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1

Natural abundance variations in stable isotopes and their potential uses in animal physiological ecology.  

PubMed

Chemical, biological, and physical processes lead to distinctive "isotopic signatures" in biological materials that allow tracing of the origins of organic substances. Isotopic variation has been extensively used by plant physiological ecologists and by paleontologists, and recently ecologists have adopted the use of stable isotopes to measure ecosystem patterns and processes. To date, animal physiological ecologists have made minimal use of naturally occurring stable isotopes as tracers. Here we provide a review of the current and potential uses of naturally occurring stable isotopes in animal physiological ecology. We outline the physical and biological processes that lead to variation in isotopic abundance in plants and animals. We summarize current uses in animal physiological ecology (diet reconstruction and animal movement patterns), and suggest areas of research where the use of stable isotopes can be fruitful (protein balance and turnover and the allocation of dietary nutrients). We argue that animal physiological ecologists can benefit from including the measurement of naturally occurring stable isotopes in their battery of techniques. We also argue that animal physiologists can make an important contribution to the emerging field of stable isotopes in biology by testing experimentally the plethora of assumptions upon which the techniques rely. PMID:9683412

Gannes, L Z; Martnez del Rio, C; Koch, P

1998-03-01

2

Natural Abundance Variations in Stable Isotopes and their Potential Uses in Animal Physiological Ecology  

Microsoft Academic Search

Chemical, biological, and physical processes lead to distinctive isotopic signatures in biological materials that allow tracing of the origins of organic substances. Isotopic variation has been extensively used by plant physiological ecologists and by paleontologists, and recently ecologists have adopted the use of stable isotopes to measure ecosystem patterns and processes. To date, animal physiological ecologists have made minimal use

Leonard Z. Gannes; Carlos Mart??nez del Rio; Paul Koch

1998-01-01

3

Partitioning Respiration Fluxes in a Forested Mountainous Ecosystem Using Natural Abundance of Stable Carbon Isotopes  

NASA Astrophysics Data System (ADS)

Isotopic mass balance techniques can help overcome challenges to studying ecosystem fluxes in complex terrain. Because scaling up measurements made at the leaf level compounds and magnifies measurement errors, it is desirable that ecosystem fluxes be measured using an integrative technique, such as eddy covariance. However, advective forcing complicates the use of eddy covariance in complex terrain, so we used an isotopic mass balance approach to partition ecosystem respiration flux in a forested site in a mountainous region of northern Idaho, USA. In 2006 and 2007, we analyzed the carbon-13 composition (?13C) of ecosystem respiration and both the ?13C and magnitude of soil, foliar, and stem component fluxes of ecosystem respiration. Soil- and stem-respired ?13C values were similar, from -27.24 (2.63) (stem) to -26.9 (1.11) (soil). Foliar respiration was consistently more enriched by up to 8. We took advantage of nighttime advection to collect samples of air from the forest, then used a Keeling plot approach to determine the isotopic composition of respired CO2. Ecosystem-respired CO2 had a seasonal range from -27.3 (0.67) to -23.5 (1.0). Using a mixing model, we then determined a ratio of soil respiration to ecosystem respiration for the forest. We compared this ratio to a ratio obtained independently by scaling up soil, foliar, and stem respiration rate measurements to the forest level. This work shows that, in the absence of eddy covariance techniques, whole-ecosystem gas exchange can be examined using the natural abundance of stable isotopes. This approach can be further used to test the accuracy of ecosystem carbon models or scaling techniques.

Berryman, E. M.; Lpez, N. U.; Gag, P.; Kavanagh, K.; Marshall, J. D.

2008-12-01

4

[Humus composition and stable carbon isotope natural abundance in paddy soil under long-term fertilization].  

PubMed

Soil samples were collected from an experimental paddy field with long-term (26 years) fertilization in Taihu Lake region of Jiangsu Province to study the effects of different fertilization on the organic carbon distribution and stable carbon isotope natural abundance (delta 13C) in the soil profile, and on the humus composition. The results showed that long-term fertilization increased the organic carbon content in top soil significantly, and there was a significantly negative exponential correlation between soil organic carbon content and soil depth (P < 0.01). The organic carbon content in 10-30 cm soil layer under chemical fertilizations and in 20-40 cm soil layer under organic fertilizations was relatively stable. Soil delta 13C increased gradually with soil depth, its variation range being from -24% per thousand to -28 per thousand, and had a significantly negative linear correlation with soil organic carbon content (P < 0.05). In 0-20 cm soil layer, the delta 13C in treatments organic manure (M), M + NP, M + NPK, M + straw (R) + N, and R + N decreased significantly; while in 30-50 cm soil layer, the delta 13C in all organic fertilization treatments except R + N increased significantly. Tightly combined humus (humin) was the main humus composition in the soil, occupying 50% or more, and the rest were loosely and stably combined humus. Long-term fertilization increased the content of loosely combined humus and the ratio of humic acid (HA) to fulvic acid (FA). PMID:19102308

Ma, Li; Yang, Lin-Zhang; Ci, En; Wang, Yan; Yin, Shi-Xue; Shen, Ming-Xing

2008-09-01

5

Stable isotope research pool inventory  

NASA Astrophysics Data System (ADS)

A listing is presented of electromagnetically separated stable isotopes which are available for distribution within the United States for nondestructive research use from the Oak Ridge National Laboratory on a loan basis. This inventory includes all samples of stable isotopes in the Material Research Collection and does not designate whether a sample is out on loan or in reprocessing. For some of the high abundance naturally occurring isotopes, larger amounts can be made available.

1982-01-01

6

Stable isotope research pool inventory  

SciTech Connect

This report contains a listing of electromagnetically separated stable isotopes which are available at the Oak Ridge National Laboratory for distribution for nondestructive research use on a loan basis. This inventory includes all samples of stable isotopes in the Research Materials Collection and does not designate whether a sample is out on loan or is in reprocessing. For some of the high-abundance, naturally occurring isotopes, larger amounts can be made available; for example, Ca-40 and Fe-56.

Not Available

1988-02-01

7

Correcting for the effects of natural abundance in stable isotope resolved metabolomics experiments involving ultra-high resolution mass spectrometry  

Microsoft Academic Search

BACKGROUND: Stable isotope tracing with ultra-high resolution Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS) can provide simultaneous determination of hundreds to thousands of metabolite isotopologue species without the need for chromatographic separation. Therefore, this experimental metabolomics methodology may allow the tracing of metabolic pathways starting from stable-isotope-enriched precursors, which can improve our mechanistic understanding of cellular metabolism. However, contributions to the

Hunter N. B. Moseley

2010-01-01

8

Critique: measuring hydrogen stable isotope abundance of proteins to infer origins of wildlife, food and people.  

PubMed

Measurement of the relative abundance of (2)H (expressed in ?(2)H values) in tissues of plants, wildlife and people has evolved into a powerful forensic tool. The approach is based on the strong linkage between spatial patterns of ?(2)H values in precipitation at local and continental scales, and the tissues of plants and animals produced on these 'isoscapes'. Unfortunately, despite this exciting potential, difficulties inherent in the measurement of ?(2)H values in complex organic materials such as proteins, as well as the accuracy of such measurements, and a reluctance to adopt strict quality assurance/QC approaches to address challenges associated with these measurements, has clearly limited this potential. These challenges are entirely avoidable and techniques now exist for the routine reliable measurement of ?(2)H values in materials of forensic interest that will allow completely comparable data among laboratories. PMID:23534421

Meier-Augenstein, Wolfram; Hobson, Keith A; Wassenaar, Leonard I

2013-04-01

9

Stable isotope abundances ( 13C, 15N) in collagen and soft tissues from Pleistocene mammals from Yakutia: Implications for the palaeobiology of the Mammoth Steppe  

Microsoft Academic Search

A suite of skeletons and frozen carcasses of upper Pleistocene mammals from Yakutia (Sakha Republic, Russia) has been analyzed for their stable isotopic abundances in carbon and nitrogen. Results from bone collagen and soft tissues have been compared. The samples studied belong to herbivorous (mammoths, woolly rhinoceros, horse, bison, muskox) and carnivorous (wolf, lion) species. Bone collagen of herbivorous and

Herv Bocherens; Gilles Pacaud; Petr A. Lazarev; Andr Mariotti

1996-01-01

10

Nitrogen and carbon stable isotope abundances support the myco-heterotrophic nature and host-specificity of certain achlorophyllous plants  

Microsoft Academic Search

Summary Over 400 species of achlorophyllous vascular plants are thought to obtain all C from symbiotic fungi. Consequently, they are termed 'myco-heterotrophic.' However, direct evidence of myco-heterotrophy in these plants is limited. During an investigation of the patterns of N and C stable isotopes of various eco- system pools in two old-growth conifer forests, we sampled six species

Steven A. Trudell; Paul T. Rygiewicz; Robert L. Edmonds

2003-01-01

11

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

12

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 nondestructive research use on a loan basis. This inventory includes all samples of stable isotop...

1984-01-01

13

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 nondestructive research use on a loan basis. This inventory includes all samples of stable isotop...

1986-01-01

14

Stable isotope laser spectroscopy  

NASA Astrophysics Data System (ADS)

Recent advances in semiconductor laser technology have produced a reliable lightweight device ideally suited for a spacecraft high resolution molecular spectrometer. Lead-salt tunable diode lasers (TDL) emit in several spectral modes, each with a very narrow linewidth of -0.0003/cm. This spectral resolution is much narrower than typical Doppler broadened molecular linewidths in the mid-IR range. Thus it is possible to detect individual rotational lines within the vibrational band and measure their intensity, which can be used to determine gas concentration. The narrow spectral lines of any impurity gas tend to lie between the narrow lines of the gas of interest. This represents a major advantage over the accepted gas chromatograph mass spectrometer (GCMS) technique for measuring gas concentrations and isotope ratios. The careful and extensive gas purification procedures required to remove impurities for reliable GCMS measurements will not be required for an IR laser gas analysis. The infrared laser gas analysis technique is being developed to measure stable isotopic ratios of gases such as CO2, CH4, N2O, and NH3. This will eventually lead to development of instruments capable of in situ istopic measurements on planets such as Mars. The carbon (C-12, C-13) isotope ratio is indicative of the type of carbon fixation mechanisms (e.g., photosynthesis, respiration) in operation on a planet, while the nitrogen (N-14, N-15) isotope ratio can probably be used to date nitrogen-bearing Martian samples. The absorbance ratio of two adjacent lines of CO2 in the 2300/cm (4.3 micron) region of the spectrum was measured. The precision of the measurement is presently better than 1 percent and significant improvement is anticipated as rapid sweep-integration techniques and computer controlled data acquistion capabilities are incorporated.

Becker, J. F.; Yaldaei, Ramil; McKay, Christopher P.

1989-03-01

15

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

16

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

17

Relative isotopic abundances of zirconium in S-type stars  

Microsoft Academic Search

The relative abundances of the six stable or nearly stable isotopes of zirconium were measured for three S stars, R Cyg, V Cnc, and R Gem. The method of analysis is described with the abundances determined by comparing the observed stellar profile of intensity vs wavelength with synthetic spectra calculated by the Minnaert interpolation scheme for a single slab LTE

A. C. Zook

1978-01-01

18

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

19

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

20

THE ATOMIC WEIGHTS COMMISSION AND ISOTOPIC ABUNDANCE RATIO DETERMINATIONS.  

SciTech Connect

Following Thomson's discovery of stable isotopes in non-radioactive chemical elements, the derivation of atomic weight values from mass spectrometric measurements of isotopic abundance ratios moved very slowly. Forty years later, only 3 1/2 % of the recommended values were based on mass spectrometric measurements and only 38% in the first half century. It might be noted that two chemical elements (tellurium and mercury) are still based on chemical measurements, where the atomic weight value calculated from the relative isotopic abundance measurement either agrees with the value from the chemical measurement or the atomic weight value calculated from the relative isotopic abundance measurement falls within the uncertainty of the chemical measurement of the atomic weight. Of the 19 chemical elements, whose atomic weight is based on non-corrected relative isotopic abundance measurements, five of these are two isotope systems (indium, iridium, lanthanum, lutetium and tantalum) and one is a three-isotope system (oxygen).

HOLDEN, N.E.

2005-08-07

21

Stable isotope analysis in primatology: a critical review.  

PubMed

Stable isotope analysis has become an important tool in ecology over the last 25 years. A wealth of ecological information is stored in animal tissues in the relative abundances of the stable isotopes of several elements, particularly carbon and nitrogen, because these isotopes navigate through ecological processes in predictable ways. Stable carbon and nitrogen isotopes have been measured in most primate taxonomic groups and have yielded information about dietary content, dietary variability, and habitat use. Stable isotopes have recently proven useful for addressing more fine-grained questions about niche dynamics and anthropogenic effects on feeding ecology. Here, we discuss stable carbon and nitrogen isotope systematics and critically review the published stable carbon and nitrogen isotope data for modern primates with a focus on the problems and prospects for future stable isotope applications in primatology. PMID:23015270

Sandberg, Paul A; Loudon, James E; Sponheimer, Matt

2012-11-01

22

Metal Stable Isotopes in Paleoceanography  

NASA Astrophysics Data System (ADS)

Considered esoteric only a few years ago, research into the stable isotope geochemistry of transition metals is moving into the geoscience mainstream. Although initial attention focused on the potential use of some of these nontraditional isotope systems as biosignatures, they are now emerging as powerful paleoceanographic proxies. In particular, the Fe and Mo isotope systems are providing information about changes in oxygenation and metal cycling in ancient oceans. Zn, Cu, Tl, and a number of other metals and metalloids also show promise. Here we review the basis of stable isotope fractionation as it applies to these elements, analytical considerations, and the current status and future prospects of this rapidly developing research area.

Anbar, Ariel D.; Rouxel, Olivier

2007-05-01

23

[Distribution characteristics of soil humus fractions stable carbon isotope natural abundance (delta 13C) in paddy field under long-term ridge culture].  

