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  • 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.
61

Chemical and mineralogical signatures of oxygenic photosynthesis in Archean and Paleoproterozoic sediments / Signatures chimiques et mineralogiques de la photosynthèse oxygénique dans les sédiments de l’Archéen et du Paleoproterozoïque

Hubert, Axelle 16 December 2015 (has links)
L’émergence des bactéries photosynthétiques oxygéniques (BPO), ou cyanobactéries, est probablement l’évènement le plus important de l’histoire de la Terre, depuis l’apparition de la vie elle-même. Par la libération d’O2 dans l’environnement, les BPO ont conduit à l’oxygénation de notre planète, jusqu’alors anoxique, et au développement de la vie complexe. Cependant, cette évolution n’est toujours pas datée. Dans cette étude, j’ai cherché à identifier des signatures chimiques spécifiques aux BPO, in situ à l’échelle du μm, dans des tapis microbien fossiles datant de 3,45 à 1,88 Ga, recouvrant ainsi une période allant de la Terre anoxique à la Terre oxygénée après le « Great Oxidation Event » (GOE). Nous avons utilisé la microscopie optique, la spectroscopie Raman, le MEB/EDX, l’EPMA, la μ-XRF à rayonnement synchrotron (SR-XRF), et des analyses isotopiques. Une nouvelle méthode de quantification élémentaire pour SR-XRF, ainsi qu’une nouvelle méthodologie de préparation d’échantillons ont été developpés. Les résultats obtenus par EPMA et μ-XRF montrent que, dans certains contextes de déposition, un enrichissement en lanthanides (par exemple La, Sm, Gd) de cellules fossiles, et un enrichissement en Cu de pyrites diagénétiques formées en association avec des BPO, pourraient représenter des signatures chimiques spécifiques aux BPO. Suite à ces résultats, je propose que les BPO ont évolué entre 3,33 et 2,98 Ga. Je propose que les techniques élémentaires telles que l’EPMA et la μ-XRF sont les techniques les plus appropriées pour trouver des signatures chimiques spécifiques aux BPO et contraindre leur émergence dans le temps. / The evolution of oxygenic photosynthetic bacteria (OPB) is probably the most important biological event of Earth’s history since the emergence of life itself. The release of their by-product O2 in the environment, which was globally anoxic, fundamentally changed the face of the Earth and led to the development of complex life. However, the specific timing of this evolutionary step remains unclear. This study is based on the search for in situ chemical signatures of OPB at the microbial (μm) scale, within fossilized microbial photosynthetic mats in Archean and Paleoproterozoic sediments dated between 3.45 Ga and 1.88 Ga, i.e. spanning the anoxic Earth to the aftermath of the GOE. We used optical microscopy, Raman spectroscopy, SEM/EDS, EPMA, synchrotron radiation μ-XRF, and isotope analytical techniques. The μXRF results were improved by the use of a new sample preparation method and a new quantification method, both developed during this study.Results obtained by EPMA and μXRF show that, under certain depositional contexts, enrichment in lanthanides (such as Sm, La and Gd) in individual OPB cells, as well as a Cu enrichment in diagenetic pyrites formed in association with OPB, may represent chemical signatures of OPB. I propose that OPB evolved sometime between 3.33 Ga and 2.98 Ga. Also, I argue that elemental techniques such as EPMA and μ-XRF are the most suitable techniques to find chemical signatures of OPB and constrain the timing of their emergence.
62

Identifying Quaternary Climate Change with XRF Analysis on Loess From South-Western England / Identifikation av kvartära klimatförändringar med XRF-analys på lössjordar från sydvästra England

