• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 92
  • 13
  • Tagged with
  • 105
  • 99
  • 14
  • 13
  • 12
  • 11
  • 10
  • 9
  • 8
  • 7
  • 7
  • 6
  • 5
  • 5
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Speciation and fractionation of Ca and the REE in fresh and marine waters /

Dahlqvist, Ralf. January 2004 (has links)
Diss. (sammanfattning) Stockholm : Univ., 2004. / Härtill 5 uppsatser.
2

Proterozoic crustal evolution in southcentral Fennoscandia /

Appelquist, Karin. January 2010 (has links)
Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2010. / Härtill 5 uppsatser.
3

Mapping of contaminant dispersion from a polluted mining area by geochemical and geophysical methods, Rävlidmyran,northern Sweden : Use of geochemical and geophysical studies to investigate contaminants

Theander, Astrid January 2019 (has links)
After open pit mining, the pit can either be backfilled or be filled with groundwater andbecome a pit lake. These lakes tend to be acidic and contains high concentrations ofmetals, which increases the environmental risks in the area. One of these pit lakes isRävlidmyran in the Skellefte ore district. This problem and this pit lake have created thepurpose of this thesis, which is to compare the different water types connected to an openpit, i.e. groundwater, surface water and the actual pit lake water, and to connect the waterwith geophysical readings. The purpose is also to compare ratios between elements to beable to gain more geochemical information.To gain information about the groundwater, several groundwater pipes have since a longtime back been installed in the area. The groundwater has thereafter regularly beensampled and analysed. The surface water has also been sampled regularly in differentspots. In the pit lake, a depth profile has been created by water sampling at differentdepths in the pit lake. The geophysical measurements used in this thesis are resistivityand induced potential measurements, and measurements were done with the slingrammethod.The water sampling indicated that all three types of water contained elevatedconcentrations of metals. The ratio between (Cu+Zn+Pb)/Na indicated that the pit lakehad the highest value. The measurement also indicated that the highest concentration ofdissolved metals is found under the chemocline in the pit lake, compared with other watertypes. Also, the ratio Fe/S were the highest under the chemocline in the pit lake, whichindicates e.g. dissolution of pyrite. When it comes to the ratio representing e.g. dissolutionof gypsum (Ca/S) it was below 1 all the time, except for in two groundwater pipes. The(Ca+Mg)/Na–ratio had the highest values in the pit lake and that indicates dissolution ofe.g. carbonates. This is not very surprising since the pit lake has been and are limedregularly.The geophysical investigations indicated increased electrical conductivity in a waste rockheap northwest of the pit lake, where the sampling indicated elevated copperconcentrations. The readings also show that the groundwater flow direction is againstLake Hornträsket north of the pit lake. They also indicated potential flow paths for thegroundwater. These can contain elevated concentrations of ore elements, which can beconfirmed by a sampling of the groundwater in that area. From the geophysical data, it isalso possible to see that one of the profiles are located along a possible groundwaterplume, based on a low resistivity area and the shape of the potential plume. / Efter brytning ur ett dagbrott, så kan dagbrotten ur efterbehandlingssyfte till exempel bliåterfyllt med antingen gråberg eller med vatten. Ifall dagbrottet blir återfyllt med vattenoch en dagbrottssjö skapas, så tenderar denna sjö att vara försurad och innehålla förhöjdahalter av metaller. Detta ökar de lokala belastningarna på miljön i området. En av dessadagbrottssjöar är Rävlidmyran som ligger i Skelleftefältet. Denna dagbrottssjö och dessbieffekter har skapat syftet med detta examensarbete, vilket är att jämföra olikavattentyper kopplade till Rävlidmyran (grundvatten, ytvatten och vatten i dagbrottssjön)samt att jämföra geokemin med geofysiska mätningar. Syftet är också att jämföramolkvoter mellan relevanta element för att i sin tur få mer geokemisk information.För att få fram mer information om grundvatten så har flertalet grundvattenrörinstallerats i området sen flera år tillbaka. Därefter har grundvattnet provtagits ochanalyserats regelbundet. Ytvattnet i området har också provtagits. I dagbrottssjön har enprofil tagits fram genom att ta vattenprover på olika djup i sjön. De geofysiskamätningarna som gjorts är resistivitet och inducerad potential mätningar, samtmätningar som utförts med slingram-metoden.Vattenprovtagningarna indikerade att alla tre vattentyper innehåller förhöjda halter avmetaller. Molkvoten (Cu+Zn+Pb)/Na visade att kvoten var högst under kemoklinen idagbrottssjön i jämförelse med de andra två vattentyperna. De kemiska analyserna avvattenproverna av de olika vattentyperna pekade också på att vattnet under kemoklineni dagbrottssjön innehöll en större mängd lösta joner. Kvoten Fe/S var också högst i dettavatten. När det kommer till molkvoten som bland annat representerar gipsutfällning ochgipsupplösning – Ca/S – så var det under 1 i hela området, med undantag för tvågrundvattenrör. Kvoten (Ca+Mg)/Na var högst i dagbrottssjön och det indikerarupplösning av exempelvis karbonater. Detta är inte helt oväntat, då dagbrottssjön kalkatsregelbundet sedan en lång tid tillbaka.De geofysiska utredningarna indikerade på förhöjd elektrisk konduktivitet i ettgråbergsupplag nordväst om dagbrottssjön, där vattenanalyserna påvisade en förhöjdkoncentration av koppar. Mätningarna visade även att grundvattnets riktning var motsjön Hornträsket, som är lokaliserad norr om dagbrottssjön. De indikerade ävenpotentiella flödesvägar för grundvatten. Dessa flödesvägar kan innehålla förhöjda halterav metaller, vilket kan bekräftas med hjälp av provtagningar av grundvatten i området.Från de geofysiska mätningarna är det också möjligt att se att en av profilerna är placeradlängs med en möjlig grundvattenplym, baserat på en låg resistivitet och den potentiellaplymens form.
4

