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1

Atmospheric Trace Gas Abundances and Stable Isotope Ratios via IR-LIF  

NASA Technical Reports Server (NTRS)

We propose to develop new technologies with support provided by PIDDP that will enable the in situ measurements of abundances and stable isotope ratios in important radiatively and biogenically active gases such as carbon dioxide, carbon monoxide, water, methane, nitrous oxide, and hydrogen sulfide to very high precision (0.1 per mil or better for the isotopic ratios, for example). Such measurements, impossible at present, could provide pivotal new constraints on the global (bio)geochemical budgets of these critical species, and could also be used to examine the dynamics of atmospheric transport on Mars, Titan, and other solar system bodies. We believe the combination of solid state light sources with imaging of the IR laser induced fluorescence (IR-LIF) via newly available detector arrays will make such in situ measurements possible for the first time. Even under ambient terrestrial conditions, the LIF yield from vibrational excitation of species such as water and carbon dioxide should produce emission measures well in excess of ten billion photons/sec from samples volumes of order 1 c.c. These count rates can, in principle, yield detection limits into the sub-ppt range that are required for the in situ isotopic study of atmospheric trace gases. While promising, such technologies are relatively immature, but developing rapidly, and there are a great many uncertainties regarding their applicability to in situ IR-LIF planetary studies. We therefore feel PIDDP support will be critical to developing these new tools, and propose a three-year program to combine microchip near-IR lasers with low background detection axes and state-of-the-art HgCdTe detectors developed for astronomical spectroscopy to investigate the sensitivity of IR-LIF under realistic planetary conditions, to optimize the optical pumping and filtering schemes for important species, and to apply the spectrometer to the non-destructive measurement of stable isotopes in a variety of test samples. These studies form the necessary precursors to the development of compact, lightweight stable isotope/trace gas sensors for future planetary missions.

Blake, Geoffrey A.

2004-01-01

2

Natural-abundance stable carbon isotopes of small-subunit ribosomal RNA (SSU rRNA) from Guaymas Basin (Mexico)  

NASA Astrophysics Data System (ADS)

Small-subunit ribosomal RNA (SSU rRNA) is a phylogenetically informative molecule found in all species. Because it is poorly preserved in most environments, it is a useful marker for active microbial populations. We are using the natural-abundance stable carbon isotopic composition of specific microbial groups to help identify the carbon substrates contributing to microbial biomass in a variety of marine environments. At Guaymas Basin, hydrothermal fluids interact with abundant sedimentary organic carbon to produce natural gas and petroleum. Where this reaches the sediment surface, it can support dense patches of seafloor life, including Beggiatoa mats. We report here on the stable carbon isotopic composition of SSU rRNA from a Beggiatoa mat transect, a cold background site, a warm site with high oil concentration, and a second Beggiatoa mat. The central part of the transect mat overlay the steepest temperature gradient, and was visually dominated by orange Beggiatoa. This was fringed by white Beggiatoa mat and bare, but still warm, sediment. Methane concentrations were saturating beneath the orange and white mats and at the oily site, lower beneath bare sediment, and below detection at the background site. Our initial hypotheses were that rRNA isotopic composition would be strongly influenced by methane supply, and that archaeal rRNA might be lighter than bacterial due to contributions from methanogens and anaerobic methane oxidizers. We used biotin-labeled oligonucleotides to capture Bacterial and Archaeal SSU rRNA for isotopic determination. Background-site rRNA was isotopically heaviest, and bacterial RNA from below 2 cm at the oily site was lightest, consistent with control by methane. Within the transect mat, however, the pattern was more complicated; at some sediment depths, rRNA from the mat periphery was isotopically lightest. Part of this may be due to the spatially and temporally variable paths followed by hydrothermal fluid, which can include horizontal flow. There was no consistent isotopic difference between rRNAs captured by the two probes, although RNA recoveries were too low for isotopic determinations at depths where methanogens and methane oxidizers are expected. Our prediction that rRNA stable carbon isotopic composition would correlate with methane supply was borne out by the comparison between background and mat sediments, but may be an oversimplification for sites within hydrothermal features. Future work will include the isotopic characterization of other potential carbon substrates, such as acetate. We are also investigating cold-seep sediments and brine pools in the Gulf of Mexico, where methane is significantly more 13C-depleted than at Guaymas Basin and may therefore leave a stronger imprint on microbial biomass.table carbon isotopes of rRNA captured with Bacterial and Archaeal probes at mat transect and background sites.

MacGregor, B. J.; Mendlovitz, H.; Albert, D.; Teske, A. P.

2012-12-01

3

Evaluating microbial carbon sources in Athabasca oil sands tailings ponds using natural abundance stable and radiocarbon isotopes  

NASA Astrophysics Data System (ADS)

Natural abundance stable (?13C) and radiocarbon (?14C) isotopes of phospholipid fatty acids (PLFAs) were used to evaluate the carbon sources utilized by the active microbial populations in surface sediments from Athabasca oil sands tailings ponds. The absence of algal-specific PLFAs at three of the four sites investigated, in conjunction with ?13C signatures for PLFAs that were generally within ~3 of that reported for oil sands bitumen (~ -30), indicated that the microbial communities growing on petroleum constituents were dominated by aerobic heterotrophs. The ?14C values of PLFAs ranged from -906 to -586 and pointed to a significant uptake of fossil carbon (up to ~90% of microbial carbon derived from petroleum), particularly in PLFAs (e.g., cy17:0 and cy19:0) often associated with petroleum hydrocarbon degrading bacteria. The comparatively higher levels of 14C in other, less specific PLFAs (e.g., 16:0) indicated the preferential uptake of younger organic matter by the general microbial population (~50-80% of microbial carbon derived from petroleum). Since the main carbon pools in tailings sediment were essentially 'radiocarbon dead' (i.e., no detectable 14C), the principal source for this modern carbon is considered to be the Athabasca River, which provides the bulk of the water used in the bitumen extraction process. The preferential uptake of the minor amount of young and presumably more biodegradable material present in systems otherwise dominated by recalcitrant petroleum constituents has important implications for remediation strategies. On the one hand, it implies that mining-related organic contaminants could persist in the environment long after tailings pond reclamation has begun. Alternatively, it may be that the young, labile organic matter provided by the Athabasca River plays an important role in stimulating or supporting the microbial utilization of petroleum carbon in oil sands tailings ponds via co-metabolism or priming processes. Further research needs to examine the role which priming processes play in controlling the fate of organic contaminants in Athabasca oil sands tailings ponds, such as understanding to what extent the addition of labile material may hinder or enhance microbial uptake of fossil carbon. This knowledge can be subsequently used to optimize conditions which favour natural attenuation processes in reclamation sites following mine closure.

Ahad, J. M.; Pakdel, H.

2013-12-01

4

Food Resources of Stream Macronivertebrates Determined by Natural-Abundance stable C and N Isotopes and a 15N Tracer Addition  

SciTech Connect

Trophic relationships were examined using natural-abundance {sup 13}C and {sup 15}N analyses and a {sup 15}N-tracer addition experiment in Walker Branch, a 1st-order forested stream in eastern Tennessee. In the {sup 15}N-tracer addition experiment, we added {sup 15}NH{sub 4} to stream water over a 6-wk period in early spring, and measured {sup 15}N:{sup 14}N ratios in different taxa and biomass compartments over distance and time. Samples collected from a station upstream from the {sup 15}N addition provided data on natural-abundance {sup 13}C:{sup 12}C and {sup 15}N:{sup 14}N ratios. The natural-abundance {sup 15}N analysis proved to be of limited value in identifying food resources of macroinvertebrates because {sup 15}N values were not greatly different among food resources. In general, the natural-abundance stable isotope approach was most useful for determining whether epilithon or detritus were important food resources for organisms that may use both (e.g., the snail Elimia clavaeformis), and to provide corroborative evidence of food resources of taxa for which the {sup 15}N tracer results were not definitive. The {sup 15}N tracer results showed that the mayflies Stenonema spp. and Baetis spp. assimilated primarily epilithon, although Baetis appeared to assimilate a portion of the epilithon (e.g., algal cells) with more rapid N turnover than the bulk pool sampled. Although Elimia did not reach isotopic equilibrium during the tracer experiment, application of a N-turnover model to the field data suggested that it assimilated a combination of epilithon and detritus. The amphipod Gammarus minus appeared to depend mostly on fine benthic organic matter (FBOM), and the coleopteran Anchytarsus bicolor on epixylon. The caddisfly Diplectrona modesta appeared to assimilate primarily a fast N-turnover portion of the FBOM pool, and Simuliidae a fast N-turnover component of the suspended particulate organic matter pool rather than the bulk pool sampled. Together, the natural-abundance stable C and N isotope analyses and the experimental {sup 15}N tracer approach proved to be very useful tools for identifying food resources in this stream ecosystem.

Mulholland, P. J.

2000-01-01

5

Characterizing the Spatial and Temporal Variations in Organic Carbon Abundance and Stable Isotope Ratios in Lake Sediments Containing Evidence of Prehistoric Agriculture  

NASA Astrophysics Data System (ADS)

Intra-basin spatial variability in lake sediments has the potential to limit the utility of interpretations based on the analysis of a single sediment core. We analyzed a network of five sediment cores to assess geochemical and isotopic spatial variability across a lake in southern Costa Rica. Laguna Zoncho (8.813N, 82.963W) provides an excellent opportunity to detect spatial variability because it is a small lake (0.75 ha) with a known history of prehistoric maize agriculture in its watershed. During the agricultural period (1770-570 cal BP) at Zoncho, stable carbon isotope values in the five cores average -23 V-PDB; these values increase to -27 V-PDB during the subsequent period of forest recovery. In prior work at the lake, this forest recovery was assumed to have been initiated by the Spanish Conquest about AD 1500, but our new findings suggest it may have occurred earlier and have been driven by a different set of circumstances. We attribute the more positive values during the agricultural period to a greater abundance of C4 vegetation in the watershed as the result of agricultural activity that removed native C3 forest vegetation and created fields and disturbed environments that favor C4 plants. Organic carbon contents during the agricultural period average 5 % and increase to an average of 16 % post-Conquest. Molar C/N ratios range from 13 during the agricultural period to 16 after the cessation of agriculture in the watershed. The cores may indicate a non-simultaneous end to agriculture in the watershed. Stable carbon isotope values and organic carbon contents in three of the four cores collected closer to shore contain evidence of an abrupt end of agriculture around 1000 cal. BP. In these cores, stable carbon isotope values indicate a dramatic shift from C4 to C3 inputs and a rapid increase in organic contents. The fourth core shows this shift around 700 cal. BP. The core recovered from the center of the lake records a gradual end to agriculture in the watershed from 1000 to 700 cal. BP, suggesting that the central core contains reworked material from refocusing of intra-basinal sediments. Spatial variations in organic carbon content and stable carbon isotopic values in a lake as small as Laguna Zoncho highlights the importance of core site selection.

Taylor, Z. P.; Finkelstein, D. B.; Horn, S. P.

2009-12-01

6

Colorado Plateau Stable Isotope Laboratory  

NSDL National Science Digital Library

This website, hosted by Northern Arizona University, describes stable isotopes. The site defines stable isotopes and how to measure them, and lists their research applications. Many of the advances in ecology and environmental sciences in the past decade have relied on stable isotopes.

Colorado Plateau Stable Isotope Laboratory (CPSIL); University, Northern A.

7

Stable Isotope Enrichment Capabilities at ORNL  

SciTech Connect

The Oak Ridge National Laboratory (ORNL) and the US Department of Energy Nuclear Physics Program have built a high-resolution Electromagnetic Isotope Separator (EMIS) as a prototype for reestablishing a US based enrichment capability for stable isotopes. ORNL has over 60 years of experience providing enriched stable isotopes and related technical services to the international accelerator target community, as well as medical, research, industrial, national security, and other communities. ORNL is investigating the combined use of electromagnetic and gas centrifuge isotope separation technologies to provide research quantities (milligram to several kilograms) of enriched stable isotopes. In preparation for implementing a larger scale production facility, a 10 mA high-resolution EMIS prototype has been built and tested. Initial testing of the device has simultaneously collected greater than 98% enriched samples of all the molybdenum isotopes from natural abundance feedstock.

Egle, Brian [ORNL; Aaron, W Scott [ORNL; Hart, Kevin J [ORNL

2013-01-01

8

Monsoon Variability In The Western Arabian Sea During Last 10,000 Years BP: A Planktic Foraminiferal Abundances And It's Stable Isotope Records  

NASA Astrophysics Data System (ADS)

: The western Arabian Sea responds to the southwest monsoon winds by upwelling colder and nutrient rich waters from the deeper layers, causing a reduction in the sea surface temperature and enhanced biological productivity. A number of paleoclimatic studies have been carried out in this region to elucidate past monsoon variability (Sirocco et al., 1993; Gupta et al, 2003; Tiwari, 2005; Saher et.al.; 2007). Globigerina bulloides, a planktic foraminiferal species normally inhabiting surface ocean waters in temperate latitudes ( Be and Tolderlund , 1977) also becomes abundant at tropical latitudes upwelling occurs, and in these cases its abundance can exceed considerably. The conspicuous fluctuation in the abundance of Gg.bulloides during upwelling and non upwelling intervals is established through several studies ( Thiede and Junger, 1980, Gupta et al, 2003) This robust relation has been used as a proxy for wind velocity at several different times in the past in the Arabian Sea (Anderson et.al., 2002). A significant result from some of these centennially resolved Holocene records is declining abundance of Globigerina bulloides which is paralleled by reduced insolation record and this has been inferred as declining strength of Asian Monsoon. We are presenting here the data from the core SS4018 from near the Gulf of Aden, Western Arabian Sea taken at a water depth of 2830 m, precisely dated by the radiocarbon method using Accelerator Mass Spectrometry on planktonic foraminiferal separates. We have carried out the planktic foraminiferal census counts for each sample to know the relative abundance of key species. In addition to this, we have also employed multi- proxy approach such as oxygen and carbon isotopes of planktic foraminiferal tests, TOC, CaCO3 (%) to strengthen our interpretation and also to understand the relationships amongst the proxies themselves. Abundance of the key planktic foraminiferal species and other proxy records reveal at least 3 major climatic events (M-1, M-2 and M-3) during the last 10,000yrs. The earliest one (M-1) is a major decline in the upwelling intensity during 7.9.-5.6 kyBP. We have observed the lowest abundance of upwelling indicator species (UIS), it goes down from 70(%) to 30(%), mixed dweller (MD) and thermocline dweller (TD) species were showing their maximum abundance and at that time Organic carbon (OC) value revealed the lowest amount. Oxygen stable isotope records were also suggesting the same results. The second event at 5.5-2.2 kyBP (M-2) corresponds to average upwelling. We have observed the 2-3 high peaks of (UIS), on average UIS were showing around 50-55(%) of their abundance during this period, thus we have concluded the moderate intensity of SWM winds during M-2. The third event at last 2ky (M-3), decreasing trend in the strength of the SWM has been observed on the basis of sharp decline in the abundance of UIS and OC amount. For this interval, we have observed the increasing trend in the MD and TD planktic foraminiferal species.

Singh, A. K.; Tiwari, M.; Sinha, D. K.; Ramesh, R.

2007-12-01

9

Lithium Isotopic Abundances in Stars  

NASA Astrophysics Data System (ADS)

The Li isotope ratio, 6Li/7Li, in stars can be determined from the isotopic shift in the Li I 670.8 nm resonance line. Because of the small effect this however requires truly precision spectroscopy: spectral resolving power R ? 105 and S/N ? 500. In this review we discuss the method and what one can learn from Li isotopic abundances in terms of Big-Bang nucleosynthesis, cosmic ray production of Li, stellar structure, and planet formation. Some instrumental problems and the need for new instrumentation are briefly discussed.

Nissen, Poul Erik; Asplund, Martin

10

Stable Isotope Research Pool Inventory.  

National Technical Information Service (NTIS)

This report contains a listing of electromagnetically separated stable isotopes which are available at the Oak Ridge National Laboratory for distribution for non-destructive research use on a loan basis. This inventory includes all samples of stable isoto...

1985-01-01

11

ISOTOPIC TITANIUM ABUNDANCES IN LOCAL M DWARFS  

SciTech Connect

Relative abundances of the five stable isotopes of titanium ({sup 46}Ti to {sup 50}Ti) are measured for 11 M dwarfs belonging to the thin disk (four stars), thick disk (three stars), the halo (one star), and either the thick or the thin disk (three stars). Over the metallicity range of the sample (-1< [Fe/H] <0), the isotopic ratios are approximately constant at the solar system ratios. There is no discernible difference between the isotopic ratios for thin and thick disk stars. Isotopic ratios are in fair accord with recent calculations of Galactic chemical evolution despite the fact that such calculations underpredict [Ti/Fe] by about 0.4 dex at all metallicities.

Chavez, Joy [Department of Astronomy, University of Texas, 1 University Station, C1400 Austin, TX 78712-0259 (United States); Lambert, David L. [McDonald Observatory, University of Texas at Austin, 1 University Station, C1402 Austin, TX 78712-0259 (United States)], E-mail: jchavez@astro.as.utexas.edu, E-mail: dll@astro.as.utexas.edu

2009-07-10

12

Using PLFA Biomarkers and Natural Abundance Stable and Radiocarbon Isotopes to Characterize the Microbial Ecology and Metabolism of Methane Cycling  

NASA Astrophysics Data System (ADS)

Methane generated in the subsurface is a major source of atmospheric CH4, but its release is mitigated by CH4-oxidizing bacteria (methanotrophs). Therefore, it is important to understand the ecology of methanotroph communities in various environments. Phospholipid fatty acid (PLFA) analyses are a particularly useful method for characterizing these communities for two reasons: (1) Many type I and II methanotrophs produce specific PLFA biomarkers that can be used to estimate their populations, and (2) because CH4 is often very depleted in 13C and sometimes 14C, natural abundance ?13CPLFA and ?14CPLFA values can be used to trace the flow of CH4- derived carbon through microbial ecosystems. We used these tools to evaluate the role of methanotrophs in carbon flow in three different environments: (1) a soil column overlying a coal bed methane (CBM) seep in southwest CO, and pristine, oligotrophic groundwaters within (2) sedimentary and (3) granitic host rocks in Japan. In the soil column impacted by CBM seepage, concentrations of the biomarker PLFAs for type I (16:1?8cis) and type II (18:1?8cis) methanotrophs were as high as 13 and 18 nmoles (g dry soil)-1, respectively. Depth profiles of methanotroph PLFA concentrations varied over different sampling dates indicating dynamic populations. ?13CPLFA values of the CBM soils (-25.1 to - 66.9) were substantially more negative than those for the control soil (-14.5 to -32.5) indicating that CBM is an important carbon source for the CBM-impacted soil microbial community. ?14CPLFA values (-351 to -936) indicate the importance of 14C-dead CBM as a carbon source to the microbial communities, contributing 32 to 66% of total carbon in PLFA structures isolated from shallow soils and 67 to 97% for those isolated from deeper soils. The biomarker for type II methanotrophs, comprised 3 and 18% of total PLFAs in sedimentary and granitic groundwaters, respectively. The ?14C values determined for type II methanotroph PLFAs in the sedimentary (- 861) and granite (-867) waters were very similar to the ?14C values of dissolved inorganic carbon (DIC) in each water (ca -850) suggesting that type II methanotrophs ultimately derive all of their carbon from DIC. In contrast, ?13C values of type II PLFAs in the sedimentary (- 93) and granite (-60) waters indicate that these organisms use different carbon assimilation schemes in each environment. These studies show the utility of PLFA biomarkers and ?13CPLFA and ?14CPLFA values to characterize the in situ metabolisms of methanotrophic bacteria and overall CH4 recycling in diverse environments.

Mills, C. T.; Mandernack, K. W.; Slater, G. F.; Dias, R. F.

2008-12-01

13

STABLE ISOTOPES IN PLANT ECOLOGY  

Microsoft Academic Search

? Abstract The use of stable isotope techniques in plant ecological research has grown steadily during the past two decades. This trend will continue as investigators realize that stable isotopes can serve as valuable nonradioactive tracers and nondestruc- tive integrators of how plants today and in the past have interacted with and responded to their abiotic and biotic environments. At

Todd E. Dawson; Stefania Mambelli; Agneta H. Plamboeck; Pamela H. Templer; Kevin P. Tu

2002-01-01

14

Stable Isotopes in Foraminiferal Carbonate  

Microsoft Academic Search

Analyses of stable oxygen and carbon isotopes from foraminiferal shells have played a pivotal role in palaeoceanography since Emiliani (1955) interpreted the isotopic record from deep-sea cores as a series of Pleistocene climate\\/temperature cycles. Oxygen isotope stratigraphy has become a global correlation tool, and an established dating tool. The primary ice-volume control on (benthic) oxygen isotope records has led to

Steve Cooke; Eelco J. Rohling

15

Millimeter-scale variations of stable isotope abundances in carbonates from banded iron-formations in the Hamersley Group of Western Australia  

NASA Technical Reports Server (NTRS)

Several diamond drill cores from formations within the Hamersley Group of Western Australia have been studied for evidence of short-range variations in the isotopic compositions of the carbonates. For a set of 32 adjacent microbands analyzed in a specimen from the Marra Mamba Iron Formation, carbon isotope compositions of individual microbands ranged from -2.8 to -19.8 per mil compared to PDB and oxygen isotope compositions ranged from 10.2 to 20.8 per mil compared to SMOW. A pattern of alternating abundances was present, with the average isotopic contrasts between adjacent microbands being 3.0 per mil for carbon and 3.1 per mil for oxygen. Similar results were obtained for a suite of 34 microbands (in four groups) from the Bruno's Band unit of the Mount Sylvia Formation. Difficulties were experienced in preparing samples of single microbands from the Dales Gorge Member of the Brockman Iron Formation, but overall isotopic compositions were in good agreement with values reported by previous authors. Chemical analyses showed that isotopically light carbon and oxygen were correlated with increased concentrations of iron. The preservation of these millimeter-scale variations in isotopic abundances is interpreted as inconsistent with a metamorphic origin for the isotopically light carbon in the BIF carbonates. A biological origin is favored for the correlated variations in 13C and Fe, and it is suggested that the 13C-depleted carbonates may derive either from fermentative metabolism or from anaerobic respiration. A model is presented in which these processes occur near the sediment-water interface and are coupled with an initial oxidative precipitation of the iron.

Baur, M. E.; Hayes, J. M.; Studley, S. A.; Walter, M. R.

1985-01-01

16

Millimeter-scale variations of stable isotope abundances in carbonates from banded iron-formations in the Hamersley Group of Western Australia.  

PubMed

Several diamond drill cores from formations within the Hamersley Group of Western Australia have been studied for evidence of short-range variations in the isotopic compositions of the carbonates. For a set of 32 adjacent microbands analyzed in a specimen from the Marra Mamba Iron Formation, carbon isotope compositions of individual microbands ranged from -2.8 to -19.8 per mil compared to PDB and oxygen isotope compositions ranged from 10.2 to 20.8 per mil compared to SMOW. A pattern of alternating abundances was present, with the average isotopic contrasts between adjacent microbands being 3.0 per mil for carbon and 3.1 per mil for oxygen. Similar results were obtained for a suite of 34 microbands (in four groups) from the Bruno's Band unit of the Mount Sylvia Formation. Difficulties were experienced in preparing samples of single microbands from the Dales Gorge Member of the Brockman Iron Formation, but overall isotopic compositions were in good agreement with values reported by previous authors. Chemical analyses showed that isotopically light carbon and oxygen were correlated with increased concentrations of iron. The preservation of these millimeter-scale variations in isotopic abundances is interpreted as inconsistent with a metamorphic origin for the isotopically light carbon in the BIF carbonates. A biological origin is favored for the correlated variations in 13C and Fe, and it is suggested that the 13C-depleted carbonates may derive either from fermentative metabolism or from anaerobic respiration. A model is presented in which these processes occur near the sediment-water interface and are coupled with an initial oxidative precipitation of the iron. PMID:11539027

Baur, M E; Hayes, J M; Studley, S A; Walter, M R

1985-01-01

17

Iron stable isotopes: beyond biosignatures  

Microsoft Academic Search

The stable isotope geochemistry of Fe has attracted intense interest in the past five years. This interest was originally motivated by the possible use of Fe isotopes in biosignature applications, particularly in sediments from the ancient Earth or Mars. This application is still being developed, with particular attention to fractionation mechanisms. Understanding such mechanisms should also provide new insights into

A. D. Anbar

2004-01-01

18

Environmental and biomedical applications of natural metal stable isotope variations  

USGS Publications Warehouse

etal stable isotopes are now being used to trace metal contaminants in the environment and as indicators of human systemic function where metals play a role. Stable isotope abundance variations provide information about metal sources and the processes affecting metals in complex natural systems, complementing information gained from surrogate tracers, such as metal abundance ratios or biochemical markers of metal metabolism. The science is still in its infancy, but the results of initial studies confirm that metal stable isotopes can provide a powerful tool for forensic and biomedical investigations.

Bullen, T. D.; Walczyk, T.

2009-01-01

19

Purification, recovery, and laser-driven fluorination of silicon from dissolved and particulate silica for the measurement of natural stable isotope abundances.  

PubMed

A procedure for the purification, recovery, and determination of isotopic abundances of silicon from biogenic and lithogenic particulate matter and dissolved silicic acid is reported. Purification involves the reaction of acid molybdate with dissolved silicon in natural waters or that produced by the dissolution of particulate silica by hydrofluoric acid. The resulting silicomolybdic acid is then quantitatively precipitated by reaction with triethylamine hydrochloride. The silicon is recovered as silicon dioxide through stepwise combustion of the dried precipitate. Fluorination of the product for isotopic analysis is accomplished by laser heating under pure fluorine generated by the decomposition of a fluorine-based salt. The resulting silicon tetrafluoride is separated from hydrogen fluoride and other fluorination byproducts cryogenically using a variable-temperature cold trap. Yields for silicon recovery are 99.9% for precipitation and greater than 95% for the purification/fluorination procedure. Reproducibility of the isotopic composition for pure quartz granules processed through the procedure is 0.1 for ?(30)Si. PMID:21619245

De La Rocha, C L; Brzezinski, M A; Deniro, M J

1996-11-01

20

Stable Isotopes and M&Ms  

NSDL National Science Digital Library

Students are often confused by the concepts of stable isotope signatures and conventional notation. This activity is designed to introduce students to the del notation (isotopic signature), fractionation, and end member mixing of stable isotopes using familiar objects disguised as isotopes. The activity does not explain the physical manifestation of why isotopic fractionation occurs, but does explain the concepts that one easily observes when interpreting stable isotope data sets.

De Jesus, Roman

21

Absolute isotopic abundances of TI in meteorites  

NASA Astrophysics Data System (ADS)

The absolute isotope abundance of Ti has been determined in Ca-Al-rich inclusions from the Allende and Leoville meteorites and in samples of whole meteorites. The absolute Ti isotope abundances differ by a significant mass dependent isotope fractionation transformation from the previously reported abundances, which were normalized for fractionation using 46Ti/48Ti. Therefore, the absolute compositions define distinct nucleosynthetic components from those previously identified or reflect the existence of significant mass dependent isotope fractionation in nature. The authors provide a general formalism for determining the possible isotope compositions of the exotic Ti from the measured composition, for different values of isotope fractionation in nature and for different mixing ratios of the exotic and normal components.

Niederer, F. R.; Papanastassiou, D. A.; Wasserburg, G. J.

1985-03-01

22

Stable Carbon and Nitrogen Isotopic  

Microsoft Academic Search

The perennially ice-covered lakes in the McMurdo Dry Valleys, Antarctica, are part of the coldest and driest ecosystem on earth. To understand lacustrine carbon and nitrogen cycling in this end-member ecosystem, and to define paleolimnological proxies for ice-covered lakes, we measured the stable carbon and nitrogen isotopic composition of particulate organic matter (POM) and benthic organic matter (BOM) within the

Jennifer Lawson; PETER T. DORAN; Fabien Kenig; DAVID J. DES MARAIS; JOHN C. PRISCU

2004-01-01

23

Climatic/Hydrologic Oscillations since 155,000 yr B.P. at Owens Lake, California, Reflected in Abundance and Stable Isotope Composition of Sediment Carbonate  

USGS Publications Warehouse

Sediment grain size, carbonate content, and stable isotopes in 70-cm-long (???1500-yr) channel samples from Owens Lake core OL-92 record many oscillations representing climate change in the eastern Sierra Nevada region since 155,000 yr B.P. To first order, the records match well the marine ??18O record. At Owens Lake, however, the last interglaciation appears to span the entire period from 120,000 to 50,000 yr B.P., according to our chronology, and was punctuated by numerous short periods of wetter conditions during an otherwise dry climate. Sediment proxies reveal that the apparent timing of glacial-interglacial transitions, notably the penultimate one, is proxy-dependent. In the grain-size and carbonate-content records this transition is abrupt and occurs at ??? 120,000 yr B.P. In contrast, in the isotopic records the transition is gradual and occurs between 145,000 and 120,000 yr B. P. Differences in timing of the transition are attributed to variable responses by proxies to climate change. ?? 1997 University of Washington.

Menking, K. M.; Bischoff, J. L.; Fitzpatrick, J. A.; Burdette, J. W.; Rye, R. O.

1997-01-01

24

Stable Isotope Signatures for Microbial Forensics  

Microsoft Academic Search

The isotopic distribution of the atoms composing the molecules of microorganisms is a function of the substrates used by the organisms. The stable isotope content of an organism is fixed so long as no further substrate consumption and biosynthesis occurs, while the radioactive isotopic content decays over time. The distribution of stable isotopes of C, N, O and H in

Helen W

2012-01-01

25

Chlorine stable isotopes in sedimentary systems: does size matter?  

NASA Technical Reports Server (NTRS)

Stable isotope abundances vary because of size differences. The chlorine stable isotope system was one of the first described theoretically, but had a slow, disappointment strewn development, relative to other elements. Method improvement gave only small, but significant, differences in compositions of geological materials. Eventually, brines and groundwater chlorides gave larger differences. Physical processes like diffusion and adsorption, probably are the main controls of groundwater compositions. Recent work on anthropogenic groundwater contaminants shows variations resulting from manufacturing processes; implying possibilities of tracing sources.

Coleman, Max

2004-01-01

26

Silicon Reference Materials Certified for Isotope Abundances.  

National Technical Information Service (NTIS)

In a series of gas mass-spectrometric measurements performed near the highest attainable accuracy, samples from two highly homogeneous batches of silicon crystals and silica powder were compared directly with a synthetic mixture of the three stable isotop...

S. Valkiers P. De Bievre G. Lenaers H. S. Peiser

1991-01-01

27

Uses of stable isotopes in fish ecology  

EPA Science Inventory

Analyses of fish tissues (other than otoliths) for stable isotope ratios can provide substantial information on fish ecology, including physiological ecology. Stable isotopes of nitrogen and carbon frequently are used to determine the mix of diet sources for consumers. Stable i...

28

Stable Isotope Inventory Requirements and Enrichment Capabilities.  

National Technical Information Service (NTIS)

The electromagnetic isotope enrichment program established in 1945 has since then continued to provide enriched stable, actinide, and selected radioactive isotopes. These unique materials used in research and medicine and for industrial applications are m...

W. A. Bell J. G. Tracy

1985-01-01

29

Stable Isotope Group 1981 Progress Report.  

National Technical Information Service (NTIS)

Geothermal studies were reported on the Tauhara, Wairakei, Orakeikorako and Mokai areas. We assisted the two N.Z. geothermal consultant companies with isotope analyses and the Geothermal Institute with lectures on stable isotope aspects of the diploma cou...

M. K. Stewart

1982-01-01

30

Stable isotope deltas: tiny, yet robust signatures in nature.  

PubMed

Although most of them are relatively small, stable isotope deltas of naturally occurring substances are robust and enable workers in anthropology, atmospheric sciences, biology, chemistry, environmental sciences, food and drug authentication, forensic science, geochemistry, geology, oceanography, and paleoclimatology to study a variety of topics. Two fundamental processes explain the stable isotope deltas measured in most terrestrial systems: isotopic fractionation and isotope mixing. Isotopic fractionation is the result of equilibrium or kinetic physicochemical processes that fractionate isotopes because of small differences in physical or chemical properties of molecular species having different isotopes. It is shown that the mixing of radioactive and stable isotope end members can be modelled to provide information on many natural processes, including (14)C abundances in the modern atmosphere and the stable hydrogen and oxygen isotopic compositions of the oceans during glacial and interglacial times. The calculation of mixing fractions using isotope balance equations with isotope deltas can be substantially in error when substances with high concentrations of heavy isotopes (e.g. (13)C, (2)H, and (18)O ) are mixed. In such cases, calculations using mole fractions are preferred as they produce accurate mixing fractions. Isotope deltas are dimensionless quantities. In the International System of Units (SI), these quantities have the unit 1 and the usual list of prefixes is not applicable. To overcome traditional limitations with expressing orders of magnitude differences in isotope deltas, we propose the term urey (symbol Ur), after Harold C. Urey, for the unit 1. In such a manner, an isotope delta value expressed traditionally as-25 per mil can be written as-25mUr (or-2.5cUr or-0.25dUr; the use of any SI prefix is possible). Likewise, very small isotopic differences often expressed in per meg 'units' are easily included (e.g. either+0.015 or+15 per meg can be written as+15?Ur. PMID:22462621

Brand, Willi A; Coplen, Tyler B

2012-09-01

31

Measurement of isotope abundance variations in nature by gravimetric spiking isotope dilution analysis (GS-IDA).  

PubMed

Subtle variations in the isotopic composition of elements carry unique information about physical and chemical processes in nature and are now exploited widely in diverse areas of research. Reliable measurement of natural isotope abundance variations is among the biggest challenges in inorganic mass spectrometry as they are highly sensitive to methodological bias. For decades, double spiking of the sample with a mix of two stable isotopes has been considered the reference technique for measuring such variations both by multicollector-inductively coupled plasma mass spectrometry (MC-ICPMS) and multicollector-thermal ionization mass spectrometry (MC-TIMS). However, this technique can only be applied to elements having at least four stable isotopes. Here we present a novel approach that requires measurement of three isotope signals only and which is more robust than the conventional double spiking technique. This became possible by gravimetric mixing of the sample with an isotopic spike in different proportions and by applying principles of isotope dilution for data analysis (GS-IDA). The potential and principle use of the technique is demonstrated for Mg in human urine using MC-TIMS for isotopic analysis. Mg is an element inaccessible to double spiking methods as it consists of three stable isotopes only and shows great potential for metabolically induced isotope effects waiting to be explored. PMID:23419016

Chew, Gina; Walczyk, Thomas

2013-04-01

32

Substitution of stable isotopes in Chlorella  

NASA Technical Reports Server (NTRS)

Replacement of biologically important isotopes in the alga Chlorella by corresponding heavier stable isotopes produces increasingly greater deviations from the normal cell size and changes the quality and distribution of certain cellular components. The usefulness of isotopically altered organisms increases interest in the study of such permuted organisms.

Flaumenhaft, E.; Katz, J. J.; Uphaus, R. A.

1969-01-01

33

Stable Isotope Signatures for Microbial Forensics  

SciTech Connect

The isotopic distribution of the atoms composing the molecules of microorganisms is a function of the substrates used by the organisms. The stable isotope content of an organism is fixed so long as no further substrate consumption and biosynthesis occurs, while the radioactive isotopic content decays over time. The distribution of stable isotopes of C, N, O and H in heterotrophic microorganisms is a direct function of the culture medium, and therefore the stable isotope composition can be used to associate samples with potential culture media and also with one another. The 14C content depends upon the 14C content, and therefore the age, of the organic components of the culture medium, as well as on the age of the culture itself. Stable isotope signatures can thus be used for sample matching, to associate cultures with specific growth media, and to predict characteristics of growth media.

Kreuzer, Helen W.

2012-01-03

34

Stable isotopes and biomarkers in microbial ecology  

Microsoft Academic Search

The use of biomarkers in combination with stable isotope analysis is a new approach in microbial ecology and a number of papers on a variety of subjects have appeared. We will first discuss the techniques for analysing stable isotopes in biomarkers, primarily gas chromatography-combustion-isotope ratio mass spectrometry, and then describe a number of applications in microbial ecology based on degreesC.

H. T. S. Boschker; J. J. Middelburg

2002-01-01

35

Stable Vanadium Isotope Fractionation at High Temperatures  

NASA Astrophysics Data System (ADS)

Vanadium is a redox sensitive transition metal existing in multiple valence states at terrestrial conditions. Stable vanadium isotopes (reported as ?51V in % relative to an Alfa Aesar standard [1]) are a potentially powerful tracer of oxidation-reduction processes. However, the determination of ?51V is analytically challenging, primarily due to the extreme abundance ratio between the only two stable isotopes (51V/50V ~ 400) and, also, significant isobaric interferences of 50Ti and 50Cr on the minor 50V isotope. We have developed the first method able to determine ?51V to a precision (2 s.d. ~ 0.15%, [1,2]) that enables application of this isotope system to geological processes. To usefully investigate high temperature processes using vanadium isotopes, knowledge of the isotope composition and range of values present in the ambient mantle is required. Here we discuss the first ?51V measured in igneous materials encompassing peridotites, MORB, and primitive mantle-derived melts such as picrites. This first dataset provides a preliminary reconnaissance of the magnitude of natural fractionation. We find little isotope fractionation in suites of peridotites and MORB (< 0.5 %). However, the small but analytically significant variation appears to be related to secondary processes, with extremely altered peridotites consistently displaying slightly heavier isotope compositions. We find no resolvable ?51V variation between fresh MORB glass and fresh peridotite. Intriguingly, a suite of subduction-related peridotites from the Mariana forearc, previously characterized for fO2 [3], do not display the predicted co-variation between ?51V and fO2, but instead also have compositions identical to MORB glass. This nominally supports recent indications that there is limited difference in the oxygen fugacity of the MORB source and the subarc mantle wedge [e.g., 4, 5]. Finally, we observe large ?51V variations (~ 2 %) in a suite of evolving lavas from Hekla volcano, Iceland, which produces eruptive material with a wide range of SiO2 from a cogenetic source. The ?51V of Hekla lavas are well correlated with indices of differentiation such as MgO and SiO2, suggesting that processes such as fractional crystallization may be a fundamental cause of high temperature ?51V fractionation. This nascent dataset provides a first glimpse into the magnitude of vanadium isotope fractionation that may be expected at high temperatures. The presence of significant isotope variation outside of analytical precision in these materials bodes well for the use of ?51V to address a variety of broad scale questions in high temperature planetary processes. [1] Nielsen, S.G., Prytulak, J., Halliday, A.N. 2011. Geost. Geoanal. Res., in press. [2] Prytulak, J., Nielsen, S.G., Halliday, A.N. 2011. Geost. Geoanal. Res., in press. [3] Parkinson and Pearce, 1998. Journal of Petrology, 39, 1577-1618. [4] Lee et al., 2005. Journal of Petrology, 46, 2313-2336. [5] Cottrell and Kelley, 2011. Earth and Planetary Sciences Letters, 305, 270-282.

Prytulak, J.; Parkinson, I. J.; Savage, P. S.; Nielsen, S. G.; Halliday, A. N.

2011-12-01

36

Stable isotope dynamics in elasmobranch fishes  

Microsoft Academic Search

Carbon and nitrogen stable isotope analyses have improved our understanding of food webs and movement patterns of aquatic\\u000a organisms. These techniques have recently been applied to diet studies of elasmobranch fishes, but isotope turnover rates\\u000a and isotope diettissue discrimination are still poorly understood for this group. We performed a diet switch experiment on\\u000a captive sandbar sharks (Carcharhinus plumbeus) as a

John M. LoganMolly; Molly E. Lutcavage

2010-01-01

37

Stable Isotope Ratios: Hurricane Olivia  

Microsoft Academic Search

The oxygen and hydrogen isotopic compositions of rains from HurricaneOlivia (1994) in the eastern Pacific were measured. The rains werecollected on 24 and 25 September during airplane flights conducted at anelevation of 3 km. Hurricane Olivia peaked in intensity to a category-4storm between the two dates. Isotope ratios of rains from HurricaneOlivia were markedly lower (d 18O = 13.9to 28.8)

James R. Lawrence; Stanley David Gedzelman; John Gamache; Michael Black

2002-01-01

38

Resources on Isotopes: Fundamentals of Stable Isotope Geochemistry  

NSDL National Science Digital Library

This is a brief review of some of the fundamentals of stable isotope geochemistry, including definitions, terminology, basic principles, standards, and guidelines on reporting data. Users can follow the link on the top right for the periodic table and read about the isotopic systems of several dozen elements.

39

Isotopic abundance ratios in interstellar carbon monosulfide  

SciTech Connect

A survey of the relative abundances of the isotopic species, /sup 12/C/sup 32/S, /sup 12/C/sup 34/S, and /sup 13/C/sup 32/S has been made in 14 dense molecular clouds through observations of the J=3-1 rotational transitions at 3 mm. The abundance ratio, (/sup 13/C/sup 32/S)/(/sup 12/C/sup 34/S), is found to be 1.9 times greater in the galactic center sources than in the galactic disk sources. The average ratio for the galactic disk sources is 0.35 +- 0.10 where the quoted error is the rms of the source-to-source fluctuations. The average disk value for (/sup 13/C)/(/sup 12/C) is 0.015, if (/sup 32/S)/(/sup 34/S) is terrestrial. No evidence is found for a systematic variation of the ratio within the disk itself. Terrestrial sulfur abundances would imply that either the observations in CS are spatially unresolved or the kinetic temperature for CS is lower than that for CO. Beam dilution factors are derived for the sources studied. In addition, values for the molecular hydrogen densities and CS fractional abundances are obtained for these sources.

Frerking, M.A.; Wilson, R.W.; Linke, R.A.; Wannier, P.G.

1980-08-15

40

Measuring In Vivo Ureagenesis With Stable Isotopes  

PubMed Central

Stable isotopes have been an invaluable adjunct to biomedical research for more than 70 years. Indeed, the isotopic approach has revolutionized our understanding of metabolism, revealing it to be an intensely dynamic process characterized by an unending cycle of synthesis and degradation. Isotopic studies have taught us that the urea cycle is intrinsic to such dynamism, since it affords a capacious mechanism by which to eliminate waste nitrogen when rates of protein degradation (or dietary protein intake) are especially high. Isotopes have enabled an appreciation of the degree to which ureagenesis is compromised in patients with urea cycle defects. Indeed, isotopic studies of urea cycle flux correlate well with the severity of cognitive impairment in these patients. Finally, the use of isotopes affords an ideal tool with which to gauge the efficacy of therapeutic interventions to augment residual flux through the cycle.

Yudkoff, Marc; Mew, Nicholas Ah; Daikhin, Yevgeny; Horyn, Oksana; Nissim, Ilana; Nissim, Itzhak; Payan, Irma; Tuchman, Mendel

2010-01-01

41

Availability of Enriched Stable Isotopes: Present Status and Future Prospects.  

National Technical Information Service (NTIS)

The Electromagnetic Isotope Enrichment Facility (EMIEF) is currently used to produce 225 enriched stable isotopes of 50 elements. Among these are included most of the known elements with stable isotopes except for the noble gases, certain light elements, ...

R. W. Hoff

1986-01-01

42

Uncertainty in source partitioning using stable isotopes  

Microsoft Academic Search

Stable isotope analyses are often used to quan- tify the contribution of multiple sources to a mixture, such as proportions of food sources in an animal's diet, or C3 and C4 plant inputs to soil organic carbon. Linear mixing models can be used to partition two sources with a single isotopic signature (e.g., ?13C) or three sources with a second

Donald L. Phillips; Jillian W. Gregg

2001-01-01

43

In-gel stable isotope labeling for relative quantification using mass spectrometry  

Microsoft Academic Search

Although differences in protein staining intensity can often be visualized by difference gel electrophoresis, abundant proteins can obscure less abundant proteins, and quantification of post-translational modifications is difficult. We present a protocol for quantifying changes in the abundance of a specific protein or changes in specific modifications of a protein using in-gel stable isotope labeling. In this protocol protein extracts

Xiang Zhang; Bin Zheng; Lisa A Maroney; Heather R Christofk; Ning Wu; Lewis C Cantley; John M Asara

2006-01-01

44

Heavy Stable Isotopes: From Exceptional to Expected  

NASA Astrophysics Data System (ADS)

Less than a decade ago, the stable isotope geochemistry of transition metals and other "heavy" elements was a highly specialized niche confined to a few seemingly exceptional elements. This situation was transformed by the development and refinement of MC-ICP-MS techniques, particularly in the last five years. Measurable stable isotope variations turn out to be ubiquitous across the periodic table, from Li to Hg. It is now safe to assume that the isotopic composition of any element with two or more stable isotopes is measurably variable. What was once exceptional is now expected. Among the first of these new systems to be explored were Fe and Mo isotopes. A number of lessons emerging from this work can be applied to the development of other isotope systems. Most important is that initial expectations are often wrong. For example, based on their environmental chemistries it was expected that redox reactions should produce some of the largest isotope effects for both elements. In the case of Fe, theoretical and experimental studies converge to convincingly indicate that a fractionation of ~ 1.5 /amu occurs between Fe(III) and Fe(II) aquo complexes at equilibrium (e.g., Welch et al., 2003; Anbar et al., 2005). Consistent with these findings, most natural variations of are < 1.5 /amu (e.g., Johnson et al., 2004). This redox-related fractionation is at the heart of emerging interpretations of variations in the isotopic composition of Fe and their application to understanding ancient ocean redox (e.g., Dauphas et al., 2004; Rouxel et al., 2005). In contrast, Mo isotope variations turn out to be controlled only indirectly by redox conditions. Instead, one of the most important Mo isotope effects in the environment appears to be a fractionation of ~ 1 /amu during adsorption of Mo to Mn-oxides (Barling et al., 2001; Siebert et al., 2003). This fractionation has been reproduced in the laboratory (Barling and Anbar, 2004) and appears to be an equilibrium isotope effect unrelated to Mo redox chemistry. Because the extent of Mn-oxide deposition on the seafloor is a function of ocean oxygenation, Mo isotopes are nevertheless emerging as a powerful ocean redox proxy (Arnold et al., 2004). Collectively, these and other findings demonstrate that MC-ICP-MS analyses open the door to rich new research areas, particularly when analyses of natural samples are combined with laboratory experiments and computational predictions to gain insight into fractionation mechanisms.

Anbar, A.

2006-12-01

45

Calculation of substrate flux using stable isotopes  

SciTech Connect

The use of stable isotope tracers to calculate substrate kinetics in humans is favored over the use of radioactive isotopes because of their greater safety and versatility. However, potential complications not met when dealing with radioactive tracers are caused (1) the natural occurrence of the stable isotope used as a tracer and (2) the necessity to administer the tracer in an amount that cannot be treated as massless. The authors therefore found it desirable to derive a theoretically valid equation for calculating the rate of appearance, R{sub a}, of a substrate under steady-state conditions using a stable isotope tracer. This theoretically valid equation yields results that differ from those of the equations conventionally used to calculate (endogenous) R{sub a} in steady state. Quantitative determination of the error in one of these equations revealed that for tracers commonly used in metabolic studies the error is negligible, whereas the error made in the other equation is likely to be quite high in commonly encountered situations. Finally, to allow for proper use of different definitions of isotopic enrichment that have arisen from practical considerations, they use the results derived above to determine valid equations for R{sub a} appropriate to the two prevalent definitions.

Rosenblatt, J.; Wolfe, R.R. (Univ. of Texas Medical Branch, Galveston (USA))

1988-04-01

46

UNCERTAINTY IN SOURCE PARTITIONING USING STABLE ISOTOPES  

EPA Science Inventory

Stable isotope analyses are often used to quantify the contribution of multiple sources to a mixture, such as proportions of food sources in an animal's diet, C3 vs. C4 plant inputs to soil organic carbon, etc. Linear mixing models can be used to partition two sources with a sin...

47

Production of stable isotopes utilizing the plasma separation process  

NASA Astrophysics Data System (ADS)

A plasma separation process (PSP) is being operated at Theragenics Corporation's , Oak Ridge, TN, facility for the enrichment of stable isotopes. The PSP utilizes ion cyclotron mass discrimination to separate isotopes on a relatively large scale. With a few exceptions, nearly any metallic element could be processed with PSP. Output isotope enrichment factor depends on natural abundance and mass separation and can be fairly high in some cases. The Theragenics PSP facility is believed to be the only such process currently in operation. This system was developed and formerly operated under the US Department of Energy Advanced Isotope Separation program. Theragenics also has a laboratory at the PSP site capable of harvesting the isotopes from the process and a mass spectrometer system for analyzing enrichment and product purity. Since becoming operational in 2002, Theragenics has utilized the PSP to separate isotopes of several elements including: dysprosium, erbium, gadolinium, molybdenum and nickel. Currently, Theragenics is using the PSP for the separation of 102Pd, which is used as precursor for the production of 103Pd. The 103Pd radioisotope is the active ingredient in TheraSeed , which is used in the treatment of early stage prostate cancer and being investigated for other medical applications. New industrial, medical and research applications are being investigated for isotopes that can be enriched on the PSP. Pre-enrichment of accelerator or reactor targets offers improved radioisotope production. Theragenics operates 14 cyclotrons for proton activation and has access to HFIR at ORNL for neutron activation of radioisotopes.

Bigelow, T. S.; Tarallo, F. J.; Stevenson, N. R.

2005-12-01

48

Electrochemical Fractionation of Molybdenum Stable Isotopes  

NASA Astrophysics Data System (ADS)

Stable isotope signatures were measured from Molybdenum (Mo) electrodeposited from aqueous solution. As potential varied from -1.35 V to -2.00 V (relative to Ag/AgCl), fractionation decreases from ?97/95Mo = -1.3 to -0.9 (?97/95Mo defined as the difference in the 97Mo/95Mo ratio of deposited Mo relative to aqueous Mo). Natural variations of ?97/95Mo span a range of ~ 3 [Barling, J. and Anbar, A. D., EPSL. 2004, 217: 315], therefore, charge transfer driven fractionation may be responsible for some of the observed variation in Mo stable isotope geochemistry. Following previous approaches with Fe and Zn [Kavner, A. et al. Geochim. Cosmochim. Acta. 2005, 69: 2971; 2008, 72: 1731], Mo was plated in a three-electrode cell from a neutral to slightly alkaline solution (pH ~ 8.7). Voltage was held constant during electrodeposition using an Autolab Potentiostat. In all experiments, less than 0.5 % of the Mo was deposited, which insures that the plating reservoir remains at an approximately constant isotopic composition. Plated Mo was then recovered in acid, and the isotopic composition of samples and stock solutions were measured using a Thermo Scientific Neptune MC-ICP-MS. These experiments show that the redox process induces an isotopic signature with respect to the starting material, with a trend showing that fractionation decreases as a function of applied voltage.

Crawford, J.; Black, J.; Wasylenki, L.; Gordon, G.; Anbar, A.; Kavner, A.

2008-12-01

49

New Stable Isotope Tropical Paleoclimate Proxies  

NASA Astrophysics Data System (ADS)

Organized tropical rain systems such as tropical cyclones (TC) and mesoscale convective systems (MCS) produce both water vapor and rainfall with distinctly low isotope ratios. This lowering is caused by recyling of water in organized systems. Therefore, fresh water carbonate organisms have considerable potential to act as proxy recorders of these systems. Ostracoda are ephemeral making them especially attractive candidates. Tropical trees offer another opportunity because the low isotopic spikes produced in both soil waters when heavy rains result and ambient water vapor surronding the trees may be recorded in the tree cellulose. Ostracoda living in the surface waters derived from Tropical Storm Allison (2001) document the passage of the storm in their oxygen isotope ratios. The stable isotopic composition of water vapor along the southwest coast of Mexico shows considerable variation in response to TC and MCS activity offshore even when no rain falls in the region. Potentially a long-term record of this activity may be found in the stable isotopic composition of trees providing low elevation trees of sufficient longevity can be found.

Lawrence, J. R.

2005-05-01

50

Isotopic r-process abundances produced by supernova explosions  

NASA Astrophysics Data System (ADS)

The rapid neutron capture process (r-process) is one of the major nucleosynthesis processes responsible for the synthesis of heavy nuclei beyond iron. Isotopes beyond Fe are most exclusively formed in neutron capture processes and more heavier ones are produced by the r-process. Approximately half of the heavy elements with mass number A>70 and all of the actinides in the solar system are believed to have been produced in the r-process. We have studied the r-process in supernovae for production of heavy elements beyond A=40 with the newest mass values available. The supernovae envelopes at a temperature >109 K and neutron density of 1024 cm-3 are considered to be one of the most potential sites for the r-process. We investigate the r-process in a site-independent, classical approach which assumes a chemical equilibrium between neutron captures and photodisintegrations followed by a ?-flow equilibrium. We have studied the r-process path corresponding to temperatures ranging from 1.0109 K to 3.0109 K and neutron density ranging from 1020 cm-3 to 1030 cm-3. The primary goal of the r-process calculations is to fit the global abundance curve for solar system r-process isotopes by varying time dependent parameters such as temperature and neutron density. This method aims at comparing the calculated abundances of the stable isotopes with observation. The abundances obtained are compared with supernova explosion condition and found in good agreement. The elements obtained along the r-process path are compared with the observed data at all the above temperature and density range.

Baruah, Rulee; Duorah, Kalpana; Duorah, H. L.

2012-08-01

51

Stable Isotopes, Quantum Computing and Consciousness  

NASA Astrophysics Data System (ADS)

Recent proposals of quantum computing/computers (QC) based on nuclear spins suggest that consciousness (CON) activity may be related (assisted) to subset of C13 atoms incorporated randomly, or quasirandomly, in neural structures. Consider two DNA chains. Even if they are completely identical chemically (same sequence of codons), patterns of 12C and 13C isotopes in them are different (possible origin of personal individuality). Perhaps it is subsystem of nuclear spins of 13C "sublattice" which forms dynamical system capable of QC and on which CON is "spanned". Some issues related to this hypothesis are: (1) existence of CON-driven positional correlations among C13 atoms, (2) motion (hopping) of C13 via enhanced neutron tunneling, cf. quantum "anti Zeno-effect", (3) possible optimization of concentration of QC-active C13 atoms above their standard isotopic abundance, (4) characteristic time-scales for operation of C13-based QC (perrhaps, broad range of scales), (5) reflection of QC dynamics of C13 on CON, (6) possibility that C13-based QC operates "above" level of "regular" CON (perhaps, Jungian sub/super-CON), (7) isotopicity as connector to universal Library of Patterns ("Platonic World"), (8) self-stabilization of coherence in C13 (sub)system. Some of this questions are, in principle, experimentally addressable through shifting of isotopic abundances.

Berezin, Alexander A.

