Trace Element Values Research Articles

Equilibrium and Disequilibrium Trace Element Partitioning in Hydrous Eclogites (Trescolmen, Central Alps)

elements, Pb, Th and U, whereas phengite hosts Ba and is, along Despite the widespread presence of hydrous phases in subductionwith clinopyroxene and paragonite, an important phase for B. related systems, experimental D trace element values for many However, because of their low modal abundance in eclogite-facies hydrous phases are lacking. To fill this gap, we present a set of rocks, phengite and paragonite do not control the B whole-rock budget. D values (where Min indicates amphibole, zoisite, We infer that estimated D values from equilibrium phengite, paragonite or apatite) derived from equilibrium parageneses assemblages can be used as a good approximation for partition of eclogites from Trescolmen (Central Alps, Switzerland). These coefficients under the given PT conditions (>650°C and 2·0 data can be combined with experimental data for D, GPa). Deformation-induced dynamic recrystallization seems to be to estimate D values for the hydrous phases, thus circumventing the driving process necessary for a close approach towards trace experimental problems with the direct determination of such values. element equilibrium. This process should work efficiently during We analysed Li, Be, B, Sr, Y, Zr, Nb, Ba, Ce, Nd, Sm, Pb, Th subduction close to the slab–mantle interface, affecting sediments and U in coexisting phases by laser ablation microprobe inductively and low-T altered mid-ocean ridge basalt, but is of less importance coupled plasma mass spectrometry. Many of the values are extremely inside the slab. Knowledge of D values from equilibrium assemblages low; for example, Nb, Ba, Ce, Th and U are in the lower ppb determined in this study is useful not only for large-scale subductionrange in clinopyroxene. Attainment of equilibrium was evaluated zone modelling, but also as an aid in the selection of equilibrium by textural, and major and trace element characteristics. Nonsubassemblages in imperfectly equilibrated samples, so that a equilibrated assemblages are common in most eclogite localities, crystallization sequence can be derived. including Trescolmen, and using such samples would lead to the derivation of erroneous values for equilibrium partitioning. However, four of the 10 studied eclogites from Trescolmen having homogeneous

Attenuation of spectral interferences during laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) using an rf only collision and reaction cell

The reduction of spectral interferences in laser ablation inductively coupled plasma mass spectrometry was investigated using an rf only hexapole as a collision and reaction cell with H2 as the reaction gas and He as a buffer gas. Argon-based polyatomic ions (ArX+) were attenuated by between 1 and 6 orders of magnitude with H2 during laser ablation experiments whilst analyte transmission under the same parameters was maintained above 80%. The amount of ArX+ attenuation for a fixed volume of reactive H2 gas was proportional to the electronegativity of parent element X. Interferences were not significantly attenuated with He. However, a change from ‘dry’ to ‘wet’ conditions in the plasma led to reactions with water molecules in the cell giving an apparent reactivity for clean He buffer gas whilst reducing the efficiency of some reactions with H2. Improved accuracy and precision were demonstrated under optimised conditions for the analysis of trace elements in sulfide and carbonate standard reference materials as a result of background interference reduction. Multi-element analysis was possible with reactive gases in the reaction cell as demonstrated by the accurate analysis, to within 15% of the recommended values for most trace elements, of candidate glass reference materials using NIST SRM glasses for calibration.

Critical values of trace elements in soils from the viewpoint of the transfer pathway soil - plant

The development of soil limiting values of the protection of the quantity and mainly quality of the crop production tends from empiric values towards critical values, based on ecotoxicity. We present an attempt to derive transfer functions by the means of multiple regression analysis. The substitution of trace elements contents in crops in the prediction equations for fodder or food standards or phytotoxicity limits satisfies the present ecotoxicological demands. We preferred polyfactor relations to simple ones. The exceeding of reference values must be verified by the determination of the hazardous transfer in the field. Therefore the reference values are called testing values. They were derived especially for Cd, Pb, As, Cu, Zn, Ni and Mn. For some trace elements, only protective values can be set up (especially for Cr, Hg, but also for Tl, Be, V). They reflect minimum values that guarantee growing crops without any risks. Experimental data (pot trials) were compared with results obtained in field investigations. The resulting critical values were also compared with the values proposed in Germany.