Geochemical and hydrological aspects of interactions between water and mine waste

Shcherbakova, Elena January 2006 (has links)
This thesis presents laboratory studies of sulphidic mine tailings remediated by flooding, and a pilot-scale study of dry cover for remediation of unoxidised sulphide-rich tailings. At the Kristineberg Zn-Cu mine in northern Sweden, sulphide-rich, poorly buffered tailings have been deposited in five impoundments located along a valley. By increasing pH by liming, thereby reducing metal mobility, a water-covered downstream impoundment is made to function as a trap for metals released from the till-covered impoundments upstream. As a result of the liming, a calcite-gypsum sludge has been formed on the tailings. The potential metal release from the sludge during resuspension events and in a long-term perspective was investigated by performing a shake flask test and sequential extraction of the sludge. A laboratory mixing experiment was performed to simulate the flocculation processes that occur in limed tailings ponds if stream water is diverted through a pond as a part of a remediation programme. The laboratory studies showed that the sequentially extracted carbonate and oxide fractions together contained ≥ 97% of the total amount of Cd, Co, Cu, Ni, Pb and Zn in the sludge. The association of these metals with carbonates and oxides appears to result from sorption and/or co-precipitation reactions at the surfaces of calcite and Fe, Al and Mn oxyhydroxides forming in the impoundment. In the shake flask test, remobilisation of Zn, Cu, Cd and Co (at a pH of 7-9) from the sludge resulted in dissolved concentrations of these metals that were significantly lower than those predicted to result from dissolution of the carbonate fraction of the sludge. This may suggest that cationic Zn, Cu, Cd and Co remobilised from dissolving calcite, gypsum and Al oxyhydroxides were readsorbed onto Fe oxyhydroxides remaining stable under oxic conditions. The laboratory mixing experiment showed that the flocculants that settled were rich in C (18 wt%) and acid leachable Fe (14-19wt%). Thus, organic matter and Fe oxyhydroxides appear to form substantial fractions of the flocculants. Trace metal uptake in the flocculants that settled in the mixing bottles resulted in removal of Cd, Co, Cu and Zn from the dissolved phase. Another part this thesis work focuses on the hydrological aspects of dry covers. The water balance in well-defined, pilot-scale systems with various types of dry cover applied on mine tailings at the Kristineberg site has been studied. Experimental studies of water infiltration through dry covers on sulphidic tailings can be used for predicting cover performance and cover design parameters relating to the same climate conditions and the same type of tailings. For this purpose, different multilayer covers have been applied in pilot-scale test cells. Clayey till, sewage sludge, Trisoplast (a mixture of a polymer, bentonite and tailings sand) and fine-grained apatite are used as sealing layers, on top of which a protective cover of unspecified till has been applied. To be able to evaluate the behaviour of the multilayer covers in tailings-impoundment scale, and to predict how the different barrier constructions influence infiltration rate and water balance, the experimental soil covers have been monitored for water percolation, climate conditions and frost penetration. The different infiltration rates in different cells were discussed. The initial results for the first two years of monitoring suggest that the apatite concentrate as a sealing layer is more promising in reducing net infiltration than a 0.3 m thick clayey till. The high fractions of water percolated through the sealing layers (~30% of precipitation) may be explained by the absence of natural run-off from the experimental cells. The results show that snowmelt, freezing of the soil and differences in soil hydraulic properties appear to have effects on the differences in water balance in the cells. / <p>Godkänd; 2006; 20070109 (haneit)</p>
5

