Dissertations / Theses on the topic 'Trace elements'
To see the other types of publications on this topic, follow the link: Trace elements.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Trace elements.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Bárány, Ebba. "Trace elements in adolescents /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2002. http://epsilon.slu.se/v117.pdf.
Full text
2
Corrigan, F. M. "Trace elements and psychiatric illness." Thesis, University of Aberdeen, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.592272.
Full textAbstract:
Developments in analytical techniques have allowed study of the concentrations of more than thirty elements in biological tissues. These methods have been applied to blood and brain tissues from patients with a wide range of psychiatric illness. Increases in blood vanadium concentrations in affective illness are discussed in relation to possible disturbance of noradrenaline metabolism. It is suggested that high vanadium levels may reflect high circulatory levels of noradrenaline but direct evidence of such a link has not yet been obtained. Discussions of elements in dementia centres mainly on aluminium and zinc: the possibility of low zinc concentrations being relevant becomes more likely as evidence accumulates for the role of zinc in hippocampal function. Glutamatergic transmission is likely to be crucial in this context and evidence is presented for an association between glutamate and the rare earth elements cerium and lanthanum in caudate nucleus of schizophrenics. Whether these will prove to have a fucntional role in hippocampus remains to be seen, but possible implications for modulation of striatal dopaminergic function, via glutamatergic corticostriatal tracts, are discussed. Reduction of caesium may be important through altered GABAergic transmission and reduction of indium may reflect changes in dopaminergic neuronal activity. It is considered that this work on human tissue is giving indications of which elements need to be studied in laboratory experiments to elucidate their role in neuronal transmission and, therefore, in psychiatric illness.
3
Stovell, Alex Gordon. "Trace elements and human fertility." Thesis, University of Surrey, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301350.
Full text
4
Погорєлов, Максим Володимирович, Максим Владимирович Погорелов, Maksym Volodymyrovych Pohorielov, E. V. Gusak, V. N. Deyneka, and E. N. Gordienko. "Trace elements in healthy bones." Thesis, Видавництво СумДУ, 2012. http://essuir.sumdu.edu.ua/handle/123456789/27504.
Full textAbstract:
Osteogenesis stimulation is one of the underinvestigated issues nowadays, as well as the topical problem of traumatology. One of the most important functions of the osseous tissue is depositing of macro- and microelements, due to this research on the skeleton ion profile is highly important to explain the osteogenesis physiological and reparative processes. As some microelements are involved into enzyme catalysis reactions, which are held in the osteogenic cells, so in case of their deficit or imbalance some processes are interrupted such as osteoblastic and osteoclastic differentiation, apatite crystallization process, cell-cell collaboration. These all cause physiological and reparative remodeling changes of bone.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/27504
5
Okada, Naoki. "TRACE ELEMENTS IN TREE STEMS." Kyoto University, 1990. http://hdl.handle.net/2433/78225.
Full text
6
Voigt, Astrid. "Bioavailability of trace metals to plants." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19561.
Full textAbstract:
Soil quality guidelines are currently based on total trace metal loads. There is a need to define indices of bioavailability to allow reasonable predictions for plant metal uptake and toxicity in soils. Trace metal toxicities to plants often correlate best with free metal ion activities. The first objective was to develop a plant bioassay that is sensitive to trace metals at concentrations realistic for soils. The root elongation of lettuce Lactuca sativa 'Buttercrunch' was used as toxicological endpoint. This endpoint was sensitive and reproducible to environmentally relevant concentrations of Cd, Cu, Ni, Pb and Zn. The second objective was to test whether free metal ion activities are constant predictors of metal toxicities in synthetic solutions and in soil extracts that differ in their concentrations of cations and ligands. The root elongation assay was used to test this hypothesis. In synthetic solutions, the rhizotoxicity of Cd, Cu, Ni, Pb and Zn decreased with increasing Ca and H concentrations. This could not be explained with the effect of higher cationic concentrations on root growth or on solution speciation. It was concluded that Ca and H inhibited the rhizotoxicity of all metals tested. The rhizotoxicity of Cu and Cd was further examined in soil extracts. Both metals became less rhizotoxic at higher H and dissolved organic matter concentrations. The rhizotoxicity endpoints from the experiments in synthetic solution were used to develop parameters for a Biotic Ligand Model (BLM) for Cd, Cu, Ni, Pb and Zn. The BLM accounts for solution speciation and interprets cationic inhibition of rhizotoxicity as competition of metals with Ca and H for potential sites of rhizotoxicity. The BLM predicted metal rhizotoxicity better than the free metal ion activity in synthetic solutions and in soil extracts. Different models were tested against literature rhizotoxicity data for metals at different Ca and H concentrations. Predictions for metal rhizotoxicity given by BLM, Gouy-Chapman-Stern model and Freundlich equation model were compared with predictions based on free metal ion activities in solution. The BLM predicted rhizotoxicity most accurately. The BLM seems promising for predictions of metal toxicity and metal bioavailability in soils to support site-specific environmental risk assessments.
7
Reed, Graham Philip. "Control of trace elements and gasification." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313361.
Full text
8
Dundar, Mustafa Sahin. "Speciation studies on dietary trace elements." Thesis, University of Hull, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337335.
Full text
9
Reyes, Delgadillo Dulce B. "Modeling natural attenuation of trace elements in soils." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101169.
Full textAbstract:
Trace elements added to the soil by human activities could contaminate it and occasionally cause a threat to environmental and human health. The toxicity and mobility of a trace element are affected by the element's solubility, which in turn is influenced by the soil properties. When mobile, trace elements can be leached out of the soil. If leaching occurs at a faster rate than atmospheric deposition, element concentrations in the soil will decrease by natural attenuation.We analyzed soil properties in 40 soils and their soil solutions to obtain a set of equations with the most significant predictors of As, Cd, Co, Cu, Mo, Ni, Pb and Zn in solution. The total element concentration and the pH were the best predicting variables of the amount of element in solution for all trace elements analyzed, while organic carbon and Al or Mn oxides also influenced the solubility of some trace elements. Using the equations predicting elemental solubility, we wrote a model for natural attenuation in the computer program Stella that considers atmospheric deposition as the input for trace elements and leaching as the output. Simulations were carried out for the 40 soils during 1,000 years with steady deposition inputs.
At current atmospheric deposition rates and the neutral to alkaline pH of these soils, attenuation occurred in most soils for Mo. For As, Cd, Co, Cu and Ni it occurred only in soils with abundant total element concentrations or an acidic pH. Minor retention occurred with Pb and Zn. Only Cd and Cu were of concern in leaching waters. The developed model can serve as a decision making tool in the selection of natural attenuation as a remediation strategy.
10
Dick, A. L. "Trace elements in Antarctic snow and air." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376538.
Full text
11
Al-Merey, Rafaat. "Trace elements determination in Syrian phosphate rocks." Thesis, University of Reading, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329358.
Full text
12
Santos, Susana Isabel Barros dos. "Trace elements quantification in Portuguese red wines." Master's thesis, Faculdade de Ciências e Tecnologia, 2011. http://hdl.handle.net/10362/6276.
Full textAbstract:
Dissertation for the Degree of Master in
Technology and Food Safety – Food QualityThe aim of this thesis is to characterize Portuguese red wines in terms of trace elements composition. The wines were chosen so that all the country was represented and studied. For trace elements quantification (As, Hg, Cd, Ni and Pb) were tested various sample treatments including for all trace elements: acid digestion or presence and absence of spike. The need for H2O2 addition in order to oxidize organic compounds was analyzed for Hg, Cd, Ni and Pb. Quantification of all trace elements was performed with Atomic Absorption Spectrometry techniques. After the method validation were analyzed 25 Portuguese red wines and duplicates. The concentrations obtained were used to perform a statistical analysis to determine what were the regions with highest incidence of each trace element. Using Target Hazard Quotient (THQ) equation was possible to identify the regions where the concentrations found are a reason for public health concern, being values above 1 a motive for concern. After the analysis was determined that there is no need for wine samples digestion and that the presence of H2O2 is crucial. Hg and As were quantified with Hydride Generation Atomic Absorption Spectrometry; Ni and Pb with Flame Atomic Absorption Spectrometry; Cd with Electrothermal Atomic Absorption Spectrometry. The statistical results allowed to conclude that the system variation was mainly explained by the variation of Ni, As and Hg concentrations. Ni was largely found in Estremadura and Terras do Sado wines, while As and Hg were found mostly in Minho and Douro wines respectively. All of THQs determined were under 1, which is the limit value above which there is reason for health concern. Maximum THQ values were of 0.044 in Algarve wines were due to Ni.