2000-10-01

52

Stable isotope `vital effects' in coccolith calcite  

NASA Astrophysics Data System (ADS)

Uncertainties about the origin of the many disequilibrium or 'vital effects' in a variety of calcifying organisms, and whether these effects are constant or variable, have hampered paleoceanographic application of carbon and oxygen isotopic ratios. Unraveling the source of these effects will improve paleoceanographic applications and may provide new information on changes in cell physiology and ecology. Culture of eight species of coccolithophorids, a dominant marine phytoplankton group, reveals a 5 array of disequilibrium or 'vital effects' in both the carbon and oxygen isotopic composition of coccolith calcite. In moderate light and nutrient-replete cultures, oxygen isotopic fractionation and carbon isotopic fractionation correlates directly with cell division rates and correlates inversely with cell size across a range of species. However, when growth rates of a single species are increased or decreased by higher or lower light levels, ? 18O is relatively invariant. Likewise, growth rate variations as a function of temperature do not influence coccolith ? 18O; the slope of the ? 18O vs. temperature relation in cultures of both Gephyrocapsa oceanica and Helicosphaera carteri is the same as for abiogenic carbonates. This suggests a constant, species-specific isotopic fractionation which does not vary with cell physiology. The constancy of vital effects suggests that coccolith stable isotopes will provide reliable phase for paleoceanographic reconstruction of temperature and seawater chemistry, as long as monospecific fractions are analyzed or changes in nannofossil assemblages are accounted for with species-specific correction factors. We suspect that the cell size, and its constraints on the rate of CO 2 diffusion relative to C fixation, may be the first order influence on coccolith stable isotope vital effects. A quantitative model of this process may provide important constraints on mechanisms of carbon acquisition of coccolithophorids in both modern and extinct species.

Ziveri, P.; Stoll, H.; Probert, I.; Klaas, C.; Geisen, M.; Ganssen, G.; Young, J.

2003-05-01

53

Paleoenvironmental reconstruction of the Asbole fauna (Busidima Formation, Afar, Ethiopia) using stable isotopes  

Microsoft Academic Search

The Middle Pleistocene environmental and climatic conditions at Asbole, lower Awash Valley, Ethiopia were reconstructed using stable carbon and oxygen isotopic composition (13C, 18O) of fossil tooth enamel coupled with faunal abundance data. We analyzed the isotopic composition of a total of 80 herbivorous tooth enamel samples from 15 mammalian taxa, which archive the dietary preferences and drinking behavior from

Zelalem Bedaso; Jonathan G. Wynn; Zeresenay Alemseged; Denis Geraads

2010-01-01

54

Stable Isotope Spectroscopy for Diagnostic Medicine  

NASA Astrophysics Data System (ADS)

Isotopic tracers have been used in medical research for more than fifty years. Radioactive isotopes have been most used because of the high detection efficiencies possible. With increased awareness of the effects of low level radiation and radioactive waste management problems, the need for safe non radioactive tracers has become apparent. Rare stable isotopes of biologically active elements can be used for metabolic and pharmacokinetic studies provided that both sufficient detection sensitivity can be achieved and reliable cost effective instruments can be developed. High resolution optical spectroscopic methods which can determine isotopic ratios with high precision and accuracy are viable for research and clinical use. The study of 13C/12C ratios in CO2 for breath test diagnostics will be described in detail. Using the laser optogalvonic effect with isotopic lasers a specific medical diagnostic for h-pylori infection, has recently received FDA approval. Opportunities exist to study D/H ratios in water and 18O/16O ratios in CO2 and water for basic metabolism diagnostics and 15N/14N ratios in urine for liver function and related studies.

Murnick, D. E.

2000-06-01

55

Ce isotope abundance in chondritic and HED meteorites  

NASA Astrophysics Data System (ADS)

138La, 136Ce and 138Ce are p-process nuclides, and their isotopic abundances are generally low due to their modes of nucleosynthesis compared with other isotopes of La and Ce (139La, 140Ce and 142Ce). Tanimizu et al. (2004) mentioned that, using the 140Ce/142Ce ratio as the normalizing value, 136Ce isotope abundance could be acted as an indicator of p-process nuclide anomaly for extra-terrestrial materials to understand the nucleosynthetic origins of solar system matter. Then, meteoritic primordial composition of Ce isotope provides useful information related with 138La decay system. Especially, combined Ce/Nd isotope data in geological and cosmological materials enable us the modeling of the light REE profiles of the source material. We measured Ce isotope ratio for fifteen meteorites, using 140Ce/142Ce=7.941 as the normalizing value, in order to compare Ce isotope abundance between chondritic and HED meteorites. Of them, Ce isotope abundances from two chondritic meteorites were deviated from the average abundances of other 13 meteorites. In this report, we will discuss cosmochemical significance of Ce isotope anomaly.

Lee, S.; Asahara, Y.; Tanaka, T.; Lee, S. R.

2011-12-01

56

A large area experiment to determine cosmic ray isotopic abundances  

NASA Technical Reports Server (NTRS)

Measurements of the isotopic composition of cosmic rays have shown that the cosmic ray isotope ratios, Ne-22/Ne-20 and (Mg-25 + Mg-26)/Mg-24, exceed the solar abundance ratios by factors of 2.7 and 1.8, respectively. There are several processes which could be responsible for the observed excess of neutron-rich isotopes. The considered models imply neutron enrichment in the case of other, less abundant species, and a measurement of the involved isotopic abundances could provide a basis for the determination of the dominating processes occurring in cosmic ray sources. However, an experiment utilizing special equipment is necessary to conduct the required measurements. Such an experiment, the Aluminum Isotopic Composition Experiment (Alice), is being designed in a joint effort involving NASA and a West German university. Alice uses a Cherenkov-range technique to determine the isotopic composition of elements from oxygen through argon.

Mauger, B. G.; Balasubrahmanyan, V. K.; Ormes, J. F.; Streitmatter, R. E.; Heinrich, W.; Simon, M.; Tittel, H. O.

1983-01-01

57

The abundances of elements and isotopes in the solar wind  

NASA Technical Reports Server (NTRS)

Studies of the chemical and isotopic composition of the solar wind are reviewed. Solar wind abundance measurements are discussed and solar wind, coronal, and photospheric abundances for elements between H and Fe are presented. Also, consideration is given to the determination of the solar wind isotopic composition of the noble gases using foil collection techniques and the observation of solar wind heavy ions with the mass per charge spectrometer on ISEE-3. Other topics include solar wind observations with solid state detectors, solar wind abundances in the magnetosheath and the plasma sheet, and high-mass resolution measurements of chemical elements and isotopes in the solar wind.

Gloeckler, George; Geiss, Johannes

1988-01-01

58

Rivers and Stable Isotopes as Indicators of Biogeochemical Gradients  

NASA Astrophysics Data System (ADS)

Consideration of processes on very small (microbe) to large (catchment) scales become increasingly important in biogeochemical gradient work. In this context, rivers are ideal indicators of biogeochemical gradients for large continental scales when geochemical- and discharge data are combined for flux evaluations. If these are further combined with isotope measurements, sources and turnover of water and dissolved constituents can be quantified. An example study is the combination of GIS-, discharge- and water stable isotope data on the in Clyde River basin in Scotland. Here we determined transpiration with an annual average of 0.489 km3 a-1. When combining this rate with the water use efficiency, the CO2 uptake of the entire basin yielded an annual net primary production (NPP) of 185.2 g C m-2. Compared to other temperate areas this is about half the NPP than expected, which is most likely caused by the predominant cover of grasslands. Therefore, agricultural and forest vegetation schemes could influence continental water balances on time scales of years to decades. In another study on the Lagan River in N. Ireland, stable isotope methods were applied to evaluate the role of carbonate versus silicate dissolution. Of these two types of weathering only silicate dissolution withdraws atmospheric CO2 to be stored in the continental crust over long time periods. A downstream evolution with increasing pH- and ?13CDIC values revealed carbonate dissolution despite their minor abundance in the catchment of less than 5 %. This dominant carbonate signal on the riverine carbon cycle outlines the capacity of buffering anthropogenic influences and CO2 turnover. It should be even more pronounced in other rivers where carbonates usually occupy a larger proportion of the basin geology. Future biogeochemical gradient work on rivers should apply particulate and dissolved organic constituent fluxes. This includes more refined compound specific isotope work on selected pollutants such as TCE, PAH, PCB as well as riverine microbiological considerations. Such expansions meet the challenge of measuring much smaller concentrations compared to groundwater contaminant plumes. Further combinations of stable N, H, O, and S isotope systems would also help to resolve overlapping trends when only carbon isotopes are measured. Apart from combining traditional light stable isotope systems, addition of newly accessible isotope groups by multicollector ICP-MS (i.e. Fe, Cr, Zn) and radioisotope techniques can provide innovative tools for resolving gradients and their biogeochemical cycling within rivers.

Barth, J. A.

2005-12-01

59

Stable isotopes dissect aquatic food webs from the top to the bottom  

NASA Astrophysics Data System (ADS)

Stable isotopes have been used extensively to study food-web functioning, that is, the flow of energy and matter among organisms. Traditional food-web studies are based on the natural variability of isotopes and are limited to larger organisms that can be physically separated from their environment. Recent developments allow isotope ratio measurements of microbes and this in turn allows the measurement of entire food webs, in other words, from small producers at the bottom to large consumers at the top. Here, I provide a concise review on the use and potential of stable isotopes to reconstruct end-to-end food webs. I will first discuss food web reconstruction based on natural abundances isotope data and will then show that the use of stable isotopes as deliberately added tracers provides complementary information. Finally, challenges and opportunities for end-to-end food web reconstructions in a changing world are discussed.

Middelburg, J. J.

2014-04-01

60

Stable isotope probing linking microbial identity to function  

Microsoft Academic Search

Stable isotope probing (SIP) is a technique that is used to identify the microorganisms in environmental samples that use a particular growth substrate. The method relies on the incorporation of a substrate that is highly enriched in a stable isotope, such as 13C, and the identification of active microorganisms by the selective recovery and analysis of isotope-enriched cellular components. DNA

Marc G. Dumont; J. Colin Murrell

2005-01-01

61

Stable isotopes in fish as indicators of habitat use  

EPA Science Inventory

In our isotopic studies of fish in Oregon Coast Range streams we have found stable isotopes of carbon, oxygen and sulfur to be surprisingly useful in identifying and discriminating specific habitat or tributary use by a variety of fish species. Stable isotopes of carbon can be u...

62

Embryotoxicity of stable isotopes and use of stable isotopes in studies of teratogenetic mechanisms  

SciTech Connect

Experiments on teratogenic effects of stable isotopes from our own and other laboratories are evaluated. In the first series of investigations, the enrichment of the stable isotope /sup 13/C derived from U-/sup 13/C-glucose was studied in mouse embryos at various stages of development, including limb buds in organ culture. Preimplantation mouse embryos incubated in vitro in /sup 13/C-enriched medium for 48 hours showed normal development during subsequent differentiation in vitro and also in vivo after embryo transfer to faster mothers. These embryos were 15% to 20% enriched in /sup 13/C. Administration of U-13-C-glucose to pregnant mice during organogenesis led to an increase of the absolute /sup 13/C content of the embryo for several days after the end of isotope administration, whereas the enrichment in maternal tissue decreased. No alterations of embryonic development were detected due to stable isotope enrichment. Development of cultured mouse limb buds was unaffected by incubation with 82 mol% U-/sup 13/C-glucose as judged from morphologic and biochemical criteria. The second part of the article describes the value of deuterium-labeled drugs as probes into the mechanism of activation of teratogenic metabolites. A comparison of the pharmacokinetics as well as the teratogenicity between cyclophosphamide and some specific deuterium-labeled analogues showed that the isotope effect observed can be related to a particular metabolic pathway crucial for teratogenic activation by this drug.

Spielmann, H.; Nau, H.

1986-07-01

63

LITERATURE SURVEY ON ISOTOPIC ABUNDANCE RATIO MEASUREMENTS - 2001-2005  

SciTech Connect

Along with my usual weekly review of the published literature for new nuclear data, I also search for new candidates for best measurements of isotopic abundances from a single source. Most of the published articles, that I previously had found in the Research Library at the Brookhaven Lab, have already been sent to the members of the Atomic Weights Commission, by either Michael Berglund or Thomas Walczyk. In the last few days, I checked the published literature for any other articles in the areas of natural variations in isotopic abundance ratios, measurements of isotopic abundance ratios on samples of extra-terrestrial material and isotopic abundance ratio measurements performed using ICPMS instruments. Hopefully this information will be of interest to members of the Commission, the sub-committee on isotopic abundance measurements (SIAM), members of the former sub-committee on natural isotopic fractionation (SNIF), the sub-committee on extra-terrestrial isotope ratios (SETIR), the RTCE Task Group and the Guidelines Task Group, who are dealing with ICPMS and TIMS comparisons. In the following report, I categorize the publications in one of four areas. Measurements performed using either positive or negative ions with Thermal Ionization Mass Spectrometer, TIMS, instruments; measurements performed on Inductively Coupled Plasma Mass Spectrometer, ICPMS, instruments; measurements of natural variations of the isotopic abundance ratios; and finally measurements on extra-terrestrial samples with instrumentation of either type. There is overlap in these areas. I selected out variations and ET results first and then categorized the rest of the papers by TIMS and ICPMS.

HOLDEN, N.E.

2005-08-13

64

Assessing the Amazon Basin Circulation with Stable Water Isotopes  

NASA Astrophysics Data System (ADS)

The isotopic abundances of Oxygen-18 (? 18O) and Deuterium (? D) over the Amazon are used to constrain simulations of the water cycle in this, the largest river basin in the world. Tracking the two stable but rare isotopes of water (1HD16O and 1H218O) makes it possible to trace Amazonian regional evaporative and condensation processes. This offers isotopic constraints on regional to global-scale atmospheric moisture budgets. Based on data in the Global Network on Isotopes in Precipitation (GNIP) database, we analyse the simulation of the land surface hydrology and water cycling. Temporal changes between 1965 and 2000 in stable water isotopic signatures in the Amazon have been used to evaluate global climate model (GCM) predictions revealing notable anomalies. For example, the differences in the wet season deuterium excess between Belem and Manaus are consistent with recent GCM simulations only if there has been a relative increase in evaporation from non-fractionating water sources over this period. Despite earlier predictions that land-use change signals would be found, late twentieth century data reveal no significant change in dry season isotopic characteristics. On the other hand, more recent isotopic data do show trends at stations in the Andes, where as much as 88% of the rainfall is thought to be derived from recycled moisture. At Izobamba the wet season depletions are enhanced (greater depletion) and the dry season ones decreased (less depletion). At Bogota only the wet months show statistically significant changes - also an enhancement. More depletion in the wet months is consistent with reductions in non-fractioning recycling such as through transpiration and in full re-evaporation of canopy-intercepted rainfall. These data might be linked to deforestation impacts. Results of GCM and simpler model simulations of the Amazon suggest that the recent stable isotope record is consistent with the predicted effects of forest removal, perhaps combined with greenhouse warming. At a minimum, large-scale simulations of South American climate ought to be tested against these isotopic data in any validation effort. Specific caveats our conclusions include: (i)monthly isotope data only are available in GNIP and hence analysed; (ii) the statistically significant seasonal changes reported might be related to, or even exaggerated by, El Nio-Southern Oscillation (ENSO) events or other climatic variations that modify the Walker circulation and Inter-Tropical Convergence Zone (ITCZ) position and hence affect the moisture climatology of the Amazon; (iii)no information on fluxes from simulated open water as a surface type in the Amazon GCM experiments has been considered; (iv)the selected models are failing to correctly simulate the relative components of transpiration and re-evaporated canopy interception in the Amazon dry season; and (v) no isotope tracking in the Amazon deforestation simulations was reviewed, because none is yet available. These shortcomings deserve further work.

McGuffie, K.; Henderson-Sellers, A.

2004-05-01

65

Carbon Isotope Abundance Ratios in Comets  

NASA Astrophysics Data System (ADS)

High resolution (lambda /Delta lambda ~ 10(5) ) spectra of the CN B-X (0-0) band at 3883 Angstroms have been obtained of four comets using the Mt. Stromlo 1.8-m telescope echelle spectrograph. The resolution and the S/N ratios of the spectra are of sufficient quality that (13) C(14) N lines have been identified in two of the comets. A fluorescence equilibrium model has been developed to compute the rotational line populations in the four lowest vibrational levels of the ground electronic state of the CN B-X (0-0) band. Line fluorescence efficiencies and rotational line intensities for all isotopic combinations of (12) C, (13) C, (14) N and (15) N have been computed for a range in heliocentric velocites. The computed CN spectra generated at the observed resolution are compared with the observations, and (12) C/(13) C ratios are derived. We show for the first time that collisions in the inner coma significantly affect the rotational line populations in the lowest vibrational levels of the ground electronic state. We find that the carbon isotope ratios are consistent with terrestrial values in all four comets.

Kleine, M.; Wyckoff, S.; Wehinger, P. A.; Peterson, B.

1992-12-01

66

A redetermination of the isotopic abundances of atmospheric Ar  

Microsoft Academic Search

Atmospheric argon measured on a dynamically operated mass spectrometer with an ion source magnet, indicated systematically larger 40Ar\\/36Ar ratios compared to the generally accepted value of Nier [Nier A.O., 1950. A redetermination of the relative abundances of the isotopes of carbon, nitrogen, oxygen, argon, and potassium. Phys. Rev. 77, 789793], 295.50.5, which has served as the standard for all isotopic

Jee-Yon Lee; Kurt Marti; Jeffrey P. Severinghaus; Kenji Kawamura; Hee-Soo Yoo; Jin Bok Lee; Jin Seog Kim

2006-01-01

67

APPROACHES FOR MEASURING STABLE CARBON AND NITROGEN ISOTOPES IN BACTERIA  

EPA Science Inventory

Stable isotopes have been used successfully over the past three decades to trace through aquatic food chairs. his technique, however, has only recently been used to examine aquatic microbial roles in elemental cycling. he major obstacle to measuring stable isotope compositions in...

68

Stable isotopes in daily precipitation at Dome Fuji, East Antarctica  

Microsoft Academic Search

Daily precipitation samples for stable isotope analysis were collected throughout 2003 at Dome Fuji Station, inland East Antarctica. Stable isotopes show significantly depleted values with a large seasonal variability, which have never been obtained. Temporal changes in ?-T relation and d-excess are consistent with those found in geographical distribution. Precipitation was obtained almost everyday, though the amounts were quite small

Koji Fujita; Osamu Abe

2006-01-01

69

Stable Isotopes and Mineral Resource Investigations in the United States  

NSDL National Science Digital Library

This USGS handout is a page providing a good, brief summary of stable isotope techniques and applications in the geosciences. A map indicating the locations of current USGS stable isotopic studies accompanies the text. A discussion of mineral weathering effects and case studies from ore deposits in Maine and North Carolina complement the general overview.

70

INCORPORATING CONCENTRATION DEPENDENCE IN STABLE ISOTOPE MIXING MODELS  

EPA Science Inventory

Stable isotopes are frequently used to quantify the contributions of multiple sources to a mixture; e.g., C and N isotopic signatures can be used to determine the fraction of three food sources in a consumer's diet. The standard dual isotope, three source linear mixing model ass...

71

INCORPORATING CONCENTRATION DEPENDENCE IN STABLE ISOTOPE MIXING MODELS  

EPA Science Inventory

Stable isotopes are often used as natural labels to quantify the contributions of multiple sources to a mixture. For example, C and N isotopic signatures can be used to determine the fraction of three food sources in a consumer's diet. The standard dual isotope, three source li...

72

Intrapopulation variation in carbon and nitrogen stable isotope ratios in the earthworm Aporrectodea longa  

Microsoft Academic Search

The natural abundance variations in carbon and nitrogen stable isotope ratios in a population of the earthworm Aporrectodea longa, a species known to feed on both soil and plant litter, is reported in this paper. Worms were collected from a small land area of an old white clover field and body tissue and mucus were analyzed separately. The range of

Olaf Schmidt

1999-01-01

73

Stable isotopes' as trophic tracers: combining field sampling and manipulative labelling of food resources for macrobenthos  

Microsoft Academic Search

We combined 3 different approaches to determine the relative importance of microphytobenthos production as food for intertidal macrobenthic animals: (1) the natural abundance of stable-isotope ratios of carbon and nitrogen, (2) an in situ deliberate tracer addition of C-13-bicarbonate, which was transferred through the benthic food chain after its incorporation by benthic algae, and (3) a dual labelling experiment in

P. M. J. Herman; J. J. Middelburg; J. Widdows; C. M. Lucas; C. H. R. Heip

2000-01-01

74

Stable Isotope Database: present and past archives  

NASA Astrophysics Data System (ADS)

Paleoclimate data provide benchmarks against which the realism of the processes simulated by climate models can be assessed. Within this framework, it is essential to avoid introducing uncertainties associated with transfer functions and therefore to operate with robust proxies. The implementation of stable isotopes of water or carbon inside climate models motivates a synthesis of available data. Supported by the LABEX L-IPSL and involving a team of climate modelers and paleoclimatologists, this project aims to establish a worldwide database of ?18O, ?D ?17O and ?13C from oceanic microfossils, corals, ice cores, cave speleothems, lakes, tree rings, and vegetation leaves wax. The aim is to provide a global vision of the hydrological cycle during the LGM and other selected key periods (last 2000 years, Mid-Holocene, Dansgaard-Oeschger events, and the Eemian). It requires screening through hundreds of published oceanic and continental records, validating the selection of the data based on resolution and chronological information. We extracted ~900 dated ?18O records from 650 marine sediment cores, 65 ?18O records from 50 ice cores, ~200 ?18O speleothems records from 60 caves, and 540 ?13C records from 290 marine sediment cores. An additional aspect of this project consists in the construction of an online portal providing an intuitive and interactive platform allowing selecting, visualizing, and downloading of the records included in this database, thus improving the distribution and comparison of paleoclimatic records from various sites.

Bolliet, Timoth

2014-05-01

75

Apolipoprotein metabolism: a stable-isotope approach.  

PubMed

Lipids are the major fuel of the body. Efficient functioning as an energy source dictates that lipids must be transportable in the plasma from the point of synthesis and assembly to the storage depots and finally to the tissues to provide energy through oxidative metabolism. Complex lipid forms are transported through the plasma as lipoprotein particles. These particles, secreted from the intestine and liver, have nonpolar outer surface composed of cholesterol, phospholipids, and apolipoproteins. Apolipoproteins are essential for the production, secretion, and continued structural integrity of the various lipoprotein particles and thus play a pivotal role in the control mechanisms of lipid transport. Apolipoproteins regulate specific enzyme activities and modulate plasma lipoprotein clearance through receptor-mediated processes. Quantitative information regarding the rates of synthesis and catabolism of apolipoproteins is vital to an understanding of their metabolism in health and disease. General considerations are followed by a specific use of stable-isotope methodology to quantitative the rate of synthesis of very-low-density-lipoprotein apolipoprotein B-100 (VLDL apo B-100) in control and familial-combined-hyperlipidemic (FCHL) patients. PMID:8475890

Halliday, D; Venkatesan, S; Pacy, P

1993-05-01

76

Literature Survey on Isotopic Abundance Ratio Measurements 2001-2005.  

National Technical Information Service (NTIS)

Along with my usual weekly review of the published literature for new nuclear data, I also search for new candidates for best measurements of isotopic abundances from a single source. Most of the published articles, that I previously had found in the Rese...

N. E. Holden

2005-01-01

77

Convenient synthesis of stable deuterium-labeled alkylpyrazines for use in stable isotope dilution assays.  

PubMed

Stable isotope dilution assays (SIDA) provide for accurate and precise quantitation of aroma components, such as alkylpyrazines, which are often present in low concentrations in complex food matrices. The unavailability of labeled standards is the main limitation to the widespread use of SIDA. This study describes the chlorination of several alkylpyrazines to form the corresponding chloroalkylpyrazine compounds, which are efficient starting materials for the synthesis of deuterium-labeled alkylpyrazines, namely [H?]-2-methylpyrazine (d-1), [H?]-2-ethylpyrazine (d-2), [H?]-2,3(or 6)-dimethylpyrazine (d-3A, d-3B), [H?]-2,[H?]-6-dimethylpyrazine (d-3C), [H?]-2,[H?]-6-diethylpyrazine (d-4), [H?]-2-ethyl-3(or 6)-methylpyrazine (d-5A, d-5B), 2,[H?]-3,5-trimethylpyrazine (d-6), [H?]-2-ethyl-3,6-dimethylpyrazine (d-7), [H?]-2-ethyl-3,5-dimethylpyrazine (d-8), and 2,3-diethyl-[H?]-5-methylpyrazine (d-9), which were obtained in good yields (57-100%) and high purities (86-98%). These stable isotopes were used as internal standards in SIDA to accurately and precisely determine selected alkylpyrazines in commercial peanut butter, cocoa powder, and instant coffee. 2,3-Diethyl-5-methylpyrazine (p-9) and 2-ethyl-3,5-dimethylpyrazine (p-8), despite their low abundance, had the highest odor-active values among the 13 pyrazines quantified in all products due to their very low odor thresholds. PMID:23528050

Fang, Mingchih; Cadwallader, Keith R

2013-04-17

78

Stable isotope views on ecosystem function: challenging or challenged?  

PubMed Central

Stable isotopes and their potential for detecting various and complex ecosystem processes are attracting an increasing number of scientists. Progress is challenging, particularly under global change scenarios, but some established views have been challenged. The IX meeting of the Spanish Association of Terrestrial Ecology (AAET, beda, 1822 October 2009) hosted a symposium on the ecology of stable isotopes where the linear mixing model approach of partitioning sinks and sources of carbon and water fluxes within an ecosystem was challenged, and new applications of stable isotopes for the study of plant interactions were evaluated. Discussion was also centred on the need for networks that monitor ecological processes using stable isotopes and key ideas for fostering future research with isotopes.

Resco, Victor; Querejeta, Jose I.; Ogle, Kiona; Voltas, Jordi; Sebastia, Maria-Teresa; Serrano-Ortiz, Penelope; Linares, Juan C.; Moreno-Gutierrez, Cristina; Herrero, Asier; Carreira, Jose A.; Torres-Canabate, Patricia; Valladares, Fernando

2010-01-01

79

Continuous operation of spectroscopy instruments for stable isotope analysis  

NASA Astrophysics Data System (ADS)

Routine Application of Novel Stable Isotope Spectroscopy Instruments; Berkeley, California, 12 December 2010 ; Stable isotopes provide a tracer for biogeochemical processes and for exchange between the biosphere and atmosphere at local to global scales. Recent developments in laser spectroscopy now offer the ability to measure stable isotopes in small molecules such as water vapor and carbon dioxide in unprecedented temporal resolution (up to 10 hertz). In a meeting organized with support from the U.S. National Science Foundation-funded Biogeosphere-Atmosphere Stable Isotope Network (BASIN), an international group consisting of researchers and manufacturers' representatives discussed the challenges of daily use of absorption spectroscopy instruments for stable isotope analysis in continuous field operation. Technological advancement in absorption spectroscopy analysis techniques tied to increased availability of affordable instruments has opened the door to new scientific opportunities and facilitates the use of stable isotope analysis by a larger group of researchers. Despite technological progress, though, stable isotope analysis still requires delicate treatment of samples and setup. Meeting participants tried to identify the key responsibilities for individual labs and the scientific community to help ensure comparability of results and prepare for future regional to global collaborative research efforts. The meeting was concluded with the recommendations below.

Zeeman, Matthias J.; Tu, Kevin P.; Knohl, Alexander

2011-06-01

80

Micronutrient Cadmium in the Oceans, Distribution and Stable Isotope Fractionation  

NASA Astrophysics Data System (ADS)

Recent breakthroughs in ultra-clean seawater sampling, analytical instrumentation and chemical separation of trace metals have led to significant improvement in both sensitivity and accuracy of concentration measurements of some key bio-limiting metals such as Zn, Cd and Fe. Stable isotope fractionations of these transition metal elements have added a further new dimension to our understanding of the marine biogeochemical cycling of trace nutrients. Improving our understanding of the latter is essential for assessing the impact of climate changes on the global carbon cycle, given the control of oceanic nutrient inventories on the efficiency of the "biological pump" and hence, its strength in regulating the sequestration of atmospheric CO2. The first reliable vertical distribution profiles of trace metal element cadmium (Cd) in the oceans [1, 2] showed a correlation with the major nutrient phosphate. This apparent involvement of Cd in the ocean biological cycle was unexpected, as Cd was known to be toxic, notably at high Cd abundance where it interferes with the true biological function of zinc (Zn), due to their similar chemistry. The novel ability to measure accurately the stable isotope fractionation of Cd in seawater may now help unravel the apparent role of Cd in the ocean biological cycle, akin to the classical breakthroughs and numerous applications of the ratio 13C/12C for understanding the ocean carbon cycle. We have examined the distribution of Cd concentration and isotope ratios in depth profiles from the High Nutrients Low Chlorophyll (HNLC) Southern Ocean, collected within the framework of the international GEOTRACES program. The first surface water transect along the Greenwich Meridian in the Southern Ocean revealed a strong meridional isotope gradient and two major biogeochemical provinces with distinctive Cd isotope fractionation factors, apparently related to phytoplankton community compositions and cellular uptake mechanisms [3]. Here we focus on the vertical distribution of Cd concentration and isotope ratios in the water column, as these reflect the combined effects of physical, chemical, and biological processes that control the export of carbon to the deep ocean. Cadmium concentration depth profiles show typical nutrient-like distributions with differences in the Cd-maxima depths, consistent with those of phosphate and reveal changes in the depth of re-mineralization of Cd and PO4 across the Antarctic. A strong surface-to-depth isotope gradient is seen in all profiles with high ?112/110Cd values in the mixed layer of up to +4.5 and low values of about +1.2, identifying deep Antarctic waters with a Cd-light isotope signature. The depth zone of maximum changes in Cd concentration and ?112/110Cd values coincide with that of the apparent oxygen utilization, a tracer of carbon export, demonstrating the role of Cd as an important nutrient for marine ecosystems. Examination of property-property co-variations provide new insights into the cycling of Cd and other trace metals which will be discussed, with emphasis on the significance of the global oceanic Cd-phosphate correlation and use and pitfalls of Cd isotopes as tracer of past changes in the strength of the biological carbon pump and the thermohaline circulation. [1] Boyle et al. (1976), Nature 263, 42-44. [2] Bruland (1980), EPSL, 47, 176-198. [3] Abouchami et al. (2011), EPSL 305, 83-91.

Abouchami, W.; Galer, S. J.; Feldmann, H.; Andreae, M. O.; de Baar, H.; Middag, R.; Klunder, M.; Laan, P.

2012-12-01

81

An investigation of techniques for the measurement and interpretation of cosmic ray isotopic abundances. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

An instrument, the Caltech High Energy Isotope Spectrometer Telescope was developed to measure isotopic abundances of cosmic ray nuclei by employing an energy loss - residual energy technique. A detailed analysis was made of the mass resolution capabilities of this instrument. A formalism, based on the leaky box model of cosmic ray propagation, was developed for obtaining isotopic abundance ratios at the cosmic ray sources from abundances measured in local interstellar space for elements having three or more stable isotopes, one of which is believed to be absent at the cosmic ray sources. It was shown that the dominant sources of uncertainty in the derived source ratios are uncorrelated errors in the fragmentation cross sections and statistical uncertainties in measuring local interstellar abundances. These results were applied to estimate the extent to which uncertainties must be reduced in order to distinguish between cosmic ray production in a solar-like environment and in various environments with greater neutron enrichments.

Wiedenbeck, M. E.

1977-01-01

82

Metal stable isotopes in low-temperature systems: A primer  

USGS Publications Warehouse

Recent advances in mass spectrometry have allowed isotope scientists to precisely determine stable isotope variations in the metallic elements. Biologically infl uenced and truly inorganic isotope fractionation processes have been demonstrated over the mass range of metals. This Elements issue provides an overview of the application of metal stable isotopes to low-temperature systems, which extend across the borders of several science disciplines: geology, hydrology, biology, environmental science, and biomedicine. Information on instrumentation, fractionation processes, data-reporting terminology, and reference materials presented here will help the reader to better understand this rapidly evolving field.

Bullen, T. D.; Eisenhauer, A.

2009-01-01

83

Miniature Laser Spectrometer for Stable Isotope Measurements  

NASA Technical Reports Server (NTRS)

As a first step in successfully measuring carbon isotopes optically we have previously demonstrated the measurement of C-13/C-12 to a precision of 0.1% using a tunable diode laser and CO2 spectral lines in the 2300/cm spectral region. This precision of 0.1% (1 per mil) for carbon isotopes is a value sufficiently precise to provide important isotopic data of interest to astrobiologists. The precision presently attainable in gases is sufficient to permit our instrument to be used in the measurement of isotopic ratios of interest to astrobiologists as well as geologists and planetary scientists.

Becker, J. F.; Kojiro, D. R.

1999-01-01

84

Isotopic Abundances as Tracers of the Processes of Lunar Formation  

NASA Astrophysics Data System (ADS)

Ever since Apollo, isotopic abundances have been used as tracers to study lunar formation, in particular, to study the sources of the lunar material. In the last decade, however, a number of isotopic similarities have been observed between the lunar samples and the Earth's mantle such that these two reservoirs are now known to be indistinguishable from one another to high precision for a variety of isotopic tracers. This occurs against the backdrop of a Solar System that exhibits widespread heterogeneity with respect to these tracers, a situation that strongly argues that the source of the lunar material is the silicate Earth. To reconcile this observation with the fact that the Moon is thought to result from the collision of two isotopically distinct planetary bodies, a scenario has emerged in which the material from the Moon-forming impactor and the proto-Earth are homogenized in the aftermath of the giant impact. This takes place via turbulent mixing in the time after the giant impact but before lunar accretion while the Earth-Moon system exists in the form of a continuous, high-temperature fluid. Importantly, this high-temperature phase of the evolution occurs in the presence of at least two phases (liquid + vapor) making possible chemical and isotopic fractionation. While equilibrium isotopic fractionation tends to zero at high temperatures, and the post giant impact environment experiences some of the highest temperatures encountered in the Earth sciences, there are several factors that nevertheless make equilibrium isotope effects important probes of this early evolution. (1) Because the vaporization of silicates involves decomposition reactions, the bonding environment for elements in the liquid is often very different from that in the vapor. This difference makes the magnitude of isotopic fractionation intrinsically large, even at the relevant temperatures. (2) Since the isotopic composition of a silicate liquid and co-existing vapor are distinctly different, if the Moon preferentially forms from the liquid or vapor relative to the Earth, mass-dependent isotopic differences at the planetary scale may arise. The large density contrast between liquid and vapor makes phase separation possible. (3) The precision with which planetary isotopic compositions can be determined has increased such that measurements are sensitive to even small degrees of high-temperature phase separation. Using thermodynamic models of silicate liquids to determine the partial vaporization behavior of the major elements, we will present calculations of isotopic fractionation due to liquid-vapor separation for the elements iron, magnesium, silicon, and oxygen. Improvements in analytical precision have largely settled the question of the source of the lunar material - the Earth's mantle - and isotopic measurements are now beginning to yield insight into the high-temperatures processes operating during lunar formation.

Pahlevan, K.

2011-12-01

85

BIODEGRADATION OF FLUORANTHENE AS MONITORED USING STABLE CARBON ISOTOPES  

EPA Science Inventory

The measurement of stable isotope ratios of carbon (d13C values) was investigated as a viable technique to monitor the intrinsic bioremediation of polycyclic aromatic hydrocarbons (PAHs). Biometer-flask experiments were conducted in which the bacterium, Sphingomonas paucimobilis,...

86

Stable Isotope Sales: Mound Customer and Shipment Summaries, FY 1984.  

National Technical Information Service (NTIS)

A listing is given of Mound's sales of stable isotopes of noble gases, deuterium, carbon, oxygen, nitrogen, chlorine, bromine, and sulfur for Fiscal Year 1984. Purchasers are listed alphabetically and are divided into domestic and foreign groups. A cross-...

J. A. Gridley

1986-01-01

87

Stable Isotope Sales: Mound Customer and Shipment Summaries, FY1983.  

National Technical Information Service (NTIS)

A listing is given of Mound's sales of stable isotopes of noble gases, deuterium, carbon, oxygen, nitrogen, chlorine, bromine, and sulfur for fiscal year 1983. Purchasers are listed alphabetically and are divided into domestic and foreign groups. A cross-...

J. Gridley

1985-01-01

88

Stable isotope sales: Mound customer and shipment summaries, FY 1988.  

National Technical Information Service (NTIS)

This report lists Mound's sales of stable isotopes of noble gases, carbon, oxygen, nitrogen, chlorine, bromine, and sulfur for fiscal year 1988. Purchasers are listed alphabetically and are divided into domestic and foreign groups. Cross-reference indexes...

K. A. Flayler

1990-01-01

89

Stable isotope sales: Mound customer and shipment summaries. FY 1989.  

National Technical Information Service (NTIS)

This report lists Mound's sales of stable isotopes of noble gases, carbon, oxygen, nitrogen, chlorine, bromine, and sulfur for fiscal year 1989. Purchasers are listed alphabetically and are divided into domestic and foreign groups. Cross-reference indexes...

K. A. Flayler

1991-01-01

90

Stable Isotope Sales: Mound Customer and Shipment Summaries, FY 1987.  

National Technical Information Service (NTIS)

This report lists Mound's sales of stable isotopes of noble gases, carbon, oxygen, nitrogen, chlorine, bromine, and sulfur for fiscal year 1987. Purchasers are listed alphabetically and are divided into domestic and foreign groups. Cross-reference indexes...

K. A. Flayler

1988-01-01

91

Stable Isotopes Sales: Mound Customer and Shipment Summaries, FY 1985.  

National Technical Information Service (NTIS)

A listing is given of Mound's sales of stable isotopes of noble gases, deuterium, carbon, oxygen, nitrogen, chlorine, bromine, and sulfur for fiscal year 1985. Purchasers are listed alphabetically and are divided into domestic and foreign groups. A cross-...

K. A. Flayler

1987-01-01

92

Progress in Value Assignment for Stable Isotope Reference Materials  

NASA Astrophysics Data System (ADS)

A re-compilation of the existing certificate data for stable isotope reference materials was carried out at IAEA during the last years. Most of these isotopic ratios are expressed as per mil deviation relative to the isotopic ratio of an artificially chosen primary reference material using the commonly used conventional ? -scales. The recommended isotope values for those reference materials, produced by various researchers and institutions over the last four decades and distributed by the IAEA and NIST, have been subject to different `value assignment' approaches in the past and resulted in some inconsistencies in their recommended certified isotopic composition. During an IAEA Advisory Group meeting in September 2000 consensus was obtained on a consistent and robust a posteriori data evaluation to assign the value on the existing whole suite of stable isotope reference materials (RM) for the elements of hydrogen, carbon, nitrogen, oxygen and sulfur. Advances towards a closer calibration of carbon RMs were presented by NIST as a result of a performed calibration exercise for inorganic stable carbon RMs involving selected laboratories. For the first time sulfur stable isotope calibration data were presented by different institutions, which allow a firm and consistent value assignment of sulfur stable isotope RMs. At the same time efforts at IRMM were presented to tie up those conventional ? -scale values to SI-units by direct isotope ratio measurements using primary methods. The future challenges are twofold: 1. improving and maintaining the consistency of established stable isotope ? -scales by better characterization of existing reference materials and production of suitable successor materials (as example the primary water reference materials VSMOW and SLAP will be discussed), and 2. producing suitable reference materials for new analytical methods, especially in the field of organic compounds analyzed by means of continuous flow methods involving gas chromatography and elemental analyzers coupled with mass spectrometers. Some initiatives for the production of new suitable reference materials will be presented.

Grning, M.; Taylor, P. D.; Klinedinst, D. B.

2001-05-01

93

Stable isotopes in pharmacology studies: present and future  

SciTech Connect

Stable-isotope techniques offer advantages over older methods in safety, sensitivity, specificity, and reduction in numbers of subjects required and analytic determinations for some types of pharmacology studies. In addition to their use as internal standards in gas chromatography-mass spectrometry analytic methods, stable isotopes have been successfully employed in studies of absorption, bioavailability, distribution, biotransformation, excretion, metabolite identification, time-dependent and dose-dependent pharmacokinetic changes, drug interactions, pharmacologic changes during pregnancy, mutagenicity, and teratogenicity. 32 references.

Browne, T.R.

1986-07-01

94

Stable Isotope Evidence for European Upper Paleolithic Human Diets  

Microsoft Academic Search

This paper presents the published and unpublished stable carbon and nitrogen isotope values for 36 European Upper Paleolithic\\u000a humans from 20 sites. The isotope data were measured to determine the sources of dietary protein in Upper Paleolithic diets;\\u000a the evidence indicates that animal, not plant, protein was the dominant protein source for all of the humans measured. Interestingly,\\u000a the isotope

Michael P. Richards

95

Carbon Stable Isotopes as Indicators of Coastal Eutrophication  

EPA Science Inventory

Coastal ecologists and managers have frequently used nitrogen stable isotopes (?15N) to trace and monitor anthropogenic nitrogen (N) in coastal ecosystems. However, the interpretation of ?15N data can often be challenging, if not confounding, as the isotope values fr...

96

Monitoring biodegradation of hydrocarbons by stable isotope fractionation  

Microsoft Academic Search

In the last decade, several studies have demonstrated that stable isotope tools are highly applicable for monitoring anaerobic biodegradation processes. An important methodological approach is to characterize distinct degradation pathways with respect to the specific mechanism of C-H-bond cleavage and to quantify the extent of biodegradation by compound specific isotope analysis (CSIA). Here, enrichment factors (?bulk) needed for a CSIA

Conrad Dorer; Anko Fischer; Steffi Herrmann; Hans-Hermann Richnow; Carsten Vogt

2010-01-01

97

USE OF STABLE ISOTOPES IN ENVIRONMENTAL AND FORENSIC GEOCHEMISTRY STUDIES  

EPA Science Inventory

Stable carbon and hydrogen isotopes have been used for many decades in the petroleum industry, but the development of combined gas chromatography-isotope ratio mass spectrometry (GCIRMS) has led to a virtual explosion in application of this technique not only in petroleum explora...

98

SOURCE PARTITIONING USING STABLE ISOTOPES: COPING WITH TOO MANY SOURCES  

EPA Science Inventory

Stable isotopes are increasingly being used as tracers in environmental studies. One application is to use isotopic ratios to quantitatively determine the proportional contribution of several sources to a mixture, such as the proportion of various pollution sources in a waste st...

99

Separation of the Stable Isotopes of Cl, S and Ca.  

National Technical Information Service (NTIS)

The stable isotopes of sulfur and chlorine are being separated on a practical scale by liquid phase thermal diffusion. The present capacity of a small separation system occupying 3m exp 2 of laboratory floor space is 0.5 kg of chlorine isotopes per year a...

W. M. Rutherford

1981-01-01

100

Modelling of stable water isotopes during frontal passages with COSMOiso  

NASA Astrophysics Data System (ADS)

Numerical models can help to better understand the complex processes influencing isotopic variability in atmospheric moisture and precipitation. They can provide information on the full three-dimensional structure of the isotopic composition of water vapour at locations where no measurements can be performed, and can be used for sensitivity experiments clarifying the role of specific processes governing isotopic variability. Isotope-enabled general circulation models have proven to successfully reproduce the large-scale climatological mean isotopic composition of surface precipitation. However, due to their typically coarse spatial resolution, they show difficulties in simulating isotopic variability associated with meso-scale weather events like fronts and convective systems. The implementation of stable water isotopes in limited-area models with high resolution is required to study the corresponding processes. In this study we present a one-year simulation for Europe with a recently introduced isotope-enabled version of the limited-area model COSMO (COSMOiso). The model is validated against observations at different locations, including high-resolution measurements of isotopes in water vapour in north-eastern Switzerland. Based on the simulation with COSMOiso, the connection between different meteorological parameters and the stable water isotopes is studied, with a focus on the passage of fronts. Composites of several events are used to characterise the typical three-dimensional structure and temporal evolution of stable water isotopes in water vapour associated with fronts. By using data from different vertical model levels we can gain new insight into the mechanisms influencing the isotopic composition in the atmospheric column during frontal passages. This allows to assess the process chain of precipitation formation in detail and will help in the interpretation of the resulting isotopic trends observed in surface precipitation.

Duetsch, Marina; Pfahl, Stephan; Aemisegger, Franziska; Sodemann, Harald; Wernli, Heini

2014-05-01

101

High Resolution Measurements of Isotope Shifts and Hyperfine Structure in Stable and Radioactive Lead Isotopes.  

National Technical Information Service (NTIS)

We present new measurements of isotopic shifts and hyperfine structure in the lead resonance line for a total of 15 isotopes. The experimental accuracy is of order 4 MHz. Using independent measurements of the nuclear parameter lambda for the stable isotop...

R. C. Thompson M. Anselment K. Bekk S. Goering A. Hanser

1982-01-01

102

Stable isotope ecology in the Omo-Turkana Basin.  

PubMed

Stable isotopes provide an independent assessment of paleoenvironments in the Omo-Turkana Basin. Stable isotopes track the flow of oxygen and carbon through ecosystems and accordingly are not directly related to changes in mammalian faunal composition or sedimentology. Therefore, isotope studies give insight into the paleoenvironmental conditions in which human evolutionary trends have been recorded. The development of stable isotopes as indicators of continental environmental conditions has proceeded in parallel with questions about the conditions of human environment. What was the vegetation? How hot was it? How dry? What were the diets of animals living among early humans? And most persistently, how important were "savannas" to early hominids? In this review, we take the opportunity to provide extensive background on the use of isotopes in anthropological sites. The application of stable isotope ecology to anthropological sites in the Turkana Basin has a long history, but in many ways the Omo-Turkana Basin has been a proving ground for the development of new proxy methods for understanding tropical terrestrial environments in the Neogene and Quaternary. For that reason, we also describe some of the fundamental aspects of isotope ecology that developed outside the field of paleoanthropology. PMID:22170692

Cerling, Thure E; Levin, Naomi E; Passey, Benjamin H

2011-01-01

103

Stable Chlorine Isotope Study: Application to Early Solar System Materials  

NASA Technical Reports Server (NTRS)

A significantly large mass fractionation between two stable chlorine isotopes is expected during planetary processes In addition, in view of the isotopic heterogeneity of other light elements, the chlorine isotopes can potentially be used as a tracer for the origins and evolutionary processes of early solar system materials. Due to analytical difficulties, however, current chlorine isotope studies on planetary materials are quite controversial among IRMS (gas source mass spectrometry) and/or TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1-3]. Although a cross-calibration of IRMS and TIMS indicates that both techniques are sufficiently consistent with each other [4], some authors have claimed that the Cl-37/Cl-35 ratio of geological samples obtained by TIMS technique are, in general, misleadingly too high and variable compared to those of IRMS [3]. For example, almost no differences of Cl isotope composition were observed among mantle materials and carbonaceous meteorites by [3]. On the other hand, according to more recent IRMS work [2], significant Cl isotope variations are confirmed for mantle materials. Therefore, additional careful investigation of Cl isotope analyses are now required to confirm real chlorine isotope variations for planetary materials including carbonaceous chondrites [5]. A significantly large mass fractionation between two stable chlorine isotopes is expected during planetary processes In addition, in view of the isotopic heterogeneity of other light elements, the chlorine isotopes can potentially be used as a tracer for the origins and evolutionary processes of early solar system materials. Due to analytical difficulties, however, current chlorine isotope studies on planetary materials are quite controversial among IRMS (gas source mass spectrometry) and/or TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1-3]. Although a cross-calibration of IRMS and TIMS indicates that both techniques are sufficiently consistent with each other [4], some authors have claimed that the 37Cl/35Cl ratio of geological samples obtained by TIMS technique are, in general, misleadingly too high and variable compared to those of IRMS [3]. For eample, almost no differences of Cl isotope composition were observed among mantle materials and carbonaceous meteorites by [3]. On the other hand, according to more recent IRMS work [2], significant Cl isotope variations are confirmed for mantle materials. Therefore, additional careful investigation of Cl isotope analyses are now required to confirm real chlorine isotope variations for planetary materials including carbonaceous chondrites [5]. In order to clarify the stable chlorine isotope features of early solar system materials, we have initiated development of the TIMS technique at NASA JSC applicable to analysis of small amounts of meteoritic and planetary materials. We report here the current status of chlorine isotope analysis at NASA JSC.

Mala,ira. M/; Nyquist, L. E.; Reese, Y.; Shih, C-Y; Fujitani, T.; Okano, O.

2010-01-01

104

Stable Isotope Tracers in Large Scale Hydrological Models  

NASA Astrophysics Data System (ADS)

Stable isotopes of oxygen and hydrogen (deuterium and oxygen-18) have been shown to be effective tracers for characterizing hydrological processes in small river basins. Their application in large river basins has lagged behind due to the lack of sufficient isotope data. Recent availability of isotope data from most US rivers and subsequent efforts by the International Atomic Energy Agency (IAEA) to collect comprehensive global information on isotope compositions of river runoff is changing this situation. These data sets offer new opportunities to utilize stable isotopes in studies of large river basins. Recent work carried out jointly by the Water Systems Analysis Group of the University of New Hampshire and the Isotope Hydrology Section of the IAEA applied isotope-enabled global water balance and transport models to assess the feasibility of using isotope data for improving water balance estimations at large scales. The model implemented simple mixing in the various storage pools (e.g. snow pack, soil moisture, groundwater, and river channel) and fractionation during evapotranspiration. Sensitivity tests show that spatial and temporal distributions of isotopes in precipitation and their mixing in the various storage pools are the most important factors affecting the isotopic composition of river discharge. The groundwater storage pool plays a key role in the seasonal dynamics of stable isotope composition of river discharge. Fractionation during phase changes appears to have a less pronounced impact. These findings are consistent with those in small scale catchments where ``old water'' and ``new water'' (i.e. pre-event water and storm runoff) can be easily separated by using isotopes. Model validation using available data from the US rivers showed remarkable performance considering the inconsistencies in the temporal sampling of precipitation and runoff isotope composition records. The good model performance suggests that seasonal variations of the isotopic composition of the precipitation and as a consequence the runoff follow a regular pattern that is less affected by inter-annual variations. The presentation will discuss the design and implementation of the isotope enabled water balance/transport model, its application and the potential of using global isotope information as (``soft'') calibration/validation data. Because of the sensitivity of runoff isotopic composition to groundwater storage pools, isotope data may offer new opportunities to assess the volumes of these storage terms and to evaluate their sustainability for human use.

Fekete, B. M.; Aggarwal, P.

2004-05-01

105

Fractionation of metal stable isotopes by higher plants  

USGS Publications Warehouse

Higher plants induce chemical reactions in the rhizosphere, facilitating metal uptake by roots. Fractionation of the isotopes in nutrients such as calcium, iron, magnesium, and zinc produces a stable isotope composition in the plants that generally differs from that of the growth medium. Isotope fractionation also occurs during transport of the metals within most plants, but its extent depends on plant species and on the metal, in particular, on the metal's redox state and what ligand it is bound to. The metal stable isotope variations observed in plants create an isotope signature of life at the Earth's surface, contributing substantially to our understanding of metal cycling processes in the environment and in individual organisms.

Von Blanckenburg, F.; Von Wiren, N.; Guelke, M.; Weiss, D. J.; Bullen, T. D.

2009-01-01

106

Stable isotope paleoaltimetry of the Mount Everest region  

NASA Astrophysics Data System (ADS)

Long-term climatic evolution and atmospheric circulation patterns are influenced to a first order by the topography of the largest mountain ranges. Reconstructing the Neogene elevation history of the Mount Everest region is of particular interest for understanding the tectonic history of the Himalaya-Tibet orogen as well as global scale atmospheric circulation and biotic changes through time. Stable isotope paleoaltimetry uses the isotopic lapse rate of precipitations preserved in the near-surface record. In the absence of surface deposits such as paleosols, volcanic ashes, or lacustrine limestone that record the stable isotopic composition of early to mid-Miocene water preserved in the highly erosive Himalayan range, we conduct stable-isotope paleoaltimetry based on the hydrogen isotopic composition (?D) of hydrous minerals that crystallized in the South Tibetan detachment (STD) shear zone at ~17 Ma. For paleoaltimetry reconstruction we compare stable isotope records from the STD mylonitic footwall to age-equivalent oxygen isotope ratios (?18O) measured within pedogenic carbonate from Siwalik foreland paleosols that developed near Miocene sea level. The relative differences between meteoric water compositions in the foreland basin and the ?18Owater calculated from the hydrogen isotope composition of syntectonic minerals suggest that by ~17 Ma the central Himalaya was at an elevation similar to what it is today, and that a rain shadow likely existed at that time. Our results demonstrate the power of shear-zone based paleoaltimetry in eroded mountain belts, call for caution in interpreting basin-based stable isotope paleoaltimetry in the rain shadow of the mid-Miocene Himalayan range and suggest that strengthening of the South Asian monsoon may have occurred in early to mid-Miocene, earlier than previously thought.

Gebelin, A.; Mulch, A.; Teyssier, C.; Jessup, M. J.; Law, R. D.; Brunel, M.

2012-12-01

107

Tritium and stable isotopes of magmatic waters  

Microsoft Academic Search

To investigate the isotopic composition and age of water in volcanic gases and magmas, we analyzed samples from 11 active volcanoes ranging in composition from tholeiitic basalt to rhyolite: Mount St. Helens (USA), Kilauea (USA), Pacaya (Guatemala), Galeras (Colombia), Satsuma Iwo-Jima (Japan), Sierra Negra and Alcedo (Ecuador), Vulcano (Italy), Par??cutin (Mexico), Kudryavy (Russia), and White Island (New Zealand). Tritium at

F. Goff; G. M. McMurtry

2000-01-01

108

The geochemistry of the stable carbon isotopes  

Microsoft Academic Search

Several hundred samples of carbon from various geologic sources have been analyzed in a new survey of the variation of the ratio C 13 \\/C 12 in nature. Mass spectrometric determinations were made on the instruments developed by H. C. and his co-workers utilizing two complete feed systems with magnetic switching to determine small differences in isotope ratios between samples

Harmon Craig

1953-01-01

109

New Stable Isotope Tropical Paleoclimate Proxies  

Microsoft Academic Search

Organized tropical rain systems such as tropical cyclones (TC) and mesoscale convective systems (MCS) produce both water vapor and rainfall with distinctly low isotope ratios. This lowering is caused by recyling of water in organized systems. Therefore, fresh water carbonate organisms have considerable potential to act as proxy recorders of these systems. Ostracoda are ephemeral making them especially attractive candidates.

J. R. Lawrence

2005-01-01

110

Assessment of Renal Function by the Stable Oxygen and Hydrogen Isotopes in Human Blood Plasma  

PubMed Central

Water (H2O) is the most abundant and important molecule of life. Natural water contains small amount of heavy isotopes. Previously, few animal model studies have shown that the isotopic composition of body water could play important roles in physiology and pathophysiology. Here we study the stable isotopic ratios of hydrogen (?2H) and oxygen (?18O) in human blood plasma. The stable isotopic ratio is defined and determined by ?sample?=?[(Rsample/RSTD)?1] * 1000, where R is the molar ratio of rare to abundant, for example, 18O/16O. We observe that the ?2H and the ?18O in human blood plasma are associated with the human renal functions. The water isotope ratios of the ?2H and ?18O in human blood plasma of the control subjects are comparable to those of the diabetes subjects (with healthy kidney), but are statistically higher than those of the end stage renal disease subjects (p<0.001 for both ANOVA and Student's t-test). In addition, our data indicate the existence of the biological homeostasis of water isotopes in all subjects, except the end stage renal disease subjects under the haemodialysis treatment. Furthermore, the unexpected water contents (?2H and ?18O) in blood plasma of body water may shed light on a novel assessment of renal functions.

Kuo, Tai-Chih; Wang, Chung-Ho; Lin, Hsiu-Chen; Lin, Yuan-Hau; Lin, Matthew; Lin, Chun-Mao; Kuo, Hsien-Shou

2012-01-01

111

General statistical framework for quantitative proteomics by stable isotope labeling.  