Fractionation of the stable silicon isotopes : analytical method developments and selected applications in geochemistry

Engström, Emma January 2007 (has links)
During the last few decades, variations in the 'natural' isotopic abundances of stable elements (termed 'fractionation') have received considerable interest from the scientific community. Though analytical methods and techniques for the measurement of isotopic abundances with adequate figures of merit have been available for light elements (e.g. B, C, N and O) for some time, and the wealth of data produced has secured maturity status for such applications, relatively modest progress in fractionation studies devoted to high-mass elements has been made until recently, mainly because of constraints of the available analytical techniques. The situation has changed drastically with the advent of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), with the number of reports about natural fractionation of Fe, Cu, Zn, Mo, Cd, Sn increasing exponentially during the recent years. In spite of the high Si abundance in nature and the importance of the element in many areas of the Earth sciences (focusing on e.g. weathering, the global Si cycle, paleoclimate studies, paleoceanography, and biological uptake), the available information on Si isotope fractionation remains rather limited due to the laborious and hazardous chemical purification procedures associated with the analyses. The focus of this thesis was the development of analytical methods for the precise and accurate measurements of Si isotope ratios, which is an absolute requirement for meaningful fractionation studies, in various matrices. This work involved detailed studies on sample preparation (including matrix separation) and refining the measurement protocol by using high resolution MC-ICP-MS. In the former stages, quantitative analyte recovery, thorough control of contamination levels and purification efficiency were the major targets, while severe spectral interferences and the need for adequate instrumental mass bias corrections challenged the latter. The performance of the method was tested in the first inter- laboratory performance assessment study of its kind with good results. As limited examples of applications, studies on Si isotope fractionation in aqueous, plant and humus samples were performed utilizing methods developed. The efficient analyte separation, high-resolution capability of the instrument, quantitative Si recovery and accurate mass bias correction using Mg as internal standard, allowed the determination of the Si isotopic composition of natural waters and biological samples with long-term reproducibility, expressed as twice the standard deviation (2σ), equal to or less than 0.10‰ for δ29Si and 0.25‰ for δ30Si. Furthermore, the presence of a challenging spectral interference on 29Si originating from 28SiH+ was revealed during this study, indicating that instrumental resolution in excess of 3500 is required for interference-free Si isotopic analyses. However, despite complete removal of N-, O-, and C-containing interferences appearing on the high-mass side of the Si isotopes, it was found that exact matching of both the acid matrix and the Si concentration are mandatory due to tailing from the abundant 14N16O+ interference on 30Si. This thesis also includes results from the first study of the Si isotopic homogeneity of major biomass components from a defined area in Northern Sweden covered by boreal forest. Since the potential impact of vegetation on the terrestrial biogeochemical cycle has attracted considerable interest, thorough characterization of the Si isotopic composition of the biomass potentially allows the utilization of this isotope system in the assessment of the relative contributions of biogenic and mineral silica in plants, soil solutions and natural waters (including fresh-, brackish- and marine waters). Isotopic analyses of the biological materials yielded a surprisingly homogenous silicon isotopic composition (relative to the NBS28 Si reference material), expressed as δ29Si (2σ), ranging from (- 0.14 ± 0.05)‰ to (0.13 ± 0.04)‰ Furthermore, elemental and isotopic analysis of local airborne particulate matter suggests that vegetation also accumulates silica via incorporation of exogenous Si containing primary and secondary minerals (in addition to root uptake of non-ionic silicic acid), a fact that has been neglected in previously published studies. This strongly indicates that the presence of potential surface contributions must be considered during in situ silicon uptake studies / <p>Godkänd; 2007; 20071011 (ysko)</p>
6

