Waste rock and tailings generated by sulphide ore mining often contains large amounts of iron sulphides which oxidize when exposed to atmospheric oxygen and may generate acidity. In the absence of alkaline minerals to neutralize this acidity, elements including harmful heavy metals become mobile. Clearly, it is a high priority for mining operations to reduce the impact of mining waste on the environment. New research aimed to take advantage of industrial rest products to inhibit acid mine drainage has yielded some reason for optimism. The recycling of chemicals in sulphate pulp mills yields green liquor dregs (GLD). The fact that GLD have a low hydraulic conductivity and are alkaline opens the possibility of using it for construction of sealing layers for sulphidic mine waste. The study consists of two parts. The aim of the first part was to characterize the GLD and evaluate their suitability for sealing layer purposes. GLD were characterized physically, mineralogically and chemically to define variations in the properties of the material and to evaluate if they can act as a potential candidate for construction of sealing layers. Compared to lime, the pure GLD appear to have a higher porosity and surface area even though both materials have comparable particle size. The shear strength may, however, be insufficient. In cover applications, where high compaction grade and low hydraulic conductivity are desirable, mixing additives to GLD is necessary to improve the material properties. Based on the characterization results, the difference between batches is fairly small both mineralogically and physically. GLD could be an alternative to traditional sealing layers made of till since it was shown to have relatively low hydraulic conductivity and high water retention potential. The small particle size and high buffer capacity makes it a better candidate than till which usually varies in size and hydraulic conductivity. There is a chemical variation of the material but the element content does not seem to be an environmental concern.The aim of the second part of the study was to improve the performance of the GLD by blending them with other rest products. Geotechnical and geochemical investigations were performed on GLD mixed with tailings. Humidity cell tests were used to study the effect of GLD on the mobility of elements considered to be major environmental issues in the tailings. By adding tailings to GLD, the shear strength improved 2-3 times after 1 month of curing. The water retention capacity remained at a high level. Humidity cell tests revealed that a 50/50 mix of GLD and tailings has a direct effect on the metal leaching from tailings. The alkaline capacity of the pulping waste raised the pH, thereby stabilizing the tailings and reducing the leaching of Al, Cd, Cu, Ni, Co, Cr and Mn. The amount of leached elements could be directly related to the pH during the test. Elements that showed an increase of leaching as a result of the application of GLD were Mo and As. This is explained by the chemical behavior of these elements and their tendency to become mobile at high pH.In summary, GLD have the potential to both reduce the amount of leachate generated in tailings and, due to their alkaline property, improve the leachate quality by decreasing the metal mobility. However, restrictions occur when GLD are blended with tailings containing large amounts of As and Mo since an increased leaching may be expected. Further research will focus on the aging of the material and its long-term stability.

