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Trace Elements (trace + element)
Kinds of Trace Elements Terms modified by Trace Elements Selected AbstractsDETECTING CHANGES OF CELTIC GOLD SOURCES THROUGH THE APPLICATION OF TRACE ELEMENT AND Pb ISOTOPE LASER ABLATION ANALYSIS OF CELTIC GOLD COINS*ARCHAEOMETRY, Issue 4 2009C. BENDALL This project follows on from an initial study of Celtic gold coins from the Middle Rhine/Moselle region, which was based on material found at the Martberg, a Late Iron Age/Roman sanctuary and settlement (River Moselle, western Germany; Bendall 2003). The earlier work was expanded to encompass over 100 examples of various other regional Celtic gold coinages from the collection of the Römisch-Germanisches Zentralmuseum, Mainz. The alloy (Au,Ag,Cu) and trace element compositions (in particular Ni, Sb and Pt) were determined by EPMA and LA,ICP,MS, respectively, and their Pb isotope signatures were measured by LA,MC,ICP,MS. Of the 28 trace elements measured, only Ni, Sb and Pt were found to show meaningful variations and so only they are presented here. In particular, differences in the Pt/Au ratios between various groups of earlier coinage (imitations of Philippus and Alexander/Nike staters, Sch. 23 and some early Boian coins) on the one hand, and the majority of the Boian and the southern rainbow cup coinages on the other, indicate a significant difference in the gold sources exploited for these regional coinages. The Pb isotope data confirm previous conclusions that the contribution of gold to the total lead in the Au,Ag,Cu coin alloys can be detected, especially for coins with over 70% gold, and show that possible gold sources include both eastern Mediterranean and Alpine sources. Combining the Pb isotope data with the Pt/Au ratios allows the potential gold sources to be further differentiated. [source] Quantitative Chemical Mapping of Relevant Trace Elements at Biomaterials/Biological Media Interfaces by Ion Beam MethodsADVANCED ENGINEERING MATERIALS, Issue 7 2010Edouard Jallot The definition of biomaterial as proposed by the European Society for Biomaterials in 1986 puts forward the overall importance of the notion of contact between the biomaterial and biological medium (cell, tissue, fluid,,). The underlying concept of biocompatibility makes the interface between biomaterial and biological medium a privileged zone of interest. In this paper, we would like to give an exhaustive view of how ion beams techniques can contribute to a better understanding of such interface taking several examples dealing with bone tissue substitution. After a short presentation of ion beams techniques the paper will focus on PIXE/RBS spectroscopies and will give the basics of these coupled technique. Three examples will then be presented to illustrate the interest of these techniques to study biomaterials/biological interactions. The first example deals with metallic alloys based joint prostheses. The ionic release from the prosthesis and the wear behavior of total knee prostheses will be presented. In the last two examples, bioactive materials will be studied. The common characteristic of bioactive ceramics is the kinetic modification of their surface upon interaction which is ideally monitored by PIXE chemical mapping. The second example will review the benefit of using PIXE/RBS technique to study the effect of doping of bioactive glasses on the very first steps involved in the bioactivity mechanisms like dissolution, ionic release, and biomineralization onto the surface of the glasses. Finally, protein delivery systems based upon mesoporous hydroxyapatites will be studied. Chemical mapping allowing the quantitative determination of protein distribution inside the HAp grains will be presented for the first time. [source] High-Resolution LA-ICP-MS for Accurate Determination of Low Abundances of K, Sc and Other Trace Elements in Geological SamplesGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 1 2010Julia Regnery LA-ICP-MS; haute résolution de masses; matériaux géologiques de référence; verres MPI-DING Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to determine K, Sc, Ti, V, Cr, Mn, Co, Ni and Zn in geological samples. Because the isotopes of these elements and the internal standard element (Ca) often have interferences from molecular ions when determined using quadrupole or sector-field ICP-MS in low mass resolution mode, ion intensities were measured at a high mass resolution of 4000. We investigated dynamic element fractionation, type and abundance of molecular ions using different geological reference materials. Highly resolved mass spectra were especially important for accurate low-abundance measurements. As a result, maximum "critical" concentration limits for each isotope were obtained, where a mass resolution of 4000 was necessary for reliable LA-ICP-MS analysis. To test the LA-ICP-MS technique, different international reference material glasses and powdered rock reference materials were analysed. Rock powders were fused to glass beads using an Ir-strip heater. Nearly all concentration values for the reference materials agreed with the reference values at the 95% confidence level. To demonstrate routine LA-ICP-MS analysis at a mass resolution of 4000, trace element data for Hawaiian basalts are also presented. La technique de spectrométrie de masse couplée à un plasma inductif et associée à un système d'ablation laser (LA-ICP-MS) a été utilisée pour la détermination des concentrations en K, Sc, Ti, V, Cr, Mn, Co, Ni and Zn dans des échantillons géologiques. Parce que les isotopes de ces éléments et l'élément utilisé comme standard interne (Ca) ont souvent des interférences liées à la formation d'ions moléculaires lorsqu'ils sont analysés par les techniques d'ICP-MS quadripolaire ou à secteur magnétique en mode basse résolution de masses, les intensités des ions ont été mesurées en mode haute résolution de masses de 4000. Nous avons étudié le fractionnement dynamique des éléments, le type et l'abondance des ions moléculaires en utilisant différents matériaux géologiques de référence. Les spectres de masse de haute résolution ont été particulièrement importants pour les mesures précises des faibles abondances. En conséquence, les limites maximales de concentration critique pour chaque isotope ont été obtenues, dans les cas où une résolution de masse de 4000 était nécessaire pour obtenir des analyses LA-ICP-MS fiables. Pour tester la technique LA-ICP-MS proposée, différents verres et poudres de matériaux de référence internationaux ont été analysés. Les poudres de roche ont été transformées en billes de verre par fusion dans un four automatique à chauffage par filament d'iridium. Presque toutes les concentrations obtenues pour les matériaux de référence sont en accord avec les valeurs de référence de la littérature à un niveau de confiance de 95%. Pour démontrer que la méthode présentée de LA-ICP-MS à résolution de masses de 4000 peut s'utiliser en routine, nous présentons également des données d'éléments traces de basaltes Hawaïens. [source] Direct Current Plasma Emission Spectrometric Determination of Major, Minor and Trace Elements in Microwave Oven Acid Leachates of Powdered Whole Coal SamplesGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 1 2005Sandro Fadda DCP-AES; échantillons de charbon; four à micro-ondes; éléments facilement ionisables; effets de matrice. Major concentrations of Al2O3, Fe2O3, MgO, CaO, Na2O and K2O, minor levels of TiO2, P2O5 and thirty petrologically, geochemically and environmentally