PubMed

A 16-year field experiment was conducted in a ridge culture paddy field in the hilly region of Sichuan Basin, aimed to investigate the distribution characteristics of stable carbon isotope natural abundance (delta 13C) in soil humus fractions. The soil organic carbon (SOC) content in the paddy field under different cultivation modes ranked in the order of wide ridge culture > ridge culture > paddy and upland rotation. In soil humus substances (HS), humin (HU) was the main composition, occupying 21% - 30% of the total SOC. In the extracted soil carbon, humic acid (HA) dominated, occupying 17% - 21% of SOC and 38% - 65% of HS. The delta 13C value of SOC ranged from -27.9 per thousand to -25.6 per thousand, and the difference of the delta 13C value between 0-5 cm and 20-40 cm soil layers was about 1.9 per thousand. The delta 13C value of HA under different cultivation modes was 1 per thousand - 2 per thousand lower than that of SOC, and more approached to the delta 13C value of rapeseed and rice residues. As for fulvic acid (FA), its delta 13C value was about 2 per thousand and 4 per thousand higher than that of SOC and HA, respectively. The delta 13C value of HU in plough layer (0-20 cm) and plow layer (20-40 cm) ranged from -23.7 per thousand - -24.9 per thousand and -22.6 per thousand - -24.2 per thousand, respectively, reflecting the admixture of young and old HS. The delta 13C value in various organic carbon fractions was HU>FA>SOC>rapeseed and rice residues>HA. Long-term rice planting benefited the increase of SOC content, and cultivation mode played an important role in affecting the distribution patterns of soil humus delta 13C in plough layer and plow layer. PMID:21774322

Tang, Xiao-hong; Luo, You-jin; Ren, Zhen-jiang; L, Jia-ke; Wei, Chao-fu

2011-04-01

24

Stable Isotope Research Pool Inventory.  

National Technical Information Service (NTIS)

This report contains a listing of electromagnetically separated stable isotopes which are available for distribution within the United States for nondestructive research use from the Oak Ridge National Laboratory on a loan basis. This inventory includes a...

1982-01-01

25

Stable Isotope Research Pool Inventory.  

National Technical Information Service (NTIS)

This report contains a listing of electromagnetically separated stable isotopes which are available for distribution within the United States for non-destructive research use from the Oak Ridge National Laboratory on a loan basis. This inventory includes ...

1980-01-01

26

Stable isotopes in tree rings  

Microsoft Academic Search

Stable isotopes in tree rings could provide palaeoclimate reconstructions with perfect annual resolution and statistically defined confidence limits. Recent advances make the approach viable for non-specialist laboratories. The relevant literature is, however, spread across several disciplines, with common problems approached in different ways. Here we provide the first overview of isotope dendroclimatology, explaining the underlying theory and describing the steps

Danny McCarroll; Neil J. Loader

2004-01-01

27

THE ATOMIC WEIGHTS COMMISSION AND ISOTOPIC ABUNDANCE RATIO DETERMINATIONS  

Microsoft Academic Search

Following Thomson's discovery of stable isotopes in non-radioactive chemical elements, the derivation of atomic weight values from mass spectrometric measurements of isotopic abundance ratios moved very slowly. Forty years later, only 3 1\\/2 % of the recommended values were based on mass spectrometric measurements and only 38% in the first half century. It might be noted that two chemical elements

2005-01-01

28

Iron stable isotopes: beyond biosignatures  

NASA Astrophysics Data System (ADS)

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 the environmental biogeochemistry of Fe. At the same time, the Fe isotope system holds promise for other exciting frontiers, including applications in oceanography, solid Earth geochemistry and biomedicine. Such applications will be increasingly attractive as Fe isotope analysis becomes routine.

Anbar, A. D.

2004-01-01

29

A Study of the Decomposition of Reed (Phragmites australis ) as a Possible Source of Aquatic Humic Substances by Measuring the Natural Abundance of Stable Carbon Isotopes  

NASA Astrophysics Data System (ADS)

The decomposition of leaf and steam litter of reed (P. australis) was measured both in the field and in the laboratory. The breakdown rates, the total carbon and the stable carbon isotope dynamics of reed litter were determined. The stable carbon isotope ratios of isolated humic substances (fulvic and humic acids) were also analysed. The 13C value in reed remains increased from -26 to -24 for stems and from -27 to -26 for leaves. The dissolved fulvic and humic acids isolated from the experimental bottles (mean 13C was -27.6) and the reservoir water were depleted in 13C (mean 13C was -28.6) relative to the reed remains. The results show that reed litter is an important source of coloured aquatic humic substances.

Balogh, Katalin V.; Prsing, Mtys; Vrs, Lajos; Tth, Nomi

2006-02-01

30

Teaching stable isotopes  

NSDL National Science Digital Library

This is a reading assignment in three parts, with problem sets for each part. Part 1 is introductory, part 2 explains isotopic effects of volatilization and fluid flow during metamorphism, and part 3 uses data from the Alta contact aureole, Utah, as an example of the processes.

Dunn, Steven R.

31

Stable Isotope Group 1983 Progress Report.  

National Technical Information Service (NTIS)

The work of the Stable Isotope Group of the Institute of Nuclear Sciences in the fields of isotope geology, isotope hydrology, geochronology, isotope biology and related fields, and mass spectrometer instrumentation, during 1983, is described. (Atomindex ...

M. K. Stewart

1984-01-01

32

Stable isotope analysis of the bioelements: an introduction.  

PubMed

The abundances of the stable isotopes of the bioelements are not constant. Subtle, but significant, variations may be induced by physical, physiological and biochemical processes. These variations may be detected and quantified. Often, isotope fingerprints are characteristic of certain processes and may reveal information concerning the sources and origins of compounds of interest. Moreover, natural variabilities of stable isotopes may be exploited in order to perform tracer experiments. The most accurate technology to perform stable isotope analysis is (gas) isotope ratio MS (IRMS). Compound-specific approaches employ hyphenation of GC and LC to IRMS. In these approaches, complete conversion to simple gases prior to MS is required. Analysis by stable isotope ratio spectroscopy currently approaches the accuracy of IRMS. However, for bioanalytical projects, it is still predominantly confined to material synthetically enriched with stable isotopes. PMID:21083079

Flenker, Ulrich

2009-09-01

33

Stable Chlorine Isotope Fractionation  

NASA Astrophysics Data System (ADS)

Chlorine isotope partitioning between different phases is not well understood. Pore fluids can have ?37Cl values as low as -8, with neoform sediments having strongly positive values. Most strikingly, volcanic gases have ?37Cl values that cover a range in excess of 14 (Barnes et al., this meeting). The large range is difficult to explain in terms of equilibrium fractionation, which, although calculated to be very large for Cl in different oxidation states, should be less than 2 between chloride species (Schauble et al., 2003, GCA). To address the discrepancy between Nature and theory, we have measured Cl isotope fractionation for selected equilibrium and disequilibrium experiments in order to identify mechanisms that might lead to large fractionations. 1) NaCl (s,l) NaCl (v): NaCl was sealed in an evacuated silica tube and heated at one end, causing vaporization and reprecipitation of NaCl (v) at the cool end of the tube. The fractionation is 0.2 at 700C (halite-vapor) and 0.7 at 800C (liquid-vapor), respectively. The larger fractionation at higher temperature may be related to equilibrium fractionation between liquid and gas vs. `stripping' of the solid in the lower T experiments. 2) Sodalite NaCl(l): Nepheline and excess NaCl were sealed in a Pt crucible at 825C for 48 hrs producing sodalite. The measured newly-formed sodalite-NaCl fractionation is -0.2. 3) Volatilization of HCl: Dry inert gas was bubbled through HCl solutions and the vapor was collected in a downstream water trap. There was no fractionation for 12.4M HCl (HCl fuming) vapor at 25C. For a 1 M boiling HCl solution, the HCl-vapor fractionation was ~9. The difference is probably related to the degree of dissociation in the acid, with HCl dissolved in water for the highly acidic solutions, and dissociated H3O+ and Cl- for lower concentrations. The HCl volatilization experiments are in contrast to earlier vapor-liquid experiments in NaCl-H2O system, where fractionation was less than 0.2 at 400- 450 C (Leibscher et al., Chem. Geol., 2006). The HCl vaporization data provide a mechanism for generating large fractionations under appropriate natural conditions.

Sharp, Z.

2006-12-01

34

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

35

Periodicity of the stable isotopes  

Microsoft Academic Search

It is demonstrated that all stable (non-radioactive) isotopes are formally interrelated as the products of systematically adding alpha particles to four elementary units. The region of stability against radioactive decay is shown to obey a general trend based on number theory and contains the periodic law of the elements as a special case. This general law restricts the number of

J. C. A. Boeyens

2003-01-01

36

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

37

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

38

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

39

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

40

Assessing the Amazon Basin Circulation with Stable Water Isotopes  

Microsoft Academic Search

The isotopic abundances of Oxygen-18 (delta 18O) and Deuterium (delta 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

K. McGuffie; A. Henderson-Sellers

2004-01-01

41

Stable isotopes dissect food webs from top to the bottom  

NASA Astrophysics Data System (ADS)

Stable isotopes have been used extensively to study food web functioning, i.e. the flow of energy and matter among organisms. Traditional food-web studies are based on the natural variability of carbon and nitrogen 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 then measurement of entire food webs, i.e. 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 isotope 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.

2013-09-01

42

Detection of Correlations in Stellar Isotopic Abundances  

NASA Astrophysics Data System (ADS)

The composition of a star changes with time via sequences of thermonuclear reactions. These sequences strongly couple the abundances of all elements to each other. The resulting complex interdependencies often make it difficult to ascertain which isotopic abundances most influence one another. To investigate this, a FORTRAN program has been written which analyzes these abundances over time as predicted by a simulation to determine if they may be correlated. This is accomplished via a looping over all possible pairs of tracked isotopes, quantitatively ascertaining the shapes of the abundance versus time curves for each, and assigning numerical scores to determine if these pairs of curves are correlated, anticorrelated, or uncorrelated. Preliminary results from this study will be presented.

Thomsen, K. A.; Smith, M. S.

2012-10-01

43

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...

44

Carbon Isotope Abundances in Comets  

Microsoft Academic Search

Rotational lines of 13C14N have been identified in high-resolution (lambda\\/Deltalambda~60,000) echelle spectra of the CN B2Sigma+-X2Sigma+ (0-0) band in three comets. The 12C\\/13C abundance ratios determined using a full fluorescence excitation model for comets Levy (C\\/1990 K1), Austin (C\\/1989 X1), and Okazaki-Levy-Rudenko (C\\/1989 XIX) are 90+\\/-10, 85+\\/-20, and 93+\\/-20, respectively, consistent with the solar system ratio, 90. A lower limit

Susan Wyckoff; Marvin Kleine; Bruce A. Peterson; Peter A. Wehinger; Lucy M. Ziurys

2000-01-01

45

Stable Isotope Fractionation Studies of Timna Mineralization.  

National Technical Information Service (NTIS)

Stable isotope fractionation studies have been shown to be invaluable geochemical indicators of the processes involved in ore deposition and mineralization. The present work is concerned with the application of carbon and oxygen isotopic studies to an und...

A. Matthews

1983-01-01

46

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

47

Stable Carbon and Sulfur Isotopes as Records of the Early Biosphere. Abstract Only.  

National Technical Information Service (NTIS)

The abundance ratios of the stable isotopes of light elements such as carbon and sulfur can differ between various naturally-occurring chemical compounds. If coexisting compounds have achieved mutual chemical and isotopic equilibrium, then the relative is...

D. J. Desmarais

1989-01-01

48

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

2012-03-30

49

Stable isotope deltas: Tiny, yet robust signatures in nature  

USGS Publications Warehouse

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 14C 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. 13C, 2H, and 18O ) 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?25 mUr (or?2.5 cUr or?0.25 dUr; 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.

Brand, Willi A.; Coplen, Tyler B.

2012-01-01

50

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

2013-03-19

51

Attempt to characterize certain organic and mineral substances by their stable isotope composition  

Microsoft Academic Search

The determination of the relative abundance of various stable isotopes--; deuterium, oxygen-18, carbon-13, nitrogen-15, sulphur- 34--can be used to ; characterize the origin of a water body and of an organic or mineral substance in ; the environment. This results from the discovery that isotopic fractioning by ; living organisms occurs. The stable isotope composition of any substance ; reflects,

J. Bripartout; J. C. Fontes; R. Letolle; A. Mariotti; L. Merlivat

1975-01-01

52

Comparison of stable isotope reference samples  

Microsoft Academic Search

Use of light stable isotope ratio measurements has proliferated in the past decade. The need for procuring additional stable isotope reference materials was recognized at an International Atomic Energy Agency (IAEA) consultants' meeting convened in 19761. This group recommended acquisition of two carbonates, two carbon dioxide samples, a biotite, a sulphate, and other reference materials. We report here on the

Tyler B. Coplen; Carol Kendall; Jessica Hopple

1983-01-01

53

Stable isotope composition of Hellenic bottled waters  

Microsoft Academic Search

Bottled waters are an increasingly significant product in the human diet. In this work, we present a dataset of stable isotope ratios for bottled waters sampled in Greece. A total of 25 domestic brands of bottled still waters, collected on the Greek market in 2009, were analysed for ?18O and ?2H. The measured stable isotope ratios range from ?9.9 to

2010-01-01

54

Stable Isotope-Coded Proteomic Mass Spectrometry  

SciTech Connect

The ability to quantify the changes in protein abundance between cells subjected to a variety of extracellular stimuli or the onset of a diseased state remains an extremely active area of proteome research. Although advances in sample preparation, chromatographic separation, mass spectrometry instrumentation and bioinformatics contribute to producing a viable method for comparative proteome-wide analyses, the foundation of quantitation is based in part upon improved methods for chemical and metabolic stable isotope labeling of proteins and peptides. The ability to quantify differences in protein expression and post-translational modifications has been demonstrated, but insights into the biochemical mechanisms that will contribute to the development of new biotechnologies have yet to be realized.

Goshe, Michael B. (BATTELLE (PACIFIC NW LAB)); Smith, Richard D. (BATTELLE (PACIFIC NW LAB))

2003-02-01

55

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

56

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

57

Helium isotopic abundance variation in nature  

SciTech Connect

The isotopic abundance of helium in nature has been reviewed. This atomic weight value is based on the value of helium in the atmosphere, which is invariant around the world and up to a distance of 100,000 feet. Helium does vary in natural gas, volcanic rocks and gases, ocean floor sediments, waters of various types and in radioactive minerals and ores due to {alpha} particle decay of radioactive nuclides.

Holden, N.E.