Influence of vegetation change on watershed hydrology: implications for paleoclimatic interpretation of lacustrine δ18O records

Stratigraphic shifts in the oxygen isotopic (δ18O) and trace element (Mg and Sr) composition of biogenic carbonate from tropical lake sediment cores are often interpreted as a proxy record of the changing relation between evaporation and precipitation (E/P). Holocene δ18O and Mg and Sr records from Lakes Salpetén and Petén Itzá, Guatemala were apparently affected by drainage basin vegetation changes that influenced watershed hydrology, thereby confounding paleoclimatic interpretations. Oxygen isotope values and trace element concentrations in the two lowland lakes were greatest between ~ 9000 and 6800 14C-yr BP, suggesting relatively high E/P, but pollen data indicate moist conditions and extensive forest cover in the early Holocene. The discrepancy between pollen- and geochemically-inferred climate conditions may be reconciled if the high early Holocene δ18O and trace element values were controlled principally by low surface runoff and groundwater flow to the lake, rather than high E/P. Dense forest cover in the early Holocene would have increased evapotranspiration and soil moisture storage, thereby reducing delivery of meteoric water to the lakes. Carbonate δ18O and Mg and Sr decreased between 7200 and 3500 14C-yr BP in Lake Salpetén and between 6800 and 5000 14C-yr BP in Lake Petén Itzá. This decline coincided with palynologically documented forest loss that may have led to increased surface and groundwater flow to the lakes. In Lake Salpetén, minimum δ18O values (i.e., high lake levels) occurred between 3500 and 1800 14C-yr BP. Relatively high lake levels were confirmed by 14C-dated aquatic gastropods from subaerial soil profiles ~ 1.0–7.5 m above present lake stage. High lake levels were a consequence of lower E/P and/or greater surface runoff and groundwater inflow caused by human-induced deforestation.

The Incorporation of Laser Ablation for Sampling into a Proton X-ray Emission System

ABSTRACTThe variation with depth of the composition of corrosion layers on buried metal objects can provide the archaeologist with valuable information relating to the burial conditions of the object. In some cases these layers can be very thick and so, normally destructive methods such as sampling are used to characterise the metal and corrosion layers when possible. We have developed a system for the use of a microfocused high power pulsed Nd:YAG laser to ablate the corrosion layer in a series of controlled steps while monitoring the composition of the exposed surface using focused PIXE and RBS in the external beam facility of the Oxford Scanning Proton Microprobe. With proper manipulation of the data we are able to calculate the values for trace elements at various depths in the corrosion layer. It is hoped that this system will lead to a better understanding of corrosion properties.

Analysis of some Nigerian solid mineral ores by energy-dispersive X-ray fluorescence spectroscopy

Determination of major, minor and trace elements in some Nigerian solid mineral ores by energy-dispersive X-ray fluorescence (EDXRF) spectroscopy is described. Concentration values of major, minor and trace elements for Z>18 are reported. The mineral ores studied include (i) tantalite–coloumbite minerals, (ii) bismuth minerals and (iii) lead minerals. The accuracy and precision of the technique for chemical analysis was assured by analysing the geological standards mica–Fe (biotite) and NBS 278 (obsidian).

Short-term environmental change in a Jurassic lagoon deduced from geochemical trends in aragonite bivalve shells