significant trace elements have been determined in microwave oven acid leachates of whole powdered coal samples by direct current plasma-atomic emission spectrometry (DCP-AES). A single sample preparation procedure was suitable for all the determinations with no additional dilution step for major elements solution. Dried samples (0.5 g) were treated in low-pressure PFA digestion vessels with HF/HCl/HNO3/HClO4 acids to quantitatively extract the analytes from the bulk material, while leaving the major part of organic matrix as a residue. The major constituents of geological samples, in particular the easily ionised elements (EIEs) such as alkali and alkaline earths, may complicate the instrumental determinations in DCP-AES because of differential enhancements of elemental emission intensities and stray light interferences. Taking account of these factors, the coal matrix is considered to have very low major oxide totals as compared to many other common geo-environmental and related materials (rocks, sediments, soil, ashes etc.). The sample size employed here, while yielding a relatively concentrated solution to cover a wide range of elemental determinations, provided a sample matrix that significantly diminished interferences for DCP measurements. The need for closely matching the unknowns and calibrators was eliminated except for overall acidity and an excess quantity of caesium for EIE buffering. Calibration of the spectrometer was accomplished by simple aqueous single element solutions as high concentration calibrators in addition to a reagent blank as a low concentration calibrator. Two point working curves were established to allow for the maximum concentrations of each element expected in the unknowns. The precision of determinations under routine conditions as well as the reproducibility of the leaching and precision of instrumental measurements have been evaluated. Relative standard deviations (RSD) were of 1,2% for those elements whose concentrations in solid samples were well above the limits of quantification. Method detection limits in the buffered solutions were also evaluated. To evaluate the accuracy of the microwave oven-DCP method a suite of eight certified coal reference materials of differing rank, were analysed with good agreement with the certified and/or available published data. Results are presented for the uncertified major oxides in the AR series reference materials. Les concentrations en éléments majeurs: Al2O3, Fe2O3, MgO, CaO, Na2O et K2O, en éléments mineurs TiO2, P2O5 et en 30 éléments en trace dont le comportement est important en Pétrologie, en Géochimie et en Environnement, ont été analysées par spectrométrie d'émission atomique à plasma à courant direct (DCP-AES), dans des lessivages acides effectués dans un four à micro-ondes sur des échantillons de charbon mis en poudre. Ce mode préparatoire unique est adaptéà toutes les déterminations sans qu'il soit nécessaire d'effectuer une dilution supplémentaire pour l'analyse des éléments majeurs. Les échantillons préalablement desséchés (0.5 g) sont traités dans les pots de PFA de basse pression, avec un mélange d'acides HF/HCl/HNO3/HClO4, afin d'extraire quantitativement les analytes du matériel géologique, tout en laissant la plus grande part de la matrice organique sous forme résiduelle. Les constituants majeurs de ces échantillons géologiques, en particulier les éléments facilement ionisables (EIEs) tels que les alcalins et les alcalino-terreux, peuvent compliquer l'analyse en DCP-AES à cause des rendements variables des intensités d'émission élémentaires et des interférences de raies de lumière. Mais là dessus, la matrice de charbon se révèle être bien plus pauvre en oxydes majeurs que les autres matériaux géologiques, environnementaux ou de type proche (roches, sédiments, sols, cendres). La taille d'échantillon retenue ici, tout en fournissant une solution relativement concentrée qui permet la détermination de beaucoup d'éléments, fournit une matrice qui diminue significativement les interférences lors de la mesure par DCP-AES. Le besoin d'avoir les solutions d'échantillons et les solutions de calibration avec des matrices très proches est donc éliminé, mis à part pour l'acidité totale et la quantité excessive de Césium pour tamponner les EIE. La calibration du spectromètre est faite avec des solutions mono- élémentaires aqueuses, pour déterminer les points de concentrations élevées et avec le blanc de réactifs pour le point de concentration basse. Les courbes de calibrations sont déterminées avec 2 points, pour autoriser l'analyse de concentrations maximales pour chaque élément dans les échantillons inconnus. La précision des déterminations en conditions de routine ainsi que la reproductibilité de l'opération de lessivage et la précision instrumentale des analyses ont étéévaluées. Les déviations standards relatives (RSD) sont de 1,2% pour tout élément dont les concentrations dans le solide sont au dessus des limites de quantification. Les limites de détection de la méthode dans les solutions tamponnées ont aussi étéévaluées. Enfin, pour évaluer la justesse de cette méthode "micro-ondes - DCP" huit charbons certifiés matériaux de référence de différents types ont été analysés, et sont en bon accord avec les données certifiées ou seulement disponibles publiées. Les données sur un certain nombre d'oxydes d'éléments majeurs actuellement non certifiés sont présentées pour les matériaux de référence AR. [source] Routine Analyses of Trace Elements in Geological Samples using Flow Injection and Low Pressure On-Line Liquid Chromatography Coupled to ICP-MS: A Study of Geochemical Reference Materials BR, DR-N, UB-N, AN-G and GHGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2-3 2001Jean Carignan géostandards; éléments traces; flow injection; chromatographie liquide; ICP-MS We describe analytical procedures for trace element determinations developed at the CNRS Service d'Analyse des Roches et des Minéraux (SARM) and report results obtained for five geochemical reference materials: basalt BR, diorite DR-N, serpentinite UB-N, anorthosite AN-G and granite GH. Results for rare earth elements, U and Th are also reported for other reference materials including dunite DTS-1, peridotite PCC-1 and basalt BIR-1. All rocks were decomposed using alkali fusion. Analyses were done by flow injection ICP-MS and by on-line low pressure liquid chromatography (LC)-ICP-MS for samples containing very low REE, U and Th concentrations. This latter method yielded limits of determination much lower than data by direct introduction and eliminated possible isobaric interference on these elements. Although results agree with most of the working values, when available, results for some elements differed slightly from the recommended concentrations. In these cases, we propose new values for Co, Y and Zn in basalt BR, Zr in diorite DR-N, Sr and U in granite GH, and Ga and Y in anorthosite AN-G. Furthermore, although the Sb concentration measured in AN-G was very close to our limit of determination, our value (0.3 ± 0.1 ,g g,1) is much lower than the reported working value of 1.4 ± 0.2 ,g g,1. These new values would need to be confirmed by a new inter-laboratory programme to further characterise these reference materials. Results obtained for REE, Th and U concentrations using the on-line low pressure LC-ICP-MS yielded good limits of determination (ng g,1to sub-ng g,1for rocks and ng l,1to sub-ng l,1for natural waters) and accurate results. The efficiency of the matrix separation allowed accurate