High precision isotope ratio measurements have found increasing application in various branches of science, from classical isotope geochronology to complex multi-tracer experiments in environmental studies. Progress in analytical technologies in recent years has allowed higher quality data to be obtained through mass spectrometry. Major pitfalls lie in challenges to obtain accurate and reliable isotopic data for trace and ultra-trace element by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) and multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Sources of errors must therefore be accurately evaluated and avoided at every procedural step. The present study has been focused on analytical method development, optimization and evaluation (including sample preparation, matrix separation, instrumental analysis and data evaluation stages) for isotopic and multi-elemental analyses in environmental samples at trace and ultra-trace levels. The first method tested and optimized has allowed obtaining both osmium concentration and isotopic ratio (187Os/188Os) data together with broad multi-elemental characterization of samples. The procedure was as follows: digestion of small biological samples spiked with Os (enriched in 190Os) followed by concentration and Os isotope measurements by ICP- SFMS, operated with solution nebulization (SN) introduction system and methane addition to the plasma. A specific gas-phase introduction (GPI) system was adopted for samples with low analyte content (<500 pg) for isotopic measurements. Memory effects were avoided with implementation of disposable plastic lab ware. This resulted in a relatively inexpensive and rapid method with high sample throughput capability. SN method limit of detection (MLOD) did not improve compared to previous studies (2 pg g-1), while a MLOD of 0.2 pg g-1 obtained with GPI represents an important improvement, especially taking into account potential further gains due to refined digestion stage. Method reproducibility for 187Os/188Os evaluated using in-house control samples was better than 1.5% RSD. The method, successively applied to a large scale bio-monitoring case, confirmed the presence of an anthropogenic Os in animals from an area affected by emissions from a stainless steel foundry. The second method has been focused on Cd concentration and isotope ratio measurements. Different analytical stages were critically evaluated and optimized for processing carbon-rich environmental samples. Several digestion methods were tested (high pressure ashing, microwave, ultrawave and ashing) followed by ion-exchange chromatography to separate analyte from matrix. Concentrations were measured by ICP-SFMS and subsequently isotopic ratio measurements were performed using Neptune Plus MC-ICP-MS. The latter was tested with two different introduction configurations: a standard SN system and a high sensitivity setup (Aridus II desolvating nebulizer). Overall reproducibility of the method was assessed by replicate preparation and Cd isotope ratio measurements in various environmental matrices (soil, sediments, Fe-Mn nodules, sludge, kidney, liver, leaves, mushroom, lichen) and was found to be better than 0.1‰ (2σ for δ114Cd/110Cd) for the majority of samples. Purification performances were evaluated by analyzing the different elution fractions collected at each separation step by ICP-SFMS. Cadmium recovery in the purified fraction was above 95% for all samples analyzed. Spectrally interfering elements such as Mo and Sn might partially co-elute in the Cd fraction and their effect on isotope ratios was carefully investigated. Though the use of a desolvating nebulizer increases the instrumental sensitivity and reduces oxide formation, at the same time it resulted in degraded in-run precision because of poorer signal stability. Accuracy was difficult to assess due to the absence of certified Cd isotopic values. Therefore, Cd isotope data for several commercially-available reference materials are presented and compared with previously published results where available. The method was then applied to variety of biological samples including birch leaves (Betula pubescenes) collected from various locations and different seasons. Birch leaves showed fractionation towards heavier isotopes with a mean δ114Cd/110Cd of 0.7‰ and found to be influenced by seasonal variations. The reason for such fractionation is assumed to be derived from sample uptake through the root system and translocation in the plant. Cd isotopic patterns were compared with other isotopic systems (Zn, Os, Pb) to provide a more comprehensive view of the observed variations.