Kronborg, Pelle January 2020 (has links)
Huge changes in climate occurred at the end of the last Quaternary glaciation. The end of this glaciation corresponds with the end of Pleistocene with its repeated glacial cycles and the start of the current geological epoch, the Holocene interglacial. The climate at this time was characterized by increasing temperatures and an increase in rainfall. This project focuses on understanding and examining these changes in climate using loess deposits from south-western England. Loess is an aeolian sediment and covers around 10 % of the Earth’s land surface and these deposits are excellent archives of past climate. Investigating loess can give understanding of past regional and local wind circulation patterns, atmospheric dustiness as well as weathering conditions. Studying paleoclimate is important since studying and understanding trends in past climate can increase our understanding of how the climate will change in the future. This study examined loess from two sites in south-western England, Porth Cressa and Lowland Point. These are relatively thin deposits; Lowland Point has a thickness of 180 cm and Porth Cressa has a thickness of 97 cm. England lacks the thick loess deposits that can be found in other parts of the world and thus the study of English loess has mostly been neglected. These deposits thus could contain unutilized information about paleoclimate. The elemental composition of the samples was examined using X-Ray Fluorescence (XRF). With the measured elemental composition, it’s possible to use weathering indices to see trends in postdepositional weathering. Low weathering intensities indicate a colder and drier climate, while higher weathering intensities indicate a warmer and more humid climate. The results from the weathering indices were plotted against depth at the two sites to identify changes in weathering and hence climate over time. Compared with the results from previous studies the results from some weathering indices seemed credible. Previous studies have indicated that the Chemical Proxy of Alteration (CPA) is the most appropriate weathering index for loess and the results from this study supports that theory. The results from the CPA show a trend with decreasing weathering intensities followed by a trend with increasing weathering intensities This implies that there was a period with decreasing temperatures/humidity followed by a period with increasing temperature humidity sometime at the end of the last glaciation. The geochemical data also showed support for a previous archaeological theory that there has been human reworking in the upper horizons at Lowland Point. / Slutet av den sista kvartära glaciationen var en tid med stora klimatförändringar. Denna tid sammanfaller med slutet av Pleistocene och dess glaciära cyklar samt starten på den nuvarande geologiska epoken, Holocen. Klimatet vid den här tiden karaktäriserades av ökande temperaturer och ökande nederbörd. Det här projektet fokuserar på att granska och förstå dessa klimatförändringar med hjälp av lössjordar från sydvästra England. Löss bildas av vindburet sediment och täcker ungefär 10 % av jordens landyta, dessa avlagringar är utmärkta arkiv för historiskt klimat. Att undersöka lössjordar kan ge information om historiska regionala och lokala vindcirkulations-mönster, vittringsförhållanden samt mängden damm i atmosfären. Att undersöka paleoklimat är viktigt då förståelse för trender i tidigare klimat kan ge oss förståelse för hur klimatet kommer förändras i framtiden. Den här studien undersökte löss från två platser i sydvästra England, Lowland Point och Porth Cressa. Dessa avlagringar är relativt tunna; Lowland Point har en tjocklek på 180 cm och Porth Cressa har en tjocklek på 97 cm. England har inte de tjocka lössavlagringarna som går att hitta i andra delar av världen och därför har lite forskning utförts på brittiskt löss. Dessa avlagringar kan alltså innehålla oanvänd information om paleoklimat. Provernas grundämnessammansättning undersöktes med X-Ray Fluorescence (XRF). Med den uppmäta grundämnessammansättningen är det möjligt att använda vittringsindex för att se trender i vittring efter deposition. En låg vittringsintensitet indikerar ett kallare och torrare klimat medan en högre vittringsintensitet indikerar ett varmare och fuktigare klimat. Resultaten plottades mot djup för att visuellt identifiera förändringar i klimatet över tid. Vid jämförelse med tidigare studier verkade resultaten från vittringsindexen trovärdiga. Tidigare studier har föreslagit att CPA (Chemical Proxy of Alteration) är det mest lämpliga vittringsindexet för lössjordar och resultaten från denna studie stödjer den teorin. Resultaten från CPA visade på en trend med minskade vittringsintensitet följt av en trend med ökande vittrings intensitet. Detta antyder att det var en period med minskande temperatur/fuktighet följt av en period med ökande temperatur/fuktighet runt slutet av den senaste istiden. De geokemiska resultaten stödde också den tidigare arkeologiska teorin att mänsklig aktivitet har påverkat de övre horisonterna vid Lowland Point.
63

