Добірка наукової літератури з теми "Copper isotope fractionation"

The widespread hypoxic conditions of the tumor microenvironment can impair the metabolism of bioessential elements such as copper and sulfur, notably by changing their redox state and, as a consequence, their ability to bind specific molecules. Because competing redox state is known to drive isotopic fractionation, we have used here the stable isotope compositions of copper (65Cu/63Cu) and sulfur (34S/32S) in the blood of patients with hepatocellular carcinoma (HCC) as a tool to explore the cancer-driven copper and sulfur imbalances. We report that copper is 63Cu-enriched by ∼0.4‰ and sulfur is 32S-enriched by ∼1.5‰ in the blood of patients compared with that of control subjects. As expected, HCC patients have more copper in red blood cells and serum compared with control subjects. However, the isotopic signature of this blood extra copper burden is not in favor of a dietary origin but rather suggests a reallocation in the body of copper bound to cysteine-rich proteins such as metallothioneins. The magnitude of the sulfur isotope effect is similar in red blood cells and serum of HCC patients, implying that sulfur fractionation is systemic. The 32S-enrichment of sulfur in the blood of HCC patients is compatible with the notion that sulfur partly originates from tumor-derived sulfides. The measurement of natural variations of stable isotope compositions, using techniques developed in the field of Earth sciences, can provide new means to detect and quantify cancer metabolic changes and provide insights into underlying mechanisms.

In this study we investigated the distribution of dissolved and particulate zinc (dZn and pZn respectively) and its isotopes in the Subantarctic Zone as part of a Geotraces Process voyage. dZn and pZn depth profiles contrasted each other, with dZn showing depletion within the euphotic zone while pZn profiles showed enrichment. Fitting a power law equation to the pZn profiles produced an attenuation factor of 0.82, which contrasted values for particulate phosphorus, cadmium and copper. The results indicate that zinc has a longer regeneration length scale than phosphorus and cadmium, but shorter than copper. The differential regeneration of pZn relative to that of particulate phosphorus likely explains why dZn appears to have a deeper regeneration profile than that of phosphate. The dZn isotope (δ66Zndissolved) profiles collected across the Subantarctic Zone showed differing profile structures. For one station collected within an isolated cold-core eddy (CCE), δ66Zndissolved showed surface enrichment relative to deep waters. The corresponding pZn isotope profiles within the CCE did not show enrichment; rather, they were subtly depleted in surface waters and then converged to similar values at depth. Zinc isotope fractionation can be explained through a combination of fractionation processes associated with uptake by phytoplankton, zinc complexation by natural organic ligands and zinc regeneration from particulate matter.

Copper is a critical enzyme cofactor in the body but also a potent cellular toxin when intracellularly unbound. Thus, there is a delicate balance of intracellular copper, maintained by a series of complex interactions between the metal and specific copper transport and binding proteins. The gastrointestinal (GI) tract is the primary site of copper entry into the body and there has been considerable progress in understanding the intricacies of copper metabolism in this region. The GI tract is also host to diverse bacterial populations, and their role in copper metabolism is not well understood. In this study, we compared the isotopic fractionation of copper in the GI tract of mice with intestinal microbiota significantly depleted by antibiotic treatment to that in mice not receiving such treatment. We demonstrated variability in copper isotopic composition along the length of the gut. A significant difference, ∼1.0‰, in copper isotope abundances was measured in the proximal colon of antibiotic-treated mice. The changes in copper isotopic composition in the colon are accompanied by changes in copper transporters. Both CTR1, a copper importer, and ATP7A, a copper transporter across membranes, were significantly down-regulated in the colon of antibiotic-treated mice. This study demonstrated that isotope abundance measurements of metals can be used as an indicator of changes in metabolic processes in vivo. These measurements revealed a host–microbial interaction in the GI tract involved in the regulation of copper transport.

A non-metallic flow-through reaction cell is described, designed forin situtime-resolved X-ray diffraction coupled with stable isotope analysis. The experimental setup allows the correlation of Cu isotope fractionation with changes in crystal structure during copper sulfide dissolution. This flow-through cell can be applied to many classes of fluid–mineral reactions that involve dissolution or ion exchange.