measurements of Eu without the need to correct the BaO isobaric interference for samples having Ba/Eu ratios as high as 27700. For REE concentrations in PCC-1 and DTS-1, differences with values reported in the literature are interpreted as resulting from possible heterogeneity of the reference materials. Thorium and U values are proposed for these two samples, as well as for AN-G and UB-N. Nous rapportons les procédures d'analyse pour les éléments traces développées au Service d'Analyse des Roches et des Minéraux (SARM) du CNRS et les résultats obtenus pour 5 géostandards: le basalte BR, la diorite DR-N, la serpentinite UB-N, l'anorthosite AN-G et le granite GH. Des résultats obtenus pour les Terres Rares (REE), l'uranium et le thorium sont aussi rapportés pour d'autres matériaux de référence tels que la dunite DTS-1, la péridotite PCC-1 et le basalte BIR-1. Les roches ont été décomposées par fusion alcaline. Les analyses ont été faites par Flow Injection ICP-MS et par chromatographie liquide basse pression en ligne sur un ICP-MS pour les très faibles teneurs en REE, U et Th. Cette dernière méthode permet d'avoir une meilleure limite de détermination que celle par introduction directe et d'éliminer certaines interférences isobariques sur ces éléments. Bien que, dans la majorité des cas, nous ayons mesuré les valeurs de référence telles que rapportées dans la littérature, certaines concentrations mesurées diffèrent légèrement des valeurs recommandées. Ainsi, nous proposons de nouvelles valeurs de Co, Y et Zn pour le basalte BR, de Zr pour la diorite DR-N, de Sr et U pour le granite GH et de Ga et Y pour l'anorthosite AN-G. De plus, bien que la concentration en Sb mesurée pour AN-G soit très proche de notre limite de détermination, notre valeur (0.3 ± 0.1 ,g g,1) est bien inférieure à celle rapportée dans la littérature (1.4 ± 0.2 ,g g,1). Ces nouvelles valeurs devraient être confirmées par une nouvelle campagne de caractérisation inter laboratoire pour ces géostandards. Les résultats obtenus pour les REE, U et Th par chromatographie liquide basse pression en ligne sur un ICP-MS sont justes et livrent des limites de détermination faibles au niveau du ng g,1à sub-ng g,1pour les roches et ng l,1à sub-ng l,1pour les eaux naturelles. La séparation de la matrice est efficace et permet une mesure juste de Eu sans correction d'interférence générée par l'oxyde de Ba, et ce même pour des échantillons possédant des rapports Ba/Eu très élevés, de l'ordre de 27700. Les concentrations en REE mesurées pour les échantillons PCC-1 et DTS-1 peuvent être significativement différentes de celle rapportées dans la littérature, probablement à cause d'une hétérogénéité de ces échantillons. Des valeurs de concentrations en U et Th sont proposées pour ces deux échantillons ainsi que pour AN-G et UB-N. [source] Neutron Activation Analysis Applied to the Determination of Heavy Metals and Other Trace Elements in Sediments from Sepetiba Bay (RJ), BrazilGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2-3 2001Fàbio Pellegatti analyse par activation neutronique; métaux lourds; éléments en traces; sédiments marins In this work, instrumental neutron activation analysis (INAA) was applied to the determination of the elements As, Ba, Br, Ce, Co, Cr, Cs, Eu, Fe, Hf, La, Lu, Nd, Rb, Sc, Sm, Ta, Tb, Th, U, Yb, Zn in twenty eight bottom sediment samples from Sepetiba Bay, Rio de Janeiro, Brazil. With the concentration data obtained, contour maps were prepared, by using Kriging method, to show the spatial distribution of the studied elements in the Bay. The elements Co, Cr, Cs, Fe, Sc, Ta and Zn showed similar behaviour in the sediments, with higher concentrations along the northern coast of the bay, where the fluvial water inputs are concentrated. The distribution of U, rare earth elements and Ba in the Bay indicates that these elements are not deposited as contaminants. Dans ce travail, les éléments suivants, As, Ba, Br, Ce, Co, Cr, Cs, Eu, Fe, Hf, La Lu, Nd, Rb, Sc, Sm, Ta, Tb, Th, U, Yb et Zn ont été analysés par activation neutronique instrumentale dans vingt huit sédiments de fond de la baie de Sepetiba, Rio de Janeiro, Brésil. Par krigeage et à partir des concentrations obtenues, nous avons établi des cartes de la répartition spatiale des éléments étudiés dans la baie. Co, Cr, Cs, Fe, Sc, Ta et Zn ont des comportements similaires dans les sédiments, avec des concentrations plus importantes le long de la côte nord de la baie, oú les apports en eau fluviale sont concentrés. La distribution en U, Terres Rares et Ba indique que ces éléments ne sont pas déposés comme polluants dans la baie. [source] Regulation of Mineral and Trace Elements in Human Milk: Exogenous and Endogenous FactorsNUTRITION REVIEWS, Issue 8 2000Bo Lönnerdal Ph.D. Breast-fed infants are dependent on an adequate supply of minerals and trace elements for normal growth and development. For most of these elements, the mammary gland appears to have developed mechanisms to regulate their concentrations, even when the maternal diet varies considerably or maternal conditions are affected by different challenges. For some elements, however, there appears to be little or no such regulation. Increased knowledge about these mechanisms, or their absence, and to what extent they may compensate for adverse maternal conditions, including poor nutrition, will help identify infants and women at risk for deficiencies of these nutrients. [source] Rare Earth, Major and Trace Elements in the Kunimiyama Ferromanganese Deposit in the Northern Chichibu Belt, Central Shikoku, JapanRESOURCE GEOLOGY, Issue 4 2005Yasuhiro Kato Abstract. Rare earth, major and trace element geochemistry is reported for the Kunimiyama stratiform ferromanganese deposit in the Northern Chichibu Belt, central Shikoku, Japan. The deposit immediately overlies greenstones of mid-ocean ridge basalt (MORB) origin and underlies red chert. The ferromanganese ores exhibit remarkable enrichments in Fe, Mn, P, V, Co, Ni, Zn, Y and rare earth elements (excepting Ce) relative to continental crustal abundance. These enriched elements/ Fe ratios and Post-Archean Average Australian Shale-normalized REE patterns of the ferromanganese ores are generally analogous to those of modern hydrothermal ferromanganese plume fall-out precipitates deposited on MOR flanks. However in more detail, Mn and Ti enrichments in the ferromanganese ores are more striking than the modern counterpart, suggesting a significant contribution of hydrogenetic component in the Kunimiyama ores. Our results are consistent with the interpretation that the Kunimiyama ores were umber deposits that primarily formed by hydrothermal plume fall-out precipitation in the Panthalassa Ocean during the Early Permian and then accreted onto the proto-Japanese island arc during the Middle Jurassic. The presence of strong negative Ce anomaly in the Kunimiyama ores may indicate that the Early Permian Panthalassa seawater had a more striking negative Ce anomaly due to a more oxidizing oceanic condition than today. [source] Trace Elements as Contaminants and Nutrients: Consequences in Ecosystems and Human Health.Edited by M.,N.,V.CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 7 2009Prasad Wiley, 2008. 