13
Norris, C. Ashley. "Volatilities of trace elements in silicate melts." Thesis, University of Oxford, 2016. http://ora.ox.ac.uk/objects/uuid:2ae4f65b-951b-42d3-9b71-6d91c7b6d207.
Full textAbstract:
The loss rates of volatile elements from silicate melts are of considerable interest to a number of branches of volcanology, petrology, and geochemistry. In the volcanic context emanation coefficients are used as empirical measures of the extent of loss of individual elements in the gas phase. In geochemistry and cosmochemistry relative loss rates control the pattern of element depletions during melting and core segregation on asteroids and proto planets. Incorporation of such differentiated, pre-melted bodies probably influenced the well-known pattern of volatile element depletion in the Silicate Earth. This study makes two independent measurements of the volatilities of the elements Ag, Bi, Cd, Cr, Cu, Ga, Ge, In, Mo, Pb, Sn, Tl, V, W and Zn, in molten silicate. The first includes a series of high pressure (1.5GPa) metal-silicate partitioning experiments used to determine the activities of trace elements in silicate melts. The second involves direct measurement of volatile loss from a representative basaltic melt at oxygen fugacities applicable to planetary formation. Results from this study show that some elements (e.g. indium) are less volatile than previously thought, while others (e.g. copper) are more so. Applying these results to volatile depletion in the Silicate Earth reconciles the supposed overabundance of indium, as suggested by condensation temperatures. Comparing depletion of the Silicate Earth relative to CI meteorites shows a remarkably consistent trend with the measured volatility factors, suggesting that evaporative volatile loss occurred during planetary formation, most likely from planetesimals. The volatile loss data from this study also support the observation of volatile depletion in lunar basalts. Such agreement provides additional evidence that the Moon experienced some degree of volatile loss during its accretion after the giant impact by Theia.
14
Fontanili, L. "SYSTEMIC ALLOCATION OF TRACE ELEMENTS IN RICE." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/253624.
Full textAbstract:
Several studies have shown that Cd, a non-essential and toxic metal, is taken up from soil and translocated in a root-to-shoot direction through transporters of essential elements such as Zn, suggesting that the two metal ions may compete for the same transporter protein on a membrane. However, the movement of Zn and Cd ions across several biological membranes involves a wide range of transport systems, each characterized by a specific selectivity. Although divergent results have been obtained, they suggest that Zn-independent pathways for Cd translocation in plants could be possible.
The proteins belonging to the HMA (Heavy-Metal ATPases) family have been partially characterized as the main actors of the process of translocation of trace elements (essential or non-essential) to all organs of the plant. In particular, OsHMA2 is the main transport system so far described in rice as involved in the xylem loading of Zn and Cd, even though both its activity and function has not been unambiguously characterized.
The research carried out in this PhD project took place in this context. Indeed, the general purpose was studying the main mechanisms involved in the systemic distribution of some trace elements in rice plants. In particular the activity was aimed at better understanding the Zn and Cd translocation pathways, and was focused on studying the possible competition between the two metal ions mainly for the root-to-shoot translocation, since these processes have been seen to be crucial in determining Cd accumulation in the shoots. Specifically, the aims of this study were: (i) to investigate the effects of the possible competition between Zn and Cd on their chelation and subcellular compartmentalization at the root level, thus in reducing the amount of the two metals potentially mobile through the plant. This was done using physiological techniques aimed at isolating and quantifying thiol based Zn- and/or Cd-binding complexes; (ii) to investigate the potential inhibitory effect exerted by Zn on Cd translocation in unstressed rice plants, performing a short-term positron-emitting tracer imaging system (PETIS) experiment using 107Cd as tracer; (iii) to identify genes encoding transporters involved in a putative Zn-insensitive Cd xylem loading, thus responsible for a possible Zn-independent Cd translocation pathway, by performing bioinformatic analysis. Our attention focused on the P1B-type ATPase (HMA) family in order to search for orthologs of the genes codifying the transporters that in the model plant Arabidopsis were found to mediate the xylem loading of Cd; (iv) to functional characterize the transporters encoded by the abovementioned genes by heterologous expression in Saccharomyces cerevisiae.
A complete set of competition experiments were performed: in the first, rice plants (O. sativa L. ssp. japonica cv. Roma) were hydroponically grown and differentially exposed for a 10-day period to increasing Zn external concentrations, in the absence or presence of a steady amount of Cd, whilst, in the second, plants were exposed for 10 days to different Cd concentrations in the presence of a steady amount of Zn. The concentrations of Zn and Cd in xylem sap, roots and shoots were evaluated by inductively coupled plasma-mass spectrometry (ICP-MS), to determine their partitioning between plant organs. The results were related to the total Zn and Cd content in root fractions obtained by a sequential extraction procedure with buffer and acid. The procedure allowed to discriminate Zn and Cd ions potentially mobile (cationic) from those retained in complexes with thiol-peptides or other soluble molecules negatively charged in the extraction buffer (anionic), or tightly adsorbed to cellular matrices or apoplast components (acid soluble and ash); so, the last three fractions should be considered not available for root-to-shoot translocation. Moreover, the systemic movement of Cd in the whole rice plants was monitored by applying to the roots fresh marked (107Cd) culture solutions containing a steady amount of Cd and different concentrations of Zn in PETIS experiments.
The main results clearly indicate the lack of a fully reciprocity considering the effect of Cd on Zn accumulation, and vice versa, since the accumulation of Zn in the shoot was significantly inhibited by Cd increases in all the analyzed conditions, whereas those of Cd was only partially impaired by Zn increases. Such a finding suggests that Cd ions may use at least two distinct pathways to be translocated from the root to the shoot. The first one – shared with Zn – is probably used for Zn translocation in physiological conditions, whilst the second one appears as a Zn-independent route that Cd may preferentially use when the first pathway is saturated with Zn. Moreover, the Zn-independent pathway seems constitutively expressed in rice plants since the partial inhibitory effect exerted by Zn on Cd translocation was also observed in short-term PETIS experiments performed with unstressed plants. Since OsHMA2 appears to play an important role in Zn/Cd root-to-shoot translocation, in this work we also contributed to elucidate some aspects related to the OsHMA2 transport activity and selectivity by comparing the inhibitory effects exerted by Zn or Cd on the growth of yeast cells expressing, or not, OsHMA2. The results indicate that OsHMA2 enhances Zn and Cd tolerance in yeast, so we can reasonably conclude that OsHMA2 may pump excess of cytosolic Zn or Cd into the apoplast and thus has all the requisites to be considered the xylem loading system potentially involved in mediating the translocation of Cd through the Zn-dependent pathway. In addition, this study represents one of the first examples of growth inhibition analysis applied to plant gene functional characterization.
In conclusion, our data provide several evidence to support the hypothesis that at least two competing pathways may be interested in mediating root-to-shoot Cd translocation in rice. The first one, prevailing at relatively low Zn concentrations, could involve OsHMA2 as Zn2+/Cd2+ xylem loading system, while the second one appears to involve a Zn-independent system that still needs to be identified among the plethora of transporters involved in the metal homeostasis. The possible future identification of the transporter(s) responsible for the Zn-independent Cd translocation pathway(s) could allow the development of markers to select rice genotypes able to exclude Cd from the shoots. Furthermore, these activities could have important technological implications in the fields of food safety, especially in cases where the strategies used for containing Cd accumulation in the crops be founded on Zn fertilization.
15
Trapp, John Michael. "Chemistry of Iron and Other Trace Elements in Trade Wind Aerosols and Precipitation." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/323.
Full textAbstract:
The atmospheric transport of various substances from the continents to the oceans plays an important role in biogeochemical processes. Trace metals, iron in particular is of great interest as its availability regulates the growth of phytoplankton over large areas of the ocean. This dissertation focuses on examining and characterizing the factors that affect the solubility of trace metals in Miami and Barbados aerosols and precipitation, in particular species that could play a role in surface seawater biogeochemistry (Fe and trace metals such as Al, V, Cr, Mn, Cu, Co, Ni, Zn, As, Tl, Ba, Cd, Pb, Th, Ti, Zr, and REE's). To enable this study existing methods of colorimetric spectroscopic and inductively coupled plasma mass spectrometry analysis were improved and modified. This dissertation examines several issues related to source inputs: 1.) Are single spot sources within the North African dust source distinguishable after long transport by their bulk metal composition and thus important in the characteristics of individual mineral dust samples? 2.) What is the temporal variability and controlling factors in trace metal solubility in trade wind aerosols collected over Barbados? 3.) Which factors control the observed trend of speciation and increasing iron solubility in decreasing aerosol loading? Additionally a kinetic model of species specific iron (II) to iron(III) oxidation kinetics in NaCl Brines was conducted at nano-molar levels. This study greatly expands the ability to predict rates of iron oxidation at concentrations closer to those observed in natural systems.