1993-08-01

58

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

Microsoft Academic Search

Trophic relationships were examined using natural-abundance ¹³C and ¹⁵N analyses and a ¹⁵N-tracer addition experiment in Walker Branch, a 1st-order forested stream in eastern Tennessee. In the ¹⁵N-tracer addition experiment, we added ¹⁵NH to stream water over a 6-wk period in early spring, and measured ¹⁵N:¹⁴N ratios in different taxa and biomass compartments over distance and time. Samples collected from

PATRICK J. MULHOLLAND; J ENNIFER; L. TANK; D IANE M. SANZONE; WILFRED M. WOLLHEIM; J. PETERSON; J ACKSON R. WEBSTER; JUDY L. MEYER

2000-01-01

59

Stable isotope investigations of chlorinated aliphatic hydrocarbons.  

National Technical Information Service (NTIS)

Stable isotope ratio measurements for carbon (C) and chlorine (Cl) can be used to elucidate the processes affecting transformation and transportation of chlorinated aliphatic hydrocarbons (CAHs) in the environment. Methods recently developed in our labora...

T. Abrajano L. J. Heraty B. D. Holt L. Huang N. C. Sturchio

1999-01-01

60

Stable Isotopes As Tracers In Ocean Sciences  

Microsoft Academic Search

By making use of differences in stable carbon isotope ratios, which have resulted from chemical isotope effects, for carbon reservoirs large scale tracer experiments have been observed. These natural experiments have been used to quantify ocean pollution, sediment sources and duck food-webs.

P. Parker; R. Anderson; J. Winters; R. Scalan

1983-01-01

61

Transport of stable isotopes: I: Development of a kinetic continuum theory for stable isotope transport  

Microsoft Academic Search

Equations are developed describing migration of stable isotopes via a fluid phase infiltrating porous media. The formalism of continuum fluid mechanics is used to deal with the problem of microscopic inhomogeneity. Provision is made explicitly for local equilibrium exchange of isotopes between minerals and fluids as well as for kinetic control of isotopic exchange. Changing characteristic parameters of transport systems

L. P. Baumgartner; D. Rumble

1988-01-01

62

Stable isotope dilution assays in mycotoxin analysis.  

PubMed

The principle and applications of stable isotope dilution assays (SIDAs) in mycotoxin analysis are critically reviewed. The general section includes historical aspects of SIDAs, the prerequisites and limitations of the use of stable isotopically labelled internal standards, and possible calibration procedures. In the application section actual SIDAs for the analysis of trichothecenes, zearalenone, fumonisins, patulin, and ochratoxin A are presented. The syntheses and availability of labelled mycotoxins for use as internal standards is reviewed and specific advances in food analysis and toxicology are demonstrated. The review indicates that LC-MS applications, in particular, require the use of stable isotopically labelled standards to compensate for losses during clean-up and for discrimination due to ion suppression. As the commercial availability of these compounds continues to increase, SIDAs can be expected to find expanding use in mycotoxin analysis. PMID:18060393

Rychlik, Michael; Asam, Stefan

2007-12-01

63

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

64

Stable Isotopes in Dendroclimatology: Moving Beyond Potential  

Microsoft Academic Search

\\u000a When trees grow, they assimilate carbon from atmospheric carbon dioxide, and hydrogen and oxygen from soil water. The stable\\u000a isotope ratios of these three elements carry signals that can be interpreted in terms of past climate because isotope ratios\\u000a are climatically controlled by the trees water and gas exchange budgets. The traditional tree-ring proxies form the most\\u000a widespread and arguably

Mary Gagen; Danny McCarroll; Neil J. Loader; Iain Robertson

65

Aberrant Water Homeostasis Detected by Stable Isotope Analysis  

PubMed Central

While isotopes are frequently used as tracers in investigations of disease physiology (i.e., 14C labeled glucose), few studies have examined the impact that disease, and disease-related alterations in metabolism, may have on stable isotope ratios at natural abundance levels. The isotopic composition of body water is heavily influenced by water metabolism and dietary patterns and may provide a platform for disease detection. By utilizing a model of streptozotocin (STZ)-induced diabetes as an index case of aberrant water homeostasis, we demonstrate that untreated diabetes mellitus results in distinct combinations, or signatures, of the hydrogen (?2H) and oxygen (?18O) isotope ratios in body water. Additionally, we show that the ?2H and ?18O values of body water are correlated with increased water flux, suggesting altered blood osmolality, due to hyperglycemia, as the mechanism behind this correlation. Further, we present a mathematical model describing the impact of water flux on the isotopic composition of body water and compare model predicted values with actual values. These data highlight the importance of factors such as water flux and energy expenditure on predictive models of body water and additionally provide a framework for using naturally occurring stable isotope ratios to monitor diseases that impact water homeostasis.

O'Grady, Shannon P.; Wende, Adam R.; Remien, Christopher H.; Valenzuela, Luciano O.; Enright, Lindsey E.; Chesson, Lesley A.; Abel, E. Dale; Cerling, Thure E.; Ehleringer, James R.

2010-01-01

66

Stable Isotope Constraints of Atmospheric Methane Budgets  

NASA Astrophysics Data System (ADS)

Recent reports of methane concentrations in ice records, including the 800 kyr Antarctic EPICA ice core, confirm that the present day tropospheric methane mixing ratios of over 1.8 ppm are anomalously high for this millennial time period (PIH/LP methane mean is 0.52 ppm). Our understanding and quantification of the changes to and intensity variations of tropospheric methane sources and sinks remains imperfect. Stable carbon and hydrogen isotope ratios of atmospheric methane offer assistance to check our assessments of methane fluxes. However, due to a) the number and shifts of methane sources and sinks, b) substantial overlap in isotope signatures and c) variations on both annual and geologic time scales, the isotope mass balances are under-constrained. Our attempts to reconcile present day and past atmospheric methane mass balances continue to challenge us. Despite this limitation, isotope information is essential to elucidate and characterize the processes and pathways affecting global atmospheric methane systematics. This presentation will outline these mass balancing acts and discuss these issues surrounding the stable isotopes of methane.

Whiticar, M. J.; Melton, J. R.; Kaplan, J. O.; Schaefer, H.

2008-12-01

67

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

68

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

69

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

70

Dual stable isotope analysis (? 13C and ? 15N) of soil invertebrates and their food sources  

Microsoft Academic Search

More research is required to validate and refine natural abundance stable isotope ratio techniques as a tool for the investigation of the feeding ecology of soil animals and trophic relations in soil food webs. Isotope ratios of C (?13C) and N (?15N) were measured in herbivorous and detritivorous invertebrate groups, namely lumbricid earthworms (7 species), enchytraeid worms (3 species), slugs

Olaf Schmidt; James P Curry; Jens Dyckmans; Emilia Rota; Charles M Scrimgeour

2004-01-01

71

The stable isotope ecology of terrestrial plant succession  

Microsoft Academic Search

We review the relevance and use of stable isotopes for the study of plant community succession. Stable isotope measurements provide information on the origin of resources acquired by plants, the processes governing resource uptake and transformation, and the physiological and environmental conditions of plant growth. When combined with measurements of the stable isotope ratio values of soil microbial biomass, soil

Vctor Resco; Juan P. Ferrio; Jos A. Carreira; Leonor Calvo; Pere Casals; ngel Ferrero-Serrano; Elena Marcos; Jos M. Moreno; David A. Ramrez; M. Teresa Sebasti; Fernando Valladares; David G. Williams

2011-01-01

72

Characterising the Terrestrial Stable Cr Isotope Cycle  

NASA Astrophysics Data System (ADS)

Cr isotopes were shown to present a sensitive tracer of redox changes in aqueous solutions [1,2]. Here, the potential of stable Cr isotope fractionation in the environment was further investigated by high-precision double- spike MC-ICP-MS measurements. Reduction experiments of Cr(VI) to Cr(III) in aqueous solutions on ion exchange columns confirmed the mass-dependent Cr isotope fractionation of -3.4 per atomic mass unit reported by Ellis et al. [1]. Furthermore, these experiments revealed that the fractionation associated with adsorption is minor. This is shown by a very small preferential adsorption of isotopically heavy chromium of most likely Cr(III) species on the anion resin. A similar observation was made for Cr(III) species on cation resin. This is in line with the negligible fractionation effects that have been reported for adsorption of Cr(VI) onto ?-Al2O3 and goethite surfaces [2], respectively. Thus, the large Cr isotope fractionation that accompanies Cr reduction and the small sorption effects of both Cr(VI) and Cr(III) species make stable Cr isotopes a sensitive tracer to detect and quantify redox changes in a variety of geochemical reservoirs. The stable Cr isotope compositions of the principle silicic igneous reservoirs of the Earth do not show measurable variations. ?^{53}Cr/^{52}Cr values (relative to SRM3112a) of six mantle lherzolites (- 0.0140.083; 2 SD), six ultramafic cumulate rocks (-0.0340.094) and five continental and oceanic basalts that represent partial mantle melts (-0.0440.089) are indistinguishable within uncertainties. Thus, unlike as was suggested for Fe isotopes [3], partial mantle melting appears not to fractionate Cr isotopes. Cr(III)-bearing uvarovite and fuchsite minerals from amphibolite facies metamorphic rocks are also equal to those of igneous rock reservoirs. These observations are not unexpected, because there is no apparent redox change of Cr involved during partial mantle melting or metamorphism. Also the fractionation effects caused by potential ligand changes of Cr between solids, and solids and melt are too small to be detected at high-temperatures. Large Cr isotope fractionations with ?^{53}Cr/^{52}Cr values of +0.672 to +1.093 were observed for crocoite (PbCr(VI)O4), a mineral that forms in oxidising zones of medium- to high- temperature hydrothermal systems. It has yet to be investigated whether Cr isotopes fractionate during the oxidation of Cr(III) to Cr(VI). It is, however, likely, that Cr behaves like its chemical twin Se that only fractionates during reduction [4]. In this case the observed heavy Cr isotope compositions of crocoites are the result of partial Cr(VI) reduction from the hydrothermal fluid, allowing to quantify changes in redox conditions along the hydrothermal pathway. [1] Ellis, A.S. et al. (2002), Science 295, 2060-2062, [2] Ellis, A.S. et al. (2004), Eniron. Sci. Technol. 38, 3604-3607, [3] Weyer, S. et al. (2005), Earth and Planet. Sci. Letters 240, 251-264, [4] Johnson, T.M. and Bullen, T.D. (2004), Reviews in Mineralogy & Geochemistry 55, 289-317.

Schoenberg, R.; Zink, S.; Staubwasser, M.; von Blanckenburg, F.

2006-12-01

73

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

74

The abundances of isotopes in the cosmic radiation. [Milky way  

Microsoft Academic Search

Studies of the isotopic composition of nuclei in the cosmic radiation are reviewed, including abundances of the isotopes of elements from H to Ni (nuclear charge 1>{ital Z}>28), and their implications for cosmic ray origin, acceleration, and transport in the Galaxy. The review focuses on determinations of the composition of cosmic ray source material, and the extent to which the

Mewaldt

1989-01-01

75

Stable carbon isotope ratios of rock varnish organic matter: a new paleoenvironmental indicator.  

PubMed

Stable carbon isotope ratios of organic matter in rock varnishes of Holocene age from western North America and the Middle East show a strong association with the environment. This isotopic variability reflects the abundance of plants with different photosynthetic pathways in adjacent vegetation. Analyses of different layers of varnish on late Pleistocene desert landforms indicate that the carbon isotopic composition of varnish organic matter is a paleoenvironmental indicator. PMID:17777781

Dorn, R I; Deniro, M J

1985-03-22

76

Mass Spectrometric Investigations on Ruthenium Isotopic Abundances.  

National Technical Information Service (NTIS)

Ruthenium isotopic compositions were measured on various terrestrial samples. One measurement was made on meteoritic material and assumed to be representative of primordial ruthenium. These measurements were made possible after a careful investigation of ...

C. Devillers T. Lecomte M. Lucas R. Hagemann

1976-01-01

77

Lithium Isotopic Abundances in Metal-poor Halo Stars  

Microsoft Academic Search

Very high quality spectra of 24 metal-poor halo dwarfs and subgiants have been acquired with ESO's VLT\\/UVES for the purpose of determining Li isotopic abundances. The derived one-dimensional, non-LTE 7Li abundances from the Li I 670.8 nm line reveal a pronounced dependence on metallicity but with negligible scatter around this trend. Very good agreement is found between the abundances from

Martin Asplund; David L. Lambert; Poul Erik Nissen; Francesca Primas; Verne V. Smith

2006-01-01

78

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

79

STABLE ISOTOPES IN HUMAN NUTRITION LABORATORY METHODS AND RESEARCH APPLICATIONS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The existence of stable, non-radioactive isotopes of the elements and the ability to measure these isotopes by mass spectrometry were first recognized in the early and mid-1920s (Aston, 1927). However, stable isotopes were not used for nutrition-related research until the 1930s, when Schoenheimer a...

80

MINERAL BIOAVAILABILITY AND METABOLISM DETERMINED BY USING STABLE ISOTOPE TRACERS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Definitive data on mineral bioavailability in humans and animals can be obtained by using isotopic tracers. The use of stable isotope tracers to study important issues in mineral nutrition has expanded rapidly in the past two decades, particularly in humans. Stable isotopes have a number of advanta...

81

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...

82

STABLE CARBON ISOTOPE ANALYSIS OF NUCLEIC ACIDS TO TRACE SOURCES OF DISSOLVED SUBSTRATES USED BY ESTUARINE BACTERIA  

EPA Science Inventory

The natural abundance of stable carbon isotopes measured in bacterial nucleic acids that were extracted from estuarine bacterial concentrates were used to trace sources of organic matter for bacteria in.aquatic environments. he stable carbon isotope ratios of P. aeruginosa and nu...