778,pp., hardcover, US$,175.00,ISBN 978-0-470-18095-2 [source] Speleothem preservation and diagenesis in South African hominin sites implications for paleoenvironments and geochronologyGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 5 2009Philip J. Hopley Plio-Pleistocene speleothems from australopithecine-bearing caves of South Africa have the potential to yield paleoenvironmental and geochronological information using isotope geochemistry. Prior to such studies it is important to assess the preservation of geochemical signals within the calcitic and aragonitic speleothems, given the tendency of aragonitic speleothems to recrystallize to calcite. This study documents the geochemical suitability of speleothems from the principal hominin-bearing deposits of South Africa. We use petrography, together with stable isotope and trace element analysis, to identify the occurrence of primary aragonite, primary calcite, and secondary calcite. This study highlights the presence of diagenetic alteration at many of the sites, often observed as interbedded primary and secondary fabrics. Trace element and stable isotopic values distinguish primary calcite from secondary calcite and offer insights into geochemical aspects of the past cave environment. ,13C values of the primary and secondary calcites range from +6 to ,9, and ,18O values range from ,4 to ,6,. The data are thus typical of meteoric calcites with highly variable ,13C and relatively invariant ,18O. High carbon isotope values in these deposits are associated with the effects of recrystallization and rapid outgassing of CO2 during precipitation. Mg/Ca and Sr/Ca ratios differ between primary and secondary calcite speleothems, aiding their identification. Carbon and oxygen isotope values in primary calcite reflect the proportion of C3 and C4 vegetation in the local environment and the oxygen isotope composition of rainfall. Primary calcite speleothems preserve the pristine geochemical signals vital for ongoing paleoenvironmental and geochronological research. © 2009 Wiley Periodicals, Inc. [source] Otolith chemistry of prey fish consumed by a fish predator: does digestion hinder Russian doll techniques?JOURNAL OF FISH BIOLOGY, Issue 10 2009Q. E. Phelps The effect of digestion by a predatory fish (largemouth bass Micropterus salmoides) on stable isotopic (,13C and ,18O) and trace elemental (Sr:Ca and Ba:Ca) compositions of prey fish (bluegill Lepomis macrochirus) otoliths was investigated in a laboratory experiment. Trace element and stable-isotopic signatures of L. macrochirus otoliths were not significantly altered for up to 16 h after L. macrochirus were consumed by M. salmoides. Prey fish otoliths recovered from predator digesta can retain environmental stable isotopic and trace elemental signatures, suggesting that determination of environmental history for prey fishes by stable-isotope and trace-element analysis of otoliths recovered from stomachs of piscivorous fishes will be feasible. [source] Annual trace element cycles in calcite,aragonite speleothems: evidence of drought in the western Mediterranean 1200,1100,yr,BP,JOURNAL OF QUATERNARY SCIENCE, Issue 5 2005Emily A. McMillan Abstract Each of two calcitic stalagmites from Grotte de Clamouse, Herault, southern France, displays a discrete aragonite layer dated at around 1100,yr,BP. The layer of fanning aragonite ray crystals is immediately preceded by calcite with Mg and Sr compositions that are uniquely high for the past 3,kyr. Trace element compositions close to the boundary between original aragonite and calcite are consistent with quasi-equilibrium partitioning of trace elements between the phases. Study of modern dripwaters demonstrates that pronounced covariation of Mg/Ca and Sr/Ca ratios in dripwater occurs owing to large amounts of calcite precipitation upflow of the drips that fed the stalagmites. Trace element to Ca ratios are enhanced during seasonally dry periods. Ion microprobe data demonstrate a pronounced covariation of trace elements, including Mg and Sr in calcite, and Sr, U and Ba in aragonite. The mean peak spacing is close to the long-term mean of annual growth rates determined by differences in U-series ages and so the trace element peaks are interpreted as annual. The trace element chemistry of the stalagmites on annual to inter-annual scales thus directly reflects the amounts of prior calcite precipitation, interpreted as an index of aridity. The longer-term context is a multi-decadal period of aridity (1200,1100,yr,BP) possibly correlated with an analogous episode in Central America. The arid period culminated in the nucleation of aragonite, but within a decade was followed by a return to precursor conditions. Copyright © 2005 John Wiley & Sons, Ltd. [source] Essential elements and contaminants in tissues of commercial pelagic fish from the Eastern Mediterranean SeaJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 9 2009Beyza Ersoy Abstract BACKGROUND: It is important to determine the concentrations of essential and non-essential metals in fish for human health. The essential elements and contaminants (Pb and Cd) were determined seasonally in the muscle and liver of some pelagic fish species round herring (Etrumeus teres), chub mackerel (Scomber japonicus), golden grey mullet (Liza aurata) and Mediterranean horse mackerel (Trachurus mediterraneus) from the Iskenderun Bay, Eastern Mediterranean Sea. RESULTS: The Na, K, Ca and Mg were the most abundant elements in muscle and liver tissues. The Na, K, Ca and Mg concentrations in fish tissues were between 51.7 and 3426 mg kg,1. Muscle accumulated the lowest levels of elements. Trace element and contaminant levels in muscle were highest in spring and summer. The Cu, Zn and Cr concentrations were highest in summer. The Ni, Mn and Fe concentrations were highest in spring. The maximum Pb concentrations in the muscle and liver of fish species was 0.39 and 0.80 mg kg,1 in autumn. The maximum Cd concentration in the muscle of fish was 0.27 mg kg,1 in spring and the maximum Cd concentration in the liver was 0.78 mg kg,1 in summer. CONCLUSION: The Cr, Pb, Cd, Cu and Zn levels in muscle were found to be lower than permissible limits reported by various authorities. Estimated weekly and daily intake for Pb and Cd by consumption of fish muscle were far below the PTWI and PTDI values established by FAO/WHO. Copyright © 2009 Society of Chemical Industry [source] Serum trace element levels in COPD patient: The relation between trace element supplementation and period of mechanical ventilation in a randomized controlled trialRESPIROLOGY, Issue 8 2009May EL-ATTAR ABSTRACT Background and objective: Many trace elements play important roles in activating or inhibiting enzymatic reactions, by competing with other elements and metalloproteins for binding sites, by affecting the permeability of cell membranes and by other mechanisms. They play important roles in the oxidant/antioxidant balance. As such, trace elements are thought to be involved directly or indirectly in the pathogenesis of several diseases. The aim of the present study is to investigate the effect trace elements (Se, Mn and Zn) intravenously administered on the period the COPD patients spend on mechanical ventilation. Methods: In a randomized double-blinded controlled trial a set of 120 subjects (40 normal volunteers and 80 COPD) were recruited. Serum concentration levels of Se, Mn and Zn were determined for all enrolled subjects with Inductively Coupled Plasma spectroscopy. COPD patients received intravenous supplementation of the above trace elements and the period the patients spent on mechanical ventilation was determined. Results: There was a significant reduction (P = 0.013) in the period the patients with COPD spent on the mechanical ventilation when received intravenous supplementation (9.4 ± 7.3 days) compared with the