirrotita ou arsenopirita para todas as composições. A interação mineral/prata ocorre mediante a competição de vários sítios da superfície pelos íons em solução. A quantidade de íons prata em solução tem um papel importante no aumento da velocidade de dissolução dos sulfetos. O consumo de H2S e de S2O32- deve causar o aumento na velocidade de dissolução dos minerais. De uma maneira geral, pode-se concluir que as combinações pirita-pirrotita otimizam as interações com os íons Ag+, tanto por oferecer maior quantidade de sítios de enxofre/intermediários para as interações químicas como por apresentar maior quantidade de elétrons na superfície a circuito aberto. Por outro lado, a presença de arsenopirita prejudica as interações com a prata já que causa uma diminuição na concentração efetiva de elétrons na superfície. Além disto, a formação de sulfetos de arsênio limita a quantidade de enxofre disponível para as interações químicas com os íons em solução. / The electrochemical behavior of iron sulfides, pyrite, pyrrhotite and arsenopyrite was studied in acetic acid/sodium acetate buffer, pH = 4.5. The investigations included the dissolution of minerals (isolated and mixed in pairs) and the studies of the deposition of silver ions on the electrode surfaces, taking into account the semiconducting properties of each one. Based on the data obtained using cyclic voltammetry, capacitance and photoelectrochemical measurements and scanning electron microscopy, mechanisms of dissolution for each mineral were proposed. The dissolution of the three minerals was evaluated taking into account the relative amounts of SO42-, S and Fe(OH)3 obtained and evidenced that the relative amount of sulfate formed from pyrite is greater that from pyrrhotite. Arsenopyrite presents intermediate behavior. The quantity of iron hydroxide produced by pyrrhotite is greater that produced by pyrite and arsenopyrite. The presence of the As2S3 in the surface of the arsenopyrite electrode inhibits the reduction of sulfur. The results obtained with the electrodes constructed with two minerals show that, in potentials next to Eoc, the reactions producing sulfur and Fe(III) predominate. Above 0.8 V, the oxidation of S and/or S2O32- occurs, generating sulfate for all electrodes. On the electrodes, containing arsenopyrite, the oxidation of As2S3 also takes place. The presence of pyrite in the mixture of minerals (more than 40% in weight) causes a decrease of the local pH, favoring the thiosulfate decomposition. The values of the flat band potentials have been estimated based on Gartner\'s and Mott-Shottky \'s models. The value of the band gap energy, of each mineral and of the mixed electrodes, was evaluated. It was established that, in the working solution, the Fermi level of the minerals coincided with the redox potential of the electrolyte. The open circuit potential is determined by the presence of oxides/hydroxides on the electrode surface. The pyrrhotite addition reduces the quantum efficiency while the presence of arsenopyrite favors the photoelectrochemical yield of the electrodes. An increase of the amount of pyrrhotite produces a decrease in the value of the bandgap energy of the electrodes. The pyrite/pyrrhotite mixture, for any composition, favors the sulfur production in detriment of the sulfate one. At open circuit conditions, the mixture pyrite/arsenopyrite does not present any variation. The study of the deposition of silver ions showed that the contact with the metallic ions in solution does not produce significant morphologic modifications on the electrode surfaces. The metallic silver and the silver sulfide formed are incorporated in small grains spread along the surface. It was demonstrated that silver sulfide and elemental silver might be identified by the inspection of the voltammograms. In the electrodes constructed with mineral combinations the interactions with silver ions occur, specially, in the grains of pyrrhotite or arsenopyrite for all compositions. The silver concentration in solution plays an important role increasing the dissolution rate of the sulfides. The S2O32- and H2S consumption may intensify the dissolution rate of the minerals. The mixture pyrite-pyrrhotite improves the interactions with Ag+ ions, at open circuit, by producing more S2O32-/S for the chemical interactions and by increasing the electron concentration at the surface. On the other hand, the presence of arsenopyrite disfavors the interactions with silver as it reduces the number of charge carriers on the electrode surface. Moreover, the formation of arsenic sulfides limits the reduction of sulfur and the chemical interactions with ions in solution.