PubMed

The combination of stable isotope labeling (SIL) with mass spectrometry (MS) allows comparison of the abundance of thousands of proteins in complex mixtures. However, interpretation of the large data sets generated by these techniques remains a challenge because appropriate statistical standards are lacking. Here, we present a generally applicable model that accurately explains the behavior of data obtained using current SIL approaches, including (18)O, iTRAQ, and SILAC labeling, and different MS instruments. The model decomposes the total technical variance into the spectral, peptide, and protein variance components, and its general validity was demonstrated by confronting 48 experimental distributions against 18 different null hypotheses. In addition to its general applicability, the performance of the algorithm was at least similar than that of other existing methods. The model also provides a general framework to integrate quantitative and error information fully, allowing a comparative analysis of the results obtained from different SIL experiments. The model was applied to the global analysis of protein alterations induced by low H?O? concentrations in yeast, demonstrating the increased statistical power that may be achieved by rigorous data integration. Our results highlight the importance of establishing an adequate and validated statistical framework for the analysis of high-throughput data. PMID:24512137

Navarro, Pedro; Trevisan-Herraz, Marco; Bonzon-Kulichenko, Elena; Nez, Estefana; Martnez-Acedo, Pablo; Prez-Hernndez, Daniel; Jorge, Inmaculada; Mesa, Raquel; Calvo, Enrique; Carrascal, Montserrat; Hernez, Mara Luisa; Garca, Fernando; Brcena, Jos Antonio; Ashman, Keith; Abian, Joaqun; Gil, Concha; Redondo, Juan Miguel; Vzquez, Jess

2014-03-01

112

Modeling stable isotope transport in metamorphic and hydrothermal systems  

NASA Astrophysics Data System (ADS)

Stable isotopes are powerful tools for deciphering the fluid flow histories of metamorphic terrains. The nature of fluid flow, fluid sources, and fluid fluxes can be delineated in well constrained studies. Continuum mechanics models for stable isotope fluid-rock exchange were developed and used over the last three decades in an attempt to accurately interpret the signatures left behind by fluid flow in the earths crust. The efforts have been hampered by the realization that the exchange of many stable isotopes, e.g. oxygen and carbon, by intracrystalline diffusion, hence without re-organization of the crystal lattice, appears to be too slow to achieve significant exchange. This should lead to relatively flat isotopic exchange profiles on hand-, outcrop, or aureole scale. Nevertheless, isotopic fronts are typically sharp (sub mm to cm scale), when measured in the field. This has lead to the suggestion that these sharp fronts correspond to the sides of infiltration fronts, implying the data to have been collected at a high angle to the infiltration direction. Nevertheless, the fact that the oxygen and carbon fronts are located at the same place is not explained by this. A review of published carbon and oxygen data reveals that many contact aureoles show linear trends in oxygen-carbon isotope ratio diagrams for carbonate sample suits. This implies that the fluid composition infiltrating the aureoles had essentially an X(CO2) of 0.5. This is in contrast to skarn mineralogy developed, which requires a water-rich fluid, in agreement with the general notion that igneous fluids are water-rich. These and other observations indicate that the mass transport equation used for stable isotope exchange needs to be improved to model appropriately the actual isotope kinetics during fluid-rock exchange. Detailed isotope studies on systems where net transport reactions are driven by mass transport have led us to identify different exchange mechanisms, including: a) the stable isotope exchange is given by instantaneous mass balance written for the isotope during reaction; b) equilibrium precipitation of products, but slow exchange kinetics for reactants. These observations require that the reactive term in the stable isotope reactive transport equation is re-written to include the net transfer reactions, which in turn implies the solution of the transport equation for the elements driving the reaction.

Baumgartner, L. P.; Mueller, T.; Skora, S.; Begue, F.

2007-12-01

113

Use of Stable Isotopes in Forensic Analysis of Microorganisms  

SciTech Connect

The use of isotopic signatures for forensic analysis of biological materials is well-established, and the same general principles that apply to interpretation of stable isotope content of C, N, O, and H apply to the analysis of microorganisms. Heterotrophic microorganisms derive their isotopic content from their growth substrates, which are largely plant and animal products, and the water in their culture medium. Thus the isotope signatures of microbes are tied to their growth environment. The C, N, O, and H isotope ratios of spores have been demonstrated to constitute highly discriminating signatures for sample matching. They can rule out specific samples of media and/or water as possible production media, and can predict isotope ratio ranges of the culture media and water used to produce a given sample. These applications have been developed and tested through analyses of approximately 250 samples of Bacillus subtilis spores and over 500 samples of culture media, providing a strong statistical basis for data interpretation. A Bayesian statistical framework for integrating stable isotope data with other types of signatures derived from microorganisms has been able to characterize the culture medium used to produce spores of various Bacillus species, leveraging isotopic differences in different medium types and demonstrating the power of data integration for forensic investigations.

Kreuzer-Martin, Helen W.; Hegg, Eric L.

2012-01-18

114

Stable Carbon Isotope Fractionation by Methylotrophic Methanogenic Archaea  

PubMed Central

In natural environments methane is usually produced by aceticlastic and hydrogenotrophic methanogenic archaea. However, some methanogens can use C1 compounds such as methanol as the substrate. To determine the contributions of individual substrates to methane production, the stable-isotope values of the substrates and the released methane are often used. Additional information can be obtained by using selective inhibitors (e.g., methyl fluoride, a selective inhibitor of acetoclastic methanogenesis). We studied stable carbon isotope fractionation during the conversion of methanol to methane in Methanosarcina acetivorans, Methanosarcina barkeri, and Methanolobus zinderi and generally found large fractionation factors (?83 to ?72). We further tested whether methyl fluoride impairs methylotrophic methanogenesis. Our experiments showed that even though a slight inhibition occurred, the carbon isotope fractionation was not affected. Therefore, the production of isotopically light methane observed in the presence of methyl fluoride may be due to the strong fractionation by methylotrophic methanogens and not only by hydrogenotrophic methanogens as previously assumed.

Penger, Jorn; Conrad, Ralf

2012-01-01

115

Stable platinum isotope measurements in presolar nanodiamonds by TEAMS.  

PubMed

Nanodiamonds are stardust grains commonly found in primitive meteorites. They survived the formation of the solar system and kept their own individuality. Measurements of trace-element isotopic signatures in these grains will help understanding heavy element nucleosynthesis in massive stars and dust formation from their ejecta. We have continued previous attempts to search for stable Pt isotope anomalies in nanodiamonds via trace element accelerator mass spectrometry (TEAMS). The installation of a new injector beam line at the VERA facility allowed studying low traces of stable elements in different materials. Moreover, recent experiments showed that VERA provides the required measurement precision together with a low Pt machine background. Here, we observed for the first time an indication for enhancements of (198)Pt/(195)Pt isotope ratios in two diamond residues prepared by different chemical separation techniques from the Allende meteorite. Variations in other isotopic ratios were within analytical uncertainty, and no anomaly was identified in a third diamond fraction. PMID:23565017

Wallner, A; Melber, K; Merchel, S; Ott, U; Forstner, O; Golser, R; Kutschera, W; Priller, A; Steier, P

2013-01-01

116

Stable isotope geochemistry of East African waters. [Abstract only  

SciTech Connect

Lakes and Rivers in East Africa have varied stable isotopic compositions. Lakes exhibit enriched delta13-C values (-2 to +5%), while their inflowing rivers show depleted values (-15 to -8%). Hot springs and standing pools of water have intermediate values. Some small lakes are extremely variable in delta18-0 or deltaD (+2 to +8% and +20 to +40%, respectively for Lake Naivasha), whereas larger lakes are relatively constant for long periods of time (+5.6 to 6.1 and +36 to 40, respectively for Lake Turkana). Isotopic values are unrelated to salinity for comparison between lakes. Stable isotopes also reveal the sources of hot spring discharges: the Kapedo hot springs probably originate from Maralel and not from Lake Baringo as local legend has it; the hot springs north of Lake Naivasha are of meteoric origin while those to the south of Lake Naivasha have similar isotopic compositions to Lake Naivasha.

Sayer, M.D.; Cerling, T.E.; Bowman, J.R.

1983-03-01

117

From birds to butterflies: animal movement patterns and stable isotopes.  

PubMed

Establishing patterns of movement of wild animals is crucial for our understanding of their ecology, life history and behavior, and is a prerequisite for their effective conservation. Advances in the use of stable isotope markers make it possible to track a diversity of animal species in a variety of habitats. This approach is revolutionizing the way in which we make connections between phases of the annual cycle of migratory animals. However, researchers must exercise care in their application of isotopic methods. Here, we review stable isotope patterns in nature and discuss recent tracking applications in a range of taxa. To aid in the interpretation and design of effective and insightful isotope movement studies, we discuss a series of key issues and assumptions. This exciting field will advance rapidly if researchers consider these aspects of study design and interpretation carefully. PMID:16701265

Rubenstein, Dustin R; Hobson, Keith A

2004-05-01

118

Stable platinum isotope measurements in presolar nanodiamonds by TEAMS  

PubMed Central

Nanodiamonds are stardust grains commonly found in primitive meteorites. They survived the formation of the solar system and kept their own individuality. Measurements of trace-element isotopic signatures in these grains will help understanding heavy element nucleosynthesis in massive stars and dust formation from their ejecta. We have continued previous attempts to search for stable Pt isotope anomalies in nanodiamonds via trace element accelerator mass spectrometry (TEAMS). The installation of a new injector beam line at the VERA facility allowed studying low traces of stable elements in different materials. Moreover, recent experiments showed that VERA provides the required measurement precision together with a low Pt machine background. Here, we observed for the first time an indication for enhancements of 198Pt/195Pt isotope ratios in two diamond residues prepared by different chemical separation techniques from the Allende meteorite. Variations in other isotopic ratios were within analytical uncertainty, and no anomaly was identified in a third diamond fraction.

Wallner, A.; Melber, K.; Merchel, S.; Ott, U.; Forstner, O.; Golser, R.; Kutschera, W.; Priller, A.; Steier, P.

2013-01-01

119

Stable isotopes determination in some Romanian wines.  

PubMed

This paper presents a study concerning the isotopic fingerprint ((18)O and (13)C) of some wines prepared from relevant Romanian grape varieties (e.g. Feteasca Alba (FA), Feteasca Regala (FR) and Cabernet Sauvignon (CS)) obtained in different vintage years (2002, 2003, 2004, 2007 and 2008). These wines were obtained from different vineyards having a significant role in the wine market: Cotesti, Tohani, Stefanesti, Aiud, Cotnari, Bucium, Murfatlar, Bujoru, Dragasani and Valea Calugareasca. Several observations related to the dependence of isotope ratios on geographical origin and climatic conditions were drawn. The authentic wines obtained from the FA grape variety from six different vineyards showed ?(18)O values in the range of+3.28 (Cotesti region - 4538'N/2704'E) to-2.60 (Aiud region - 4619'N/2345'E). The ?(13)C values were very similar for all the samples with an average of about-26 . The difference between the ?(18)O values was due to the different climatic zones, which have an influence on the ?(18)O values of wine water. For the wine variety CS obtained from the Dealu Mare-Tohani vineyard, production years 2003 and 2004, a greater difference in the ?(18)O values of wine water ranging from 1.89 (in 2004) to 5.35 (in 2003) was noted. This difference is explained by the different mean annual temperatures in 2003 and 2004. PMID:22397311

Magdas, Dana Alina; Cuna, Stela; Cristea, Gabriela; Ionete, Roxana Elena; Costinel, Diana

2012-06-01

120

The Measurement of Iron-Group Isotopic Abundances in the Cosmic Rays Using the Magpie Detector  

NASA Astrophysics Data System (ADS)

This thesis details the analysis of data from the MAGPIE detector, a balloon-borne detector designed to measure cosmic ray isotope abundances between 300 and 900 MeV/a ? in the Fe group. MAGPIE consists of a magnetic spectrometer for measuring particle rigidity, and nine stacks of CR-39 plastic nuclear track detectors for measuring charge and velocity. After an Antarctic flight in December of 1991 during which ~2000 Fe nuclei were collected, damage occurred to the spectrometer during the landing of the balloon payload, limiting the analysis to cosmic ray particles that stop in the plastic stack. This limited the energy range of data to between 100 MeV/a ? and 400 MeV/a ? for Fe group elements. The measurement of Fe group isotopes is an important one. Because nuclei from this group have the highest binding energy of all the elements, they represent the primary products during late stellar nucleosynthesis. This characteristic makes Fe group isotopes unique in their ability to probe the interior environment during the final stages of stellar evolution. In addition, the primary decay channel by e- capture for some of the Ni and Co isotopes makes these isotopes ideal for probing the time delay between production of cosmic rays and their acceleration. Finally, the radioactive isotope 54Mn has a mean lifetime that is comparable to residence time of lighter elements in the galaxy, which has been measured using the 10Be isotopic abundance. Both of these abundances are produced primarily through spallation during propagation, and Mn can measure the average density of the propagation medium and residence time for Fe group elements with isotopic abundance measurements of stable spallation products. After etching, the MAGPIE CR-39 plastic was scanned for tracks using an automated microscope and image processing system. This system offers a data acquisition method that is as efficient and much quicker than techniques using a microscope and reticle. Cosmic ray data were separated from background noise pits using a sheet aligning algorithm that searched for tracks having similar shape and size. I performed an extensive error analysis on the MAGPIE detector, scanning system, and etching facilities. Contributions to mass resolution from the last two categories are neglible. I found that the intrinsic charge resolution of the plastic has been severely degraded over time. This resolution fundamentally limited the ability of this detector to resolve charges to ?Z>= 0.4 e. The data were successfully fit to a charge distribution, but mass resolution was not adequate to generate a mass distribution. There appears to be an underabundance of Fe data, possibly from a systematic error.

Yanasak, Nathan Eugene

121

Stable isotope composition of the meteoric precipitation in Croatia.  

PubMed

The precipitation is the input into the water system. Its stable isotope composition has to be known for the proper use and management of water resources. Croatia is not well represented in the Global Network of Isotopes in Precipitation (GNIP) database, and the geomorphology of the country causes specific local conditions. Therefore, at the Stable Isotope Laboratory (SILab), Rijeka, we monitor the stable isotope composition (?(18)O, ?(2)H) of precipitation. Since ?(18)O and ?(2)H are well correlated, we concentrate the discussion on the ?(18)O distribution. Together with GNIP, our database contains 40 stations in Croatia and in the neighbouring countries. Their different latitudes, longitudes and altitudes give information of great detail, including the influence of the topographic structure on the precipitation in the south-eastern part of Europe, as well as the complex interplay of the different climate conditions in the area. Within a few hundred kilometres, the stable isotope values display a significant change from the maritime character in the south (mean ?(18)O around-6 to-8) to the continental behaviour in the north (mean ?(18)O around-8 to-11). Depending on the location, the mean ?(18)O values vary with altitude at a rate of approximately-0.2/100 m and-0.4/100 m, respectively. Also the deuterium excess has been found to depend on location and altitude. The data are being used to construct a ?(18)O map for the entire area. PMID:23937110

Hunjak, Tamara; Lutz, Hans O; Roller-Lutz, Zvjezdana

2013-01-01

122

Copper stable isotopes to trace copper behavior in wetland systems.  

PubMed

Wetlands are reactive zones of the landscape that can sequester metals released by industrial and agricultural activities. Copper (Cu) stable isotope ratios (?(65)Cu) have recently been used as tracers of transport and transformation processes in polluted environments. Here, we used Cu stable isotopes to trace the behavior of Cu in a stormwater wetland receiving runoff from a vineyard catchment (Alsace, France). The Cu loads and stable isotope ratios were determined in the dissolved phase, suspended particulate matter (SPM), wetland sediments, and vegetation. The wetland retained >68% of the dissolved Cu and >92% of the SPM-bound Cu, which represented 84.4% of the total Cu in the runoff. The dissolved Cu became depleted in (65)Cu when passing through the wetland (?(65)Cuinlet-outlet from 0.03 to 0.77), which reflects Cu adsorption to aluminum minerals and organic matter. The ?(65)Cu values varied little in the wetland sediments (0.04 0.10), which stored >96% of the total Cu mass within the wetland. During high-flow conditions, the Cu flowing out of the wetland became isotopically lighter, indicating the mobilization of reduced Cu(I) species from the sediments and Cu reduction within the sediments. Our results demonstrate that the Cu stable isotope ratios may help trace Cu behavior in redox-dynamic environments such as wetlands. PMID:24787375

Babcsnyi, Izabella; Imfeld, Gwenal; Granet, Mathieu; Chabaux, Franois

2014-05-20

123

Elemental and isotopic abundances in the solar wind  

NASA Technical Reports Server (NTRS)

The use of collecting foils and lunar material to assay the isotopic composition of the solar wind is reviewed. Arguments are given to show that lunar surface correlated gases are likely to be most useful in studying the history of the solar wind, though the isotopic abundances are thought to give a good approximation to the solar wind composition. The results of the analysis of Surveyor material are also given. The conditions leading to a significant component of the interstellar gas entering the inner solar system are reviewed and suggestions made for experimental searches for this fraction. A critical discussion is given of the different ways in which the basic solar composition could be modified by fractionation taking place between the sun's surface and points of observation such as on the Moon or in interplanetary space. An extended review is made of the relation of isotopic and elemental composition of the interplanetary gas to the dynamic behavior of the solar corona, especially processes leading to fractionation. Lastly, connection is made between the subject of composition, nucleosynthesis and the convective zone of the sun, and processes leading to modification of initial accretion of certain gases on the Earth and Moon.

Geiss, J.

1972-01-01

124

Mercury abundances and isotopic compositions in the Murchison (CM) and Allende (CV) carbonaceous chondrites  

NASA Astrophysics Data System (ADS)

The abundance and isotopic composition of Hg was determined in bulk samples of both the Murchison (CM) and Allende (CV) carbonaceous chondrites using single- and multi-collector inductively coupled plasma mass spectrometry (ICP-MS). The bulk abundances of Hg are 294 15 ng/g in Murchison and 30.0 1.5 ng/g in Allende. These values are within the range of previous measurements of bulk Hg abundances by neutron activation analysis (NAA). Prior studies suggested that both meteorites contain isotopically anomalous Hg, with ? 196/202Hg values for the anomalous, thermal-release components from bulk samples ranging from -260 to +440 in Murchison and from -620 to +540 in Allende (Jovanovic and Reed, 1976a; 1976b; Kumar and Goel, 1992). Our multi-collector ICP-MS measurements suggest that the relative abundances of all seven stable Hg isotopes in both meteorites are identical to terrestrial values within 0.2 to 0.5 . On-line thermal-release experiments were performed by coupling a programmable oven with the single-collector ICP-MS. Powdered aliquots of each meteorite were linearly heated from room temperature to 900C over twenty-five minutes under an Ar atmosphere to measure the isotopic composition of Hg released from the meteorites as a function of temperature. In separate experiments, the release profiles of S and Se were determined simultaneously with Hg to constrain the Hg distribution within the meteorites and to evaluate the possibility of Se interferences in previous NAA studies. The Hg-release patterns differ between Allende and Murchison. The Hg-release profile for Allende contains two distinct peaks, at 225 and 343C, whereas the profile for Murchison has only one peak, at 344C. No isotopically anomalous Hg was detected in the thermal-release experiments at a precision level of 5 to 30 , depending on the isotope ratio. In both meteorites the Hg peak at 340C correlates with a peak in the S-release profile. This correlation suggests that Hg is associated with S-bearing phases and, thus, that HgS is a major Hg-bearing phase in both meteorites. The Hg peak at 225C for Allende is similar to release patterns of physically adsorbed Hg on silicate and metal grains. Prior studies suggested that the isotopic anomalies reported from NAA resulted from interference between 203Hg and 75Se. However, the amount of Se released from both meteorites, relative to Hg, is insufficient to produce all of the observed anomalies.

Lauretta, Dante S.; Klaue, Bjoern; Blum, Joel D.; Buseck, Peter R.

2001-09-01

125

The iron stable isotope fingerprint of the human diet.  

PubMed

The stable isotopes of iron disclose the metabolic pathways of iron within the human food chain. We have measured with precise multicollector ICP-MS the iron concentrations and stable isotope composition of 60 food products that are representative of the average German diet. We find that vegetables fall within the range typical of strategy I plants (-0.1 to -1.4 in ?(56)Fe), crop products and processed crop foods into the range typical of strategy II plants (-0.6 to +0.4), and animal products into the (54)Fe-enriched range known for animal tissue and blood (-1.1 to -2.7). Weighting these isotope compositions by the average iron dietary sources, we find a representative composition of European vegetarian diet of -0.45, whereas that of omnivores is -0.82. For human blood, known to be enriched in light iron isotopes, we find fractionation factors for iron absorption of -2.0 and -2.3 for vegetarians (female and male, respectively) and -1.3 and -1.5 for omnivores (female and male, respectively). Knowing these fractionation factors is a prerequisite for using stable iron isotope ratios in blood as monitors of intestinal iron uptake regulation. PMID:24188194

von Blanckenburg, Friedhelm; Noordmann, Janine; Guelke-Stelling, Monika

2013-12-11

126

STABLE ISOTOPES AS INDICATORS OF SOIL WATER DYNAMICS IN WATERSHEDS  

EPA Science Inventory

Stream water quality and quantity depend on discharge rates of water and nutrients from soils. However, soil-water storage is very dynamic and strongly influenced by plants. We analyzed stable isotopes of oxygen and hydrogen to quantify spatial and temporal changes in evaporati...

127

Development of stable isotope mixing models in ecology - Fremantle  

EPA Science Inventory

More than 40 years ago, stable isotope analysis methods used in geochemistry began to be applied to ecological studies. One common application is using mathematical mixing models to sort out the proportional contributions of various sources to a mixture. Examples include contri...

128

Development of stable isotope mixing models in ecology - Sydney  

EPA Science Inventory

More than 40 years ago, stable isotope analysis methods used in geochemistry began to be applied to ecological studies. One common application is using mathematical mixing models to sort out the proportional contributions of various sources to a mixture. Examples include contri...

129

Development of stable isotope mixing models in ecology - Dublin  

EPA Science Inventory

More than 40 years ago, stable isotope analysis methods used in geochemistry began to be applied to ecological studies. One common application is using mathematical mixing models to sort out the proportional contributions of various sources to a mixture. Examples include contri...

130

Apparatus and method for monitoring of gas having stable isotopes  

DOEpatents

Gas having stable isotopes is monitored continuously by using a system that sends a modulated laser beam to the gas and collects and transmits the light not absorbed by the gas to a detector. Gas from geological storage, or from the atmosphere can be monitored continuously without collecting samples and transporting them to a lab.

Clegg, Samuel M; Fessenden-Rahn, Julianna E

2013-03-05

131

From birds to butterflies: animal movement patterns and stable isotopes  

Microsoft Academic Search

Establishing patterns of movement of wild animals is crucial for our understanding of their ecology, life history and behavior, and is a prerequisite for their effective conservation. Advances in the use of stable isotope markers make it possible to track a diversity of animal species in a variety of habitats. This approach is revolutionizing the way in which we make

Dustin R. Rubenstein; Keith A. Hobson

2004-01-01

132

Standards for stable isotope measurements in natural compounds  

Microsoft Academic Search

RESEARCH based on stable isotope variations in natural compounds is expanding in scientific fields such as geochemistry, hydrology, environmental studies and biochemistry. However, intercomparison of results obtained in different laboratories is often not fully reliable and therefore to improve the intercalibration of deuterium and 18O measurements in natural waters, two water standards have been distributed by the International Atomic Energy

R. Gonfiantini

1978-01-01

133

Monte Carlo spreadsheet modeling of stable isotope biosynthesis  

Microsoft Academic Search

Metabolic physiologists often introduce stable isotopes, atoms containing additional neutrons, into molecules during biosynthesis. This tags the newly synthesized material by altering its mass. Monte Carlo analysis is implemented on a popular spreadsheet to analyze this process. An example is provided where acetoacetate is synthesized by condensation of two acetate moieties. The precursor acetate is present as a mixture of

Thomas M. Masterson; Joanne K. Kelleher

1996-01-01

134

Stable Isotope Sales: Mound Customer and Shipment Summaries, FY 1986.  

National Technical Information Service (NTIS)

A listing is given of Mound's sales of stable isotopes of noble gases, carbon, oxygen, nitrogen, chlorine, and sulfur for fiscal year 1986. Purchasers are listed alphabetically and are divided into domestic and foreign groups. Cross-reference indexes by l...

L. R. Kramer K. A. Flayler

1988-01-01

135

Stable Isotope Sales: Mound Customer and Shipment Summaries, FY 1982.  

National Technical Information Service (NTIS)

A listing is given of Mound's sales of stable isotopes of noble gases, carbon, oxygen, nitrogen, chlorine, and sulfur for Fiscal Year 1982. Purchasers are listed alphabetically and are divided into domestic and foreign groups. A cross-reference index by l...

A. H. Ruwe

1983-01-01

136

Stable isotopes of captive cetaceans (killer whales and bottlenose dolphins).  

PubMed

There is currently a great deal of interest in using stable isotope methods to investigate diet, trophic level and migration in wild cetaceans. In order to correctly interpret the results stemming from these methods, it is crucial to understand how diet isotopic values are reflected in consumer tissues. In this study, we investigated patterns of isotopic discrimination between diet and blood constituents of two species of cetaceans (killer whale, Orcinus orca, and bottlenose dolphin, Tursiops truncatus) fed controlled diets over 308 and 312 days, respectively. Diet discrimination factors (?; mean s.d.) for plasma were estimated to ?(13)C=2.30.6 and ?(15)N=1.80.3, respectively, for both species and to ?(13)C=2.70.3 and ?(15)N=0.50.1 for red blood cells. Delipidation did not have a significant effect on carbon and nitrogen isotopic values of blood constituents, confirming that cetacean blood does not serve as a reservoir of lipids. In contrast, carbon isotopic values were higher in delipidated samples of blubber, liver and muscle from killer whales. The potential for conflict between fisheries and cetaceans has heightened the need for trophic information about these taxa. These results provide the first published stable isotope incorporation data for cetaceans, which are essential if conclusions are to be drawn on issues concerning trophic structures, carbon sources and diet reconstruction. PMID:21270301

Caut, Stphane; Laran, Sophie; Garcia-Hartmann, Emmanuel; Das, Krishna

2011-02-15

137

Stable isotope mass balance of lakes: a contemporary perspective (Invited)  

NASA Astrophysics Data System (ADS)

Stable isotopes are widely used in paleoclimate studies of lakes to reconstruct water balance and/or climatic conditions, but there are a variety of assumptions that are often made to simplify and operationalize the isotope transfer functions. Based on recent studies conducted on a wide range of lakes across North America, as well as a comprehensive compilation of existing data from around the globe, we present contemporary examples of stable-isotope mass-balance studies based on site-specific to regional lake datasets. We illustrate the need in most cases to understand and characterize the local climate and hydrological setting to accurately model the observed isotopic enrichment, as well as the importance of amount-weighting liquid fluxes and evaporation-flux-weighting vapour fluxes. Potential complications due to atmospheric feedback are also explored by presenting a new analysis of the Laurentian Great Lakes where we apply a model that considers the timing of evaporation, which occurs mainly in the winter, and accounts for downwind lake effects, humidity and isotopic build-up in the boundary layer. One future opportunity of lake-based paleoclimate research may be to develop controlled studies that allow for specific atmospheric or water-balance processes to be targeted and reconstructed. We also show relationships between selected water quality indicators and isotope-based water balance indicators that should, in principle, be preserved in the lake sediment record.

Gibson, J. J.; Birks, S. J.; YI, Y.; Jasechko, S.

2013-12-01

138

Heavy element stable isotope ratios: analytical approaches and applications.  

PubMed

Continuous developments in inorganic mass spectrometry techniques, including a combination of an inductively coupled plasma ion source and a magnetic sector-based mass spectrometer equipped with a multiple-collector array, have revolutionized the precision of isotope ratio measurements, and applications of inorganic mass spectrometry for biochemistry, geochemistry, and marine chemistry are beginning to appear on the horizon. Series of pioneering studies have revealed that natural stable isotope fractionations of many elements heavier than S (e.g., Fe, Cu, Zn, Sr, Ce, Nd, Mo, Cd, W, Tl, and U) are common on Earth, and it had been widely recognized that most physicochemical reactions or biochemical processes induce mass-dependent isotope fractionation. The variations in isotope ratios of the heavy elements can provide new insights into past and present biochemical and geochemical processes. To achieve this, the analytical community is actively solving problems such as spectral interference, mass discrimination drift, chemical separation and purification, and reduction of the contamination of analytes. This article describes data calibration and standardization protocols to allow interlaboratory comparisons or to maintain traceability of data, and basic principles of isotope fractionation in nature, together with high-selectivity and high-yield chemical separation and purification techniques for stable isotope studies. PMID:23397089

Tanimizu, Masaharu; Sohrin, Yoshiki; Hirata, Takafumi

2013-03-01

139

Modeled and measured stable isotope data in Siberian tree rings  

NASA Astrophysics Data System (ADS)

Stable isotopes in tree-rings are widely used for the reconstruction of environmental conditions, but more information could be extracted when using mechanistic models for their interpretation. Tree-ring width, cell wall structure and stable carbon as well as oxygen isotope analyses in tree wood and cellulose were carried out for four larch trees (Larix cajanderi Mayr) from northeastern Yakutia (69N, 148E) during the period from 1945 to 2004 and these data compared with several models. Based on a biochemical model of photosynthesis and modified model of stomatal conductance our work provides intra-annual dynamics of carbon content in photoassimilates and isotope composition in tree-rings depending on climatic factors. The mechanistic Roden-Lin-Ehleringer model was used to quantify both the physical and biochemical fractionation events associated with hydrogen and oxygen isotope ratios in tree-ring cellulose. Simulation results were compared with measured data. Predictions of carbon isotope ratios from Fritts, ORCHIDEE and LPX models were consistent with measured data. The Roden-Lin-Ehleringer oxygen model allowed the prediction of humidity and source water enrichment as well as oxygen isotope effects associated with leaf water enrichment. This work was supported by Marie Curie Fellowships (EU-ISOTREC 235122; 909122) awarded to Sidorova Olga and a grant of Russian Scientific School 5327.2012.4.

Sidorova, Olga; Siegwolf, Rolf; Kupzova, Anna; Launois, Thomas; Peylin, Philippe; Spahni, Renato; Bryukhanova, Marina; Roden, John; Saurer, Matthias; Shashkin, Aleksander

2013-04-01

140

Light stable isotope analysis of meteorites by ion microprobe  

NASA Technical Reports Server (NTRS)

The main goal was to develop the necessary secondary ion mass spectrometer (SIMS) techniques to use a Cameca ims-4f ion microprobe to measure light stable isotope ratios (H, C, O and S) in situ and in non-conducting mineral phases. The intended application of these techniques was the analysis of meteorite samples, although the techniques that have been developed are equally applicable to the investigation of terrestrial samples. The first year established techniques for the analysis of O isotope ratios (delta O-18 and delta O-17) in conducting mineral phases and the measurement of S isotope ratios (delta S-34) in a variety of sulphide phases. In addition, a technique was developed to measure delta S-34 values in sulphates, which are insulators. Other research undertaken in the first year resulted in SIMS techniques for the measurement of wide variety of trace elements in carbonate minerals, with the aim of understanding the nature of alteration fluids in carbonaceous chondrites. In the second year we developed techniques for analyzing O isotope ratios in nonconducting mineral phases. These methods are potentially applicable to the measurement of other light stable isotopes such as H, C and S in insulators. Also, we have further explored the analytical techniques used for the analysis of S isotopes in sulphides by analyzing troilite in a number of L and H ordinary chondrites. This was done to see if there was any systematic differences with petrological type.

Mcsween, Harry Y., Jr.

1994-01-01

141

Prospects for clinical cancer metabolomics using stable isotope tracers  

PubMed Central

Metabolomics provides a readout of the state of metabolism in cells or tissue and their responses to external perturbations. For this reason, the approach has great potential in clinical diagnostics. For more than two decades,, we have been using stable isotope tracer approaches to probe cellular metabolism in greater detail. The ability to enrich common compounds with rare isotopes such as carbon (13C) and nitrogen (15N) is the only practical means by which metabolic pathways can be traced, which entails following the fate of individual atoms from the source molecule to products via metabolic transformation. Changes in regulation of pathways are therefore captured by this approach, which leads to deeper understanding of the fundamental biochemistry of cells. Using lessons learned from pathways tracing in cells and organs, we have been applying this methodology to human cancer patients in a clinical setting. Here we review the methodologies and approaches to stable isotope tracing in cells, animal models and in humans subjects.

Lane, Andrew N.; Fan, Teresa W-M; Higashi, Richard M.; Tan, Jinlian; Bousamra, Michael; Miller, Donald M.

2009-01-01

142

Stable isotope analysis of breath using the optogalvanic effect  

NASA Astrophysics Data System (ADS)

A new technique based on the optogalvanic effect has been developed for the measurement of stable isotope ratios in the carbon dioxide of exhaled breath. Data obtained before and after ingestion of harmless stable isotope labeled compounds, metabolized to carbon dioxide, can be used for sensitive noninvasive diagnostics of various disease conditions. The technique uses the specificity of laser resonance spectroscopy and achieves sensitivity and accuracy typical of sophisticated isotope ratio mass spectrometers. Using fixed frequency carbon dioxide lasers, 13C/12C ratios can be determined with a precision of 2 ppm with 100 second averaging times. Multiple samples can be analyzed simultaneously providing real time continuous calibration. In a first application, analysis of 13C/12C ratios in exhaled human breath after ingestion of 13C labeled urea is being developed as a diagnostic for the bacterium H-pylori, known to be the causative agent for most peptic and duodenal ulcers.

Murnick, Daniel E.; Colgan, M. J.; Lie, H. P.; Stoneback, D.

1996-05-01

143

Biomedical research applications of electromagnetically separated enriched stable isotopes  

NASA Astrophysics Data System (ADS)

The current and projected annual requirements through 1985 for stable isotopes enriched by electromagnetic separation methods were reviewed for applications in various types of biomedical research: (1) medical radiosiotope production, labeled compounds, and potential radio-pharmaceuticals; (2) nutrition, food science, and pharmacology: (3) metallobiochemistry and environmental toxicology; (4) nuclear magnetic resonance, electron paramagnetic resonance, and moessbauer spectroscopy in biochemical, biophysical, and biomedical research; and (5) miscellaneous advances in radioactive and nonradioactive tracer technology. Radioisotopes available from commercial sources or routinely used in clinical nuclear medicine were excluded. Current requirements for enriched stable isotopes in biomedical research are not being satisfied. Severe shortages exist for Mg 26, Ca 43, Zn 70, Se 76, Se 77, Se 78, Pd 102, Cd 111, Cd 113, and Os 190. Many interesting and potentially important investigations in biomedical research require small quantities of specific elements at high isotopic enrichments.

Lambrecht, R. M.

144

Hydrological investigation of a multi-stratified pit lake using radioactive and stable isotopes combined with hydrometric monitoring  

NASA Astrophysics Data System (ADS)

Pit lakes connected with mine tunnels and shafts may display unique stratification features.A multi-isotopic study has been conducted in a meromictic pit lake with complex stratification.Tritium abundance has provided a plausible lake flooding model.?18O and ?2H isotopes combined with hydrological studies have solved the pit lake dynamics.The physical structure of the lake is very stable and not affected by groundwater flow.

Snchez-Espaa, Javier; Diez Ercilla, Marta; Prez Cerdn, Fernando; Yusta, Iaki; Boyce, Adrian J.

2014-04-01

145

Mercury Abundances and Isotopic Compositions in the Murchison (CM) and Allende (CV)Carbonaceous Chondrites  

NASA Technical Reports Server (NTRS)

The abundance and isotopic composition of Hg was determined in bulk samples of both the Murchison (CM) and Allende (CV) carbonaceous chondrites using single- and multi-collector inductively coupled plasma mass spectrometry (ICP-MS). The bulk abundances of Hg are 294 6 15 ng/g in Murchison and 30.0 6 1.5 ng/g in Allende. These values are within the range of previous measurements of bulk Hg abundances by neutron activation analysis (NAA). Prior studies suggested that both meteorites contain isotopically anomalous Hg, with d l 96/202Hg values for the anomalous, thermal-release components from bulk samples ranging from 2260 %o to 1440 9/00 in Murchison and from 2620 9/00 to 1540 9/00 in Allende (Jovanovic and Reed, 1976a; 1976b; Kumar and Goel, 1992). Our multi-collector ICP-MS measurements suggest that the relative abundances of all seven stable Hg isotopes in both meteorites are identical to terrestrial values within 0.2 to 0.5 9/00m. On-line thermal-release experiments were performed by coupling a programmable oven with the singlecollector ICP-MS. Powdered aliquots of each meteorite were linearly heated from room temperature to 900 C over twenty-five minutes under an Ar atmosphere to measure the isotopic composition of Hg released fiom the meteorites as a h c t i o n of temperature. In separate experiments, the release profiles of S and Se were determined simultaneously with Hg to constrain the Hg distribution within the meteorites and to evaluate the possibility of Se interferences in previous NAA studies. The Hg-release patterns differ between Allende and Murchison. The Hg-release profile for Allende contains two distinct peaks, at 225" and 343"C, whereas the profile for Murchison has only one peak, at 344 C. No isotopically anomalous Hg was detected in the thermal-release experiments at a precision level of 5 to 30 9/00, depending on the isotope ratio. In both meteorites the Hg peak at ;340"C correlates with a peak in the S-release profile. This correlation suggests that Hg is associated with S-bearing phases and, thus, that HgS is a major Hg-bearing phase in both meteorites. The Hg peak at 225 C for Allende is similar to release patterns of physically adsorbed Hg on silicate and metal grains.

Lauretta, D. S.; Klaue, B.; Blum, J. D.; Buseck, P. R.

2001-01-01

146

Stable Isotope Fractionation of Cr in Carbonaceous and Ordinary Chondrites  

NASA Astrophysics Data System (ADS)

Difficulties with chemical separation and mass spectrometry combined with little expectation of isotopic fractionation at high temperature left the stable isotope geochemistry of Cr almost unknown [1]. The search for ^{53}Cr excess resulting from the decay of the radioactive nuclide ^{53}Mn (T1/2 = 3.5 My) was very successful but the small amount of data produced to date attests to the particularly difficult measurement by TIMS. This preliminary report describes evidence of mass-dependent fractionation of the stable Cr isotopes 50, 52, and 53 as measured by MC-ICPMS in meteorites relative to SRM 979 Cr standard. Cr was purified using cation-exchange chemistry. The yield is ~100 %. The samples were run on the Nu- Plasma HR of UC Davis in pseudo high-resolution mode. The absence of isotopic fractionation induced by the chemical purification has been double checked by 1) processing the standard through the column and 2) running the same sample several times through the columns. In both cases, we observe no difference in the measured isotopic ratio. The external reproducibility, estimated from 13 replicates of Bjurbole, is 50 ppm. The range of the fractionation per mass unit among 7 carbonaceous chondrites (CI, CM, CO, CV and CK) and 5 ordinary chondrites (H, L and LL) is 0.3 . Individual chondrules from Chainpur and Bjurbole have a wider range (0.6 ). All the chondrites analyzed so far are isotopically lighter than the bulk silicate earth (? ^{50/52}Cr=0, [1]). As for Zn [2], Cr isotopes seem to be heavier in ordinary chondrites (-0.23 ) than in carbonaceous chondrites (-0.35 ). Also as for Zn and Cu [2-3], Cr stable isotopes in carbonaceous chondrites are correlated with ? 17O, suggesting a mixing between an isotopically heavy component and an isotopically light one. The correlation between mass-dependent fractionation of Cr and non-mass-dependent ? 17O requires attention and adequate interpretation. References: [1] Johnson and Bullen, 2004, Review in Mineralogy and Geochemistry. [2] Luck et al., 2005 GCA. [3] Luck et al., 2003 GCA.

Moynier, F.; Jacobsen, B.; Yin, Q.

2006-12-01

147

The abundances of elements and isotopes in the solar wind  

NASA Technical Reports Server (NTRS)

Solar wind abundances have now been measured for eleven elements and the isotopes of the noble gases. Aside from solar wind protons and alpha particles, which have been studied extensively since the 1960's, information for heavier elements is limited. Nevertheless, two effects stand out. First is the enrichment of abundances of elements with low first ionization potential (FIP), most likely the combined result of an atom-ion separation process in the upper chromosphere, and a marginal coupling of low-charge-state heavy ions to protons and alphas during the acceleration of the solar wind. Second, there is variability in the solar wind composition over a whole range of time scales. Recent measurements carried out in the earth's magnetosheath during times that included high-speed coronal-hole-associated flows indicate a significantly lower overabundance of low FIP elements. Given the fact that the He/H ratio is remarkably constant in the coronal hole solar wind, this result suggests that both enrichment and variability are reduced in such flows.

Gloeckler, George; Geiss, Johannes

1989-01-01

148

Seasonal water uptake and movement in root systems of Australian phraeatophytic plants of dimorphic root morphology: a stable isotope investigation  

Microsoft Academic Search

A natural abundance hydrogen stable isotope technique was used to study seasonal changes in source water utilization and water movement in the xylem of dimorphic root systems and stem bases of several woody shrubs or trees in mediterranean-type ecosystems of south Western Australia. Samples collected from the native treeBanksia prionotes over 18 months indicated that shallow lateral roots and deeply

Todd E. Dawson; John S Pate

1996-01-01

149

BOREAS TE-5 CO2 Concentration and Stable Isotope Composition  

NASA Technical Reports Server (NTRS)

The BOREAS TE-5 team collected measurements in the NSA and SSA on gas exchange, gas composition, and tree growth. This data set contains measurements of the concentration and stable carbon (C-13/C-12 and oxygen (O-18/O-16) isotope ratios of atmospheric CO2 in air samples collected at different heights within forest canopies. The data were collected to determine the influence of photosynthesis and respiration by the forest ecosystems on the concentration and stable isotope ratio of atmospheric CO2 These measurements were collected at the SSA during each 1994 IFC at OJP, OBS, and OA sites. Measurements were also collected at the NSA during each 1994 IFC at the OJP, T6R5S TE UBS, and T2Q6A TE OA sites. The stable isotope ratios are expressed using standard delta notation and in units of per mil. The isotope ratios are expressed relative to the international standard, PDB, for both carbon and oxygen samples. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry

2000-01-01

150

Tracking ENSO with tropical trees: Progress in stable isotope dendroclimatology  

NASA Astrophysics Data System (ADS)

The terrestrial tropics remain an important gap in the growing proxy network used to characterize past ENSO behavior. Here we describe a strategy for development of proxy estimates of paleo-ENSO, via proxy rainfall estimates derived from stable isotope (?18O) measurements made on tropical trees. The approach applies a new model of oxygen isotopic composition of alpha-cellulose (Roden et al., 2000), a rapid method for cellulose extraction from raw wood (Brendel et al., 2000), and continuous flow isotope ratio mass spectrometry (Brand, 1996) to develop proxy chronological, rainfall and growth rate estimates from tropical trees, even those lacking annual rings. The promise and pitfalls of the approach are illustrated in pilot datasets from the US, Costa Rica, Brazil, and Peru, which show isotopic cycles of 4-6 per mil, and interannual anomalies of up to 8 per mil. Together with the mature ENSO proxies (corals, extratropical tree-rings, varved sediments, and ice cores), replicated and well-dated stable isotope chronologies from tropical trees may eventually improve our understanding of ENSO history over the past several hundred years.

Evans, M. N.; Poussart, P. F.; Saleska, S. R.; Schrag, D. P.

2002-12-01

151

Stable isotope patterns in micronekton from the Mozambique Channel  

NASA Astrophysics Data System (ADS)

We measured the stable carbon (?13C) and nitrogen (?15N) isotopic composition of tissues of micronektonic organisms (fishes, squids, crustaceans and gelatinous organisms) collected in the Mozambique Channel during two scientific cruises in 2008 and 2009. The oceanic circulation in the Mozambique Channel is dominated by mesoscale cyclonic and anticyclonic eddies which play a key role in biological processes of less-productive deep-sea ecosystems. We investigated the potential impact of mesoscale features on the ?13C and ?15N values of 32 taxa of micronekton. Fishes, squids, crustaceans and gelatinous organisms encompassed a wide range of isotopic niches, with large overlaps among species. Our results showed that mesoscale features did not really influence the isotopic signatures of the sampled organisms, although cyclonic eddies can occasionally impact the nitrogen signatures of micronekton. We show that ?13C values were intermediate between standard offshore and nearshore signatures, suggesting that pelagic production in the Mozambique Channel could be partly supported by the transport and export of inorganic and organic particles from the Mozambican coast toward the offshore area. Trophic levels calculated from ?15N values ranged from 2.6 to 4.2, showing that micronekton taxa can be tertiary consumers in the Mozambique Channel. Our findings evidenced clusters of micronektonic organisms according to their ?15N or ?13C isotopic signatures, but variations in stable isotope values reflect a complex set of embedded processes linked to physical mesoscale dynamics (rotational dynamics of eddies) and basic biology and ecology of micronektonic organisms (vertical habitat, migration pattern, dietary habits, body length) that are discussed with regard to the stable isotope method based on time-integrated assimilated food.

Mnard, Frdric; Benivary, Hermann Doris; Bodin, Nathalie; Coffineau, Nathalie; Le Loc'h, Franois; Mison, Thomas; Richard, Pierre; Potier, Michel

2014-02-01

152

Stable isotope-vapour trajectory relationships in Rocky Mountain snowpacks  

NASA Astrophysics Data System (ADS)

To assess the relationships between vapour trajectories and stable water isotopes in the Canadian Rocky Mountains, snow pits were sampled over three accumulation seasons (2004/05, 2005/06 and 2006/07) at two field sites. These sites, the Opabin and Haig Glaciers, are 160km apart at similar elevations and represent windward and lee-slope environments respectively. At both sites, snow pits were sampled at one glacier and one forefield location for delta 18O, deltaD, temperature and density. Intra-seasonal changes in delta18O are examined to determine the extent of post-depositional modification of isotope stratigraphies. At forefield sampling locations, vapour transport within the snowpack caused a significant amount of post-depositional modification of the seasonal delta18 O signal. At glacier sites there was minimal temporal change before the onset of spring melt in all years, and the comparative structure of delta 18O profiles from both glacier sites suggests that regional controls govern the isotopic composition of solid-phase precipitation in the Rocky Mountain region. The seasonal stability of isotope profiles at glacier sites enables individual snowfall events to be identified within isotope stratigraphies. A trajectory classification is produced for all events and the key meteorological, synoptic and isotopic characteristics of each trajectory class are investigated using data from alpine field sites and a suite of meteorological records from the region. An analysis of the relative influences of temperature and air-mass trajectory on snow-isotope ratios reveals some separation in mean delta 18O between storm classes, but the separation appears to be primarily driven by the mean temperature of each class rather than being a direct effect of vapour pathway. To further investigate the effect of storm trajectory on stable isotope ratios in this region, the isotopic evolution of precipitation along storm trajectories from 2006/07 is modelled using a single stage Rayleigh distillation model coupled to a simple orographic model. Isotopic data from alpine snow pits, along with an additional dataset from a sampling transect in southern British Columbia, are used to constrain and test the model. The addition of an orographic component is an improvement over a conventional Rayleigh model, and there is a good model fit to alpine isotope data for most storms.

Sinclair, Kate E.

153

Intrinsic and synthetic stable isotope marking of tsetse flies.  

PubMed

The sterile insect technique has been successfully used to eliminate tsetse populations in a number of programs. Program monitoring in the field relies on the ability to accurately differentiate released sterile insects from wild insects so that estimates can be made of the ratio of sterile males to wild males. Typically, released flies are marked with a dye, which is not always reliable. The difference in isotopic signatures between wild and factory-reared populations could be a reliable and intrinsic secondary marker to complement existing marking methods. Isotopic signatures are natural differences in stable isotope composition of organisms due to discrimination against the heavier isotopes during some biological processes. As the isotopic signature of an organism is mainly dependent on what it eats; by feeding factory-reared flies isotopically different diets to those of the wild population it is possible to intrinsically mark the flies. To test this approach unlabeled samples of Glossina pallidipes (Austen) (Diptera: Glossinidae) from a mass rearing facility and wild populations were analyzed to determine whether there were any natural differences in signatures that could be used as markers. In addition experiments were conducted in which the blood diet was supplemented with isotopically enriched compounds and the persistence of the marker in the offspring determined. There were distinct natural isotopic differences between factory reared and wild tsetse populations that could be reliably used as population markers. It was also possible to rear artificially isotopically labeled flies using simple technology and these flies were clearly distinguishable from wild populations with greater than 95% certainty after 85 days of "release". These techniques could be readily adopted for use in SIT programs as complimentary marking techniques. PMID:21870965

Hood-Nowotny, Rebecca; Watzka, Margarete; Mayr, Leo; Mekonnen, Solomon; Kapitano, Berisha; Parker, Andrew

2011-01-01

154

Stable Isotope Mapping of Alaskan Grasses and Marijuana  

NASA Astrophysics Data System (ADS)

The spatial variation of isotope signatures in organic material is a useful forensic tool, particularly when applied to the task of tracking the production and distribution of plant-derived illicit drugs. In order to identify the likely grow-locations of drugs such as marijuana from unknown locations (i.e., confiscated during trafficking), base isotope maps are needed that include measurements of plants from known grow-locations. This task is logistically challenging in remote, large regions such as Alaska. We are therefore investigating the potential of supplementing our base (marijuana) isotope maps with data derived from other plants from known locations and with greater spatial coverage in Alaska. These currently include >150 samples of modern C3 grasses (Poaceae) as well as marijuana samples (n = 18) from known grow-locations across the state. We conducted oxygen, carbon and nitrogen stable isotope analyses of marijuana and grasses (Poaceae). Poaceae samples were obtained from the University of Alaska Fairbanks (UAF) Museum of the North herbarium collection, originally collected by field botanists from around Alaska. Results indicate that the oxygen isotopic composition of these grasses range from 10 to 30, and broadly mirror the spatial pattern of water isotopes in Alaska. Our marijuana samples were confiscated around the state of Alaska and supplied to us by the UAF Police Department. ?13C, ?15N and ?18O values exhibit geographic patterns similar to the modern grasses, but carbon and nitrogen isotopes of some marijuana plants appear to be influenced by additional factors related to indoor growing conditions (supplementary CO2 sources and the application of organic fertilizer). As well as providing a potential forensic resource, our Poaceae isotope maps could serve additional value by providing resources for studying ecosystem nutrient cycling, for tracing natural ecological processes (i.e., animal migration and food web dynamics) and providing modern data for comparison with isotope analyses conducted on fossil leaf material in paleoecological studies.

Booth, A. L.; Wooller, M. J.

2008-12-01

155

Intrinsic and Synthetic Stable Isotope Marking of Tsetse Flies  

PubMed Central

The sterile insect technique has been successfully used to eliminate tsetse populations in a number of programs. Program monitoring in the field relies on the ability to accurately differentiate released sterile insects from wild insects so that estimates can be made of the ratio of sterile males to wild males. Typically, released flies are marked with a dye, which is not always reliable. The difference in isotopic signatures between wild and factory-reared populations could be a reliable and intrinsic secondary marker to complement existing marking methods. Isotopic signatures are natural differences in stable isotope composition of organisms due to discrimination against the heavier isotopes during some biological processes. As the isotopic signature of an organism is mainly dependent on what it eats; by feeding factory-reared flies isotopically different diets to those of the wild population it is possible to intrinsically mark the flies. To test this approach unlabeled samples of Glossina pallidipes (Austen) (Diptera: Glossinidae) from a mass rearing facility and wild populations were analyzed to determine whether there were any natural differences in signatures that could be used as markers. In addition experiments were conducted in which the blood diet was supplemented with isotopically enriched compounds and the persistence of the marker in the offspring determined. There were distinct natural isotopic differences between factory reared and wild tsetse populations that could be reliably used as population markers. It was also possible to rear artificially isotopically labeled flies using simple technology and these flies were clearly distinguishable from wild populations with greater than 95% certainty after 85 days of release. These techniques could be readily adopted for use in SIT programs as complimentary marking techniques.

Hood-Nowotny, Rebecca; Watzka, Margarete; Mayr, Leo; Mekonnen, Solomon; Kapitano, Berisha; Parker, Andrew

2011-01-01

156

Infrared Spectroscopy and Stable Isotope Geochemistry of Hydrous Silicate Glasses  

SciTech Connect

The focus of this DOE-funded project has been the study of volatile components in magmas and the atmosphere. Over the twenty-one year period of this project, we have used experimental petrology and stable isotope geochemistry to study the behavior and properties of volatile components dissolved in silicate minerals and melts and glasses. More recently, we have also studied the concentration and isotopic composition of CO2 in the atmosphere, especially in relation to air quality issues in the Los Angeles basin.

Stolper, Edward

2007-03-05

157

The use of stable isotope labelling for the analytical chemistry of drugs.  

PubMed

This perspective reviews the potential for stable isotope labelling to examine the metabolic transformations of drugs. The increased sensitivity and widespread availability of modern nuclear magnetic resonance (NMR) and high-resolution mass spectrometers will increase the application of stable isotopes to study drug metabolism. Creating mass doublets by mixing a natural isotopic abundance compound with a labelled isotopomer and applying stable isotope filtering to high resolution mass spectrometry allows one to rapidly identify drug metabolites in very complex samples, such as blood or urine. Applying this approach to drug metabolism will require a significant synthesis effort. The relatively small number of (13) C, (15) N, or (17,18) O-labelled precursors exacerbates this problem, making the synthesis of the labelled drug often more difficult than that of the parent compound. We have developed new strategies for stable isotope labelling of complex molecules based on the rich chemistry of [(13) C]methyl phenyl sulfide, where the phenylthio group acts as a stable, non-volatile carrier for the valuable (13) C-label. For example we have used [(13) C]methyl phenyl sulfide to prepare the three possible (13) C-isotopomers ([1-(13) C]-, [2-(13) C]-, [1,2-(13) C(2) ]) of the two carbon precursors, ethyl 2-(phenylthio) acetate and ethyl N,N-dimethyl oxamate. In each case, these two-carbon labelling precursors are asymmetric and the differential reactivity of the carbons allows for either/or (13) C-labelling in the products. We demonstrate the utility of these two carbon precursors in the synthesis of aromatic ring-labelled N-(4-hydroxyphenyl)acetamide (acetaminophen or paracetamol). PMID:22170639

Unkefer, Clifford J; Martinez, Rodolfo A

2012-01-01

158

Stable carbon and nitrogen isotope analysis of avian uric acid.  