COPD patients who received placebo (17.8 ± 7.6 days). Conclusions: Trace element (Se, Mn and Zn) status is altered in critically ill patients with COPD. The supplementation achieved a reduction in the period those patients spent on the mechanical ventilation. A larger multi-centre trial is required to confirm this preventive effect and to explore its applicability to other critical care conditions. [source] Trace metals, stable isotope ratios, and trophic relations in seabirds from the North Pacific OceanENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2005John E. Elliott Abstract Trace elements including mercury, cadmium, selenium, and stable nitrogen isotope ratios (,15N) were measured in tissues of Pacific seabirds. Two species of albatross (Diomedea immutabilis, Diomedea nigripes), four species of shearwaters (Puffinus bulleri, Puffinus carneipes, Puffinus griseus, Puffinus tenuirostris), northern fulmar (Fulmarus glacialis), and horned puffin (Fratercula corniculata) were collected opportunistically by an experimental fishery in the North Pacific Ocean. Two species each of petrels (Oceanodroma leucorhoa, Oceanodroma furcata) and auklets (Ptychoramphus aleuticus, Cerorhinca monocerata) were collected at breeding colonies on the north coast of British Columbia, Canada. Concentrations of toxic trace metals varied considerably among the pelagic nonbreeders; highest concentrations consistently were in D. nigripes (e.g., Hg), 70-fold greater than F. corniculata (e.g., Cd), eightfold greater than P. tenuirostris (e.g., Se), and fourfold greater than F. corniculata. Most essential trace elements varied little among species, consistent with physiological regulation. Values for ,15N correlated positively with hepatic Se (r = 0.771, p = 0.025) and negatively with Co (r = 0.817, p = 0.013). Among the four breeding species, there were significant positive associations for ,15N in muscle and hepatic Se (r = 0.822, p = 0.002), Hg (r = 0.744, p = 0.0001), and Cd (r = 0.589, p = 0.003). Differences in time scales integrated by ,15N versus trace metals in tissues probably reduced the apparent associations between trace-metal exposure and diet. [source] Characterization of major and trace elements in sclerotium grainsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2007M. Watanabe Summary Sclerotium grains in soil contain humus-metal complexes that are probably produced from fungal metabolites. The characterization of major elements in sclerotium grains collected from volcanic ash soils in Mt Myoko was examined by X-ray photoelectron spectroscopy, FT-IR spectrometry and CHN analysis, and the concentration of trace elements was determined by PIXE (particle induced X-ray emission spectrometer) analysis. The content of major elements, C, H, N, O and Al, was approximately 47.6, 3.32, 0.78, 30.2 and 1.4% by mass, respectively. Trace elements such as Ti, Cr, Mn, Cu, Zn, Br and Pb were detected in the grains at concentrations between 10 and 100 ,g g,1. Functional carbon groups for the whole grain were characterized by the dominance of O-alkyl C associated with aromatic C. The comparison between the surface and subsurface (matrix) of the grain showed that the concentrations of O, C and N were relatively greater on the surface of sclerotium grains than in the matrix. The proportion of carbon having C,O, C=O, and O,C=O bonds, O and N showed a tendency to decrease from the surface towards the matrix. The proportion of C assigned as C,C and/or C,H bonds had a tendency to increase towards the matrix associated with Al. [source] Metals in human placenta: focus on the effects of cadmium on steroid hormones and leptin,JOURNAL OF APPLIED TOXICOLOGY, Issue 3 2010Sandra Stasenko Abstract Cadmium and other metallic ions can act as metalloestrogens and endocrine disruptors of reproductive tissues and fetal development in mammals, including humans. The detrimental effects occur with respect to the synthesis of both steroid and polypeptide hormones in the placenta. Leptin is produced by the trophoblast and may regulate fetal organogenesis and development. In human term placentas, concentrations of toxic metals and their effects on steroidogenesis were assessed in healthy parturients (109 non-smokers and 99 smokers) in relation to tobacco smoking. Trace elements (cadmium, lead, iron, zinc and copper) were analyzed in placentas using atomic absorption spectroscopy, and steroid hormones (progesterone and estradiol) were assayed in placental samples by an enzyme-immunometric method. Cadmium concentrations were doubled in placentas of smokers as compared with non-smokers, and placental lead and zinc concentrations increased significantly. Placental concentrations of iron, copper, progesterone and estradiol did not differ. In addition, human trophoblast cells were co-cultured with 0, 5, 10 or 20,,µm CdCl2 for 96,,h and leptin mRNA assessed by quantitative polymerase chain reaction. Leptin mRNA declined dose-responsively as a result of CdCl2 exposure. Collectively, the results confirm that human placental tissue offers a unique opportunity to biomonitor cadmium exposure in both the maternal and the internal fetal environments. In addition, the results strongly suggest that cadmium may cause a decline in placental leptin synthesis, as we have previously shown for placental progesterone production. This may constitute further evidence of the endocrine-disrupting effects of cadmium, as a constituent of tobacco smoke, on reproduction in women. Copyright © 2009 John Wiley & Sons, Ltd. [source] Trace elements in edible tissues of three shrimp species (Penaeus semisulcatus, Parapenaeus longirostris and Paleomon serratus)JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 2 2008Nalan Gokoglu Abstract Accumulation levels of trace elements in edible tissues of three shrimp species (Penaeus semisulcatus, Parapenaeus longirostris and Paleomon serratus) from the Gulf of Antalya, Turkey were investigated. Copper (Cu), cadmium (Cd), zinc (Zn), iron (Fe) and manganese (Mn) concentrations were determined by atomic absorption spectrophotometry. The lowest Cu (1.33 mg kg,1) and Cd (0.23 mg kg,1) and highest Mn (1.52 mg kg,1) concentrations were found in P. longirostris, the lowest Zn (6.25 mg kg,1), Fe (1.84 mg kg,1) and Mn (0.25 mg kg,1) concentrations in P. serratus and the highest Cu (6.19 mg kg,1), Cd (2.36 mg kg,1), Zn (30.84 mg kg,1) and Fe (33.89 mg kg,1) concentrations in P. semisulcatus. The Cd levels detected in P. semisulcatus and P. serratus were above legislative limits. Our results show that there were significant differences in trace element concentrations among the three shrimp species. The highest levels of the five trace elements investigated, with the exception of Mn, were found in edible tissue of P. semisulcatus. Copyright © 2007 Society of Chemical Industry [source] Geochemical Signatures of Early Paleogene Source Rocks in the Sanshui Basin, South ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2010Chunlian LIU Abstract: The Honggang member of the early Paleogene Buxin Formation is the main source rock in the Sanshui Basin, characterized by organic-rich black shales with the cyclic recurrence of organic-poor sediments. The geochemical characteristics of the Honggang member have been documented to determine the organic matter types and depositional environments in this paper. The organic matter of the black shales mainly consists of a mixture of land plant-derived and phytoplankton-derived organic matter. Total organic carbon content (TOC)-sulfur-iron (Fe) relationships