Successful mine waste reclamation is a fundamental aspect in mine plan development and is legislated through the European Parliament’s ‘Management of Waste from Extractive Industries Directive (2006/21/EC)’. Field and pilot-scale trials were utilised to evaluate different applications of an alternative cover material, sewage sludge, in its ability to remediate and prevent acid rock drainage formation from sulphidic mine tailings derived from the Kristineberg Zn-Cu mine, northern Sweden. Sewage sludge is an organically-rich waste material generated from the treatment of domestic waste water. It may function suitably as a low permeable barrier against oxygen ingress when compacted or as a surface vegetation substrate. The first study focused on evaluating the effectiveness of a sewage sludge sealing layer, part of a composite dry cover design system. Data on tailings, leachate water and pore gas geochemistry during eight years from two experimental pilot-scale test cells revealed that the sludge was an effective barrier to oxygen influx, which prevented sulphide oxidation and acid rock drainage formation. Sludge-borne metals (Cd, Co, Cu, Fe, Pb, Zn) precipitated and were retained in the underlying tailings due to the reduced conditions produced, resulting in low concentrations of dissolved metals (<10μg/L Cd, Co, Cu, Ni, Pb, Zn) in the drainage, several orders of magnitude lower than that from an uncovered tailings reference cell. However, a 19.6% mass reduction of the sludge due to organic matter degradation may compromise the effectiveness of the cover in the long-term. The second study evaluated the geochemical impact of a field-scale surface application of sewage sludge on the groundwater quality of a formally-remediated sulphidic-tailings impoundment. Thirteen years after initial remediation, 12 000 tonnes of sludge were applied to a depth of 0.3m to re-vegetate and stabilise the pre-existing water-saturated and composite dry cover design systems. After two years, a 17% reduction of the sludge volume occurred due largely to aerobic degradation of the organic matter fraction, leaching of the constituents Ca and S, and partially due to the leaching of Cu, Ni, Pb and Zn. Groundwater data indicated that sludge-borne constituents derived from the dry covered areas were prevented from infiltrating through the low permeable sealing layer. Instead they drained laterally through the protective layer to the impoundment toe and did not reach nor have a negative impact on the tailings groundwater. Oppositely, a major plume of sludge-borne constituents derived from the water-saturated area entered the tailings groundwater vertically unhindered, then dispersed laterally through the tailings due to the dominating hydrogeological regime. The plume migrated underneath the dry composite covered area after 2.2 years, where concentrations of Cu (188µg/L), Fe (254mg/L), Ni (263µg/L), Pb (95µg/L) and Zn (1.55mg/L) peaked. The plume included elevated nitrate concentrations (167mg/L) released from nitrification of ammonium in the sludge, which oxidised pyrite in the tailings. However, the effects were temporary due to declining sludge-borne nitrate and metal release from the sludge due to vegetation establishment after 2 years. The expected duration of the plume to disperse and exit the tailings impoundment is estimated to take another 4 years. In conclusion, these studies have found that sewage sludge can be effectively utilised as a suitable alternative cover material within the study periods observed as a sealing layer and as a final vegetation substrate on composite dry covers, but not water-saturated covered systems for the remediation of sulphidic mine tailings. Further investigations will have to verify the effectiveness of these applications in the long-term.

Information on the occurrence of As species and iron sulphide minerals in tailings is essential for predicting therelease of As over extended period of time. Tailings originating from a goldmine in northern Sweden with low content of trace elements except for As were used for this purpose. The dominating sulphides were pyrrhotite and arsenopyrite. The samples used in the study were post-cyanided, tailings slurries treated with Fe2(SO4)3 and H2O2 to form arsenates and Fe-hydrates for effective As-immobilization. Speciation of the As in ore and tailings samples revealed that mining processes have dissolved the majority of the arsenopyrite in the ore, causing secondary As phases to co-precipitate with newly formed Fe-hydrates. A minor part of the As retained in the tailings was assumed to be As (III)-species. Weathering cell tests (WCT) involving 32 weekly cycles of wetting and air exposure were conducted to assess the effect of weathering on the stability of As in the tailings. As-bearing Fe-hydrates remained intact during the early stages of the WCT; the low release of As during this period was probably due to the dissolution of solubleAs(III)-phases. During the later stages of the WCT, the release of As, Fe and S increased due to pyrrhotite oxidation and the destabilization of As-bearing Fe-hydrates. The majority of the originally present As was still associated with the tailings by the end of the test, but additional pyrrhotite oxidation with the pH falling to &gt;3 could further destabilize these As-bearing Fe-hydrates. In the second part of the study,cyanided tailings were converted into a monolith by using a method called cemented paste backfill (CPB). Two mixtures of CPB were tested; CE with 1 wt. % of cement and CE-FA consisting 2 weight (wt.) % of cement together with 1 wt. % of biofuel fly ash. The stability of As in CPB-masses andun-amended tailings were evaluated using tank leaching tests (TLT) and WCT: s. TheTLT results showed