PubMed

We report results obtained using a new technique developed to measure the stable-isotope composition of uric acid isolated from bird excreta (guano). Results from a diet-switch feeding trial using zebra finches suggest that the delta(13)C of uric acid in the guano equilibrates with the diet of the bird within 3 days of a change in diet, while the equilibration time for delta(15)N may be longer. The average carbon isotope discrimination between uric acid and food before the diet switch was +0.34 +/- 1 per thousand (1sigma) while after the diet switch this increased slightly to +0.83 +/- 0.7 per thousand (1sigma). Nitrogen isotope discrimination was +1.3 +/- 0.3 per thousand (1sigma) and +0.3 +/- 0.3 per thousand (1sigma) before and after the diet switch; however, it is possible that the nitrogen isotope values did not fully equilibrate with diet switch over the course of the experiment. Analyses of other chemical fractions of the guano (organic residue after uric acid extraction and non-uric acid organics solubilised during extraction) suggest a total range of up to 3 per thousand for both delta(13)C and delta(15)N values in individual components of a single bulk guano sample. The analysis of natural samples from a range of terrestrial and marine species demonstrates that the technique yields isotopic compositions consistent with the known diets of the birds. The results from natural samples further demonstrate that multiple samples from the same species collected from the same location yield similar results, while different species from the same location exhibit a range of isotopic compositions indicative of different dietary preferences. Given that many samples of guano can be rapidly collected without any requirement to capture specimens for invasive sampling, the stable-isotope analysis of uric acid offers a new, simple and potentially powerful tool for studying avian ecology and metabolism. PMID:18837063

Bird, Michael I; Tait, Elaine; Wurster, Christopher M; Furness, Robert W

2008-11-01

159

Investigating microbial carbon cycling using natural abundance isotope analysis of PLFA  

NASA Astrophysics Data System (ADS)

Understanding microbial carbon sources and cycling is fundamental to our conceptualization of microbial ecosystems and their role in biogeochemical cycling in natural systems. Achieving this understanding requires application of a wide range of approaches. Natural abundance isotope analysis of individual compounds, particularly cellular components such as Phospholipids Fatty Acids (PLFA) can provide insights into the carbon sources and metabolic activities of the in situ microbial community from environmental samples. This is primarily because specific PLFA can be well resolved by gas chromatography even from complex matrices where confounding biological/organic compound abound. These PLFA can then be attributed to the viable microbial community, in some cases to specific components of this community and due to characteristic biosynthetic fractionations of stable isotope ratios, ?13C analysis of PLFA can: differentiate isotopically distinct primary carbon sources of heterotrophic communities; identify isotopic patterns characteristic of autotrophic versus heterotrophic processes; and elucidate microbial biosynthetic pathways. In cases where there ?13C cannot provide resolution of carbon sources, new approaches in ?14C of PLFA can be applied. The vast range in ?14C of ancient and modern carbon provides an easily traceable signal that can differentiate uptake and utilization of these carbon sources. This is particularly useful in cases such as contaminated sites where petroleum based contamination has occurred, or in natural systems where microbial communities may be utilizing geologic versus recently photosynthetically fixed carbon. This talk will present several examples demonstrating the utility of this approach.

Slater, G. G.; Brady, A.; Cowie, B.

2008-12-01

160

Method for determination of stable carbon isotope ratio of methylnitrophenols in atmospheric particulate matter  

NASA Astrophysics Data System (ADS)

A technique for the measurement of the stable isotope ratio of methylnitrophenols in atmospheric particulate matter is presented. Atmospheric samples from rural and suburban areas were collected for evaluation of the procedure. Particulate matter was collected on quartz fibre filters using dichotomous high volume air samplers. Methylnitrophenols were extracted from the filters using acetonitrile. The sample was then purified using a combination of high-performance liquid chromatography and solid phase extraction. The final solution was then divided into two aliquots. To one aliquot, a derivatising agent, Bis(trimethylsilyl)trifluoroacetamide, was added for Gas Chromatography-Mass Spectrometry analysis. The second half of the sample was stored in a refrigerator. For samples with concentrations exceeding 1 ng ?l-1, the second half of the sample was used for measurement of stable carbon isotope ratios by Gas Chromatography-Isotope Ratio Mass Spectrometry. The procedure described in this paper provides a method for the analysis of methylnitrophenols in atmospheric particulate matter at concentrations as low as 0.3 pg m-3 and for stable isotope ratios with an accuracy of better than 0.5 for concentrations exceeding 100 pg m-3. In all atmospheric particulate matter samples analysed, 2-methyl-4-nitrophenol was found to be the most abundant methylnitrophenol, with concentrations ranging from the low pg m-3 range in rural areas to more than 200 pg m-3 in some samples from a suburban location.

Moukhtar, S.; Saccon, M.; Kornilova, A.; Irei, S.; Huang, L.; Rudolph, J.

2011-11-01

161

Stable Isotope Analyses of water and Aqueous Solutions by Conventional Dual-inlet Mass Spectrometry  

SciTech Connect

The foundation of various analytical methods for the stable isotope composition of water and other aqueous samples (natural abundance, {sup 1}H : {sup 2}H (D) = 99.985 : 0.015 atom%, and {sup 16}O : {sup 17}O : {sup 18}O = 99.762 : 0.038 : 0.200 atom%) was established during the Manhatten Project in the U.S.A., when large amounts of heavy water were produced for nuclear reactors (see Kirshenbaum, 1951, for a detailed account). From early on, there was great interest in the oxygen and hydrogen isotopic compositions of water, because they are the ideal tracers of water sources and reactions. The increased analytical precisions made possible by the subsequent development of modern gas-source isotope-ratio mass spectrometers with dual-inlets and multi-collectors, have caused the proliferation of new analytical methods and applications for the oxygen and hydrogen isotopic compositions of water. These stable isotopes have found wide applications in basic as well as applied sciences (chemistry, geology, hydrology, biology, medical sciences, and food sciences). This is because water is ubiquitous, is an essential and predominant ingredient of living organisms, and is perhaps the most reactive compound in the Earth.

Horita, Juske [ORNL; Kendall, C. [U.S. Geological Survey, Menlo Park, CA

2004-01-01

162

Stable isotope dilution analyses of molybdenum in meteorites.  

PubMed

Isotope dilution mass spectrometry is an ideal analytical technique to measure the elemental abundance of Mo in C1 carbonaceous chondrites and the metallic and troilite phases of iron meteorites. The mean abundance of Mo in two C1 meteorites is 0.909+/-0.040 microg/g which corresponds to a value of 2.55 atoms Mo with respect to Si equal to 10(6) atoms, which is identical to the currently accepted solar system abundance. The partitioning of Mo between the metallic and sulfide phases in the Mundrabilla iron meteorite was found to be 6.0+/-0.2 microg/g and 8.6+/-0.3 microg/g, respectively. A new, precise Mo concentration of 1.54+/-0.04 microg/g for the Geochemical Reference Standard BCR-1 is also reported. PMID:11220597

Wieser, M E; De Laeter, J R

2000-01-01

163

Stable Isotopes of Ice: the Legacy of Willi Dansgaard  

NASA Astrophysics Data System (ADS)

Stable isotope ratios of ice, D/H and 18O/16O are one of the key climate indicators measured in ice cores. These isotope ratios vary with temperature, a relationship based on physical principles backed up by many observations. The combination of these isotope ratios, expressed as the difference between the delta values with ?18O scaled by a factor of eight, is called the deuterium excess (d=?D-8*?18O). This parameter varies primarily as a function of the conditions of evaporation of the parent moisture for snow, yielding a signal of ocean conditions measured in the ice. In his classic 1964 paper in Tellus, Willi Dansgaard laid out the theoretical and observational basis for using stable isotope ratios in ice cores as paleo-environmental tools. This paper, cited over 2,200 times, and written nearly 50 years ago, is one of the key foundational papers in paleoclimatology, and remains a must read for any student of stable isotope geochemistry. In this talk we will explore Dansgaard's legacy of ice core climatology, with a focus on his pioneering work in using the full temporal resolution of ice cores in Greenland to explore climate change on time scales of years to decades. While Dansgaard began his career applying a clever technique to a novel medium with the goal of simply trying to understand how our planet functions, he early on understood the power of ice cores to inform us about human impacts on the climate system, as well as the power of ice cores to tell us about natural climate variability on time scales of human interest and impact. Dansgaard's body of work is one of the solid pillars on which modern paleoclimatology stands, and continues to inform us today about modern anthropogenic climate change.

White, J. W. C.; Johnson, S. J.

2012-04-01

164

Atomic Masses of the Stable Isotopes, 10<=A<=30  

Microsoft Academic Search

The masses of all stable isotopes in the range 10<=A<=30 have been measured using the large double-focusing mass spectrometer recently constructed at this laboratory. No serious discrepancies are found between the present results and other mass spectroscopic measurements except at Ne20. The masses calculated from nuclear reaction energies are, with the exception of F19, lower than the present results. The

T. T. Scolman; K. S. Quisenberry; A. O. Nier

1956-01-01

165

Continental-Scale Distributions of Vegetation Stable Carbon Isotope Ratios  

Microsoft Academic Search

\\u000a The stable carbon isotope composition (?13C) of terrestrial vegetation is important for a variety of applications in fields ranging from biogeochemistry to zoology\\u000a to paleoclimatology. To a large degree, spatial patterns in plant ?13C are imparted by variations in the photosynthetic pathway (C3\\/C4) composition of vegetation in topical and subtropical regions. Thus, the fractional coverage of each vegetation type must

Christopher J. Still; Rebecca L. Powell

166

A NEW CALCULATION FOR THE AGE OF THE EARTH FROM ABUNDANCES OF LEAD ISOTOPES  

Microsoft Academic Search

A new method, basically distinct from the two most common methods, is ; suggested for calculating the age of the Earth from lead isotope abundances. In ; common with other methods, the new method assumes that the samples used in the ; calculation can be interpreted by equations appropriate to evolution of the lead ; isotope abundances in a single

R. G. Ostic; R. D. Russell; P. H. Reynolds

1963-01-01

167

Paleoclimate and Amerindians: evidence from stable isotopes and atmospheric circulation.  

PubMed

Two Amerindian demographic shifts are attributed to climate change in the northwest plains of North America: at approximately 11,000 calendar years before present (yr BP), Amerindian culture apparently split into foothills-mountains vs. plains biomes; and from 8,000-5,000 yr BP, scarce archaeological sites on the open plains suggest emigration during xeric "Altithermal" conditions. We reconstructed paleoclimates from stable isotopes in prehistoric bison bone and relations between weather and fractions of C(4) plants in forage. Further, we developed a climate-change model that synthesized stable isotope, existing qualitative evidence (e.g., palynological, erosional), and global climate mechanisms affecting this midlatitude region. Our isotope data indicate significant warming from approximately 12,400 to 11,900 yr BP, supporting climate-driven cultural separation. However, isotope evidence of apparently wet, warm conditions at 7,300 yr BP refutes emigration to avoid xeric conditions. Scarcity of archaeological sites is best explained by rapid climate fluctuations after catastrophic draining of the Laurentide Lakes, which disrupted North Atlantic Deep Water production and subsequently altered monsoonal inputs to the open plains. PMID:11226265

Lovvorn, M B; Frison, G C; Tieszen, L L

2001-02-27

168

Paleoclimate and Amerindians: Evidence from stable isotopes and atmospheric circulation  

USGS Publications Warehouse

Two Amerindian demographic shifts are attributed to climate change in the northwest plains of North America: at ???11,000 calendar years before present (yr BP), Amerindian culture apparently split into foothills-mountains vs. plains biomes; and from 8,000-5,000 yr BP, scarce archaeological sites on the open plains suggest emigration during xeric "Altithermal" conditions. We reconstructed paleoclimates from stable isotopes in prehistoric bison bone and relations between weather and fractions of C4 plants in forage. Further, we developed a climate-change model that synthesized stable isotope, existing qualitative evidence (e.g., palynological, erosional), and global climate mechanisms affecting this midlatitude region. Our isotope data indicate significant warming from ???12,400 to 11,900 yr BP, supporting climate-driven cultural separation. However, isotope evidence of apparently wet, warm conditions at 7,300 yr BP refutes emigration to avoid xeric conditions. Scarcity of archaeological sites is best explained by rapid climate fluctuations after catastrophic draining of the Laurentide Lakes, which disrupted North Atlantic Deep Water production and subsequently altered monsoonal inputs to the open plains.

Lovvorn, M. B.; Frison, G. C.; Tieszen, L. L.

2001-01-01

169

Modelling of stable isotope fractionation by methane oxidation and diffusion in landfill cover soils  

SciTech Connect

A technique to measure biological methane oxidation in landfill cover soils that is gaining increased interest is the measurement of stable isotope fractionation in the methane. Usually to quantify methane oxidation, only fractionation by oxidation is taken into account. Recently it was shown that neglecting the isotope fractionation by diffusion results in underestimation of the methane oxidation. In this study a simulation model was developed that describes gas transport and methane oxidation in landfill cover soils. The model distinguishes between {sup 12}CH{sub 4}, {sup 13}CH{sub 4}, and {sup 12}CH{sub 3}D explicitly, and includes isotope fractionation by diffusion and oxidation. To evaluate the model, the simulations were compared with column experiments from previous studies. The predicted concentration profiles and isotopic profiles match the measured ones very well, with a root mean square deviation (RMSD) of 1.7 vol% in the concentration and a RMSD of 0.8 per mille in the {delta}{sup 13}C value, with {delta}{sup 13}C the relative {sup 13}C abundance as compared to an international standard. Overall, the comparison shows that a model-based isotope approach for the determination of methane oxidation efficiencies is feasible and superior to existing isotope methods.

Mahieu, Koenraad [Laboratory of Applied Physical Chemistry (ISOFYS), Ghent University, Coupure links 653, B-9000 Ghent (Belgium); Department of Applied Mathematics, Biometrics and Process Control (BIOMATH), Ghent University, Coupure links 653, B-9000 Ghent (Belgium)], E-mail: Koenraad.mahieu@lid.kviv.be; De Visscher, Alex [Department of Chemical and Petroleum Engineering, Schulich School of Engineering, University of Calgary, 2500 University Drive N.W., Calgary, Alberta, T2N 1N4 (Canada); Vanrolleghem, Peter A. [Department of Applied Mathematics, Biometrics and Process Control (BIOMATH), Ghent University, Coupure links 653, B-9000 Ghent (Belgium); Department of Civil Engineering (modelEAU), Universite Laval, Pavillon Pouliot, Quebec, G1K 7P4 (Canada); Van Cleemput, Oswald [Laboratory of Applied Physical Chemistry (ISOFYS), Ghent University, Coupure links 653, B-9000 Ghent (Belgium)

2008-07-01

170

Modelling of stable isotope fractionation by methane oxidation and diffusion in landfill cover soils.  

PubMed

A technique to measure biological methane oxidation in landfill cover soils that is gaining increased interest is the measurement of stable isotope fractionation in the methane. Usually to quantify methane oxidation, only fractionation by oxidation is taken into account. Recently it was shown that neglecting the isotope fractionation by diffusion results in underestimation of the methane oxidation. In this study a simulation model was developed that describes gas transport and methane oxidation in landfill cover soils. The model distinguishes between 12CH4, 13CH4, and 12CH3D explicitly, and includes isotope fractionation by diffusion and oxidation. To evaluate the model, the simulations were compared with column experiments from previous studies. The predicted concentration profiles and isotopic profiles match the measured ones very well, with a root mean square deviation (RMSD) of 1.7 vol% in the concentration and a RMSD of 0.8 per thousand in the delta13C value, with delta13C the relative 13C abundance as compared to an international standard. Overall, the comparison shows that a model-based isotope approach for the determination of methane oxidation efficiencies is feasible and superior to existing isotope methods. PMID:17825548

Mahieu, Koenraad; De Visscher, Alex; Vanrolleghem, Peter A; Van Cleemput, Oswald

2008-01-01

171

Nitrogen stable isotopes in primary uptake compartments across streams differing in nutrient availability.  

PubMed

High variability in the natural abundance of nitrogen stable isotopes (?(15)N) has been reported for primary uptake compartments (PUCs; e.g., epilithon, filamentous algae, bryophytes, macrophytes) in human-impacted aquatic ecosystems, but the origin of this variability is not yet well understood. We examined how ?(15)N of different PUC types relate to ?(15)N of dissolved inorganic nitrogen (DIN) species (nitrate and ammonium) and to the stream nutrient concentrations in which they grow. We selected 25 reaches located across the fluvial network of La Tordera catchment (NE Spain, 868.5 km(2)), encompassing a gradient of human pressures from headwaters to the river valley. ?(15)N-PUC variability was mostly explained by location within the fluvial network and was strongly related to the ?(15)N of DIN species, especially of ammonium. Models were stronger for PUCs growing within the stream channel and thus using streamwater as their main source of nutrients. Regression models including nutrient concentrations improved the prediction power for ?(15)N-PUCs, suggesting that nutrient concentrations and stoichiometry cannot be ignored in explaining the natural abundance of nitrogen isotopes in PUCs. These results provide insights into what controls variability in ?(15)N of PUCs within a stream network, with implications for the application of stables isotopes as an ecological tool. PMID:23930789

Pastor, Ada; Peipoch, Marc; Caas, Ldia; Chappuis, Eglantine; Ribot, Miquel; Gacia, Esperana; Riera, Joan Llus; Mart, Eugnia; Sabater, Francesc

2013-09-17

172

Realistic Fasting Does Not Affect Stable Isotope Levels of a Metabolically Efficient Salamander  

EPA Science Inventory

Stable isotopes are commonly used to examine various aspects of animal ecology. The use of stable isotopes generally proceeds under the implicit assumption that resource use is the only factor driving variation in stable isotope levels; however, a wealth of studies demonstrate a...

173

Enantioselective stable isotope analysis (ESIA) of polar Herbicides  

NASA Astrophysics Data System (ADS)

The complexity of aquatic systems makes it challenging to assess the environmental fate of chiral micropolutants. As an example, chiral herbicides are frequently detected in the environment (Buser and Muller, 1998); however, hydrological data is needed to determine their degradability from concentration measurements. Otherwise declining concentrations cannot unequivocally be attributed to degradation, but could also be caused by dilution effects. In contrast, isotope ratios or enantiomeric ratios are elegant alternatives that are independent of dilution and can even deliver insights into reaction mechanisms. To combine the advantages of both approaches we developed an enatioselective stable isotope analysis (ESIA) method to investigate the fate of the chiral herbicides 4-CPP ((RS)-2-(4-chlorophenoxy)-propionic acid), mecoprop (2-(4-Chloro-2-methylphenoxy)-propionic acid) and dichlorprop (2-(2,4-Dichlorophenoxy)-propionic acid). After testing the applicable concentration range of the method, enantioselective isotope fractionation was investigated by microbial degradation using dichlorprop as a model compound. The method uses enantioselective gas-chromatography (GC) to separate enantiomers. Subsequently samples are combusted online to CO2 and carbon isotope ratios are determined for each enantiomer by isotope-ratio-mass-spectrometry (IRMS). Because the analytes contain a polar carboxyl-group, samples were derivatised prior to GC-IRMS analysis with methanolic BF3 solution. Precise carbon isotope analysis (2? ?0.5) was achieved with a high sensitivity of ? 7 ng C that is needed on column for one analysis. Microbial degradation of the model compound dichlorprop was conducted with Delftia acidovorans MC1 and pronounced enantiomer fractionation, but no isotope fractionation was detected. The absence of isotope fractionation can be explained by two scenarios: either the degrading enzyme has no isotopic preference, or another step in the reaction without an isotopic preference was rate determining. Our findings are in contrast to previously reported results for the degradation of ?-hexachlorocyclohexane (Badea et al., 2012), where isotope fractionation, but no enantiomeric fractionation was observed. Hence the two lines of evidence seem to be independent of each other. Enhanced insight maybe provided when both effects appear simultaneously, as shown downstream of a landfill site under anaerobic conditions for the chiral herbicide 4-CPP (Milosevic et al., 2013). Buser HR, Muller MD (1998): Occurrence and transformation reactions of chiral and achiral phenoxyalkanoic acid herbicides in lakes and rivers in Switzerland. Environmental Science & Technology 32 (5):626-633. Badea S-L, Vogt C, Gehre M, Fischer A, Danet A-F, Richnow H-H (2011): Development of an enantiomer-specific stable carbon isotope analysis (ESIA) method for assessing the fate of alpha-hexachlorocyclohexane in the environment. Rapid Communications in Mass Spectrometry 25 (10):1363-1372. Milosevic N, Qiu S, Elsner M, Einsiedl F, Maier MP, Bensch HKV, Albrechtsen HJ, Bjerg PL (2013): Combined isotope and enantiomer analysis to assess the fate of phenoxy acids in a eterogeneous geologic setting at an old landfill. Water Research 47 (2): 637-649.

Maier, Michael; Qiu, Shiran; Elsner, Martin

2013-04-01

174

Stable isotope-resolved metabolomics and applications for drug development  

PubMed Central

Advances in analytical methodologies, principally nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS), during the last decade have made large-scale analysis of the human metabolome a reality. This is leading to the reawakening of the importance of metabolism in human diseases, particularly cancer. The metabolome is the functional readout of the genome, functional genome, and proteome; it is also an integral partner in molecular regulations for homeostasis. The interrogation of the metabolome, or metabolomics, is now being applied to numerous diseases, largely by metabolite profiling for biomarker discovery, but also in pharmacology and therapeutics. Recent advances in stable isotope tracer-based metabolomic approaches enable unambiguous tracking of individual atoms through compartmentalized metabolic networks directly in human subjects, which promises to decipher the complexity of the human metabolome at an unprecedented pace. This knowledge will revolutionize our understanding of complex human diseases, clinical diagnostics, as well as individualized therapeutics and drug response. In this review, we focus on the use of stable isotope tracers with metabolomics technologies for understanding metabolic network dynamics in both model systems and in clinical applications. Atom-resolved isotope tracing via the two major analytical platforms, NMR and MS, has the power to determine novel metabolic reprogramming in diseases, discover new drug targets, and facilitates ADME studies. We also illustrate new metabolic tracer-based imaging technologies, which enable direct visualization of metabolic processes in vivo. We further outline current practices and future requirements for biochemoinformatics development, which is an integral part of translating stable isotope-resolved metabolomics into clinical reality.

Fan, Teresa W-M.; Lorkiewicz, Pawel; Sellers, Katherine; Moseley, Hunter N.B.; Higashi, Richard M.; Lane, Andrew N.

2012-01-01

175

Stable Isotope Ratios in Hair and Teeth Reflect Biologic Rhythms  

PubMed Central

Biologic rhythms give insight into normal physiology and disease. They can be used as biomarkers for neuronal degenerations. We present a diverse data set to show that hair and teeth contain an extended record of biologic rhythms, and that analysis of these tissues could yield signals of neurodegenerations. We examined hair from mummified humans from South America, extinct mammals and modern animals and people, both healthy and diseased, and teeth of hominins. We also monitored heart-rate variability, a measure of a biologic rhythm, in some living subjects and analyzed it using power spectra. The samples were examined to determine variations in stable isotope ratios along the length of the hair and across growth-lines of the enamel in teeth. We found recurring circa-annual periods of slow and fast rhythms in hydrogen isotope ratios in hair and carbon and oxygen isotope ratios in teeth. The power spectra contained slow and fast frequency power, matching, in terms of normalized frequency, the spectra of heart rate variability found in our living subjects. Analysis of the power spectra of hydrogen isotope ratios in hair from a patient with neurodegeneration revealed the same spectral features seen in the patient's heart-rate variability. Our study shows that spectral analysis of stable isotope ratios in readily available tissues such as hair could become a powerful diagnostic tool when effective treatments and neuroprotective drugs for neurodegenerative diseases become available. It also suggests that similar analyses of archaeological specimens could give insight into the physiology of ancient people and animals.

Appenzeller, Otto; Qualls, Clifford; Barbic, Franca; Furlan, Raffaello; Porta, Alberto

2007-01-01

176

Guidelines and recommended terms for expression of stable-isotope-ratio and gas-ratio measurement results  

USGS Publications Warehouse

To minimize confusion in the expression of measurement results of stable isotope and gas-ratio measurements, recommendations based on publications of the Commission on Isotopic Abundances and Atomic Weights of the International Union of Pure and Applied Chemistry (IUPAC) are presented. Whenever feasible, entries are consistent with the Systme International d'Units, the SI (known in English as the International System of Units), and the third edition of the International Vocabulary of Basic and General Terms in Metrology (VIM, 3rd edition). The recommendations presented herein are approved by the Commission on Isotopic Abundances and Atomic Weights and are designed to clarify expression of quantities related to measurement of isotope and gas ratios to ensure that quantity equations instead of numerical value equations are used for quantity definitions. Examples of column headings consistent with quantity calculus (also called the algebra of quantities) and examples of various deprecated usages connected with the terms recommended are presented.

Coplen, Tyler B.

2011-01-01

177

Carbon allocation in plants and ecosystems - insights from stable isotope studies  

NASA Astrophysics Data System (ADS)

Trees are large global stores of carbon (C) that will be impacted by increased carbon dioxide levels and climate change. However, at present we cannot properly predict the carbon balance of forests in future as we lack knowledge on how plant physiological processes, the transfer of carbon within the plant, carbon storage, and remobilization in the plant tissues as well as the release of carbon from the roots to the soil interact with environmental drivers and ecosystem-scale processes. This paper will summarise how stable isotope techniques can give new insights in the fate of newly assimilated C in plants and ecosystems on time scales from hours to seasons and it will include studies either characterizing temporal and spatial variation in the natural abundance of carbon and oxygen isotopes or applying isotopically enriched tracers. It comprises the assessment of the mechanisms of C partitioning among specific metabolic pathways, between plant organs and into various ecosystem C pools with different residence times. Moreover stable isotopes are highly suitable tools to characterise the role of the phloem, which is the central long-distance conveyer distributing C from source to sinks and thus plays a central role in linking sites and structures of storage, growth and other metabolic activities. A deeper understanding of these processes and their interaction with environmental drivers is critical for predicting how trees and ecosystems will respond to coming global environmental changes, including increased temperature, altered precipitation, and elevated carbon dioxide concentrations.

Gessler, Arthur

2014-05-01

178

Controls on stable strontium isotope fractionation in coccolithophores with implications for the marine Sr cycle  

NASA Astrophysics Data System (ADS)

The controls on stable Sr isotope fractionation into the calcite produced by the coccolithophore species Emiliania huxleyi, Coccolithus pelagicus spp. braarudii and Gephyrocapsa oceanica are investigated. Each species has been cultured under controlled laboratory conditions at a range of temperatures (10-25 C) to test the potential of ?88/86Sr as a proxy for growth rate and/or sea surface temperature. Coccolithophores are one of the most abundant pelagic calcifiers; since Sr substitutes to some degree for Ca in their calcite coccoliths, coccolithophores represent a significant output of Sr from seawater, potentially influencing the ?88/86Sr mass balance in the modern oceans. The coccoliths are investigated for their ?88/86Sr, Sr/Ca, and ?18O measured as function of temperature. As temperature is increased all species show a negative stable Sr isotopic fractionation, related to a temperature controlled growth rate. We infer the shift of ?88/86Sr to lighter values as indicative of a kinetic control on the isotope fractionation, revealing the potential of ?88/86Sr as a proxy for growth rate, which in these experiments is primarily dictated by temperature. The results from these experiments indicate that coccolithophore calcite incorporates Sr with a very light ?88/86Sr isotope composition as low as 0.

Stevenson, Emily I.; Hermoso, Michal; Rickaby, Rosalind E. M.; Tyler, Jonathan J.; Minoletti, Fabrice; Parkinson, Ian J.; Mokadem, Fatima; Burton, Kevin W.

2014-03-01

179

Stable isotope analysis using tunable diode laser spectroscopy  

NASA Technical Reports Server (NTRS)

Ratios of C-12/C-13 in CO2 have been measured using a tunable diode laser (TDL) spectrometer to an accuracy of better than 0.4 percent. These results were made possible by the use of state-of-the-art high-temperature TDLs, an etalon and wavenumber calibration technique, high-speed assembly language controlled data acquisition, and the ratioing of absorbances from simultaneously acquired sample and reference data scans. The dual beam spectrometer that is employed uses the sweep integration technique in a spectral region where adjacent spectral lines are of approximately equal absorbance at the expected isotopic abundances.

Becker, Joseph F.; Sauke, Todd B.; Loewenstein, Max

1992-01-01

180

Pulsed stable isotope-resolved metabolomic studies of cancer cells.  

PubMed

Metabolic reprogramming is a key step in oncogenic transformation, and it involves alterations in both bioenergetic and anabolic metabolism. Sustained by these metabolic alterations, malignant cells acquire the ability to re-enter the cell cycle and proliferate. The so-called central carbon metabolism (CCM) is the ultimate source for energy and building blocks enabling cellular growth and proliferation. The time-resolved monitoring of the conversion of stable isotope-labeled metabolites provides profound insights into the metabolic dynamics of malignant cells and enables the tracking of individual carbon routes within the CCM. Specifically, the analysis of isotope incorporation rates within short time frames by means of pulsed stable isotope-resolved metabolomics (pSIRM) can be used to determine the dynamics of glycolysis and glutaminolysis-two metabolic circuitries that are often deregulated in malignant cells. Here, we detail a pSIRM-based method that can be applied to the study of metabolic alteration in cultured cancer cells. PMID:24924133

Pietzke, Matthias; Kempa, Stefan

2014-01-01

181

Stable lead isotopes evidence anthropogenic contamination in Alaskan sea otters  

SciTech Connect

Lead concentrations and stable isotopic compositions were measured in teeth of preindustrial and contemporary sea otters (Enhydra lutris) from Amchitka Island, AK, to determine if changes had occurred in the magnitude and source of assimilated lead. Although there was no significant difference in lead concentrations between the two groups of otters ({bar x} {plus minus} {sigma}Pb/Ca atomic = 3.6 {plus minus} 2.9 {times} 10{sup {minus}8}), differences in stable lead isotopic compositions revealed a pronounced change in the source of accumulated lead. Lead {bar x} {plus minus} 2{sigma}{sub {bar x}} in the preindustrial otters ({sup 207}Pb/{sup 206}Pb = 0.828 {plus minus} 0.006) was derived from natural deposits in the Aleutian arc, while lead in the contemporary animals ({sup 207}Pb/{sup 206}Pb = 0.856 {plus minus} 0.003) was primarily industrial lead from Asia and western Canada. The isotopic ratios demonstrate anthropogenic perturbations of the lead cycle in present-day coastal food webs and indicate that lead concentration measurements alone are inadequate in assessing the introduction and transport of contaminant lead in the environment.

Smith, D.R.; Estes, J.A.; Flegal, A.R. (Univ. of California, Santa Cruz (USA)); Niemeyer, S. (Lawrence Livermore National Laboratory, CA (USA))

1990-10-01

182

Experimental chlorine stable isotope fractionation of perchlorate respiring bacteria  

NASA Astrophysics Data System (ADS)

Perchlorate natural occurrences on earth are very limited and seem restricted to extremely arid environments such as nitrate deposits of the Atacama Desert of northern Chile, where perchlorate contents can reach 0.1 to 1%. Anthropogenically sourced perchlorate however is extensively used as a major component of explosives and rocket fuels. Careless disposal of these highly soluble and very stable perchlorates locally led to the contamination of drinking water, now recognised as posing a significant health threat. Recent studies have demonstrated that some microorganisms are able to completely reduce perchlorate to innocuous chloride, and offer a great potential for the bioremediation of contaminated waters. Provided that the isotopic fractionation associated with this reduction is significant, the measurement of the chloride isotopic composition of contaminated water is a powerful tool for monitoring the progress of in-situ remediation. We report here, the characterisation of the isotopic fractionation associated with perchlorate reduction performed by Dechlorosoma suillum strain PS during 3 culture experiments performed in a batch fermentor (anoxic, 37C, pH =7). The basal medium contained acetate as the electron donor and perchlorate as the electron acceptor. When possible, chloride salts were replaced by sulphate salts so as to lower the initial chloride content. The paired chlorine isotopic compositions of chloride and perchlorate in solutions sampled throughout the experiment were measured using the method described in Ader et al. 2001. The fractionation between chloride and perchlorate was calculated independently for each sample, using on the one hand the chloride content and isotopic composition and on the other hand the perchlorate content and isotopic composition. The results show that the fractionation is constant within error throughout the experiment for the 3 experiments with a weighted mean of -14.940.14. This value is much lower than the theoretical value expected for an isotopic equilibrium between perchlorate and chloride (-65.8 or -71.3; Schauble et al., 2003). Making the assumption that the microbial fractionation reflects that of the rate-limiting reaction step (probably the first electron transfer), and that the theoretical isotopic fractionation for this electron transfer to perchlorate can be deduced from the general relation between the fractionation between perchlorate and the other species depending on their oxidation state, we suggest that the first step of the microbial perchlorate reduction might occur at isotopic equilibrium in the investigated conditions. Ader et al., 2001, Anal. Chem. 73, 4946-4950. Schauble et al., 2003 G.C.A., 67, 3267-3281.

Ader, M.; Coleman, M.; Coates, J.; Chaudhuri, S.

2006-12-01

183

Stable isotope values of North Atlantic water masses  

NASA Astrophysics Data System (ADS)

A comprehensive study of seawater stable isotope properties in the mid-latitude North Atlantic is still missing, especially for the intermediate and deep-water masses. To fill this gap seawater samples were collected since 2006 along various transects in the Northeast Atlantic. During the Atlantic Meridional Transect (AMT) 18 expedition the upper 300 m were sampled between 46.6 and 24.7N. RV Poseidon cruises POS334, POS349, POS377, and POS383 to the Azores Front region (38.3-30N; 22-20W) generally yielded samples down to 2000 m. High-resolution sampling over the whole water column was performed during the OVIDE 2010 (Portugal to Reykjanes ridge) and KN199-4 cruises. Cruise KN199-4 implemented the section from Lisbon to the Cape Verde Islands of the US GEOTRACES North Atlantic transect. Additional stations collected samples along the Iberian margin during the EUROFLEETS Iberia-Forams cruise on RV Garcia del Cid in September 2012. The isotope results clearly indicate the different water masses and hydrographic fronts, although variability in some regions is higher than expected, potentially an affect of the different years and seasons sampled and/ or meandering of the Azores Current. Higher isotope values are observed in the surface waters of the central subtropical gyre and on the southern side of the Azores Front, i.e. within the Azores Current. Lower isotope values are observed in the North Atlantic Deep Water and the Antarctic Intermediate Water upwelled off NW Africa. Mediterranean Outflow Water is best depicted in the Deuterium values because the salinity signal is less rapidly diluted than temperature. Combining the isotope with the respective station's CTD data will allow establishing regional relationships between isotope and temperature/ salinity.

Voelker, Antje

2013-04-01

184

Distribution and fractionation of Zn stable isotopes in the oceans  

NASA Astrophysics Data System (ADS)

We have measured stable Zn isotope ratios in anthropogenic samples, natural and cultured marine phytoplankton, hydrothermal vent fluids and chimney minerals, and seawater. This comprehensive dataset allows us to explore the sources and sinks of Zn isotopes in the oceans, and the marine processes that fractionate Zn isotopes. By understanding of the forces that control Zn isotope distribution in the oceans, Zn isotopes may serve as tracers of many important biogeochemical processes. All measurements were made on an IsoProbe multi-collector ICP-MS and are reported relative to Lyons-JMC Zn. Zn is an important nutrient for marine phytoplankton, biological uptake and regeneration are largely responsible for the concentration distribution of Zn in the oceans. Both natural and anthropogenic Zn dust are important sources of Zn to the surface ocean. Our measurements show that anthropogenic Zn, with the exception of highly purified and highly fractionated laboratory standards, is isotopically indistinguishable from natural continental materials with ?66Zn ratios between 0.09 and 0.28. The other large source of Zn to the surface oceans is upwelling of deeper waters with a heavier Zn isotope signature. Deep seawater (>300m) samples from the North Pacific were measured and found to have isotope ratios between 0.45 and 0.55. Natural plankton samples appear to reflect the source of Zn to the surface ocean. Plankton samples from areas with large natural and anthropogenic dust Zn sources look isotopically similar to anthropogenic and continental materials. Plankton tows from remote regions of the oceans have Zn isotope ratios more similar to that of deep Pacific seawater. To investigate the role that phytoplankton may play in fractionating Zn isotopes, we have cultured T. oceanica at a variety of Zn concentrations and compared the phytoplankton to the media in which they were grown. Unwashed phytoplankton are 0.03 to 0.38 heavier than the media, indicating the preferential absorption of heavy Zn onto the cell surface. Cells washed with an oxalate-EDTA rinse to remove extracellular metals are lighter than the media by 0.16 to 0.80. The magnitude of biological fractionation is highest at high Zn concentrations. The difference in fractionation at different free Zn2+ ion concentrations appears to correspond to the relative importance of high-affinity and low-affinity uptake systems in metal transport. Hydrothermal vent fluids are found to have ?66Zn values between 0.05 and 1.33, spanning nearly the entire range reported for natural samples. Fluids from high temperature vents have generally heavier Zn isotope ratios, while those from low-temperature vents are more variable in their Zn isotope ratios and can be much lighter. Paired fluid and chimney samples from both high and low temperature vents allow us insight into the role of Zn sulphide precipitation in fractionating Zn isotopes.

John, S. G.; Geis, R. W.; Park, G.; Engwall, A.; Zhang, Z.; Bergquist, B. A.; Rouxel, O.; Saito, M. A.; Boyle, E. A.

2006-12-01

185

A stable isotope-based approach to tropical dendroclimatology  

NASA Astrophysics Data System (ADS)

We describe a strategy for development of chronological control in tropical trees lacking demonstrably annual ring formation, using high resolution ? 18O measurements in tropical wood. The approach applies existing models of the oxygen isotopic composition of alpha-cellulose (Roden et al., 2000), a rapid method for cellulose extraction from raw wood (Brendel et al., 2000), and continuous flow isotope ratio mass spectrometry (Brenna et al., 1998) to develop proxy chronological, rainfall and growth rate estimates from tropical trees lacking visible annual ring structure. Consistent with model predictions, pilot datasets from the temperate US and Costa Rica having independent chronological control suggest that observed cyclic isotopic signatures of several permil (SMOW) represent the annual cycle of local rainfall and relative humidity. Additional data from a plantation tree of known age from ENSO-sensitive northwestern coastal Peru suggests that the 1997-8 ENSO warm phase event was recorded as an 8 anomaly in the ? 18O of ?-cellulose. The results demonstrate reproducibility of the stable isotopic chronometer over decades, two different climatic zones, and three tropical tree genera, and point to future applications in paleoclimatology.

Evans, Michael N.; Schrag, Daniel P.

2004-08-01

186

Stable carbon isotope biogeochemistry of lakes along a trophic gradient  

NASA Astrophysics Data System (ADS)

The stable carbon (C) isotope variability of dissolved inorganic and organic C (DIC and DOC), particulate organic carbon (POC), glucose and polar-lipid derived fatty acids (PLFA) were studied in a survey of 22 North American oligotrophic to eutrophic lakes. The ?13C of different PLFA were used as proxy for phytoplankton producers and bacterial consumers. Lake pCO2 was primarily determined by autochthonous production (phytoplankton biomass), especially in eutrophic lakes, and governed the ?13C of DIC. All organic-carbon pools showed larger isotopic variability in eutrophic lakes compared to oligo-mesotrophic lakes because of the high variability in ?13C at the base of the food web (both autochthonous and allochthonous carbon). Phytoplankton ?13C was negatively related to lake pCO2 over all lakes and positively related to phytoplankton biomass in eutrophic lakes, which was also reflected in a large range in photosynthetic isotope fractionation (ϵCO2-phyto, 8-25 ). The carbon isotope ratio of allochthonous carbon in oligo-mesotrophic lakes was rather constant, while it varied in eutrophic lakes because of maize cultivation in the watershed.

de Kluijver, A.; Schoon, P. L.; Downing, J. A.; Schouten, S.; Middelburg, J. J.

2014-05-01

187

Calcium kinetics with microgram stable isotope doses and saliva sampling  

NASA Technical Reports Server (NTRS)

Studies of calcium kinetics require administration of tracer doses of calcium and subsequent repeated sampling of biological fluids. This study was designed to develop techniques that would allow estimation of calcium kinetics by using small (micrograms) doses of isotopes instead of the more common large (mg) doses to minimize tracer perturbation of the system and reduce cost, and to explore the use of saliva sampling as an alternative to blood sampling. Subjects received an oral dose (133 micrograms) of 43Ca and an i.v. dose (7.7 micrograms) of 46Ca. Isotopic enrichment in blood, urine, saliva and feces was well above thermal ionization mass spectrometry measurement precision up to 170 h after dosing. Fractional calcium absorptions determined from isotopic ratios in blood, urine and saliva were similar. Compartmental modeling revealed that kinetic parameters determined from serum or saliva data were similar, decreasing the necessity for blood samples. It is concluded from these results that calcium kinetics can be assessed with micrograms doses of stable isotopes, thereby reducing tracer costs and with saliva samples, thereby reducing the amount of blood needed.

Smith, S. M.; Wastney, M. E.; Nyquist, L. E.; Shih, C. Y.; Wiesmann, H.; Nillen, J. L.; Lane, H. W.

1996-01-01

188

A new method for stable lead isotope extraction from seawater.  

PubMed

A new technique for stable lead (Pb) isotope extraction from seawater is established using Toyopearl AF-Chelate 650M() resin (Tosoh Bioscience LLC). This new method is advantageous because it is semi-automated and relatively fast; in addition it introduces a relatively low blank by minimizing the volume of chemicals used in the extraction. Subsequent analyses by HR ICP-MS have a good relative external precision (2?) of 3.5 for (206)Pb/(207)Pb, while analyses by MC-ICP-MS have a better relative external precision of 0.6. However, Pb sample concentrations limit MC-ICP-MS analyses to (206)Pb, (207)Pb, and (208)Pb. The method was validated by processing the common Pb isotope reference material NIST SRM-981 and several GEOTRACES intercalibration samples, followed by analyses by HR ICP-MS, all of which showed good agreement with previously reported values. PMID:24120164

Zurbrick, Cheryl M; Gallon, Cline; Flegal, A Russell

2013-10-24

189

Intramolecular stable isotope distributions detect plant metabolic responses on century time scales  

NASA Astrophysics Data System (ADS)

Plants respond to environmental changes on a vast range of time scales, and plant gas exchanges constitute important feedback mechanisms in the global C cycle. Responses on time scales of decades to centuries are most important for climate models, for prediction of crop productivity, and for adaptation to climate change. Unfortunately, responses on these timescale are least understood. We argue that the knowledge gap on intermediate time scales is due to a lack of adequate methods that can bridge between short-term manipulative experiments (e.g. FACE) and paleo research. Manipulative experiments in plant ecophysiology give information on metabolism on time scales up to years. However, this information cannot be linked to results from retrospective studies in paleo research, because little metabolic information can be derived from paleo archives. Stable isotopes are prominent tools in plant ecophysiology, biogeochemistry and in paleo research, but in all applications to date, isotope ratios of whole molecules are measured. However, it is well established that stable isotope abundance varies among intramolecular groups of biochemical metabolites, that is each so-called "isotopomer" has a distinct abundance. This intramolecular variation carries information on metabolic regulation, which can even be traced to individual enzymes (Schleucher et al., Plant, Cell Environ 1999). Here, we apply intramolecular isotope distributions to study the metabolic response of plants to increasing atmospheric [CO2] during the past century. Greenhouse experiments show that the deuterium abundance among the two positions in the C6H2 group of photosynthetic glucose depends on [CO2] during growth. This is observed for all plants using C3 photosynthesis, and reflects the metabolic flux ratio between photorespiration and photosynthesis. Photorespiration is a major C flux that limits assimilation in C3 plants, which encompass the overwhelming fraction of terrestrial photosynthesis and the vast majority of crop species. To access century time scales, we traced this metabolic signal in historic material of two crop species during the past 100 years and find the same response as predicted from the greenhouse experiments. This allows estimating how much photorespiration has been reduced due to the anthropogenic CO2 emission during the 20th century, and shows that plants have not acclimated to increasing [CO2] during more than 100 generations. In summary, we demonstrate that metabolic responses of plants to environmental changes create intramolecular isotope signals. These signals can be identified in manipulation experiments and can be retrieved from plant archives. The isotope abundance of each intramolecular position is set by specific isotope fractionations, such as enzyme isotope effects or hydrogen exchange with xylem water (Augusti et al., Chem. Geol. 2008). Therefore it may be possible to simultaneously reconstruct several physiologic or climate signals from an archive of a single molecule. The principles governing intramolecular isotope distributions are general for all metabolites and isotopes (D, 13C), therefore intramolecular isotope distributions can multiply the information content of paleo archives. In particular, they allow extraction of metabolic information on long time scales, thereby connecting plant physiology with paleo research.

Schleucher, Jrgen; Ehlers, Ina; Augusti, Angela; Betson, Tatiana

2014-05-01

190

UNiquant, a Program for Quantitative Proteomics Analysis Using Stable Isotope Labeling  

PubMed Central

Stable isotope labeling (SIL) methods coupled with nanoscale liquid chromatography and high resolution tandem mass spectrometry are increasingly useful for elucidation of the proteome-wide differences between multiple biological samples. Development of more effective programs for the sensitive identification of peptide pairs and accurate measurement of the relative peptide/protein abundance are essential for quantitative proteomic analysis. We developed and evaluated the performance of a new program, termed UNiquant, for analyzing quantitative proteomics data using stable isotope labeling. UNiquant was compared with two other programs, MaxQuant and Mascot Distiller, using SILAC-labeled complex proteome mixtures having either known or unknown heavy/light ratios. For the SILAC-labeled Jeko-1 cell proteome digests with known heavy/light ratios (H/L = 1:1, 1:5, and 1:10), UNiquant quantified a similar number of peptide pairs as MaxQuant for the H/L = 1:1 and 1:5 mixtures. In addition, UNiquant quantified significantly more peptides than MaxQuant and Mascot Distiller in the H/L = 1:10 mixtures. UNiquant accurately measured relative peptide/protein abundance without the need for post-measurement normalization of peptide ratios, which is required by the other programs.

Huang, Xin; Tolmachev, Aleksey V.; Shen, Yulei; Liu, Miao; Huang, Lin; Zhang, Zhixin; Anderson, Gordon A.; Smith, Richard D.; Chan, Wing C.; Hinrichs, Steven H.; Fu, Kai; Ding, Shi-Jian

2011-01-01

191

Trophic position of deep-sea fishAssessment through fatty acid and stable isotope analyses  

NASA Astrophysics Data System (ADS)

To investigate the trophic ecology of two of the dominant families of deep-sea fish (Macrouridae and Moridae) fatty acid and stable isotope analyses were applied to liver and muscle samples of five abundant species from the NE Atlantic. In conjunction with stomach content data these methods made it possible to identify differences in feeding strategies between the five study species as well as variation in feeding in relation to increasing depth and body size. Biomarkers identified strong similarities between Coryphaenoides armatus and Antimora rostrata though differences were found associating C. armatus more with the benthic food web whereas A. rostrata showed stronger links to the pelagic food web. While Lepidion eques was classified as a species linking benthic and benthopelagic food webs, both fatty acid and stable isotope data suggested that Coryphaenoides guentheri fed on an exclusively benthic diet . Coryphaenoides rupestris on the other hand were largely dependent on a copepod-based food web. Ontogenetic changes in feeding were found for both A. rostrata and C. armatus with the indication of a switch from active predation to scavenging occurring with increasing body size. Biomarkers also reflected the seasonal influx from the photic zone though changes were species-specific and probably reflected the variation in prey availability and abundance in response to these inputs. Our findings have thus demonstrated that the combined use of these biomarkers can elucidate trophic specialisations in situations where conventional methods alone previously provided insufficient data.

Stowasser, G.; McAllen, R.; Pierce, G. J.; Collins, M. A.; Moffat, C. F.; Priede, I. G.; Pond, D. W.

2009-05-01

192

Protein Stable Isotope Fingerprinting (P-SIF): Multidimensional Protein Chromatography Coupled to Stable Isotope-Ratio Mass Spectrometry  

NASA Astrophysics Data System (ADS)

As metagenomics increases our insight into microbial community diversity and metabolic potential, new approaches are required to determine the biogeochemical expression of this potential within ecosystems. Because stable isotopic analysis of the major bioactive elements (C, N) has been used historically to map flows of substrates and energy among macroscopic food webs, similar principles may apply to microbes. To address this challenge, we have developed a new analytical approach called Protein Stable Isotope Fingerprinting (P-SIF). P-SIF generates natural stable isotopic fingerprints of microbial individual or community proteomes. The main advantage of P-SIF is the potential to bridge the gap between diversity and function, thereby providing a window into the "black box" of environmental microbiology and helping to decipher the roles of uncultivated species. Our method implements a three-way, orthogonal scheme to separate mixtures of whole proteins into subfractions dominated by single or closely-related proteins. Protein extracts first are isoelectrically focused in a gel-free technique that yields 12 fractions separated over a gradient of pH 3-10. Each fraction then is separated by size-exclusion chromatography into 20 pools, ranging from >100kD to ~10kD. Finally, each of these pools is subjected to HPLC and collected in 40 time-slices based on protein hydrophobicity. Theoretical calculation reveals that the true chromatographic resolution of the total scheme is 5000, somewhat less than the 9600 resulting fractions. High-yielding fractions are subjected to ?13C analysis by spooling-wire microcombustion irMS (SWiM-irMS) optimized for samples containing 1-5 nmol carbon. Here we will present the method, results for a variety of pure cultures, and preliminary data for a sample of mixed environmental proteins. The data show the promise of this method for unraveling the metabolic complexity hidden within microbial communities.

Pearson, A.; Bovee, R. J.; Mohr, W.; Tang, T.

2012-12-01

193

Variations in lead isotopic abundances in Sprague-Dawley rat tissues: possible reason of formation.  

PubMed

It has been reported in previous research that the lead isotopic composition of blood, urine and feces samples statistically differed from the given lead sources in Sprague-Dawley (SD) rats. However, the reason for this phenomenon is still unclear. An animal experiment was performed to investigate the lead isotope fractionation in diverse biological samples (i.e., lungs, liver, kidneys, bone) and to explore the possible reasons. SD rats were intratracheally instilled with lead acetate at the concentrations of 0, 0.02, 0.2, and 2 mg/kg body weight. Biological samples were collected for lead isotope analysis using an inductively coupled plasma mass spectrometry (ICP-MS). Significant differences are observed in lead isotope abundances among the diverse biological samples. The lead isotope abundances ((206)Pb, (207)Pb and (208)Pb) in diverse biological samples show different degrees and directions of departure from the given lead source. The results suggest that differences in enrichment or depletion capacity for each lead isotope in the various tissues might lead to the variation in lead isotopic abundances in tissues. Moreover, a nonlinear relationship between the blood lead level and the lead isotope abundances in liver and bone is observed. When the whole-blood level is higher than 50 ng/mL, the lead isotopic compositions of biological samples tend to be the same. Thus, the data support the speculation of a fractionation functional threshold. PMID:24587048

Liu, Duojian; Wu, Jing; Ouyang, Li; Wang, Jingyu

2014-01-01

194

Analysis of stable isotopes in fish to identify habitat use and switching  

EPA Science Inventory

In our isotopic studies of fish in Oregon Coast Range streams we have found stable isotopes of carbon, oxygen and sulfur to be surprisingly useful in identifying and discriminating specific habitat or tributary use by a variety of fish species. Stable isotopes of carbon can be u...

195

Stable Isotopic Studies and Ecosystem Research in Asia  

NASA Astrophysics Data System (ADS)

Stable isotope studies could contribute much to our understanding of ecosystem nutrient cycling, fate and transport of pollutants, and human impacts on the environment in Asia. As examples of ongoing studies within the Asian region that utilize stable isotopic techniques, results from two studies investigating relationships among patterns in ? 15N and net rates of nitrogen transformations in forest ecosystems in Taiwan are shown. In an evergreen hardwood forest in northeastern Taiwan (24 34 N, 121 34 E), soil ? 15N values in the forest floor ranged from -1.8 to 1.8 . Mineral soils had higher ? 15N values (4.1 to 6.0 ). Foliage ? 15N values for overstory trees ranged from -6.6 to -2.0 ). In a montane ecosystem in central Taiwan (23 28 N, 120 48 E)we found that net rates of N mineralization were related to soil C:N ratios. In this mixed grassland-forest system, foliar ? 15N values of the dominant species ranged from -6 to -3 . Surface soil ? 15N values were between -1 and 3 with a greater difference between foliar and soil values in grassland soils. Our results illustrate the need for more information regarding fundamental patterns in rates of ecosystem nitrogen cycling in Asia, especially as related to wider scale patterns in nutrient cycling within the region, to demonstrate potential insights from these kinds of studies.

Owen, J. S.; Wang, M. K.; King, H. B.; Kao, S. J.

2004-05-01

196

Stable nitrogen isotopes in coastal macroalgae: geographic and anthropogenic variability.  

PubMed

Growing human population adds to the natural nitrogen loads to coastal waters. Both anthropogenic and natural nitrogen is readily incorporated in new biomass, and these different nitrogen sources may be traced by the measurement of the ratio of stable nitrogen isotopes (?(15)N). In this study ?(15)N was determined in two species of macroalgae (Ascophyllum nodosum and Fucus vesiculosus), and in nitrate and ammonium to determine the relative importance of anthropogenic versus natural sources of nitrogen along the coast of NW Spain. Both algal species and nitrogen sources showed similar isotopic enrichment for a given site, but algal ?(15)N was not related to either inorganic nitrogen concentrations or ?(15)N in the water samples. The latter suggests that inorganic nitrogen inputs are variable and do not always leave an isotopic trace in macroalgae. However, a significant linear decrease in macroalgal ?(15)N along the coast is consistent with the differential effect of upwelling. Besides this geographic variability, the influence of anthropogenic nitrogen sources is evidenced by higher ?(15)N in macroalgae from rias and estuaries compared to those from open coastal areas and in areas with more than 1510(3) inhabitants in the watershed. These results indicate that, in contrast with other studies, macroalgal ?(15)N is not simply related to either inorganic nitrogen concentrations or human population size but depends on other factors as the upwelling or the efficiency of local waste treatment systems. PMID:23247291

Viana, Ins G; Bode, Antonio

2013-01-15

197

Anatomy of a cluster IDP. Part 2: Noble gas abundances, trace element geochemistry, isotopic abundances, and trace organic chemistry of several fragments from L2008#5  

NASA Technical Reports Server (NTRS)

The topics discussed include the following: noble gas content and release temperatures; trace element abundances; heating summary of cluster fragments; isotopic measurements; and trace organic chemistry.

Thomas, K. L.; Clemett, S. J.; Flynn, G. J.; Keller, L. P.; Mckay, David S.; Messenger, S.; Nier, A. O.; Schlutter, D. J.; Sutton, S. R.; Walker, R. M.

1994-01-01

198

Subterranean Sympatry: An Investigation into Diet Using Stable Isotope Analysis  

PubMed Central

In the Western Cape three species of mole-rat occur in sympatry, however, little is known about differences in their dietary preferences. Dietary composition of the three species; the common mole-rat (Cryptomys hottentotus hottentotus), the Cape mole-rat (Georychus capensis) and the Cape dune mole-rat (Bathyergus suillus) were examined using stable isotope analysis. Blood, fur and claw samples were collected from 70 mole-rats, in addition to several potential food items, to assess food selection of the three species under natural conditions. Overall there was a significant difference in the isotopic composition (?13C and ?15N) between all three species and significant differences in their diet composition. There were also significant differences between tissues in all three species suggesting temporal variation in diet. The small size and colonial lifestyle of C. h. hottentotus allows it to feed almost 100% on bulbs, while the solitary and larger species G. capensis and B. suillus fed to a greater extent on other resources such as grasses and clover. B. suillus, the largest of the species, had the most generalized diet. However, overall all species relied most heavily upon geophytes and consumed the same species suggesting competition for resources could exist. We also showed a high level of individual variation in diet choices. This was most pronounced in B. suillus and G. capensis and less so in C. h. hottentotus. We demonstrate that stable isotope analysis can successfully be applied to examine dietary patterns in subterranean mammals and provide insights into foraging patterns and dietary variation at both the inter and intra population level.

Robb, Gillian N.; Woodborne, Stephan; Bennett, Nigel C.