The Swedish mining industry has changed from the historical situation with several smaller mines to the present situation with a few, bigger mines. This results in presence of abandoned mines around Sweden. Remediation of mines is regulated by legislation and the present demands are considerably higher than it was some decades ago.  The Storliden mine was a Zink- and Coppermine active between 2001-2008. Storliden is located in Malå municipality, Västerbotten county, and is included in the Skellefte district, known for its sulfide mineralizations.  The ore was broken underground with a technique called cut and fill mining. It was estimated that the ore was to be consumed in 2007, but due to rising ore prices, the mine was operated until 2008. Remediation was done through backfilling the mine with waste rock from Storliden and Boliden’s mines Renström, Kedträsk, and Kankberg. Also, tailings, concrete, and sludge from the sedimentation basins were backfilled. Today, the mine is filled with water.  High Arsenic concentrations in water is a serious health issue in parts of the world. Bangladesh is perhaps the most common example where Arsenic in groundwater has caused health problems for millions of people. In Sweden, the Skellefte field is known for its elevated Arsenic concentrations in the bedrock, related to sulfide mineralizations. Studies confirm a correlation between Arsenic-bearing bedrock and elevated concentrations in water.  This thesis work has been conducted together with the consultant company Golder Associates (Golder) in Luleå. Golder has performed environmental investigations in the Storliden area during the period 2018-2020. Installation and sampling of groundwater wells were included in this investigation. High concentrations of Arsenic was found in some of the groundwater wells. This thesis aims to review potential sources of Arsenic and their potential significance. The purposes are to be fulfilled by evaluating and interpreting the results from the sampling, Piper diagrams, ratios, and modeling in the program PHREEQC.  The results indicate that the presence of Arsenopyrite in the bedrock is the most likely source of the elevated concentrations of Arsenic in deep groundwater. Oxidation of Arsenopyrite is likely caused by mainly dissolved oxygen in groundwater. Further, the water quality differs from different depths, indicating that deep groundwater and water flow from the mine via the ramp do not have any immediate connection. It is likely that remains of tailings on the industrial area cause low pH and leaching of metals locally.  High concentrations of Arsenic can occur very locally, highlighting the importance of conducting sampling of groundwater used as drinking water in areas where sulfide mineralizations are confirmed or suspected. Further, a relation between the time that water is in contact with the bedrock/mineralization and the concentration of Arsenic is stated. Higher concentration HCO3- tends to correlate with elevated Arsenic concentration. / Sveriges gruvindustri har förändrats i snabb takt, från ett flertal mindre gruvor till dagens läge med ett mindre antal större gruvor. Detta resulterar i förekomst av nedlagda gruvor runt om i Sverige. Efterbehandling av gruvor regleras genom lagstiftning, och kraven idag är betydligt högre än för bara något decennium sedan.   Storlidengruvan var en zink- och koppargruva verksam mellan 2001–2008. Storliden ligger i Malå kommun och området ingår i Skelleftefältet, känt för sina sulfidmineraliseringar. Malmen bröts i en underjordsgruva med så kallad igensättningsbrytning, dvs. tomrum har succesivt fyllts ut med material under driften. Malmen beräknades vara förbrukad 2007, men när malmpriset ökade kunde gruvan leva vidare till 2008. Efterbehandlingen innebar att fylla igen gruvan med gråberg från Storliden men också gråberg från Bolidens gruvor Renström, Kedträsk och Kankberg. Dessutom användes anrikningssand, cement och slam från sedimentationsbassängerna för att fylla igen gruvan. Länshållning av gruvan upphörde och idag är gruvan vattenfylld. Höga arsenikhalter i vatten är ett hälsoproblem i delar av världen. Det kanske vanligaste exemplet är Bangladesh, där arsenik i grundvatten har orsakat hälsoproblem för miljontals människor. I Sverige är Skelleftefältet utmärkande för den höga arsenikhalten i berggrunden. Naturlig arsenikhalt i borrade brunnar har undersökts i flera studier som visar ett samband mellan arsenikhaltig berggrund och förhöjda halter i vatten.  Examensarbetet har utförts tillsammans med konsultföretaget Golder Associates i Luleå. Golder har fått i uppdrag att utföra miljötekniska undersökningar i Storlidenområdet, bland annat ingick installation och provtagning av grundvattenrör. Denna provtagning skedde under perioden 2018–2020. I några av grundvattenrören påträffades förhöjda halter av arsenik. Detta examensarbete syftar till att utreda förekomsten av Arsenik i grundvattnet, undersöka vilka källor som kan vara orsaken till arsenikhalterna samt källornas förväntade betydelse. Detta har gjorts genom att utvärdera och tolka resultaten från provtagningarna samt användningen av Piper-diagram, geokemiska kvoter och geokemisk modellering i programmet PHREEQC. Resultaten indikerar att förekomst av arsenikkis som mineralisering i berggrunden är den mest troliga källan till de förhöjda halterna av arsenik i djupt grundvatten. Oxidationen av arsenikkis sker troligtvis främst av löst syre i grundvattnet. Vidare skiljer sig vattenkvalitén åt från olika djup och delar av området som provtagits, dvs. det verkar inte finnas någon omedelbar koppling mellan djupt grundvatten och vatten som kommer via rampen som leder till gruvan. Det är troligt att rester av anrikningssand på industriområdet orsakar lågt pH och metallutlakning lokalt.  Höga arsenikhalter kan förekomma lokalt, vilket understryker vikten av att utföra provtagning av grundvatten som används för dricksvatten i områden där misstänkt eller konstaterade sulfidmineraliseringar förekommer, eftersom arsenik annars kan vara en mycket skadlig ”diffus” förorening. Vidare konstateras också samband mellan den tid som vatten är i kontakt med mineralisering och arsenikhalt. Högre halt HCO3- tenderar att korrelera med förhöjd arsenikhalt