Depuis la fin du 19ème siècle, le traitement des vignes par des fongicides cupriques a engendré une augmentation de la teneur en cuivre (Cu) dans les sols viticoles, ainsi que dans les écosystèmes aquatiques en aval. Cette thèse vise à mieux comprendre le devenir de ce Cu dans un agrosystème basé sur l’étude du fractionnement isotopique du 65Cu/63Cu. Les résultats montrent que durant 4 à 5 décennies de culture de vignes, les sols en surface se sont enrichis en Cu de 9 à 28 fois par rapport au fond géochimique et que les minéraux argileux jouent un rôle important dans l’accumulation du Cu. Lors des événements pluvieux, ~1% du Cu appliqué est mobilisé, essentiellement lié à des argiles. Le bassin d’orage récoltant les lames ruisselantes retient en moyenne 68% du Cu dissous et plus de 92% du Cu particulaire. Les ratios isotopiques du Cu dans le bassin indiqueraient la sorption du Cu dissous dans les sédiments, ainsi que la réduction du Cu(II) in situ due à des processus biogéochimiques
Since the end of the 19th century, the use of copper (Cu)-based fungicides has resulted in increased Cu concentrations in vineyard soils, but also in downstream aquatic ecosystems. The aim of the thesis was to better understand the fate of this Cu in an agrosystem based on assessing Cu isotope fractionation (65Cu/63Cu). The results have shown that the surface vineyard soils have become enriched in Cu from 9 to 28 times compared to the background level during 4 to 5 decades of vine-growing and that clay minerals were the major Cu sorbing phases in the soils. During rainfall, runoff mobilized ~1% of the applied Cu during the, mainly associated with clays. The stormwater wetland collecting the runoff retained in average 68% of the dissolved and more than 92% of particulate Cu. Cu isotope ratios measured in the wetland suggested dissolved Cu sorption to the sediments and in situ reduction of Cu(II) due to biogeochemical processes

The nature of Cu isotope fractionation in natural Cu-Fe-S minerals was investigated through acid ferric sulfate leaching of copper ore from Morenci, Arizona. Copper isotope composition of the derived solutions varies from δ⁶⁵Cu = 0.47‰ to 5.21‰ over the course of progressive copper extraction. High δ⁶⁵Cu values characterize solutions collected in the first half of the leach, while the solutions collected between 35% and 45% copper recovery exhibit lower δ⁶⁵Cu values. This general pattern was observed for both bacterially-mediated and abiotic leaching. Sulfate solutions derived from dissolving pure djurleite show variable Cu isotope compositions as well, although the range is protracted from δ⁶⁵Cu = 0.01‰ to 1.21‰. As the Cu:S ratio of the remaining sulfide decreases, crystal structure parameters change as mineralogy passes through a series of nonstoichiometric copper sulfides. Mineralogy converges to yarrowite near 44% copper dissolution. Crystal chemical studies show that distribution of the two copper-sulfur bond coordination geometries, triangular planar and tetrahedral, in the copper sulfides, approximately corresponds to changes in δ⁶⁵Cu of the leachates. In particular, the proportion of CuS3 relative to CuS4 groups decreases from Cu/S = 2.00 (chalcocite) to 1.40 (geerite). Between Cu/S = 1.40 to 1.00 (covellite), the relative proportion of CuS3 groups increases slightly. Connection between coordination number and Cu isotope fractionation implies affinity of CuS₃ groups for the heavier, ⁶⁵Cu, isotope. This can be justified through bond length-bond strength arguments. Solutions from bornite dissolution vary from δ⁶⁵Cu = -0.79‰ to 1.14‰, with the largest values associated with solutions from early stage of reaction (up to 15% copper removal). Around 25% dissolution, δ⁶⁵Cu of the solution approaches that of the original bornite (δ⁶⁵Cu = 0.02‰). This is explained by disappearance of all remaining CuS₃ groups. Sulfur isotope compositions of solutions and sulfides derived from djurleite leaching were determined to investigate the possibility of intra-mineral fractionation. Very soon after reaction initiation, δ³⁴S of both sulfur reservoirs reach a steady-state with sulfate solutions about 2‰ enriched in ³⁴S relative to residual sulfide. Unlike the case of Cu isotopes, the main partitioning affecting S isotopes is exchange between sulfate and sulfide.