16
Gurusamy, K. S. "Role of trace elements in colorectal liver metastases." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1302062/.
Full textAbstract:
Trace elements are involved in many key metabolic pathways. Literature review demonstrated that the trace element content in liver metastases is lower than that in surrounding livers and that in livers of normal individuals. The significance of trace elements in the diagnosis, prognosis, and treatment of patients undergoing surgical resection for colorectal liver metastases (CLM) is not known. Samples obtained from patients who underwent liver resection for colorectal liver metastases were used for this research. Iron, copper and zinc content were measured by X-ray fluorescence (XRF) and were confirmed to be lower in colorectal liver metastases than normal liver. Measuring zinc levels in the tissues could differentiate CLM and normal liver with a sensitivity and specificity of 100% and 93.1% respectively. There was a positive correlation between zinc content but not copper content and microvessel density (MVD), a surrogate marker of angiogenesis. However, tumour copper content was found to be a very good predictive factor of survival in patients undergoing liver resection for CLM (area under receiver operating characteristics curve - AUROC 0.919). Micro-XRF revealed that the zinc was preferentially found in normal liver cells (hepatocytes) followed by tumour cells and found least in fibrous stroma. ZnT1, the main zinc efflux transporter, was downregulated in CLM compared with normal liver (5.2 fold, P = 0.002 respectively). Tissue culture experiments using the cell line HT-29 demonstrated no correlation between zinc in culture medium and the main zinc transporters (ZnT1 and ZIP1). However, zinc chelation inhibited genetic markers of apoptosis and angiogenesis and was lethal to the HT-29 cell line. Zinc did not have any effect on cell viability but had a protective effect against short periods of zinc chelation. This thesis has demonstrated unique and biologically important relationships between zinc levels and colorectal metastases which require further biochemical and genetic investigation.
17
Sham, R. P. "The role of selected trace elements in atherosclerosis." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47251.
Full text
18
Pallavicini, Nicola. "Method development for isotope analysis of trace and ultra-trace elements in environmental matrices." Doctoral thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-59705.
Full textAbstract:
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>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>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.
19
Poon, Tim-leung. "Trace organic pollution in the indoor environment /." [Hong Kong : University of Hong Kong], 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13498605.
Full text
20
Ambrose, Andrea Jane. "A preconcentration technique for the determination of trace elements." Thesis, University of Plymouth, 1989. http://hdl.handle.net/10026.1/1662.
Full text
21
Corgne, Alexandre. "Deep earth structure and the distribution of trace elements." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399373.
Full text
22
Zeng, Taofang 1963. "Transformation of iron and trace elements during coal combustion." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9971.
Full text
23
Hassani, Bibizahra 1959. "Binding of trace elements with various dietary fiber sources." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277058.
Full textAbstract:
Mineral binding capacity of rice bran, oat hull, soy bran, wheat bran, peanut, apple, tomato, and barley fiber were investigated. Defatted fibers were analyzed for ash, protein, acid detergent fiber, and lignin. The fibers were washed with 1% HCl and Acid washed samples were studied for their mineral binding ability. The minerals tested were zinc, copper, and magnesium. Analysis of acid washed samples showed that most of the original minerals had been stripped from the fiber. In most of the fibers studied, the order of binding was copper > zinc > magnesium. Among the eight fibers studied, oat hull and apple fiber had the lowest consistent binding capacity for the three minerals investigated. This in vitro binding study has been run to duplicate intestinal condition of pH 6.8.
24
Elliott, Tracey Anne. "Bone diagenesis : an experimental study of selected trace elements." Thesis, Durham University, 1993. http://etheses.dur.ac.uk/1556/.
Full text
25
Sabino, Magali. "Bioaccumulation of trace elements in Seychelles marine food webs." Thesis, La Rochelle, 2021. http://www.theses.fr/2021LAROS026.
Full textAbstract:
La sécurité alimentaire, qui est la garantie de l’approvisionnement et de la qualité des aliments tout en gérant les ressources de manière durable, est intrinsèquement liée à la connaissance de la biologie et l’écologie des espèces consommées. Dans un contexte de dérèglement climatique menaçant la salubrité des produits de la mer, il est donc nécessaire d’établir un référentiel sur le fonctionnement des systèmes marins, ainsi que sur l’occurrence des nutriments et des contaminants dans les produits de la mer. C’est d’autant plus important pour les Petits Etats Insulaires en Développement (PEID), qui dépendent des ressources marines pour leur subsistance, et où les produits de la pêche sont la première source de protéines et micronutriments (éléments traces essentiels) pour les populations locales. Malgré l’importance des systèmes tropicaux pour la sécurité alimentaire, ces systèmes sont peu étudiés comparés aux systèmes polaires et tempérés. Cette thèse vise à mieux comprendre le fonctionnement des systèmes marins tropicaux, et à établir un référentiel sur l’occurrence des micronutriments et des contaminants métalliques dans les produits de la pêche aux Seychelles (Océan Indien), un PEID tropical. En étudiant les concentrations en éléments traces aux niveaux inter- et intraspécifique, nous avons identifié différents facteurs intrinsèques et extrinsèques influençant la bioaccumulation de ces éléments dans les ressources marines tropicales. Nous avons aussi montré l’importance de considérer différentes échelles (individu, espèce et écosystème) pour mieux comprendre l’occurrence des éléments traces essentiels et non-essentiels dans les produits de la merFood security, that is guarantying food supply and quality while sustainably managing resources, is closely linked to knowing the biology and ecology of consumed species. In a context of global changes that are threatening seafood safety, it is thus necessary to establish baselines on marine ecosystem functioning, as well as nutrient availability and contamination occurrence in seafood. This is all the more important in Small Island Developing States (SIDS), where populations rely on marine resources for their subsistence, and where capture fisheries resources are the main sources of proteins and micronutrients (i.e. essential trace elements) in local populations’ diet. In spite of the importance of tropical systems in ensuring food security, they remain largely understudied compared to polar and temperate systems. This thesis thus aims to better understand the functioning of tropical marine systems, and to establish a baseline on micronutrient availability and metal(loid) contamination in a wide diversity of capture fisheries resources from the Seychelles (Western Indian Ocean), a tropical SIDS. By investigating trace element concentration patterns at the inter- and intraspecific levels, it was possible to identify intrinsic and extrinsic factors influencing trace element bioaccumulation in tropical capture fisheries resources. We thus highlighted the importance of considering different scales (individual, species, and ecosystem) to better understand essential trace element availability and non-essential trace element occurrence in seafood
26
Seames, Wayne Stewart. "The partitioning of trace elements during pulverized coal combustion." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/284196.
Full textAbstract:
The environmental impact resulting from the release of trace elements during coal combustion is an important issue for the coal-fired electric utility industry. Trace elements exit the combustor by partitioning between the flue gas and the fly ash particles. A comprehensive study has been conducted to investigate the mechanisms governing the partitioning of trace elements during pulverized coal combustion. The behavior of seven trace elements (arsenic, selenium, antimony, cobalt, cesium, thorium, and cerium) in six pulverized coals were studied under commercially relevant conditions in a well-described laboratory combustion environment. The partitioning of trace elements is governed by the extent of volatilization during combustion, the form of occurrence in the flue gas, and the mechanisms controlling vapor-to-solid phase transformation to fly ash particle surfaces. The most common vapor-to-solid phase partitioning mechanism for semi-volatile trace elements is reaction with active fly ash surfaces. Trace elements that form oxy-anions upon volatilization (e.g. arsenic, selenium, antimony) will react with active calcium and iron cation fly ash surface sites. Trace elements that form simple oxides upon volatilization (e.g. cobalt, cesium) will react with active aluminum oxy-anion fly ash surface sites. The maximum combustion temperature affects the availability of active calcium and iron surface sites but not aluminum sites. Sulfur inhibits the reactivity of oxy-anions with iron surface sites. For coals with high sulfur contents (>1 wt % as SO₂), volatilized trace elements that form oxy-anions will partition by reaction with calcium surface sites if sufficient sites are available. For coals with low sulfur contents, volatilized trace elements that form oxy-anions, will partition by reaction with iron surface sites. Volatilized trace elements that form oxy-anions will not partition by reaction if the coal sulfur content is high and the calcium content is low (<3 wt% as CaO). Transition metals (e.g. cobalt) may form simple oxides, oxy-anions or both upon volatilization. An appreciable fraction of trace elements with limited volatility (e.g. cobalt, thorium, cerium, cesium) will volatilize. These will partition back to the solid phase by homogeneous nucleation or surface reaction depending upon the post-combustion conditions present.