suggest that the organic-rich black shales were deposited under dysoxic-to-euxinic water conditions. The time that iron minerals remained in contact with H2S in anoxic waters possibly influenced the formation of syngenetic pyrite, and organic carbon controlled the formation of diagenetic pyrite. Organic-poor intervals usually show pyrite sulfur enrichment and higher degree of pyritization values relative to low organic carbon contents. This resulted from HS, diffusing downward from overlying organic-rich sediments and formed Fe sulfides through reactions with sufficient Fe. Trace elements generally exhibit low concentrations and little TOC dependence, suggesting some degree of depletion in these elements in the early Paleogene sediments of the Sanshui Basin. This probably resulted from cyclic recurrences of oxic benthic conditions, which promoted the remobilization of trace elements and caused the low concentration of trace elements. [source] Analytical SuperSTEM for extraterrestrial materials researchMETEORITICS & PLANETARY SCIENCE, Issue 10 2009John P. Bradley The improved technical capabilities enable analyses previously not possible. Mineral structures can be directly imaged and analyzed with single-atomic-column resolution, liquids, and implanted gases can be detected, and UV-VIS optical properties can be measured. Detection limits for minor/trace elements in thin (<100 nm thick) specimens are improved such that quantitative measurements of some extend to the sub-500 ppm level. Electron energy-loss spectroscopy (EELS) can be carried out with 0.10,0.20 eV energy resolution and atomic-scale spatial resolution such that variations in oxidation state from one atomic column to another can be detected. Petrographic mapping is extended down to the atomic scale using energy-dispersive X-ray spectroscopy (EDS) and energy-filtered transmission electron microscopy (EFTEM) imaging. Technical capabilities and examples of the applications of SuperSTEM to extraterrestrial materials are presented, including the UV spectral properties and organic carbon K-edge fine structure of carbonaceous matter in interplanetary dust particles (IDPs), X-ray elemental maps showing the nanometer-scale distribution of carbon within GEMS (glass with embedded metal and sulfides), the first detection and quantification of trace Ti in GEMS using EDS, and detection of molecular H2O in vesicles and implanted H2 and He in irradiated mineral and glass grains. [source] Trace element distributions in soils developed in loess deposits from northern FranceEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2006T. Sterckeman Summary A pedo-geochemical survey was carried out in the Nord-Pas de Calais region (France) on soils developed in loess deposits. Total concentrations of Al, Fe and 18 trace elements, as well as common soil characteristics, were determined in samples from 52 surface and 97 deep horizons developed in these loess deposits. The Pb isotopic composition was determined in two sola. The composition of deep horizons, compared with that of the upper continental crust, with that of horizons developed from 21 other sedimentary rocks from the region and with that of loess from various parts of the world, confirms that loess from the Nord-Pas de Calais region derives from multi-recycled and well-mixed ancient sedimentary rocks. Correlation analysis shows that least mobile (i.e. ionic potential (Z/r) is between 3 and 7) geogenic elements (Bi, Co, Cr, Cu, In, Ni, Pb, Sn, Tl, V, Zn) are associated with the fraction <2 µm (which we define as ,lutum'). More mobile elements (As, Cd, Hg, Mn, Mo, Sb, Se) are less associated with this fraction. Cadmium is particularly linked to Mn. The distribution of [trace element]/([Al] or [Fe]) in the French loess gives the background content for soils developed from most sedimentary materials in northwestern Europe. Topsoils are enriched with all the trace elements examined, except Co, Cr and Ni. Enrichments with Cd, Cu, Mn and Zn are greater in cultivated soils than in forest soils. Enrichments with Pb and with Cu, Hg, Mo, Sb, Se and Sn are mainly due to human contamination through atmospheric fallout. Organic matter seems to act as a sink for all the exogenous trace elements. [source] Interaction of copper and zinc with allophane and organic matter in the B horizon of an AndosolEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2003C. Latrille Summary Andosols developed on basaltic material are naturally rich in metals. Organic matter and allophane, the key colloids of these soils, have a strong affinity for trace metals, but are intimately mixed so that speciation of trace metal is difficult to determine. We used three complementary approaches, namely physical fractionation, chemical extraction and potentiometric measurement, to distinguish them. Physical particle-size separations and chemical selective dissolution of allophanes and organic matter were combined to demonstrate relations between the occurrence of colloids and contents of Cu and Zn in an andic B horizon. About 22% of total soil Cu and 7% of total soil Zn were present in the < 5-,m fraction, associated with organic or amorphous mineral constituents. To support this association further, the affinity of soil colloids for Cu and Zn in a mimicked system was demonstrated. An Al-rich allophane was synthesized, and a portion of the organic matter was extracted from the clay fraction, and their reactivities towards Cu2+ or Zn2+ were studied by potentiometry. The two metallic cations displayed specific affinity towards allophane or soluble organic matter. Furthermore, the behaviour of copper and zinc in the ternary system, allophane + soluble organic matter + trace element, revealed a synergy in the surface complexation. The use of these three speciation approaches highlighted the linkage between metals and constituents, and showed how important the colloidal constituents are in the behaviour of Cu and Zn in Andosols. [source] Selenium affects biosilica formation in the demosponge Suberites domunculaFEBS JOURNAL, Issue 15 2005Effect on gene expression, spicule formation Selenium is a trace element found in freshwater and the marine environment. We show that it plays a major role in spicule formation in the demosponge Suberites domuncula. If added to primmorphs, an in vitro sponge cell culture system, it stimulates the formation of siliceous spicules. Using differential display of transcripts, we demonstrate that, after a 72-h exposure of primmorphs to selenium, two genes are up-regulated; one codes for selenoprotein M and the other for a novel spicule-associated protein. The deduced protein sequence of selenoprotein M (14 kDa) shows characteristic features of metazoan selenoproteins. The spicule-associated protein (26 kDa) comprises six characteristic repeats of 20 amino acids, composed of 10 distinct hydrophobic regions (, 9 amino acids in length). Recombinant proteins were prepared, and antibodies were raised against these two proteins. Both were found to stain the central axial filament, which comprises the silicatein, as well as the surface of the spicules. In the presence of selenium, only the genes for selenoprotein M and spicule-associated protein are up-regulated, whereas the expression of the silicatein gene remains unchanged. Finally we show that, in the presence of selenium, larger silica aggregates are formed. We conclude that selenium has a stimulatory effect on the formation of siliceous spicules in sponges, and it may be involved in the enzymatic synthesis of biosilica