Master of Science
Department of Geology
Matthew E. Brueseke
Mid-Miocene epithermal Au-Ag ores of the northern Great Basin USA are related to magmatism associated with the inception of the Yellowstone hotspot. The geochemical chemical connection between these ores and spatially and temporally related volcanism is not well understood, but has been suggested (Kamenov, 2007; Saunders et al., 2015). These Cu- and Pb- isotope studies show that the ore and associated gangue minerals have different sources of Pb, which supports evidence that the metal(loids) originate from a deep magmatic source (Saunders et al., 2008). Cu isotopes as a tool for exploring linkages between ore deposits and related volcanic rocks is a new and evolving field. A suite of mid-Miocene Northern Great Basin (NGB) and Snake River Plain (SRP) volcanic rocks was analyzed by aquaregia leach for their δ⁶⁵Cu compositions. These samples have all been previously characterized and include basalts, trachybasalt, basaltic andesites, and basaltic trachyandesites that are representative of regional flood basalt magmatism and younger basalt eruptions in central Idaho. Included are rocks from the Santa Rosa-Calico volcanic field, NV (e.g., Buckskin-National district); Owyhee Mountains, ID (Silver City District); Midas, NV region, near Jarbidge, NV; and a locality proximal to Steens Mountain, OR. Also included are two Pleistocene basalts from the central Snake River plain unequivocally related to the Yellowstone hotspot volcanism (McKinney Basalt and Basalt of Flat Top Butte), and one Eocene basalt from the Owyhee Mountains that is related to pre-hotspot arc volcanism. International rock standards ranging from ultramafic to intermediate were also analyzed in this study for comparison. Our new δ⁶⁵Cu data greatly expands the range of known Cu isotopic compositions for basalts, with values ranging from -0.84‰ to +2.61‰. These values overlap with the δ⁶⁵Cu of regional ores, further suggesting a link between the source(s) of the ores and the NGB rocks. The range of δ⁶⁵Cu values also overlaps with mantle rock values, suggesting that the Cu isotopic composition may be a signature derived from the mantle source. Fractionation mechanisms that cause such a broad range in Cu isotopes are still unclear but liquid-vapor transitions and mantle metasomatism are being explored. Furthermore, δ⁶⁵Cu values of international rock standards reported in this study did not agree with previously reported data (Archer and Vance, 2004; Bigalke et al., 2010; Moeller et al., 2012; Liu et al., 2014, 2015) suggesting that aquaregia leach may not be a preferable technique when analyzing volcanic rocks.