Trace metal speciation in the Baltic sea

Gelting, Johan January 2006 (has links)
Physicochemical speciation of metals in natural waters is very important for understanding their distribution, mobility, bioavailability and toxicity. To be able to understand the behaviour of an aqueous element and the transformation between chemical and physical species, there is a need for reliable methods that enable measurements of specific fractions of metals. Many different techniques are used for metal speciation, of which many suffer from problems. Ultrafiltration has frequently been used to study speciation of metals in natural waters. A possible alternative or complement to ultrafiltration is the technique of diffusive gradients in thin films (DGT), a novel technique which provides an in situ measurement of labile metal species. DGT accumulates metals in a time- integrated way and produces a mean concentration over the chosen deployment period. DGT- labile metals may be regarded as a measure of the bioavailable amount, since the DGT simulates the diffusion process that occurs when a metal is diffusing into a cell membrane. This thesis is focused on the DGT technique for sampling and determination of labile species in the Baltic Sea. The aim of this study was to compare the trace metal speciation methods; DGT, 1 kDa ultrafiltration, 0.22µm membrane filtration and unfiltered water, to study the dynamics for the DGT labile fractions to find out which mechanisms that control the labile fraction. In 2003 and 2004, DGT and 1 kDa ultrafiltration were simultaneously applied at two sampling stations in the Baltic Sea with different salinity and trace metal concentrations. Baltic Sea concentrations of Mn, Zn and Cd measured by DGT during 2004 were similar to the concentrations measured in 1 kDa ultrafiltered samples, especially for Mn. Cu and Ni, showed noticeably higher concentrations in ultrafiltered water than DGT-labile concentrations. This indicates the existence of low molecular weight Cu and Ni species, small enough to pass through the 1 kDa, but can also be a sign of high degree of organic complexation which will lead to an underestimation in the DGT labile fraction. The dynamics of DGT-labile trace metals during 2004 show quite large variations during the season at 0.5 to 40 meters depth. From May to August, Cu, Cd and Mn drop about 35, 50% and 60% respectively. Ni decreased about 25% late April to late June but was slightly recovered at late season. The only elements that showed good correlation between DGT-labile species to dissolved phase (0.22µm filtrate) was Mn and Cd. DGT labile Mn is probably controlled by oxidizing bacteria during most of the sampling period, and DGT labile Co, Cd and to some extent Zn seem to follow this process. It should be noted that Mn is closely correlated to P, a relationship which need further investigations. Cu and Ni are controlled by other processes, where influence from primary production may be one. This is the first comparison of DGT and 1 kDa ultrafiltration regarding trace metals in brackish waters. Strong correlations between the methods imply that DGT can be a simple alternative to an ultrafiltration procedure. It is also the first study on trace metals in the Baltic Sea where measurements were performed at high temporal resolution during several months. / <p>Godkänd; 2006; 20061124 (ysko)</p>
7

Further characterisation and applications of the diffusive gradients in thin films technique : In situ measurements of anions and cations in environmental waters