83

Stable isotopes in juvenile marine fishes and their invertebrate prey from the Thames Estuary, UK, and adjacent coastal regions  

Microsoft Academic Search

Estuaries are regarded as valuable nursery habitats for many commercially important marine fishes, potentially providing a thermal resource, refuge from predators and a source of abundant prey. Stable isotope analysis may be used to assess relative resource use from isotopically distinct sources. This study comprised two major components: (1) development of a spatial map and discriminant function model of stable

Chris D. B. Leakey; Martin J. Attrill; Simon Jennings; Mark F. Fitzsimons

2008-01-01

84

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

85

Probing the Activities of Soil Invertebrates Using Stable Isotope Approaches  

NASA Astrophysics Data System (ADS)

Soil dwelling invertebrates play a vital role in determining the physical properties and nutrient cycling in soil. Their diverse behaviours influence organic litter, water and gas transport. They impact on other soil biota, e.g. microbes, plants, other invertebrates, etc. via their various grazing and predatory activities, and their role in the comminution of litter influences the activities of other decomposer organisms. However, major challenges exist in the study of the activities of such invertebrates due to the small sizes of many of the key organisms and the opaque nature of soil. This paper will provide an overview of a number of new approaches that have been developed to investigate the behaviours of soil invertebrates. The techniques we employ are based on the use of stable isotopes, exploiting both natural abundance labelling and artificially isotopically enriched tracers. Experiments range from simple feeding and choice experiments in laboratory arenas to pot-based microcosm studies, and field experiments (Chamberlain et al., 2004; Black et al. in press). The philosophy underpinning this research is to exploit fundamental biochemical information to determine the activities of organisms. Thus, compound-specific stable isotope determinations are one of our major goals since these yield high specificity stable isotopic information, often at the biochemical building block level. Compound-specific approaches also have the virtue of enhancing analytical sensitivity, such that the ? 13C values of the biochemical components of individual specimens of low microgram-sized organisms, i.e. mesoinvertebrates, can be recorded their behaviours investigated (Evans et al., 2003; Black et al. in press).

Evershed, R. P.

2004-12-01

86

Distribution and fractionation of Zn stable isotopes in the oceans  

Microsoft Academic Search

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

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

2006-01-01

87

Cr stable isotope fractionation and reaction kinetics in aqueous milieu  

Microsoft Academic Search

Mass-dependent stable Cr isotope variations show great potential to monitor the natural attenuation of anthropogenic chromate pollution as well as to investigate changes in environmental conditions in the present and the past. However, accurate interpretation of mass-dependent Cr isotope variations requires profound knowledge of the Cr isotope fractionation behaviour during redox transitions and the isotope exchange kinetics of the reactions

S. Zink; R. Schoenberg; M. Staubwasser

2009-01-01

88

STABLE ISOTOPES IN ECOLOGICAL STUDIES: NEW DEVELOPMENTS IN MIXING MODELS  

EPA Science Inventory

Stable isotopes are increasingly being used as tracers in ecological studies. One application uses isotopic ratios to quantify the proportional contributions of multiple sources to a mixture. Examples include food sources for animals, water sources for plants, pollution sources...

89

A gas chromatograph\\/mass spectrometry method for determining isotopic distributions in organic compounds used in the chemical approach to stable isotope separation  

Microsoft Academic Search

A variety of gas chromatograph\\/mass spectrometry (GC\\/MS) methods have been developed to resolve benzene, benzophenone, anthracene, fluorenone, and their respective stable isotope analogs from other components by gas chromatography. The ratio of stable isotope-labeled material to natural isotopic abundance compounds is determined from the mass spectra averaged across the chromatographic peak. Both total ion and selective ion chromatographic approaches were

A. M. Martinez; W. D. Spall; B. F. Smith

1990-01-01

90

The Stable Isotopic Composition of Atmospheric CO2  

NASA Astrophysics Data System (ADS)

When a bean leaf was sealed in a closed chamber under a lamp (Rooney, 1988), in two hours the atmospheric CO2 in the microcosm reached an isotopic steady state with a 13C abundance astonishingly similar to the global mean value of atmospheric CO2 at that time (-7.5 in the ?13C notation introduced below). Almost concurrently, another research group sealed a suspension of asparagus cells in a different type of microcosm in which within about two hours the atmospheric O2 reached an isotopic steady state with 18O enrichment relative to water in the microcosm that was, too, remarkably similar to the global-scale offset between atmospheric O2 and mean ocean water (21 versus 23.5 in the ?18O notation introduced below; Guy et al., 1987). These classic experiments capture some of the foundations underlying the isotopic composition of atmospheric CO2 and O2. First, in both cases the biological system rapidly imposed a unique isotopic value on the microcosms' atmosphere via their massive photosynthetic and respiratory exchange of CO2 and O2. Second, in both cases the biological system acted on materials with isotopic signals previously formed by the global carbon and hydrological cycles. That is, the bean leaf introduced its previously formed organic matter (the source of the CO2 respired into microcosm's atmosphere), and the asparagus cells were introduced complete with local tap water (from which photosynthesis released molecular oxygen). Therefore, while the isotopic composition of the biological system used was slave to long-term processes, intense metabolic processes centered on few specific enzymes (Yakir, 2002) dictated the short-term atmospheric composition.In a similar vein, on geological timescales of millions of years, the atmosphere and its isotopic composition are integral parts of essentially a single dynamic ocean-atmosphere-biosphere system. This dynamic system exchanges material, such as carbon and oxygen, with the sediments and the lithosphere via slow processes that roughly follow the cycle of: weathering of rock and carbon uptake from the atmosphere, transport to the ocean, sedimentation, plate tectonics, metamorphism, and volcanism - leading to carbon release back to the atmosphere. But on a shorter timescale of years to millennia, the very slow geological processes retreat to the background, against which other massive fluxes control the rapid exchange of carbon and oxygen within the ocean-atmosphere-biosphere system. It is this timescale that is relevant to the well-being of our human society, and is a major focus in much of the research on the carbon cycle.Isotopes were discovered in 1911 (Urey, 1948) and the implications of isotopic substitution in chemical reactions were realized sometime later ( Bigeleisen, 1965). In practice, the use of stable isotopes in geochemistry and biogeochemistry (e.g., Craig, 1953, 1954) awaited the development of the isotope ratio mass spectrometer ( McKinney et al., 1950; Nier, 1947) that provided the necessary precision. Over the 50 years following this breakthrough, the application of stable isotopes has made tremendous progress in the scope of applications, as well as in the resolution and precision of the measurements. The carbon isotopic composition of rocks and sediments was measured intensively since the early 1950s ( Hoefs, 1987). Isotope hydrology caught up quickly ( Clark and Fritz, 1997), followed by the application of stable isotopes in biology and ecology ( Rundel et al., 1988; Griffiths, 1998; Ehleringer et al., 1992). Today, stable isotope measurements have become an indispensable and integral part of atmospheric measurement programs (e.g., Francey et al., 2001; Masarie et al., 2001; Trolier et al., 1996). Efforts to develop analytical and numerical models that incorporate the cycling of stable isotopes in CO2 expanded in parallel (e.g., Bolin, 1981; Ciais et al., 1997a, b; Enting et al., 1995). Recently, the consideration of mass-independent isotope phenomena in nature ( Thiemens, 1999; see Chapter 4.06, and of triple stable isotopes in geochemistry

Yakir, D.

2003-12-01

91

GCR neon isotopic abundances: Comparison with wolf-rayet star models and meteoritic abundances  

NASA Astrophysics Data System (ADS)

Measurements of the neon isotopic abundances from the ACE-CRIS experiment are presented. These abundances have been obtained in seven energy intervals over the energy range of ~80<=E<=280 MeV/nucleon. The 22Ne/20Ne source ratio is derived using the measured 21Ne/20Ne abundance as a ``tracer'' of secondary production of the neon isotopes. We find that the 22Ne/20Ne abundance ratio at the cosmic-ray source is a factor of 5.0+/-0.2 greater than in the solar wind. The GCR 22Ne/20Ne ratio is also shown to be considerably larger than that found in anomalous cosmic rays, solar energetic particles, most meteoritic samples of matter, and interplanetary dust particles. Recent two-component Wolf-Rayet models provide predictions for the 22Ne/20Ne ratio and other isotope ratios. Comparison of the CRIS neon, iron, and nickel isotopic source abundance ratios with predictions indicate possible enhanced abundances of some neutron-rich nuclides that are expected to accompany the 22Ne excess. .

Binns, W. R.; Wiedenbeck, M. E.; Christian, E. R.; Cummings, A. C.; George, J. S.; Israel, M. H.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.; von Rosenvinge, T. T.; Yanasak, N. E.

2001-11-01

92

Systematic investigations of the stable Cd isotopes  

NASA Astrophysics Data System (ADS)

The Cd nuclei, especially the stable even-even isotopes have been well studied since they were suggested as paradigms of the vibrational, or U(5), limit of the Interacting Boson Model (IBM). In addition to the normal quadrupole phonon states, in many cases suggested up to the three-phonon quintuplet, more deformed 2p4h intruder excitations have been established. Recent investigations with the (n,n^'?) reaction [1,2,3,4] have provided a wealth of information on the low-lying levels, including many lifetimes not previously known. Deviations in the transition B(E2) values for low-spin states from those expected for U(5) nuclei are observed to appear systematically across the Cd isotopes. We have performed detailed calculations using the IBM-2, and find that these deviations cannot be explained through considered mixings with the intruder excitations or mixed-symmetry states, indicating that some physics is missing in the description of these levels. [1] F. Corminboeuf et al., Phys. Rev. C 63, 014305 (2001).[2] P.E. Garrett et al., Phys. Rev. C 75, 014307 (2007).[3] D. Bandyopadhyay et al., to be published. [4] M. Kadi et al., Phys. Rev. 68, 031306 (2003).

Garrett, P. E.; Green, K. L.; Wood, J. L.; Kulp, W. D.

2007-10-01

93

Stable Isotope Group 1985 progress report.  

National Technical Information Service (NTIS)

The work of the Group in 1985 is described and includes studies in isotope geology, isotope hydrology, geochronology, mass spectrometer instrumentation and isotope biology. 55 refs. (Atomindex citation 21:011537)

G. L. Lyon

1986-01-01

94

Stable Isotope Group 1984 progress report.  

National Technical Information Service (NTIS)

The work of the group in 1984 is described and includes studies in isotope geology, isotope hydrology, geochronology, isotope biology and mass spectrometer instrumentation. Geothermal studies have decreased compared to other years, but major data summarie...

G. L. Lyon

1985-01-01

95

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

96

Isotope-abundance variations of selected elements (IUPAC technical report)  

USGS Publications Warehouse

Documented variations in the isotopic compositions of some chemical elements are responsible for expanded uncertainties in the standard atomic weights published by the Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry. This report summarizes reported variations in the isotopic compositions of 20 elements that are due to physical and chemical fractionation processes (not due to radioactive decay) and their effects on the standard atomic-weight uncertainties. For 11 of those elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, copper, and selenium), standard atomic-weight uncertainties have been assigned values that are substantially larger than analytical uncertainties because of common isotope-abundance variations in materials of natural terrestrial origin. For 2 elements (chromium and thallium), recently reported isotope-abundance variations potentially are large enough to result in future expansion of their atomic-weight uncertainties. For 7 elements (magnesium, calcium, iron, zinc, molybdenum, palladium, and tellurium), documented isotope variations in materials of natural terrestrial origin are too small to have a significant effect on their standard atomic-weight uncertainties. This compilation indicates the extent to which the atomic weight of an element in a given material may differ from the standard atomic weight of the element. For most elements given above, data are graphically illustrated by a diagram in which the materials are specified in the ordinate and the compositional ranges are plotted along the abscissa in scales of (1) atomic weight, (2) mole fraction of a selected isotope, and (3) delta value of a selected isotope ratio.

Coplen, T. B.; Bohlke, J. K.; De Bievre, P.; Ding, T.; Holden, N. E.; Hopple, J. A.; Krouse, H. R.; Lamberty, A.; Peiser, H. S.; Revesz, K.; Rieder, S. E.; Rosman, K. J. R.; Roth, E.; Taylor, P. D. P.; Vocke, Jr. , R. D.; Xiao, Y. K.

2002-01-01

97

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

98

Stable Isotopes of Cr and Se as Tracers of Redox Processes in Earth Surface Environments  

Microsoft Academic Search

\\u000a Redox reactions play a central role in the environmental geochemistry of chromium (Cr) and selenium (Se). A small but growing\\u000a body of research shows that the stable isotope abundances of both elements are altered by these redox reactions. As is observed\\u000a with nitrate and sulfate, reduction of the higher valence oxoanions to lower valence forms induces isotopic fractionation,\\u000a with the

Thomas M. Johnson

99

Incorporating concentration dependence in stable isotope mixing models  

Microsoft Academic Search

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 linear mixing model assumes that the proportional contribution of a source to a mixture

Donald L. Phillips; Paul L. Koch

2002-01-01

100

Palaeoclimate interpretation of stable isotope data from lake sediment archives  

Microsoft Academic Search

The isotope composition of authigenic and biogenic carbonates and diatom silica are commonly used as palaeoclimate proxies from lake sediments. This article reviews the controls on the isotope composition of lacustrine skeletal and non-skeletal deposits and illustrates how stable isotope studies contribute to an understanding of changes in temperature, precipitation patterns, evaporation and the carbon cycle. It highlights the differences

Melanie J Leng; Jim D Marshall

2004-01-01

101

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...

102

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...

103

Investigating the Formation of Pedogenic Carbonate Using Stable Isotopes  

Microsoft Academic Search

The stable isotope composition of pedogenic carbonate has been used as a paleoenvironmental proxy because it is thought to form in isotopic equilibrium with soil CO2 and soil water, which are influenced by vegetation type and atmospheric circulation patterns, respectively. However, the isotopic composition of soil CO2 and soil water change seasonally and it is not known what portion of

D. O. Breecker; Z. D. Sharp; L. McFadden

2006-01-01

104

Some natural variations in the relative abundance of copper isotopes  

USGS Publications Warehouse

The relative isotopic abundance of copper has been measured in a number of minerals and a few plant materials. Suites of samples from Michigan and the Colorado Plateau have been examined in more detail to determine if local variations due to isotopic exchange or diffusion could be found. The relative isotopic abundance of copper in specimens from several other localities was also determined. The variations noted were small but in some cases were felt to be significant because they were larger than the experimental error (0??1 per cent in the ratio). A total spread of -1 to +8 parts per mil compared to the standard was found in the specimens tested. ?? 1958.

Walker, E. C.; Cuttitta, F.; Senftle, F. E.