The Bathonian age Inverbrora Member of the Brora Coal Formation, northern Scotland, was deposited in a predominantly fresh- water coastal lagoon setting. However, two prominent shell beds within the mostly argillaceous succession have been interpreted as resulting from temporary inundation of marine water and establishment of brackish conditions. The ensuing lagoon hydrology and paleoenvironment were investigated by measuring stable isotopic (δ18O and δ13C) and trace element (Mg, Sr, Mn, Ba) variations within five exceptionally well preserved aragonite shells of the bivalve Isognomon murchisoni . Transects were sampled across the visible growth banding with a resolution of 0.25−0.15 mm for stable isotopes, and 0.05 mm for trace elements. Oxygen and carbon isotope data define a broadly covariant trend (δ18O between +0.4‰ and −4.8‰ Peedee belemnite [PDB]; δ13C between +2.2‰ and −0.7‰ PDB) that supports a variably brackish-water setting with slight seasonal evaporation. Absolute trace element values vary from shell to shell but show consistent patterns of covariation. Profiles of Mg/Ca across shell layers display multiple sharp, episodic minima that are coincident with peaks in Sr/Ca and Ba/Ca. This is interpreted as documenting inundation of the restricted, brackish-water lagoon by relatively cooler seawater, leading to a temporary increase in metabolic activity of the bivalves. Less frequent minima in Mg/Ca, Sr/Ca, δ18O, and δ13C record fresh-water influx and dramatic salinity reduction in the lagoon. Bivalve metabolic efficiency was decreased, and in some cases breaks in shell growth occurred. This study shows that in hydrodynamically complex settings, trace element variation in bivalve shells can provide a detailed record of short-term environmental change.

Marine Chemistry of the Permian Phosphoria Formation and Basin, Southeast Idaho

Major components in the Meade Peak Member of the Phosphoria Formation are apatite, dolomite, calcite, organic matter, and biogenic silica—a marine fraction; and aluminosilicate quartz debris—a terrigenous fraction. Samples from Enoch Valley, in southeast Idaho, have major element oxide abundances of Al2O3, Fe2O3, K2O, and TiO2 that closely approach the composition of the world shale average. Factor analysis further identifies the partitioning of several trace elements—Ba, Ga, Li, Sc, and Th and, at other sites in southeast Idaho and western Wyoming, B, Co, Cs, Hf, Rb, and Ta—totally into this fraction. Trace elements that fail to show such correlations or factor loadings include Ag, As, Cd, Cr, Cu, Mo, Ni, Se, the rare earth elements (REE), U, V, and Zn. Their terrigenous contribution is determined from minimum values of trace elements versus the terrigenous fraction. These minima too define trace element concentrations in the terrigenous fraction that approximately equal their concentrations in the world shale average. The marine fraction of trace elements represents the difference between the bulk trace element content of a sample and the terrigenous contribution. Of the trace elements enriched above a terrigenous contribution, Ag, Cr, Cu, Mo, and Se show strong loadings on the factor with an organic matter loading and U and the REE on the factor with a strong apatite loading. Cd, Ni, V, and Zn do not show a strong correlation with any of the marine components but are, nonetheless, strongly enriched above a terrigenous contribution. Interelement relationships between the trace elements identify two seawater sources—planktonic debris and basinal bottom water. Relationships between Cd, Cu, Mo, Zn, and possibly Ni and Se suggest a solely biogenic source. Their accumulation rates, and that of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(PO_{4}^{3{\mbox{--}}}\) \end{document}, further identify the level of primary productivity as having been moderate and the residence time of water in the basin at 4.5 yr. Enrichments of Cr, U, V, and the REE, above both terrigenous and biogenic contributions, define bottom-water redox conditions as having been oxygen depleted, that is, denitrifying but not sulfate reducing.

Mantle reservoir geochemistry from statistical analysis of ICP-MS trace element data of equatorial mid-Atlantic MORB glasses