Österlund, Helene January 2011 (has links)
As both the toxicity and the mobility of trace elements are related to chemical forms present, robust methods for element speciation analysis are of great interest. During the last 15 years, hundreds of scientific articles have been published on the development and applications of the diffusive gradients in thin films (DGT) passive sampling technique. The aim of this thesis was to explore new application areas as well as carry out further characterisation of DGT-adsorbents already on the market. The commercially available DGT containing ferrihydrite adsorbent, currently in use for the determination of phosphate and inorganic arsenic, was characterised with respect to anionic arsenate, molybdate, antimonate, vanadate and tungstate determination. Tests were performed in the laboratory as well as in the field. Diffusion coefficients were determined for the anions using two different methods with good agreement. Simultaneous measurements of arsenate were conducted as quality control to facilitate comparison of the performance with previous work. The ferrihydrite-backed DGT was concluded useful for application over the pH-range 4 to 10 for vanadate and tungstate, and 4 to <8 for molybdate and antimonate. At pH values ≥8, deteriorating adsorption was observed. Further investigations of the ferrihydrite-DGT device were done with respect to organic arsenic species. From previous research it is understood that the two most prevalent forms of organic arsenic in natural waters, monomethylarsinate (MMA) and dimethylarsonate (DMA), adsorb to ferrihydrite. It was concluded that MMA and under some conditions DMA are accumulated and might therefore be included in total arsenic measurements. A method for speciation of inorganic As, DMA and MMA was described. DGT sampling was applied at three stations, with different salinities, in the brackish Baltic Sea. Time series as well as vertical profiles were taken and complementary membrane- (<0.22 μm) and ultrafiltrations (<1 kDa) were conducted on discrete samples collected at 5 m depth. A combination of a restricted pore (RP) version of DGT and the normal open pore (OP) DGT, both loaded with Chelex cation exchanger, was used for speciation of copper and nickel. Due to minimal differences in results between the OP- and RP-DGTs it was suggested that the complexes were smaller than the pore size of the RP gel (~1 nm) resulting in both DGTs accumulating essentially the same fraction. Furthermore, there seemed to be a trend in copper speciation indicating a higher degree of strong complexation with increasing salinity. The low salinity stations are more impacted by fluvial inputs which will likely affect the nature and composition of the organic ligands present. Assuming that copper forms more stable complexes with ligands of marine rather than terrestrial origin would be sufficient to explain the observed trend. Additionally, uranium results from the same sampling tours were used to evaluate OP-DGT for in situ uranium measurements. Previous research has focused on laboratory studies for characterisation of a range of suitable uranium adsorbents, including Chelex. From the Baltic Sea study, a strong correlation between DGT-labile uranium and pH was revealed. The correlation could not be associated to organic complexation, since the ultrafiltration results implicated that uranium was truly dissolved. Instead it must be attributed to the formation of stable inorganic anionic uranyl-carbonate complexes, the stability of which increases with increasing numbers of carbonates and pH. Transplanted aquatic moss has commonly been used to monitor bioavailable trace metal contaminations in freshwater. Like the DGT technique the method has the advantage of generating time-weighted averaged concentrations. The DGT technique has in several previous studies been suggested to mimic biological uptake of trace metals. Four speciation/fractionation techniques – DGT, transplanted aquatic moss, ultrafiltration (1 kDa) and membrane filtration (0.22 μm) – were used in parallel for measurements of Al, Cd, Co, Cu, Fe, Mn, Ni and Zn in a contaminated freshwater stream in northern Sweden. Differences and similarities between the methods were investigated and how these depend on geochemical water quality. Strong correlations between DGT-results and the concentrations in the filtrate (<0.22 μm) and ultrafiltration permeate for Al, Cu, Cd, Co and Zn were detected and, generally, elevated trace metal concentrations were found in the transplanted moss, compared to moss from the non-polluted reference stream. However, no correlation between moss and DGT-labile concentrations could be discerned. / Godkänd; 2011; 20110921 (helost)
8

Method development for isotope analysis of trace and ultra-trace elements in environmental matrices / Metodutveckling för isotopanalyser av spår- och ultra-spårelement i miljömatriser