components. [source] Accurate U-Pb Age and Trace Element Determinations of Zircon by Laser Ablation-Inductively Coupled Plasma-Mass SpectrometryGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 3 2004Honglin Yuan LA-ICP-MS; laser excimer; zircon; géochronologie; éléments en trace Various zircons of Proterozoic to Oligocene ages (1060-31 Ma) were analysed by laser ablation-inductively coupled plasma-mass spectrometry. Calibration was performed using Harvard reference zircon 91500 or Australian National University reference zircon TEMORA 1 as external calibrant. The results agree with those obtained by SIMS within 2s error. Twenty-four trace and rare earth elements (P, Ti, Cr, Y, Nb, fourteen REE, Hf, Ta, Pb, Th and U) were analysed on four fragments of zircon 91500. NIST SRM 610 was used as the reference material and 29Si was used as internal calibrant. Based on determinations of four fragments, this zircon shows significant intra-and inter-fragment variations in the range from 10% to 85% on a scale of 120 ,m, with the variation of REE concentrations up to 38.7%, although the chondrite-normalised REE distributions are very similar. In contrast, the determined age values for zircon 91500 agree with TIMS data and are homogeneous within 8.7 Ma (2s). A two-stage ablation strategy was developed for optimising U-Pb age determinations with satisfactory trace element and REE results. The first cycle of ablation was used to collect data for age determination only, which was followed by continuous ablation on the same spot to determine REE and trace element concentrations. Based on this procedure, it was possible to measure zircon ages as low as 30.37 0.39 Ma (MSWD = 1.4; 2s). Other examples for older zircons are also given. Différents zircons d'âges variant du Protérozoïque à l'Oligocène (1060-31 Ma) ont été analysés par spectrométrie avec source à plasma induit et ablation laser. La calibration a été faite en utilisant le zircon 91500 de référence de Harvard ou le zircon TEMORA 1 de référence de l'Université Nationale Australienne comme calibrant externe. Les résultats sont en accord avec ceux obtenus par SIMS aux erreurs analytiques près (2s). Vingt-quatre éléments en trace et Terres Rares (P, Ti, Cr, Y, Nb, quatorze ETR, Hf, Ta, Pb, Th et U) ont été analysés sur quatre fragments du zircon 91500. Le standard SRM 610 de NIST a été utilisé comme matériau de référence et 29Si comme calibrant interne. À partir des déterminations faites sur ces quatre fragments, ce zircon montre des variations intra et inter fragments de l'ordre de 10%à 85%à une échelle de 120 ,m, avec des variations des concentrations de Terres Rares allant jusquà 38.7%, bien que le spectre de Terres Rares normalisé aux chondrites reste très constant. Au contraire, les âges déterminés pour le zircon 91500 sont en accord avec les résultats de TIMS et sont homogènes à 8.7 Ma près (2s). Une stratégie d'ablation en deux étapes a été développée pour optimiser les déterminations d'âges U-Pb, et avoir des résultats de Terres Rares et d'éléments en trace satisfaisants. Le premier cycle d'ablation était utilisé pour collecter les données nécessaires à la détermination de l'âge seulement et était suivi d'un cycle d'ablation continue sur le même spot, pour déterminer les concentrations en Terres Rares et en éléments en trace. Grâce à cette procédure, il a été possible de mesurer des âges sur zircons aussi récents que 30.37 0.39 Ma (MSWD = 1.4; 2s). D'autres exemples sur des zircons plus vieux sont aussi donnés. [source] Continental basalts in the accretionary complexes of the South-west Japan Arc: Constraints from geochemical and Sr and Nd isotopic data of metadiabaseISLAND ARC, Issue 1 2000Hiroo Kagami Abstract The Ryoke Belt is one of the important terranes in the South-west Japan Arc (SJA). It consists mainly of late Cretaceous granitoid rocks, meta-sedimentary rocks (Jurassic accretionary complexes) and mafic rocks (gabbros, metadiabases; late Permian,early Jurassic). Initial ,Sr (+ 25, + 59) and ,Nd (, 2.1,,5.9) values of the metadiabases cannot be explained by crustal contamination but reflect the values of the source material. These values coincide with those of island arc basalt (IAB), active continental margin basalt (ACMB) and continental flood basalt (CFB). Spiderdiagrams and trace element chemistries of the metadiabases have CFB-signature, rather than those of either IAB or ACMB. The Sr,Nd isotope data, trace element and rare earth element chemistries of the metadiabases indicate that they result from partial melting of continental-type lithospheric mantle. Mafic granulite xenoliths in middle Miocene volcanic rocks distributed throughout the Ryoke Belt were probably derived from relatively deep crust. Their geochemical and Sr,Nd isotopic characteristics are similar to the metadiabases. This suggests that rocks, equivalent geochemically to the metadiabases, must be widely distributed at relatively deep crustal levels beneath a part of the Ryoke Belt. The geochemical and isotopic features of the metadiabases and mafic granulites from the Ryoke Belt are quite different from those of mafic rocks from other terranes in the SJA. These results imply that the Ryoke mafic rocks (metadiabase, mafic granulite) were not transported from other terranes by crustal movement but formed in situ. Sr,Nd isotopic features of late Cretaceous granitoid rocks occurring in the western part of the Japanese Islands are coincident with those of the Ryoke mafic rocks. Such an isotopic relation between these two rocks suggests that a continental-type lithosphere is widely represented beneath the western part of the Japanese Islands. [source] Selenium and selenoproteins in the brain and brain diseasesJOURNAL OF NEUROCHEMISTRY, Issue 1 2003Jun Chen Abstract Over the past three decades, selenium has been intensively investigated as an antioxidant trace element. It is widely distributed throughout the body, but is particularly well maintained in the brain, even upon prolonged dietary selenium deficiency. Changes in selenium concentration in blood and brain have been reported in Alzheimer's disease and brain tumors. The functions of selenium are believed to be carried out by selenoproteins, in which selenium is specifically incorporated as the amino acid, selenocysteine. Several selenoproteins are expressed in brain, but many questions remain about their roles in neuronal function. Glutathione peroxidase has been localized in glial cells, and its expression is increased surrounding the damaged area in Parkinson's disease and occlusive cerebrovascular disease, consistent with its protective role against oxidative damage. Selenoprotein P has been reported to possess antioxidant activities and the ability to promote neuronal cell survival. Recent studies in cell culture and gene knockout models support a function for selenoprotein P in delivery of selenium to the brain. mRNAs for other selenoproteins, including selenoprotein W, thioredoxin reductases, 15-kDa selenoprotein and type 2 iodothyronine deiodinase, are also detected in the brain. Future research directions will surely unravel the important functions of this class of proteins in the brain. [source] Temporal responses in the disruption of iron regulation by manganeseJOURNAL OF NEUROSCIENCE RESEARCH, Issue 8 2006Catherine Kwik-Uribe Abstract Manganese (Mn) is an essential trace element, though at elevated exposures it is also a neurotoxicant. Several mechanisms underlying manganese toxicity have been investigated, although a consistent mechanism(s) of action at low