2012-01-01

199

Winds, Water Budgets and Stable Isotopes in Tropical Cyclones using TRMM and QUICKSCAT  

NASA Technical Reports Server (NTRS)

Water vapor is the most abundant greenhouse gas in the atmosphere. Changes in its concentration and distribution are controlled by the hydrologic cycle. Because of its capacity to absorb and emit long wave radiation, release latent heat during condensation in storms and reflect short wave radiation when clouds form it has a major impact on Global climate change. The stable isotope ratios of water are H20 H2l6O and H0 H2l6O. These ratios change whenever water undergoes a phase change. They also change in both rain and water vapor whenever an air parcel is exposed to rain. In addition the relative changes in the two ratios differ as a &nction of the relative humidity. In short, the stable isotope ratios in water vapor in the atmosphere contain an integrated history of the processes affecting the concentration and distribution of water vapor in the atmosphere. Therefore the measurement and interpretation of changes in these stable isotope ratios are a powerful tool matched by no other method in tracing the transport history of water in the atmosphere. Our initial studies under this grant focused on the changes of the stable isotope ratios of precipitation and water vapor in tropical cyclones. The changes in time and space were found to be very large and to trace the transport of water in the storms reflecting changes in basic structural features. Because the stable isotope ratios of rains from tropical cyclones are so low flooding associated with land falling tropical cyclones introduces a negative isotopic spike into the coastal surface waters. In addition the stable isotope ratios of water vapor in the vicinity of tropical cyclones is anomalously low. This suggests that carbonate shelled organisms such as ostracoda living in coastal waters have the potential to record the isotopic spike and thereby provide a long term record of tropical storm activity in sediment cores containing fossil shells. Likewise, tree rings in coastal environments offer a similar potential. We have analyzed the oxygen isotopic composition of ostrcoda shells formed in the floodwaters of Tropical Storm Allison (2001) and discovered the negative isotopic 1 16 spike. Because we had learned that storm activity has a major impact on the stable isotope ratios of water vapor in the tropics and sub-tropics we decided to analyze the isotopic compositions of water vapor in different locations in the tropics. We did this in Puerto Escondido, Mexico in July 1998, near Kwajalein Island in the Pacific in 1999 as part of a TRMM summer field program and in 2001 in Key West, Florida as part of the CAMEX 4 summer field program. Our isotopic studies along with our earlier tropical cyclone studies showed that the low isotopic ratios in water vapor induced by exposure to rains the storms persisted for 48 hours often far away from the original storm site. We also noted that positive isotopic spikes were introduced into atmospheric water vapor if winds were high and extensive sea spray was present. These findings have a significant impact on the interpretation of the stable isotope studies of tropical ice cores found in the high mountain regions of the tropics. The assumption made in interpreting the ice core record is that the source water vapor evaporated from the sea surface is in near isotopic equilibrium with the seawater and undergoes a decrease during its transport that reflects the change in temperature from the sea surface to the site of the ice core. Because an additional isotopic depletion occurs at the sea surface source area that depends on the intensity, duration and size of the tropical rain system the isotopic variations found in the ice cores must take into account changes in past storm activity in the tropics. These systems must be an important source of water vapor to the ice cores because they charge the troposphere with water vapor to a far greater vertical height than evaporation in quiescent regions. Finally, an interest in increased heat transfer in thnterior of tropical cyclones resulting from greater amounts of sea spray is a topic of considerab

Lawrence, James R.

2004-01-01

200

Quantitation of stable isotopic tracers of calcium by fast atom bombardment mass spectrometry  

SciTech Connect

Instrumentation and methodology developed for quantitation of stable isotopic traces in urine are described. Calcium is isolated from urine as the insoluble oxalate salt which is subsequently dissolved in hydrochloric acid. The isotopic content of the acid solution is determined by use of a conventional mass spectrometer equipped with a fast atom bombardment ion source. Calcium ions are desorbed from the sample surface by a beam of high-energy xenon atoms and detected with a high-resolution mass spectrometer. A data acquisition system has been developed to control the mass spectrometer and record the ion signals. Detailed analysis of potential sources of error indicates that the precision of the method is presently limited primarily by an isotope effect that occurs during ion desorption. Results presented here demonstrate that the relative abundances of calcium isotopes in urine can be determined with high precision (coefficient of variation < 0.2%) and that the method is a viable alternative to conventional thermal ionization mass spectrometry. The method is especially attractive because it uses a conventional high-resolution mass spectrometer which is routinely used for analysis of organic substances.

Jiang, X.; Smith, D.L.

1987-11-01

201

The stable carbon isotopes in enstatite chondrites and Cumberland Falls  

NASA Astrophysics Data System (ADS)

The carbon-isotopic composition (CIC) of the total carbon in the enstatite chondrites Indarch, Abee, St. Marks, Pillistfer, Hvittis and Daniel's Kuil and the enstatite achondrite Cumberland Falls has been measured. The empirical relationship between CIC and total carbon content is distinct from that of carbonaceous and ordinary chondrites. Within the enstatite chondrite group the average C-13 content increases with petrographic type: E4 less than E5 less than E6. Daniel's Kuil shows the largest C-13 enrichment in the bulk carbon of any meteorite. The CIC is most clearly correlated with the abundance of the elements Zn, Cd, and In. Insofar as these elements may hold the key to the understanding of enstatite chondrites, more detailed combined CIC and trace-element studies of these meteorites will play an important role in the deciphering of their history.

Deines, P.; Wickman, F. E.

1985-01-01

202

ANALYSIS OF RICIN TOXIN PREPARATIONS FOR CARBOHYDRATE AND FATTY ACID ABUNDANCE AND ISOTOPE RATIO INFORMATION  

SciTech Connect

This report describes method development and preliminary evaluation for analyzing castor samples for signatures of purifying ricin. Ricin purification from the source castor seeds is essentially a problem of protein purification using common biochemical methods. Indications of protein purification will likely manifest themselves as removal of the non-protein fractions of the seed. Two major, non-protein, types of biochemical constituents in the seed are the castor oil and various carbohydrates. The oil comprises roughly half the seed weight while the carbohydrate component comprises roughly half of the remaining mash left after oil and hull removal. Different castor oil and carbohydrate components can serve as indicators of specific toxin processing steps. Ricinoleic acid is a relatively unique fatty acid in nature and is the most abundant component of castor oil. The loss of ricinoleic acid indicates a step to remove oil from the seeds. The relative amounts of carbohydrates and carbohydrate-like compounds, including arabinose, xylose, myo-inositol fucose, rhamnose, glucosamine and mannose detected in the sample can also indicate specific processing steps. For instance, the differential loss of arabinose relative to mannose and N-acetyl glucosamine indicates enrichment for the protein fraction of the seed using protein precipitation. The methods developed in this project center on fatty acid and carbohydrate extraction from castor samples followed by derivatization to permit analysis by gas chromatography-mass spectrometry (GC-MS). Method descriptions herein include: the source and preparation of castor materials used for method evaluation, the equipment and description of procedure required for chemical derivatization, and the instrument parameters used in the analysis. Two types of derivatization methods describe analysis of carbohydrates and one procedure for analysis of fatty acids. Two types of GC-MS analysis is included in the method development, one employing a quadrupole MS system for compound identification and an isotope ratio MS for measuring the stable isotope ratios of deuterium and hydrogen (D/H) in fatty acids. Finally, the method for analyzing the compound abundance data is included. This study indicates that removal of ricinoleic acid is a conserved consequence of each processing step we tested. Furthermore, the stable isotope D/H ratio of ricinoleic acid distinguished between two of the three castor seed sources. Concentrations of arabinose, xylose, mannose, glucosamine and myo-inositol differentiated between crude or acetone extracted samples and samples produced by protein precipitation. Taken together these data illustrate the ability to distinguish between processes used to purify a ricin sample as well as potentially the source seeds.

Wunschel, David S.; Kreuzer-Martin, Helen W.; Antolick, Kathryn C.; Colburn, Heather A.; Moran, James J.; Melville, Angela M.

2009-12-01

203

A Redetermination of the Relative Abundances of the Isotopes of Neon, Krypton, Rubidium, Xenon, and Mercury  

Microsoft Academic Search

A careful redetermination of isotopic abundance ratios in neon, krypton, rubidium, xenon, and mercury has been made. The mass spectrometer employed was calibrated for mass discriminative effects with a synthetic argon isotope mixture made from essentially pure samples of A36 and A40. The present results together with those obtained from an earlier study on carbon, nitrogen, oxygen, argon, and potassium

Alfred O. Nier

1950-01-01

204

A quantitative approach to combine sources in stable isotope mixing models  

EPA Science Inventory

Stable isotope mixing models, used to estimate source contributions to a mixture, typically yield highly uncertain estimates when there are many sources and relatively few isotope elements. Previously, ecologists have either accepted the uncertain contribution estimates for indiv...

205

COMPOUND-SPECIFIC STABLE ISOTOPE ANALYSIS TO DEMONSTRATE IN-SITU MTBE BIOTRANSFORMATION  

EPA Science Inventory

Changes in the stable isotopic composition of organic contaminants (isotopic fractionation) are a useful indicator of biotransformation, and have been reported in literature for several volatile organic compounds. The technique offers an interesting alternative to time-consuming ...

206

COMPOUND-SPECIFIC STABLE ISOTOPE ANALYSIS TO DEMONSTRATE IN-SITU MTBE BIOTRANSFORMATION  

EPA Science Inventory

Change of stable isotope composition of organic contaminants (isotopic fractionation) is a useful indicator of biotransformation. Most of applications to date are in the area of chlorinated solvents and recently BTEX, MTBE and TBA. Chemical reactions (biotic- and abiotic transfor...

207

STABLE ISOTOPIC EVIDENCE OF CARBON AND NITROGEN USE IN CULTURED ECTOMYCORRHIZAL AND SAPROTROPHIC FUNGI  

EPA Science Inventory

Stable isotopes in sporocarps have proven useful for inferring ectomycorrhizal or saprotrophic status and understanding carbon (C) and nitrogen (N) utilization. However, greater understanding of processes producing isotopic concentrations is needed. We measured natural abundanc...

208

New technologies for small sample stable isotope measurement: static vacuum gas source mass spectrometry, laser probes, ion probes and gas chromatography-isotope ratio mass spectrometry  

NASA Astrophysics Data System (ADS)

Since there are 83 natural elements, any review of the use of mass spectrometry for the study of abundance and isotopic compositions of individual species in a geological environment, including locations beyond the Earth, has of necessity to be selective. This paper will focus on the studies of the so-called "light elements": hydrogen, carbon, nitrogen, oxygen, silicon and sulphur and their isotope systems. Five of the elements chosen (H, C, O, N and si) are amongst the most abundant in the cosmos, four (H, C, O and N) contribute substantially to life processes and choosing either C or Si together with O would allow as to account for > 60% of virtually all rocks. To further restrict the subject matter, I intend to concentrate on advances in the techniques for measurement of these elements. Amongst the most important advances in technology are the following: (i) the reduction of sample requirements for gas source stable isotope mass spectrometry into the picomole range; (ii) the application of focussed lasers as a means of extracting gas for isotopic measurement; (iii) a demonstration of the abilities of the ion microprobe (SIMS) in producing isotope measurements; and (iv) coupling of gas chromatography to stable isotope mass spectrometers for compound specific isotope analysis of complex mixtures. Some of the scientific highlights which have been achieved by the above means are respectively: (i) the identification of individual silicon carbide minerals as grains of interstellar dust; (ii) the demonstration of growth effects in diamonds of terrestrial and extraterrestrial origin; (iii) mineral specific isotopic compositions for complex geological materials; and (iv) unravelling the origin of mixtures of biomarkers in sedimentary environments.

Pillinger, C. T.

1992-09-01

209

Stable isotope pulse-chasing and compound specific stable carbon isotope analysis of phospholipid fatty acids to assess methane oxidizing bacterial populations in landfill cover soils.  

PubMed

The oxidation of methane by bacteria residing in soils constitutes an important terrestrial methane sink. These bacteria are particularly abundant in the covering soils of landfill caps due to the supply of high concentrations of methane from the landfill below. Only about 0.1% of soil bacteria are amenable to available methods of culturing, resulting in the need for a method of in situ analysis. A combination of phospholipid fatty acid (PLFA) analysis and stable isotopic labeling has been employed in this investigation as a means of cultivation-independent bacterial analysis. Soil samples taken from the profiles of two landfill caps, one of clay and one of sand, were incubated with 13C-labeled methane. PLFAs were analyzed by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) in order to determine their 13C content, from which the PLFA distribution of the methane-oxidizing bacteria was calculated. Neither landfill cap supported communities of bacteria capable of oxidizing ambient levels of methane but only those elevated levels that are usually attributable to landfills. The clay-capped landfill profile exhibited a change in the methane-oxidizing bacterial community with depth, whereas the sand-capped landfill site displayed a mixture of both type I and II methanotrophs throughout the profile. Two additional samples, taken from sites where methane production was evident, were particularly dominated by type II methanotrophic bacteria. PMID:15046336

Crossman, Zo M; Abraham, Faye; Evershed, Richard P

2004-03-01

210

Using stable isotope ratios to estimate atmospheric nitrogen fixed by cyanobacteria at the ecosystem scale.  

PubMed

Diazotrophic cyanobacteria are capable of fixing atmospheric N2 to satisfy their physiological nitrogen requirements. This process can result in the transfer of substantial amounts of "new" diazotrophic nitrogen (ND) to aquatic ecosystems during blooms of these taxa. Using in situ measurements of plankton natural abundance stable isotope composition and a combination of underway and fixed site survey data, the total N(D) flux into the Gippsland Lakes estuary (Australia) was estimated during a summer bloom of the diazotrophic cyanobacterium Nodularia spumigena. Over the course of the bloom, N(D) increased in the upper water column of the estuary from 33% +/- 17% (mean +/- SD) to 73% +/- 13% of the standing pool of total particulate N. A conservative estimate of total N(D) flux (146 Mg) equates to an estimated 177% of the summer total N load and 22% of the annual total N load to the estuary. Combining natural abundance stable isotope measurements with relatively simple fixed and underway survey designs can provide a cost-effective approach for monitoring the N(D) flux into estuary or lacustrine environments. This approach relies on an isotopic differential between the diazotrophic and the non-diazotrophic components of the plankton community; it may not be appropriate in ecosystems that experience low-level blooms or blooms of intermittent N-fixing cyanobacteria. Large-scale blooms of diazotrophic cyanobacteria are considered uncommon in estuaries, yet it is clear that these blooms can represent major sources of new N to estuarine ecosystems when and where they occur. PMID:24834739

Woodland, Ryan J; Cook, Perran L M

2014-04-01

211

Mathematical modeling of stable carbon isotope ratios in natural gases^@?  

NASA Astrophysics Data System (ADS)

A new approach is presented for mathematical modeling of stable carbon isotope ratios in hydrocarbon gases based on both theoretical and experimental data. The kinetic model uses a set of parallel first-order gas generation reactions in which the relative cracking rates of isotopically substituted (k?) and unsubstituted (k) bonds are represented by the equation k?/k=(Af?/Af) exp(-?Ea/RT), where R is the gas constant and T is temperature. Quantum chemistry calculations have been used to estimate the entropic (A f?/A f) and enthalpic (?Ea) terms for homolytic bond cleavage in a variety of simple molecules. For loss of a methyl group from a short-chain n-alkane (? C 6), for example, we obtain an average ?Ea of 42.0 cal/mol and an average A f?/A f of 1.021. Expressed differently, 13C-methane generation is predicted to be 2.4% (24) slower than 12C-methane generation (from a short-chain n-alkane) in a sedimentary basin at 200C but only 0.7% (7) slower in a laboratory heating experiment at 500C. Similar calculations carried out for homolytic bond cleavage in other molecules show that with few exceptions, ?Ea varies between 0 and 60 cal/mol and A f?/A f between 1.00 and 1.04. Examination of this larger data set reveals: (1) a weak sigmoid relationship between ?Ea and bond dissociation energy; and (2) a strong positive correlation between ?Ea and A f?/A f. The significance of these findings is illustrated by fitting a kinetic model to chemical and isotopic data for the generation of methane from n-octadecane under isothermal closed-system conditions. For a specific temperature history, the fitted model provides quantitative relationships among methane carbon isotope composition, total methane yield and methane generation rate which may have relevance to the cracking of oil-prone kerogens and crude oil. The observed variability of the kinetic reactivity of various methane source rocks highlights the need to apply and adequately calibrate such models with laboratory data for specific study areas. With this approach isotope data of natural gases can be used not only to estimate the time of gas generation in a sedimentary basin, but also to evaluate the source rock maturities at which specific accumulations were generated, and place constraints on trap charging histories.

Tang, Y.; Perry, J. K.; Jenden, P. D.; Schoell, M.

2000-08-01

212

High-precision isotope ratio mass spectrometry and stable isotope precursors for tracer studies in cell culture.  

PubMed

The use of stable isotope-labeled tracers is demonstrated in an in vitro system with analysis by high-precision isotope ratio mass spectrometry (IRMS), using n-3 long-chain polyunsaturated fatty acid (LCP) biosynthesis from [U-(13)C]18:3n-3 (18:3n-3*) in Y79 human retinoblastoma cells as a model system. The cells were cultured as a suspension in RPMI 1640 medium supplemented with 15% fetal calf serum at 37 degrees C with 5% CO(2) in air. They were harvested by sedimentation and cell lipids were extracted to determine the presence of 18:3n-3* metabolites using gas chromatography-combustion (GCC)-IRMS. As the dose of 18:3n-3* was systematically increased from treatment to treatment, the atom percent excess and the amounts of biosynthesized LCP* increased, while the percentage dose in each n-3 LCP* remained constant. Cultures incubated with 0.5 micromol (10 microM) of albumin-bound 18:3n-3, composed of 18:3n-3* diluted 1/60 or 1/100 with natural abundance 18:3n-3, yielded products with enrichments about 1.5 at.% excess (delta(13)C(PDB) < 1500 per thousand), which is optimal for high-precision measurements. Kinetics in Y79 cells incubated with 18:3n-3* showed that n-3 LCP* incorporation increased over time; 18:3n-3*, 20:5n-3*, 22:5n-3*, and 22:6n-3* were detected at all time points with the 1/60 dilution. These data document experimental parameters for optimal stable isotope use and IRMS detection for in vitro tracer methodology. PMID:11078586

Huang, M C; Muddana, S; Horowitz, E N; McCormick, C C; Infante, J P; Brenna, J T

2000-12-01

213

Stable carbon isotope analysis of nucleic acids to trace sources of dissolved substrates used by estuarine bacteria.  

PubMed Central

The natural abundance of stable carbon isotopes measured in bacterial nucleic acids extracted from estuarine bacterial concentrates was used to trace sources of organic matter for bacteria in aquatic environments. The stable carbon isotope ratios of Pseudomonas aeruginosa and nucleic acids extracted from cultures resembled those of the carbon source on which bacteria were grown. The carbon isotope discrimination between the substrate and total cell carbon from bacterial cultures averaged 2.3% +/- 0.6% (n = 13). Furthermore, the isotope discrimination between the substrate and nucleic acids extracted from bacterial cultures was 2.4% +/- 0.4% (n = 10), not significantly different from the discrimination between bacteria and the substrate. Estuarine water samples were prefiltered through 1-micron-pore-size cartridge filters. Bacterium-sized particles in the filtrates were concentrated with tangential-flow filtration and centrifugation, and nucleic acids were then extracted from these concentrates. Hybridization with 16S rRNA probes showed that approximately 90% of the nucleic acids extracted on two sample dates were of eubacterial origin. Bacteria and nucleic acids from incubation experiments using estuarine water samples enriched with dissolved organic matter from Spartina alterniflora and Cyclotella caspia had stable carbon isotope values similar to those of the substrate sources. In a survey that compared diverse estuarine environments, stable carbon isotopes of bacteria grown in incubation experiments ranged from -31.9 to -20.5%. The range in isotope values of nucleic acids extracted from indigenous bacteria from the same waters was similar, -27.9 to -20.2%. Generally, the lack of isotope discrimination between bacteria and nucleic acids that was noted in the laboratory was observed in the field.(ABSTRACT TRUNCATED AT 250 WORDS) Images

Coffin, R B; Velinsky, D J; Devereux, R; Price, W A; Cifuentes, L A

1990-01-01

214

Stable isotope study of the Ganga (Ganges) river system  

NASA Astrophysics Data System (ADS)

Stable hydrogen (?D) and oxygen (? 18O) isotope ratios of the Ganga river system are reported for the first time. High-altitude streams (Ganga headwaters) show a ?D-? 18O relationship close to that of the global meteoric water line. Samples from the lowland regions show a significant effect of evaporation, indicated by a reduced slope (of approximately six) in the ?D-? 18O plot. There is a progressive enrichment of the ? values downstream in the Ganga. The ? values of the Ganga headwaters show a change of -0.19 (? 18O) and -1.6 (?D) per 100 m increase in altitude (the 'altitude effect'), which is shown by a simple theoretical calculation to be half that in the local precipitation.

Ramesh, R.; Sarin, M. M.

1992-11-01

215

Stable isotopes as indicators for long term soil degradation  

NASA Astrophysics Data System (ADS)

We summarize the results of several studies that explored the suitability of stable isotope as indicators for soil degradation. Two approaches to indicate soil degradation were tested. The first one aims to identify soil erosion in hill slope transects from uplands (erosion source, oxic soils) to adjacent wetlands (erosion sink, anoxic soils) as it often occurs in mountain environments. The second aims at identifying long-term disturbance of oxic soils through decreasing correlations between ?13C and soil organic carbon (SOC), ?15N and N content, and ?15N and C:N ratio. Following the first approach, different stable isotope signatures can be expected for uplands and adjacent wetland soils. In our study, ?13C of SOC in wetland soils was with -28.3 0.6 olighter than those of upland soils (-26.6 0.6 o). Soil erosion is indicated by intermediate ?13C values (-27.5 0.5 o) of the wetland soil. Analogue oxic upland soils and wetlands not affected by soil erosion also differed in ?18O values. The upper horizons (0-10 cm) of upland soils had a mean ?18O between 5 and 15 o, while ?18O signatures of reference wetland soils varied between 15 and 20 o. Intermediate ?18O values for wetland soils adjacent to an upland can consequently be interpreted as mixing of soil erosion material with the organic wetland soil. Following the second approach, 'stable' landscape positions (reference sites), which are neither affected by erosion nor deposition are compared with disturbed sites. For undisturbed soils we expect that the enrichment of 15N and 13C with soil depth, due to fractionation during decomposition, goes in parallel with a decrease in N and SOC content. In the Swiss Alps, the soil profiles of the reference sites showed significant correlations between SOC content and its corresponding 13C signature. In contrast, for the eroding sites this relationship was not significant. The usefulness of the stable carbon isotope signature as a qualitative indicator for soil disturbance could be confirmed for a mountain site in South Korea. For the Korean site, we could further show that the 15N isotope signature can be used similarly for uncultivated sites. Further, ?15N is functionally related to the C:N ratio. In unperturbed sites ?15N values cover a relatively narrow range at any particular C:N ratio in soils within a large geographical region. Substantial loss, or gain of N, mostly results in the loss or gain of 15N-depleted forms. The latter results in larger or smaller ?15N values than usual at the observed C:N ratio and can serve as a soil disturbance indicator.

Meusburger, Katrin; Conen, Franz; Alewell, Christine

2014-05-01

216

The abundance of the radioactive isotope Al-26 in galactic cosmic rays  

NASA Technical Reports Server (NTRS)

Satellite observations of the isotopic composition of aluminum in low energy cosmic rays (E/M = 200 MeV/amu) have been used to determine the abundance of the unstable isotope Al-26 (T1/2 = 0.87 Myr). The observed abundance ratio, Al-26/Al-27 = 0.036 (+0.037, -0.022), is in good agreement with previous balloon observations and yields a cosmic ray confinement time consistent with values based on the abundance of Be-10.

Wiedenbeck, M. E.

1983-01-01

217

Stable carbon isotopes in bivalve shells as a salinity proxy  

NASA Astrophysics Data System (ADS)

Stable carbon isotopes of dissolved inorganic carbon (?13C-DIC) often vary with salinity in estuarine settings. Variations of salinity in estuaries also complicate temperature reconstructions based on oxygen isotope values in biological carbonates. Therefore having a salinity proxy could assist in estuarine temperature reconstruction as well as providing data on freshwater discharge into the estuary. Unfortunately, ?13C values in bivalve shells are potentially influenced by several sources of carbon including DIC, metabolic carbon and sediment pore-water DIC. This study first investigates the influence of these three potential carbon sources in the Manila clam (Ruditapes philippinarum) reared under laboratory conditions and then in the field during a two-year monitoring study. Metabolic carbon remained fairly constant in the laboratory (~12%) and we did not detect any difference between clams living in organic rich sediments and those in sediment free aquaria. There was a strong correlation between ?13C-shell and ?13C-DIC (r2=0.77) indicating that ?13C-shell can be used as a relative salinity indicator. In the field, calculated salinities were within the range of recorded salinities ( 5 salinity units), but there were significant differences between individuals. This study highlights the potential of using ?13C in bivalve shells as a salinity proxy, but also illustrates that large uncertainties are associated with this proxy.

Gillikin, D. P.; Poulain, C.; Mas, R.; Woule Ebongue, V.; Robert, R.; Paulet, Y.; Lorrain, A.

2010-12-01

218

Stable isotope studies on geothermal gases from the eastern part of Byk Menderes Graben (Turkey)  

NASA Astrophysics Data System (ADS)

We report new stable isotope data (?13C, ?15N) from three production wells of the Kizildere geothermal field and from three moffettes from the adjacent Tekke Hamam geothermal field, situated in the eastern segment of the Byk Menderes graben system (western Anatolia, Turkey). The data were discussed in the context of sources and provenance of N2, CO2 and CH4, as well as carbon isotope exchange and reservoir temperatures. ?13C values of CO2 fall in a narrow range with no systematic differences between both locations. The values suggest limestone as prime source of CO2, mixing with small and variable amounts of CO2 from other sources (organic-rich sediments, mantle CO2). In contrast, ?13C values of CH4 differ considerably between both sites and reveal an origin of methane from thermal degradation of organic matter. Computed temperatures from carbon isotope exchange between CO2 and CH4 are 30-50C higher than measured reservoir temperatures at Tekke Hamam and >80C higher at Kizildere, respectively. The carbon isotope disequilibrium is probably caused by mixing of gases from different sources (limestone, organic-rich sediments) and a relatively fast ascent of the volatiles. The higher temperature discrepancy at Kizildere can be explained by faster gas ascent through a drill well, compared to slower gas ascent through natural fractures and faults at Tekke Hamam. Air-corrected ?15N values fall between values suggested for a sedimentary source and the mantle, but are quite variable even for samples from the same location. Comprehensive discussion of the new data with noble gas isotopes and gas abundances from the same samples (Wiersberg et al., 2011) will help to quantify the contributions of gases from different sources and to characterize mixing and phase separation processes. Wiersberg et al. (2011), JVGR (208), p. 112-121

Wiersberg, T.; Grassa, F.; Suer, S.; Gulec, N.; Erzinger, J.; Parlaktuna, M.

2012-12-01

219

Stable isotopes (?13C and ?15N) of organic matrix from coral skeleton  

PubMed Central

The evolutionary success of reef-building corals in nutrient-poor tropical waters is attributed to endosymbiotic dinoflagellates. The algae release photosynthetic products to the coral animal cells, augment nutrient flux, and enhance the rate of coral calcification. Natural abundance of stable isotopes (?13C and ?18O) provides answers to modern and paleobiological questions about the effect of photosymbiosis on sources of carbon and oxygen in coral skeletal calcium carbonate. Here we compare 17 species of symbiotic and nonsymbiotic corals to determine whether evidence for photosymbiosis appears in stable isotopes (?13C and ?15N) of an organic skeletal compartment, the coral skeletal organic matrix (OM). Mean OM ?13C in symbiotic and nonsymbiotic corals was similar (-26.08 vs. -24.31), but mean OM ?15N was significantly depleted in 15N in the former (4.09) relative to the latter (12.28), indicating an effect of the algae on OM synthesis and revealing OM ?15N as a proxy for photosymbiosis. To answer an important paleobiological question about the origin of photosymbiosis in reef-building corals, we applied this proxy test to a fossil coral (Pachythecalis major) from the Triassic (240 million years ago) in which OM is preserved. Mean OM ?15N was 4.66, suggesting that P. major was photosymbiotic. The results show that symbiotic algae augment coral calcification by contributing to the synthesis of skeletal OM and that they may have done so as early as the Triassic.

Muscatine, Leonard; Goiran, Claire; Land, Lynton; Jaubert, Jean; Cuif, Jean-Pierre; Allemand, Denis

2005-01-01

220

Stable isotope ecohydrology of semiarid shrubland in northwestern Mexico  

NASA Astrophysics Data System (ADS)

Ecosystem fluxes in seasonally dry ecosystems are fundamentally driven by availability of water and further ecohydrolgical processes that are triggered during the wet-growing season. One of the initial steps towards defining the functional fate of precipitation in ecosystems (i.e. influence on productivity or decomposition) is to partition evapotranspiration (ET) into its component fluxes. Aided by a real time field monitoring scheme of stable isotopes of water vapor to produce Keeling plots and micromet-driven modeling of the isotopic composition of soil evaporation (E) and transpiration (T) of representative species of a subtropical shrubland, we aimed to partitioning ET at hourly time steps during the peak monsoon season. The study was conducted in the state of Sonora Mexico at a long term eddy covariance monitoring site part of MexFlux. The ecosystem is a legume-rich subtropical shrubland that gets 550 mm of rain yearly with 70% of the total occurring during the summer monsoon season. Preliminary results indicate that on a daily scale in this ecosystem T is the dominant component of ET (T/ET 0.8 to 1) during the early morning (7 to 10 hrs local time) but drops to 60 to 50 % during the warmest part of the day (11 to 15 hrs) when the vegetation down regulate stomatal conductance and solar radiation reaches more directly the soil. Later in the afternoon (16 to 18 hrs), T/ET generally bounces back to 0.8 to 0.9 levels. Although the actual T/ET fraction varies depending on the soil moisture content in shallow soil layers, this general pattern is maintained many days through the warm rainy season and has implications to attribute the influence of rain to ecosystem function.

Yepez, E. A.; Tarin, T.; Garatuza-Payan, J.; Watts, C. J.; Rodriguez, J. C.; Vivoni, E.; Robles-Morua, A.

2013-05-01

221

The fish of Lake Titicaca: implications for archaeology and changing ecology through stable isotope analysis  

Microsoft Academic Search

Research on past human diets in the southern Lake Titicaca Basin has directed us to investigate the carbon and nitrogen stable isotopes of an important dietary element, fish. By completing a range of analyses on modern and archaeological fish remains, we contribute to two related issues regarding the application of stable isotope analysis of archaeological fish remains and in turn

Melanie J. Miller; Jos M. Capriles; Christine A. Hastorf

2010-01-01

222

Using Bayesian Stable Isotope Mixing Models to Enhance Marine Ecosystem Models  

EPA Science Inventory

The use of stable isotopes in food web studies has proven to be a valuable tool for ecologists. We investigated the use of Bayesian stable isotope mixing models as constraints for an ecosystem model of a temperate seagrass system on the Atlantic coast of France. d13C and d15N i...

223

Stable isotopic variations in west China: A consideration of moisture sources  

Microsoft Academic Search

In this study, individual precipitation samples, collected over 2 years at stations in different climatic regions of west China (Tibetan Plateau region, Tianshan region, and Altay) were analyzed for the stable isotopes of precipitation to improve our understanding of how vapor transport impacts the modern stable isotopic distribution. Our results identify regional patterns in both ?18O and deuterium excess (D

Lide Tian; Tandong Yao; K. MacClune; J. W. C. White; A. Schilla; B. Vaughn; R. Vachon; K. Ichiyanagi

2007-01-01

224

What is the main food source of the shipworm (Teredo navalis)? A stable isotope approach  

NASA Astrophysics Data System (ADS)

Stable isotope analysis of soft bodies of the shipworm Teredo navalis demonstrated that this species is mainly feeding on seston by filter feeding in contrast to wood consumption. T. navalis showed similar stable isotope values (?13C, ?15N) as Mytilus edulis and Crassostrea gigas, which species were attached to the wood instead of boring into.

Paalvast, Peter; van der Velde, Gerard

2013-07-01

225

Geospatial modeling of plant stable isotope ratios - the development of isoscapes  

Microsoft Academic Search

Large-scale spatial variation in stable isotope ratios can yield critical insights into the spatio-temporal dynamics of biogeochemical cycles, animal movements, and shifts in climate, as well as anthropogenic activities such as commerce, resource utilization, and forensic investigation. Interpreting these signals requires that we understand and model the variation. We report progress in our development of plant stable isotope ratio landscapes

J. B. West; J. R. Ehleringer; J. M. Hurley; T. E. Cerling

2007-01-01

226

Water stable isotope measurements of Antarctic samples by means of IRMS and WS-CRDS techniques  

Microsoft Academic Search

In the last years in the scientific community there has been an increasing interest for the application of stable isotope techniques to several environmental problems such as drinking water safeguarding, groundwater management, climate change, soils and paleoclimate studies etc. For example, the water stable isotopes, being natural tracers of the hydrological cycle, have been extensively used as tools to characterize

Marzia Michelini; Mattia Bonazza; Martina Braida; Onelio Flora; Giuliano Dreossi; Barbara Stenni

2010-01-01

227

USING STABLE ISOTOPES FOR FISH DIETARY ANALYSES: COPING WITH TOO MANY SOURCES  

EPA Science Inventory

Stable isotope analysis can provide a useful tool for determining time-integrated measures of proportional food source contributions to fish diets. Ratios of stable (non-radioactive) isotopes of common elements (e.g., C,N,S) vary among food sources, and tissues of consumers (e.g...

228

Lipid Correction for Carbon Stable Isotope Analysis of Deep-sea Fishes  

EPA Science Inventory

Lipid extraction is used prior to stable isotope analysis of fish tissues to remove variability in the carbon stable isotope ratio (d13C) caused by varying lipid content among samples. Our objective was to evaluate an application of a mass balance correction for the effect of lip...

229

The Role of Naturally Occurring Stable Isotopes in Mass Spectrometry, Part I: The Theory  

PubMed Central

In this tutorial, the authors explain how naturally occurring stable isotopes are contributing to experimentally determined mass spectra and how this information can be exploited in quantitative experiments, structural elucidation studies and tracer methodologies. The first instalment of this two part series focuses on the theoretical aspects of stable isotopes and the calculation of their distribution patterns.

Bluck, Les; Volmer, Dietrich A.

2013-01-01

230

Stable isotope profiles of partially migratory salmonid populations in Atlantic rivers of Patagonia  

Microsoft Academic Search

In the present study, profiles of stable isotope composition were characterized for two species with partially migratory populations in rivers along the latitudinal gradient of Patagonia, brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss. The effects of factors (e.g. ontogeny of fishes, location, species and fasting) that may influence the stable isotope analysis (SIA) were evaluated, as was SIA

J. E. Ciancio; M. A. Pascual; F. Botto; M. Amaya-Santi; S. ONeal; C. Riva Rossi; O. Iribarne

2008-01-01

231

Using Stable Isotopes to Estimate Trophic Position: Models, Methods, and Assumptions  

Microsoft Academic Search

The stable isotopes of nitrogen (d15N) and carbon (d13C) provide powerful tools for estimating the trophic positions of and carbon flow to consumers in food webs; however, the isotopic signature of a consumer alone is not generally sufficient to infer trophic position or carbon source without an appropriate isotopic baseline. In this paper, I develop and discuss methods for generating

David M. Post

2002-01-01

232

A Teaching Exercise to Introduce Stable Isotope Fractionation of Metals into Geochemistry Courses  

ERIC Educational Resources Information Center

Variations in the isotopic composition of elements have been widely used to study earth's climate, biosphere, and interior, and more recently to track the fate of contaminants. Within the broad range of elements that exhibit measureable isotopic variations, metal stable isotopes are increasingly applied across the biological, geological,

Weiss, Dominik J.; Harris, Caroline; Maher, Kate; Bullen, Thomas

2013-01-01

233

Stable isotope paleoaltimetry of high relief terrain: An atmospheric dynamics and landscape evolution perspective  

Microsoft Academic Search

Stable isotope ratios in rain and snow from mountainous regions show a strong correlation with altitude. To the extent that these isotopic ratios are preserved in the geological record, they may provide a powerful constraint on the surface uplift history of mountain belts. Existing interpretive frameworks for paleoaltimetry are based on linear regressions of modern precipitation isotope transects or on

J. Galewsky

2009-01-01

234

Stable isotope paleoaltimetry of high relief terrain: An atmospheric dynamics perspective  

Microsoft Academic Search

Stable isotope ratios in rain and snow from mountainous regions show a strong correlation with altitude. To the extent that these isotopic ratios are preserved in the geological record, they may provide a powerful constraint on the surface uplift history of mountain belts. Existing interpretive frameworks for paleoaltimetry are based on linear regressions of modern precipitation isotope transects or on

J. Galewsky

2008-01-01

235

Fast or feast: reconstructing diet in later medieval England by stable isotope analysis  

Microsoft Academic Search

In this pilot-study, which was designed to assess the range of isotopic variation in English medieval populations, we present the results of stable isotope analysis of carbon and nitrogen of human and animal bone collagen from three later medieval sites in Northern England. The isotopic values observed for the rural hospital of St. Giles by Brompton Bridge (N. Yorks.), the

Gundula Muldner; Michael P. Richards

236

Spatial analysis of stable isotope data to determine primary sources of nutrition for fish  

Microsoft Academic Search

Carbon and nitrogen stable isotopes were used to determine the ultimate autotrophic sources supporting production of three commercially important fish species over unvegetated mudflats in a subtropical estuary. Mean isotope values over the whole estuary for fish and autotroph sources were modeled to indicate feasible combinations of sources. Variability in isotope values among nine locations (separated by 310km) was then

Andrew J. Melville; Rod M. Connolly

2003-01-01

237

Forensic applications of light-element stable isotope ratios of Ricinus communis seeds and ricin preparations.  

PubMed

Seeds of the castor plant Ricinus communis are of forensic interest because they are the source of the poison ricin. We tested whether stable isotope ratios of castor seeds and ricin preparations can be used as a forensic signature. We collected over 300 castor seed samples worldwide and measured the C, N, O, and H isotope ratios of the whole seeds and oil. We prepared ricin by three different procedures, acetone extraction, salt precipitation, and affinity chromatography, and compared their isotope ratios to those of the source seeds. The N isotope ratios of the ricin samples and source seeds were virtually identical. Therefore, N isotope ratios can be used to correlate ricin prepared by any of these methods to source seeds. Further, stable isotope ratios distinguished >99% of crude and purified ricin protein samples in pairwise comparison tests. Stable isotope ratios therefore constitute a valuable forensic signature for ricin preparations. PMID:23130759

Kreuzer, Helen W; West, Jason B; Ehleringer, James R

2013-01-01

238

Documenting the diet in ancient human populations through stable isotope analysis of hair.  

PubMed

Fundamental to the understanding of human history is the ability to make interpretations based on artefacts and other remains which are used to gather information about an ancient population. Sequestered in the organic matrices of these remains can be information, for example, concerning incidence of disease, genetic defects and diet. Stable isotopic compositions, especially those made on isolates of collagen from bones, have been used to help suggest principal dietary components. A significant problem in the use of collagen is its long-term stability, and the possibility of isotopic alteration during early diagenesis, or through contaminating condensation reactions. In this study, we suggest that a commonly overlooked material, human hair, may represent an ideal material to be used in addressing human diets of ancient civilizations. Through the analysis of the amino-acid composition of modern hair, as well as samples that were subjected to radiation (thus simulating ageing of the hair) and hair from humans that is up to 5200 years old, we have observed little in the way of chemical change. The principal amino acids observed in all of these samples are essentially identical in relative abundances and content. Dominating the compositions are serine, glutamic acid, threonine, glycine and leucine, respectively accounting for approximately 15%, 17%, 10%, 8% and 8% of the total hydrolysable amino acids. Even minor components (for example, alanine, valine, isoleucine) show similar constancy between the samples of different ages. This constancy clearly indicates minimal alteration of the amino-acid composition of the hair. Further, it would indicate that hair is well preserved and is amenable to isotopic analysis as a tool for distinguishing sources of nutrition. Based on this observation, we have isotopically characterized modern individuals for whom the diet has been documented. Both stable nitrogen and carbon isotope compositions were assessed, and together provide an indication of trophic status, and principal type (C3 or C4) of vegetation consumed. True vegans have nitrogen isotope compositions of about 7/1000 whereas humans consuming larger amounts of meat, eggs, or milk are more enriched in the heavy nitrogen isotope. We have also analysed large cross-sections of modern humans from North America and Europe to provide an indication of the variability seen in a population (the supermarket diet). There is a wide diversity in both carbon and nitrogen isotope values based at least partially on the levels of seafood, corn-fed beef and grains in the diets. Following analysis of the ancient hair, we have observed similar trends in certain ancient populations. For example, the Coptics of Egypt (1000 BP) and Chinchorro of Chile (5000-800 BP) have diets of similar diversity to those observed in the modern group but were isotopically influenced by local nutritional sources. In other ancient hair (Egyptian Late Middle Kingdom mummies, ca. 4000 BP), we have observed a much more uniform isotopic signature, indicating a more constant diet. We have also recognized a primary vegetarian component in the diet of the Neolithic Ice Man of the Oetztaler Alps (5200 BP). In certain cases, it appears that sulphur isotopes may help to further constrain dietary interpretations, owing to the good preservation and sulphur content of hair. It appears that analysis of the often-overlooked hair in archaeological sites may represent a significant new approach for understanding ancient human communities. PMID:10091248

Macko, S A; Engel, M H; Andrusevich, V; Lubec, G; O'Connell, T C; Hedges, R E

1999-01-29

239

Documenting the diet in ancient human populations through stable isotope analysis of hair.  

PubMed Central

Fundamental to the understanding of human history is the ability to make interpretations based on artefacts and other remains which are used to gather information about an ancient population. Sequestered in the organic matrices of these remains can be information, for example, concerning incidence of disease, genetic defects and diet. Stable isotopic compositions, especially those made on isolates of collagen from bones, have been used to help suggest principal dietary components. A significant problem in the use of collagen is its long-term stability, and the possibility of isotopic alteration during early diagenesis, or through contaminating condensation reactions. In this study, we suggest that a commonly overlooked material, human hair, may represent an ideal material to be used in addressing human diets of ancient civilizations. Through the analysis of the amino-acid composition of modern hair, as well as samples that were subjected to radiation (thus simulating ageing of the hair) and hair from humans that is up to 5200 years old, we have observed little in the way of chemical change. The principal amino acids observed in all of these samples are essentially identical in relative abundances and content. Dominating the compositions are serine, glutamic acid, threonine, glycine and leucine, respectively accounting for approximately 15%, 17%, 10%, 8% and 8% of the total hydrolysable amino acids. Even minor components (for example, alanine, valine, isoleucine) show similar constancy between the samples of different ages. This constancy clearly indicates minimal alteration of the amino-acid composition of the hair. Further, it would indicate that hair is well preserved and is amenable to isotopic analysis as a tool for distinguishing sources of nutrition. Based on this observation, we have isotopically characterized modern individuals for whom the diet has been documented. Both stable nitrogen and carbon isotope compositions were assessed, and together provide an indication of trophic status, and principal type (C3 or C4) of vegetation consumed. True vegans have nitrogen isotope compositions of about 7/1000 whereas humans consuming larger amounts of meat, eggs, or milk are more enriched in the heavy nitrogen isotope. We have also analysed large cross-sections of modern humans from North America and Europe to provide an indication of the variability seen in a population (the supermarket diet). There is a wide diversity in both carbon and nitrogen isotope values based at least partially on the levels of seafood, corn-fed beef and grains in the diets. Following analysis of the ancient hair, we have observed similar trends in certain ancient populations. For example, the Coptics of Egypt (1000 BP) and Chinchorro of Chile (5000-800 BP) have diets of similar diversity to those observed in the modern group but were isotopically influenced by local nutritional sources. In other ancient hair (Egyptian Late Middle Kingdom mummies, ca. 4000 BP), we have observed a much more uniform isotopic signature, indicating a more constant diet. We have also recognized a primary vegetarian component in the diet of the Neolithic Ice Man of the Oetztaler Alps (5200 BP). In certain cases, it appears that sulphur isotopes may help to further constrain dietary interpretations, owing to the good preservation and sulphur content of hair. It appears that analysis of the often-overlooked hair in archaeological sites may represent a significant new approach for understanding ancient human communities.

Macko, S A; Engel, M H; Andrusevich, V; Lubec, G; O'Connell, T C; Hedges, R E

1999-01-01

240

[Applications of stable isotope techniques in the studies of soil collembolan: a review].  

PubMed

The development and application of stable isotope techniques is one of the most important progress in ecological methodologies in the 1990s. Many ecological processes are accompanied with the changes of stable isotopes ratio. According to these changes, the material circulation and energy flow of ecosystems can be followed. In recent years, many researchers introduced stable isotope techniques in soil ecology to study the soil carbon cycle and the trophic relationships between soil organisms, which greatly improved our understanding on belowground ecosystem. As for collembolan, one of the most important members of soil animals, its feeding habits and trophic position in soil ecosystem are little known. Stable isotope techniques provide a useful approach to study the food resources, trophic position, and trophic relationships of collembolan. This paper summarized the applications of stable isotope techniques in the studies of the feeding habits and trophic position of collembolan, and discussed the deficiencies and prospects of related researches. PMID:24066567

Wang, Min; Xu, Guo-Liang

2013-06-01

241

Cosmic ray isotope abundances from chromium to nickel  

NASA Technical Reports Server (NTRS)

IRIS, a telescope consisting of a large-area precision Cerenkov detector, scintillators, spark chambers, and a passive stack of Lexan polycarbonate track detectors, was exposed to the primary cosmic radiation for 6.6 sq m sr hr in a balloon flight in 1976. This measurement has yielded the isotopic composition of the iron-group elements Cr, Mn, Fe, and Ni with an average mass resolution of 0.65 amu for the energies 320-500 MeV per amu at the detector. This experiment places the most severe constraints to date on deviation from solar-system composition of the source of the cosmic radiation. Upper limits of 10 percent are placed on the ratios Fe-54/Fe-56 and Fe-58/Fe-56, which are inconsistent with large departures from solar system source composition reported by other workers. The isotopic measurements of Fe and Ni preclude the possibility that these cosmic rays were produced in a single e-process zone. The mean mass of Mn is less than 55, indicating the presence of electron-capture species produced by spallation.

Tarle, G.; Ahlen, S. P.; Cartwright, B. G.

1979-01-01

242

Stable isotope studies of nicotine kinetics and bioavailability  

SciTech Connect

The stable isotope-labeled compound 3',3'-dideuteronicotine was used to investigate the disposition kinetics of nicotine in smokers, the systemic absorption of nicotine from cigarette smoke, and the bioavailability of nicotine ingested as oral capsules. Blood levels of labeled nicotine could be measured for 9 hours after a 30-minute intravenous infusion. Analysis of disposition kinetics in 10 healthy men revealed a multiexponential decline after the end of an infusion, with an elimination half-life averaging 203 minutes. This half-life was longer than that previously reported, indicating the presence of a shallow elimination phase. Plasma clearance averaged 14.6 ml/min/kg. The average intake of nicotine per cigarette was 2.29 mg. A cigarette smoke-monitoring system that directly measured particulate matter in smoke was evaluated in these subjects. Total particulate matter, number of puffs on the cigarette, total puff volume, and time of puffing correlated with the intake of nicotine from smoking. The oral bioavailability of nicotine averaged 44%. This bioavailability is higher than expected based on the systemic clearance of nicotine and suggests that there may be significant extrahepatic metabolism of nicotine.

Benowitz, N.L.; Jacob, P. 3d.; Denaro, C.; Jenkins, R. (Univ. of California, San Francisco (USA))

1991-03-01

243

SHRIMP SI- New Capabilities for in situ Stable Isotope Analysis  

NASA Astrophysics Data System (ADS)

The SHRIMP SI is the latest generation of SHRIMP ion microprobe that has been optimised for light stable isotope analysis. The initial configuration has been set for Cs+ primary ion beam (ca. 15kV) and negative secondary extraction (ca. 10kV). The specific design inherits features from both SHRIMP I, and SHRIMP II instruments, but also has lens configurations that are unique. The primary column has two modes: a configuration allowing Kohler illumination, and a critical illumination system allowing spot sizes down to under a micrometer. The secondary extraction system utilizes an intermediate extraction lens to transfer the secondary ion beam to a separate beam matching chamber containing three quadrupole lenses. SHRIMP SI uses the same proven mass analyser design of the other forward geometry SHRIMPs.The collector has been designed around a minimum unit spacing at approximately mass 40 enabling large ETP multipliers to be used, or standard large dimension Faraday cups. The construction phase is now complete and SHRIMP SI is undergoing initial performance evaluation.

Ireland, T. R.; Clement, S.; Foster, J.

2010-12-01

244

Stable nitrogen isotopes of nestling tree swallows indicate exposure to different types of oil sands reclamation.  

PubMed

Tree swallows (Tachycineta bicolor) inhabiting reclaimed wetlands on the oil sands in northern Alberta are potentially exposed to elevated levels of oil sands constituents such as polycyclic aromatic compounds (PAC) through diet. While increased detoxification enzyme activity as measured using 7-ethoxyresorufin O-deethylase in nestlings is a generally accepted indicator of exposure to oil sands constituents, there is no apparent method to detect dietary exposure specific to oil sands processed material (OSPM). In this study, stable C and N isotopes were analyzed from muscle and feathers of nestling tree swallows (15 d old) to distinguish dietary exposure of birds near reference and OSPM wetlands. High ??N and low ?C values in the nestling tissues differentiated those from the OSPM wetlands and reference sites. Lower ??N values of nestlings compared to the ??N values of larval chironomids from an earlier study suggested that the majority of the diet of the nestlings was derived from non-OSPM sources, despite residence near and on the OSPM wetlands. Our finding of limited utilization of OSPM resources by tree swallows indicates either low abundance or diversity of dietary items emerging from OSPM wetlands, or sensory avoidance of prey from those wetlands. Minimal consumption of OSPM-derived dietary sources may be attributed to published findings of limited adverse effects on tree swallow reproduction, or growth and development for these same nestlings. This study demonstrated that stable isotope analysis, particularly for N isotopes, may serve as a useful tool to trace dietary exposure to OSPM constituents as part of avian ecotoxicology assessments of reclaimed wetlands on the oil sands. PMID:24627996

Farwell, A J; Harms, N J; Smits, J E G; Dixon, D G

2014-01-01

245

Status of stable isotope enrichment, products, and services at the Oak Ridge National Laboratory  

NASA Astrophysics Data System (ADS)

The Oak Ridge National Laboratory (ORNL) has been supplying enriched stable and radioactive isotopes to the research, medical, and industrial communities for over 50 y. Very significant changes have occurred in this effort over the past several years, and, while many of these changes have had a negative impact on the availability of enriched isotopes, more recent developments are actually improving the situation for both the users and the producers of enriched isotopes. ORNL is still a major producer and distributor of radioisotopes, but future isotope enrichment operations to be conducted at the Isotope Enrichment Facility (IEF) will be limited to stable isotopes. Among the positive changes in the enriched stable isotope area are a well-functioning, long-term contract program, which offers stability and pricing advantages; the resumption of calutron operations; the adoption of prorated conversion charges, which greatly improves the pricing of isotopes to small users; ISO 9002 registration of the IEF's quality management system; and a much more customer-oriented business philosophy. Efforts are also being made to restore and improve upon the extensive chemical and physical form processing capablities that once existed in the enriched stable isotope program. Innovative ideas are being pursued in both technical and administrative areas to encourage the beneficial use of enriched stable isotopes and the development of related technologies.

Scott Aaron, W.; Tracy, Joe G.; Collins, Emory D.

246

The isotopic and elemental abundances of neon nuclei accelerated in solar flares  

NASA Technical Reports Server (NTRS)

The relative isotopic abundances of Ne-20 and Ne-22 in seven solar flares were determined from measurements of the satellite IMP 8, yielding the ratio Ne-20/Ne-22 = 7.7 (+2.3, -1.5) for solar chromospheric matter. This value is in agreement with the ratio for the component neon-A (the 'primordial' component) found in carbonaceous chondrites. An elemental abundance ratio Ne/O = 0.14 + or - 0.01 also has been obtained which agrees closely with earlier reported measurements. It is shown that the effects of preferential acceleration relative to solar-system abundances with increasing charge number observed for some solar flares - though biasing the elemental ratio - does not appear to influence the neon isotopic abundances.

Dietrich, W. F.; Simpson, J. A.

1979-01-01

247

Cosmic-Ray-Produced Stable Isotopes in Iron Meteorites  

Microsoft Academic Search

The isotopic composition of vanadium, calcium, and potassium extracted ; from several iron meteorites was measured. The isotopes V⁵°, Ca⁴⁶, ; Ca⁴³, and K⁴° were found to be strongly enriched by cosmic-ray-; induced spallation reactions. The concentrations of these isotopes were ; determined by isotopic dilution techniques. The results are compared with data ; on cosmogenic Sc⁴⁵ and rare gas

Heinz Stauffer; Masatake Honda

1962-01-01

248

Nitrate stable isotopes: Tools for determining nitrate sources among different land uses in the Mississippi River Basin  

USGS Publications Warehouse

A study was conducted to determine whether NO3- stable isotopes (??15N and ??18O), at natural abundance levels, could discriminate among NO3- sources from sites with different land uses at the basin scale. Water samples were collected from 24 sites in the Mississippi River Basin from five land-use categories: (1) large river basins (>34 590 km2) draining multiple land uses and smaller basins in which the predominant land use was (2) urban (3) undeveloped, (4) crops, or (5) crops and livestock. Our data suggest that riverine nitrates from different land uses have overlapping but moderately distinct isotopic signatures. ??18O data were critical in showing abrupt changes in NO3- source with discharge. The isotopic values of large rivers resembled crop sites, sites with livestock tended to have ??15N values characteristic of manure, and urban sites tended to have high ??18O values characteristic of atmospheric nitrate.

Chang, C. C. Y.; Kendall, C.; Silva, S. R.; Battaglin, W. A.; Campbell, D. H.

2002-01-01

249

Contribution of stable isotopes to the understanding of the unsaturated zone of a carbonate aquifer (Nerja Cave, southern Spain)  

NASA Astrophysics Data System (ADS)

We analysed the stable isotopes ( 18O and 2H) of rainwater and drip water within a cave (Nerja Cave) located in the unsaturated zone of a carbonate aquifer. Rainfall is more abundant and presents lower isotopic content in winter, while the volume of drip water is greater and its isotopic content is lower in summer. The flow analysis of 18O through the unsaturated zone confirms the seasonal lag between rainfall and the appearance of drip water in the cave and reveals that the unsaturated zone of the aquifer, in the sector of the cave, behaves like an inertial system with a strong capability to modulate the input signal. To cite this article: F. Carrasco et al., C. R. Geoscience 338 (2006).