Pallavicini, Nicola January 2016 (has links)
The increasing load of toxic elements entering the ecosystems, as a consequence of anthropogenic processes, has grown public awareness in the last decades, resulting in a great number of studies focusing on pollution sources, transport, distribution, interactions with living organisms and remediation. Physical/chemical processes that drive the uptake, assimilation, compartmentation and translocation of heavy metals in biota has received a great deal of attention recently, since elemental concentrations and isotopic composition in biological matrices can be used as  probes of both natural and anthropogenic sources. Further they can help to evaluate fate of contaminants and to assess bioavailability of such elements in nature. While poorly defined isotopic pools, multiple sources and fractionating processes add complexity to source identification studies, tracing is hindered mainly by poorly known or unidentified fractionating factors. 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. Instrumental development and refining separation schemes have allowed higher quality data to be obtained and played a major role in the recent progress of the field. The use of modern techniques such as inductively coupled plasma sector field mass spectrometry (ICP-SFMS) and multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for trace and ultra-trace element concentrations and isotope ratio measurements have given new opportunities.  However, sources of errors must be accurately evaluated and avoided at every procedural step. Moreover, even with the utilization of sound analytical measurement protocols, source and process tracing in natural systems can be complicated further by spatial and temporal variability. The work described in the present thesis has been focused primarily 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. Special attention was paid to evaluate strengths and limitations of the methods as applied to complex natural environments, aiming at correct interpretation of isotopic results in environmental forensics. The analytical protocols covered several isotope systems of both stable (Cd, B, Cr, Cu, Fe, Tl and Zn) and radiogenic (Os, Pb and Sr) elements. Paper I was dedicated to the optimization and testing of a rapid and high sample throughput method for Os concentrations and isotope measurements by ICP-SFMS. If microwave (MW) digestion followed by sample introduction to ICP-SFMS by traditional solution nebulization (SN) offered unparalleled throughput important for processing large number of samples, high-pressure ashing (HPA) combined with gas-phase introduction (GPI) proved to be advantageous for samples with low (below 500 pg) analyte content. The method was applied to a large scale bio-monitoring case, confirming accumulation of anthropogenic Os in animals from an area affected by emissions from a stainless steel foundry. The method for Cr concentrations and isotope ratios in different environmental matrices was optimized in Paper II. A coupling between a high pressure/temperature acid digestion and a one pass, single column matrix separation allowed the analysis of chromites, soils, and biological matrices (first Cr isotope study in lichens and mosses) by ICP-SFMS and MC-ICP-MS. With an overall reproducibility of 0.11‰ (2σ), the results suggested a uniform isotope composition in soil depth profiles. On the other hand a strong negative correlation found between δ53Cr and Cr concentrations in lichens and mosses indicates that airborne Cr from local anthropogenic source(s) is depleted in heavy isotopes, therefore highlighting the possibility of utilization of Cr isotopes to trace local airborne pollution source from steel foundries.   Paper III describes development of high-precision Cd isotope ratio measurement by MC-ICP-MS in a variety of environmental matrices. Several digestion methods (HPA, MW, ultrawave and ashing) were tested for sample preparation, followed by analyte separation from matrix using ion-exchange chromatography. The reproducibility of the method (2σ for δ114Cd/110Cd) was found to be better than 0.1‰. The method was applied to a large number of birch leaves (n&gt;80) collected at different locations and growth stages. Cd in birch leaves is enriched in heavier isotopes relative to the NIST SRM 3108 Cd standard with a mean δ114Cd/110Cd of 0.7‰. The fractionation is assumed to stem from sample uptake through the root system and element translocation in the plant and it exhibits profound between-tree as well as seasonal variations. The latter were compared with seasonal isotopic variations for other isotopic systems (Zn, Os, Pb) in the same trees to aid a better understanding of underlying processes. In Paper IV the number of isotope systems studied was extended to include B, Cd, Cu, Fe, Pb, Sr, Tl and Zn. The analytical procedure utilized a high pressure acid digestion (UltraCLAVE), which provides complete oxidation of the organic material in biological samples, and a two-column ion-exchange separation which represents further development of the separation scheme described in Paper III. Such sample preparation ensures low blank levels, efficient separation of matrix elements, sufficiently high analyte recoveries and reasonably high sample throughput. The method was applied to a large number of biological samples (n&gt;240) and the data obtained represent the first combined characterization of variability in isotopic composition for eight elements in leaves, needles, lichens and mushrooms collected from a geographically confined area. To further explore the reason of variability observed, soil profiles from the same area were analyzed for both concentrations and isotopic compositions of B, Cd, Cr, Cu, Fe, Pb, Sr, Tl and Zn in Paper V. Results of this study suggest that the observed high variability can be dependent on operationally-defined fractions (assessed by applying a modified SEP to process soil samples) and on the typology of the individual matrix analyzed (assessed through the coupling of soil profile results to those obtained for other matrices: lysimetric waters, mushrooms, litter, needles, leaves and lichens). The method development conducted in this work highlights the importance of considering all possible sources of biases/errors as well as possibility to use overlapping sample preparation schemes for multi-isotope studies. The results obtained for different environmental matrices represent a starting point for discussing the role of natural isotopic variability in isotope applications and forensics, and the importance of in-depth knowledge of the multiple parameters affecting the variability observed.
9