1958-01-01

105

The use of stable isotopes to study ecosystem gas exchange  

Microsoft Academic Search

Stable isotopes are a powerful research tool in environmental sciences and their use in ecosystem research is increasing.\\u000a In this review we introduce and discuss the relevant details underlying the use of carbon and oxygen isotopic compositions\\u000a in ecosystem gas exchange research. The current use and potential developments of stable isotope measurements together with\\u000a concentration and flux measurements of CO2

D. Yakir; L. da S. L. Sternberg

2000-01-01

106

Carbon, Nitrogen and Oxygen Stable Isotope Ratios in Chitin  

Microsoft Academic Search

\\u000a Stable isotope ratios in chitin are firmly imprinted during biopolymer biosynthesis and reflect dietary, metabolic, and environmental\\u000a influences. Chitin is a chemically complex amino sugar biopolymer that also includes non-amino-sugar moieties with contrasting\\u000a isotopic compositions. Reproducible N, C, O-stable isotope determinations should rely on a chemically purified chitin substrate\\u000a with limited non-amino-sugar contributions. Insecta, Crustacea and Merostomata are not distinguished

Arndt Schimmelmann

107

Intrinsic stable isotope labeling of plants for nutritional investigations in humans  

Microsoft Academic Search

Although plant foods provide an array of nutrients in the human diet, our knowledge of how efficiently these nutrients are absorbed has been limited by our ability to selectively monitor their absorption from a complex food matrix. Intrinsic labeling of plants with low-abundance stable isotopes can provide a safe, traceable product to investigate absorptive phenomena in the gut. Various techniques,

Michael A. Grusak

1997-01-01

108

Energy sources for aquatic animals in the Orinoco River floodplain: evidence from stable isotopes  

Microsoft Academic Search

Stable carbon and nitrogen isotope ratios in autotrophs, aquatic invertebrates and fishes from the Orinoco River floodplain of Venezuela reveal that microalgae, including both phytoplankton and epiphytic (attached) forms, are predominant energy sources for many aquatic animals, even though aquatic vascular plants are much more abundant. Floating mats of the grass Paspalum repens and the water hyacinth Eichhornia spp. harbor

S. K. Hamilton; W. M. Lewis; S. J. Sippel

1992-01-01

109

The separation of stable isotopes of carbon  

NASA Astrophysics Data System (ADS)

The present state of work on the separation of carbon isotopes by diffusion, fractional distillation, chemical isotopic exchange, and the selective excitation and dissociation of molecules in electrical discharges or in the field of laser radiation has been examined. The characteristics of new laboratory and industrial assemblies for separating carbon isotopes have been described. Promising directions of study aimed at developing effective technological processes for separating carbon isotopes have been noted. The bibliography contains 148 references.

Oziashvili, E. D.; Egiazarov, A. S.

1989-04-01

110

Stable-isotope fingerprints of biological agents as forensic tools.  

PubMed

Naturally occurring stable isotopes of light elements in chemical and biological agents may possess unique "stable-isotope fingerprints" depending on their sources and manufacturing processes. To test this hypothesis, two strains of bacteria (Bacillus globigii and Erwinia agglomerans) were grown under controlled laboratory conditions. We observed that cultured bacteria cells faithfully inherited the isotopic composition (hydrogen, carbon, and nitrogen) of media waters and substrates in predictable manners in terms of bacterial metabolism and that even bacterial cells of the same strain, which grew in media water and substrates of different isotopic compositions, have readily distinguishable isotopic signatures. These "stable-isotopic fingerprints" of chemical and biological agents can be used as forensic tools in the event of biochemical terrorist attacks. PMID:12570211

Horita, Juske; Vass, Arpad A

2003-01-01

111

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

112

Stable isotope views on ecosystem function: challenging or challenged?  

PubMed

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, Ubeda, 18-22 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. PMID:20015858

Resco, Vctor; Querejeta, Jos I; Ogle, Kiona; Voltas, Jordi; Sebasti, Maria-Teresa; Serrano-Ortiz, Penlope; Linares, Juan C; Moreno-Gutirrez, Cristina; Herrero, Asier; Carreira, Jos A; Torres-Caabate, Patricia; Valladares, Fernando

2009-12-16

113

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

114

A biomarker based on the stable isotopes of nickel  

PubMed Central

The new stable isotope systems of transition metals are increasingly used to understand and quantify the impact of primitive microbial metabolisms on the modern and ancient Earth. To date, little effort has been expended on nickel (Ni) isotopes but there are good reasons to believe that this system may be more straightforward, and useful in this respect, than some others. Here, we present Ni stable isotope data for abiotic terrestrial samples and pure cultures of methanogens. The dataset for rocks reveals little isotopic variability and provides a lithologic baseline for terrestrial Ni isotope studies. In contrast, methanogens assimilate the light isotopes, yielding residual media with a complementary heavy isotopic enrichment. Methanogenesis may have evolved during or before the Archean, when methane could have been key to Earth's early systems. Our data suggest significant potential in Ni stable isotopes for identifying and quantifying methanogenesis on the early planet. Additionally, Ni stable isotope fractionation may well prove to be the fundamental unambiguous trace metal biomarker for methanogens.

Cameron, Vyllinniskii; Vance, Derek; Archer, Corey; House, Christopher H.

2009-01-01

115

Stable Isotope Studies of Cometary Analogue Materials.  

National Technical Information Service (NTIS)

Some preliminary experiments exploring the isotopic exchange of water and CO2 at low temperature are reported. The results indicate that isotopic signatures of these components may be lost even at sub-ambient temperatures and thus have implications for th...

I. A. Franchi C. M. O. Alexander C. T. Pillinger C. X. Mendoza-gomez J. M. Greenberg

1989-01-01

116

Multivariate Stable Isotope Analysis to Determine Linkages between Benzocaine Seizures  

NASA Astrophysics Data System (ADS)

In July 2010, a woman was jailed for nine years in the UK after the prosecution successfully argued that attempting to import a cutting agent was proof of involvement in a conspiracy to supply Cocaine. That landmark ruling provided law enforcement agencies with much greater scope to tackle those involved in this aspect of the drug trade, specifically targeting those importing the likes of benzocaine or lidocaine. Huge quantities of these compounds are imported into the UK and between May and August 2010, four shipments of Benzocaine amounting to more then 4 tons had been seized as part of Operation Kitley, a joint initiative between the UK Border Agency and the Serious Organised Crime Agency (SOCA). By diluting cocaine, traffickers can make it go a lot further for very little cost, leading to huge profits. In recent years, dealers have moved away from inert substances, like sugar and baby milk powder, in favour of active pharmaceutical ingredients (APIs), including anaesthetics like Benzocaine and Lidocaine. Both these mimic the numbing effect of cocaine, and resemble it closely in colour, texture and some chemical behaviours, making it easier to conceal the fact that the drug has been diluted. API cutting agents have helped traffickers to maintain steady supplies in the face of successful interdiction and even expand the market in the UK, particularly to young people aged from their mid teens to early twenties. From importation to street-level, the purity of the drug can be reduced up to a factor of 80 and street level cocaine can have a cocaine content as low as 1%. In view of the increasing use of Benzocaine as cutting agent for Cocaine, a study was carried out to investigate if 2H, 13C, 15N and 18O stable isotope signatures could be used in conjunction with multivariate chemometric data analysis to determine potential linkage between benzocaine exhibits seized from different locations or individuals to assist with investigation and prosecution of drug distribution network. More than 40 Benzocaine samples comprising both seized and control samples were analysed by two stable isotope forensic laboratories in two different countries (Australia and Scotland) to assess intra-lab reproducibility as well as inter-lab repeatability of measured stable isotope abundance values.

Kemp, H. F.; Meier-Augenstein, W.; Collins, M.; Salouros, H.; Cunningham, A.; Harrison, M.

2012-04-01

117

Biomedical Research Applications of Electromagnetically Separated Enriched Stable Isotopes.  

National Technical Information Service (NTIS)

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 radioisotope production, labeled compounds, a...

R. M. Lambrecht

1982-01-01

118

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

119

Stable isotopic composition of the active pharmaceutical ingredient (API) naproxen  

Microsoft Academic Search

A survey of the multi-stable isotopic composition of an active pharmaceutical ingredient (API), naproxen, was performed to assess the potential of Isotope Ratio Mass Spectrometry (IRMS) to distinguish the provenance of APIs. Twenty-six lots of naproxen from six manufacturers representing four countries (Italy, India, Ireland, and the USA) were analyzed for three isotope ratios (13C\\/12C, 18O\\/16O, and D\\/H). The samples

A. M. Wokovicha; J. A. Spencer; B. J. Westenberger; L. F. Buhse; J. P. Jasper

2005-01-01

120

Stable isotope composition of precipitation over southeast Asia  

Microsoft Academic Search

Spatial and temporal variability of the stable isotope composition of precipitation in the southeast Asia and western Pacific region is discussed, with emphasis on the China territory, based on the database of the International Atomic Energy Agency\\/World Meteorological Organization Global Network ``Isotopes in Precipitation'' and the available information on the regional climatology and atmospheric circulation patterns. The meteorological and pluviometric

Luis Aragufis-Aragufis; Klaus Froehlich; Kazimierz Rozanski

1998-01-01

121

Source partitioning using stable isotopes: coping with too many sources  

Microsoft Academic Search

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 stream. In general, the proportional contributions of n+1 different sources can be uniquely determined by the use of n

Donald L. Phillips; Jillian W. Gregg

2003-01-01

122

Stable isotopes sales: Mound customer and shipment summaries, FY 1985  

SciTech Connect

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-reference index by location is included for domestic and foreign customers. Cross-reference listings by isotope purchased are included for all customers.

Flayler, K.A. (comp.)

1987-12-15

123

Stable isotope sales: Mound customer and shipment summaries, FY 1986  

SciTech Connect

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 location and by isotope are included for all customers. 3 tabs.

Kramer, L.R. (ed.); Flayler, K.A. (comp.)

1988-05-20

124

Stable and Other Isotope Techniques for Perchlorate Source Identification  

Microsoft Academic Search

Stable isotopes of chlorine, oxygen, nitrogen, strontium, and hydrogen can be used as forensic indicators to fingerprint and possibly differentiate perchlorate plumes. Direct analytical methods involve isotope ratio mass spectrometry (IRMS) of ?Cl and ?O, which comprise the perchlorate anion (ClO4 ). Plots of ?Clperchlorate versus ? Operchlorate have been used to differentiate between anthropogenic and geogenic (natural) perchlorate sources.

William E. Motzer; Thomas K. G. Mohr; Sally McCraven; Phyllis Stanin

2006-01-01

125

Stable Isotope Tracers of Process in Great Lakes Food Webs  

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...

126

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

127

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

128

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 [(2)H3]-2-methylpyrazine (d-1), [(2)H5]-2-ethylpyrazine (d-2), [(2)H3]-2,3(or 6)-dimethylpyrazine (d-3A, d-3B), [(2)H3]-2,[(2)H3]-6-dimethylpyrazine (d-3C), [(2)H5]-2,[(2)H5]-6-diethylpyrazine (d-4), [(2)H5]-2-ethyl-3(or 6)-methylpyrazine (d-5A, d-5B), 2,[(2)H3]-3,5-trimethylpyrazine (d-6), [(2)H5]-2-ethyl-3,6-dimethylpyrazine (d-7), [(2)H5]-2-ethyl-3,5-dimethylpyrazine (d-8), and 2,3-diethyl-[(2)H3]-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

2013-04-09

129

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

130

Availability of enriched stable isotopes: present status and future prospects  

SciTech Connect

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, monisotopic elements, etc. The EMIEF can also be used to produce enriched samples of radioactive species, most notably the isotopes of uranium and plutonium. These enriched materials are placed in either the Sales Inventory of in the Research Materials Collection (RMC). The materials in the Sales Inventory are for sale to anyone on a first come, first served basis. Prices in the most recent catalog range from $0.05/mg for 99.8% /sup 140/Ce to $1,267/mg for 98.5% /sup 176/Lu. The materials in the RMC are made available to US researchers (or groups that include a US investigator) on a loan basis for use in non-destructive experiments and applications. In addition, certain samples have been provided to European investigators for cross-section studies through the auspices of EURATOM and the European-American Nuclear Data Committee. The status of the enriched isotopes included in the Sales Inventory is tabulated where isotopes are listed that are either not available or are in insufficient quantity or quality to meet current requests, as of 6/30/86. These can be summarized in the following subcategories: isotopes with zero inventory (22), Isotopes of insufficient quantity (17), and isotopes with insufficient enrichment quality (10). Of these 49 species, the supplies of 10 will be replenished by the scheduled FY86 enrichments in process (isotopes of bromine, calcium, nickel, potassium, rubidium, and strontium). In Table 3 are listed isotopes where the current inventory is less than the average annual sales level for the past five years. There are 47 isotopes listed, representing 25 different elements. Thus, there exists considerable potential for a substantial increase in the number of isotopes with zero inventory.

Hoff, R.W.

1986-09-18

131

Stable Isotope Dilution for Hazardous Waste Incineration.  

National Technical Information Service (NTIS)

The report gives results of a project to determine if a proposed catalytic exchange procedure could be adapted to produce the labeled analog materials necessary for isotope dilution gas chromatography/mass spectrometry (GC/MS) analysis. It is related to a...

P. W. Ryan

1984-01-01

132

The carbon stable isotope composition of pollen  

Microsoft Academic Search

The d13C value of plant tissue is increasingly used to infer environmental and ecological conditions in modern and ancient environments. Isolation techniques and morphological descriptions have been established that characterize plant pollen for the greater part of the Phanerozoic eon. If the d13C value of fossil pollen could be used as an indicator of the carbon isotope composition of ancient

A. Hope Jahren

2004-01-01

133

Sources of aerosol sulphate at Alert: Apportionment using stable isotopes  

Microsoft Academic Search

From July 1993 to September 1994, seasonal variations in the sources of SO42- aerosols in the Arctic lower atmosphere at Alert, Canada, (8230'N, 6220'W) were investigated using the sulphur isotope abundance of as little as 10 mug of sulphur analyzed by combustion-flow isotope-ratio mass spectrometry. In conjunction with air mass trajectories and in parallel with measurements of aerosol composition, the

A. L. Norman; L. A. Barrie; D. Toom-Sauntry; A. Sirois; H. R. Krouse; S. M. Li; S. Sharma

1999-01-01

134

Determination of minor isotope abundances in naturally occurring uranium materials. The tracing power of isotopic signatures for uranium.  

National Technical Information Service (NTIS)

The mass spectrometric determination of minor abundant isotopes, (sup 234)U and (sup 236)U in naturally occurring uranium materials requires instruments of high abundance sensitivity and the use of highly sensitive detection systems. In this study the the...