Carrasco, Francisco; Andreo, Bartolom; Lin, Cristina; Mudry, Jacques

2006-12-01

250

Stable isotope analysis indicates a lack of inter- and intra-specific dietary redundancy among ecologically important coral reef fishes  

NASA Astrophysics Data System (ADS)

Parrotfish are critical consumers on coral reefs, mediating the balance between algae and corals, and are often categorised into three functional groups based on adult morphology and feeding behaviour. We used stable isotope analysis (?13C, ?15N) to investigate size-related ontogenetic dietary changes in multiple species of parrotfish on coral reefs around Zanzibar. We compared signatures among species and functional groups (scrapers, excavators and browsers) as well as ontogenetic stages (immature, initial and terminal phase) within species. Stable isotope analysis suggests that ontogenetic dietary shifts occurred in seven of the nine species examined; larger individuals had enriched ?13C values, with no relationship between size and ?15N. The relationship between fish length and ?13C signature was maintained when species were categorised as scrapers and excavators, but was more pronounced for scrapers than excavators, indicating stronger ontogenetic changes. Isotopic mixing models classified the initial phase of both the most abundant excavator ( Chlorurus sordidus) as a scraper and the immature stage of the scraper Scarus ghobban (the largest species) as an excavator, indicating that diet relates to size rather than taxonomy. The results indicate that parrotfish may show similar intra-group changes in diet with length, but that their trophic ecology is more complex than suggested by morphology alone. Stable isotope analyses indicate that feeding ecology may differ among species within functional groups, and according to ontogenetic stage within a species.

Plass-Johnson, J. G.; McQuaid, C. D.; Hill, J. M.

2013-06-01

251

Temporal variability of nitrogen stable isotopes in primary uptake compartments in four streams differing in human impacts.  

PubMed

Understanding the variability of the natural abundance in nitrogen stable isotopes (expressed as ?(15)N) of primary uptake compartments (PUCs; e.g., epilithon or macrophytes) is important due to the multiple applications of stable isotopes in freshwater research and can give insights into environmental and anthropogenic factors controlling N dynamics in streams. While previous research has shown how ?(15)N of PUCs varies with ?(15)N of dissolved inorganic N (DIN) among streams, less is known about how ?(15)N of PUCs varies over time. Here, we examined monthly variation of ?(15)N of PUCs and of DIN species (nitrate and ammonium) over a year, and compared it among streams with contrasting human impacts and PUC types. Our results showed no evidence of isotopic seasonal patterns. Temporal variability in ?(15)N-PUCs increased with human impact, being the highest in the urban stream, probably influenced by the high variability of ?(15)N-DIN. Among compartments, in-stream PUCs characterized by fast turnover rates, such as filamentous algae, showed the highest temporal variability in ?(15)N values (from -3.6 to 23.2 ). Our study elucidates some of the environmental and biological controls of temporal variability of ?(15)N in streams, which should be taken into account when using stable isotopes as an ecological tool. PMID:24837817

Pastor, Ada; Riera, Joan Llus; Peipoch, Marc; Caas, Ldia; Ribot, Miquel; Gacia, Esperana; Mart, Eugnia; Sabater, Francesc

2014-06-17

252

Atmospheric Aerosol Investigation In Vilnius using Stable Carbon Isotopes  

NASA Astrophysics Data System (ADS)

The effects of aerosols on the atmosphere, climate, and public health are among the central topics in current environmental research. Spatially urban air pollution is a major public concern world-wide.In this study the results of experimental research are presented, the basis of which is the investigation of 13C/12C variations ?13C of stable carbon isotopes in total carbonaceous aerosols in Vilnius city, Lithuania. The main aim of the work is to identify the origin of carbonaceous aerosols. Two autumns and one spring sampling campaign were designed with the aim to determine the changes in the air caused by the beginning/end of the heating season. The experiment was performed during several sampling periods. The first period lasted from 26 November to 06 December 2010. The second was from 04 April to 16 May 2011. The third was from 12 to 29 October 2012. Atmospheric aerosols, according to their aerodynamic diameters, were collected with an eleven-stage impactor "MOUDI". The stages have 50% aerodynamic diameter cut-offs of 18.0, 10.0, 5.6, 3.2, 1.8, 1.0, 0.56, 0.32, 0.18, 0.1 and 0.056 ?m, for stages 1-11, respectively. The analysis proceeds essentially in two stages. In the first, MOUDI foils were analyzed with EA-IRMS (FlashEA 1112 coupled to ThermoFinnigan Delta Plus Advantage). Half of the foil was measured directly (TC ?13C values). The rest was heated in the oven (400 C) to remove organic part and measured EC+CC ?13C values (carbonates were not removed with acid). During the second stage of the analysis, corrections are made and OC ?13C values were calculated using isotopic balance equation: . As the main aim of the study was to identify the origin of incoming carbonaceous aerosols, air mass back trajectories were calculated using the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model.

Masalaite, Agne; Garbaras, Andrius; Remeikis, Vidmantas

2013-04-01

253

Stable Carbon Isotope Record in a Palau Sclerosponge  

NASA Astrophysics Data System (ADS)

The ratio of stable carbon isotopes (?13C) deposited in the calcium carbonate skeleton of marine sclerosponges appears to record the carbon isotopic composition of seawater mixed-layer dissolved inorganic carbon (?13CDIC). Thus the ?13C signature chronicled in sclerosponge skeletons offers a promising multi-century proxy record of seawater mixed-layer ?13CDIC throughout the tropics. Here, a high-resolution (0.1 mm) ?13C record for a 7.7 cm Acanthocheatetes wellsi sclerosponge from Palau (7N, 134W) is presented. At a published growth rate of 0.45 mm per year, this record spans ~s170 years beginning in July 2001 and going back to 1831. The ?13C values for a definitive 10-year A. wellsi record spanning 1989-1998 were similar to ?13C values here for the first 4.7 mm of the record providing supporting evidence for the growth rate. The sclerosponge ?13C shows a distinct Seuss Effect. At the time this abstract was submitted, the analysis of the first 16 mm of the sclerosponge revealed a significant decrease in ?13C with time [?13C = 0.02 (distance) + 2.64, r2 = 0.73, p < 0.0001, where time is marked by distance in millimeters from the growing edge] corresponding to a decrease in ?13C of 0.076 per decade. For comparison, published low-frequency measurements in Australian, New Caledonian and Jamaican sclerosponges have yielded decreases in ?13C of ~s0.05 to 0.08 per decade over the past 40 years. Preliminary interpretation of the data indicates that the amount of atmospheric CO2 contributing to the seawater ?13CDIC at Palau is intermediate to Australia and Jamaica. In addition, visual examination of the ?13C record reveals regular fluctuation in ?13C that may correspond to annual variability in ?13CDIC. This research presents the first century or longer sclerosponge ?13C record from the northwester equatorial Pacific.

Grottoli, A. G.

2002-12-01

254

The influence of authigenic clay formation on the mineralogy and stable isotopic record of lacustrine carbonates  

NASA Astrophysics Data System (ADS)

The mineralogical, compositional and stable isotopic variability of lacustrine carbonates are frequently used as proxies for ancient paleoenvironmental change in continental settings, under the assumption that precipitated carbonates reflect conditions and chemistry of ancient lake waters. In some saline and alkaline lake systems, however, authigenic clay minerals, forming at or near the sediment water interface, are a major sedimentary component. Often these clays are rich in Mg, influencing the geochemical budget of lake waters, and are therefore expected to influence the properties of contemporaneous authigenic carbonate precipitates (which may also contain Mg). This paper documents evidence for a systematic feedback between clay mineral and carbonate authigenesis through multiple precessionally driven, m-scale sedimentary cycles in lacustrine oil-shale deposits of the Eocene Green River Formation from the Uinta Basin (NE Utah). In the studied section, authigenic, Mg-rich, trioctahedral smectite content varies cyclically between 9 and 39 wt.%. The highest concentrations occur in oil-shales and calcareous mudstones deposited during high lake level intervals that favored sedimentary condensation, lengthening the time available for clay diagenesis and reducing dilution by other siliciclastic phases. An inverse relation between dolomite percentage of carbonate and trioctahedral smectite abundance suggests the Mg uptake during clay authigenesis provides a first order control on carbonate mineralogy that better explains carbonate mineralogical trends than the possible alternative controls of (1) variable Mg/Ca ratios in lake water and (2) degree of microbial activity in sediments. We also observe that cyclical change in carbonate mineralogy, believed to be induced by clay authigenesis, also causes isotopic covariation between ?13CPDB and ?18OPDB of bulk sediments because of differences in the equilibrium fractionation factors of dolomite and calcite (2 and 2.6%, respectively). This provides an alternative mechanism for the common pattern of isotopic covariation, which is typically attributed to the effect of simultaneous changes in water balance and biological activity on the carbon and oxygen isotopic composition of lake waters. These findings may help improve paleoenvironmental reconstructions based on lacustrine carbonate records by adding to the factors known to influence the mineralogical, compositional and stable isotopic signals recorded by lacustrine carbonates.

Bristow, Thomas F.; Kennedy, Martin J.; Morrison, Keith D.; Mrofka, David D.

2012-08-01

255

Evaluation of Stable Isotope Analysis as a Tool to Determine Nitrate Sources in Irish Groundwaters  

NASA Astrophysics Data System (ADS)

Natural abundance of stable isotope ratios of nitrogen (\\delta15N) and oxygen (\\delta18O) in NO3 were measured in a nitrate-vulnerable aquifer in eastern Ireland underlying an intensive agricultural area. The aim was to determine whether the dual stable isotope approach (\\delta15N and \\delta18O) could provide a more power tool than \\delta15N measurements alone for determining the source of groundwater nitrate. Forty-five private wells and boreholes representing a range of potential N sources (diffuse sources such as synthetic fertiliser spreading and/or farmyard effluents and/or septic tank effluents) were sampled on seven occasions between 2002 and 2004. Additionally, nitrate leachate samples were collected from the unsaturated zone under small-scale experiments simulating different agricultural practices. Nitrate was extracted from each water sample using an anion exchange resin technique (Silva et al., 2000), and \\delta15N and \\delta18O values were both measured by Continuous-Flow Isotopic Ratio Mass Spectrometry. The initial hypothesis was that, in a shallow gravel aquifer where nitrate leaching is important and fast, groundwater nitrates are likely to display the isotopic characteristics of their source (low \\delta15N and high \\delta18O for diffuse sources, compared to high \\delta15N and low \\delta18O for point sources). The first set of results indicates that the \\delta15N values only follow this trend, although the \\delta18O values suggest the occurrence of denitrification. The levelling of \\delta18O values may in fact be caused by the Mineralisation-Immobilisation Turnover processes (MIT) that have previously been found to occur in the unsaturated zone, incorporating new oxygen atoms during the remineralisation of the nitrate (Mengis et al., 2001). References Mengis, M.; Walther, U.; Bernasconi, S.M.; Wehrli, B. (2001) Limitations of using \\delta18O for the source identification of nitrate in agricultural soils. Environmental Science & Technology, 35, 1840-1844. Silva, S.R.; Kendall, C.; Wilkison, D.H.; Ziegler, A.C.; Chang, C.C.Y.; Avanzino, R.J. (2000) A new method for collection of nitrate from fresh water and the analysis of nitrogen and oxygen isotope ratios. Journal of Hydrology, 228, 22-36.

Minet, E.; Coxon, C.; Kalin, R.

2004-12-01

256

A stable carbon isotope and biological marker study of Polish bituminous coals and carbonaceous shales  

USGS Publications Warehouse

Biological marker and carbon isotopic compositions of coals and carbonaceous shales from the Upper Carboniferous strata of the Upper Silesian (USCB), Lower Silesian (LSCB), and Lublin (LCB) coal basins were determined to assess depositional conditions and sources of the organic matter. n-Alkane, sterane, and isoprenoid distribution, and carbon isotope ratios are consistent with an origin from higher plants. In some cases, pristane/phytane (Pr/Ph) ratios of carbonaceous shales (roof and floor shales) are < 1.0, while the associated coals have high ratios (??? 1.0). This suggests that reducing conditions prevailed during deposition of the shales, but a period of oxidizing conditions accompanied deposition of the coals. Steranes present in coal extracts are dominated by the 14??(H)17??(H)20R C29 stereoisomers, typical, but not conclusive, of higher plant origin. Carbonaceous shales exhibit a wider range of sterane composition, suggesting local, significant input of algal organic matter. Significant amounts of benzohopanes and gammacerane are present in some coals. Although benzohopanes are present at least in small amounts in samples from many different environments, they have been reported to occur most commonly in marine environments. The present study seems to provide the first example where benzohopanes have been reported in significant amounts in terrestrial organic matter. Gammacerane is abundant in rocks or sediments deposited in carbonate or highly saline marine environments. The finding of high gammacerane concentrations in the coals expands the depositional settings in which it has been observed and questions its utility as an independent indicator of hypersaline carbonate environments. Stable carbon isotope composition of coals, and type III kerogen in carbonaceous shales as well as correlation of stable carbon isotope composition of saturated and aromatic hydrocarbons in carbonaceous shales from both the USCB and the LSCB indicate terrigenous origin. Bitumens are always co-genetic with associated coals and kerogens. Isotopic data reveal that Sofer's genetic classification of oils is not applicable to organic matter in coals. ?? 2003 Elsevier B.V. All rights reserved.

Kotarba, M. J.; Clayton, J. L.

2003-01-01

257

Forensic Applications of Light-Element Stable Isotope Ratios of Ricinus communis Seeds and Ricin Preparations  

SciTech Connect

Seeds of the castor plant Ricinus communis, also known as castor beans, are of forensic interest because they are the source of the poison ricin. We have tested whether stable isotope ratios of castor seeds and ricin prepared by various methods can be used as a forensic signature. We collected over 300 castor seed samples from locations around the world and measured the C, N, O, and H stable isotope ratios of the whole seeds, oil, and three types of ricin preparations. Our results demonstrate that N isotope ratios can be used to correlate ricin prepared by any of these methods to source seeds. Further, stable isotope ratios distinguished >99% of crude and purified ricin protein samples in pair-wise comparison tests. Stable isotope ratios therefore constitute a valuable forensic signature for ricin preparations.

Kreuzer, Helen W.; West, Jason B.; Ehleringer, James

2013-01-01

258

Carbon and Sulfur Stable Isotope Records of the Early Paleogene  

NASA Astrophysics Data System (ADS)

Secular records of stable carbon isotopes and stable sulfur isotopes from marine sediment provide primary tools for understanding past changes in global biogeochemical cycling. Over the Cenozoic, the most pronounced changes in ?13C and ?34S records happened during the late Paleocene and Early Eocene. The cause of these variations remains the source of debate, in part because the ?13C and ?34S records are not linked very well in the time domain. The early Cenozoic ?34S record principally comes from analyses of barite extracted from DSDP Sites 366 and 577 (Paytan et al., Science, 1996). However, Site 366 has no ?13C record and poorly preserved microfossil assemblages, and Site 577 has a problematic stratigraphy because of misplaced datums, and unrecognized core gaps and core overlaps. Here we generate a ?13C record at Site 366, realign the stratigraphy at Site 577, and place both records on a current time scale for the early Paleogene (Option 1; Westerhold et al., P3, 2008). There is now very little play in the relative and absolute timing of ?13C and ?34S changes across the early Paleogene. Between about 62 and 58 Ma, the ?13C of carbonate increased while the ? 34S of barite decreased. A marked change occurred at about 58 Ma: form this time to about 52 Ma, the ?13C of carbonate decreased but the ? 34S of barite continued to decrease. At about 52 Ma and a few million years after, both ?13C and ? 34S increased. Thus, the records are coupled but in a complex manner, and the series of hyperthermals happened when both ?13C and ? 34S decreased together. No model to date explains these basic observations satisfactorily. For example, volcanism as a cause for the ?34C drop does not explain the initial 4 Myr rise in ?13C and apparent coeval removal of carbon from the ocean and atmosphere; storage and release of terrestrial organic carbon as a cause for the rise and fall in ?13C does not explain the drop or subsequent rise in ?34S. Clearly, however, the idea that methane build-up in marine sediment during the late Paleocene and its subsequent discharge over the early Eocene is wrong, at least as presented (Dickens, Clim. Past, 2011). This is because such storage and release must drive significant anaerobic oxidation of methane (AOM) and the formation of Fe sulfides, which if depleted in 34S relative to seawater, would cause a positive ?34S excursion. Indeed, seafloor methane cannot be a significant player in global biogeochemical cycling during the early Paleogene, unless one invokes an unconventional notion: AOM leads to burial of 34S-enriched Fe sulfides.

Dickens, G.; Backman, J.

2012-12-01

259

A guide for the laboratory information management system (LIMS) for light stable isotopes--Versions 7 and 8  

USGS Publications Warehouse

The reliability and accuracy of isotopic data can be improved by utilizing database software to (i) store information about samples, (ii) store the results of mass spectrometric isotope-ratio analyses of samples, (iii) calculate analytical results using standardized algorithms stored in a database, (iv) normalize stable isotopic data to international scales using isotopic reference materials, and (v) generate multi-sheet paper templates for convenient sample loading of automated mass-spectrometer sample preparation manifolds. Such a database program, the Laboratory Information Management System (LIMS) for Light Stable Isotopes, is presented herein. Major benefits of this system include (i) a dramatic improvement in quality assurance, (ii) an increase in laboratory efficiency, (iii) a reduction in workload due to the elimination or reduction of retyping of data by laboratory personnel, and (iv) a decrease in errors in data reported to sample submitters. Such a database provides a complete record of when and how often laboratory reference materials have been analyzed and provides a record of what correction factors have been used through time. It provides an audit trail for laboratories. LIMS for Light Stable Isotopes is available for both Microsoft Office 97 Professional and Microsoft Office 2000 Professional as versions 7 and 8, respectively. Both source code (mdb file) and precompiled executable files (mde) are available. Numerous improvements have been made for continuous flow isotopic analysis in this version (specifically 7.13 for Microsoft Access 97 and 8.13 for Microsoft Access 2000). It is much easier to import isotopic results from Finnigan ISODAT worksheets, even worksheets on which corrections for amount of sample (linearity corrections) have been added. The capability to determine blank corrections using isotope mass balance from analyses of elemental analyzer samples has been added. It is now possible to calculate and apply drift corrections to isotopic data based on the time of day of analysis. Whereas Finnigan ISODAT software is confined to using only a single peak for calculating delta values, LIMS now enables one to use the mean of two or more reference injections during a continuous flow analysis to calculate delta values. This is useful with Finnigan?s GasBench II online sample preparation system. Concentrations of carbon, nitrogen, and sulfur can be calculated based one or more isotopic reference materials analyzed with a group of samples. Both sample data and isotopic analysis data can now be exported to Excel files. A calculator for determining the amount of sample needed for isotopic analysis based on a previous amount of sample and continuous flow area is now an integral part of LIMS for Light Stable Isotopes. LIMS for Light Stable Isotopes can now assign an error code to Finnigan elemental analyzer analyses in which one of the electrometers has saturated due to analysis of too much sample material, giving rise to incorrect isotopic abundances. Information on downloading this report and downloading code and databases is provided at the Internet addresses: http://water.usgs.gov/software/geochemical.html or http://www.geogr.uni-jena.de/software/geochemical.html in the Eastern Hemisphere.

Coplen, Tyler B.

2000-01-01

260

Trophic ecology of mullets during their spring migration in a European saltmarsh: A stable isotope study  

NASA Astrophysics Data System (ADS)

Mullet populations are abundant in littoral waters throughout the world and play a significant role in organic matter fluxes. Mullets are opportunistic feeders: adults have frequently been shown to feed on primary producers (e.g. fresh or detrital plant material, microphytobenthos) but they may also feed on meiofauna. The population structure and stomach contents of mullets that colonize saltmarsh creeks in Aiguillon Bay (French Atlantic coast) were studied to determine if they use saltmarshes as a feeding ground in spring. Stable isotope analyses were carried out on mullets sampled to assess their diet during their spring migration. The mullet population was primarily composed of young-of-the-year (G0), 1 year-old (G1) of both Liza ramada and Liza aurata species and 3 year-old or older (G3+) L. ramada individuals. G0 and G3+ population densities increased during the spring period: catch per unit effort (CPUE) increased from 0.22 to 1.49 ind min -1 for the G0 age group; but stomach content analyses revealed that only G1 and G3+ feed in the saltmarsh. Isotopic signatures of G1 (spring: ? 13C: -14.8, ? 15N: 14.1) and G3+ mullets (spring: ? 13C: -16.9, ? 15N: 13.8) indicate that mullet growth is supported largely by primary consumers, such as benthic meiofauna or small macrofauna. Mullets are thus positioned at a much higher trophic level than true primary consumers.

Lebreton, Benoit; Richard, Pierre; Parlier, Emmanuel P.; Guillou, Gal; Blanchard, Grard F.

2011-03-01

261

Recent Advances in Stable Isotope Techniques for N2O Source Partitioning in Soils  

NASA Astrophysics Data System (ADS)

The use of 13C, 15N and 18O enables us to overcome uncertainties associated with soil C and N processes and to assess the links between species diversity and ecosystem function. Recent advances in stable isotope techniques enable determination of process rates, and are fundamental for examining interactions between C and N cycles. Here we will introduce the 15N-, 18O- and 13C-enrichment techniques we have developed to distinguish between different N2O-producing processes in situ in soils, presenting selected results, and will critically assess their potential, alone and in combination with molecular techniques, to help address key research questions for soil biogeochemistry and microbial ecology. We have developed 15N- 18O-enrichment techniques to distinguish between, and to quantify, N2O production during ammonia oxidation, nitrifier denitrification and denitrification. This provides a great advantage over natural abundance approaches as it enables quantification of N2O from each microbial source, which can be coupled with quantification of N2 production, and used to examine interactions between different processes and cycles. These approaches have also provided new insights into the N cycle and how it interacts with the C cycle. For example, we now know that ammonia oxidising bacteria significantly contribute to N2O emissions from soils, both via the traditionally accepted ammonia oxidation pathway, and also via denitrification (nitrifier denitrification) which can proceed even under aerobic conditions. We are also linking emissions from each source to diversity and activity of relevant microbial functional groups, for example through the development and application of a specific nirK primer for the nitrite reductase in ammonia oxidising bacteria. Recently, isotopomers have been proposed as an alternative for source partitioning N2O at natural abundance levels, and offers the potential to investigate N2O production from nitrate ammonification, and overcomes the need to apply 18O-H2O to determine nitrifier denitrification. However, this only provides an estimated, not a quantified, contribution, and further developments are required for quantification using isotope enrichment. Despite some limitations, such techniques become even more powerful when linked with other recent developments, such as nanoSIMS, gene expression and 13C-stable isotope probing of microbial RNA, and when linked to other disciplines. These may help address remaining questions such as: which microbes are producing N2O in soil, what is the influence of plants and mycorrhizal fungi on rhizosphere processes, and where is denitrification occurring in soil?

Baggs, E.; Mair, L.; Mahmood, S.

2007-12-01

262

Using stable isotope probing to obtain a targeted metatranscriptome of aerobic methanotrophs in lake sediment.  

PubMed

In this study, we demonstrate the possibility of obtaining a targeted metatranscriptome from a functional group of microorganisms using a stable isotope probing (SIP) approach. Methanotrophs in lake sediment were labelled using (13)CH4, and both labelled and unlabelled-RNA were isolated and sequenced by 454 pyrosequencing. The unlabelled metatranscriptome had a large diversity of bacterial, archaeal, eukaryotic and viral sequences as expected from a diverse sediment community. In contrast, the labelled-RNA metatranscriptome was dominated by methanotroph sequences, particularly from Methylococcaceae. Transcripts of the methane monooxygenase genes pmoCAB were the most abundant in this metatranscriptome, and the pathway of methane oxidation to CO2 could be traced, as well as many steps in the ribulose monophosphate pathway for carbon assimilation. A high abundance of mRNA transcripts for proteins related to motility was detected, suggesting an importance for methanotrophs in lake sediments. This combination of SIP and metatranscriptomics should be broadly applicable, and will enhance the detection and identification of mRNA from target organisms. PMID:24115627

Dumont, Marc G; Pommerenke, Bianca; Casper, Peter

2013-10-01

263

High frequency, realtime measurements of stable isotopes in liquid water  

NASA Astrophysics Data System (ADS)

We developed a method to measure in-situ the isotopic composition of liquid water with minimal supervision and, most important, with a temporal resolution of less than a minute. For this purpose a off-the-shelf microporous hydrophobic membrane contactor for under 200 was combined with an isotope laser spectrometer (Picarro). The contactor, originally designed for degassing liquids, was used with nitrogen as carrier gas in order to transform a small fraction of liquid water to water vapor. The generated water vapor was then analyzed continuously by the isotope laser spectrometer. To prove the membrane's applicability we determined the specific isotope fractionation factor for the phase change through the contactor's membrane for a common temperature range and with different waters of known isotopic compositions. This fractionation factor is then used to derive the liquid water isotope ratio from the measured water vapor isotope ratios and the measured temperature at the phase change. The system was compared for breakthrough curves of isotopically enriched water and the isotope values corresponded very well with those of liquid water samples taken simultaneously and analyzed with a conventional method (CRDS). The introduced method supersedes taking liquid samples and employs only relative cheap and readily available components. This makes it a relatively inexpensive, fast, user-friendly and easily reproducible method. It can be applied in both the field and laboratory wherever a water vapor isotope analyzer can be run and whenever real-time isotope data of liquid water are required at high temporal resolution with the same accuracy as collecting individual water samples.

Weiler, M.; Herbstritt, B.; Gralher, B.

2012-04-01

264

Measurement of the turnover of glycogen phosphorylase by GC/MS using stable isotope derivatives of pyridoxine (vitamin B6).  

PubMed

The majority of vitamin B6 in the body is in skeletal muscle, bound as the cofactor pyridoxal 5'-phosphate to one abundant protein, glycogen phosphorylase. Previous work has established that radiolabelled vitamin B6 can be used as a turnover label for glycogen phosphorylase. In this study, a stable isotope derivative of pyridoxine {dideuterated pyridoxine; 3-hydroxy-4-(hydroxymethyl) -5-[hydroxymethyl-2H2]-2-methylpyridine} ([2H2]PN) has been used as a metabolic tracer to study the kinetics of labelling of the body pools of vitamin B6 in mice. A non-invasive method was developed in which the isotope abundance of the urinary excretory product of vitamin B6 metabolism, 4-pyridoxic acid, was analysed by GC/MS. The change in isotope abundance of urinary 4-pyridoxic acid following administration of [2H2]PN reflects the kinetics of labelling of the body pools of vitamin B6, and yields, non-invasively, the rate of degradation of glycogen phosphorylase. PMID:8713093

Beynon, R J; Leyland, D M; Evershed, R P; Edwards, R H; Coburn, S P

1996-07-15

265

Measurement of the turnover of glycogen phosphorylase by GC/MS using stable isotope derivatives of pyridoxine (vitamin B6).  

PubMed Central

The majority of vitamin B6 in the body is in skeletal muscle, bound as the cofactor pyridoxal 5'-phosphate to one abundant protein, glycogen phosphorylase. Previous work has established that radiolabelled vitamin B6 can be used as a turnover label for glycogen phosphorylase. In this study, a stable isotope derivative of pyridoxine dideuterated pyridoxine; 3-hydroxy-4-(hydroxymethyl) -5-[hydroxymethyl-2H2]-2-methylpyridine ([2H2]PN) has been used as a metabolic tracer to study the kinetics of labelling of the body pools of vitamin B6 in mice. A non-invasive method was developed in which the isotope abundance of the urinary excretory product of vitamin B6 metabolism, 4-pyridoxic acid, was analysed by GC/MS. The change in isotope abundance of urinary 4-pyridoxic acid following administration of [2H2]PN reflects the kinetics of labelling of the body pools of vitamin B6, and yields, non-invasively, the rate of degradation of glycogen phosphorylase.

Beynon, R J; Leyland, D M; Evershed, R P; Edwards, R H; Coburn, S P

1996-01-01

266

A stable isotope aridity index for terrestrial environments  

Microsoft Academic Search

We use the oxygen isotopic composition of tooth enamel from multiple mammalian taxa across eastern Africa to present a proxy for aridity. Here we report tooth enamel 18O values of 14 species from 18 locations and classify them according to their isotopic sensitivity to environmental aridity. The species are placed into two groups, evaporation sensitive (ES) and evaporation insensitive (EI).

Naomi E. Levin; Thure E. Cerling; Benjamin H. Passey; John M. Harris; James R. Ehleringer

2006-01-01

267

Interpreting past climate from stable isotopes in continental organic matter  

NASA Astrophysics Data System (ADS)

The isotopic composition of fossil organic material from continental deposits contains myriad information about past environmental conditions. Much effort has been devoted to study of ?18O and O2H variations in organic matter, which depend strongly on isotopic effects occurring in the hydrologic cycle. Derivation of proxy temperature signals has been demonstrated in studies using ?2H data from plant cellulose extracted from fossil wood, packrat middens, and peat, because plant tissues preserve isotopic signals inherited from the temperature-dependent signature of local meteoric water. More complex deconvolution of oxygen and hydrogen isotope data from terrestrial plant cellulose has also been undertaken using correlative or mechanistic models (calibrated through comparison of modem meteorological and isotopic data) that implicitly or explicitly consider the effects of secondary isotopic alteration of plant waters during evapotranspiration. Such models have been applied with notable success to isotopic studies of wood cellulose, which has proven to be a valuable source of quantitative proxy climate data, especially in the continuous time-series records offered by tree-ring sequences. Promising results have also been obtained from isotopic study of oxygen in aquatic plant cellulose preserved in lake sediments, hydrogen in aquatic plant lipids, and oxygen and hydrogen in cellulose from peat deposits.

Edwards, Thomas W. D.

268

Hydrogen isotopic composition of NBS and IAEA stable isotope water reference samples  

Microsoft Academic Search

The hydrogen isotopic compositions of several isotope water reference samples have been determined on a cycloidal double-collecting isotope ratio mass spectrometer that can resolve HD + from the `contaminant' H 3 + ion beam.

Tyler B. Coplen; Robert N. Clayton

1973-01-01

269

Automated determination of silicon isotope natural abundance by the acid decomposition of cesium hexafluosilicate.  

PubMed

A procedure for the automated determination of isotopic abundances of silicon from biogenic and lithogenic particulate matter and from dissolved silicon in fresh or saltwaters is reported. Samples are purified using proven procedures through the reaction of Si with acidified ammonium molybdate, followed by precipitation with triethylamine and combustion of the precipitate to yield silicon dioxide. The silicon dioxide is converted to cesium hexafluosilicate by dissolution in hydrogen fluoride and the addition of cesium chloride. Isotopic analysis is accomplished by decomposing the cesium hexafluosilicate with concentrated sulfuric acid to generate silicon tetrafluoride gas. Silicon tetrafluoride is purified cryogenically and analyzed on a gas source isotope ratio mass spectrometer. Yields of silicon tetrafluoride are >99.5%. The procedure can be automated by modifying commercial inlet systems designed for carbonate analysis. The procedure is free of memory effects and isotopic biases. Reproducibility is +/-0.03-0.10 per thousand for a variety of natural and synthetic materials. PMID:16944891

Brzezinski, Mark A; Jones, Janice L; Beucher, Charlotte P; Demarest, Mark S; Berg, Howard L

2006-09-01

270

An automated method for the analysis of stable isotope labeling data in proteomics.  

PubMed

An algorithm is presented for the generation of a reliable peptide component peak table from liquid chromatography-mass spectrometry (LC-MS) and subsequent quantitative analysis of stable isotope coded peptide samples. The method uses chemical noise filtering, charge state fitting, and deisotoping toward improved analysis of complex peptide samples. Overlapping peptide signals in mass spectra were deconvoluted by correlation with modeled peptide isotopic peak profiles. Isotopic peak profiles for peptides were generated in silico from a protein database producing reference model distributions. Doublets of heavy and light labeled peak clusters were identified and compared to provide differential quantification of pairs of stable isotope coded peptides. Algorithms were evaluated using peptides from digests of a single protein and a seven-protein mixture that had been differentially coded with stable isotope labeling agents and mixed in known ratios. The experimental results correlated well with known mixing ratios. PMID:15922621

Zhang, Xiang; Hines, Wade; Adamec, Jiri; Asara, John M; Naylor, Stephen; Regnier, Fred E

2005-07-01

271

Priming effects of biochar elucidated using stable isotope techniques.  

NASA Astrophysics Data System (ADS)

Organic residues are routinely used in tropical agricultural systems; as mulches to reduce water losses and for their fertiliser value. The addition of high N content organic residues to soils has been promoted in tropical countries as a means to achieve sustainable intensification of tropical farming systems and increasing soil organic matter status on infertile low income farms. Improving the nutrient release from these materials could have positive feedback effects in terms of improved food security and increased organic matter return to the soil through improved crop yields. Unfortunately the fertiliser value of most organic residues is such that only 10 -20% of the available nitrogen in the residue is mineralised to plant available nitrogen and taken up by the plant in the first cropping year, dropping to less than 2% in the subsequent years; thus having marginal overall impact on crop yields. Improving the fertiliser benefit of residues by combining them with the biochar addition could lead to significant increases in crop yields, an immediately tangible benefit for farmers. The addition of charcoal in boreal forest systems has been shown to increase the rate of soil organic matter decomposition, suggesting there is a priming effect of a biochar analogue on organic matter decomposition. The priming effect is the increase in soil organic matter (SOM) decomposition rate after the addition of fresh organic matter or other compounds to soil. The implication is that is biochar if addition leads to the loss of native SOM it negates the carbon benefit of adding biochar to soil. However there could also be potential benefits of priming effects of biochar under specific circumstances, for example if biochar addition leads to the priming of freshly added organic matter breakdown it may in turn improve nutrient synchronisation and overall nutrient use efficiency. We conducted a series of experiments conducted in Kenya and Austria using stable isotope tools to look at the priming effects of biochar on the carbon and nitrogen turnover of organic residues added to soils. I will present the finding of these investigations and discuss their implications. Please fill in your abstract text.

Hood-Nowotny, R.; Vanlauwe, B.

2012-04-01

272

Use of Stable Isotopes in the Study of Human Cholesterol Metabolism.  

National Technical Information Service (NTIS)

An experimental procedure based on the use of stable isotope spiked molecules of cholesterol, allows the measurement in faecal cholesterol of the relative parts coming from the plasma by transfer (deuterium spiked molecules), from the non absorbed aliment...

H. Virelizier R. Hagemann J. Ferezou F. Chevallier

1979-01-01

273

Tracking Estuary Habitat use by Young American Shad Using Stable Isotopes  

EPA Science Inventory

We developed and evaluated a stable isotope turnover model to estimate the probable risidence time of young-of-year (YOY) American shad (Alosa sapidissima), an anadromous clupeid, in various estuarine habitats....

274

USE OF FATTY ACID STABLE CARBON ISOTOPE RATIO TO INDICATE MICROBIAL CARBON SOURCE IN TROPICAL SOILS  

EPA Science Inventory

We use measurements of the concentration and stable carbon isotope ratio of individual microbial phospholipid fatty acids (PLFAs) in soils as indicators of live microbial biomass levels, broad microbial community structure, and microbial carbon source. For studies of soil o...

275

Stable Isotopes of Authigenic Minerals in Variably-Saturated Fractured Tuff.  

National Technical Information Service (NTIS)

Identifying stable isotope variation and mineralogical changes in fractured rock may help establish the history of climatic and geomorphological processes that might affect the isolation properties of a waste repository site. The study examines the use of...

D. S. Weber D. D. Evans

1988-01-01

276

Continuous in situ measurements of stable isotopes in liquid water  

NASA Astrophysics Data System (ADS)

We developed a method to measure in situ the isotopic composition of liquid water with minimal supervision and, most important, with a temporal resolution of less than a minute. For this purpose a microporous hydrophobic membrane contactor (Membrana) was combined with an isotope laser spectrometer (Picarro). The contactor, originally designed for degassing liquids, was used with N2 as a carrier gas in order to transform a small fraction of liquid water to water vapor. The generated water vapor was then analyzed continuously by the Picarro analyzer. To prove the membrane's applicability, we determined the specific isotope fractionation factor for the phase change through the contactor's membrane across an extended temperature range (8C-21C) and with different waters of known isotopic compositions. This fractionation factor is needed to subsequently derive the liquid water isotope ratio from the measured water vapor isotope ratios. The system was tested with a soil column experiment, where the isotope values derived with the new method corresponded well (R2 = 0.998 for ?18O and R2 = 0.997 for ?2H) with those of liquid water samples taken simultaneously and analyzed with a conventional method (cavity ring-down spectroscopy). The new method supersedes taking liquid samples and employs only relatively cheap and readily available components. This makes it a relatively inexpensive, fast, user-friendly, and easily reproducible method. It can be applied in both the field and laboratory wherever a water vapor isotope analyzer can be run and whenever real-time isotope data of liquid water are required at high temporal resolution.

Herbstritt, Barbara; Gralher, Benjamin; Weiler, Markus

2012-03-01

277

Mid-Holocene stable isotope record of corals from the northern Red Sea  

Microsoft Academic Search

We present a study based on X-ray chronologies and the stable isotopic composition of fossil Porites spp. corals from the northern Gulf of Aqaba (Red Sea) covering the mid-Holocene period from 5750 to 4450 14C years BP (before present). The stable oxygen and carbon isotopic compositions of five specimens reveal regular annual periodicities.\\u000a Compared with modern Porites spp. from the

Y. A. Moustafa; J. Ptzold; Y. Loya; G. Wefer

2000-01-01

278

Reconstruction of past climates from stable isotope records of palaeo-precipitation preserved in continental archives  

Microsoft Academic Search

The potential of stable isotope ratios (2H\\/'H and 180\\/!60) of water as a modern tool for palaeoclimatic reconstructions on continents is reviewed. Examples of stable isotope records of palaeo-precip itation preserved in various continental archives (polar ice sheets, mid- and low latitude glaciers, lacustrine deposits, groundwater) are presented, and the methodology of their interpretation in terms of climatic changes is

K. ROZANSKI; S. J. JOHNSEN; U. SCHOTTERER; L. G. THOMPSON

1998-01-01

279

Terrestrial input to estuarine bivalves as measured by multiple stable isotopes tracers  

Microsoft Academic Search

Stable isotope ratios of carbon, nitrogen, hydrogen and oxygen were used here, to trace the extent of terrestrial input to estuarine bivalves (Mytilus edulis) during the summer of 1984 and 1985. Salinity records indicate a stronger river influence in 1985 compared to 1984.\\u000aFatty acids ratios (C24\\/C16, C24\\/C14) are intercalibrated with stable isotopes of carbon (?C) and nitrogen (??N) to

Caroline LeBlanc

1989-01-01

280

A practical recipe for stable isotope labeling by amino acids in cell culture (SILAC)  

Microsoft Academic Search

Stable isotope labeling by amino acids in cell culture (SILAC) is a simple, robust, yet powerful approach in mass spectrometry (MS)-based quantitative proteomics. SILAC labels cellular proteomes through normal metabolic processes, incorporating non-radioactive, stable isotope-containing amino acids in newly synthesized proteins. Growth medium is prepared where natural (''light'') amino acids are replaced by ''heavy'' SILAC amino acids. Cells grown in

Shao-En Ong; Matthias Mann

2006-01-01

281

A practical recipe for stable isotope labeling by amino acids in cell culture (SILAC)  

Microsoft Academic Search

Stable isotope labeling by amino acids in cell culture (SILAC) is a simple, robust, yet powerful approach in mass spectrometry (MS)-based quantitative proteomics. SILAC labels cellular proteomes through normal metabolic processes, incorporating non-radioactive, stable isotope-containing amino acids in newly synthesized proteins. Growth medium is prepared where natural (light) amino acids are replaced by heavy SILAC amino acids. Cells grown in

Matthias Mann; Shao-En Ong

2007-01-01

282

Observation and modelling of stable isotopes in precipitation for midlatitude weather systems in Melbourne, Australia  

NASA Astrophysics Data System (ADS)

The application of stable water isotopes as tracers of moisture throughout the hydrological cycle is often hindered by the relatively coarse temporal and spatial resolution of observational data. Intensive observation periods (IOPs) of isotopes in precipitation have been valuable in this regard enabling the quantification of the effects of vapour recycling, convection, cloud top height and droplet reevaporation (Dansgaard, 1953; Miyake et al., 1968; Gedzelman and Lawrence, 1982; 1990; Pionke and DeWalle, 1992; Risi et al., 2008; 2009) and have been used as a basis to develop isotope models of varying complexity (Lee and Fung, 2008; Bony et al., 2008). This study took a unified approach combining observation and modelling of stable isotopes in precipitation in an investigation of three key circulation types that typically bring rainfall to southeastern Australia. The observational component of this study involved the establishment of the Melbourne University Network of Isotopes in Precipitation (MUNIP). MUNIP was devised to sample rainwater simultaneously at a number of collection sites across greater Melbourne to record the spatial and temporal isotopic variability of precipitation during the passage of particular events. Samples were collected at half-hourly intervals for three specific rain events referred to as (1) mixed-frontal, (2) convective, and (3) stratiform. It was found that the isotopic content for each event varied over both high and low frequencies due to influences from local changes in rain intensity and large scale rainout respectively. Of particular note was a positive relationship between deuterium excess and rainfall amount under convective conditions. This association was less well defined for stratiform rainfall. As a supplement to the data coverage of the observations, the events were simulated using a version of NCAR CAM3 running with an isotope hydrology scheme. This was done by periodically nudging the model dynamics with data from the NCEP Reanalysis (Noone, 2006). Results from the simulations showed that the model represented well the large scale evolution of vapour profiles of deuterium excess and 18O for the mixed-frontal and stratiform events. Reconstruction of air mass trajectories provided further detail of the evolution and structure of the vapour profiles revealing a convergence of air masses from different source regions for the mixed-frontal event. By combining observations and modelling in this way, much detail of the structure and isotope moisture history of the observed events was provided that would be unavailable from the sampling of precipitation alone. References Bony, S., C. Risi, and F. Vimeux (2008), Influence of convective processes on the isotopic composition (?18O and ?D) of precipitation and water vapor in the tropics: 1. Radiative-convective equilibrium and Tropical Ocean-Global Atmosphere-Coupled Ocean-Atmosphere Response (TOGA-COARE) simulations, J. Geophys. Res., 113, D19305, doi:10.1029/2008JD009942. Dansgaard, W. (1953), The abundance of 18O in atmospheric water and water vapor. Tellus, 5, 461-469. Gedzelman, S. D., and J. R. Lawrence (1982), The isotopic composition of cyclonic precipitation. J. App. Met., 21, 1385-1404. Gedzelman, S. D., and J. R. Lawrence (1990), The isotopic composition of precipitation from two extratropical cyclones, Mon. Weather Rev., 118 , 495-509. Lee, J., and I. Fung (2008), 'Amount effect' of water isotopes and quantitative analysis of post-condensation processes, Hydrol. Process., 22, 1-8. Miyake, Y., O. Matsubaya, and C. Nishihara (1968), An isotopic study on meteoric precipitation, Pap. Meteorol. Geophys., 19, 243-266. Noone, D. (2006), Isotopic composition of water vapor modeled by constraining global climate simulations with reanalyses, in Research activities in atmospheric and oceanic modeling, J. Ct (ed.), Report No. 36, WMO/TD-No. 1347, p. 2.37-2.38. Pionke, H. B., and D. R. DeWalle (1992), Intra- and inter-storm 18O trends for selected rainstorms in Pennsylvania. J. Hydrol., 138, 131-143. Risi, C., S. Bony, and F. Vimeux (20

Barras, Vaughan; Simmonds, Ian

2010-05-01

283

Monsoonal moisture sources revealed using temperature, precipitation, and precipitation stable isotope timeseries  

Microsoft Academic Search

Results of analyses using timeseries of mean temperature, precipitation amount, and stable isotopes from precipitation from July-August in Tucson, Arizona, have revealed atmospheric circulation patterns related to the North American Monsoon in the U.S. Southwest. The isotope timeseries and Tucson air temperatures and precipitation amount are significantly correlated. The temperature and isotope timeseries also correlate significantly with regional and extra-regional

William E. Wright; A. Long; A. C. Comrie; S. W. Leavitt; T. Cavazos; C. Eastoe

2001-01-01

284

Stable Isotopic Profiling of Intermediary Metabolic Flux in Developing and Adult Stage Caenorhabditis elegans  

PubMed Central

Stable isotopic profiling has long permitted sensitive investigations of the metabolic consequences of genetic mutations and/or pharmacologic therapies in cellular and mammalian models. Here, we describe detailed methods to perform stable isotopic profiling of intermediary metabolism and metabolic flux in the nematode, Caenorhabditis elegans. Methods are described for profiling whole worm free amino acids, labeled carbon dioxide, labeled organic acids, and labeled amino acids in animals exposed to stable isotopes either from early development on nematode growth media agar plates or beginning as young adults while exposed to various pharmacologic treatments in liquid culture. Free amino acids are quantified by high performance liquid chromatography (HPLC) in whole worm aliquots extracted in 4% perchloric acid. Universally labeled 13C-glucose or 1,6-13C2-glucose is utilized as the stable isotopic precursor whose labeled carbon is traced by mass spectrometry in carbon dioxide (both atmospheric and dissolved) as well as in metabolites indicative of flux through glycolysis, pyruvate metabolism, and the tricarboxylic acid cycle. Representative results are included to demonstrate effects of isotope exposure time, various bacterial clearing protocols, and alternative worm disruption methods in wild-type nematodes, as well as the relative extent of isotopic incorporation in mitochondrial complex III mutant worms (isp-1(qm150)) relative to wild-type worms. Application of stable isotopic profiling in living nematodes provides a novel capacity to investigate at the whole animal level real-time metabolic alterations that are caused by individual genetic disorders and/or pharmacologic therapies.

Falk, Marni J.; Daikhin, Evgueni; Nissim, Ilana; Yudkoff, Marc

2011-01-01

285

Hadrosaurid migration: inferences based on stable isotope comparisons among Late Cretaceous dinosaur localities  

Microsoft Academic Search

Stable carbon and oxygen isotope ratios were measured for carbonate in samples of had- rosaurid tooth enamel and dentine, and gar scale ganoine and dentine from five geologically ''con- temporaneous'' (two-million-year resolution) and geographically distant late Campanian forma- tions (Two Medicine, Dinosaur Park, Judith River, Kaiparowits, and Fruitland) in the Western In- terior Basin. In all cases, isotopic offsets were

Raymond Rogers; Henry C. Fricke; Terry A. Gates

2009-01-01

286

Influence of Drinking Water and Diet on the Stable-Hydrogen Isotope Ratios of Animal Tissues  

Microsoft Academic Search

Despite considerable interest in using stable-hydrogen isotope ratio (delta D) measurements in ecological research, it was previously unknown whether hydrogen derived from drinking water, in addition to that derived from diet, contributed to the nonexchangeable hydrogen in animal tissues. We raised four experimental groups of quail (Coturnix coturnix japonica) from hatch on two isotopically distinct diets (mean nonexchangeable delta D:

Keith A. Hobson; Lisa Atwell; Leonard I. Wassenaar

1999-01-01

287

Integration of Stable Isotope and other Mass Spectral Data for Microbial Forensics  

Microsoft Academic Search

The nascent field of microbial forensics requires the development of diverse signatures as indicators of various aspects of the production environment of microorganisms. We have characterized isotopic relationships between Bacillus subtilis ATCC 6051 spores and their growth environment, using as a database the carbon, nitrogen, oxygen and hydrogen stable isotope ratios of a total of 247 separate cultures of spores

H. W. Kreuzer-Martin; K. H. Jarman

2008-01-01

288

Experimental Abiotic Synthesis and Stable Isotope Values of Gaseous Hydrocarbons and the Implications for Identifying Biosignatures  

Microsoft Academic Search

While geochemical indicators or 'biosignatures', such as stable carbon and hydrogen isotope values, of biogenic hydrocarbons have been identified, less is known about unambiguous abiogenic hydrocarbons. Traditionally, hydrocarbons that are depleted in carbon-13 are considered to be of biogenic origin, because many biological enzymatic reactions are known to preferentially incorporate the lighter carbon isotope. In this study, laboratory experiments were

P. L. Morrill; D. S. Weinberger; B. Sherwood Lollar; M. L. Fogel; G. D. Cody

2006-01-01

289

Modelling of stable isotope fractionation by methane oxidation and diffusion in landfill cover soils  

Microsoft Academic Search

A technique to measure biological methane oxidation in landfill cover soils that is gaining increased interest is the measurement of stable isotope fractionation in the methane. Usually to quantify methane oxidation, only fractionation by oxidation is taken into account. Recently it was shown that neglecting the isotope fractionation by diffusion results in underestimation of the methane oxidation. In this study

Koenraad Mahieu; Alex De Visscher; Peter A. Vanrolleghem; Oswald Van Cleemput

290

Modelling of stable isotope fractionation by methane oxidation and diffusion in landfill cover soils  

Microsoft Academic Search

A technique to measure biological methane oxidation in landfill cover soils that is gaining increased interest is the measurement of stable isotope fractionation in the methane. Usually to quantify methane oxidation, only fractionation by oxidation is taken into account. Recently it was shown that neglecting the isotope fractionation by diffusion results in underestimation of the methane oxidation. In this study

Koenraad Mahieu; Alex De Visscher; Peter A. Vanrolleghem; Oswald Van Cleemput

2008-01-01

291

Intramolecular distribution of stable nitrogen and oxygen isotopes of nitrous oxide emitted during coal combustion  

Microsoft Academic Search

The intramolecular distribution of stable isotopes in nitrous oxide that is emitted during coal combustion was analyzed using an isotopic ratio mass spectrometer equipped with a modified ion collector system (IRMS). The coal was combusted in a test furnace fitted with a single burner and the flue gases were collected at the furnace exit following removal of SOx, NOx, and

Mitsuteru Ogawa; Naohiro Yoshida

2005-01-01

292

Plasma separation process facility for large-scale stable isotope production  

Microsoft Academic Search

A facility for large-scale separation of stable isotopes using the plasma separation process (PSP) is under development at the Oak Ridge National Laboratory. The PSP is capable of separating isotopes at a large throughput rate with medium purity product and at relatively low cost. The PSP has a number of convenient features that make it an attractive technology for general

T. S. Bigelow; E. D. Collins; J. G. Tracy

1997-01-01

293

More than who eats who: Discerning ecological processes from stable isotopes data  

EPA Science Inventory

Stable isotope analyses of biota are now commonly used to discern trophic pathways between consumers and their foods. However, those same isotope data also hold information about processes that influence the physicochemical setting of food webs as well as biological processes ope...

294

Alaska Peninsula Stable Isotope and Radioisotope Chemistry: A Study in Temporal and Adaptive Diversity  

Microsoft Academic Search

Purified bone collagen from a small suite of human remains recovered at three sites on the Alaska Peninsula (Port Moller, Brooks River, and Mink Island) were analyzed for stable carbon and nitrogen isotope chemistry and were accelerator radiocarbon dated. Because samples sizes were small and faunal isotope chemistry lacking, results should be considered preliminary. However, these data indicate that each

Joan Brenner Coltrain

2010-01-01

295

Origin of petroporphyrins. 2. Evidence from stable carbon isotopes.  

PubMed

Compared with the carbon-13 isotopic composition of the ubiquitous C32DPEP (DPEP, deoxophylloerythroetioporphyrin) the heavy but equivalent carbon-13 isotopic composition for the porphyrin structures 15(2)-methyl-15,17-ethano-17-nor-H-C30DPEP and 15,17-butano-, 13,15-ethano-13(2),17-propano-, and 13(1)-methyl-13,15-ethano-13(2),17-propanoporphyrin suggests a common precursor, presumably chlorophyll c, for these petroporphyrins isolated from the marine Julia Creek oil shale and the lacustrine Condor oil shale. Similarly, the heavy but variable carbon-13 isotopic composition of 7-nor-H-C31DPEP compared with C32DPEP is consistent with an origin from both chlorophyll b and chlorophyll c3. The equivalent carbon-13 isotopic composition for 13(2)-methyl-C33DPEP compared with C32DPEP suggests a common origin resulting from a weighted average of chlorophyll inputs. PMID:11538479

Boreham, C J; Fookes, C J; Popp, B N; Hayes, J M

1990-01-01

296

Origin of petroporphyrins. 2. Evidence from stable carbon isotopes  

NASA Technical Reports Server (NTRS)

Compared with the carbon-13 isotopic composition of the ubiquitous C32DPEP (DPEP, deoxophylloerythroetioporphyrin) the heavy but equivalent carbon-13 isotopic composition for the porphyrin structures 15(2)-methyl-15,17-ethano-17-nor-H-C30DPEP and 15,17-butano-, 13,15-ethano-13(2),17-propano-, and 13(1)-methyl-13,15-ethano-13(2),17-propanoporphyrin suggests a common precursor, presumably chlorophyll c, for these petroporphyrins isolated from the marine Julia Creek oil shale and the lacustrine Condor oil shale. Similarly, the heavy but variable carbon-13 isotopic composition of 7-nor-H-C31DPEP compared with C32DPEP is consistent with an origin from both chlorophyll b and chlorophyll c3. The equivalent carbon-13 isotopic composition for 13(2)-methyl-C33DPEP compared with C32DPEP suggests a common origin resulting from a weighted average of chlorophyll inputs.

Boreham, C. J.; Fookes, C. J.; Popp, B. N.; Hayes, J. M.

1990-01-01

297

Stable-isotope geochronology of the Australian regolith  

SciTech Connect

Australian regolith profiles can be assigned to one of three post-Palaeozoic age groups on the basis of the oxygen-isotope composition of authigenic clay minerals developed in the profile. Systematic variations in the isotopic composition of meteoric waters, and therefore of the authigenic regolith minerals that formed in equilibrium with them, are a result of the continent's drift from high to low latitudes and changes in global climate. The hydrogen-isotope composition of the clays range from -115 to -50{per thousand}; however, it is inferred that the majority of clays have undergone some post-formational hydrogen-isotope exchange which renders their {delta}D composition unsuitable for dating purposes.

Bird, M.I.; Chivas, A.R. (Australian National Univ., Canberra (Australia))

1989-12-01

298

Zinc stable isotopes in seafloor hydrothermal vent fluids and chimneys  

NASA Astrophysics Data System (ADS)

Many of the heaviest and lightest natural zinc (Zn) isotope ratios have been discovered in hydrothermal ore deposits. However, the processes responsible for fractionating Zn isotopes in hydrothermal systems are poorly understood. In order to better assess the total range of Zn isotopes in hydrothermal systems and to understand the factors which are responsible for this isotopic fractionation, we have measured Zn isotopes in seafloor hydrothermal fluids from numerous vents at 9-10N and 21N on the East Pacific Rise (EPR), the TAG hydrothermal field on the Mid-Atlantic Ridge, and in the Guaymas Basin. Fluid ?66Zn values measured at these sites range from + 0.00 to + 1.04. Of the many physical and chemical parameters examined, only temperature was found to correlate with fluid ?66Zn values. Lower temperature fluids (< 250 C) had both heavier and more variable ?66Zn values compared to higher temperature fluids from the same hydrothermal fields. We suggest that subsurface cooling of hydrothermal fluids leads to precipitation of isotopically light sphalerite (Zn sulfide), and that this process is a primary cause of Zn isotope variation in hydrothermal fluids. Thermodynamic calculations carried out to determine saturation state of sphalerite in the vent fluids support this hypothesis with isotopically heaviest Zn found in fluids that were calculated to be saturated with respect to sphalerite. We have also measured Zn isotopes in chimney sulfides recovered from a high-temperature (383 C) and a low-temperature (203 C) vent at 9-10N on the EPR and, in both cases, found that the ?66Zn of chimney minerals was lighter or similar to the fluid ?66Zn. The first measurements of Zn isotopes in hydrothermal fluids have revealed large variations in hydrothermal fluid ?66Zn, and suggest that subsurface Zn sulfide precipitation is a primary factor in causing variations in fluid ?66Zn. By understanding how chemical processes that occur beneath the seafloor affect hydrothermal fluid ?66Zn, Zn isotopes may be used as a tracer for studying hydrothermal processes.