27
Hultén, Amanda. "Determination of trace elements in thrombocytes by ICP-MS." Thesis, Uppsala universitet, Institutionen för kemi - BMC, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-397392.
Full text
28
Eriksson, Emma. "Determination of trace elements in thrombocytes by ICP-AES." Thesis, Uppsala universitet, Institutionen för kemi - BMC, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-398044.
Full text
29
BARRESI, ANDREA. "Development of innovative techniques for ultra-trace elements analysis." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2023. https://hdl.handle.net/10281/403458.
Full textAbstract:
L'esperimento JUNO è stato proposto con l'obiettivo principale di risolvere il problema relativo all'ordinamento di massa dei neutrini attraverso misure accurate del flusso di antineutrini prodotto da reattori nucleari. A causa della sezione estremamente ridotta dei neutrini, il numero di eventi segnale previsti è molto piccolo, circa 60 eventi IBD al giorno, ed è quindi essenziale tenere sotto controllo il tasso di eventi di fondo. Ciò può essere ottenuto minimizzando tutte le sorgenti che contribuiscono alla produzione di eventi spuri e in primo luogo quelle generate dal fondo radioattivo. Per ogni capostipite delle catene naturali (U238 e Th232), per il 40K, e per alcuni nuclidi chiave, come 60Co e 210Pb, è necessario imporre forti limiti alla concentrazione che può essere presente all'interno dei materiali del rivelatore. Data la struttura del rivelatore JUNO, il materiale più critico è il liquido scintillante per il quale sono richieste concentrazioni di uranio e torio inferiori a 1E-15 g/g e potassio inferiori a 1E-16 g/g. In questa tesi, presento il lavoro che ho svolto in questo contesto con due scopi principali. Il primo è la validazione del software Monte Carlo dell'esperimento JUNO applicato alle simulazioni di fondo con l'obiettivo di verificare i limiti di radiopurezza imposti per i materiali e determinare il background-budget dell'esperimento. La seconda è l'implementazione di una tecnica di misura che permette di raggiungere le sensibilità richieste per la misura del contenuto di uranio, torio e potassio nel liquido scintillante. La validazione del software Monte Carlo dell'esperimento JUNO (SNiPER) è stata effettuata confrontandone i risultati con quelli di altri due codici di simulazione, in particolare con il software Arby, sviluppato presso l'Università degli studi di Milano-Bicocca. Ho potuto studiare diversi aspetti e molte criticità della simulazione del fondo e dei risultati riportati dallo strumento ufficiale, come l'applicazione del quenching factor e la forma degli spettri beta. Gli spettri dell'energia depositata prodotta dalle contaminazioni nei componenti principali del rivelatore JUNO sono stati calcolati con i codici Monte Carlo. Il tasso di eventi indotti nel rivelatore è stato valutato in base ai limiti di radiopurezza imposti, ottenendo il rate totale di eventi di fondo previsto. Il valore ottenuto è inferiore al limite imposto per garantire la sensibilità finale dell'esperimento. Ciò ha consentito di correggere e validare la risposta del software ufficiale dell'esperimento JUNO e di verificare l'attualità dei limiti di radiopurezza inizialmente definiti per i componenti del rivelatore. Durante il mio dottorato di ricerca ho completato lo sviluppo del nuovo sistema di misura, chiamato GeSparK che sfrutta la coincidenza tra uno scintillatore liquido e un rivelatore HPGe per ridurre il fondo del rivelatore HPGe singolo. È stata anche sviluppata una nuova tecnica di coincidenza ritardata che sfrutta la struttura nucleare del 239Np, il prodotto di attivazione del 238U, al fine di ottenere un marcatore estremamente forte di questo particolare decadimento e aumentare significativamente la sensibilità di misura rispetto all'approccio tradizionale. La sensibilità ottenuta era ancora insufficiente rispetto alle richieste di JUNO e per questo si decise di attuare una serie di trattamenti radiochimici. Diversi trattamenti sono stati proposti, testati e implementati con i due obiettivi di aumentare la massa del campione misurabile e ridurre la concentrazione di nuclidi interferenti. La tecnica sviluppata per uranio e torio prevede una fase di estrazione liquido-liquido e di estrazione cromatografia con resine UTEVA e TEVA rispettivamente prima e dopo l’irraggiamento. Due misurazioni condotte su campioni "bianchi" con la procedura finale hanno permesso di ottenere una sensibilità compatibile con i limiti imposti da JUNO per lo scintillatore liquido a livello del ppq.The JUNO experiment was proposed with the main aim of solving the problem related to the neutrino mass ordering through accurate measurements of the antineutrinos flow produced by nuclear reactors. Due to the extremely small cross-section of neutrinos, the number of expected signal events is very small, about 60 IBD events per day, and it is therefore essential to keep under control the rate of background events. This can be achieved by minimizing all the sources that contribute to the generation of spurious events and in the first place those generated by the radioactive background. For each progenitor of the natural chains (U238 and Th232), for the 40K, and for some key nuclides, such as 60Co and 210Pb, it is necessary to impose strong limits on the concentration that may be present within the materials of the detector. Given the structure of the JUNO detector, the most critical material is the liquid scintillator for which uranium and thorium concentrations below 1E-15 g/g and potassium below 1E-16 g/g are required. In this thesis, I present the work I did in this context with two main purposes. The first one is the validation of the Monte Carlo software of the JUNO experiment applied to the background simulations with the aim of verifying the radiopurity limits imposed for the materials and determining the background budget of the experiment. The second one is the implementation of a measurement technique that allows reaching the sensitivities required for the measurement of the content of uranium, thorium, and potassium in the liquid scintillator. The validation of the Monte Carlo software of the JUNO experiment (SNiPER) was performed by comparing its results with those of two other simulation codes, in particular with the software Arby, developed at the University of Milano-Bicocca. I was able to study different aspects and many critical issues of the simulation of the background and the results reported by the official tool, such as the application of the quenching factor and the shape of the radioactive β-decay spectra. The spectra of the deposited energy produced by the contaminations in the main components of the JUNO detector were computed with the Monte Carlo codes. The rate of events induced in the detector was assessed based on the imposed radiopurity limits, obtaining the expected total background event rate. The value obtained is lower than the limit set to ensure the final sensitivity of the experiment. This allowed correcting and validating the answer of the official software of the JUNO experiment and verifying the actuality of the radiopurity limits initially defined for the components of the detector. During my Ph.D. I completed the development of the new measurement system, called GeSparK that exploits the coincidence between a liquid scintillator and an HPGe detector to reduce the background of the single HPGe detector. I also worked on the development of a new delayed coincidence technique that exploits the nuclear structure of 239Np, the activation product of 238U, in order to obtain an extremely strong marker of this particular decay and significantly increase the measurement sensitivity compared to the traditional approach. The sensitivity obtained was still insufficient compared to the requests of JUNO and for this reason, it was decided to implement a series of radiochemical treatments. Different treatments have been proposed, tested, and implemented with the two aims of increasing the mass of the measurable sample and reducing the concentration of interfering nuclides. The technique developed for uranium and thorium involves a liquid-liquid extraction phase and the extraction chromatography with UTEVA and TEVA resins respectively before and after irradiation. Two measurements conducted on "blank samples” with the final procedure allowed us to achieve a sensitivity that is compatible with the limits imposed by JUNO for the liquid scintillator at the ppq level.
30
Van, Westrenen Willem. "Thermodynamics of garnet - melt trace element partitioning." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310693.
Full text
31
Choi, In Sup. "Trace elements determination in cancerous and noncancerous human tissues using instrumental neutron activation analysis." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/13385.
Full text
32
Pan, Jinfen. "Bioavailability of trace metals to marine bivalves mediated by dissolved and colloidal organic carbon /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202004%20PAN.
Full text
33
Lawgali, Youssef F. "Trace element levels in Mediterranean grains." Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=136842.