We report Inductively Coupled Plasma Mass Spectrometer (ICP-MS) trace element concentration data for 21 elements in 51 basaltic glasses recovered from 58 stations along a 1500-km segment of the equatorial mid-Atlantic Ridge (MAR; 5°N to 5°S). Isotope systematics of these glasses revealed mixing between two isotopically distinct (Schilling, J.-G., Hanan, B.B., McCully, B., Kingsley, R.H., 1994. Influence of the Sierra Leone mantle plume on the equatorial MAR: a Nd–Sr–Pb isotopic study. J. Geophys. Res., 99, 12005–12028.) HIMU and DM mantle sources. Trace element data presented here describe three distinct mantle reservoirs. Based on our new trace element data, we identified three, and possibly four, end-member mantle reservoirs beneath the equatorial MAR. HIMU-type signatures dominate the glasses from the northern equatorial MAR (5°N to 0°) with La/Ba, La/Th and rare earth element (REE) values similar to P-type mid-Ocean Ridge Basalts (MORB; 0.1, 9.11, (La/Yb) N =5.5, respectively). The basaltic glasses from the southern region (0° to 5°S) are mildly radiogenic in Pb and light REE depleted with N-type MORB trace element values for La/Ba, La/Th and REE (0.8, 40.0, (La/Yb) N <0.6, respectively). We estimate the mantle magma-source characteristics and identify the relative contributions of the mantle end-member components in the glasses erupted along the 1500-km transect using the trace element concentration data. Specifically, we recognize the presence of a statistically and geochemically distinct mantle reservoir depleted in Th and Ba relative to average depleted MORB between the Romanche and the Chain fracture zones. To reach the full potential of this data set, we model mantle reservoir compositions using a modification of Q-MODE factor analysis. Multivariate classification and reduction of these data clearly distinguish trace element groups each reflective of mantle source heterogeneities present in this region of the MAR. Statistical analysis of these new trace element and available Nd–Sr–Pb isotope data for the same samples defines four statistically significant distinct end-member mantle components. The binary mixing model developed previously from geochemical data that invoked the mixing of two mantle reservoirs, HIMU and N-MORB, cannot adequately explain the variance in these trace element data. Incompatible element concentrations and ratios best describe the modeled end-members reservoirs, which are HIMU (HPM), transitional N-MORB (TNM), depleted N-MORB (DNM) and an fourth incompatible element-enriched component (EPM). The statistically determined end-members explain 100% of the geochemical variance in the population but their modeled compositions may be related to process controlled variation. We clarify the relationship between statistical and geochemical reservoirs and conclude that a multiple mantle component model involving three of the identified reservoirs is clearly necessary to describe, specifically, the trace element characteristics of the equatorial mid-Atlantic MORBs. Our statistical methods yield tabulated trace element concentration data for each of these the modeled mantle components and provide insights into the MAR system, unavailable by any other technique, by allowing an estimation of the relative contributions of these end-member components in each of the 51 basaltic glass samples.

Elemental analysis of two Egyptian iron ores and produced industrial iron samples by neutron activation analysis

Elemental analysis of two iron ores and initial industrial iron production prepared by the Egyptian Iron and Steel Company of Helwan near Cairo were performed by the instrumental neutron activation analysis technique. Five samples of each type were irradiated for 48 h in a thermal neutron flux of 4 × 10 12 n/cm 2 s in the first Egyptian research reactor ET-RR-1. Also, the Pneumatic Irradiation Rabbit System (PIRS), attached to the reactor ET-RR-1 in Inshass, was used to measure short-life elements. The γ-ray spectra were obtained with a hyper pure germanium detection system. The concentration percentage values of major, minor and trace elements are presented. Implications of the elemental concentration values obtained are presented.

Reference values for trace and ultratrace elements in human serum determined by double-focusing ICP-MS.

Reference values for trace and ultratrace elements concentrations in healthy human serum, measured by double-focusing inductively coupled plasma-mass spectrometry (ICP-MS), are presented. Blood donors from Asturias (Spain) were selected as the reference population (n=59). Blood samples were collected, after donation, taking the necessary precautions to avoid contamination. All subjects analyzed had normal renal function and nutritional status, as shown from their creatinine and albumin levels. A total number of 14 elements (Al, Ca, Cr, Mn, Fe, Co, Cu, Zn, Rb, Sr, Mo, Cd, Pb, and U) were monitored almost simultaneously. Serum samples were diluted 1+4 with ultrapure water and matrix interferences were corrected using Sc, Ga, Y, and Tl as internal standards. Fe, Cu, and Zn were also determined by isotope dilution analysis (IDA). Reference trace element concentrations intervals observed containing 95% of the reference distribution after excluding outliers are presented. Fourteen serum samples from hemodialysis patients were also analyzed for comparison. High levels of Al, Cr, Sr, Mo, Mn, Pb, U, Co, and Cu and low levels of Fe, Zn, and Rb were found in the serum samples from hemodialysis patients compared to the corresponding reference values observed in this work.