R. Ovaskainen

1999-01-01

135

Stable Isotope Ratios and the Forensic Analysis of Microorganisms  

SciTech Connect

In the aftermath of the anthrax letters of 2001, researchers have been exploring various analytical signatures for the purpose of characterizing the production environment of microorganisms. One such signature is stable isotope ratios, which in heterotrophs are a function of nutrient and water sources. Here we discuss the use of stable isotope ratios in microbe forensics, using as a database the carbon, nitrogen, oxygen and hydrogen stable isotope ratios of 247 separate cultures of B. subtilis 6051 spores produced on a total of 32 different culture media. In the context of using stable isotope ratios as a signature for sample matching, we present an analysis of variation between individual samples, between cultures produced in tandem, and between cultures produced in the same medium but at different times. Additionally, we correlate the stable isotope ratios of carbon, nitrogen, oxygen, and hydrogen for growth medium nutrients or water with those of spores and show examples of how these relationships can be used to exclude nutrient or water samples as possible growth substrates for specific cultures.

Kreuzer-Martin, Helen W.; Jarman, Kristin H.

2007-06-01

136

Stable Isotope Ratios and Forensic Analysis of Microorganisms?  

PubMed Central

In the aftermath of the anthrax letters of 2001, researchers have been exploring various analytical signatures for the purpose of characterizing the production environment of microorganisms. One such signature is stable isotope ratios, which in heterotrophs, are a function of nutrient and water sources. Here we discuss the use of stable isotope ratios in microbial forensics, using as a database the carbon, nitrogen, oxygen, and hydrogen stable isotope ratios of 247 separate cultures of Bacillus subtilis 6051 spores produced on a total of 32 different culture media. In the context of using stable isotope ratios as a signature for sample matching, we present an analysis of variations between individual samples, between cultures produced in tandem, and between cultures produced in the same medium but at different times. Additionally, we correlate the stable isotope ratios of carbon, nitrogen, oxygen, and hydrogen for growth medium nutrients or water with those of spores and show examples of how these relationships can be used to exclude nutrient or water samples as possible growth substrates for specific cultures.

Kreuzer-Martin, Helen W.; Jarman, Kristin H.

2007-01-01

137

Measurement of stable carbon isotope ratios of non-methane hydrocarbons and halocarbons  

NASA Astrophysics Data System (ADS)

Within the realm of volatile organic compounds, hydrocarbons and halocarbons form a sizable proportion of carbon input to the atmosphere. Within these compound categories, the light non-methane hydrocarbons (NMHC, two to seven carbon atoms) and monocarbon halocarbons have a special place as these have strong, if not exclusive, anthropogenic (human-caused) sources. With common atmospheric molar mixing ratios in the parts-per-trillion (10-12 mole/mole) to parts-per-billion (10-9 mole/mole) range, these trace gases, though decidedly minor constituants of the atmosphere, have diverse consequences due to their atmospheric presence and their removal processes. Effects range from causing ground level air pollution and resulting hazards to health, to contributing to anthropogenic climate change and the destruction of the ozone layer in the stratosphere, among many others. The existance of stable isotopes (otherwise identical atoms with varying amounts of neutrons that do not spontaneously disintegrate) in several elements relevant to atmospheric chemistry and physics is a boon to research. Their presence in molecules is detectable by mass and cause small intra- and intermolecular property changes. These changes range from the physical (e.g. boiling point variation) to the chemical (reaction rate variation) and can influence external interactions as well. The measurement of the ratio of a minor stable isotope of an element to the major one (the stable isotope ratio) can be used to establish source fingerprints, trace the interaction dynamics, and refine the understanding of the relative contribution of sources and sinks to the atmosphere as a whole. The stable minor stable isotope of carbon, 13C, has a natural abundance of approximately 1.1 %. It has a sufficient fractional mass difference from its major isotope as to cause significant effects, making it ideal for measuring the ratios and properties of hydro- and halocarbons. In order to enable a better understanding of the behavior of these compounds in terms of their sources, sinks, inter- and intramolecular processes, it was decided in 2006 to develop an instrument capable of selectively measuring NMHC mixing ratios and stable carbon isotope ratios for use in the laboratory of the Atmospheric Physics and Chemistry Group at Universiteit Utrecht. This thesis documents the successful development, construction, testing and first applications of this stable carbon isotope ratio instrument. It is divided into five chapters, representing the content of three publications and additional material: an introduction; a method section; and applications: analysis of NMHC stable carbon isotopes in urban ambient air, laboratory measurments of the isotope effects in UV degradation of monocarbon chlorofluorocarbons, isotope analysis of diverse gases from firn air samples from Greenland, plus a section on future perspectives

Zuiderweg, A. T.

2012-09-01

138

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

SciTech Connect

We present UNiquant, a new software program for analyzing stable isotope labeling (SIL) based quantitative proteomics data. UNiquant surpassed the performance of two other platforms, MaxQuant and Mascot Distiller, using complex proteome mixtures having either known or unknown heavy/light ratios. UNiquant is compatible with a broad spectrum of search engines and SIL methods, providing outstanding peptide pair identification and accurate measurement of the relative peptide/protein abundance.

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

2011-03-04

139

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

140

Partitioning peat respiration with stable carbon isotopes  

NASA Astrophysics Data System (ADS)

Equimolar production of CO2 and CH4 is assumed with methanogenesis. However, in both field and incubation studies of peat respiration, CO2 is continually reported to be in higher concentrations than CH4. It was assumed that this is due to loss of methane with ebullition and additional CO2 production by HMW organic matter fermentation. To determine the proportions of CO2 formed from both organic matter fermentation and methanogenesis and to determine the percent loss of CH4 from ebullition, isotope mass balance equations were developed. The 13C-CO2 measured in pore water represents a mixture between the 13C-CO2 from organic matter decomposition and methanogenesis. By collecting and analyzing pore water samples for ?13C and concentrations of both CO2 and CH4, the proportion of CO2 formed from organic matter fermentation and methanogenesis was calculated. It was found that, at 0, 154, and 261 cm depths, the percent CO2 from methanogenesis was 56%, 88%, and 91%, and the percent CH4 loss due to ebullition was 69%, 79%, and 85%, respectively. These findings indicate that with increasing depth both the percent CO2 formed from methanogenesis and the percent CH4 lost increased. Incubation experiments consisting of peat from five depth intervals (30-40, 70-80, 130-140, 170-180, and 270-280cm) were used to determine the accuracy of the isotope mass balance equations based on in situ concentrations and isotopic values. Measurements were made biweekly for concentrations and ?13C of CO2 and CH4. The percents of CO2 formed from methanogenesis based on the isotope mass balance equations were found to be to be 53%, 44%, 12%, 51%, and 54% corresponding to the respective depth ranges. The ratios of CH4/CO2 measured were 51%, 39%, 4%, 41%, and 54%, respectively. The average standard deviation between these sample sets was found to be 3.5%. This indicates that the isotope mass balance equations are an appropriate model for determining in situ CO2 partitioning in these systems.

Chanton, J.; Corbett, J.; Burdige, D. J.; Glaser, P. H.; Cooper, W. T.; Tfaily, M. M.

2010-12-01

141

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

142

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

143

Stable carbon isotope fractionation by methylotrophic methanogenic archaea.  

PubMed

In natural environments methane is usually produced by aceticlastic and hydrogenotrophic methanogenic archaea. However, some methanogens can use C(1) 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. PMID:22904062

Penger, Jrn; Conrad, Ralf; Blaser, Martin

2012-08-17

144

Eukaryotic expression system for the incorporation of stable isotopes into proteins  

US Patent & Trademark Office Database

Methods for producing stable isotope-labeled recombinant protein are provided. The methods include isolating a stable isotope-labeled recombinant protein from a Trichoplusia ni larva expressing a recombinant protein, which Trichoplusia ni larva has ingested a food source comprising stable isotope-labeled algae, thereby resulting in incorporation of a stable isotope into the recombinant protein to produce the stable isotope-labeled recombinant protein.

Kobilka; Brian (Palo Alto, CA); Bokoch; Michael (Menlo Park, CA)

2011-12-13

145

Stable isotope composition of water in desert plants  

Microsoft Academic Search

A survey of the stable isotope content of tissue waters of plants from the Negev desert was conducted. Large differences were\\u000a observed in the extent of enrichment of the heavy isotopes in leaf water relative to local precipitation among different plants.\\u000a This is apparently caused by the species-dependent stratagems adopted by the plants to cope with water stress, primarily by

J. R. Gat; D. Yakir; G. Goodfriend; P. Fritz; P. Trimborn; J. Lipp; I. Gev; E. Adar; Y. Waisel

2007-01-01

146

Stable isotopes and diet at Ancient Kerma, Upper Nubia (Sudan)  

Microsoft Academic Search

Carbon and nitrogen stable isotope values were measured from bone collagen extracted from archaeological Nubian human (n=54) and faunal (n=61) populations from the site of Kerma, Sudan. Collagen suitable for isotopic analysis was extracted from 22 faunal and 48 human samples from the Eastern cemetery site, dated to the Middle Kerma (c. 20501750 BC) and Classic Kerma (c. 17501500 BC)

A. H. Thompson; L. Chaix; M. P. Richards

2008-01-01

147

Stable and Radiogenic Isotopes in Biological Archaeology: Some Applications  

Microsoft Academic Search

\\u000a Stable isotope geochemistry has had a significant impact in archaeology and anthropology of ancient peoples. Regional gradients\\u000a in ?18O and 87Sr\\/86Sr are reflected in the bones and teeth of ancient humans and can be used to detect migration of individuals from their place\\u000a of birth or early life. Studies of carbon and nitrogen isotopes in bones and teeth reveal paleodiet

Henry P. Schwarcz; Christine D. White; Fred J. Longstaffe

148

Stable isotope systematics in Pleistocene deep-sea sediment records  

SciTech Connect

The distribution of stable isotopes of oxygen and carbon in deep-sea sediments is a prime information carrier in paleoceanography. Isotope stratigraphies from deep-sea cores provide a tool for correlation, as well as an index for monitoring paleoclimate. Stable isotope systematics have been examined at several levels: 1) Data precision. Stable isotope data quality for a number of foraminifera species and size fractions is assessed by performing multiple analyses on subgroups of a given sample. Error measures have been determined which can be used to plan sampling. 2) Benthic mixing. Stratigraphic signals recovered from the deep-sea have been subjected to distortion from the activity of benthic organisms. A quantitative look at the effects of the mixing on the recovery of stratigraphic signals is presented. The unmixing problem, that is the problem of recovering high-frequency information lost in the mixing process, is also examined. A technique is developed, which allows determination of the benthic mixing parameters from certain stratigraphic relationships in multiple delta/sup 18/O signals. 3) Sedimentation rate nonlinearity. Spectral analyses are almost routinely performed on deep-sea delta/sup 18/O records, usually with the intent of finding climatic driving signals. This type of analysis assumes a linear sedimentation rate. Nonlinearity of sedimentation rate is examined at two levels. A long period (500 ka) dissolution cycle in the late Pleistocene is examined. It is demonstrated that this dissolution has affected stable isotopes and that considerable carbonate material has been dissolved.

Schiffelbein, P.A.

1984-01-01

149

Martian stable isotopes: volatile evolution, climate change and exobiological implications.  

PubMed

Measurements of the ratios of stable isotopes in the martian atmosphere and crust provide fundamental information about the evolution of the martian volatile and climate system. Current best estimates of the isotope ratios indicate that there has been substantial loss of gases to space and exchange of gases between the atmosphere and the crust throughout geologic time; exchange may have occurred through circulation of water in hydrothermal systems. Processes of volatile evolution and exchange will fractionate the isotopes in a manner that complicates the possible interpretation of isotopic data in terms of any fractionation that may have been caused by martian biota, and must be understood first. Key measurements are suggested that will enhance our understanding of the non-biological fractionation of the isotopes and of the evolution of the martian volatile system. PMID:10077868

Jakosky, B M

1999-01-01

150

Stable Isotopic Tracing--A Way Forward for Nanotechnology  

PubMed Central

Numerous publications and reports have expressed health and safety concerns about the production and use of nanoparticles, especially in areas of exposure monitoring, personal use, and environmental fate and transport. We suggest that stable isotopic tracers, which have been used widely in the earth sciences and in metabolic and other health-related studies for several decades, could be used to address many of these issues. One such example we are pursuing is the use of stable isotopes to monitor dermal absorption of zinc and titanium oxides in sunscreen preparations and other personal care products. Other potential applications of this tracing approach are discussed.

Gulson, Brian; Wong, Herbert

2006-01-01

151

Stable isotopic composition of water vapor in the tropics  

NASA Astrophysics Data System (ADS)

Water vapor samples collected during tropical field experiments at Puerto Escondido, Mexico, near Kwajalein (KWAJEX), and near Key West, Florida (CAMEX 4), were analyzed for their stable isotope contents, 1H218O:1H216O and 2H1H16O:1H216O. Highest ?18O values approached isotopic equilibrium with seawater during quiescent weather or in regions of isolated or disorganized convection. Lowest ?18O values occurred in or downwind from regions of organized mesoscale weather disturbances and ranged as low as 15 below isotopic equilibrium with seawater. The mean ?18O value of vapor over the sea surface therefore decreases as storm activity and organization increases.

Lawrence, James Robert; Gedzelman, Stanley David; Dexheimer, Darielle; Cho, Hye-Khung; Carrie, Gordon D.; Gasparini, Robert; Anderson, Casey R.; Bowman, Kenneth P.; Biggerstaff, Mike I.

2004-03-01

152

Does avian malaria infection affect feather stable isotope signatures?  