The distribution of the stable isotopes of Cu and Fe in nature is susceptible to isotope fractionation processes during the biogeochemical cycle. Since Cu and Fe are redox sensitive metals, differences in their oxidation states can lead to variations in the stable isotope composition of the aquatic species or compounds that they form. Stable isotopes of Cu and Fe have recently been used to trace metal redox cycles, nutrient pathways, metal contaminant sources and to develop isotopic biosignatures. The objective of this project was to study the geochemical processes governing the isotopic fractionation of Cu and Fe in mine impacted sites, including processes related to mineral processing. One of the key questions was to explain the role of bacteria in the variations of the isotopic composition of Cu and Fe. First, bioleaching and electroleaching of a chalcopyrite concentrate were performed. During the chalcopyrite leaching in both experiments the first release of Cu to the leachate is enriched in the heavier Cu isotope as a product of oxidative dissolution. At the later stages of leaching, the δ65Cu values for the leachate are similar to the initial material, confirming an equilibrium fractionation in a closed system. In the case of Fe isotope fractionation the dissolution of pyrite at redox potentials higher than 600mV leads to an enrichment of the heavier Fe isotope in the leachate in the bioleaching experiment, mainly regulated by the formation of secondary minerals such as jarosite. Soil bacteria were studied in three different experimental scales using pot, lysimeters and field experiments, amended with autochthonous plant growth promoting bacteria. Roots and plants from pots showed no variation in their Fe and Cu isotope composition compared to non-amended samples. However, plants growing in the amended substrates regardless of their experimental scale, showed variations in the Fe and Cu isotope composition of their roots with an increase in the heavier Cu isotope. Siderophores released either by bacteria or the plant can complexate available Cu and Fe in the soil, causing a change in the isotope fractionation of those metals. The second question is related to the biogeochemical cycle of Cu and Fe. In mine tailings the sulphide oxidation resulted in an enrichment of the lighter Cu isotope in secondary phases in the oxidized zone of the tailings compared to the original isotope composition in the unoxidised mineral. Precipitation of covellite at the oxidation front of the tailings profile resulted in a significant enrichment of the lighter Cu isotope in the bulk soil with a δ65Cu value as low as -4.35 ±0.02 ‰. Fe isotope fractionation in the Kristineberg test cell varied due to processes such as Fe(II)-Fe(III) equilibrium and precipitation of Fe-(oxy)hydroxides at the oxidation front, where δ56Fe values were higher than in the initial material. As a way to link the obtained results from this thesis, a self-restored mine site was studied. A variation towards higher δ65Cu values was seen from rocks, to water and biofilms. Cu absorption mainly by extrapolymeric substances and secondary mineral precipitation regulates the isotopic composition of the biofilm. Oxidative weathering of sulphide minerals and further precipitation of Fe-(oxy)hydroxides are considered to be the main causes for Fe isotope fractionation in this area. Summing up, this thesis provides several field studies to corroborate the data observed in the lab regarding processes that are important for the biogeochemical cycling of metals and could be further applied to the extraction of metals or for remediation purposes.
Godkänd; 2013; 20131028 (natper); Dissertation to be held in public in room E632 on Tuesday 17th of December at 10:00 am. External examiner: Dr. Dominik Weiss, Department for Earth Sciences and Engineering, Imperial College London. Chairman: Professor Björn Öhlander, Division of Geosciences and Environmental Engineering, Luleå University of Technology. --- Tillkännagivande disputation 2013-11-22 Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Nathalie Pérez Rodríguez Ämne: Tillämpad geologi/Applied Geology Avhandling: Biotic and Abiotic Isotope Fractionation of Copper and Iron. From the Lab to the Field Scale Opponent: Dr Dominik Weiss, Reader, Department of Earth Science & Engineering, Imperial College of London, UK Ordförande: Professor Björn Öhlander, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Tisdag den 17 december 2013, kl 10.00 Plats: E632, Luleå tekniska universitet

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Many isotope proxies have been applied to study the prosperous iron oxide copper gold (IOCG) province in the eastern Gawler Craton (E.G.C) and Au mineralised region of the cental Gawler Craton (C.G.C), in Southern Australia. Yet, copper isotope proxies- an indicator for low temperature fluid flow and sulfide mineralisation- have yet to be applied to the region. In this study, purification techniques using automatic column chromatography were demonstrated during separation of Cu from matrix elements. Cu isotopes – 65Cu & 63Cu – were used to understand the extent of mantle input and mantle metasomatism, potentially responsible for the Cu in IOCG mineralisation. Eleven samples were gathered. Three mafic enclaves and four intrusives from the Central Gawler Gold Province and four intrusives from the eastern Gawler IOCG province. Separation using automatic column chromatography proved challenging, with matrix elements abundant throughout the purified fractions (Co, Ti, Fe, Mg, Na), due to poor separation. Ti proved to a major interference during isotopic analysis using a Multicollector-ICP-MS, positively offsetting values. E.C.G samples showed the most positively fractionated δ65Cu values (+0.69 ± 0.024‰ to +1.422 ± 0.077‰). Enclaves from the C.G.C showed the most negatively fractionated δ65Cu values (-0.053 ± 0.023‰ to -0.897 ± 0.006‰), while intrusives from this region showed more positive δ65Cu values (+0.084±0.23‰ to +0.397±0.011‰). All samples showed a lack of hydrothermal alteration. Magmatic sulphide-containing E.G.C samples had the most positive δ65Cu values; which cannot be explained by current understanding of Cu isotope fractionation during sulfide saturation. This trend may instead be attributed to a heterogeneous sub-continental lithospheric mantle (SCLM) source. In contrast the negative δ65Cu values of mafic enclaves is possibly caused by assimilation of S-type granitic crust and/or possibly due to a heterogeneous SCLM source.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2019