John, Seth G.; Rouxel, Olivier J.; Craddock, Paul R.; Engwall, Alison M.; Boyle, Edward A.

2008-05-01

299

Stable carbon and nitrogen isotope enrichment in primate tissues  

Microsoft Academic Search

Isotopic studies of wild primates have used a wide range of tissues to infer diet and model the foraging ecologies of extinct\\u000a species. The use of mismatched tissues for such comparisons can be problematic because differences in amino acid compositions\\u000a can lead to small isotopic differences between tissues. Additionally, physiological and dietary differences among primate\\u000a species could lead to variable

Brooke E. Crowley; Melinda L. Carter; Sarah M. Karpanty; Adrienne L. Zihlman; Paul L. Koch; Nathaniel J. Dominy

2010-01-01

300

Silver isotope variations in chondrites: Volatile depletion and the initial 107Pd abundance of the solar system  

NASA Astrophysics Data System (ADS)

The extinct radionuclide 107Pd decays to 107Ag (half-life of 6.5 Ma) and is an early solar system chronometer with outstanding potential to study volatile depletion in the early solar system. Here, a comprehensive Ag isotope study of carbonaceous and ordinary chondrites is presented. Carbonaceous chondrites show limited variations ( ?107Ag = -2.1 to +0.8) in Ag isotopic composition that correlate with the Pd/Ag ratios. Assuming a strictly radiogenic origin of these variations, a new initial 107Pd/ 108Pd of 5.9 (2.2) 10 -5 for the solar system can be deduced. Comparing the Pd-Ag and Mn-Cr data for carbonaceous chondrites suggests that Mn-Cr and Pd-Ag fractionation took place close to the time of calcium-aluminium-rich inclusion (CAI) and chondrule formation 4568 Ma ago. Using the new value for the initial 107Pd abundance, the revised ages for the iron-rich meteorites Gibeon (IVA, 8.5 +3.2/-4.6 Ma), Grant (IIIAB, 13.0 +3.5/-4.9 Ma) and Canyon Diablo (IA, 19.5 +24.1/-10.4 Ma) are consistent with cooling rates and the closure temperature of the Pd-Ag system. In contrast to carbonaceous chondrites, ordinary chondrites show large stable isotope fractionation of order of 1 permil for 107Ag/ 109Ag. This indicates that different mechanisms of volatile depletion were active in carbonaceous and ordinary chondrites. Nebular processes and accretion, as experienced by carbonaceous chondrites, did not led to significant Ag isotope fractionation, while the significant Ag isotope variations in ordinary chondrites are most likely inflicted by open system parent body metamorphism.

Schnbchler, M.; Carlson, R. W.; Horan, M. F.; Mock, T. D.; Hauri, E. H.

2008-11-01

301

B-HIVE: Beeswax hydrogen isotopes as validation of environment. Part I: Bulk honey and honeycomb stable isotope analysis  

Microsoft Academic Search

Stable isotope analysis is an established method for detecting honey adulteration. We extend its application to include honey and honeycomb region-of-origin assignment using hydrogen (?2H) and oxygen (?18O) isotopes. We observed that liquid honey ?2H and ?18O values had the potential to change because of water absorption and H atom exchange between sugars and water vapour. This suggested that liquid

Lesley A. Chesson; Brett J. Tipple; Brad R. Erkkila; Thure E. Cerling; James R. Ehleringer

2011-01-01

302

Use of stable nitrogen isotope fractionation to estimate denitrification in small constructed wetlands treating agricultural runoff.  

PubMed

Constructed wetlands (CWs) in the agricultural landscape reduce non-point source pollution through removal of nutrients and particles. The objective of this study was to evaluate if measurements of natural abundance of (15)NO(3)(-) can be used to determine the fate of NO(3)(-) in different types of small CWs treating agricultural runoff. Nitrogen removal was studied in wetland trenches filled with different filter materials (T1--sand and gravel; T3--mixture of peat, shell sand and light-weight aggregates; T8--barley straw) and a trench formed as a shallow pond (T4). The removal was highest during summer and lowest during autumn and winter. Trench T8 had the highest N removal during summer. Measurements of the natural abundance of (15)N in NO(3)(-) showed that denitrification was not significant during autumn/winter, while it was present in all trenches during summer, but only important for nitrogen removal in trench T8. The (15)N enrichment factors of NO(3)(-) in this study ranged from -2.5 to -5.9 per thousand (T3 and T8, summer), thus smaller than enrichment factors found in laboratory tests of isotope discrimination in denitrification, but similar to factors found for denitrification in groundwater and a large CW. The low enrichment factors compared to laboratory studies was attributed to assimilation in plants/microbes as well as diffusion effect. Based on a modified version of the method presented by Lund et al. [Lund LJ, Horne AJ, Williams AE, Estimating denitrification in a large constructed wetland using stable nitrogen isotope ratios. Ecol Engineer 2000; 14: 67-76], denitrification and assimilation were estimated to account for 53 to 99 and 1 to 47%, respectively, of the total N removal during summer. This method is, however, based on a number of assumptions, and there is thus a need for a better knowledge of the effect of plant uptake, microbial assimilation as well as nitrification on N isotopic fractionation before this method can be used to evaluate the contribution of dinitrification in CWs. PMID:18086487

Svik, Anne Kristine; Mrkved, Pl Tore

2008-03-15

303

Stable-carbon isotope variability in tree foliage and wood. [Iunipeus; Pinus edulis  

SciTech Connect

This study documents variation of stable-carbon isotope ratios (/sup 13/C//sup 12/C) in trees of genera Juniperus and Pinus under field conditions. Results are from cellulose analysis on leaves, twigs, and wood from a number of localities in the southwestern US. Substantial variability, typically 1-3%, exists among leaves, within wood (radially, vertically, circumferentially), and between individuals at a site. These results may help guide sampling in tracer-type studies with stable-carbon isotope ratios and aid in the interpretation of isotopic results from such studies.

Leavitt, S.W.; Long, A.

1986-08-01

304

Stable Isotope Mixing Models as a Tool for Tracking Sources of Water and Water Pollutants  

EPA Science Inventory

One goal of monitoring pollutants is to be able to trace the pollutant to its source. Here we review how mixing models using stable isotope information on water and water pollutants can help accomplish this goal. A number of elements exist in multiple stable (non-radioactive) i...

305

A Test of Carbon and Oxygen Stable Isotope Ratio Process Models in Tree Rings.  

NASA Astrophysics Data System (ADS)

Stable isotopes ratios of carbon and oxygen in tree ring cellulose have been used to infer environmental change. Process-based models have been developed to clarify the potential of historic tree ring records for meaningful paleoclimatic reconstructions. However, isotopic variation can be influenced by multiple environmental factors making simplistic interpretations problematic. Recently, the dual isotope approach, where the variation in one stable isotope ratio (e.g. oxygen) is used to constrain the interpretation of variation in another (e.g. carbon), has been shown to have the potential to de-convolute isotopic analysis. However, this approach requires further testing to determine its applicability for paleo-reconstructions using tree-ring time series. We present a study where the information needed to parameterize mechanistic models for both carbon and oxygen stable isotope ratios were collected in controlled environment chambers for two species (Pinus radiata and Eucalyptus globulus). The seedlings were exposed to treatments designed to modify leaf temperature, transpiration rates, stomatal conductance and photosynthetic capacity. Both species were grown for over 100 days under two humidity regimes that differed by 20%. Stomatal conductance was significantly different between species and for seedlings under drought conditions but not between other treatments or humidity regimes. The treatments produced large differences in transpiration rate and photosynthesis. Treatments that effected photosynthetic rates but not stomatal conductance influenced carbon isotope discrimination more than those that influenced primarily conductance. The various treatments produced a range in oxygen isotope ratios of 7 . Process models predicted greater oxygen isotope enrichment in tree ring cellulose than observed. The oxygen isotope ratios of bulk leaf water were reasonably well predicted by current steady-state models. However, the fractional difference between models that predict bulk leaf water versus the site of evaporation did not increase with transpiration rates. In conclusion, although the dual isotope approach may better constrain interpretation of isotopic variation, more work is required before its predictive power can be applied to tree-ring archives.

Roden, J. S.; Farquhar, G. D.

2008-12-01

306

Tropylium, chlorine isotopic abundances, monomeric metaphosphate anion, and conestoga wagon theory  

Microsoft Academic Search

As I look back over a career in mass spectrometry, three high points stand out especially prominently. These are associated\\u000a with (1) the tropylium model for the CuH7+ ion in the mass spectra of toluene and other alkylbenzenes, (2) revision of the previously accepted value for the natural\\u000a abundance of the chlorine isotopes, and (3) the first direct observation of

Seymour Meyerson

1993-01-01

307

Feathers as a means of monitoring mercury in seabirds: Insights from stable isotope analysis.  

PubMed

Mercury concentrations, together with nitrogen and carbon stable isotope signatures, were determined in body feather samples from northern fulmars Fulmarus glacialis and great skuas Catharacta skua, and in different flight feathers from great skuas. There were no significant relationships between trophic status, as defined using isotope analysis, and mercury concentration in the same feather type, in either species. Mercury concentrations in body feather samples were markedly different between fulmars and skuas, reflecting differences in diet, but there was no corresponding difference in trophic status as measured through nitrogen stable isotope signatures. We conclude that mercury concentrations and stable isotope values in feathers are uncoupled, mercury concentrations apparently reflecting the body pool of accumulated mercury at the time of feather growth whilst stable isotope values reflect the diet at the time of feather growth. There were significant positive correlations between the different flight feathers of great skuas for all three parameters measured. These were strongest between primary 10 and secondary 8, suggesting that these two feathers are replaced at the same time in the moult sequence in great skuas. Stable isotope analysis of different feathers may provide a means of investigating moult patterns in birds. PMID:15093080

Thompson, D R; Bearhop, S; Speakman, J R; Furness, R W

1998-01-01

308

Stable isotopes in ecosystem science: structure, function and dynamics of a subtropical Savanna.  

PubMed

Stable isotopes are often utilized as intrinsic tracers to study the effects of human land uses on the structural and functional characteristics of ecosystems. Here, we illustrate how stable isotopes of H, C, and O have been utilized to document changes in ecosystem structure and function using a case study from a subtropical savanna ecosystem. Specifically, we demonstrate that: (1) delta 13C values of soil organic carbon record a vegetation change in this ecosystem from C4 grassland to C3 woodland during the past 40-120 years, and (2) delta 2H and delta 18O of plant and soil water reveal changes in ecosystem hydrology that accompanied this grassland-to-woodland transition. In the Rio Grande Plains of North America, delta 13C values of plants and soils indicate that areas now dominated by C3 subtropical thorn woodland were once C4 grasslands. delta 13C values of current organic matter inputs from wooded landscape elements in this region are characteristic of C3 plants (-28 to -25/1000), while those of the associated soil organic carbon are higher and range from -20 to -15/1000. Approximately 50-90% of soil carbon beneath the present C3 woodlands is derived from C4 grasses. A strong memory of the C4 grasslands that once dominated this region is retained by delta 13C values of organic carbon associated with fine and coarse clay fractions. When delta 13C values are evaluated in conjunction with 14C measurements of that same soil carbon, it appears that grassland-to-woodland conversion occurred largely within the past 40-120 years, coincident with the intensification of livestock grazing and reductions in fire frequency. These conclusions substantiate those based on demographic characteristics of the dominant tree species, historical aerial photography, and accounts of early settlers and explores. Concurrent changes in soil delta 13C values and organic carbon content over the past 90 years also indicate that wooded landscape elements are behaving as sinks for atmospheric CO2 by sequestering carbon derived from both the previous C4 grassland and the present C3 woody vegetation. Present day woodlands have hydrologic characteristics fundamentally different from those of the original grasslands. Compared to plants in remnant grasslands, tree and shrub species in the woodlands are rooted more deeply and have significantly greater root biomass and density than grasslands. delta 18O and delta 2H values of plant and soil water confirm that grassland species acquire soil water primarily from the upper 0.5 m of the soil profile. In contrast, trees and shrubs utilize soil water from throughout the upper 4 m of the profile. Thus, soil water that formerly may have infiltrated beyond the reach of the grassland roots and contributed to local groundwater recharge or other hydrologic fluxes may now be captured and transpired by the recently formed woodland plant communities. The natural abundances of stable isotopes revealed fundamental information regarding the impacts of human land use activities on the structure and function of this subtropical savanna. Stable isotopes provided direct, spatially explicit evidence for dramatic changes in ecosystem physiognomy and demonstrated some functional consequences for the hydrologic cycle. Furthermore, grassland-to-woodland conversion has been geographically extensive in the worlds' drylands, suggesting that these ecosystem-level changes in vegetation structure, carbon cycling, and hydrology may have implications for regional/global biogeochemistry and climate. PMID:10407309

Boutton, T W; Archer, S R; Midwood, A J

1999-01-01

309

Lead Abundance In The Martian Mantle Deduced From The Isotopic Data In Snc Meteorites  

NASA Astrophysics Data System (ADS)

Isotopic data are a powerful tool for the study of planetary evolution. Assuming that the SNC meteorites are rocks from Mars their Sm-Nd-, Rb-Sr- and Pb-Pb-isotope systematics reveal the time scale for the chemical evolution of the Martian mantle. From the Rb -Sr isotopic systematic the existence of 3 isotopically distinct reservoirs on Mars was postulated, which remained isolated for a period of 4.3 +/- 0.2 Ga. The basaltic shergottites Shergotty, Zagami and Los Angeles have relatively high radiogenic Sr, which might come from a planetary crust. A second group, characterized by non radiogenic Sr, consists of the two mafic cumulates Nakhla and Chassigny, the olivine rich basaltic shergottites DaG 476, SaU 005, Dhofar 019and the basaltic shergottite QUE 94201, which may represent the depleted mantle. The depletion of this reservoir must have taken place during a very early process. as derived from the primitive Sr isotopes and the existence of Nd-142, the daughter product of the extinct Sm-146, found in Chassigny, the Nakhlites, SaU 005, and DaG476. A third group, with intermediate Sr isotopic composition, represented by the lherzolitic shergottites, could be derived from a primitive, unfractionated mantle. Our observed correlation of Sr-isotopes with Pb-isotopes in SNC's permits to estimate the Pb abundance for the Martian mantle. The Pb isotopes of all measured SNCs show a similar pattern as Sr isotopes. The initial Pb data of Los Angeles, Shergotty, and Zagami from the enriched crustal reservoir and of Nakhla and SaU 005 from the depleted mantle reservoir plot close to the 4.5 Ga Pb -Pb isochron.. We used this correlation to estimate the value (238U/204Pb) of 3.1 for the Martian mantle. This corresponds to 366 ppb Pb. Compared to the Earth with a = 8.8, Pb is enriched on Mars by at least a fact or of 2.5. The same enrichment was found for all other moderately volatile and volatile elements on Mars. From the high abundance of Pb in the sulfide phases of iron meteorites a chalcophile behavior of Pb was postulated. Contrary to the Earth the Martian core is sulfur rich. But, the more than 2 fold enrichment of Pb in the silicate phase of Mars compared to that of Earth might exclude its chalcophile behavior. Lead, with a condensation temperature from a solar gas lower than 600oK belongs to the group of volatile elements. Obviously, during planetary formation and evolution Pb behaves like a volatile and not like a chalcophile element.

Dreibus, G.; Jagoutz, E.

310

Stable sulfur isotopes as probes for ancient life in the solar system  

NASA Astrophysics Data System (ADS)

Secular changes in the stable sulfur isotope composition of seawater sulfate on Earth range from approximately 25 to 30 per mil (CDT). Minimal fractionation has been observed for the direct assimilation of seawater sulfate by plants into the two sulfur containing protein amino acids, methionine and cysteine. Similarly, sulfur isotope fractionation appears to be minimal with increasing trophic level. Thus, in theory, secular changes in the stable sulfur isotope composition of sulfur containing amino acids in ancient marine organisms should mimic that of seawater sulfate. The presence of sulfur containing amino acids elsewhere in the solar system and a comparison of their respective stable sulfur isotope values to those of sulfate containing minerals of similar ages may provide an alternative approach for determining the occurrence of past extraterrestrial life.

Engel, Michael H.

2007-10-01

311

Stable Carbon and Nitrogen Isotope Ratios of Sodium and Potassium Cyanide as a Forensic Signature  

SciTech Connect

Sodium and potassium cyanide are highly toxic, produced in large amounts by the chemical industry, and linked to numerous high-profile crimes. The U.S. Centers for Disease Control and Prevention has identified cyanide as one of the most probable agents to be used in a future chemical terrorism event. We investigated whether stable C and N isotopic content of sodium and potassium cyanide could serve as a forensic signature for sample matching, using a collection of 65 cyanide samples. A few of these samples displayed non-homogeneous isotopic content associated with degradation to a carbonate salt and loss of hydrogen cyanide. Most samples had highly reproducible isotope content. Of these, >95% could be properly matched based on C and N isotope ratios, with a false match rate <3%. These results suggest that stable C and N isotope ratios are a useful forensic signature for matching cyanide samples.

Kruzer, Helen W [Pacific Northwest National Laboratory (PNNL); Horita, Juske [ORNL; Moran, James J [Pacific Northwest National Laboratory (PNNL); Tomkins, Bruce A [ORNL; Janszen, Derek B [Pacific Northwest National Laboratory (PNNL); Carman, April [Pacific Northwest National Laboratory (PNNL)

2012-01-01

312

Stable Carbon and Nitrogen Isotope Ratios of Sodium and Potassium Cyanide as a Forensic Signature  

SciTech Connect

Sodium and potassium cyanide are highly toxic, produced in large amounts by the chemical industry, and linked to numerous high-profile crimes. The U.S. Centers for Disease Control and Prevention has identified cyanide as one of the most probable agents to be used in a future chemical terrorism event. We investigated whether stable C and N isotopic content of sodium and potassium cyanide could serve as a forensic signature for sample matching, using a collection of 65 cyanide samples. A few of these samples displayed non-homogeneous isotopic content associated with degradation to a carbonate salt and loss of hydrogen cyanide. Most samples had highly reproducible isotope content. Of these, >95% could be properly matched based on C and N isotope ratios, with a false match rate <3%. These results suggest that stable C and N isotope ratios are a useful forensic signature for matching cyanide samples.

Kreuzer, Helen W.; Horita, Juske; Moran, James J.; Tomkins, Bruce; Janszen, Derek B.; Carman, April J.

2012-01-03

313

Carbon, hydrogen and nitrogen in carbonaceous chondrites: abundances and isotopic compositions in bulk samples.  

PubMed

Whole-rock samples of 25 carbonaceous chondrites were analysed for contents of C, H and N and delta 13C, delta D and delta 15N. Inhomogeneous distribution of these isotopes within individual meteorites is pronounced in several cases. Few systematic intermeteorite trends were observed; N data are suggestive of isotopic inhomogeneity in the early solar system. Several chondrites revealed unusual compositions which would repay further, more detailed study. The data are also useful for classification of carbonaceous chondrites; N abundance and isotopic compositions can differentiate existing taxonomic groups with close to 100% reliability; Al Rais and Renazzo clearly constitute a discrete "grouplet"' and there are hints that both CI and CM groups may each be divisible into two subgroups. PMID:11539652

Kerridge, J F

1985-01-01

314

Origins of etioporphyrins in sediments - Evidence from stable carbon isotopes  

NASA Astrophysics Data System (ADS)

In samples of the Julia Creek and Condor oil shales (Australia, Albian, and early Tertiary, respectively) etioporphyrin III is significantly depleted in C-13 (4 per mil) relative to porphyrins derived from chlorophylls. This isotopic difference suggests a large contribution from some independent source. The haem group found in cytochromes derived from microbial sources is the most likely candidate.

Boreham, Christopher J.; Fookes, Christopher J. R.; Popp, Brian N.; Hayes, J. M.

1989-09-01

315

Origins of etioporphyrins in sediments: Evidence from stable carbon isotopes  

SciTech Connect

In samples of the Julia Creek and Condor oil shales (Australia, Albian, and early Tertiary, respectively) etioporphyrin III is significantly depleted in {sup 13}C (4{per thousand}) relative to porphyrins derived from chlorophylls. This isotopic difference suggest a large contribution from some independent source. The haem group found in cytochromes derived from microbial sources is the most likely candidate.

Boreham, C.J. (BMR, Canberra (Australia)); Fookes, C.J.R. (CSIRO, Menai (Australia)); Popp, B.N.; Hayes, J.M. (Indiana Univ., Bloomington (USA))

1989-09-01

316

Stable isotope geochemistry of fumaroles: an insight into volcanic surveillance  

NASA Astrophysics Data System (ADS)

In active volcanic environments magmatic water may accumulate in the volcanic-hosted geothermal systems, or, more rarely may reach the surface along deep fractures inside the volcano crater. Knowledge of magmatic contribution to emerging fluids in volcanic active areas is critical to understanding the chemical evolution of the magma, the conditions in which it exists in the crust, and the mechanisms by which it erupts in the crust. The source of volatiles (especially water) is also of interest when eruptions are driven by the expansion of hydrothermal fluids against atmospheric pressure, without the involvement of fresh magma ('hydrothermal' or 'phreatomagmatic' eruptions). In both cases the occurrence of volcanic and/or phreatic activities is likely to be preceded by substantial isotopic and chemical changes in the crater fumarolic systems. H and O isotopic composition of condensed water from crater fumaroles appear to be able to give strong evidence for the existence of magmatic waters in the high-temperature manifestations of the volcanic systems. Isotopic data and specific hydrological models from seven different volcanic systems (Galeras Volcano, Colombia, Kilauea Volcano, Hawaii, Kudryvy Volcano, Kuril volcanic arc, Mt St Helens, USA; Guagua Pichincha, Ecuador; Vulcano island, Italy; the Aegean Volcanic Arc, Greece) are discussed in order to highlight the possibility to use those isotopic parameters in the assessment of the environmental risks of an active volcanic area.

Panichi, C.; La Ruffa, G.

2001-12-01

317

Survey of stable isotope values in Irish surface waters  

Microsoft Academic Search

We present a study of the spatial distribution of ?18O and ?D values of lake and river waters from 144 locations in Ireland. Before we can gain a better understanding of paleoclimate records derived from lacustrine carbonate minerals we must understand mechanisms that produce variation in isotope values of modern surface waters. The focus of this study is to provide

Aaron F. Diefendorf; William P. Patterson

2005-01-01

318

Origins of etioporphyrins in sediments - Evidence from stable carbon isotopes  

NASA Technical Reports Server (NTRS)

In samples of the Julia Creek and Condor oil shales (Australia, Albian, and early Tertiary, respectively) etioporphyrin III is significantly depleted in C-13 (4 per mil) relative to porphyrins derived from chlorophylls. This isotopic difference suggests a large contribution from some independent source. The haem group found in cytochromes derived from microbial sources is the most likely candidate.

Boreham, Christopher J.; Fookes, Christopher J. R.; Popp, Brian N.; Hayes, J. M.

1989-01-01

319

STABLE CHLORINE ISOTOPE ANALYSIS OF CHLORINATED ORGANIC CONTAMINANTS  

EPA Science Inventory

The biogeochemical cycling of chlorinated organic contaminants in the environment is often difficult to understand because of the complex distributions of these compounds and variability of sources. To address these issues from an isotopic perspective, we have measured the, 37Cl...

320

Relative g-factor measurements in the stable Te isotopes  

SciTech Connect

The g(2{sub 1}{sup +}) values in the even Te isotopes between {sup 122}Te and {sup 130}Te have been measured simultaneously, relative to each other, by the transient-field technique. In addition, g factors were also measured for the 3/2{sub 2}{sup +} and 5/2{sub 1}{sup +} levels in {sup 125}Te.

Stuchbery, Andrew E.; Nakamura, Akiumi; Davidson, Paul M.; Watanabe, Hiroshi [Department of Nuclear Physics, Australian National University, Canberra ACT 0200 (Australia); Wilson, Anna N. [Department of Nuclear Physics, Australian National University, Canberra ACT 0200 (Australia); Department of Physics, Australian National University, Canberra ACT 0200 (Australia); Levon, Alexander I. [Institute for Nuclear Research, Prospekt Nauki 47, 03680 Kiev (Ukraine)

2007-09-15

321

Novel and non-traditional use of stable isotope tracers to study metal bioavailability from natural particles  

USGS Publications Warehouse

We devised a novel tracing approach that involves enriching test organisms with a stable metal isotope of low natural abundance prior to characterizing metal bioavailability from natural inorganic particles. In addition to circumventing uncertainties associated with labeling natural particles and distinguishing background metals, the proposed "reverse labeling" technique overcomes many drawbacks inherent to using radioisotope tracers. Specifically, we chronically exposed freshwater snails (Lymnaea stagnalis) to synthetic water spiked with Cu that was 99.4% 65Cu to increase the relative abundance of 65Cu in the snails tissues from 32% to >80%. The isotopically enriched snails were then exposed to benthic algae mixed with Cu-bearing FeAl particles collected from the Animas River (Colorado), an acid mine drainage impacted river. We used 63Cu to trace Cu uptake from the natural particles and inferred their bioavailability from calculation of Cu assimilation into tissues. Cu assimilation from these particles was 44%, indicating that 44% of the particulate Cu was absorbed by the invertebrate. This demonstrates that inorganic particulate Cu can be bioavailable. The reverse labeling approach shows great potential in various scientific areas such as environmental contamination and nutrition for addressing questions involving uptake of an element that naturally has multiple isotopes.

Croteau, Marie-Noele; Cain, Daniel J.; Fuller, Christopher C.

2013-01-01

322

Stable carbon isotope values document how a Late Holocene expansion in grasslands impacted vertebrates in northwestern Madagascar  

NASA Astrophysics Data System (ADS)

Madagascar is home to some of the world's most distinctive plants and animals. Unfortunately, forest loss and habitat degradation has had a dramatic impact on both floral and faunal communities. Here we use carbon isotope values in radiocarbon-dated bones to examine how the vertebrate community at Anjohibe Cave, northwestern Madagascar, responded to a Late Holocene increase in C4 grass abundance. Our data demonstrate that major changes in the vegetation and animal community are recent phenomena at Anjohibe. Extinct lemurs and hippopotamuses were present until ca. 1500 years ago. These taxa relied exclusively on C3 resources. Locally extirpated fauna were present until 300 years ago. The majority of these species also relied on C3 resources. Their presence strongly suggests that the region surrounding the cave was more wooded than it is now, possibly as recently as 300 years ago. All introduced individuals are modern. Rats (Rattus sp.), shrews (Suncus murinus), and the giant frog Hoplobatrachus cf. tigrinus, have remarkably high carbon isotope values, implicating substantial ingestion of C4 foods. It is possible that grass abundance has increased dramatically in the past 100 years. Alternatively, opportunistically granivorous rats and shrews may selectively consume seeds from C4 grasses. In agreement with previous studies, stable isotope data reveal details of vegetation and faunal turnover in Northwestern Madagascar. Grasses have increased, forest dwelling species have vanished, and introduced taxa are exploiting a novel niche.

Crowley, B. E.; Samonds, K.

2012-12-01

323

Stable isotopes of authigenic minerals in variably-saturated fractured tuff  

SciTech Connect

Identifying stable isotope variation and mineralogical changes in fractured rock may help establish the history of climatic and geomorphological processes that might affect the isolation properties of a waste repository site. This study examines the use of the stable isotope ratios of oxygen ({sup 18}O/{sup 16}O) and carbon ({sup 13}C/{sup 12}C) in authigenic minerals as hydrogeochemical tools tracing low-temperature rock-water interaction in variably-saturated fractured stuff. Isotopic compositions of fracture-filling and rock matrix minerals in the Apache Leap tuff, near Superior, Arizona were concordant with geothermal temperatures and in equilibrium with water isotopically similar to present-day meteoric water and groundwater. Oxygen and carbon isotope ratios of fracture-filling, in unsaturated fractured tuff, displayed an isotopic gradient believed to result from near-surface isotopic enrichment due to evaporation rather than the effects of rock-water interaction. Oxygen isotope ratios of rock matrix opal samples exhibited an isotopic gradient believed to result from, leaching and reprecipitation of silica at depth. Methods and results can be used to further define primary flowpaths and the movement of water in variably-saturated fractured rock. 71 refs., 23 figs., 3 tabs.

Weber, D.S.; Evans, D.D.

1988-11-01

324

Stable isotope record of coexisting apatite and dolomite in Early Cambrian phosphorites, Meishucun section, South China  

NASA Astrophysics Data System (ADS)

The Precambrian-Cambrian transition forms one of the most dramatic time periods in Earth's history, as global changes in tectonics, climate and chemistry in the atmosphere and oceans favoured the worldwide Cambrian Radiation and a concomitant ecosphere revolution. This time interval is paralleled by the first appearance of the widespread giant phosphorites. The well-known Meishucun section (South China), a former candidate section for the Pc-C boundary, documents phosphorite genesis amongst a rapid biodiversification, immediately following the end of the Precambrian in a low-latitude, shallow-water carbonate shelf. This contribution aims to elucidate the relation between simultaneous phosphorite deposition and global environmental conditions at the Pc-C boundary by using stable carbon and oxygen isotope analyses. Accurate determinations of d13C and d18O values may allow conclusions about ancient ocean circulation, paleo-productivity, paleo-temperatures, and most prominently diagenetic processes. The investigated samples from the Meishucun section basically consist of apatite, dolomite, and quartz that may be further devided into a lower and upper phosphorite as well as an overlying dolostone intervall. Additionally, calcite and siderite occur as minor compounds in some samples. Bulk d13C values of the carbonate fraction correlate with dolomite abundance throughout the section ranging from -4 to 1 per mil. Furthermore, several horizons suggest a relation between d13C values and apatite content, implying lower d13C values in apatites compared to coexisting dolomite. A slight negative d13C excursion at the top of the lower phosphorite coincides with the first appearance of small shelly fossils. Corresponding bulk d18O values generally show a stratigraphic-upward trend towards lower values throughout the record with slightly higher values in dolomite-rich sections. This may either indicate a warming trend during deposition, an isotopic shift in sea water composition, or an increasing contribution from carbonate apatite contents. Tentative calculations of temperatures in the fluids responsible for carbonate and phosphate mineral formation are based on experimental calibrations of the respective isotope systems by using d18O values of the carbonate fraction. They reveal mean temperatures ranging from 9C to 51C or 50C to 114C considering potential d18O values of -8 per mil and 0 per mil vs. SMOW in the mother fluids, respectively. Maximum temperatures of about 52C using -8 per mil vs. SMOW at the top of the lower phosphorite sequence possibly point towards a pronounced diagenetic influence. However, bulk isotope values are subject to mineralogical interferences. In particular, FTIR spectroscopic analyses show that the apatites also contain carbonate groups. Thus, bulk isotopic values of carbonates reflect a mixed signal of different phases of mineral genesis. This assumption is confirmed by petrographic observations that in most cases display apatite-coated dolomites suggesting an earlier onset of dolomite formation compared to apatite. Accordingly, d18O values of phosphate groups from the above mentioned phosphorite sequence indicate a mean temperature of only 31C (water: -8 per mil SMOW). Assuming the same isotopic composition of dolomite and apatite precipitating fluids, lower temperatures are calculated for apatite formation. In conclusion, a separation of the different carbonate groups is essential to obtain oxygen and carbon isotopic signals of the corresponding mineral phase, which is currently investigated by fractionation experiments. Acknowledgements: The presented research is supported by DFG research group 736 and Leibniz Institute for Baltic Sea Research.

Wegwerth, Antje; Struck, Ulrich; Segl, Monika; Vennemann, Torsten W.; Gehlken, Peer-L.; Heubeck, Christoph; Bttcher, Michael E.

2010-05-01

325

Using Stable Water Isotopes to Evaluate Basin-Scale Simulations of Surface Water Budgets  

Microsoft Academic Search

Two rare but naturally occurring isotopes of water, 1H2 18 O and 1H2H16O, are becoming of practical use in diagnosis of climate and earth system model performance. Their value as tracers and validation tools in hydro- logical subsystems derives from the systematic and different (from each other and from the most abundant water isotope: 1H1H16O) paths and residence times they

A. Henderson-Sellers; K. McGuffie; D. Noone; P. Irannejad

2004-01-01

326

Stable isotopes in collagen and Late Quaternary carnivore palaeoecology  

Microsoft Academic Search

Several taxa of large carnivores co-occurred during the late Pleistocene in the steppe-tundra ecosystem, such as wolf Canis lupus, cave lion Panthera leo spelaea, cave hyaena Crocuta crocuta spelaea, brown bear Ursus arctos and cave bear Ursus spelaeus and Ursus ingressus. This abundance of taxa belonging to the same guild raises questions about niche partitioning, especially in terms of dietary

Herv Bocherens

2010-01-01

327

Lignocellulose-responsive bacteria in a southern California salt marsh identified by stable isotope probing  

PubMed Central

Carbon cycling by microbes has been recognized as the main mechanism of organic matter decomposition and export in coastal wetlands, yet very little is known about the functional diversity of specific groups of decomposers (e.g., bacteria) in salt marsh benthic trophic structure. Indeed, salt marsh sediment bacteria remain largely in a black box in terms of their diversity and functional roles within salt marsh benthic food web pathways. We used DNA stable isotope probing (SIP) utilizing 13C-labeled lignocellulose as a proxy to evaluate the fate of macrophyte-derived carbon in benthic salt marsh bacterial communities. Overall, 146 bacterial species were detected using SIP, of which only 12 lineages were shared between enriched and non-enriched communities. Abundant groups from the 13C-labeled community included Desulfosarcina, Spirochaeta, and Kangiella. This study is the first to use heavy-labeled lignocellulose to identify bacteria responsible for macrophyte carbon utilization in salt marsh sediments and will allow future studies to target specific lineages to elucidate their role in salt marsh carbon cycling and ultimately aid our understanding of the potential of salt marshes to store carbon.

Darjany, Lindsay E.; Whitcraft, Christine R.; Dillon, Jesse G.

2014-01-01

328

Identification of functionally active aerobic methanotrophs in sediments from an arctic lake using stable isotope probing.  

PubMed

Arctic lakes are a significant source of the greenhouse gas methane (CH(4) ), but the role that methane oxidizing bacteria (methanotrophs) play in limiting the overall CH(4) flux is poorly understood. Here, we used stable isotope probing (SIP) techniques to identify the metabolically active aerobic methanotrophs in upper sediments (0-1?cm) from an arctic lake in northern Alaska sampled during ice-free summer conditions. The highest CH(4) oxidation potential was observed in the upper sediment (0-1?cm depth) with 1.59?mol?g wet weight(-1) day(-1) compared with the deeper sediment samples (1-3?cm, 3-5?cm and 5-10?cm), which exhibited CH(4) oxidation potentials below 0.4?mol?g wet weight(-1) day(-1) . Both type I and type II methanotrophs were directly detected in the upper sediment total communities using targeted primer sets based on 16S rRNA genes. Sequencing of 16S rRNA genes and functional genes (pmoA and mxaF) in the (13) C-DNA from the upper sediment indicated that type I methanotrophs, mainly Methylobacter, Methylosoma, Methylomonas and Methylovulum miyakonense, dominated the assimilation of CH(4) . Methylotrophs, including the genera Methylophilus and/or Methylotenera, were also abundant in the (13) C-DNA. Our results show that a diverse microbial consortium acquired carbon from CH(4) in the sediments of this arctic lake. PMID:22429394

He, Ruo; Wooller, Matthew J; Pohlman, John W; Catranis, Catharine; Quensen, John; Tiedje, James M; Leigh, Mary Beth

2012-06-01

329

Radiocarbon and stable-isotope geochemistry of organic and inorganic carbon in Lake Superior  

NASA Astrophysics Data System (ADS)

We present a lake-wide investigation of Lake Superior carbon and organic matter biogeochemistry using radiocarbon, stable isotope, and carbon concentrations. Dissolved inorganic carbon (DIC) abundance in the lake was 121-122 Tg C, with offshore concentration and?13C values being laterally homogenous and tightly coupled to the physical and thermal regime and biochemical processes. Offshore ?14C of DIC (50-65) exhibited lateral homogeneity and was more 14C enriched than co-occurring atmospheric CO2 (38); nearshore ?14C of DIC (36-38) was similar to atmospheric CO2. Dissolved organic carbon (DOC) abundance was 14.2-16.4 Tg C. DOC's concentration and ?13C were homogenous in June (mixed lake), but varied laterally during August (stratification) possibly due to spatial differences in lake productivity. Throughout sampling, DOC had modern radiocarbon values (14-58) indicating a semilabile nature with a turnover time of ?60 years. Lake particulate organic carbon (POC, 0.9-1.3 Tg C) was consistently 13C depleted relative to DOC. The ?15N of epilimnetic particulate organic nitrogen shifted to more negative values during stratification possibly indicating greater use of nitrate (rather than ammonium) by phytoplankton in August. POC's radiocarbon was spatially heterogeneous (?14C range: 58 to -303), and generally 14C depleted relative to DOC and DIC. POC 14C depletion could not be accounted for by black carbon in the lake but, because of its spatial and temporal distribution, is attributed to sediment resuspension. The presence of old POC within the epilimnion of the open lake indicates possible benthic-pelagic coupling in the lake's organic carbon cycle; the ultimate fate of this old POC bears further investigation.

Zigah, Prosper K.; Minor, Elizabeth C.; Werne, Josef P.

2012-03-01

330

Stable carbon isotopes: Possible clues to early life on mars  

Microsoft Academic Search

Organic and inorganic carbon in terrestrial near-surface environments are characterized by a marked difference in their 13C\\/12C ratios which can be traced back in the Earth's sedimentary record over almost 4 billion years. There is no doublt that the bias in favour of 12C displayed by biogenic matter derives, for the most part, from the isotope-selecting properties of the carbon-fixing

Manfred Schidlowski

1992-01-01

331

Carbon cycle for Lake Washington - a stable isotope study  

Microsoft Academic Search

The authors investigate the carbon cycle in Lake Washington for the year 1980 using monthly measurements of the dissolved inorganic carbon (DIC) and its ¹³C:¹²C isotopic composition. Mass balances of DIC and its ¹³C:¹²C yield estimates of CO gas exchange rates and net organic carbon production rates. Between 24 June and 13 August, the calculated CO gas invasion rate of

P. D. Quay; S. R. Emerson; B. M. Quay; A. H. Devol

1986-01-01

332

Determination of stable carbon and hydrogen isotopes of light hydrocarbons  

Microsoft Academic Search

A combined system for the measurement of ¹³C\\/¹²C and D\\/H ratios on light hydrocarbons (C-C) and CO is described. The system is designed for natural gas and sediment gas analyses. It comprises gas chromatographic separation with online combustion of hydrocarbons to CO and HO, reduction of HO to H on zinc in closed ampules, and mass spectrometric determination of isotope

Ingolf. Dumke; Eckhard. Faber; Juergen. Poggenburg

1989-01-01

333

Stable isotope-labelled feed nutrients to assess nutrient-specific feed passage kinetics in ruminants.  

PubMed

Knowledge of digesta passage kinetics in ruminants is essential to predict nutrient supply to the animal in relation to optimal animal performance, environmental pollution and animal health. Fractional passage rates (FPR) of feed are widely used in modern feed evaluation systems and mechanistic rumen models, but data on nutrient-specific FPR are scarce. Such models generally rely on conventional external marker techniques, which do not always describe digesta passage kinetics in a satisfactory manner. Here the use of stable isotope-labelled dietary nutrients as a promising novel tool to assess nutrient-specific passage kinetics is discussed. Some major limitations of this technique include a potential marker migration, a poor isotope distribution in the labelled feed and a differential disappearance rate of isotopes upon microbial fermentation in non-steady state conditions. Such limitations can often be circumvented by using intrinsically stable isotope-labelled plant material. Data are limited but indicate that external particulate markers overestimate rumen FPR of plant fibre compared with the internal stable isotope markers. Stable isotopes undergo the same digestive mechanism as the labelled feed components and are thus of particular interest to specifically measure passage kinetics of digestible dietary nutrients. 2013 Society of Chemical Industry. PMID:24114801

Warner, Daniel; Dijkstra, Jan; Hendriks, Wouter H; Pellikaan, Wilbert F

2014-03-30

334

Low stable carbon isotope fractionation by coccolithophore RubisCO  

NASA Astrophysics Data System (ADS)

The 13C/ 12C ratio of carbon compounds is used to identify sources and sinks in the global carbon cycle. However, the relatively enriched 13C content observed for marine organic carbon remains enigmatic. The majority of oceanic carbon is fixed by algae and cyanobacteria via the Calvin-Benson-Bassham cycle, yet isotopic discrimination by the CO 2 fixation enzyme, RubisCO (ribulose 1,5-bisphosphate carboxylase/oxygenase), has only been measured for a single marine cyanobacterium. Different forms of RubisCO occur in different phytoplankton species (overall amino acid identity varying by as much as 75%) and thus may vary in the degree to which they fractionate carbon. Here we measured isotope discrimination by RubisCO from the coccolithophore Emiliania huxleyi, a cosmopolitan species used as a marine algal model .E. huxleyi RubisCO discriminated substantially less ( ? = 11.1) against 13CO 2 than other RubisCO enzymes (18-29), despite having Michaelis-Menten kinetic parameters ( K = 72 ?M; Vmax = 0.66 ?mol min -1 mg -1 protein) similar to those measured for RubisCO enzymes from different organisms. If widespread, decreased isotope discrimination of 13C by phytoplankton RubisCO may be a major factor influencing the enriched 13C content of marine organic carbon. This finding emphasizes the necessity of (a) determining ? values for RubisCOs of other marine phytoplankton and (b) re-evaluation of ?13C values from physiological, environmental, and geological studies.

Boller, Amanda J.; Thomas, Phaedra J.; Cavanaugh, Colleen M.; Scott, Kathleen M.

2011-11-01

335

Effects of nutritional restriction on nitrogen and carbon stable isotopes in growing seabirds.  

PubMed

When using stable isotopes as dietary tracers it is essential to consider effects of nutritional state on isotopic fractionation. While starvation is known to induce enrichment of (15)N in body tissues, effects of moderate food restriction on isotope signatures have rarely been tested. We conducted two experiments to investigate effects of a 50-55% reduction in food intake on delta(15)N and delta(13)C values in blood cells and whole blood of tufted puffin chicks, a species that exhibits a variety of adaptive responses to nutritional deficits. We found that blood from puffin chicks fed ad libitum became enriched in (15)N and (13)C compared to food-restricted chicks. Our results show that (15)N enrichment is not always associated with food deprivation and argue effects of growth on diet-tissue fractionation of nitrogen stable isotopes (Delta(15)N) need to be considered in stable isotope studies. The decrease in delta(13)C of whole blood and blood cells in restricted birds is likely due to incorporation of carbon from (13)C-depleted lipids into proteins. Effects of nutritional restriction on delta(15)N and delta(13)C values were relatively small in both experiments (delta(15)N: 0.77 and 0.41 per thousand, delta(13)C: 0.20 and 0.25 per thousand) compared to effects of ecological processes, indicating physiological effects do not preclude the use of carbon and nitrogen stable isotopes in studies of seabird ecology. Nevertheless, our results demonstrate that physiological processes affect nitrogen and carbon stable isotopes in growing birds and we caution isotope ecologists to consider these effects to avoid drawing spurious conclusions. PMID:17406905

Williams, Cory T; Buck, C Loren; Sears, Justine; Kitaysky, Alexander S

2007-08-01

336

Stable isotope analysis of dissolved carbon species of Hot Lake, WA  

NASA Astrophysics Data System (ADS)

Hot Lake is a hypersaline, meromictic lake in north-central Washington. The lake is epsomitic, with seasonably-variable salinity (.2 to 2 M magnesium sulfate) and produces carbonates and salt precipitates. The maximum depth of the lake is around 2.5 m, and below a thermocline there is intense solar heat retention in the monolimnion, often exceeding 50C. Despite these extreme and variable conditions, a microbial mat of up to 1.5 cm thick thrives annually in Hot Lake. The mat is widespread throughout the lake at water depths (during our experiments) ranging from 60cm-140cm. It is comprised of a variety of cyanobacteria along with other autotrophic and heterotrophic bacteria. These populations are visibly stratified with four consistent laminae displaying differences in bacterial pigmentation. Many of the layers contain carbonate species, but the full relationship between the mat and the carbonate crystallization is not known. We are studying the microbial interactions and carbon cycling of the mat communities, using stable isotope analysis of the mat and the lake water, both in situ and ex situ. We are exploring the incorporation and movement of carbon in the mat, spatially and temporally, to understand the fixation mechanisms and metabolic processes at play in this environment. This was done primarily using stable isotope ratio mass spectrometry. The focus of this work is on the study and measurement of dissolved organic and inorganic carbon using a GasBench and IRMS setup, following methods adapted from Lang et al. (2012). To account for the unique chemistry of Hot Lake, trials on the effects of oxidation conditions and salinity were done on lab-synthesized samples to compare to Hot Lake results. The majority of lake water analyses were done in conjunction with a stable isotope probing (SIP) experiment, completed during two 24-hour periods at Hot Lake in June and July of 2013. The SIP experiments included ex situ incubations (in separate glass containers on the shore of the lake immediately after removal from the lake) under various conditions (with labeled and unlabeled substrate, in the presence and absence of daylight, with and without undermat sediment) performed as both constant labeling and pulse-chase experiments. We incubated mat sections in lake water (from equivalent depth to the collected mat) spiked either with 13C-labeled or natural abundance organic (acetate or glucose) or inorganic (bicarbonate) substrates. For those conditions in which inorganic carbon was added, we measured the DOC of the water in each condition to measure conversion from DIC to DOC and vice versa for consumption/conversion of DOC to DIC. By comparing the GasBench DIC/DOC results of these various conditions over the course of the experiments, we assessed carbon flow into and out of the mat around a daily cycle. The assessments were made using the ?13C values and data of the lake water samples from the IRMS in conjunction with bulk mat isotope values. Our data show significant interactions between DIC and DOC pools and allow us to estimate the daily balance between carbon fixation and remineralization mediated by the microbial mat.

Courtney, S.; Moran, J.; Cory, A. B.; Lindemann, S. R.; Fredrickson, J.

2013-12-01

337

Estimation of soil water evaporative loss after tillage operation using the stable isotope technique  

NASA Astrophysics Data System (ADS)

Application of stable isotopes in soil studies has improved quantitative evaluation of evaporation and other hydrological processes in soil. This study was carried out to determine the effect of tillage on evaporative loss of water from the soil. Zero tillage and conventional tillage were compared. Suction tubes were installed for soil water collection at the depths 0.15, 0.50, and 1.0 m by pumping soil water with a peristaltic pump. Soil water evaporation was estimated using stable isotopes of water. The mean isotopic composition of the soil water at 0.15 m soil depth were -1.15 (?18O) and -0.75 (?D) and were highly enriched compared with the isotopic compositions of the site precipitation. Soil water stable isotopes (?18O and ?D) were more enriched near the surface under zero tillage while they were less negative down the profile under zero tillage. This suggests an occurrence of more evaporation and infiltration under conventional then zero tillage, respectively, because evaporative fractionation contributes to escape of lighter isotopes from liquid into the vapour phase leading to enrichment in heavy isotopes in the liquid phase. The annual evaporation estimated using the vapour diffusion equation ranges from 46-70 and 54-84 mm year-1 under zero and conventional tillage, respectively, indicating more evaporation under conventional tillage compared with zero tillage. Therefore, to reduce soil water loss, adoption of conservation tillage practices such as zero tillage is encouraged.

Busari, M. A.; Salako, F. K.; Tuniz, C.; Zuppi, G. M.; Stenni, B.; Adetunji, M. T.; Arowolo, T. A.

2013-09-01

338

A manual for a laboratory information management system (LIMS) for light stable isotopes  

USGS Publications Warehouse

The reliability and accuracy of isotopic data can be improved by utilizing database software to (i) store information about samples, (ii) store the results of mass spectrometric isotope-ratio analyses of samples, (iii) calculate analytical results using standardized algorithms stored in a database, (iv) normalize stable isotopic data to international scales using isotopic reference materials, and (v) generate multi-sheet paper templates for convenient sample loading of automated mass-spectrometer sample preparation manifolds. Such a database program is presented herein. Major benefits of this system include (i) an increase in laboratory efficiency, (ii) reduction in the use of paper, (iii) reduction in workload due to the elimination or reduction of retyping of data by laboratory personnel, and (iv) decreased errors in data reported to sample submitters. Such a database provides a complete record of when and how often laboratory reference materials have been analyzed and provides a record of what correction factors have been used through time. It provides an audit trail for stable isotope laboratories. Since the original publication of the manual for LIMS for Light Stable Isotopes, the isotopes 3 H, 3 He, and 14 C, and the chlorofluorocarbons (CFCs), CFC-11, CFC-12, and CFC-113, have been added to this program.

Coplen, Tyler B.

1997-01-01

339

A manual for a Laboratory Information Management System (LIMS) for light stable isotopes  

USGS Publications Warehouse

The reliability and accuracy of isotopic data can be improved by utilizing database software to (i) store information about samples, (ii) store the results of mass spectrometric isotope-ratio analyses of samples, (iii) calculate analytical results using standardized algorithms stored in a database, (iv) normalize stable isotopic data to international scales using isotopic reference materials, and (v) generate multi-sheet paper templates for convenient sample loading of automated mass-spectrometer sample preparation manifolds. Such a database program is presented herein. Major benefits of this system include (i) an increase in laboratory efficiency, (ii) reduction in the use of paper, (iii) reduction in workload due to the elimination or reduction of retyping of data by laboratory personnel, and (iv) decreased errors in data reported to sample submitters. Such a database provides a complete record of when and how often laboratory reference materials have been analyzed and provides a record of what correction factors have been used through time. It provides an audit trail for stable isotope laboratories. Since the original publication of the manual for LIMS for Light Stable Isotopes, the isotopes 3 H, 3 He, and 14 C, and the chlorofluorocarbons (CFCs), CFC-11, CFC-12, and CFC-113, have been added to this program.

Coplen, Tyler B.

1998-01-01

340

Stable isotope reactive transport modeling in water-rock interactions during CO2 injection  

NASA Astrophysics Data System (ADS)

Stable isotopes can be of great usefulness in the characterization and monitoring of CO2 sequestration sites. Stable isotopes can be used to track the migration of the CO2 plume and identify leakage sources. Moreover, they provide unique information about the chemical reactions that take place on the CO2-water-rock system. However, there is a lack of appropriate tools that help modelers to incorporate stable isotope information into the flow and transport models used in CO2 sequestration problems. In this work, we present a numerical tool for modeling the transport of stable isotopes in groundwater reactive systems. The code is an extension of the groundwater single-phase flow and reactive transport code HYTEC [2]. HYTEC's transport module was modified to include element isotopes as separate species. This way, it is able to track isotope composition of the system by computing the mixing between the background water and the injected solution accounting for the dependency of diffusion on the isotope mass. The chemical module and database have been expanded to included isotopic exchange with minerals and the isotope fractionation associated with chemical reactions and mineral dissolution or precipitation. The performance of the code is illustrated through a series of column synthetic models. The code is also used to model the aqueous phase CO2 injection test carried out at the Lamont-Doherty Earth Observatory site (Palisades, New York, USA) [1]. References [1] N. Assayag, J. Matter, M. Ader, D. Goldberg, and P. Agrinier. Water-rock interactions during a CO2 injection field-test: Implications on host rock dissolution and alteration effects. Chemical Geology, 265(1-2):227-235, July 2009. [2] Jan van der Lee, Laurent De Windt, Vincent Lagneau, and Patrick Goblet. Module-oriented modeling of reactive transport with HYTEC. Computers & Geosciences, 29(3):265-275, April 2003.

Hidalgo, Juan J.; Lagneau, Vincent; Agrinier, Pierre

2010-05-01

341

Monitoring of the aerobe biodegradation of chlorinated organic solvents by stable isotope analysis  

NASA Astrophysics Data System (ADS)

Our chemical-biological basic research aims to eliminate chlorinated environmental contaminants from aquifers around industrial areas in the frame of research program supported by the European Social Fund (TMOP-4.2.2.A-11/1/KONV-2012-0043). The most careful and simplest way includes the in situ biodegradation with the help of cultured and compound specific strains. Numerous members of Pseudomonas bacteria are famous about function of bioremediation. They can metabolism the environmental hazardous chemicals like gas oils, dyes, and organic solvents. Our research based on the Pseudomonas putida F1 strain, because its ability to degrade halogenated hydrocarbons such as trichloroethylene. Several methods were investigated to estimate the rate of biodegradation, such as the measurement of the concentration of the pollutant along the contamination pathway, the microcosm's studies or the compound specific stable isotope analysis. In this area in the Transcarpathian basin we are pioneers in the stable isotope monitoring of biodegradation. The main goal is to find stable isotope fractionation factors by stable isotope analysis, which can help us to estimate the rate and effectiveness of the biodegradation. The subsequent research period includes the investigation of the method, testing its feasibility and adaptation in the environment. Last but not least, the research gives an opportunity to identify the producer of the contaminant based on the stable isotope composition of the contaminant.

Horvth, Anik; Fut, Istvn; Palcsu, Lszl

2014-05-01

342

Tracking Diet Preferences of Bats Using Stable Isotope and Fatty Acid Signatures of Faeces  

PubMed Central

Stable isotope and fatty acid signatures of biomaterials can provide important information about the dietary niche of animals. Stable isotope and fatty acid signatures differ between aquatic and terrestrial food webs, and therefore can be used to assess the aquatic and terrestrial contributions to the diets of species. We studied faecal samples of three co-occurring bat species with known differences in feeding preferences. The aim was to assess whether stable isotope and fatty acid signatures of faeces can be used to determine feeding preferences. We used bat faeces because they can be easily and non-invasively collected. We hypothesised that faeces stable isotope and fatty acid signatures will reveal the terrestrial, aquatic and mixed feeding niches of Myotis myotis, M. daubentonii, and M. mystacinus, respectively. As predicted, the faeces of M. myotis were characterized by higher ?13C values and higher concentrations of linoleic acid and total ?6 polyunsaturated fatty acids (PUFAs), which are typically higher in terrestrial food webs. The faeces of M. daubentonii had higher ?15? values and higher concentrations of docosahexaenoic acid and total ?3 PUFAs, characteristic features of aquatic systems. Myotis mystacinus faeces had intermediate ?15? values and concentrations of both types of fatty acids. Our results show that analysing stable isotope and/or fatty acid signatures of faeces provides a promising, non-invasive tool to study the feeding ecology of bats and to assess aquatic-terrestrial interactions.

Lam, Monika My-Y; Martin-Creuzburg, Dominik; Rothhaupt, Karl-Otto; Safi, Kamran; Yohannes, Elizabeth; Salvarina, Ioanna

2013-01-01

343

Tracking diet preferences of bats using stable isotope and fatty acid signatures of faeces.  