PubMed

It is widely accepted that stable isotope ratios in inert tissues such as feather keratin reflect the dietary isotopic signature at the time of the tissue synthesis. However, some elements such as stable nitrogen isotopes can be affected by individual physiological state and nutritional stress. Using malaria infection experiment protocols, we estimated the possible effect of malaria parasite infections on feather carbon (?(13)C) and nitrogen (?(15)N) isotope signatures in juvenile common crossbills Loxia curvirostra. The birds were experimentally infected with Plasmodium relictum (lineage SGS1) and P. ashfordi (GRW2), two widespread parasites of passerines. Experimental birds developed heavy parasitemia of both parasites and maintained high levels throughout the experiment (33 days). We found no significant difference between experimental and control birds in both ?(13)C and ?(15)N values of feathers re-grown. The study shows that even heavy primary infections of malaria parasites do not affect feather ?(13)C and ?(15)N isotopic signatures. The results of this experiment demonstrate that feather isotope values of wild-caught birds accurately reflect the dietary isotopic sources at the time of tissue synthesis even when the animal's immune system might be challenged due to parasitic infection. PMID:21671039

Yohannes, Elizabeth; Palinauskas, Vaidas; Valki?nas, Gediminas; Lee, Raymond W; Bolshakov, Casimir V; Bensch, Staffan

2011-06-14

153

Isotopic Abundances of Eu, Ba, and Sm in Metal-Poor Stars  

NASA Astrophysics Data System (ADS)

We have examined the isotopic mix of the heavy neutron-capture elements Eu, Ba, and Sm in three metal-poor stars with different enrichment histories. Isotopic abundances are more fundamental than elemental abundances as probes of the contributions from the rapid and slow nucleosynthesis reactions. We show preliminary results from our study, the first to examine isotopic abundances of three elements simultaneously in the same star.

Roederer, Ian U.; Sneden, Chris; Lawler, James E.; Sobeck, Jennifer S.; Pilachowski, Catherine A.; Cowan, John J.

154

Investigating the diet of the omnivorous mirid Dicyphus hesperus using stable isotopes.  

PubMed

Omnivory involves numerous feeding relationships and a complex web of interactions. When using omnivores in biocontrol, these interactions need to be understood to maximize feeding on the target species and minimize non-target interactions. Dicyphus hesperus is used along with Encarsia formosa for biocontrol of whiteflies in greenhouse tomato crops. Dicyphus hesperus is a generalist omnivore which feeds on all components of the system. To quantify these interactions, stable isotope analysis was used to identify trophic position with nitrogen isotopes (delta15N) and plant sources with carbon isotopes (delta13C). Feeding trials were used to establish baseline isotopic data for D. hesperus and their diet, including Verbascum thapsus, an alternative plant food. Cage trials were used to monitor population abundances and the isotopic signature of D. hesperus. In feeding trials, D. hesperus were enriched relative to their food, suggesting an elevated trophic position. However, large amounts of isotopic variation were found within all diet components, with only V. thapsus exhibiting a distinct signature. In cage trials, the average delta15N and delta13C of the omnivore declined over time, coinciding with declines in total available prey, though it may be confounded by changes in temperature. The range of delta13C, but not the range of delta15N, also declined over time. This suggests a change in the plant source within the diet, but also some unquantified variability within the population. We suggest that diet variability exists within D. hesperus populations, declining as prey become less abundant. PMID:19159499

Bennett, J A; Gillespie, D R; VanLaerhoven, S L

2009-01-21

155

Neutron capture radiography: a technique for isotopic labelling and analytical imaging with a few stable isotopes.  

PubMed

NCR (neutron capture radiography) may be used successfully for the imaging of one of the stable isotopes of a few chemical elements (especially 6Li and 10B, possibly also 14N, 17O, and others) and for labelling experiments using these stable isotopes. Other physical techniques compete with NCR. However, NCR can remain extremely useful in a certain number of cases, because it is usually more easily done and is less expensive than the other techniques. PMID:16799738

Thellier, Michel; Ripoll, Camille

2006-06-19

156

Middle Pleistocene ecology and Neanderthal subsistence: Insights from stable isotope analyses in Payre (Ardche, southeastern France).  

PubMed

The Middle Palaeolithic site of Payre in southeastern France yields abundant archaeological material associated with fossil hominid remains. With its long sequence of Middle Pleistocene deposits, Payre is a key site to study the Middle Palaeolithic chronology of this region. This study is the first to investigate carbon and oxygen isotope contents of Neanderthal tooth enamel bioapatite, together with a wide range of herbivorous and carnivorous species. The aim is to contribute to the understanding of hunting behaviour, resource partitioning, diet and habitat use of animals and Neanderthals through a palaeoecological reconstruction. Local topography had a visible influence on carbon and oxygen stable isotope values recorded in herbivore tooth enamel. This was used to investigate possible habitats of herbivores. The different herbivorous species do not show large variations of their carbon and oxygen isotope values through time, indicating niche conservatism from OIS 8-7 to OIS 6-5, i.e., independently of palaeoclimatic and palaeoenvironmental variations. Based on these new observations, we conclude that Neanderthals employed a stable subsistence strategy over time, using a variety of local resources, with resource partitioning visible between humans and carnivores, especially wolves. A comparison of the results of stable isotopic investigation with the results of tooth wear analyses previously conducted on the same teeth allowed us to demonstrate that grazing and browsing do not bind animals to a specific habitat in a C3 environment as reflected in the isotopic values. PMID:23920410

Ecker, Michaela; Bocherens, Herv; Julien, Marie-Anne; Rivals, Florent; Raynal, Jean-Paul; Moncel, Marie-Hlne

2013-08-03

157

Vapor Pressure Isotope Effects and the Stable Isotope Geochemistry of the Martian Surface  

Microsoft Academic Search

The stable isotope geochemistry of light elements (H, C, N, O and S) is a tool in the search for evidence of life on bodies other than the earth for several reasons: the elements in question are used by all known or easily imagined life forms; several mass spectrometric and spectroscopic methods for measuring their isotopic compositions exist and are

J. M. Eiler

2002-01-01

158

Isotopic abundances - Inferences on solar system and planetary evolution  

NASA Astrophysics Data System (ADS)

For matter that has been removed from a region of nucleosynthetic activity and the effects of interactions with nuclear active particles, the only changes in nuclear abundances that can occur in an isolated system derive from the decay of radioactive nuclei of an element to yield the nucleus of another element. These two related nuclei furnish the absolute chronometers of geologic and cosmic time, through the decay of spontaneously radioactive parent nuclei and the accumulation of daughter nuclei. For systems related to such cosmic processes as the formation of the solar system from the precursor interstellar medium, and involving the very early evolution of the sun, there may arise considerable complexity, due to the intrinsic isotopic heterogeneity of the medium and the presence of short-lived nuclei.

Wasserburg, G. J.

1987-12-01

159

Stable isotope separation in calutrons: Forty years of production and distribution  

Microsoft Academic Search

The stable isotope separation program, established in 1945, has operated continually to provide enriched stable isotopes and selected radioactive isotopes, including the actinides, for use in research, medicine, and industrial applications. This report summarizes the first forty years of effort in the production and distribution of stable isotopes. Evolution of the program along with the research and development, chemical processing,

W. A. Bell; J. G. Tracy

1987-01-01

160

Stable isotope ecology in the Ituri Forest.  

PubMed

The Ituri Forest, Democratic Republic of Congo (formerly Zaire) is an example of a closed canopy forest showing extreme depletion in (13)C. delta(13)C values for plants from the canopy top, from gaps in the canopy, and from the subcanopy average -29.0+/-1.7 per thousand, -30.4+/-0.9 per thousand, and -34.0+/-1.5 per thousand, respectively. The delta(13)C of forest mammals show these differences, with the subcanopy browsers (okapi, dwarf antelope) having delta(13)C values for tooth enamel much more negative than subcanopy frugivores who derive their food from the canopy top, and from folivores and omnivores living in gap or clearing areas. Nitrogen isotopes in plants from this ecosystem have an average delta(15)N value of 5.4+/-1.8 per thousand and do not show significant differences at the 95% confidence interval between plants from the canopy top, from gaps in the canopy, and from the subcanopy. The delta(18)O(SMOW) values of surface waters in the study area are between -2.0 and -2.7. The delta(18)O(PDB) for tooth enamel ranged from -3 to +7 per thousand. PMID:14530961

Cerling, Thure E; Hart, John A; Hart, Terese B

2003-10-03

161

Potassium isotope abundances in Australasian tektites and microtektites.  

NASA Astrophysics Data System (ADS)

We report electron microprobe determinations of the elemental compositions of 11 Australasian layered tektites and 28 Australasian microtektites; and ion microprobe determinations of the 41K/39K ratios of all 11 tektites and 13 of the microtektites. The elemental compositions agree well with literature values, although the average potassium concentrations measured here for microtektites, 1.1 1.6 wt%, are lower than published average values, 1.9 2.9 wt%. The potassium isotope abundances of the Australasian layered tektites vary little. The average value of ?41K, 0.02 0.12 (1? mean), is indistinguishable from the terrestrial value (= 0 by definition) as represented by our standard, thereby confirming four earlier tektite analyses of Humayun and Koeberl (2004). In agreement with those authors, we conclude that evaporation has significantly altered neither the isotopic nor the elemental composition of Australasian layered tektites for elements less volatile than potassium. Although the average 41K/39K ratio of the microtektites, 1.1 1.7 (1? mean), is also statistically indistinguishable from the value for the standard, the individual ratios vary over a very large range, from -10.6 1.4 to +13.8 1.5 and at least three of them are significantly different from zero. We interpret these larger variations in terms of the evaporation of isotopically light potassium; condensation of potassium in the vapor plume; partial or complete stirring and quenching of the melts; and the possible uptake of potassium from seawater. That the average 41K/39K ratio of the microtektites equals the terrestrial value suggests that the microtektite-forming system was compositionally closed with respect to potassium and less volatile elements. The possibility remains open that 41K/39K ratios of microtektites vary systematically with location in the strewn field.

Herzog, G. F.; O'D. Alexander, C. M.; Berger, E. L.; Delaney, J. S.; Glass, B. P.

2008-10-01

162

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

163

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

164

Palaeoclimate reconstruction from stable isotope variations in speleothems: a review  

Microsoft Academic Search

Speleothems are now regarded as valuable archives of climatic conditions on the continents, offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores. They are ideal materials for precise U-series dating, yielding ages in calendar years, thereby circumventing the radiocarbon calibration problems associated with most other continental records. Stable isotope studies

Frank McDermott

2004-01-01

165

Stable Isotope Astrobiology at Hispanic Serving Institutions: Si Se Puede!  

NASA Astrophysics Data System (ADS)

A "crawl-walk-run" strategy has been used to create a strong, sustainable program in stable isotope geochemistry with an emphasis on astrobiology. The result was the creation of a vibrant program addressing the record of early life on Earth.

Melchiorre, E. B.; Lopez, A.; Velasquez, C. M.

2010-04-01

166

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...

167

Development of stable isotope mixing models in ecology - Perth  

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...

168

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...

169

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...

170

Applications of DNA-Stable Isotope Probing in Bioremediation Studies  

NASA Astrophysics Data System (ADS)

DNA-stable isotope probing, a method to identify active microorganisms without the prerequisite of cultivation, has been widely applied in the study of microorganisms involved in the degradation of environmental pollutants. Recent advances and technique considerations in applying DNA-SIP in bioremediation are highlighted. A detailed protocol of a DNA-SIP experiment is provided.

Chen, Yin; Vohra, Jyotsna; Murrell, J. Colin

171

Stable isotopes may provide evidence for starvation in reptiles.  

PubMed

Previous studies have attempted to correlate stable isotope signatures of tissues with the nutritional condition of birds, mammals, fishes, and invertebrates. Unfortunately, very little is known about the relationship between food limitation and the isotopic composition of reptiles. We examined the effects that starvation has on delta13C and delta15N signatures in the tissues (excreta, carcass, scales, and claws) of six, distantly related squamate reptiles (gaboon vipers, Bitis gabonica; ball pythons, Python regius; ratsnakes, Elaphe obsoleta; boa constrictors, Boa constrictor; western diamondback rattlesnakes, Crotalus atrox, and savannah monitor lizards, Varanus exanthematicus). Analyses revealed that the isotopic composition of reptile carcasses did not change significantly in response to bouts of starvation lasting up to 168 days. In contrast, the isotopic signatures of reptile excreta became significantly enriched in 15N and depleted in 13C during starvation. The isotopic signatures of reptile scales and lizard claws were less indicative of starvation time than those of excreta. We discuss the physiological mechanisms that might be responsible for the starvation-induced changes in 13C and 15N signatures in the excreta, and present a mixing model to describe the shift in excreted nitrogen source pools (i.e. from a labile source pool to a nonlabile source pool) that apparently occurs during starvation in these animals. The results of this study suggest that naturally occurring stable isotopes might ultimately have some utility for characterizing nitrogen and carbon stress among free-living reptiles. PMID:18613003

McCue, Marshall D; Pollock, Erik D

2008-08-01

172

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

2013-02-10

173

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.

174

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

175

Quantification in proteomics through stable isotope coding: a review.  