Natural compositional variation of the river Meuse (Maas) suspended load: a 13 ka bulk geochemical record from the upper Kreftenheye and Betuwe Formations in northern Limburg

AbstractUnambiguously pristine and largely unpolluted sediments from the Late Weichselian and Holocene infillings of the Meuse residual channels in northern Limburg (the Netherlands) have been sampled to determine the natural compositional variation of the river’s suspended load.Bulk geochemical and granulometric analyses demonstrate that about 70% of the variation can be ascribed to hydrodynamic mineral sorting. Clay- and fine silt-sized phyllosilicates are the most important deterministic features, hosting the bulk of AI2O3, TiO2, K2O, MgO and trace element variability (notably Ba, Cr, Ga, Rb and V). Quartz is abundant in the fine and coarse sand fractions. Na2O and the Zr-Nb-Nd-Y quartet relate to albitic feldspars and heavy minerals, respectively, in the coarse silt fraction. The granulometry should therefore be quantified if geochemical baseline data for a particular geological unit or region are drawn up and for the evaluation of potentially polluted sediments.Although provenance has not changed, the composition of Meuse sediments cannot be considered constant over a time frame of 1000–10,000 years, due to climatic change. Weathering of phyllosilicates in both interstadial and interglacial soil environments and changing relative source-area contributions alter the detrital clay-mineral supply to raise the AI2O3 and lower the K2O and MgO contents in Holocene Meuse sediments. Early diagenetic siderite and vivianite formation in gyttjas causes relative accumulations of Fe2O3, MnO, P2O5, Co, Ni and notably Zn above the phyllosilicate background values. These accumulations are natural and show that sediments with elevated trace metal contents are not necessarily polluted. Very early atmospheric pollution in relation to ore mining and smelting activities in the Roman era, however, probably caused elevated Pb contents in Subatlantic humic clays and peat samples, long before the historic pollution of the Industrial Revolution started.The A12O3, Fe2O3 and CaO contents are used to predict the trace-element values as a function of sample granulometry, siderite/vivianite and lime content, respectively. As such, they can provide a sound basis for environmental researchers to determine baseline values of heavy metals in bulk samples of fine-grained fluvial sediments.

The bioaccessibility of essential and potentially toxic trace elements in tropical soils from Mukono District, Uganda

It has been postulated that endomyocardial fibrosis (EMF), a common cardiac disease in certain tropical communities including parts of Uganda, may be related to the presence of elevated levels of dietary Ce, and deficient levels of dietary Mg. In Uganda, significant variation in dietary exposure to both elements is likely due to variations in local soil geochemistry and dietary habits, including geophagia (the deliberate consumption of soil). This paper reports the concentration and bioaccessibility (determined from a physiologically based extraction test—PBET) of Ce and other essential (Mg and Fe) and trace elements in soils from the Mukono district of Uganda. Trace element concentrations varied markedly between soil samples (ground soils) and soils eaten deliberately, such as termite nest soils and traditional herbal–soil remedies. The highest bioaccessibility values were reported for the chelate-rich, intestinal phase of the PBET. Median percentage bioaccessibility values for Ce (1–15%), Mg (7–33%), Fe (0.1–2.9%) and other trace elements varied considerably, but were generally higher in geophagic (herbal–soil remedies and terminte nest soils) than common (ground) soil samples. Only in the case of Fe does the ingestion of soil account for a major proportion of recommended daily intake (RDI). The revised estimates of Ce and Mg dietary intake (based on bioaccessibility data rather than an assumption of 100% bioavailability) significantly reduced the importance of geophagia relative to exposure through the ingestion of food and water.

Provenance of the lower Tertiary mudrocks in the Jammu Sub-Himalayan Zone, Jammu and Kashmir State (India), NW Himalaya and its tectonic implications

The lower Tertiary mudrocks are rich in clay minerals, which together form 48–60% whereas quartz forms 30–41% of the bulk minerals. Clay minerals of the Subathu shales are composed of illite, chlorite, and sepiolite. In the mudstones of the Murree Group, illite and chlorite are associated with kaolinite and sepiolite. The illite- and chlorite-bearing suites are indicative of their derivation from metamorphic and magmatic sources. The presence of smectite in the calcrete indicates weathering and soil-forming processes. In SiO2 vs. K2O/Na2O diagram, the mudrocks occupy active continetal margin (ACM) field with a few exceptions, suggesting that they originated from an active continental margin, orogenic belt or strike-slip basin. On the other hand in mudrock maturity index vs. log K2O/Na2O plot, the points occupy an area in and above/around phyllo-tectic field. The trace elements values, and Rb/Sr and Ba/Sr ratios are close to the values suggested for active continental margin.