Full textAbstract:
This is the first study to compare total arsenic (As) and other trace elements in the agricultural soils and grain of Eastern, Western and Southern Libya, North Africa and the Middle East (NA & MIDEA). Soil pot experiments and field experiments were conducted to determine the levels of As within wheat grains in Libya. In the soil pot experiments, wheat genotypes were planted in similar soils and yet differences in grain As concentration were found among the cultivars. The highest As accumulation was found in T. durum; however, in the field data the highest levels were found in T. aestrivum. The levels of As and other trace elements found in agricultural soils from the Eastern Western and Southern regions of Libya are examined. Mean As concentrations in the clay mineral agricultural soils of the Eastern Region were nearly 4.8 and 4.1 times higher than in the southern and western regions, respectively. It is possible that the parent material of that region contains elevated levels of As, which are then exhibited in the overlying soil. Differences in the levels of As and other trace elements found in the irrigated agricultural soil of Southern Libya were compared with non-irrigated soil from the same region. Concentrations of P, Zn and As in soil were higher in irrigated compared to non-irrigated soils, while the concentration of Cd is nearly the same in all soil samples. A market basket investigation was conducted to determine the total levels of As and Se in rice purchased from supermarkets. The average level of As in rice from NA & MIDEA is 0.22 mg/kg, comparable with average levels in Australia.
34
Wong, Wang-wah. "Trace organics pollution in the aquatic environment /." [Hong Kong] : University of Hong Kong, 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13498356.
Full text
35
Laera, Andreina. "Fate of trace elements during and after anaerobic digestion : a sequential extraction method and DGT technique to assess bio-accessible trace elements in digestate." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC2011.
Full textAbstract:
Différentes interactions chimiques entre les éléments traces métalliques (ETM) et les composés organiques/inorganiques provenant du substrat et générées au cours du processus de digestion anaérobie détermineront la spéciation des ETM dans les digesteurs anaérobies. Après digestion anaérobie, les digestats sont exposés à des conditions d’oxydation qui peuvent favoriser un changement de la spéciation des ETM et par conséquent de leur bioaccessibilité pour les microorganismes du sol et les plantes lors de l’épandage des digestats sur des terres agricoles en tant qu’amendement organique. Plusieurs techniques ont été utilisées pour évaluer la mobilité, l'accessibilité et la biodisponibilité potentielle des ETM dans les digestats afin d'évaluer les risques pour l'environnement liés à l'utilisation du digestat en tant qu’amendement organique. L’objectif de cette thèse est d'évaluer une procédure d'extraction séquentielle et la technique DGT pour évaluer les ETM bio-accessibles dans des échantillons de digestat. Les échantillons ont été prélevés dans des installations industrielles de digestion anaérobie, traitant un mélange de déchets solides industriels et municipaux ou de boues d'épuration. Les ETM étudiés sont : Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se, Zn et W. Une procédure d'extraction séquentielle, conçue à l'origine pour le fractionnement de la matière organique (MO), a été mise en œuvre pour extraire simultanément la MO et les ETM dans un échantillon de substrat et de digestat. Il a été observé que plus de 50% des quantités totales d'As, Cd, Co, Fe, Mn, Ni et Zn étaient extraites avec les fractions de MO définies de manière opérationnelle dans les deux échantillons. Une extraction plus faible a été observée pour Al, Cr, Cu, Mo et Pb. Ces éléments étaient principalement présents dans la fraction de MO dissoute, où les ETM solubles sont probablement bio-accessibles pour l'absorption microbienne. De plus, une grande partie des éléments a été retrouvée dans la fraction minérale, qui était considérée faiblement bio-accessible. Cependant, la possibilité d'utiliser la méthode susmentionnée a été remise en question par suite de la faible efficacité d'extraction de certains ETM au cours de la procédure d'extraction. De plus, il a été reconnu que les réactifs chimiques utilisés au cours de la procédure d'extraction auraient pu favoriser la dissolution/précipitation des ETM, donc une modification de leur fractionnement. Par rapport aux mesures classiques de mesure des éléments dissous, la technique DGT augmente la sensibilité pour la mesure des ETM dans les boues d'épuration digérées. Cependant, il a été observé que le temps de déploiement des échantillonneurs DGT dans les boues d’épuration digérées devrait être soigneusement évalué. De plus, la matrice de digestat a réduit l’accumulation de certains ETM dans les échantillonneurs DGT. Par conséquent, les ETM labiles de la DGT (c'est-à-dire la plupart des espèces bio-accessibles) peuvent être correctement estimés à condition d'adapter soigneusement le temps de déploiement et d'effectuer une évaluation des effets de matrice dans les digestats. L’évolution temporelle de la concentration des ETM labiles peut être estimée. Par conséquent, l’effet de l’oxygénation des digestats sur la mobilité et la bio-accessibilité des ETM, y compris les fractions labiles et solubles, dans les boues d’épuration digérées a été étudié. L'exposition à l'air du digestat a favorisé la dissolution de Al, As, Co, Cr, Cu, Fe, Mn, Mo et Pb, suggérant une possible augmentation de leur mobilité qui pourrait probablement survenir lors du stockage du digestat dans des réservoirs ouverts ou lors de la manipulation avant l'épandage sur le sol. La fraction des éléments labiles n’augmente que pendant une aération prolongée (sauf pour Fe et Mn), ce qui suggère que leur bio-accessibilité à ne peut augmenter qu’après une aération importante comme celle supposée se produire lors de l’épandage du digestat sur les solsDifferent chemical interactions between trace elements and organic/inorganic compounds originating from the substrate and generated during the anaerobic digestion process will determine the speciation of trace elements in anaerobic digesters. After anaerobic digestion, digestates are exposed to oxidizing conditions which may favor a change of trace elements’ speciation and consequently bio-accessibility for soil microorganisms and plants when digestates are spread on lands as organic amendment. Several techniques were used to assess the mobility, accessibility, and potential bio-availability of trace elements in digestates for environmental risk assessments of digestate utilization as a soil fertilizer. The aim of this thesis is to evaluate a sequential extraction procedure and the diffusive gradients in thin films technique (DGT) to assess bio-accessible trace elements in digestate samples. Samples were taken from full-scale anaerobic digestion plants treating a mixture of industrial and municipal solid wastes or sewage sludge. The elements investigated include Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se, Zn and W. A sequential extraction procedure, originally conceived for organic matter fractionation, was implemented to simultaneously extract organic matter and trace elements in a substrate and digestate sample. It was observed that more than 50% of total As, Cd, Co, Fe, Mn, Ni and Zn were extracted along with the operationally defined organic matter fractions in both samples. Whereas, a lower recovery was observed for Al, Cr, Cu, Mo and Pb. These elements were mainly found in the dissolved organic matter fraction where soluble trace elements are likely bio-accessible for microbial up-take. Moreover, a high portion of elements was found in the mineral fraction, which was considered poorly bio-accessible. However, the feasibility of using the aforementioned method was questioned following the low efficiency of extraction of certain trace elements during the extraction procedure. Moreover, it was acknowledged that chemical reagents employed during the extraction procedure could have promoted a dissolution/precipitation of trace elements and therefore a change in their fractionation. Therefore, DGT technique was tested to fractionate trace elements and it was observed that this technique increased the sensitivity of trace elements monitoring compared to conventional dissolved elements measurements in digested sewage sludge. However, it was observed that the DGT samplers’ deployment time in digested sewage sludge should be carefully evaluated. Additionally, the digestate matrix lowered the accumulation of some trace elements in the DGT samplers. Therefore, DGT labile trace elements (i.e. most bio-accessible species) can be correctly estimated provided a careful adaptation of the deployment time as well as an evaluation of the matrix effect is performed in digestate samples. Unless this, general trend of labile trace elements over time could be estimated such as the distribution of labile trace elements over time in digestate exposed to air. Therefore, the effect of atmospheric air on the mobility and bio-accessibility of trace elements, including labile and soluble fractions, in digested sewage sludge was investigated. The exposure of digestate to air promoted dissolution of Al, As, Co, Cr, Cu, Fe, Mn, Mo and Pb, suggesting that a possible increase in their mobility may likely occur during digestate storage in open tanks or handling before land spreading. Labile elements’ fraction increased only during an increase of aeration (except for Fe and Mn), suggesting that their short-term bio-accessibility can increase only after significant aeration as the one assumed to occur when digestate land spreading takes place
36
Hindersmann, Iris [Verfasser], and Tim [Akademischer Betreuer] Mansfeldt. "Trace elements in floodplain soils - effects of redox conditions on the mobility of trace elements and volatilization of mercury / Iris Hindersmann. Gutachter: Tim Mansfeldt." Köln : Universitäts- und Stadtbibliothek Köln, 2014. http://d-nb.info/1060190427/34.