PubMed

Stable isotope and fatty acid signatures of biomaterials can provide important information about the dietary niche of animals. Stable isotope and fatty acid signatures differ between aquatic and terrestrial food webs, and therefore can be used to assess the aquatic and terrestrial contributions to the diets of species. We studied faecal samples of three co-occurring bat species with known differences in feeding preferences. The aim was to assess whether stable isotope and fatty acid signatures of faeces can be used to determine feeding preferences. We used bat faeces because they can be easily and non-invasively collected. We hypothesised that faeces stable isotope and fatty acid signatures will reveal the terrestrial, aquatic and mixed feeding niches of Myotis myotis, M. daubentonii, and M. mystacinus, respectively. As predicted, the faeces of M. myotis were characterized by higher ?(13)C values and higher concentrations of linoleic acid and total ?6 polyunsaturated fatty acids (PUFAs), which are typically higher in terrestrial food webs. The faeces of M. daubentonii had higher ?(15)? values and higher concentrations of docosahexaenoic acid and total ?3 PUFAs, characteristic features of aquatic systems. Myotis mystacinus faeces had intermediate ?(15)? values and concentrations of both types of fatty acids. Our results show that analysing stable isotope and/or fatty acid signatures of faeces provides a promising, non-invasive tool to study the feeding ecology of bats and to assess aquatic-terrestrial interactions. PMID:24376703

Lam, Monika My-Y; Martin-Creuzburg, Dominik; Rothhaupt, Karl-Otto; Safi, Kamran; Yohannes, Elizabeth; Salvarina, Ioanna

2013-01-01

344

A novel sample decomposition technique at atmospheric pressure for the determination of Os abundances in iron meteorites using isotope dilution inductively coupled plasma-mass spectrometry.  

PubMed

A safe and reliable analytical technique for the determination of Os abundances in ten iron meteorites of various chemical groups was developed using isotope dilution inductively coupled plasma-mass spectrometry coupled with a sample decomposition technique. A major advantage of the sample decomposition technique developed here is that the pressure inside the reaction flask is not increased through the decomposition reaction because the flask is a fully opened system, obviating the risk of explosion of the glass apparatus. Another advantage is that there is no restriction in the sample size being decomposed. In this study, about 2 g of metallic sample were decomposed safely, and this sample size, > 10 times larger than that typically used for the Carius tube technique, allows one to obtain more reliable Os data for heterogeneous samples. The metallic samples were decomposed in a glass flask purged with Ar. Since the O2 was purged from the reaction flask, Os was not oxidised to volatile OsO4, thereby preventing significant evaporation loss of Os. The typical recovery of Os throughout the sample decomposition and separation processes was > 80%, and the total Os blank through the decomposition of a 1 g amount of sample was less than 20 pg. Os abundances were determined by means of stable isotope dilution mass spectrometry using a 190Os-enriched isotopic tracer. Except for Sikhote-Alin, the measured Os abundances in almost all the iron meteorites exhibited a good agreement with the previously published Os abundance data, within the analytical uncertainty achieved in this study (2-5%). For the Sikhote-Alin meteorite, on the basis of a better correlation between Os and Ir abundances, we believe that our Os abundance data should be more reliable. The Os abundance data obtained in this work clearly demonstrated the suitability of the newly developed sample decomposition procedure for low level Os determinations. PMID:11445949

Hattori, M; Hirata, T

2001-06-01

345

Stable isotope monitoring of ionic trapping of CO2 in deep brines  

NASA Astrophysics Data System (ADS)

CO2 injection into a depleted gas-reservoir is used as a combined method for Enhanced Gas Recovery (EGR) and CO2 storage. In order to safeguard this process, monitoring the degree of dissolution and potential further precipitation and mineral interactions are a necessity. Here a method is introduced, in which stable isotope and geochemical data can be used as a monitoring technique to quantify ionic trapping of injected CO2. Isotope and geochemical data of dissolved inorganic carbon (DIC) can be used to distinguish between already present and to be injected inorganic carbon. Injected CO2, for instance, is formed during combustion of former plant material and is expected to have a different isotope ratio (?13C value) than the baseline data of the aquifer. This is because combusted CO2 originates from organic material, such as coal and oil with a predominant C3 plant signature. Mixing the injected CO2 with groundwater is therefore expected to change the isotope, as well as the geochemical composition of the groundwater. Mass balance calculations with stable isotope ratios can serve to quantify ionic trapping of CO2 as DIC in groundwater. However, depending on the composition of the aquifer, weathering of carbonate or silicates may occur. Enhanced weathering processes due to CO2 injection can also further influence the isotopic composition. Such interactions between dissolved CO2 and minerals depend on the temperature and pressure regimes applied. Field data, as well as laboratory experiments are planned to quantify isotope ratios of dissolved inorganic carbon as well as oxygen isotope ratios of the water. These are indicative of geochemical processes before, during and after EGR. The isotope method should therefore provide a new tool to quantify the efficiency of ionic trapping under various temperatures and pressures. Keywords: Enhanced Gas Recovery, monitoring of CO2 dissolution, stable isotopes

Myrttinen, A.; Barth, J. A. C.; Becker, V.; Blum, P.; Grathwohl, P.

2009-04-01

346

Caution on the use of liquid nitrogen traps in stable hydrogen isotope-ratio mass spectrometry  

USGS Publications Warehouse

An anomalous stable hydrogen isotopic fractionation of 4 in gaseous hydrogen has been correlated with the process of adding liquid nitrogen (LN2) to top off the dewar of a stainless-steel water trap on a gaseous hydrogen-water platinum equilibration system. Although the cause of this isotopic fractionation is unknown, its effect can be mitigated by (1) increasing the capacity of any dewars so that they do not need to be filled during a daily analytic run, (2) interspersing isotopic reference waters among unknowns, and (3) applying a linear drift correction and linear normalization to isotopic results with a program such as Laboratory Information Management System (LIMS) for Light Stable Isotopes. With adoption of the above guidelines, measurement uncertainty can be substantially improved. For example, the long-term (months to years) ?2H reproducibility (1& sigma; standard deviation) of nine local isotopic reference waters analyzed daily improved substantially from about 1 to 0.58 . This isotopically fractionating mechanism might affect other isotope-ratio mass spectrometers in which LN2 is used as a moisture trap for gaseous hydrogen

Coplen, Tyler B.; Qi, Haiping

2010-01-01

347

Caution on the use of liquid nitrogen traps in stable hydrogen isotope-ratio mass spectrometry  

USGS Publications Warehouse

An anomalous stable hydrogen isotopic fractionation of 4 ??? in gaseous hydrogen has been correlated with the process of adding liquid nitrogen (LN2) to top off the dewar of a stainless-steel water trap on a gaseous hydrogen-water platinum equilibration system. Although the cause of this isotopic fractionation is unknown, its effect can be mitigated by (1) increasing the capacity of any dewars so that they do not need to be filled during a daily analytic run, (2) interspersing isotopic reference waters among unknowns, and (3) applying a linear drift correction and linear normalization to isotopic results with a program such as Laboratory Information Management System (LIMS) for Light Stable Isotopes. With adoption of the above guidelines, measurement uncertainty can be substantially improved. For example, the long-term (months to years) ??2H reproducibility (1?? standard deviation) of nine local isotopic reference waters analyzed daily improved substantially from about 1 ??? to 0.58 ???. This isotopically fractionating mechanism might affect other isotope-ratio mass spectrometers in which LN2 is used as a moisture trap for gaseous hydrogen. ?? This article not subject to U.S. Copyright. Published 2010 by the American Chemical Society.

Coplen, T. B.; Qi, H.

2010-01-01

348

Caution on the use of liquid nitrogen traps in stable hydrogen isotope-ratio mass spectrometry.  

PubMed

An anomalous stable hydrogen isotopic fractionation of 4 in gaseous hydrogen has been correlated with the process of adding liquid nitrogen (LN(2)) to top off the dewar of a stainless-steel water trap on a gaseous hydrogen-water platinum equilibration system. Although the cause of this isotopic fractionation is unknown, its effect can be mitigated by (1) increasing the capacity of any dewars so that they do not need to be filled during a daily analytic run, (2) interspersing isotopic reference waters among unknowns, and (3) applying a linear drift correction and linear normalization to isotopic results with a program such as Laboratory Information Management System (LIMS) for Light Stable Isotopes. With adoption of the above guidelines, measurement uncertainty can be substantially improved. For example, the long-term (months to years) ?(2)H reproducibility (1? standard deviation) of nine local isotopic reference waters analyzed daily improved substantially from about 1 to 0.58 . This isotopically fractionating mechanism might affect other isotope-ratio mass spectrometers in which LN(2) is used as a moisture trap for gaseous hydrogen. PMID:20718408

Coplen, Tyler B; Qi, Haiping

2010-09-15

349

Molecular and stable isotope compositions of natural gas hydrates: A revised global dataset and basic interpretations in the context of geological settings  

Microsoft Academic Search

A global dataset of molecular and stable isotope compositions of gases released from 209 different specimens of natural gas hydrate is presented and discussed. The 26 hydrate-bearing areas from 21 geographic regions are grouped into high gas flux (HGF) settings, low gas flux (LGF) settings and hydrated gas accumulations (HGA). Methane (CH4) is the most abundant hydrate-bound gas, while CO2

Alexei V. Milkov

2005-01-01

350

Rapidly assessing changes in bone mineral balance using natural stable calcium isotopes  

PubMed Central

The ability to rapidly detect changes in bone mineral balance (BMB) would be of great value in the early diagnosis and evaluation of therapies for metabolic bone diseases such as osteoporosis and some cancers. However, measurements of BMB are hampered by difficulties with using biochemical markers to quantify the relative rates of bone resorption and formation and the need to wait months to years for altered BMB to produce changes in bone mineral density large enough to resolve by X-ray densitometry. We show here that, in humans, the natural abundances of Ca isotopes in urine change rapidly in response to changes in BMB. In a bed rest experiment, use of high-precision isotope ratio MS allowed the onset of bone loss to be detected in Ca isotope data after about 1 wk, long before bone mineral density has changed enough to be detectable with densitometry. The physiological basis of the relationship between Ca isotopes and BMB is sufficiently understood to allow quantitative translation of changes in Ca isotope abundances to changes in bone mineral density using a simple model. The rate of change of bone mineral density inferred from Ca isotopes is consistent with the rate observed by densitometry in long-term bed rest studies. Ca isotopic analysis provides a powerful way to monitor bone loss, potentially making it possible to diagnose metabolic bone disease and track the impact of treatments more effectively than is currently possible.

Morgan, Jennifer L. L.; Skulan, Joseph L.; Gordon, Gwyneth W.; Romaniello, Stephen J.; Smith, Scott M.; Anbar, Ariel D.

2012-01-01

351

Food web dynamics in the Scotia Sea in summer: A stable isotope study  

NASA Astrophysics Data System (ADS)

The pelagic food web of the Scotia Sea was studied by analysing natural abundances of nitrogen and carbon stable isotopes of primary producers and pelagic consumers, sampled from the seasonal ice edge in the south to the Antarctic Polar Front in the north. The analysis covered, within a single mid-summer period, particulate organic matter (POM) and 38 taxa, ranging from suspension feeding copepods and salps to omnivorous euphausiids, pelagic fish and higher, land-based predators including fur seals, penguins and flying birds. Spatial variation in ? 15N of POM correlated well with nutrient availability and primary productivity. Latitudinal differences in ? 13C of POM were closely linked to variations in temperature, nutrients and productivity depending on the frontal region sampled. This translated to equivalent (although smaller) regional ? 13C differences among higher trophic levels. The trophic positions of species based on isotope values broadly agreed with previously published dietary data with three important exceptions. First, the carnivorous amphipod Themisto gaudichaudii had anomalously low ? 15N values. Second, Euphausia superba had ? 15N values that were also surprisingly low, considering the abundant literature suggesting its omnivory. Third, the copepod Rhincalanus gigas, considered a suspension feeder, had unexpectedly high ? 15N values rather more in keeping with omnivorous feeding. The consumer ? 15N values ranged from 1.2 (min.) measured in Salpa thompsoni (designated here as trophic level (TL) 2 across all regions) to 15.2 (max.) measured in white-chinned petrels ( Procellaria aequinoctialis, calculated as TL5 relative to the TL2 of salps). Excluding seabirds, the resulting food chain length of 3.7 TL (above POM at TL1) was lower than in most other Southern Ocean and temperate marine pelagic ecosystems. The majority (60%) of vertebrate predators occupied only 1-1.5 trophic levels above the herbivorous suspension feeders such as krill. This indicates the existence of the classic short food chain of POM-suspension feeder-vertebrate predator. However the presence of trophic levels 4 and above indicates the existence of alternative trophic pathways, for example involving myctophid fish or carrion, and that some wide-ranging predators which breed at South Georgia also feed outside the region. This conclusion is supported first by the continuum of ? 15N values between krill, suspension feeding copepods and myctophid fish, and secondly by higher trophic levels in several of the myctophid species in the low-krill region of the northern Scotia Sea, suggesting latitudinal differences in food web structure and food chain length.

Stowasser, G.; Atkinson, A.; McGill, R. A. R.; Phillips, R. A.; Collins, M. A.; Pond, D. W.

2012-01-01

352

Evaluation of stable tungsten isotopes in the resolved resonance region  

NASA Astrophysics Data System (ADS)

In the last decade benchmark experiments and simulations, together with newly obtained neutron cross section data, have pointed out deficiencies in evaluated data files of W isotopes. The role of W as a fundamental structural material in different nuclear applications fully justifies a new evaluation of 182, 183, 184, 186W neutron resonance parameters. In this regard transmission and capture cross section measurements on natural and enriched tungsten samples were performed at the GELINA facility of the EC-JRC-IRMM. A resonance parameter file used as input in the resonance shape analysis was prepared based on the available literature and adjusted in first instance to transmission data.

Emiliani, F.; Guber, K.; Kopecky, S.; Lampoudis, C.; Massimi, C.; Schillebeeckx, P.; Volev, K.

2013-03-01

353

Environmental Reconstruction of the Arctic middle Eocene using Stable Isotope Analyses of Terrestrial Substrates  

NASA Astrophysics Data System (ADS)

I report on reconstructions of key environmental attributes of the Arctic middle Eocene (circa 45 Ma) using stable isotope analyses of terrestrial substrates from Axel Heiberg Island. The field site, now located in the far north of Canada, was home to extensive forests of deciduous conifers living at approximately 83 degrees North latitude during the middle Eocene. Fossils of these trees and associated soils are known for their spectacular preservation. Here I describe my vision of the middle Eocene Arctic environment, including the lack of polar ice, the high relative humidity, high levels of soil methane production, site temperature, and patterns of seasonality. These estimates were generated from stable isotope studies of oxygen and hydrogen in fossil cellulose, carbon and oxygen in paleosol carbonate and hydrogen within lipid biomarkers. I also report on our recent advances in the understanding of the oxygen isotopic exchange specific to position within the cellulose molecule, and its implications for the interpretation of isotopic analyses of cellulose.

Jahren, A.

2006-05-01

354

Constraints on the Origin of Galactic Cosmic Rays from Direct Measurements of Isotopic and Elemental Abundances  

NASA Astrophysics Data System (ADS)

Recent measurements of galactic cosmic ray (GCR) isotopic and elemental abundances have resulted in constraints on models of the origin of GCRs. The measurement of ^{59}Ni by the Cosmic Ray Isotope Spectrometer (CRIS) on the NASA Advanced Composition Explorer (ACE) has shown that there must be >10^{5} years between nucleosynthesis and acceleration. Measurements of a range of isotope ratios, most importantly ^{22}Ne/^{20}Ne and ^{58}Fe/^{56}Fe, have shown that the composition is consistent with source material that is a mix of 80% ISM (with Solar System abundances) and 20% outflow from massive stars. Data from the Trans-Iron Galactic Element Recorder (TIGER) and the ACE-CRIS experiments both show that the ordering of refractory and volatile elements with atomic mass is greatly improved when compared to an 80%/20% mix rather than pure ISM, that they have similar slopes, and that refractory elements are preferentially accelerated by a factor of 4 over volatile elements. We discuss these observations and conclude that our constraints are consistent with a GCR origin in OB associations. This research was supported by NASA under Grants NNX08AI11G and NNX09AC17G, and by NSF under Grant 0807356

Rauch, Brian

2012-07-01

355

Steppe bison paleobiology through the scope of stable isotopes and zooarchaeology  

NASA Astrophysics Data System (ADS)

Bison are one of the most abundant and widely distributed species of large mammal during the Late Pleistocene. In the southern steppes of Eastern Europe, steppe bison (Bison priscus) is ubiquitous in zooarchaeological assemblages, particularly during the Upper Palaeolithic when a model of economic "specialization" is proposed. Specialization, in this context, implies the deliberate selection of a preferred species, which becomes the key food resource. The applicability of a specialised hunting model for the Upper Palaeolithic of Europe has recently been challenged, however (Grayson & Delpech 2002). In this research, therefore we re-examine bison acquisition strategies during the Upper Palaeolithic in the Ukrainian steppes in the light of biogeochemical and zooarchaeological data. The acquisition strategies used to procure a prey species are directly related to its social and spatial behaviour. A synthesis of ethological information for contemporary bison (Julien 2009) demonstrates the behavioural diversity of this taxa, linked mainly to local environmental variability, climatic conditions and population density. It is therefore necessary to propose a paleoethological model for the steppe bison before attempting to identify the acquisition strategies used by prehistoric hunters. In this research, we reconstruct the behaviour of the steppe bison using a combination of zooarchaeological tools, stable isotope analysis (intra-tooth isotope variation of carbon, oxygen and strontium ratios) and traditional paleobiological approaches. The advantages of using a combined approach are demonstrated through the examination of a case study: the site of Amvrosievka (Ukraine). Amvrosievka is a complex of Epigravettian sites composed of a camp and kill site, where more than 500 bison are represented (Krotova & Belan 1993). Twenty-five permanent lower teeth (M3) representing twenty-five individual bison were selected from the kill and camp site for isotopic analysis. Intra- and inter-individual variations of ?18O from the enamel carbonate were analysed in order to track seasonal temperatures changes; the 87Sr/86Sr ratio was examined to determine the spatial behaviour of the animals and ?13C was used to examine changes in diet. The relatively large number of individuals represented in this study allowed us to interpret the resulting data in terms of intra-populational variability. In addition to the isotopic analysis, zooarchaeological study of a recently excavated portion of the kill site enabled us to determine the age at death and sex-ratio of the kill-population as well as examine patterns of carcass treatment. We use the combined information from the isotopic and zooarchaeological analyses to reconstruct the social composition of the herds, their spatial behaviour, seasonality and the existence of different sub-herds through the identification of different isotopic groups. Ultimately, we are able to suggest that the site represents a palimpsest of different hunting episodes. Finally, the impact of steppe bison palaeoethology on the choice of hunting strategy and subsistence economy of the Epigravettian occupants of Amvrosievka is examined. The non migratory behaviour of steppe bison in the study region is shown to have affected the season of acquisition as well as the hunting and butchering strategies developed by the Epigravettians. The combined paleoethological and palethnographical reconstruction offered here has direct implications for understanding the relative contribution of hunting pressure vs climatic change in the demise of the "mammoth steppe" faunas at the end of the Late Pleistocene. Cited references: Grayson D. & F. Delpech, 2002. Specialized Early Upper Palaeolithic Hunters in Southwestern France ? Journal of Archaeological Science, 29, p. 1439-1449. Julien M. A., 2009. Chasseurs de bisons - Apports de l'archozoologie et de la biogochimie isotopique l'tude palethnographique et palothologique du gisement pigravettien d'Amvrosievka (Ukraine), PhD Thesis, Universit de Mont

Julien, Marie-Anne; Dorothe, Drucker; Herv, Bocherens; Ariane, Burke; Marylne, Patou-Mathis; Alexandra, Krotova

2010-05-01

356

Microbe forensics: Oxygen and hydrogen stable isotope ratios in Bacillus subtilis cells and spores  

PubMed Central

Bacillus subtilis, a Gram-positive, endospore-forming soil bacterium, was grown in media made with water of varying oxygen (?18O) and hydrogen (?D) stable isotope ratios. Logarithmically growing cells and spores were each harvested from the cultures and their ?18O and ?D values determined. Oxygen and hydrogen stable isotope ratios of organic matter were linearly related with those of the media water. We used the relationships determined in these experiments to calculate the effective whole-cell fractionation factors between water and organic matter for B. subtilis. We then predicted the ?18O and ?D values of spores produced in nutritionally identical media and local water sources for five different locations around the United States. Each of the measured ?18O and ?D values of the spores matched the predicted values within a 95% confidence interval, indicating that stable isotope ratio analyses may be a powerful tool for tracing the geographic point-of-origin for microbial products.

Kreuzer-Martin, Helen W.; Lott, Michael J.; Dorigan, Janet; Ehleringer, James R.

2003-01-01

357

Stable isotope-labeling studies in metabolomics: new insights into structure and dynamics of metabolic networks  

PubMed Central

The rapid emergence of metabolomics has enabled system-wide measurements of metabolites in various organisms. However, advances in the mechanistic understanding of metabolic networks remain limited, as most metabolomics studies cannot routinely provide accurate metabolite identification, absolute quantification and flux measurement. Stable isotope labeling offers opportunities to overcome these limitations. Here we describe some current approaches to stable isotope-labeled metabolomics and provide examples of the significant impact that these studies have had on our understanding of cellular metabolism. Furthermore, we discuss recently developed software solutions for the analysis of stable isotope-labeled metabolomics data and propose the bioinformatics solutions that will pave the way for the broader application and optimal interpretation of system-scale labeling studies in metabolomics.

Chokkathukalam, Achuthanunni; Kim, Dong-Hyun; Barrett, Michael P; Breitling, Rainer; Creek, Darren J

2014-01-01

358

A stable isotope aridity index for terrestrial environments.  

PubMed

We use the oxygen isotopic composition of tooth enamel from multiple mammalian taxa across eastern Africa to present a proxy for aridity. Here we report tooth enamel delta(18)O values of 14 species from 18 locations and classify them according to their isotopic sensitivity to environmental aridity. The species are placed into two groups, evaporation sensitive (ES) and evaporation insensitive (EI). Tooth enamel delta(18)O values of ES animals increase with aridity, whereas the tooth enamel delta(18)O values of EI animals track local meteoric water delta(18)O values, demonstrating that bioapatite delta(18)O values of animals with different behaviors and physiologies record different aspects of the same environment. The enrichment between tooth enamel delta(18)O values of ES and EI animals records the degree of (18)O enrichment between evaporated water (ingested water or body water) and source water, which increases with environmental aridity. Recognition of the ES-EI distinction creates the opportunity to use the (18)O composition of bioapatite as an index of terrestrial aridity. PMID:16840554

Levin, Naomi E; Cerling, Thure E; Passey, Benjamin H; Harris, John M; Ehleringer, James R

2006-07-25

359

Disentangling a rainforest food web using stable isotopes: dietary diversity in a species-rich ant community.  

PubMed

For diverse communities of omnivorous insects such as ants, the extent of direct consumption of plant-derived resources vs. predation is largely unknown. However, determination of the extent of "herbivory" among ants may be crucial to understand the hyper-dominance of ants in tropical tree crowns, where prey organisms tend to occur scarcely and unpredictably. We therefore examined N and C stable isotope ratios (delta(15)N and delta(13)C) in 50 ant species and associated insects and plants from a tropical rainforest in North Queensland, Australia. Variation between ant species was pronounced (range of species means: 7.1 per thousand in delta(15)N and 6.8 per thousand in delta(13)C). Isotope signatures of the entire ant community overlapped with those of several herbivorous as well as predacious arthropods. Variability in delta(15)N between ants was not correlated with plant delta(15)N from which they were collected. Ant species spread out in a continuum between largely herbivorous and purely predacious taxa, with a high degree of omnivory. Ant species' delta(15)N were consistent with the trophic level predicted by natural feeding observations, but not their delta(13)C. Low delta(15)N levels were recorded for ant species that commonly forage for nectar on understorey or canopy plants, intermediate levels for species with large colonies that were highly abundant on nectar and honeydew sources and were predacious, and the highest levels for predominantly predatory ground-foraging species. Colonies of the dominant weaver-ants (Oecophylla smaragdina) had significantly lower delta(15)N in mature forests (where preferred honeydew and nectar sources are abundant) than in open secondary vegetation. N concentration of ant dry mass showed only very limited variability across species and no correlation with trophic levels. This study demonstrates that stable isotopes provide a powerful tool for quantitative analyses of trophic niche partitioning and plasticity in complex and diverse tropical omnivore communities. PMID:12898386

Blthgen, Nico; Gebauer, Gerhard; Fiedler, Konrad

2003-11-01

360

Production cross section of neutron-rich isotopes with radioactive and stable beams  

NASA Astrophysics Data System (ADS)

The production cross section of neutron-rich isotopes of Ca, Zn, Te, Xe, and Pt are predicted in the diffusive multinucleon transfer reactions with stable and radioactive beams. With these isotopes one can treat the neutron shell evolution beyond N =28, 50, 82, and 126. Because of the small cross sections, the production of nuclei near the neutron drip line requires the optimal choice of reaction partners and bombarding energies.

Mun, Myeong-Hwan; Adamian, G. G.; Antonenko, N. V.; Oh, Yongseok; Kim, Youngman

2014-03-01

361

Linking breeding and wintering grounds of neotropical migrant songbirds using stable hydrogen isotopic analysis of feathers  

Microsoft Academic Search

Recent studies have shown that stable hydrogen isotope ratios (?D) in the tissues of animals often correlate with ?D of local\\u000a precipitation. Here we examined the relationship between ?D in feathers and growing season precipitation for neotropical migrant\\u000a songbirds breeding over a continent-wide isotopic gradient. ?D values were determined on feathers of 140 individuals of 6\\u000a species of wild insectivorous

K. A. Hobson; Leonard I. Wassenaar

1996-01-01

362

Mid-Holocene Climate Reconstruction by Analysis of Growth Increments and Stable Isotopes of Marine Bivalves  

Microsoft Academic Search

Climate records constructed from growth increment and stable isotope analyses of modern and fossil mollusks from the north coast of Peru provide a high-resolution proxy for interannual sea surface temperature (SST) oscillations. Oxygen isotopes were measured in fossil and modern mollusk shells along the axes of maximum growth. Acetate peels of shell cross-sections record daily and semi-daily growth increments. The

S. D. Houk; K. A. Maasch; D. H. Sandweiss

2001-01-01

363

Stable carbon isotope ratio analyses on trace methane from ice samples  

Microsoft Academic Search

Measurement of the concentration and stable isotope ratios of methane from air enclosures in ancient ice can aid in understanding the temporal dynamics of methane sources and sinks. These measurements can reconstruct past atmospheric compositions on scales of tens-to-hundreds of years with adequate precision and accuracy. We present an improved micro-extraction gas-chromatography continuous-flow isotope ratio mass spectrometer (CF-IRMS) method to

Joe R. Melton; Michael J. Whiticar; Paul Eby

2011-01-01

364

Organic Matter Stable Isotope (? 13 C, ? 15 N) Response to Historical Eutrophication of Lake Taihu, China  

Microsoft Academic Search

We explored the use of carbon and nitrogen isotope ratios (?13C, ?15N) in sediment organic matter as proxy indicators of historical changes in the trophic state of Lake Taihu, the third largest\\u000a freshwater lake in China. Stable isotope signatures in four sediment cores spanning the 20th century were compared with instrumental\\u000a records of lake-water trophic state. The comparative study shows

Jinglu Wu; Lin Lin; Michael K. Gagan; Gerhard H. Schleser; Sumin Wang

2006-01-01

365

Fluid regimes in the deformation of the Helvetic nappes, Switzerland, as inferred from stable isotope data  

Microsoft Academic Search

The stable isotope composition of veins, pressure shadows, mylonites and fault breccias in allochthonous Mesozoic carbonate cover units of the Helvetic zone show evidence for concurrent closed and open system of fluid advection at different scales in the tectonic development of the Swiss Alps. Marine carbonates are isotopically uniform, independent of metamorphic grade, where d13C=1.51.5 (1 s) and d18O=25.42.2 (1

Martin Burkhard; Robert Kerrich

1988-01-01

366

Changes in biomarker abundances and sulfur isotopes of pyrite across the Permian Triassic (P/Tr) Schuchert Dal section (East Greenland)  

NASA Astrophysics Data System (ADS)

In this study, we report on biomarker abundances through parts of the Permian/Triassic boundary (PTB) of Schuchert Dal (East Greenland) that contains rich marine faunal records and excellent terrestrial palynological records. Biomarker abundances and sulfur isotopes are used to correlate the series of events (including changes in element cycling and associated redox conditions of the ocean) surrounding the collapse of the marine and terrestrial ecosystems through this record of a major crisis of life on Earth during a mass extinction episode. The Upper Schuchert Dal Formation contains a low diversity palynological assemblage, ascribed to arborescent cordiaite-conifer-pteridosperm vegetation. Samples from this pre-collapse interval are characterised by high abundances of dibenzofuran (DBF), dibenzothiophene (DBT) and biphenyl. Since these compounds have similar base structures, and show comparable abundance curves, it is plausible that they probably derive from a common source. We propose that phenolic compounds of lignin of the woody plants present during this period could be the source for DBF, DBT and biphenyl. The redox conditions during this period of time also support the formation of DBF and DBT. Just above the extinction interval, there is a dramatic decrease in the abundances of DBF and DBT which occurs at the same time as a sudden change in the stable sulfur isotopic composition ( ?34S) of pyrite, indicating a change in redox conditions from oxic to anoxic/euxinic conditions. ?34S values leading up to the extinction are highly depleted in the heavy sulfur isotope (about - 40 vs. VCDT), whilst shortly after the extinction interval much more positive isotope values are observed (about - 25). An inferred change in the biogeochemical sulfur cycle is supported by facies evidence from similar neighbouring sections. It is suggested that two processes are operating closely here; 1) Changes in redox conditions and 2) extinction and/or transgression accounting for the absence of woody material.

Fenton, Stephen; Grice, Kliti; Twitchett, Richard J.; Bttcher, Michael E.; Looy, Cindy V.; Nabbefeld, Birgit

2007-10-01

367

Stable isotope evolution and paleolimnology of ancient Lake Creede  

USGS Publications Warehouse

The lacustrine carbonate and travertine (tufa) deposits of ancient Lake Creede preserve a remarkable record of the isotopic evolution of the lake. That record indicates that the ?18O of the lake water, and by analogy its salinity, evolved through evaporation. Limited ans less reliable data on hydrous minerals and fluid inclusions in early diagenetic carbonates indicate that the ?D of the lake waters also evolved through evaporation. The isotope data place restrictions on models of the physical limnology of the lake and its evolution. The closed-basin Lake Creede formed shortly after collapse of the 26.9 Ma Creede caldera. Throughout most of its history it occupied the northern three quarters of the moat between the resurgent dome and wall of the caldera. The Creede Formation was deposited in the basin, dominantly as lacustrine sediments. Travertine mounds interfinger with Creede Formation sediments along the inner and outer margins of the lake basin. An estimated one-half of the original thickness of the Creede Formation has been lost mainly to erosion although scattered remnants of the upper portion remain on the caldera walls. Two diamond core holes (CCM-1 and CCM-2) sampled the uneroded portion of the Creede Formation as part of the U.S. Continental Drilling Program. Volcaniclastic material, including tuff units deposited directly into the lake and ash washed in from the watershed, compose the main lithologies of the Creede Formation. These volcaniclastic strata were produced by episodic ring-fracture volcanism. Lacustrine carbonates make up about 15% of the section sampled by drill core. They occur as 1 mm to 2 cm low-Mg calcite laminar alternating with siliciclastic laminar in scattered intervals throughout the preserved section. The carbonate laminar are accumulations of 5-20 ?m crystallites (microparites) and brine shrimmp fecal pellets (peloids) composed mainly of microparasite particles. Low-Mg calcite also occurs as an early diagenetic replacement of gypsum or ikaite (CaCO3 6H2O) crystals grown displacively in the muds and silts neat the water-sediment interface (rice grains). Other studies indicate that aragonite was the original CaCO3 precipitate forming the microsparite and pelodial laminae and that it converted to calcite suring burual diagenesis. Samples from CCM-2 and nearby outcrop do not appear to have undergone significant isotope exchange during recrystallization. Samples from CCM-1 and nearby outcrop, however, appear to have undergone extensive oxygen isotope exchange with meteoric water-dominated fluids possibly during a local 17.6 Ma hydrothermal event. The ?18-?13C data set produced by microsampling of individual carbonate lamellae and rice grains is exceptional in several aspects and provides important clues concerning the evolution of limnologic structure of the lake and its chemical and isotopic composition. Travertine and ikaite pseudomorphs in travertine deposits extendthe record an additional 330m above the collar of CCM-2. The ?18O values on the CCM-2 samples range from 10.4% to 37.3% and ?13C values range from -10.8% to 9.6%. The data fall into two distinct groups, a covariant group and an invariant group. The covariant group shows a strong negative covariance and a large range of ?18O and ?13C values. The negative covariance is opposite that normally reported for lacustrine carbonates. The large range of ?18O and ?13C values requires that the carbonates precipitated from waters have a large range of temperature and carbon and oxygen isotopic composition. The invariant group has a narrow range of large ?18O values (35% to 2%) and a wide range of ?13C values (-10.8% to 9.6%), indicating precipitation from waters with a narrow range of temperature and ?18O but a wide range of in ?13C of aqueous carbon. The ranges of isotope values for microsparite and peloid samples are virtually identical; two-thirds are in the covariant group. By contrast, the values for almost all rice grain samples are in the in

Rye, Robert O.; Bethke, Philip M.; Finkelstein, David B.

2000-01-01

368

Recent developments in application of stable isotope analysis on agro-product authenticity and traceability.  

PubMed

With the globalisation of agro-product markets and convenient transportation of food across countries and continents, the potential for distribution of mis-labelled products increases accordingly, highlighting the need for measures to identify the origin of food. High quality food with identified geographic origin is a concern not only for consumers, but also for agriculture farmers, retailers and administrative authorities. Currently, stable isotope ratio analysis in combination with other chemical methods gradually becomes a promising approach for agro-product authenticity and traceability. In the last five years, a growing number of research papers have been published on tracing agro-products by stable isotope ratio analysis and techniques combining with other instruments. In these reports, the global variety of stable isotope compositions has been investigated, including light elements such as C, N, H, O and S, and heavy isotopes variation such as Sr and B. Several factors also have been considered, including the latitude, altitude, evaporation and climate conditions. In the present paper, an overview is provided on the authenticity and traceability of the agro-products from both animal and plant sources by stable isotope ratio analysis. PMID:24128481

Zhao, Yan; Zhang, Bin; Chen, Gang; Chen, Ailiang; Yang, Shuming; Ye, Zhihua

2014-02-15

369

Stable-isotope record of organic carbon from an evolving carbonate banktop, Bight of Abaco, Bahamas  

NASA Astrophysics Data System (ADS)

The stable-isotope composition (?13C) of total organic carbon (TOC) was measured as a function of depth throughout a 217-cm-thick sequence of Holocene carbonate sediment within the Bight of Abaco lagoon, Little Bahama Bank. Biofacies and lithofacies analyses indicate progressive banktop submergence and paleoenvironmental response during Holocene sea-level rise. Stable-isotope values shift markedly from -27.7 within the 7900 B.P. paleosol at the base of the core to -11.1 at the present-day sediment-water interface. An abrupt excursion toward heavy-isotope values records the first establishment of Thalassia seagrass upon open-marine flooding. A multitracer approach, combining biofacies, lithofacies, and stable-isotope analysis of TOC confirms that the dramatic +17 shift observed in ?13C was a direct result of sea-level rise and associated environmental changes over the banktop; there is little evidence of spurious diagenetic overprint. Stable-isotope analyses of organic carbon may enhance the reconstruction of carbonate sequences by revealing a distinctive geochemical signature of banktop flooding, including the onset of growth of otherwise unpreservable Thalassia seagrass.

Rasmussen, Kenneth A.; Haddad, Robert I.; Neumann, A. Conrad

1990-08-01

370

Stable-isotope record of organic carbon from an evolving carbonate banktop, Bight of Abaco, Bahamas  

SciTech Connect

The stable-isotope composition ({delta}{sup 13}C) of total organic carbon (TOC) was measured as a function of depth throughout a 217-cm-thick sequence of Holocene carbonate sediment within the Bight of Abaco lagoon, Little Bahama Bank. Biofacies and lithofacies analyses indicate progressive banktop submergence and paleoenvironmental response during Holocene sea-level rise. Stable-isotope values shift markedly from {minus}27.7{per thousand} within the 7900 B.P. paleosol at the base of the core to {minus}11.1{per thousand} at the present-day sediment-water interface. An abrupt excursion toward heavy-isotope values records the first establishment of Thalassia seagrass upon open-marine flooding. A multitracer approach, combining biofacies, lithofacies, and stable-isotope analysis of TOC confirms that the dramatic +17{per thousand} shift observed in {delta}{sup 13}C was a direct result of sea-level rise and associated environmental changes over the banktop; there is little evidence of spurious diagenetic overprint. Stable-isotope analyses of organic carbon may enhance the reconstruction of carbonate sequences by revealing a distinctive geochemical signature of banktop flooding, including the onset of growth of otherwise unpreservable Thalassia seagrass.

Rasmussen, K.A.; Neumann, A.C. (Univ. of North Carolina, Chapel Hill (USA)); Haddad, R.I. (NASA-Ames Research Center, Moffett Field, CA (USA))

1990-08-01

371

Influence of regional precipitation patterns on stable isotopes in ice cores from the central Himalayas  

NASA Astrophysics Data System (ADS)

Several ice cores have been recovered from the Dasuopu Glacier and the East Rongbuk (ER) Glacier in the central Himalayas since the 1990s. Although the distance between the ER and the Dasuopu ice core drilling sites is only ∼125 km, the stable isotopic record (?18O or ?D) of the ER core is interpreted as a precipitation proxy while the Dasuopu core as a temperature proxy. Thus, the climatological significance of the stable isotopic records of these Himalayan ice cores remains a subject of debate. Based on analysis of regional precipitation patterns over the region, we find that the different interpretations of the Dasuopu and Everest isotopic records may not be contradictive. The north-south and west-east seesaws of the Indian Summer Monsoon (ISM) precipitation are primarily responsible for precipitation falling at the ER site, which results in a negative correlation between the ER ?18O or ?D record and precipitation amount along the southern slope of the central Himalayas, corresponding to the "amount effect". In addition to the ISM precipitation, non-summer monsoonal precipitation associated with winter westerlies also significantly contributes to precipitation falling at the Dasuopu site, which may cause a positive correlation between the Dasuopu stable isotopic record and temperature, in response to the "temperature effect". Our results have important implications for interpreting the stable isotopic ice core records recovered from different climatological regimes of the Himalayas.

Pang, H.; Hou, S.; Kaspari, S.; Mayewski, P. A.

2013-05-01

372

Influence of regional precipitation patterns on stable isotopes in ice cores from the central Himalayas  

NASA Astrophysics Data System (ADS)

Several ice cores have been recovered from the Dasuopu (DSP) Glacier and the East Rongbuk (ER) Glacier in the central Himalayas since the 1990s. Although the distance between the DSP and the ER ice core drilling sites is only ~ 125 km, the stable isotopic record (?18O or ?D) of the DSP core is interpreted in previous studies as a temperature proxy, while the ER core is interpreted as a precipitation proxy. Thus, the climatological significance of the stable isotopic records of these Himalayan ice cores remains a subject of debate. Based on analysis of regional precipitation patterns over the region, we find that remarkable discrepancy in precipitation seasonality between the two sites may account for their disparate isotopic interpretations. At the ER core site, the Indian summer monsoon (ISM) precipitation is dominating due to topographic blocking of the moisture from westerlies by the high ridges of Mt. Qomolangma (Everest), which results in a negative correlation between the ER ?18O or ?D record and precipitation amount along the southern slope of the central Himalayas in response to the "amount effect". At the DSP core site, in comparison with the ISM precipitation, the wintertime precipitation associated with the westerlies is likely more important owing to its local favorable topographic conditions for interacting with the western disturbances. Therefore, the DSP stable isotopic record may be primarily controlled by the westerlies. Our results have important implications for interpreting the stable isotopic ice core records recovered from different climatological regimes of the Himalayas.

Pang, H.; Hou, S.; Kaspari, S.; Mayewski, P. A.

2014-02-01

373

Stream-water stable isotopes, moisture fluxes, complex topography and isotopic fractionation along the South Central Andes  

NASA Astrophysics Data System (ADS)

Stable-isotope data and modeling studies have focused on establishing a relationship between elevation and the ?18O and ?D of precipitation in order to interpret paleo-isotope data in terms of past moisture sources and changes in the distribution of rainfall. Far less is known about how local topographic features such as the height and relief of orographic barriers and/or valley geometry influence stable isotope fractionation by modulating moisture pathways. We establish regional characteristics of stable-isotopes in rainfall and stream water from NW Argentina, and quantify the impact of topography from different morphotectonic regions (e.g., broken foreland, fold and thrust belt, orogenic plateau) on the degree of isotopic fractionation. The Central Andes constitute a major orographic barrier to atmospheric circulation. Moisture-bearing air masses rise along their eastern flanks, leading to heavy convective rainfall during austral summer. We present results of the ?18O and ?D composition of water from 219 streams along three E-W transects between 22S and 28S, crossing several orographic barriers, intermontane basins and the Puna Plateau. Stream-water ?18O for the different segments ranges between - 3.6 to -6.7 (VSMOW) in the southern broken foreland, between -5.3 to -11.4 in the transition zone between the Subandes foreland-fold-and-thrust belt and the broken foreland, and between -6.1 to -11.6 in Subandes. In combination with TRMM-satellite derived rainfall and a thermodynamic model for the isotopic evolution of precipitation, our data reveal: (1) a strong N-S gradient in the effectiveness of isotopic fractionation in relation to different topographic configurations of the orographic front and plateau flank, resulting in a two- to three-fold difference in the efficiency of rainwater isotopic fractionation ; (2) a strong relationship between the isotopic signal and elevation along the wedge topography of the Subandes, contrasting with a weak relationship in the complex topography of the broken foreland system, due to the characteristics of moisture pathways through the intermontane basin zone; (3) a "critical" orographic barrier that forces an additional 50% rain-out of the remaining moisture behind the first orographic barrier to the east of the Puna and an orographic barrier threshold elevation between 2 to 2.5 km; and (4) an unequal distribution of catchment rainfall, resulting in a deviation from expected catchment isotopic values. Thus, in addition to different moisture sources, complex topography significantly modifies modern stable-isotope values. The influence of the topographic pathway is most pronounced in the broken-foreland province, which provides multiple pathways for moisture to penetrate into the orogen, resulting in poor correlations between isotopic fractionation and elevation. In contrast, the laterally-continuous orographic ramp of the Subandes yields strong correlations between isotopic fractionation and elevation. Therefore, isotopic records derived from soil-carbonates, plant-biomarkers, volcanic glass, and teeth in areas with similar complex topography may be problematic in reflecting elevation changes and tracking the tectonic build up of orography.

Rohrmann, A.; Strecker, M. R.; Clarke, B. A.; Bookhagen, B.; Mulch, A.; Sachse, D.

2012-12-01

374

Determination of Key Intermediates in Cholesterol and Bile Acid Biosynthesis by Stable Isotope Dilution Mass Spectrometry  

PubMed Central

For more than a decade, we have developed stable isotope dilution mass spectrometry methods to quantify key intermediates in cholesterol and bile acid biosynthesis, mevalonate and oxysterols, respectively. The methods are more sensitive and reproducible than conventional radioisotope (RI), gas-chromatography (GC) or high-performance liquid chromatography (HPLC) methods, so that they are applicable not only to samples from experimental animals but also to small amounts of human specimens. In this paper, we review the development of stable isotope dilution mass spectrometry for quantifying mevalonate and oxysterols in biological materials, and demonstrate the usefulness of this technique.

Yoshida, Tadashi; Honda, Akira; Miyazaki, Hiroshi; Matsuzaki, Yasushi

2008-01-01

375

Stable isotope analysis of the karst hydrological systems in the Bay of Kvarner (Croatia).  

PubMed

Here we present the results of the first systematic analysis of the stable isotope composition of the karst hydrological systems in the Bay of Kvarner. Gaussian mixture modelling, time series analysis and autoregressive integrated moving average (ARIMA) modelling were applied using the stable isotope compositions of the karst groundwater. This study revealed that the recharge is dominated by winter precipitation, the dual-porosity system is dominated by baseflow, the hinterlands of the individual springs have different degrees of karstification and the springs within the Rje?ina River catchment have higher recharge elevations than the springs in the Bakar Bay catchment. PMID:24681429

Mance, D; Hunjak, T; Lenac, D; Rubini?, J; Roller-Lutz, Z

2014-08-01

376

Stable Isotope Analysis of Precipitation Samples Obtained via Crowdsourcing Reveals the Spatiotemporal Evolution of Superstorm Sandy  

PubMed Central

Extra-tropical cyclones, such as 2012 Superstorm Sandy, pose a significant climatic threat to the northeastern United Sates, yet prediction of hydrologic and thermodynamic processes within such systems is complicated by their interaction with mid-latitude water patterns as they move poleward. Fortunately, the evolution of these systems is also recorded in the stable isotope ratios of storm-associated precipitation and water vapor, and isotopic analysis provides constraints on difficult-to-observe cyclone dynamics. During Superstorm Sandy, a unique crowdsourced approach enabled 685 precipitation samples to be obtained for oxygen and hydrogen isotopic analysis, constituting the largest isotopic sampling of a synoptic-scale system to date. Isotopically, these waters span an enormous range of values (21 for O, 160 for H) and exhibit strong spatiotemporal structure. Low isotope ratios occurred predominantly in the west and south quadrants of the storm, indicating robust isotopic distillation that tracked the intensity of the storm's warm core. Elevated values of deuterium-excess (25) were found primarily in the New England region after Sandy made landfall. Isotope mass balance calculations and Lagrangian back-trajectory analysis suggest that these samples reflect the moistening of dry continental air entrained from a mid-latitude trough. These results demonstrate the power of rapid-response isotope monitoring to elucidate the structure and dynamics of water cycling within synoptic-scale systems and improve our understanding of storm evolution, hydroclimatological impacts, and paleo-storm proxies.

Good, Stephen P.; Mallia, Derek V.; Lin, John C.; Bowen, Gabriel J.

2014-01-01

377

Redox-driven stable isotope fractionation in transition metals: Application to Zn electroplating  

NASA Astrophysics Data System (ADS)

Redox processes are ubiquitous in Earth science and are often associated with large isotope fractionations. In a previous study, voltage-dependent amplification of stable isotope fractionation was observed for an Fe reduction process. Here, we describe experiments showing a similar effect for a second transition metal, zinc. After electrochemical reduction, the composition of plated Zn metal is enriched in the light isotope ( 64Zn) with respect to the Zn 2+ leftover in solution, with a voltage-dependent fractionation factor. Results from voltage-dependent electroplating experiments are in good agreement with a second data set following equilibrium fractional isotope evolution of Zn isotopes during an electroplating process which stepwise removes most of the Zn from the aqueous reservoir. Taken together, the results indicate a voltage-dependent isotope fractionation (in permil) of 66Zn with respect to 64Zn to be equal to -3.45 to 1.71 V. The negative slope trend is in contrast with previously published results on iron isotope fractionation during electroplating which shows a positive slope. These results are interpreted using an extension of Marcus theory, which predicts isotope fractionations as a function of driving force in an electrochemical system. Taken together with observations of natural fractionation of redox-sensitive and non redox-active elements, our modified Marcus theory provides a framework for quantitatively predicting transition metal isotope geochemical signatures during environmentally relevant redox processes in terms of simple energetic parameters.

Kavner, A.; John, S. G.; Sass, S.; Boyle, E. A.

2008-04-01

378

Stable isotope analysis of precipitation samples obtained via crowdsourcing reveals the spatiotemporal evolution of Superstorm Sandy.  

PubMed

Extra-tropical cyclones, such as 2012 Superstorm Sandy, pose a significant climatic threat to the northeastern United Sates, yet prediction of hydrologic and thermodynamic processes within such systems is complicated by their interaction with mid-latitude water patterns as they move poleward. Fortunately, the evolution of these systems is also recorded in the stable isotope ratios of storm-associated precipitation and water vapor, and isotopic analysis provides constraints on difficult-to-observe cyclone dynamics. During Superstorm Sandy, a unique crowdsourced approach enabled 685 precipitation samples to be obtained for oxygen and hydrogen isotopic analysis, constituting the largest isotopic sampling of a synoptic-scale system to date. Isotopically, these waters span an enormous range of values (> 21 for ?(18)O, > 160 for ?(2)H) and exhibit strong spatiotemporal structure. Low isotope ratios occurred predominantly in the west and south quadrants of the storm, indicating robust isotopic distillation that tracked the intensity of the storm's warm core. Elevated values of deuterium-excess (> 25) were found primarily in the New England region after Sandy made landfall. Isotope mass balance calculations and Lagrangian back-trajectory analysis suggest that these samples reflect the moistening of dry continental air entrained from a mid-latitude trough. These results demonstrate the power of rapid-response isotope monitoring to elucidate the structure and dynamics of water cycling within synoptic-scale systems and improve our understanding of storm evolution, hydroclimatological impacts, and paleo-storm proxies. PMID:24618882

Good, Stephen P; Mallia, Derek V; Lin, John C; Bowen, Gabriel J

2014-01-01

379

Analytical modelling of stable isotope fractionation of volatile organic compounds in the unsaturated zone  

NASA Astrophysics Data System (ADS)

Analytical models were developed that simulate stable isotope ratios of volatile organic compounds (VOCs) near a point source contamination in the unsaturated zone. The models describe diffusive transport of VOCs, biodegradation and source ageing. The mass transport is governed by Fick's law for diffusion. The equation for reactive transport of VOCs in the soil gas phase was solved for different source geometries and for different boundary conditions. Model results were compared to experimental data from a one-dimensional laboratory column and a radial-symmetric field experiment. The comparison yielded a satisfying agreement. The model results clearly illustrate the significant isotope fractionation by gas phase diffusion under transient state conditions. This leads to an initial depletion of heavy isotopes with increasing distance from the source. The isotope evolution of the source is governed by the combined effects of isotope fractionation due to vaporisation, diffusion and biodegradation. The net effect can lead to an enrichment or depletion of the heavy isotope in the remaining organic phase, depending on the compound and element considered. Finally, the isotope evolution of molecules migrating away from the source and undergoing degradation is governed by a combined degradation and diffusion isotope effect. This suggests that, in the unsaturated zone, the interpretation of biodegradation of VOC based on isotopic data must always be based on a model combining gas phase diffusion and degradation.

Bouchard, Daniel; Cornaton, Fabien; Hhener, Patrick; Hunkeler, Daniel

2011-01-01

380

Analytical modelling of stable isotope fractionation of volatile organic compounds in the unsaturated zone.  

PubMed

Analytical models were developed that simulate stable isotope ratios of volatile organic compounds (VOCs) near a point source contamination in the unsaturated zone. The models describe diffusive transport of VOCs, biodegradation and source ageing. The mass transport is governed by Fick's law for diffusion. The equation for reactive transport of VOCs in the soil gas phase was solved for different source geometries and for different boundary conditions. Model results were compared to experimental data from a one-dimensional laboratory column and a radial-symmetric field experiment. The comparison yielded a satisfying agreement. The model results clearly illustrate the significant isotope fractionation by gas phase diffusion under transient state conditions. This leads to an initial depletion of heavy isotopes with increasing distance from the source. The isotope evolution of the source is governed by the combined effects of isotope fractionation due to vaporisation, diffusion and biodegradation. The net effect can lead to an enrichment or depletion of the heavy isotope in the remaining organic phase, depending on the compound and element considered. Finally, the isotope evolution of molecules migrating away from the source and undergoing degradation is governed by a combined degradation and diffusion isotope effect. This suggests that, in the unsaturated zone, the interpretation of biodegradation of VOC based on isotopic data must always be based on a model combining gas phase diffusion and degradation. PMID:21056918

Bouchard, Daniel; Cornaton, Fabien; Hhener, Patrick; Hunkeler, Daniel

2011-01-25

381

Characterizing uranium oxide reference particles for isotopic abundances and uranium mass by single particle isotope dilution mass spectrometry.  

PubMed

Uranium and plutonium particulate test materials are becoming increasingly important as the reliability of measurement results has to be demonstrated to regulatory bodies responsible for maintaining effective nuclear safeguards. In order to address this issue, the Institute for Reference Materials and Measurements (IRMM) in collaboration with the Institute for Transuranium Elements (ITU) has initiated a study to investigate the feasibility of preparing and characterizing a uranium particle reference material for nuclear safeguards, which is finally certified for isotopic abundances and for the uranium mass per particle. Such control particles are specifically required to evaluate responses of instruments based on mass spectrometric detection (e.g. SIMS, TIMS, LA-ICPMS) and to help ensuring the reliability and comparability of measurement results worldwide. In this paper, a methodology is described which allows quantifying the uranium mass in single micron particles by isotope dilution thermal ionization mass spectrometry (ID-TIMS). This methodology is characterized by substantial improvements recently achieved at IRMM in terms of sensitivity and measurement accuracy in the field of uranium particle analysis by TIMS. The use of monodisperse uranium oxide particles prepared using an aerosol generation technique developed at ITU, which is capable of producing particles of well-characterized size and isotopic composition was exploited. The evidence of a straightforward correlation between the particle volume and the mass of uranium was demonstrated in this study. Experimental results have shown that the uranium mass per particle can be measured via the ID-TIMS method to a relative expanded uncertainty of about 10% (coverage factor k=2). The availability of reliable and validated methods for the characterization of uranium particles is considered to be essential for the establishment of SI-traceable measurement results. It is therefore expected that the method developed in this study is valuable for the certification of particulate materials in which the isotopic composition and the content of uranium must be accurately known. PMID:23021805

Kraiem, M; Richter, S; Erdmann, N; Khn, H; Hedberg, M; Aregbe, Y

2012-10-20

382

Micropowder collecting technique for stable isotope analysis of carbonates.  

PubMed

Micromilling is a conventional technique used in the analysis of the isotopic composition of geological materials, which improves the spatial resolution of sample collection for analysis. However, a problem still remains concerning the recovery ratio of the milled sample. We constructed a simple apparatus consisting of a vacuum pump, a sintered metal filter, electrically conductive rubber stopper and a stainless steel tube for transferring the milled powder into a reaction vial. In our preliminary experiments on carbonate powder, we achieved a rapid recovery of 5 to 100?g of carbonate with a high recovery ratio (>90%). This technique shortens the sample preparation time, improves the recovery ratio, and homogenizes the sample quantity, which, in turn, improves the analytical reproducibility. PMID:21488119

Sakai, Saburo; Kodan, Tsuyoshi

2011-05-15

383

Depletion of 13C in lignin and its implications for stable carbon isotope studies  

NASA Astrophysics Data System (ADS)

Stable carbon isotope compositions of organic matter are now widely used to trace carbon flow in ecosystems, and have been instrumental in shaping current perceptions of the importance of terrestrial vegetation to estuarine and coastal marine environments. A general assumption in these and other studies relying on carbon isotope compositions for source identification of organic matter has been that the major biochemical components of plant tissues are isotopically invariant. We report here large differences between the carbon isotope compositions of the polysaccharide and lignin components of a variety of vascular plants, including the salt-marsh grass Spartina alterniflora, and demonstrate that the carbon isotope composition of Spartina detritus gradually changes during biogeochemical processing as polysaccharides are preferentially removed, leaving a material that is relatively enriched in lignin-derived carbon and depleted in 13C.

Benner, Ronald; Fogel, Marilyn L.; Sprague, E. Kent; Hodson, Robert E.

1987-10-01