TRACE ELEMENT CONCENTRATION PATTERNS IN SEDIMENTS OF THE LOWER RIO CONCHOS, MEXICO

A two-step sequential extraction of B, V,Cr, Ni, Cu, and Pb in sediments from the lower RioConchos, Mexico, was used to identify sections of theriver where accumulation of these elements has takenplace. The concentrations of Mg, Fe and Al insediments were concurrently determined in order toinfer about the possible source of trace elements.According to their extractability, B and Pb werelabeled as more mobile, while Cr was the least mobile.Normalized concentration and partition coefficient(Kd) values along the lower Rio Conchos helpedidentify locations with abnormally large trace elementvalues. Sites near urban centers showed the mostaccumulation with respect to most elements, while thehighest B and Pb Kd values were found at sites farfrom urban areas and irrigation drain returns.Correlation analysis between sediment and waterconcentrations indicated a separate concentrationpattern for the sediments, most likely the result oftheir longer term element storing ability as comparedto water. In contrast, a high correlation was obtainedamong elements in sediments, with the exception of Band Pb. This study is a preliminary effort toquantitatively determine the impacts of irrigation andother human activities to the quality of one ofnorthern Mexico's most important rivers.

IAEA Internet database of natural matrix reference materials.

The International Atomic Energy Agency maintains a database on internationally available certified reference materials of natural origin. The database was updated in 1998 and prepared for an Internet implementation. A user-friendly structure was created, providing two main pathways for browsing, either according to the matrix classification or the producer's name. The database presently contains over 20,000 values for 480 measurands and 1085 reference materials from 43 different producers. Most of the materials entered contain values for trace and minor elements (66%).

Elemental sulfur formation related to celestine reduction: An example of biomineralization of bacterial origin

This study investigates the disseminated elemental sulfur formation in celestine mineralization in the upper member of the Bozbel Formation (Eocene) in the Sivas basin, Turkey. Optical and scanning electron microscope studies indicate that the sulfur minerals have three main morphologies including lacy, grape-like, and spheroidal — lobous types structures. These sulfur structures are occasionally coated with organic matter. Total organic carbon and infrared spectrometry studies indicate that an average of 1 % organic matter in this sulfur is of biogenic origin. Detailed studies on these elemental sulfur deposits suggest that the sulfur was formed by the reduction of celestine through the metabolic activities of sulfate reducing bacteria. This observation is supported by the trace element values obtained through x-ray fluorescence analyses on both the celestine and the elemental sulfur samples.

Preservation of delta 18 O and delta 13 C in belemnite rostra from the Jurassic/Early Cretaceous successions