Full-field PIXE imaging using a Colour X-ray Camera: Advantages and drawbacks in elemental mapping of large areas with a poly-capillary optics

Buchriegler, Josef 31 May 2021 (has links)
A novel combination of a full-field X-ray detector and particle-induced X-ray emission (PIXE) as an established analytical method has been assembled and examined at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The so-called Colour X-ray Camera (CXC) based on a pn-junction charge-coupled device (pnCCD) is interconnected with a poly-capillary optics (PCO) for the purpose of X-ray imaging. This first combination of PIXE as a lowbackground excitation method and the approach of full-field imaging is likely to close the gap between fast and sensitive investigations of large sample surfaces. The assembly called full-field PIXE (FF-PIXE) is intended for laterally resolved and quantifiable surveys of large geological samples with respect to their trace elemental composition. The PCO comprising hundred thousands of capillaries with inner diameters of about 20 µm is employed in order to map the specimen’s characteristic X-ray response induced by 3 MeV protons provided by a 6 MV tandem-accelerator. The subsequent pnCCD-chip comprising 264×264 pixels is capable of individually detecting X-ray photons in the energy range from 1 to 20 keV on a 12×12 mm² large field of view. The camera’s native lateral resolution could be determined to be 76 µm in the medium energy range, which is basically restricted by the pixel dimensions (48×48 µm²). Extensive experimental tests investigating the concept of sample 'illumination', X-ray transmission through the PCO, and imaging properties of the CXC, yielded substantial insights allowing to judge the new concept of X-ray imaging. While the variability of excitation intensity was proven to be better than 10% and the homogeneous response of the detector was verified, energy-dependent imaging impairments arose from the PCO. In comparative measurements at imaging systems using photons and electrons for excitation, both the full field approach and PIXE as the method of choice could be confirmed to be capable of meeting the initial objectives. In addition, enhancement techniques have been successfully tested to overcome downsides arising from the PCO’s transmission characteristics. Apart from suppressing the hexagonal pattern and a radial unevenness caused by the PCO, the system’s lateral resolving power could be improved towards 63 µm when using the 1:1 optics. The investigations have revealed that, at present, the complex transmission nature of the PCO is a main obstacle in obtaining quantitative results. A number of parameters (e.g. frame readout speed) and dependencies (e.g. lateral resolution vs. elemental sensitivity) have nevertheless been identified and explored the understanding of which will help to move forward 'on the road to metrology'. / Die neuartige Kombination eines Vollfeld-Röntgendetektors und partikelinduzierter Röntgenemission (PIXE: 'Proton-Induced X-ray Emission') als etablierte Analysemethode wurde am Helmholtz-Zentrum Dresden-Rossendorf (HZDR) aufgebaut und erforscht. Die sogenannte Röntgenfarbkamera (CXC: 'Colour X-ray Camera') basiert auf Ladungskopplung mit p-n-Übergängen (pnCCD: 'pn-junction Charge-Coupled Device') und ist zwecks Abbildung mit einer Polykapillaroptik (PCO: 'Poly-Capillary Optics') gekoppelt. Dieser erstmalige gemeinsame Einsatz von PIXE, als Analysemethode mit niedrigem Untergrund, und dem Ansatz der Vollfeldabbildung eignet sich, um die Lücke zwischen schneller und empfindlicher Analyse großer Probenoberflächen zu schließen. Die als full-field PIXE (FF-PIXE) bezeichnete Anlage ist für ortsaufgelöste und quantifizierbare Untersuchungen großer geologischer Proben konzipiert und soll insbesondere deren Spurenelementverteilung analysieren. Die charakteristische Röntgenstrahlung wird mit 3 MeV-Protonen, die von einem 6 MV-Tandembeschleuniger bereit gestellt werden, induziert. Die ortsaufgelöste Abbildung dieser induzierten Strahlung wird mittels hunderttausender Kapillaren (je ca. 20 µm Innendurchmesser) realisiert. Der nachgelagerte aus 264×264 Pixeln bestehende pnCCD-Chip ist in der Lage, Röntgenphotonen im Energiebereich von 1 bis 20 keV aus einem 12×12 mm² großen Sichtfeld einzeln zu erfassen. Im mittleren Energiebereich wurde für die Kamera eine native Ortsauflösung von 76 µm ermittelt, die im Wesentlichen durch die Pixeldimensionen (48×48 µm²) bestimmt ist. Umfangreiche experimentelle Tests, die das Konzept der Probenausleuchtung, der Röntgenübertragung durch die PCO und die Abbildungseigenschaften der CXC untersuchten, führten zu wesentlichen Erkenntnissen, die die Beurteilung des neuen Abbildungskonzepts für Röntgenfluoreszenz ermöglichen. Während die Variabilität der Anregungsintensität nachweislich besser als 10% ist und die homogene Empfindlichkeit des Detektors verifiziert wurde, ergaben sich energieabhängige Beeinträchtigungen der Bildübertragung durch die PCO. Vergleichsmessungen mit bildgebenden Systemen, die Photonen und Elektronen zur Anregung verwenden, konnten bestätigen, dass sowohl der Vollfeldansatz, als auch PIXE als Methode der Wahl zur Erreichung der ursprünglichen Ziele geeignet sind. Darüber hinaus wurden verschiedene Techniken zur Bildverbesserung erfolgreich getestet, die durch die PCO verursachte Abbildungsfehler korrigieren. Abgesehen von der Unterdrückung hexagonaler Muster und der Korrektur radialer Ungleichmäßigkeiten konnte das laterale Auflösungsvermögen des Systems bei Verwendung der 1:1-Optik auf 63 µm verbessert werden. Die Untersuchungen haben ergeben, dass die komplexen Übertragungseigenschaften der PCO derzeit eine der größten Hürden sind, um quantitative Ergebnisse zu erzielen. Dennoch wurde eine Reihe von Parametern (z.B.Auslesegeschwindigkeit) und Abhängigkeiten (z.B. Ortsauflösung vs. Elementempfindlichkeit) identifiziert und untersucht, deren Verständis dazu beitragen wird, auf dem Weg zu quantitativen Ergebnissen, voran zu kommen.
64