Environmental applications of biogeochemical data from Geological Survey of Sweden

Lax, Kaj January 2005 (has links)
The Geological Survey of Sweden, SGU, has carried out geochemical mapping for several decades. In 1983, two regional mapping programmes were initiated, aiming at a nation wide coverage. While one of the programmes, till geochemical mapping, was focussed mainly on production of regional baseline information for mineral exploration purposes, the second programme was more adapted to environmental issues. This second programme constitutes sampling of living matter (roots of Carex species, Filipendula Ulmaria, and the bryophyte Fontinalis Antipyretica) in minor streams, and is called biogeochemical mapping. Despite more than twenty years of mapping, several aspects of the method and its results still remain unexplored. Furthermore, results from the biogeochemical mapping programme have traditionally been expressed as residuals (contents in ash, contents of iron and manganese, and loss on ignition have been used as independent variables). This residual method however is not used in the Fontinalis antipyretica monitoring method developed by the Swedish Environmental Protection agency (SEPA), thus use of the SGU regional data set as baseline information in a SEPA context is very difficult. Therefore, a transition to dry weight is desirable. This however introduces several problems, e. g. for chromium. Following an introduction to the development and current status of the geochemical mapping programmes, two environmental applications of the biogeochemical dataset have been developed through a combination of statistical and geostatistical methods. In the first, subsets of the biogeochemical database have been created and used in order to determine possible species dependent effects, spatial correlation and influence of main elements like titanium, iron, aluminium, silica, and manganese on chromium. In the second, relations between the chemical composition of samples and areas known (and suspected) to host acid sulphate soils are studied. The species studied vary somewhat regarding metal contents. Such differences are assumed to be related to uptake mechanisms. However, for most elements the differences are much smaller than the spatial variance and the results from the mapping programme can be used without respect to species. Other geochemical databases (till and soil), as well as geological data, have been used in order to examine the geochemical properties of the biogeochemical samples, and factors affecting spatial distribution, e.g. relationships with quaternary deposits. Chromium contents in biogeochemical samples are strongly related to titanium, silica, zirconium and ash content. This correlation is not present in glacial till and other quaternary deposits. Normalisation of chromium by titanium is an efficient tool to separate anthropogenic point source pollution from chromium derived from natural sources. Acid sulphate soils have a strong impact on surface waters, and ecosystems therein. The metal contents of biogeochemical samples in two separate areas where acid sulphate soils occur display similar features as stream water. Of the elements studied, levels of yttrium, nickel, cobalt, zinc, sulphur, (and others) are significantly higher in samples collected in areas with postglacial clays and gyttja containing soils, deposits that are known to comprise acid sulphate soils. The metal content of the biogeochemical samples can be used in order to detect active acid sulphate soils. / <p>Godkänd; 2005; 20061211 (haneit)</p>
10