Full text
37
Denney, Susan, and susan denney@deakin edu au. "Trace metal speciation in the Pieman River catchment, Western Tasmania." Deakin University. School of Ecology and Environment, 2000. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20071107.111755.
Full textAbstract:
The Pieman River catchment has seen continuous mining of economic deposits of gold, silver, lead, copper, zinc and tin since the 1870s. Tributaries of this river which receive mining effluent, either directly or from acid mine drainage (AMID), have total metal concentrations considerably above background levels and are of regulatory concern. The lower Pieman River is however classified as a State Reserve in which recreational fishing and tourism are the major activities. It is therefore important that water entering the lower Pieman River from upstream hydroelectric impoundments is of high quality.
Metals in natural waters exist in a variety of dissolved, colloidal and particulate forms. The bioavailability and hence toxicity of heavy metal pollutants is very dependant on their physico form. Knowledge of the speciation of a metal in natural aquatic environments is therefore necessary for understanding its geochemical behaviour and biological availability.
Complexation of metal ions by natural ligands in aquatic systems is believed to play a significant role in controlling their chemical speciation. This study has investigated temporal and spatial variation in complexation of metal ions in the Pieman River. The influence of pH, temperature, organic matter, salinity, ionic strength and time has been investigated in a series of field studies and in laboratory-based experiments which simulated natural and anthropogenic disturbances.
Labile metals were measured using two techniques in various freshwater and estuarine environments. Diffusive gradients in thin-films (DGT) allowed in situ measurement of solution speciation whilst differential pulse anodic stripping voltammetry (DPASV) was used to measure labile metal species in water samples collected from the catchment.
Organic complexation was found to be a significant regulating mechanism for copper speciation and the copper-binding ligand concentration usually exceeded the total copper concentration in the river water. Complexation was highly dependent on pH and at the river-seawater interface was also regulated by salinity, probably as a result of competitive complexation by major ions in seawater (eg. Ca 2+ ions).
Zinc complexation was also evident, however total zinc concentrations in the water column often far exceeded the potential binding capacity of available ligands. In addition to organic complexation, Zn speciation may also be associated with adsorption by flocculated or resuspended colloidal Mn and/or Fe oxyhydroxides.
Metal ion complexation and hence speciation was found to be highly variable within the Pieman River catchment. This presents major difficulties for environmental managers, as it is therefore not possible to make catchment-wide assumptions about the bioavailability of these metals. These results emphasise the importance of site-specific sampling protocols and speciation testing, ideally incorporating continuous, in situ monitoring.
38
Tinggi, Ujang. "Trace element analysis and nutritional studies in children with phenylketonuria." Thesis, Queensland University of Technology, 1989. https://eprints.qut.edu.au/36913/1/36913_Tinggi_1989.pdf.
Full textAbstract:
Techniques suitable for sample preparation and analysis of copper, iron, zinc, chromium, manganese and selenium in plasma, urine and food samples were further developed to achieve the maximum accuracy and reproducibility. The problems and limitations associated with the analytical techniques were discussed. Special emphasis was given to selenium because of prevalent matrix interferences and losses associated with its analysis especially at the low levels present in some of the samples. Precedence was also given to the analysis of selenium, manganese and chromium in selected foods as such data are currently lacking for Australia. Samples of food from three-day weighed dietary diary as well as blood plasma and urine samples were used for the assessment of the above trace element nutritional status in children with phenylketonuria and their healthy siblings. The results of these findings are discussed.
39
Benneyworth, Laura Mahoney. "Distribution of Trace Elements in Cumberland River Basin Reservoir Sediments." TopSCHOLAR®, 2011. http://digitalcommons.wku.edu/theses/1113.
Full textAbstract:
The U.S. Army Corps of Engineers, Nashville District, maintains ten reservoirs in the Cumberland River Basin in Kentucky and Tennessee, and has been monitoring sediment chemistry in the reservoirs since 1994. The purpose of this study is to evaluate the sediment data collected from the reservoirs from 1994 to 2010 to determine if there are any spatial patterns of the trace elements: arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, and zinc. The results indicated that trace element levels were consistent with national baseline concentrations measured by the U.S. Geological Survey. Center Hill reservoir had the greatest number of trace element concentrations (all except cadmium) that were significantly higher when compared to all other reservoirs. The degree of urbanization in the reservoir basins was based on population density from the 2000 Census and the percentage of developed land using the 2006 national land cover dataset. Aquatic toxicity values were used as a measure of sediment quality. The reservoirs with the worst aquatic toxicity rankings were not the most urban, instead they were the reservoirs with the longest retention times. Therefore, it may be concluded that retention time has a larger effect on Cumberland River Basin sediment concentrations than the type of land use or the degree of urbanization. The results also indicate that it may be prudent to include an evaluation of quality based on aquatic toxicity when monitoring sediment quality, and that when reservoirs are the subject of sediment quality assessments, the consideration of the physical properties of the reservoir, especially the retention time, is essential for a comprehensive evaluation. This may also imply that sediment quality in reservoirs may effectively be regulated by water resource management techniques at the reservoirs that affect retention time.
40
Havercroft, Janet M. "Boron and other trace elements in human tissues and fluids." Thesis, University of Surrey, 1989. http://epubs.surrey.ac.uk/842751/.
Full textAbstract:
The multielemental technique of inductively coupled plasma source mass spectrometry (ICP-MS) was used to measure the elemental concentration of boron and 28 other elements within blood and its fractions, saliva, urine, hair, nails, synovial fluid, brain and bone samples. A number of biological standard reference materials were also analysed: IAEA A13 animal blood and H4 animal muscle, NIST 1577A bovine liver and SRM909 human serum, and SINR 0920 Chinese hair. Boron levels were found to be in the order of 30-40ng/mL in saliva and synovial fluid, 150ng/mL in blood, 1mug/mL in urine, 2-4mug/g in hair, bone and brain, and 10mug/g in nails. Other elements ranged in concentration from sub-nanogram/gram (or mL) to percentage (%w/w) levels. Associations of boron with other trace elements, such as boron and calcium in blood, were also investigated in the various tissues and fluids, as were variations due to age and sex. Frequency distribution curves were plotted for trace elements and micronutrients in all tissues and fluids. Since most elements demonstrated a symmetrical distribution in blood, this was thought to be indicative of the amount of homeostatic regulation, rather than the essentiality of the element. The distribution of elements among the various sample matrices, and occurrences of elemental or matrix interdependence, were investigated. Rubidium and caesium, also calcium and strontium, for example, were consistently found to behave in similar ways among the clinical specimens. In addition, alterations in elemental levels due to factors such as age and sex were assessed in the range of tissues and fluids. Full descriptions of the elemental content of brain, bone and synovial fluid samples were obtained. Comparisons were made between rheumatoid arthritic (RA) and control subjects for brain and bone, and between RA and osteoarthritic (OA) patients for the synovial fluid. Boron was shown to be "very highly significantly" depleted in RA bone (at the 0.1% level). Other elements showing variations in bone and brain were lithium and iron. Iron was also at lower levels in RA synovial fluid compared to OA, in contrast to phosphorus, copper and zinc, where increases were seen. Elemental levels were linked with other clinical parameters in synovial fluid, such as crystal content and white blood cell count (a measure of the extent of inflammation), to assess any possible variations. Fluid containing crystals displayed elevated levels of scandium, strontium and caesium. Several elements showed a positive correlation with white blood cell count; these were caesium, magnesium, phosphorus, copper, zinc and rubidium.
41
Petronda, Andrea. "Trace elements in the Cyprus environment associated with urban development." Thesis, University of Surrey, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.606802.