XRF-mätning av tungmetaller i bottensediment under vatten

Gonzalez, Charlotte January 2021 (has links)
Syftet med denna undersökning har varit att besvara frågan om röntgenfluorescens är en bra metod för att mäta kvicksilver i bottensediment under vatten. Undersökningen har genomförts genom ett fysiskt experiment och kräver någon form av ett röntgenfluorescenssystem. Ett röntgenfluorescenssystem ger ett fluorescensspektrum som visar en intensitet av röntgenstrålar i antalet fotoner per sekund (counts) som funktion av energi i elektronvolt. Detta kan avslöja vilka grundämnen som befinner sig i fiberbanken och hur mycket av grundämnet. Röntgenfluorescens används redan i många olika applikationer, exempelvis i matindustrin, gruvor och för analys inom forskning. Denna undersökning har visat att röntgenfluorescens även fungerar för mätningar under vatten men kräver mer optimering för bättre precision.
65

Rozvoj hospodářských aktivit na území římských provincií Thrákie a Moesie Inferior se zaměřením na sklářskou výrobu. / Development of manufacturing/economical aspects in roman provinces Thracia and Moesia Inferior with focusing on glassmaking.

Čisťakova, Viktorija January 2021 (has links)
The work presented here focuses on the development of economic activities in the provinces of Thrace and Moesia Inferior (in today's Bulgaria), specifically on the problematic of glassmaking in Roman period and the Late Antiquity. In my work I have focused on the systematic interpretation of the economical development of the rural environment in a context of social, political and economic transformation during Roman rule. The second part of the work presents the glassmaking in the Roman Empire - its beginning, the development of certain technological processes and the specifics of trade activities with raw glass and finished glass products. A collection from the Roman site of Yurt-Stroyno was selected as a case study (during seasons 2012-2014) 1413 fragments of glass were found here. The main aim of the presented study is a typological analysis of the glass finds, supplemented by an analysis of the material composition of selected artifacts. Chemical XRF analyses of the material composition were applied due to clarify the chronological framework of the study group, to determine the source of raw glass for the local glassworks and to raise awareness of Roman and late antique glass in southeastern Bulgaria. 116 samples from the Yurta-Stroyno site were analysed. The selection of samples was carried...
66

XRF-analys av förorenad mark : undersökning av felkällor och lämplig provbearbetning / XRF-analysis of contaminated soil : a study of error sources and suitable sample preparation

Kjellin, Johan January 2004 (has links)
<p>X-ray fluorescence (XRF) detection of heavy metals is a cost- and time-effective method for investigation of polluted areas. Compared to laboratory analysis, XRF analysis is limited by high detection limits and uncertainties in some situations. Preparation of samples is known to affect the results of measurements.</p><p>The purpose of this thesis is to bring a deeper understanding of how different factors affect the results of XRF-analysis. A large number of measurements have been made with the instruments Niton XLt 700 and Niton Xli 700. Results from measurements of lead, zinc and copper have been analysed.</p><p>This study has shown that a greater moisture content will give a lower measured concentration for the same sample. If the moisture content is known, it is possible to make good approximations of concentrations in dry samples. No obvious differences were found between different metals.</p><p>Proper homogenisation of samples was found to be one of the most critical issues. It should be noted that laboratories do not usually homogenise samples prior to analysis, so samples sent for laboratory verification should therefore be homogenised before sending.