Stratigraphic collection of 263 belemnite rostra (guards) from Jurassic to Lower Cretaceous sediments in the Moscow area of Russia, northern Germany, England, New Zealand, and Morocco were analyzed to determine temporal variations in their delta 18 O and delta 13 C as a proxy for isotopic composition of surface seawater. Internal structures of the rostra were studied using cathodoluminescence and SEM techniques, their trace element (Fe, Mn, Mg, and Sr), and the stable carbon and oxygen isotope compositions. The average stratigraphic resolution is about 1 Ma. These samples represent a broad range of paleolatitudes and paleoceanographic settings, ranging from 42 degrees N to 82 degrees S, covering boreal to subtropical, brackish to open marine shelf paleoenvironments. The rostra originally contained domains enriched in organic matter that were later replaced by luminescent diagenetic calcite, thereby generating an impression of seasonal growth rings. Diagenetic calcite accounts for up to 6.8 percent of the rostrum. The trace element content of the rostra range from 227 to 3935 ppm for Mg, 379 to 1514 ppm for Sr, and up to 305 and 3662 ppm for Mn and Fe, respectively. However, selective drilling of only primary calcitic domains resulted in 90 percent of all analyzed samples to fall within the range of trace element values typical for modern low Mg-calcite shells. The chemical and textural data suggest that the primary calcite of the rostra is well preserved, as is its isotopic signature. The delta 13 C and delta 18 O measurements define oscillating temporal bands, of about 3 to 4 per mil width, around more or less modern marine values of +2 and -1 per mil, respectively. Oxygen isotopes in the well preserved rostra most likely reflect temperature variations within a approximately 14+ or -8 degrees C range. The observed 3 to 4 per mil spread of values between contemporaneous specimens, which is comparable to the scatter of data reported for modern low-Mg calcitic brachiopod shells, probably reflects the diversity of local ecosystems, although some of the spread may be due to real short term temporal variations within single biozones. The delta 13 C values of the rostra define a band similar to that of the oxygen isotopes, and the temporal oscillations of both isotope curves are commonly in phase. The above dataset, complemented by the results of Jones, Jenkyns, and Hesselbo (1994) and Jones and others (1994), yields a composite delta 18 O and delta 13 C variations in belemnite guards for the entire Jurassic-Early Cretaceous interval. For delta 18 O, the oscillating band indicates that the most negative values occur at times of independently postulated global and/or regional anoxic events, such as those in the Toarcian and Kimmeridgian as well as the Aptian. These OAEs appear to be characterized by up to 10 degrees C higher seawater temperatures than the intervening background times. The delta 13 C record shows 13 C depletion for the Kimmeridgian event but enrichment for the other two, suggesting that the delta 13 C temporal oscillations and OAEs are not simply a reflection of surficial productivity due to operation of the biological pump, but rather of changing oceanic circulation patterns due to variations in latitudinal surface temperature gradients.

Particle size determination of some IAEA and NIST environmental and biological reference materials

Particle size distributions in fifteen International Atomic Energy Agency (IAEA) and sixteen National Institute of Standards and Technology (NIST) reference materials (RMs) were measured with the basic aim to investigate the potential of these materials to be used as reference or quality control materials in analyses where a small sample mass is required (< 100 mg). Most of the investigated materials are commercially available environmental or biological natural matrix RMs with certified values for trace elements, radionuclides, or organometallic compounds. The laser diffraction technique was used in all measurements. From the point of particle size distribution, materials IAEA-390 (Algae, a set of three materials), IAEA-396m (Urban Dust, 3x air jet milled), NIST-SRM 1515 (Apple Leaves), NIST-SRM 1547 (Peach Leaves), NIST-SRM 1566a (Oyster Tissue), NIST-SRM 1570a (Spinach), NIST-SRM 1573a (Tomato Leaves), and NIST-SRM 1648 (Urban Particulate) can be considered appropriate for small sample mass analysis. However, additional analytical tests are needed to confirm the appropriate homogeneous distribution of chemical composition, the level of heterogeneity for individual elements, at this sample mass level.

Re-evaluation and extension of the scope of elements in US Geological Survey Standard Reference Water Samples†

More than 100 US Geological Survey (USGS) Standard Reference Water Samples (SRWSs) were analyzed for numerous trace constituents, including Al, As, B, Ba, Be, Bi, Br, Cd, Cr, Co, Cu, I, Fe, Pb, Li, Mn, Mo, Ni, Rb, Sb, Se, Sr, Te, Tl, U, V, Zn and major elements (Ca, Mg, Na, SiO2, SO4, Cl) by inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectrometry. In addition, 15 USGS SRWSs and National Institute of Standards and Technology (NIST) standard reference material (SRM) 1641b were analyzed for mercury using cold vapor atomic fluorescence spectrometry. Also USGS SRWS Hg-7 was analyzed using isotope dilution–inductively coupled plasma mass spectrometry. The results were compared with the reported certified values of the following standard reference materials: NIST SRM 1643a, 1643b, 1643c and 1643d and National Research Council of Canada Riverine Water Reference Materials for Trace Metals SLRS-1, SLRS-2 and SLRS-3. New concentration values for trace and major elements in the SRWSs, traceable to the certified standards, are reported. Additional concentration values are reported for elements that were neither previously published for the SRWSs nor traceable to the certified reference materials. Robust statistical procedures were used that were insensitive to outliers. These data can be used for quality assurance/quality control purposes in analytical laboratories.