Copper (Cu) is an essential micronutrient for plants and many microorganisms, playing a key role in electron transport during photosynthesis, lignin formation and cell wall metabolism. However, when Cu is present at elevated concentrations it can cause toxicity with impacts on the growth, reproduction and survival of aquatic and terrestrial organisms. The biogeochemical cycle of Cu in aquatic and terrestrial environments can be influenced by numerous biological (e.g. root rhizosphere) and physicochemical (e.g. redox, pH) properties. A better understanding of Cu biogeochemical cycling is required to ensure optimal Cu supply to organisms. As such, there is an increasing need for the development of new analytical tools that can be used in complex environmental systems to examine this. This thesis investigates the use of Cu stable isotopes to yield new information on the behaviour of Cu in soil-plant systems. Copper has two stable isotopes, ⁶³Cu and ⁶⁵Cu, and the different partitioning of these two isotopes between Cu pools (known as fractionation) can provide information on the reactions and mechanisms involved in Cu transport from one pool to another. Stable isotope data from plant growth studies were coupled with solid phase speciation and dialysis solution speciation to yield a better understanding of the isotopic signature of bioavailable Cu and the mechanisms by which Cu is absorbed into, and translocated throughout, plants. The effect of Cu complexation by soluble organic matter was quantified to assess whether the isotopic signature of bioavailable ‘free’ Cu differed to that of the total soil solution Cu. This is important as fractionation between soil solution and plants cannot be accurately measured if the isotopic signature of the available pool of Cu is not accurately known. Copper isotope fractionation was examined in solutions of both synthetic organic ligands and Suwannee River fulvic acid (SRFA) using Donnan dialysis to separate the free and complexed Cu pools. The results showed that Cu contained within the organic complex was enriched in the heavy isotope, with the magnitude of fractionation proportional to the strength of the Cu-ligand bond. These results highlight the importance of determining the isotopic signature of the bioavailable ‘free’ Cu when looking at plant uptake mechanisms, as the isotopic signature of the total solution Cu is different to that of free Cu if Cu is partly complexed with organic ligands, as is usually the case in environmental samples. When using Cu isotope fractionation to assess root absorption mechanisms, it is important to consider the contribution of Cu adsorbed to the cell wall. In order to assess the isotope fractionation involved with Cu adsorption onto plant cell walls, four-week old plants and seedlings of Fe-acquisition Strategy I and Strategy II species were exposed to various concentrations of Cu for short periods of time. Adsorbed Cu was then desorbed from four-week old tomato and oat plants, using 3 different desorption techniques to determine which root washing technique quantitatively released adsorbed Cu while not extracting symplastic Cu. The results showed that the root wash procedure based on cation exchange using La and Ca was the best extractant to exclusively target the apoplastic Cu, while EDTA and HCl extractants showed signs of symplastic Cu removal. No significant isotope fractionation was found during adsorption onto the surface of monocotyledonous (monocot, Strategy II) plant roots, but adsorption onto the surface of dicotyledonous (dicot, Strategy II) plant roots yielded Cu isotope fractionations on the order of that seen during Cu complexation with fulvic acid (Δ⁶⁵Cu root-solution = ca. 0.2‰). The results suggested that a difference in the type and/or strength of Cu binding sites on the cell walls exists for monocot and dicot species, and highlight the importance of root washing when assessing isotope fractionation due to root absorption. The fractionation of Cu stable isotopes during uptake into plant roots and translocation to shoots was used to gain new information on Cu acquisition mechanisms by plants. Copper isotope fractionation values were coupled with intact tissue speciation techniques (X-ray absorption spectroscopy, XAS) to examine the uptake, translocation and speciation of Cu in a dicot (tomato) and monocot (oat) plant species. Plants were grown in solution culture where Cu was maintained as free Cu by regular replacement of the nutrient solution, so that complexation-induced isotope fractionation in the solution did not complicate the determination of fractionation due to plant uptake. The iron (Fe) conditions were varied to test whether the stimulation of Fe acquiring mechanisms can affect Cu uptake in plants. The results showed that isotopically light Cu was preferentially incorporated into tomatoes (Δ⁶⁵Cu whole plant-solution= ca. -1‰), whereas oats showed minimal isotopic fractionation, with no effect on isotope fractionation with changing Fe conditions in either species. The presence of isotopically light Cu in tomatoes was attributed to a reductive uptake mechanism. The heavier isotope was preferentially translocated to shoots in tomato, while oat plants showed no significant fractionation during translocation. The translocation fractionation observed for tomatoes was suggested to be linked to an oxidation and organic complexation with nicotianamine, as both of oxidation and complexation processes lead to heavy isotope enrichment. The majority of Cu in roots and leaves of both speciesexisted as sulphur-coordinated Cu(I) species indicating glutathione/cysteine-rich proteins. The lack of isotopic discrimination in oat plants suggests that Cu uptake and translocation was not redox-selective and different translocation pathways exist between monocot and dicot plant species. The results presented in this thesis provide significant new information on the behaviour of Cu isotopes in soil-plant systems. For the first time it has been shown that Cu complexation with soluble organic matter and adsorption onto plant roots can cause notable isotopic fractionation, with the organic complex or root surface enriched in the heavy isotope. The most significant findings of this research relate to differences observed between Cu uptake and translocation mechanisms between monocot and dicot species, elucidated from Cu isotope fractionations and XAS analysis. These data open the door to future research into Cu source tracing using isotopic signatures, further investigations into Cu behaviour in soil solutions in-situ, as well as field studies looking at Cu uptake and translocation mechanisms in plants grown in soil environments.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Agriculture, Food and Wine, 2014.