</p><p>Sample preparation, including drying, sieving to finer grain-sizes and analysing in a special sample cup was found to increase the measured concentrations and decrease the variation between measurements. The concentrations differed with different sample matrices and with sample preparation. Because of the differences, measurements should always be correlated with laboratory analysis before any conclusions can be made. In situations when metals are well within detection range of the XRF instrument, the only preparation needed is in most cases homogenisation. If metal levels are just at the limit, or just below the detection limit, further preparations of samples should be made. When drying samples makes detection possible, more preparation is usually not worth the effort. If detection limits still are a problem after drying, the samples should be sieved and analysed in sample cups. In situations where concentrations still are below the</p><p>detection limit when analysing in sample cups, or if the measurements are disturbed for other reasons, another method than XRF-analysis must be used. When XRF analysis is possible, the method is preferable compared to only laboratory analysis. This cost- and time effective method makes a larger number of measurements possible, and gives a more complete overview of a polluted area.</p> / <p>Analys med röntgenfluorescensdetektor (XRF) är en snabb och kostnadseffektiv fältmetod för detektion av tungmetaller i mark. Nackdelen är att mätningarna inte är tillförlitliga i alla sammanhang och att detektionsgränsen för många ämnen är förhållandevis hög. Det är sedan tidigare känt att olika former av provbearbetning påverkar mätresultaten.</p><p>I detta examensarbete har undersökts hur olika faktorer påverkar mätresultaten vid analys av jordprover med XRF instrument. Faktorerna som undersökts är inverkan av vattenkvot, kornstorlek, provpåsar och olika provbearbetningsmetoder. Vid provbearbetningsförsöken skickades prover även in till externt laboratorium för jämförande analys. Metaller som undersökts är bly, zink och koppar.</p><p>Vid undersökningen konstaterades att en ökad vattenkvot ger upphov till lägre mätvärden. Vid kännedom om vattenkvot kan halt per torrsubstans med god överensstämmelse uppskattas utifrån mätningar på fuktiga prov. Är precisionskraven stora och vattenkvoten varierande och okänd bör dock proverna torkas innan mätningar görs. Ingen avsevärd skillnad sågs mellan de olika metaller som undersöktes.</p><p>Vid undersökningen om provbearbetningens betydelse visade det sig att homogeniseringen av proverna är mycket viktig, inte minst av prover som skickas till laboratorieanalys.</p><p>Ökad provbearbetning med torkning och siktning till mindre kornstorlek tenderar att ge högre mätvärden med XRF instrument. Storleksmässigt är mätvärden vid obearbetade prov mest överensstämmande med laboratorieanalys. Mest skiljer sig analys på finsiktade prover i provkopp. Korrelationsmässigt finns i en del fall en tendens till bättre överensstämmelse med mer bearbetade prov. Den största vinsten med ökad bearbetning av prover konstaterades i detta arbete vara att mark med lägre metallkoncentrationer då kan analyseras.</p><p>I de fall där halterna av metaller ligger väl inom XRF instrumentets detektionsområde visade det sig att det oftast är tillräckligt att endast homogenisera proverna innan analys görs. I de fall där koncentrationen av metaller är på gränsen till vad XRF instrumentet kan detektera rekommenderas att proverna torkas, eller om nödvändigt torkas, siktas och analyseras i provkopp. Där nivåerna av metaller ligger under detektionsgränsen för XRF instrument trots provbearbetning, eller där andra ämnen till exempel järn stör mätningarna, måste en annan analysmetod väljas.</p>
67