Full textAbstract:
Since Cyprus entered the European Union (EU) in 2004, there has been a rapid expansion associated with the development of major motorway networks, tourist centres, commercial and industrial activity within major cities. To date, very little research has been undertaken in Cyprus, to assess the impact of such urban development on chemical levels in the environment. This research aimed to assess the possible levels of chemicals• in the southern part of Cyprus using the olive tree as a potential biomonitor for evaluating the degree of Mn, Cu, Zn, Pb, Cr, Co, Ni, V, Mo, Cd and As contamination in Cyprus. Olive tree bark, leaves, tree-rings, olives (olive oil) and surface soils were collected from four areas (rural, tourist, urban and transport). [n addition, samples were collected from different urban centres namely: Nicosia, Lamaca, Limassol and Paphos. This study confirmed that olive tree bark could be used to assess the release of chemicals from anthropogenic sources, especially from urban and transport activities. Unwashed olive bark lead levels for highways (mean 25.2; range 0.63 to 119 mg/kg Pb dry weight) were significantly higher than for rural areas (1.62; 0.08 to 3.81 mg/kg Pb d.w.). The other parts of the olive tree have provided data on the mobility and accumulation of the elements and possible links between the different media (tree-rings, leaves, olives, olive oil and surrounding surface soils). The overall elemental levels for the southern part of Cyprus were found to be lower than reported literature values. This research has also found that the highest elemental levels are in samples from urban (Nicosia) and from transport sites. This is due to construction-demolition activities, road expansion (including re-surfacing and widening) and high vehicular traffic densities. Unwashed tree ring cores in Lamaca showed high levels of copper (41 .3 to 54.9 mg/kg Cu d.w.) in segments which represented 20-30 years ago, showing the effect of the closure and decommissioning of the petroleum refinery. The elemental levels found in the tourist and rural areas were significantly lower. Rural or 'non-polluted' sites were used to provide control data for Cyprus. In addition, high elemental levels were not found in the olives and olive oil. Relatively high zinc levels (1.83 and 3.05 mg/kg Zn) were found in olive oils bought from the Cyprus and UK markets. There is no set limit for zinc which makes the evaluation of the risk difficult. Comparing the levels with the literature, the data was in agreement with levels found in other countries. Arsenic (total and speciation) analysis of the water and surrounding media (soils and poultry manure), near Nicosia, showed the highest arsenic levels to be 59.8 1J9/1 As in water, with the predominant species to be arsenate (Asv). A few groundwater As levels surpassed the World Health Organisation Guideline for drinking water (10 1Jg/l As). In conclusion, continuous monitoring is necessary, as the island is rapidly growing and developing, especially major motorways and tourist/city centres. The database created through this research will be able to assist and provide a leading start to future studies for other researchers in Cyprus and other countries, especially in the Mediterranean who grow olives and are undergoing urban development
42
Earle, Kay Elizabeth. "Determination of trace elements in relation to diabetes in man." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37679.
Full text
43
Pimenta, Joana Raimundo. "Accumulation, responses and genotoxicity of trace elements in octopus vulgaris." Doctoral thesis, Faculdade de Ciências e Tecnologia, 2010. http://hdl.handle.net/10362/4895.
Full textAbstract:
Dissertação apresentada para obtenção do Grau de Doutor em Bioquímica pela Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaCommon octopus, Octopus vulgaris, is a sedentary cephalopod inhabiting coastal waters and thus susceptible to be exposed to local contamination. Octopuses were captured in three coastal areas with contrasting environmental contamination: Matosinhos, Cascais and Olhão. Levels of V, Cr, Fe, Co, Ni, Zn, Cu, As, Se, Cd, Hg and Pb were analysed in various tissues of octopus: digestive gland, gills, kidney, gonads, posterior salivary glands, branchial hearts, ink sac, stomach, skin, mantle and arm. The different metal concentrations in the eleven analysed tissues are apparently a consequence of the role of metals in metabolic functions (e.g. gonads, ink sac, kidney, gills and salivary glands), although non-essential elements in digestive gland, branchial hearths, kidney and ink sac may be linked to specific ligands or excretory/detoxification mechanisms. Metal levels found in octopus tissues (e.g. Cd, Pb and Hg) were in line with concentrations registered in the environment. Lead isotopic ratios in octopus digestive gland allowed separation of individuals according to environmental Pb sources (anthropogenic and natural). The consistent differences between organisms captured in the two areas (Matosinhos and Olhão) points that Pb isotopic signature provides a useful tool to distinguish octopus populations. Concentrations of Hg also responded to environmental availability and, for the first time, levels of MeHg were determined. Higher Hg, MeHg and Se concentrations were observed in digestive gland and MeHg (%) in mantle. Good relations were obtained between digestive gland and mantle for Hg and MeHg, suggesting an efficient transport from digestive gland and storage in mantle. Selenium seems to have a protective role against Hg assimilation. Demethylation processes may occur being more noticeable in organisms from the more contaminated area. When metals are accumulated, only a minor percentage is associated with organelles. However, levels in these sub-cellular fractions respond to the enhanced concentrations in the whole tissue. Moreover, it seems that the role of the elements in the cells, and consequently their association with the sub-cellular fraction, superimpose the response to availability. Within cytosolic fraction metals are associated either with low and high molecular weight proteins, being metallothioneins an important detoxification mechanism when levels, mainly Cd, exceeded a threshold value. Although different detoxification mechanisms were observed in octopus tissues, DNA damages were registered mainly in digestive gland. A good agreement was obtained with environmental availability, tissue function and cellturnover. Cadmium seems to be a strong strand breakage inducer. Octopus can be used as bioindicator.
Fundação para a Ciência e a Tecnologia, bolsa de doutoramento (SFRH/BD/37730/2007
44
Marchand, Charlotte. "Phytoremediation of soil contaminated with petroleum hydrocarbons and trace elements." Doctoral thesis, Linnéuniversitetet, Institutionen för biologi och miljö (BOM), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-60839.
Full textAbstract:
The rapid urbanization and industrialization has led to an increase of disposal petroleum hydrocarbons (PHC) and trace elements (TE) into the environment. These pollutants are considered as the most toxic contaminants in the world due to their persistence in the environment, and the long range of toxicological effects for living beings. Recent concerns regarding the environmental contamination have initiated the development of several remediation technologies, including physical, chemical, and biological approaches. In this thesis, gentle soil remediation options (GRO) were investigated at different scales for the reclamation of PHC and TE co-contaminated soil. In the first part of this thesis, laboratory experiments were performed to characterize PHC and TE contaminated soil as well as the indigenous microorganisms (bacteria and fungi) present inside these contaminated soil. It was found that the studied aged contaminated soil had a negative effect on earthworm’s development and L. sativum biomass. Moreover, a high respiration of microorganisms attributed to the transformation/ mineralization of organic matter or/and organic pollutants was observed. This presence of viable microorganisms suggested an adaptation of microorganisms to the contaminant. Further results showed that the long-term exposure of soil microorganisms to high PHC concentration and the type of isolation culture media did not influence the ability of isolates to effectively degrade PHC. However, phylogenic affiliation had a strong on PHC biodegradation. In the second part of this thesis, preliminary studies in greenhouse were assessed to investigate the ability of M. sativa assisted by compost in the greenhouse aided-phytoremediation of PHC and TE. It was found that compost incorporation into the soil promoted PHC degradation, M. sativa growth and survival, and phytoextraction of TE. Residual risk assessment after the phytoremediation trial also showed a positive effect of compost amendment on plant growth and earthworm development. Pilot scale ecopile experiment carried out in the third part of this thesis allow a reduction of up to 80% of PHC and 20% of metals after 17 months. This research demonstrated that M. sativa and H. annus were suitable for phytodegradation of PHC and phytoextraction of TE. Results from this thesis are helpful for further full-scale phytoremediation studies.
45
Tsoi, Yeuk Ki. "Prevalent instrumentation and material in trace elements analysis and speciations." HKBU Institutional Repository, 2011. http://repository.hkbu.edu.hk/etd_ra/1250.
Full text
46
Üzelyalçın, Berna Harsa Şebnem. "Effects Of Trace Elements On The Production Of Baker's Yeast/." [s.l.]: [s.n.], 2002. http://library.iyte.edu.tr/tezler/master/biyoteknoloji/T000146.rar.
Full text
47
Ferraro, Stefano. "Influence of trace elements on secondary die-cast aluminium alloys." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423822.
Full textAbstract:
Recycling play a key role on saving of natural resources and on reducing pollution. The recycling of aluminium alloys is also cost-effective, since it reduce the material cost and creates a considerable energy-saving. The use of recycled Al alloys (usually called secondary) has improved in recent years also because of their comparable mechanical properties with primary aluminium alloys.
During the production of secondary aluminium alloys, the scrap are mixed regardless of their specific chemical composition, and then master alloys or pure elements are added to the molten metal. Furthermore, certain impurity elements are either difficult or expensive to remove, and their role in mechanical properties can be important. Due to the presence of these additional trace elements, a number of complex intermetallic phases can therefore form in multi-component Al-Si alloys. Mechanical and physical properties of alloys and castings are strongly related to sizes, morphologies and distribution of these intermetallic phases, which are in turn a function of alloy composition and cooling rate.