that the CPB mixtures were not suitable for use inunderground backfilling because the As content of the CPB leachates increasedcontinuously over the course of the tests. The proportion of binders inCPB-materials is usually 3-7% because such loadings are required to create amonolithic mass that physically and chemically stabilizes arsenic species intailings. The addition of small quantities of binders in CE and CE-FA maytherefore have been insufficient to ensure that the monoliths were highly saturated, which is required to prevent the transport of oxygen and water through the CPB material. In the WCT, crushed CPB materials were used and the addition of binders caused only a minor increase in the leaching of As relative to that seen with unmodified tailings. The addition of binders has re-located a minor proportion of As in As-bearing Fe-hydrates into less acid-tolerant species. During the later stages of the WCTs, the CPB mixtures were treated with acid in order to consume the buffering minerals and simulate the formation of acid mine drainage (AMD). When acid was added to crushed CPB-materials, As-release increased due to the dissolution of Fe-hydrates. The addition of binders into tailings could pose more resistance to sulphide oxidation, which in turn means that the stability of As-bearing Fe-hydrates could be prolonged on long term. Results from the WCT suggested that the addition of low proportions of binders could have a positive effect on As-leaching in a long term perspective. A relatively new method called “Surfacepaste disposal” (SPD), where mixtures of low proportions of binders and tailings is placed as a cover on the un-amended tailings has shown promising results in terms of decreasing As-leaching and the generation of AMD. Future research will, therefore, focus on the stability of As in SPD-applications.

<p>This study is concerned with speciation and fractionation of the rare earth elements (REE) and calcium (Ca) in aqueous solutions. The aim is to investigate the chemical states and physical sizes in which these elements can be present. The REE (including neodymium) and Ca have contrasting geochemical behavior in aqueous solutions. Ca is a major dissolved element, while the REE are trace components and highly reactive with aquatic particles.</p><p>The major interests of the five papers included in this thesis are the following:</p><p>· Papers I and V deal with the behavior of neodymium (Nd) and its isotopes in the Kalix River and some marine waters.</p><p>· The diffusive gradients in thin-films (DGT) method is developed for measuring Ca and Mg in Paper II.</p><p>· Paper III presents a speciation and fractionation study of Ca in the Kalix and Amazonian rivers.</p><p>· The rare earth elements and their carrier phases are investigated in the Kalix river in Paper IV.</p><p>For most elements a detailed study of speciation and fractionation can not be performed using only one method. This is due to the overall heterogeneity of the material, considering both size and chemical composition, which is present in aquatic solutions. During this project the aquatic geochemistry of the REE and Ca has been studied using mainly three methods; cross-flow filtration (CFF), field-flow fractionation (FFF) and diffusive gradients in thin-films (DGT). Field work has to a large part been conducted in the Kalix River, in northern Sweden, which is one of the last pristine river systems in Europe. Some field work has also been conducted in the Baltic Sea and the Arctic Ocean. Results from Amazonian rivers are also presented.</p><p>These are the main conclusions from this work:</p><p>The DGT technique works equally well for measuring Ca and Mg in natural waters as previously reported for trace metal.</p><p>A significant colloidal phase for Ca could be detected in the Kalix River and in different Amazonian rivers. This was concluded independently using both CFF and FFF.</p><p>Variations in REE signatures in the Kalix River suggests two different pathways for the REE during weathering and release form soil profiles and transport in the river.</p><p>No significant variation in Nd-isotopic composition could be detected in the Kalix River although concentrations varied by a factor of ~10. This suggests that there is one major source for Nd in the river although different pathways for the REE may exist.</p><p>A study of Nd in the Kalix River, the Baltic Sea and the Arctic Ocean showed that the isotopic compositions in the diffusible fractions were similar to water samples. However, the relative amount of diffusible Nd increased with salinity, probably reflecting the lower concentration of colloidal and particulate material in marine waters.</p>