Use and environmental impact of antifouling paints in the Baltic Sea

Bighiu, Maria Alexandra January 2017 (has links)
Biocide-based antifouling (AF) paints are the most common method for preventing biofouling, i.e. the growth of algae, barnacles and other organisms on boat hulls. AF paints for leisure boats are predominantly based on copper (Cu) as the main biocide, with zinc (Zn) present as a pigment and stabilizer. Both metals are released from the paint matrix into the water column, leading to contamination of marinas which typically have only limited water exchange. Thus, the aim of this PhD thesis was to describe the use of AF paints in different regions in Sweden, as well as the associated environmental consequences with regard to contamination of the environment and toxicity to non-target aquatic snails. Using a recently developed X-ray fluorescence application, high levels of Cu were detected on boats moored in freshwaters, despite a more than 20-year-old ban, as well as high levels of tin (Sn) on 10 % of the boats, indicating the presence of (old) tributyltin paints (TBT), which might pose an environmental risk and a health hazard for people performing the paint scraping (paper 1). In addition, very high levels of Cu and Zn were measured in the biofouling material collected from the boat hulls, and this is problematic because the biofouling is commonly disposed of on the soil in boatyards at the end of each season. No difference was found in the amount of biofouling on boats coated with Cu or biocide-free paints, which implies that Cu might be currently overused in areas of low salinity and low barnacle density (paper 2). This work also introduces the use of a new species for ecotoxicological field experiments, the snail Theodoxus fluviatilis. Chronic field experiments (paper 3) revealed 6-fold increases in snail mortality, negative growth and up to 67-fold decreased reproduction in marinas, compared to areas not impacted by boating (‘reference areas’). Moreover, a higher prevalence of snails with histopathological alterations (e.g. necrosis of gills, gonads, midgut gland and parasite infestation, among others) was observed in the marinas, compared to the reference areas (paper 4). Statistical modelling indicated that the majority of the toxic effects were best predicted by the metals, most likely originating from AF paints. The results presented in this thesis depict some important aspects of AF paint use in brackish water and highlight the necessity of implementing a suitable management practice for the heavily contaminated biofouling waste in order to minimize the risk to soils. In addition, the evidence of toxicity to snails in marinas can be used as a basis to increase the public understanding of the impact of recreational boating and encourage people to choose less toxic alternatives to AF paints. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>
68