exposures has not been fully elucidated. Here we systematically evaluated the effects of in vitro manganese exposure on intracellular iron (Fe) homeostasis and iron-regulatory protein (IRP) binding activity in undifferentiated PC12 cells over a range of manganese exposure concentrations (1, 10, 50, and 200 ,M MnCl2) and exposure durations (12, 24, 36, and 48 hr), to test the hypothesis that moderately elevated manganese exposure disrupts cellular iron regulation. Results demonstrate that manganese exposure produces a rapid and sustained dose-dependent dysregulation of cellular iron metabolism, with effects occurring as early as 12 hr exposure and at manganese doses as low as 1 ,M. Manganese exposure altered the dynamics of IRP-1 binding and the intracellular abundance of IRP-2, and altered the cellular abundance of transferrin receptor, ferritin, and mitochondrial aconitase protein levels. Cellular levels of labile iron were significantly increased with manganese exposure, although total cellular iron levels were not. The overall pattern of effects shows that manganese produced an inappropriate cellular response akin to iron deficiency, to which the cells were able to mount a compensatory response. Consistent with our previous studies, these data indicate that even low to moderate exposures to Manganese in vitro significantly disrupt cellular iron metabolism, which may be an important contributory mechanism of manganese neurotoxicity. © 2006 Wiley-Liss, Inc. [source] Seasonal records of climatic change in annually laminated tufas: short review and future prospects,JOURNAL OF QUATERNARY SCIENCE, Issue 5 2005J. E. Andrews Abstract Many Recent and fossil freshwater tufa stromatolites contain millimetre-scale, alternating laminae of dense micrite and more porous or sparry crystalline calcites. These alternating laminae have been interpreted to represent seasonally controlled differences in the biotic activity of microbes, and/or seasonally controlled changes in the rate of calcification. Either way, couplets of these microbially mediated alternating calcified laminae are generally agreed to represent annual seasonality. Combined stable isotope (,18O and ,13C) and trace element (Mg, Sr, Ba) geochemistry from Recent tufa stromatolites show that seasonal climatic information is available from these calcites. Variability in ,18O (and in one case Mg concentration) has been shown to be controlled primarily by stream temperature change, usually driven by solar insolation. In arid climates, seasonal evaporation can also cause ,18O enrichment by at least 1,. Variability in ,13C results potentially from: (1) seasonal change in plant uptake of 12C-enriched CO2; (2) seasonal change in degassing of 12C-enriched CO2 in the aquifer system; and (3) precipitation of calcite along the aquifer or river flow path, a process that increases ,13C of dissolved inorganic carbon (DIC) in the remaining water. Mechanisms 2 and 3 are linked because calcite precipitates in aquifers where degassing occurs, e.g. air pockets. The latter mechanism for ,13C enrichment has also been shown to cause sympathetic variation between trace element/Ca ratios and ,13C because trace elements with partition coefficients much greater than 1 (e.g. Sr, Ba) remain preferentially in solution. Since degassing in air pockets will be enhanced during decreased recharge when water saturation of the aquifer is lowest, sympathetic variation in trace element/Ca ratios and ,13C is a possible index of recharge and therefore precipitation intensity. High-resolution geochemical data from well-dated tufa stromatolites have great potential for Quaternary palaeoclimate reconstructions, possibly allowing recovery of annual seasonal climatic information including water temperature variation and change in rainfall intensity. However, careful consideration of diagenetic effects, particularly aggrading neomorphism, needs to be the next step. Copyright © 2005 John Wiley & Sons, Ltd. [source] Cadmium concentration in durum wheat grain (Triticum turgidum) as influenced by nitrogen rate, seeding date and soil typeJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2010Patrizia Perilli Abstract BACKGROUND: Cadmium (Cd) is a trace element that has been associated with various human health problems. Cd enters plants, either by direct absorption through leaves or by uptake from soils, allowing Cd into the food chain. Nitrogen (N) fertilizer management is important in optimizing crop yield and protein content of durum wheat, but may influence Cd availability and hence Cd concentration in crops, with the effects being strongly influenced by environmental conditions and crop cultivar. RESULTS: In field studies, Cd and protein concentration in durum wheat grain differed between cultivars and were strongly affected by N application, with only minor effects of N occurring on concentration and uptake of P and Zn. Protein content increased significantly with N application in five of six site-years, with the response being generally independent of cultivar and seeding data. Cd concentration also increased with N application in five of six seeding dates, with the response being greater in AC Melita than Arcola in three of the six site-years. There were large differences in Cd concentration from year to year and with seeding date, indicating a strong environmental influence. CONCLUSIONS: This study shows that different cultivars accumulate different levels of Cd in the grain and that seeding date and nitrogen fertilizer management can influence grain Cd concentration, with the magnitude of effects varying with environmental factors. In the future we may be able to manipulate management practices to optimize protein concentration and minimize Cd concentration in durum wheat, which could help to address the health and safety concerns of consumers. © Society of Chemical Industry and Her Majesty the Queen in right of Canada [source] Biofortification of lettuce (Lactuca sativa L.) with iodine: the effect of iodine form and concentration in the nutrient solution on growth, development and iodine uptake of lettuce grown in water cultureJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2010Wim Voogt Abstract BACKGROUND: Iodine is an essential trace element for humans. Two billion individuals have insufficient iodine intake. Biofortification of vegetables with iodine offers an excellent opportunity to increase iodine intake by humans. The main aim was to study the effect of iodine form and concentration in the nutrient solution on growth, development and iodine uptake of lettuce, grown in water culture. RESULTS: In both a winter and summer trial, dose rates of 0, 13, 39, 65, and 90 or 129 µg iodine L,1, applied as iodate (IO3,) or iodide (I,), did not affect plant biomass, produce quality or water uptake. Increases in iodine concentration significantly enhanced iodine content in the plant. Iodine contents in plant tissue were up to five times higher with I, than with IO3,. Iodine was mainly distributed to the outer leaves. The highest iodide dose rates in both trials resulted in 653 and 764 µg iodine kg,1 total leaf fresh weight. CONCLUSION: Biofortification of lettuce with iodine is easily applicable in a hydroponic growing system, both with I, and IO3,. I, was more effective than IO3,. Fifty grams of iodine-biofortified lettuce would provide, respectively, 22% and 25% of the recommended daily allowance of iodine for adolescents and adults. Copyright © 2010 Society of Chemical Industry [source] | |||||||||||||||||||||||||||||||||||||||||||