This study is concerned with speciation and fractionation of the rare earth elements (REE) and calcium (Ca) in aqueous solutions. The aim is to investigate the chemical states and physical sizes in which these elements can be present. The REE (including neodymium) and Ca have contrasting geochemical behavior in aqueous solutions. Ca is a major dissolved element, while the REE are trace components and highly reactive with aquatic particles. The major interests of the five papers included in this thesis are the following: · Papers I and V deal with the behavior of neodymium (Nd) and its isotopes in the Kalix River and some marine waters. · The diffusive gradients in thin-films (DGT) method is developed for measuring Ca and Mg in Paper II. · Paper III presents a speciation and fractionation study of Ca in the Kalix and Amazonian rivers. · The rare earth elements and their carrier phases are investigated in the Kalix river in Paper IV. For most elements a detailed study of speciation and fractionation can not be performed using only one method. This is due to the overall heterogeneity of the material, considering both size and chemical composition, which is present in aquatic solutions. During this project the aquatic geochemistry of the REE and Ca has been studied using mainly three methods; cross-flow filtration (CFF), field-flow fractionation (FFF) and diffusive gradients in thin-films (DGT). Field work has to a large part been conducted in the Kalix River, in northern Sweden, which is one of the last pristine river systems in Europe. Some field work has also been conducted in the Baltic Sea and the Arctic Ocean. Results from Amazonian rivers are also presented. These are the main conclusions from this work: The DGT technique works equally well for measuring Ca and Mg in natural waters as previously reported for trace metal. A significant colloidal phase for Ca could be detected in the Kalix River and in different Amazonian rivers. This was concluded independently using both CFF and FFF. Variations in REE signatures in the Kalix River suggests two different pathways for the REE during weathering and release form soil profiles and transport in the river. No significant variation in Nd-isotopic composition could be detected in the Kalix River although concentrations varied by a factor of ~10. This suggests that there is one major source for Nd in the river although different pathways for the REE may exist. A study of Nd in the Kalix River, the Baltic Sea and the Arctic Ocean showed that the isotopic compositions in the diffusible fractions were similar to water samples. However, the relative amount of diffusible Nd increased with salinity, probably reflecting the lower concentration of colloidal and particulate material in marine waters.

Diss. Luleå : Luleå tekniska universitet, 2007. / Härtill 4 uppsatser.

Measurements of snow water equivalent (SWE) constitute an important input to hydrological models used to predict snowmelt runoffs. The new generation of such models use distributed snow data, including distribution of SWE, as input, and rely on it for calibration and validation. Using ground penetrating radar (GPR) from snowmobiles or helicopters is one of the methods to estimate SWE, and it allows for covering large areas in a short period of time. However, the accuracy offered by GPR is detrimentally affected by the presence of liquid water in the snow. This is a problem since when a snowpack is at its peak, and therefore of the largest interest, it has quite often started to melt so there might be liquid water in the snowpack. The present work is an attempt to solve this problem for SWE estimates made by multi-offset GPR operated from a snowmobile. The main idea is to use radar data already available, and to utilize, in addition to two-way travel time, radar wave attenuation, which both depend on snow wetness. Thus obtained liquid water content of a snowpack can be used to get more accurate estimates of SWE.Using radar wave attenuation to obtain liquid water content requires the relationship between liquid water content and electrical conductivity, which has to be established experimentally. The results of several series of experiments, first establishing this relationship for a specific salt content, and then confirming that variation in salt content does not significantly affect it, are presented in this work.However, there remains another problem to be solved. Attenuation caused by energy dissipation in the snow can only be determined from measured radar wave amplitude if losses due to reflection at the snow/ground interface are known. Since a multi-offset GPR system is in fact an array of antennas, several measurements can be made at each point with radar waves reflecting from the ground with different angles of incidence. It should therefore be possible to calculate angle-dependent reflectivity from radar wave amplitudes using Snell's law and one of Fresnel equations. However, applicability of this method in the presence of measurement errors has to be verified. Initial experiments point to problems due to antenna ring-down from the direct wave interfering with the reflected wave, so further tests of the method should be conducted, or ultimately another method to determine reflectivity of the snow/ground interface should be found. Theoretical and experimental results presented in this thesis lead to the conclusion that when SWE is estimated with a multi-offset GPR system, radar wave amplitudes, available in radar data, can be used to establish liquid water content of a snowpack and hence improve the accuracy of SWE estimates, provided that the problem with establishing reflectivity of the snow/ground interface is solved.