Evaluation of Total Fume and Heavy Metal Emission Factors Applicable to Gas Metal Arc Welding

Jilla, Abhinay 23 May 2019 (has links)
Welding is a metal joining process widely used in many manufacturing facilities around the world. It involves the process of heating the base and filler metals to a high temperature that leads to the formation of fumes. Welding emissions consist of gaseous pollutants and micron and sub-micron particles consisting of different heavy metals. Health risks associated with exposures to weld fume is well recognized in the literature. This research evaluates emissions and emission factors applicable to gas metal arc welding (GMAW) on AH 36 (mild steel) and 316 L (stainless steel). Emission factors evaluated consisted, total fume, chromium, cobalt, lead, manganese, and nickel. A weld fume chamber is used to capture the welding fumes onto a filter and then further analyzed to quantify the total fume and heavy metal emissions. Critical operating parameters such as current, voltage, shielding gas, welding speed, and contact tube to work distance (CTWD) were considered while evaluating emissions and emission factors. The parameters with greater influence on emissions are selected, and then the heavy metal emissions are quantified by varying those parameters using inductively coupled plasma atomic emission spectrometry (ICP-AES) and portable XRF (X-Ray Fluorescence) analyzer. The heavy metal results from the ICP-AES and XRF are compared to explore the feasibility of using XRF analyzer in quantifying the heavy metals in welding fumes. Using the heavy metal emissions, the lifetime carcinogenic and non-carcinogenic risks are evaluated for the GMAW process. The mild steel (MS) and stainless steel (SS) statistical analysis results indicate current and voltage are most influencing parameters in generating the fumes in GMAW. This research found a significant linear relationship between ICP-AES and XRF heavy metal results. The lifetime carcinogenic and non-carcinogenic risks results indicate high potential health risks if not properly managed.
69

XRF-analys av förorenad mark : undersökning av felkällor och lämplig provbearbetning / XRF-analysis of contaminated soil : a study of error sources and suitable sample preparation