The Al–Si based alloys are transversally used in different foundry processes. Among all the technologies, high-pressure die-casting (HPDC) represents the most common process to produce automotive components by secondary Al–Si alloys because it allows one to increase the production by lowering the cycle time and to obtain economically components with complex geometries and high quality surface.
The effects of trace elements and intermetallics phases on features of aluminium castings are still not fully understood, especially when components are made by means of HPDC process. The motivation of the research presented in this doctoral thesis was, therefore, to fill this gap in knowledge. The study has aimed at understanding the influence of various trace elements on the microstructure and mechanical properties of secondary die-cast aluminium alloys and, in particular, on secondary AlSi9Cu3(Fe) die-cast alloys.
A literature review and a sufficient background of previously reported results on the influence of trace elements on the features of aluminium alloys as well as the formation of intermetallic phases were carried out. It was found that the mechanical and microstructural analysis generally referred to primary cast Al alloys with low concentration of trace elements outside of those studied. Furthermore the samples were usually produced on gravity die-cast, while some intermetallics phases were frequently observed in high-pressure die-casting, where higher cooling rates and different feeding conditions exist.
Special attention has been given to:
The effects of Bismuth addition on secondary die-cast aluminium alloys: Bismuth substitute the lead in free-cutting wrought Al alloys, and this is leading to a steady increase of Bi content in secondary Al alloys due to the recycling process.
The nucleation temperature of primary Fe-rich intermetallic compounds, as function of Fe, Mn and Cr content and cooling rate: Fe-rich phases have a high specific gravity and tend to segregate to the bottom of aluminium melts and holding furnaces. These phases form primary solid particles, generally called sludge, thus reduce the effective capacity of the furnace.
The influence of Fe, Mn and Cr addition, separately or in combination, on the microstructural and mechanical characteristics of secondary die-cast aluminium alloys: sludge crystals are hard and brittle compact inclusions which can compromise the machining operations, with a considerable effects on the cutting tool life, and even more degrade the mechanical and physical properties of the component. As recycling of aluminium alloys becomes more common, sludge will be a problem of increasing importance due to the concentration of Fe, Mn and Cr in the scrap cycle.Il riciclaggio gioca un ruolo chiave sul risparmio delle risorse naturali e sulla riduzione dell'inquinamento. Il riciclo dell'alluminio è oltretutto economicamente conveniente, in quanto riduce il costo del materiale a fronte di un considerevole risparmio energetico. L'utilizzo di leghe di alluminio riciclate (comunemente chiamate leghe secondarie) è aumentato negli ultimi anni anche grazie alle loro proprietà meccaniche, le quali sono in alcuni casi comparabili con le leghe di alluminio primarie. Durante il processo di produzione dell'alluminio secondario i rottami vengono mescolati assieme indipendentemente dalla loro composizione chimica specifica. Al termine del processo fusorio la composizione viene regolata tramite l'aggiunta di leghe madri o di metalli puri. Tuttavia alcune impurezze presenti nel rottame rimangono all'interno della lega in quanto il loro processo di rimozione è complicato o non economicamente conveniente. A causa della presenza di questi elementi in traccia, un certo numero di fasi intermetalliche complesse si può formare nei getti. Di conseguenza le proprietà meccaniche e fisiche dei componenti in lega di alluminio sono fortemente correlate alla dimensione, alla morfologia e alla distribuzione di tali fasi intermetalliche, le quali sono a loro volta funzione della composizione della lega e della velocità di raffreddamento del metallo. Grazie alle loro elevata colabilità, le leghe Al-Si sono molto utilizzate in tutti i processi di fonderia. Tra le diverse tecnologie, la pressocolata (HPDC - high-pressure die-casting) rappresenta il processo più comune per la produzione di getti di alluminio nel settore automotive. Questa tecnologia permette di ottenere componenti con geometrie complesse e un'ottima finitura superficiale con una riduzione dei costi grazie alla elevata produttività e al basso tempo ciclo. Gli effetti degli elementi in traccia e delle fasi intermetalliche sulle proprietà dei getti in alluminio non sono ancora del tutto noti, soprattutto quando i componenti sono prodotti tramite pressocolata. Obiettivo di questo lavoro di dottorato di ricerca era perciò quello di supplire a queste lacune. Lo scopo del presente lavoro è studiare l'influenza di diversi elementi in traccia sulla microstruttura e sulle proprietà meccaniche di getti in lega secondaria di alluminio prodotti mediante pressocolata, ed in particolare nella lega AlSi9Cu3(Fe). In prima analisi, è stata condotta una recensione della letteratura sull'influenza degli elementi in traccia sulle proprietà delle leghe di alluminio e sulla formazione delle fasi intermetalliche. Questo ha permesso di constatare che le caratteristiche meccaniche e microstrutturali legate alla presenza di fasi indesiderate sono normalmente valutate in getti prodotti con leghe primarie di alluminio, in cui è presente una bassa concentrazione di impurezze al di fuori di quelle studiate. Inoltre i campioni studiati sono generalmente prodotti mediante colata in gravità, mentre alcune fasi intermetalliche sono tipiche della pressocolata, in cui la velocità di raffreddamento è molto più elevata e sono presenti diverse condizioni di alimentazione e di riempimento dello stampo. Nel presente lavoro è stata posta particolare attenzione a: Gli effetti dell'aggiunta di Bismuto nelle leghe di alluminio secondarie pressocolate: il Bismuto ha sostituito il Piombo nelle leghe di alluminio da deformazione plastica ad alta lavorabilità alle macchine utensile. Questo ha comportato un aumento del contenuto di Bismuto nelle leghe secondarie di alluminio a causa del processo di riciclaggio degli sfridi di lavorazione. La temperatura di nucleazione dei precipitati intermetallici ricchi in Ferro in funzione della velocità di raffreddamento e della concentrazione in lega di Ferro, Cromo e Manganese: le fasi ricche in ferro hanno un elevata densità e tendono a segregare sul fondo del fondo del forno di mantenimento. L'insieme di queste fasi primarie forma una fanghiglia, chiamata sludge, che riduce l'effettiva capacità del forno. L'effetto dell'aggiunta di Ferro, Cromo e Manganese, singolarmente o in combinazione tra di loro, sulle caratteristiche microstrutturali e meccaniche delle leghe di alluminio secondarie pressocolate: le particelle di sludge sono inclusioni compatte dure e fragili, le quali possono compromettere le operazioni di lavorazione meccanica, con una conseguente riduzione della durata degli utensili, ed una marcata riduzione delle proprietà meccaniche e fisiche del componente. Il problema delle particelle di sludge nelle leghe secondarie di alluminio assume un'importanza sempre maggiore a causa dell'aumento del riciclo dell'alluminio e della presenza di Fe, Mn e Cr nel ciclo del rottame.
48
Miao, Aijun. "Trace metal accumulation and toxicity in marine phytoplankton /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202006%20MIAO.
Full text
49
Jin, Li. "Determination of trace metals and copper complexation in freshwater systems of the Bonavista Peninsula, Newfoundland by stripping voltammetry." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq25853.pdf.
Full text
50
Ataro, A., Robert Ian McCrindle, B. M. Botha, Cheryl Myra Ethelwyn McCrindle, and P. P. Ndibewu. "Quantification of trace elements in raw cow’s milk by inductively coupled plasma mass spectrometry (ICP-MS)." Elsevier, 2008. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000153.
Full textAbstract:
The levels of trace elements are an important component of safety and quality of milk. While certain elements
such as chromium are essential at low levels, an excess can result in deleterious effects on human
health. International quality control standards for milk are published by the Codex Alimentarious Commission
and levels of heavy metals in milk intended for human consumption are routinely monitored.
This paper describes a new method for demonstrating the levels of V, Cr, Mn, Sr, Cd and Pb in raw cow’s
milk, using an ICP-MS. Samples (n = 24) of raw cow’s milk were collected from dairy farms close to mines
in Gauteng and North West Provinces of South Africa. In order to destroy organic matrix, each freeze dried
milk sample was mineralised by using a microwave assisted digestion procedure. Concentrations of trace
elements in digested milk samples were measured by ICP-MS. A whole milk powder reference material
(NIST SRM 8435) was used to evaluate the accuracy of the proposed method. It was found that the levels
of V, Cr, Mn, Sr, Cd and Pb obtained using the new method showed concordance with certified values.