Northern Norrbotten County is one of the three major ore producing districts in Sweden. Based on the predominance of epigenetic Cu-Au and Fe-oxide mineralization this region is regarded as a typical IOCG province. The massive to layered Viscaria Cu-deposit is proposed to be a VMS deposit of Besshi-type and is unique in deposit type of the region. The volcaniclastic rocks of the Viscaria Formation hosting the Viscaria deposit belong to the rift related Kiruna Greenstone Group. The Viscaria deposit consists of three stratiform-stratabound mineralized zones: A-, B- and D-zone. Sulphide mineralization of the D-zone differs in structural features, host rock, mineralization style and Fe-oxide dominance over Cu-sulphides compared to the main Cu-ore in the A-zone. These differences between A- and D-zone mineralization styles raise the subject that the D-zone could be of a different origin.   The Kiruna area is mainly covered by glacial-till, which contributes to limited bedrock exposure. This becomes a challenge when exploring for new deposits and highlights the importance of good geological knowledge obtained from existing deposits to carry through successful exploration programs. The objective of this study is to characterize the Fe-Cu-occurrence and the associated alteration halo of the Viscaria D-zone. Alteration halos can reach several kilometres away from the main ore zone and provides mineralogical and chemical signatures that extend the target area significantly in exploration for new deposits. Detailed core logging, optical microscopic studies, lithogeochemistry and electron microprobe analyses was utilized to contribute to a better genetic understanding of the D-zone and the associated hanging wall and footwall alteration features. The study shows that the main ore minerals of the D-zone consist of magnetite and chalcopyrite, and minor pyrite and hematite. The major alteration minerals associated with mineralization are calcite, actinolite/tremolite, epidote, chlorite and also biotite and scapolite in the hanging wall. The most prominent potential ore vector is calcite veins and biotite, as the abundance increase towards the D-zone. D-zone are further characterised by low REE concentrations, similarly to the calcic-dolomite host. The study also shows that the alteration halo of the D-zone is different in the hanging wall compared to the footwall, which is confirmed by the lithogeochemistry and mineral chemistry. The footwall is characterized by spilitization and chlorite alteration. The lithogeochemistry of the D-zone and the hanging wall reveals element mobility of Mg, Ba, Fe, Na, K, Cu and Zn. Mineral chemistry of epidote, amphibole and chlorite shows chemical changes in Fe/Al- and Mg/Fe-ratios. According to the result of this thesis and earlier studies, the D-zone mineralization is suggested to be part of the VMS system forming the stratigraphically above laying A-zone of the Viscaria Cu-deposit.

The potential of utilizing a new form of chemical processing technology called SpinChem® Rotating Bed Reactor (RBR), in combination with different reactive materials, for the purpose of remediating multi-contaminated aquifers under changing environmental conditions, was investigated using laboratory studies and geochemical models. Four different reactive materials, or combinations thereof, were tested: heat-treated peat powder combined with zero-valent iron (ZVI); IronPeat, which consists of peat powder coated with a ferriferous hydrosol (FFH); and a powdered steel waste product. Results showed that the powdered steel waste was compatible with the technology while the peat-based sorbents were not. However, there were no indications that the kinetics of the sorption reactions increased. This was attributed to the fact that the rate-limiting steps, for the binding of the studied metal(loid)s onto iron oxide, are generally considered to be dependent on the later stages of the sorption process related to diffusion mechanisms and not to the rate of mass transfer through the bulk liquid phase, which is what primarily is increased through application of the SpinChem® RBR technology.