Kjellin, Johan January 2004 (has links)
X-ray fluorescence (XRF) detection of heavy metals is a cost- and time-effective method for investigation of polluted areas. Compared to laboratory analysis, XRF analysis is limited by high detection limits and uncertainties in some situations. Preparation of samples is known to affect the results of measurements. The purpose of this thesis is to bring a deeper understanding of how different factors affect the results of XRF-analysis. A large number of measurements have been made with the instruments Niton XLt 700 and Niton Xli 700. Results from measurements of lead, zinc and copper have been analysed. This study has shown that a greater moisture content will give a lower measured concentration for the same sample. If the moisture content is known, it is possible to make good approximations of concentrations in dry samples. No obvious differences were found between different metals. Proper homogenisation of samples was found to be one of the most critical issues. It should be noted that laboratories do not usually homogenise samples prior to analysis, so samples sent for laboratory verification should therefore be homogenised before sending. Sample preparation, including drying, sieving to finer grain-sizes and analysing in a special sample cup was found to increase the measured concentrations and decrease the variation between measurements. The concentrations differed with different sample matrices and with sample preparation. Because of the differences, measurements should always be correlated with laboratory analysis before any conclusions can be made. In situations when metals are well within detection range of the XRF instrument, the only preparation needed is in most cases homogenisation. If metal levels are just at the limit, or just below the detection limit, further preparations of samples should be made. When drying samples makes detection possible, more preparation is usually not worth the effort. If detection limits still are a problem after drying, the samples should be sieved and analysed in sample cups. In situations where concentrations still are below the detection limit when analysing in sample cups, or if the measurements are disturbed for other reasons, another method than XRF-analysis must be used. When XRF analysis is possible, the method is preferable compared to only laboratory analysis. This cost- and time effective method makes a larger number of measurements possible, and gives a more complete overview of a polluted area. / Analys med röntgenfluorescensdetektor (XRF) är en snabb och kostnadseffektiv fältmetod för detektion av tungmetaller i mark. Nackdelen är att mätningarna inte är tillförlitliga i alla sammanhang och att detektionsgränsen för många ämnen är förhållandevis hög. Det är sedan tidigare känt att olika former av provbearbetning påverkar mätresultaten. I detta examensarbete har undersökts hur olika faktorer påverkar mätresultaten vid analys av jordprover med XRF instrument. Faktorerna som undersökts är inverkan av vattenkvot, kornstorlek, provpåsar och olika provbearbetningsmetoder. Vid provbearbetningsförsöken skickades prover även in till externt laboratorium för jämförande analys. Metaller som undersökts är bly, zink och koppar. Vid undersökningen konstaterades att en ökad vattenkvot ger upphov till lägre mätvärden. Vid kännedom om vattenkvot kan halt per torrsubstans med god överensstämmelse uppskattas utifrån mätningar på fuktiga prov. Är precisionskraven stora och vattenkvoten varierande och okänd bör dock proverna torkas innan mätningar görs. Ingen avsevärd skillnad sågs mellan de olika metaller som undersöktes. Vid undersökningen om provbearbetningens betydelse visade det sig att homogeniseringen av proverna är mycket viktig, inte minst av prover som skickas till laboratorieanalys. Ökad provbearbetning med torkning och siktning till mindre kornstorlek tenderar att ge högre mätvärden med XRF instrument. Storleksmässigt är mätvärden vid obearbetade prov mest överensstämmande med laboratorieanalys. Mest skiljer sig analys på finsiktade prover i provkopp. Korrelationsmässigt finns i en del fall en tendens till bättre överensstämmelse med mer bearbetade prov. Den största vinsten med ökad bearbetning av prover konstaterades i detta arbete vara att mark med lägre metallkoncentrationer då kan analyseras. I de fall där halterna av metaller ligger väl inom XRF instrumentets detektionsområde visade det sig att det oftast är tillräckligt att endast homogenisera proverna innan analys görs. I de fall där koncentrationen av metaller är på gränsen till vad XRF instrumentet kan detektera rekommenderas att proverna torkas, eller om nödvändigt torkas, siktas och analyseras i provkopp. Där nivåerna av metaller ligger under detektionsgränsen för XRF instrument trots provbearbetning, eller där andra ämnen till exempel järn stör mätningarna, måste en annan analysmetod väljas.
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Fast screening of metal contaminated soil using a x-ray fluorescence method

Zeng, Guo-wei 29 June 2010 (has links)
The purpose of this research is to develop a rapid determination method for heavy metals in soil. Using X-ray fluorescence to obtain soil metals decision limit (CC£\) and detection capability (CC£]), to establish the scope of soil metal concentration selection. Then aqua regia digestion digestion and ICP-OES analysis of Pb, Cd, Zn, Ni, Cr, Cu area to check the accuracy of screening. Operating conditions; First, the soil standard samples for the Establishment and assessment of the applicability of the standard. Finally,using of the soil near the control standard establish methods and explore ways to establish the applicability and potential impact. I hope this research can provide a fast, accurate, and sensitivity of soil heavy metal screening, to achieve savings of cost. The results show that the standard reference soil Cu: screening rate was 79.7%, sensitivity was 43.6% and an specificity of 87.7%; reference standard soil Pb: screening rate was 91.5%, a sensitivity of 8.3% specificity 91.5%;reference standard soil Cr:screening rate was 100%, sensitivity was 0%, 100% specificity; reference standard soil Ni: screening rate was 96.1%, sensitivity was 0%, specificity 92.4%; reference standard soil Zn: screening rate was 82.4%, sensitivity was 69.2%, specificity 87.1%; reaching control values of soil Cu: screening rate was 83.0%, sensitivity was 30.8%, specificity of 84.3%. Screening rate and specificity with 80%, the sensitivity poor areas, water was the major disturbance factor.

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