Abstract The recent discovery of large Cenozoic porphyry copper deposits in the Tibetan Plateau has revealed atypical features. Their formation all postdate the India-Asia collision at 55 ± 10 Ma, and therefore they are not affiliated with normal arc magmatism. Three major nonarc porphyry copper belts or provinces in Tibet comprise the Gangdese porphyry Cu-Mo belt (>45 Mt Cu, 1.79 Mt Mo), the Yulong porphyry Cu-Mo belt (8.75 Mt Cu,1.04 Mt Mo), and the western Yunnan porphyry Cu-Mo-Au polymetallic province (~1 Mt Cu, ~1 Mt Mo, and 310 t Au). Alkaline volcanic rocks (lamprophyres, shoshonites, and potassic-ultrapotassic volcanic rocks) are common in these metallogenic belts and provinces, but the temporal, spatial, and genetic relationship between this magmatism and deposit formation remains enigmatic. There are two episodes of porphyry mineralization in the Tibetan Plateau, 45 to 35 and 22 to 11 Ma, and alkaline volcanic rocks are both contemporaneous with and spatially close to porphyry mineralization. Evolved Nd-Hf isotope compositions, and high Mg#, Cr, and Ni contents of Tibetan alkaline volcanic rocks suggest that they are derived from phlogopite-bearing lithospheric mantle, whereas the adakitic property and hybrid geochemical and isotopic features of the high Sr/Y granitoids suggest they are derived from partial melting of lower crust by mantle-derived alkaline mafic melt, with subsequent mixing. The mantle-derived alkaline magmas: (1) triggered water-flux melting of the thickened lower crust and generation of fertile high Sr/Y magmas with high water contents; (2) that dominate the source of ore-related magmas are more Au rich; (3) have variable oxidation states and some can oxidize residual sulfide in the lower crust to release Cu and Au for porphyry deposit formation; other lower crustal melts became oxidized via amphibole and/or garnet fractionation; and (4) provide higher S and Cl contents that are essential volatiles for deposit formation. We conclude that mantle-derived alkaline melts are vital to form porphyry deposits in nonarc settings, thus explaining the close spatial and temporal association of alkaline volcanic rocks and porphyry deposits in Cenozoic Tibet.