Sulphide oxidation, oxygen diffusion and metal mobility in sulphide-bearing mine tailings in Northern Sweden

Alakangas, Lena January 2006 (has links)
Large quantities of sulphide-bearing mining wastes produced from ore processing are deposited throughout the world. Sulphide oxidation in the wastes may release acidic water with high concentrations of metals to the environment. Remediation strategies are usually site specific, since the physical and chemical properties of the wastes vary. Therefore, sulphide oxidation, oxygen diffusion and metal mobility in unoxidised and oxidised, remediated and unremediated wastes have been studied in the present work. The efficiency of different cover systems on unoxidised tailings from Kristineberg, were studied in pilot-scale test cells (5*5*3 m3)under field conditions. Clayey till, sewage sludge, apatite and Trisoplast were used as sealing layers and unspecified till as a protective cover. In one cell tailings were left uncovered. Unoxidised tailings in the test-cells in the initial stage after deposition showed relatively low sulphur release (600- 800 mg/l)in leachate waters, which probably was an effect of high moisture content in the tailings prior to deposition. Near-neutral pH found in the leachates was an effect of neutralisation by carbonate minerals present and lime (Ca(OH)2) added prior to deposition. Similar sulphur concentrations were found also in the uncovered tailings. The sulphide oxidation rate increased with time in the uncovered tailings, and decreased in the covered. The lowest oxygen concentrations were observed below the cover system with sewage sludge, which was the most effective barriar against oxygen in a short-term perspective. The oxygen fluxes through the clayey till and apatite layers were within the same magnitude and varied between 0.5 and 4 mole/year,m2. The Trisoplast layer seemed to have failed as a barrier against oxygen. Tailings studied at field scale at Laver and Kristineberg had oxidised for more than 50 years. The tailings at Kristineberg have high pyrite content (c.25% and 50%) and those at Laver have low grade of pyrrhotite (2-3%). The Laver tailings are unremediated, while at Kristineberg the tailings were remediated in 1996. The transport of metals in the drainage water at Laver decreased during a study period of 8 years. The transport of dissolved sulphur indicated a declining trend of sulphide oxidation rate in the tailings, which was confirmed by oxygen measurements in the tailings and weathering rate estimations. The decline was considered to be natural as a result of the increased distance that oxygen has to travel to reach unoxidised sulphide grains. The major part of the amounts of metals released by sulphide oxidation were secondarily retained in the tailings, and to a small extent in layers cemented by jarosite and Fe-(oxy)hydroxides. Sequential extraction of these layers showed that metals such as Cu and Pb were mostly associated with crystalline Fe-(oxy)hydroxides. Most important retention mechanism was, however, sorption onto minerals surfaces below the oxidation front. The studied Impoundment 1 at Kristineberg was remediated by two different methods; on one part a dry cover consisting of a sealing layer and a protective cover were applied, and the groundwater table was raised and a single dry cover applied on the other part. When the groundwater table was raised in oxidised tailings, secondarily retained metals such as Fe, Mg, Mn, S and Zn were remobilised resulting in increased concentrations in the groundwater. The concentrations declined with time, due to dilution by inflowing uncontaminated water. Decreased concentrations of Fe, Mg, Mn, S and Zn were observed also in the groundwater below the dry cover as the amount of percolating water decreased. The concentrations of trace elements such as Cd, Co, Cr, Cu, Ni and Pb were almost depleted in the groundwater, since these metals were retained within the tailings by mechanisms such as co-precipitation, precipitation and sorption. Analysis of pyrite grains by LA-ICP-SMS showed that pyrite surfaces were important for retention of As and Cu, in particular, but also for Cd and Zn. This study shows that the physico-chemical conditions expressed by pH and redox potential have a large impact on element mobility’s. For example, As was mobilised as a result of remediation, while the concentrations of most metals decreased in the drainage waters. / Godkänd; 2006; 20061116 (pafi)

Page generated in 0.0299 seconds