PubMed

This review focuses on techniques for quantification and identification in proteomics by stable isotope coding. Methods are examined for analyzing expression, post-translational modifications, protein:protein interactions, single amino acid polymorphism, and absolute quantification. The bulk of the quantification literature in proteomics focuses on expression analysis, where a wide variety of methods targeting different features of proteins are described. Methods for the analysis of post-translational modification (PTM) focus primarily on phosphorylation and glycosylation, where quantification is achieved in two ways, either by substitution or tagging of the PTM with an isotopically coded derivatizing agent in a single process or by coding and selecting PTM modified peptides in separate operations. Absolute quantification has been achieved by age-old internal standard methods, in which an isotopically labeled isoform of an analyte is synthesized and added to a mixture at a known concentration. One of the surprises is that isotope coding can be a valuable aid in the examination of intermolecular association of proteins through stimulus:response studies. Preliminary efforts to recognize single amino acid polymorphism are also described. The review ends with the conclusion that (1) isotope ratio analysis of protein concentration between samples does not necessarily relate directly to protein expression and rate of PTM and (2) that multiple new methods must be developed and applied simultaneously to make existing stable isotope quantification methods more meaningful. Although stable isotope coding is a powerful, wonderful new technique, multiple analytical issues must be solved for the technique to reach its full potential as a tool to study biological systems. PMID:15253416

Julka, Samir; Regnier, Fred

176

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

177

High Spatial Resolution Isotopic Abundance Measurements by Secondary Ion Mass Spectrometry: Status and Prospects  

NASA Astrophysics Data System (ADS)

Secondary Ion Mass Spectrometry, SIMS or ion microprobe analysis, has become an important tool for geochemistry because of its ability study the distributions of elemental and isotopic abundances in situ on polished samples with high (typically a few microns to sub-micron) spatial resolution. In addition, SIMS exhibits high sensitivity for a wide range of elements (H to Pu) so that isotope analyses can sometimes be performed for elements that comprise only trace quantities of some mineral phase (e.g., Pb in zircon) or on major and/or minor elements in very small samples (e.g., presolar dust grains). Offsetting these positive attributes are analytical difficulties due to the complexity of the sputtering source of analyte ions: (1) relatively efficient production of molecular ion species (especially from a complex matrix such as most natural minerals) that cause interferences at the same nominal mass as atomic ions of interest, and (2) quantitation problems caused by variations in the ionization efficiencies of different elements and/or isotopes depending upon the chemical state of the sample surface during sputtering--the so-called "matrix effects". Despite the availability of high mass resolution instruments (e.g., SHRIMP II/RG, CAMECA 1270/1280/NanoSIMS), the molecular ion interferences effectively limit the region of the mass table that can be investigated in most samples to isotope systems at Ni or lighter or at Os or heavier. The matrix effects and the sensitivity of instrumental mass discrimination to the physical state of the sample surface can hamper reproducibility and have contributed to a view that SIMS analyses, especially for so- called stable isotopes, are most appropriate for extraterrestrial samples which are often small, rare, and can exhibit large magnitude isotopic effects. Recent improvements in instrumentation and technique have extended the scope of SIMS isotopic analyses and applications now range from geochronology to paleoclimatology to volcanology to biogeochemistry and cosmochemistry. Multiple collector (static magnetic field) measurements at high mass resolving power have enabled high precision (sub-permil) for several stable isotopes systems (e.g., C, O, Mg, S). Applied to geochronology, the multiple collector approach permits very rapid survey of zircon Pb-Pb ages to identify candidate Hadean grains for further detailed analysis. Ion imaging has been used to correlate isotope compositions with biochemistry (e.g., FISH-SIMS) or to search for especially rare samples among larger populations (e.g., supernova grains of Stardust). For favorable sample geometries with lateral homogeneity, SIMS isotope analyses may be conducted in depth-profiling mode which brings spatial resolution into the tens of nm range. Applications of this approach include experimental petrology, thermochronology, and isotopic analyses of shallowly-implanted solar wind ions. New approaches to removal of molecular ion interferences include reverse- geometry instrumentation and accelerator-based SIMS. There always exists trade-offs between microanalysis and trace analysis on the one hand, and high precision on the other. In this contribution, I will review current status for isotope precision and accuracy of SIMS for applications in stable and radiogenic isotopes as a function of spatial scale. A discussion of current limits and future prospects for improvement in understanding matrix effects will be given. Examples from ion imaging/ depth profiling/ geochronology and cosmochemistry will be provided.

McKeegan, K. D.

2007-12-01

178

Use of the stable isotope (106)Cd for studying dietary cadmium absorption in humans.  

PubMed

Hydroponically grown wheat was intrinsically labelled with the stable isotope 106cadmium (106Cd) and the flour made into a porridge. The abundance of the isotope in the porridge was approximately 30 times the natural abundance, but the total level of Cd in the porridge was 0.03 mg/kg fresh weight, which was the same as expected in a normal diet. Cadmium measurements were made using inductively coupled plasma-mass spectrometry (ICP-MS). The porridge was eaten at breakfast by adult and infant volunteers. Bulked faecal collections were analysed for unabsorbed Cd. Initial results suggest that the apparent absorption of Cd may be higher than 5% as commonly quoted, but longer faecal collection times may be necessary to confirm this. PMID:10720732

Crews, H M; Owen, L M; Langford, N; Fairweather-Tait, S J; Fox, T E; Hubbard, L; Phillips, D

2000-03-15

179

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

180

Utilizing stable isotope abundances of lichens to monitor environmental change  

Microsoft Academic Search

Reported field observations, laboratory studies and transplant experiments confirm that lichens are affected by pollutants. The ubiquitous nature of lichens and their susceptibility to the environment suggest that their response to variations in atmospheric composition might provide a useful means for monitoring environmental quality. Through such monitoring, the detection of abnormal levels of defined pollutants in the atmosphere would be

Judith E. Batts; Lisa J. Calder; Barry D. Batts

2004-01-01

181

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

182

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

183

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

184

Abut sound science, stable isotope dilution, blasphemy and heresy.  

PubMed

The molar ratio between an analyte and its equal labeled with stable isotope(s), used as a bioanalytical IS, is here suggested as an essential (and currently not commonly applied) validation parameter. This parameter, when calculated and measured, gives the possibility for the bioanalyst to compare calibration graphs and QC samples over time independently of added amount of IS. Additionally, when QC samples and calibration samples do not agree it is obvious to identify where the discrepancies are. Whether calibration samples are needed when this parameter is extensively and carefully validated and understood, is also discussed. PMID:23937136

Svensson, Leif D

2013-08-01

185

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

186

Stable isotope composition of water vapor as an indicator of transpiration fluxes from rice crops  

NASA Astrophysics Data System (ADS)

Measurements of the stable isotope composition (?2H and ?18O) of water vapor and associated micrometeorological parameters were made before and after full establishment of a rice crop in southeastern Australia. The aim of the experiment was to gain a better understanding of stable isotope variations of water vapor near the ground surface in response to local evaporation, local transpiration, regional scale vapor transport and the vertical stability of the atmospheric boundary layer. Vapor samples were collected at several heights within 9 m of the water surface during two separate sampling periods. The ?2H values of the water vapor ranged over more than 60, reflecting major rapid changes in regional air mass sources, as well as variations in the stability of the lowest 10 m of the atmosphere. The influence of tropical and higher-latitude air masses resulted in local vapor compositions which were relatively enriched and depleted, respectively, in heavy isotopes. Vertical gradients in heavy isotope abundances were very large during stable conditions (as much as ??2H = -27 from 0.8 to 8.4 m), as the result of mixing between transpired water and regional air vapor. Transpiration fluxes calculated from the water vapor ?2H gradient ranged from 5 to 7 mm d-1, which was in good agreement with one-dimensional aerodynamic energy budget calculations of daytime vapor fluxes.

Brunel, J. P.; Simpson, H. J.; Herczeg, A. L.; Whitehead, R.; Walker, G. R.

1992-05-01

187

DNA Stable-Isotope Probing (DNA-SIP)  

PubMed Central

DNA stable-isotope probing (DNA-SIP) is a powerful technique for identifying active microorganisms that assimilate particular carbon substrates and nutrients into cellular biomass. As such, this cultivation-independent technique has been an important methodology for assigning metabolic function to the diverse communities inhabiting a wide range of terrestrial and aquatic environments. Following the incubation of an environmental sample with stable-isotope labelled compounds, extracted nucleic acid is subjected to density gradient ultracentrifugation and subsequent gradient fractionation to separate nucleic acids of differing densities. Purification of DNA from cesium chloride retrieves labelled and unlabelled DNA for subsequent molecular characterization (e.g. fingerprinting, microarrays, clone libraries, metagenomics). This JoVE video protocol provides visual step-by-step explanations of the protocol for density gradient ultracentrifugation, gradient fractionation and recovery of labelled DNA. The protocol also includes sample SIP data and highlights important tips and cautions that must be considered to ensure a successful DNA-SIP analysis.

Dunford, Eric A.; Neufeld, Josh D.

2010-01-01

188

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

189

Multi-year Stable Isotope Temperature Relationship, Summit, Greenland  

Microsoft Academic Search

In concert with a published (Shuman et al., 2001) and recently extended composite temperature record from satellite and automatic weather station (AWS) data at Summit, Greenland, (72.58*N, 38.53*W), a 2 m snow pit and a 6+ m shallow firn core, were recovered in May 2001. Analysis of these data has enabled the relationship of Summit temperatures and stable isotopes to

C. A. Shuman; J. L. Mann

2002-01-01

190

Stable Isotope Labeling with Amino acids in Nematodes  

PubMed Central

We describe an approach for the accurate quantitation of global protein dynamics in Caenorhabditis elegans. We adapted Stable Isotope Labeling with Amino acids in Cell culture (SILAC) for nematodes, by feeding worms a heavy lysine- and arginine-labeled E. coli strain. We also report a genetic solution to remove the arginine-to-proline conversion problem. Combining our approach with quantitative proteomics methods, we characterized the heatshock response in worms.

Larance, Mark; Bailly, Aymeric P.; Pourkarimi, Ehsan; Hay, Ronald T.; Buchanan, Grant; Coulthurst, Sarah; Xirodimas, Dimitris P.; Gartner, Anton; Lamond, Angus I.

2011-01-01

191

The use of stable carbon isotope analysis in rooting studies  

Microsoft Academic Search

Stable carbon isotope analysis was evaluated as a means of predicting the relative proportions of C3 and C4 root phytomass in species mixtures. The following mixtures of C3 and C4 species were used: 1) big bluestem (Andropogon gerardii)\\/cheatgrass (Bromus tectorum), 2) little bluestem (Schizachyrium scoparium)\\/cheatgrass, and 3) sorghum (Sorghum bicolor)\\/sunflower (Helianthus annuus). There was a significant correlation (P4 phytomass and

Tony J. Svejcar; Thomas W. Boutton

1985-01-01

192

Paleoclimate and Amerindians: Evidence from stable isotopes and atmospheric circulation  

PubMed Central

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 foothillsmountains vs. plains biomes; and from 8,0005,000 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, Marjorie Brooks; Frison, George C.; Tieszen, Larry L.

2001-01-01

193

Climatic signals in multiple highly resolved stable isotope records from Greenland  

Microsoft Academic Search

Twenty ice cores drilled in medium to high accumulation areas of the Greenland ice sheet have been used to extract seasonally resolved stable isotope records. Relationships between the seasonal stable isotope data and Greenland and Icelandic temperatures as well as atmospheric flow are investigated for the past 150200 years. The winter season stable isotope data are found to be influenced

B. M. Vinther; P. D. Jones; K. R. Briffa; H. B. Clausen; K. K. Andersen; D. Dahl-Jensen; S. J. Johnsen

2010-01-01

194

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

2013-08-30

195

Late Glacial Tropical Savannas in Sundaland Inferred From Stable Carbon Isotope Records of Cave Guano  

NASA Astrophysics Data System (ADS)

During the Last Glacial Period (LGP), reduced global sea level exposed the continental shelf south of Thailand to Sumatra, Java, and Borneo to form the contiguous continent of Sundaland. However, the type and extent of vegetation that existed on much of this exposed landmass during the LGP remains speculative. Extensive bird and bat guano deposits in caves throughout this region span beyond 40,000 yr BP, and contain a wealth of untapped stratigraphic palaeoenvironmental information. Stable carbon isotope ratios of insectivorous bird and bat guano contain a reliable record of the animal's diet and, through non-specific insect predation, reflect the relative abundance of major physiological pathways in plants. Various physiological pathways of carbon fixation in plants yield differing stable carbon isotope ratios. Stable carbon isotope values of C3 plants are lower than C4 vegetation due to different enzymatic discriminations of the heavy isotope through the carbon fixing pathways. In tropical locales, grasses nearly always follow the C4 photosynthetic pathway, whereas tropical rainforest uses C3 photosynthesis, providing a proxy for vegetation and therefore climate change in the past. Here we discuss four guano stable-isotope records, based on insect cuticle and n-alkane analysis, supplemented by pollen analysis. All sites suggest a C3 dominated ecosystem for the Holocene, consistent with the wet tropical forest vegetation present at all locations. Two sites from Palawan Island, Philippines, record stable carbon isotope values of guano that document a drastic change from C3 (forest) to C4 (savanna) dominated ecosystems during the Last Glacial Maximum (LGM). A third location, at Niah Great Cave, Malaysia, indicates C3-dominant vegetation throughout the record, but does display variation in stable carbon isotope values likely linked to humidity changes. A fourth location, Batu Caves in Peninsular Malaysia, also indicates open vegetation during the LGM. Vegetation models disagree as to the nature of vegetation during the LGM in Sundaland, but our results suggest major contraction of forest area with significant implications for carbon storage during the LGM and also for understanding the development of modern biogeographic and genetic patterns in the region. Additional cave guano sites will provide further constraints on the nature of environmental change in the region over the last glacial cycle.

Wurster, C. M.; Bird, M. I.; Bull, I.; Dungait, J.; Bryant, C. L.; Ertun, T.; Hunt, C.; Lewis, H. A.; Paz, V.

2008-12-01

196

Sensitivity of stable water isotopic values to convective parameterization schemes  

NASA Astrophysics Data System (ADS)

Convective parameterization has been argued as a principal generator of inter-model differences in climate sensitivity, but it is difficult in practice to constrain simulated convective processes. Here we show how stable water vapor isotopes, which are sensitive to the convective condensation rates, may be useful for evaluating convective parameterizations. By varying one of the least constrained convection parameters in the NCAR Community Atmosphere Model (CAM), namely the timescale for consumption of convective available potential energy (CAPE), ?, the simulated precipitation experiences substantial changes in response to changes in both the deep and shallow convection schemesincreasing ? from the standard 2 hours to 8 hours increases the contribution from shallow convection. The lowest order effect of increasing ? is a decrease (increase) in lower (upper) tropospheric condensation rates, with approximately the opposite vertical structure for the change in simulated isotopic signature. Increasing ? from the standard 2 hours to 8 hours also provides a better match to satellite-observed water vapor isotope ratios, albeit with some uncertainty related to the quality of currently-available satellite measurements. Thus, the incorporation of water vapor isotopes into GCMs provides additional constraints on convective parameterizations, especially as more and better quality water vapor isotope measurements become available.

Lee, Jung-Eun; Pierrehumbert, Raymond; Swann, Abigail; Lintner, Benjamin R.

2009-12-01

197

Estimation of evapotranspiration rate in irrigated lands using stable isotopes  

NASA Astrophysics Data System (ADS)

Agriculture in the Aral Sea basin is the main consumer of water resources and due to the current agricultural management practices inefficient water usage causes huge losses of freshwater resources. There is huge potential to save water resources in order to reach a more efficient water use in irrigated areas. Therefore, research is required to reveal the mechanisms of hydrological fluxes in irrigated areas. This paper focuses on estimation of evapotranspiration which is one of the crucial components in the water balance of irrigated lands. Our main objective is to estimate the rate of evapotranspiration on irrigated lands and partitioning of evaporation into transpiration using stable isotopes measurements. Experiments has done in 2 different soil types (sandy and sandy loam) irrigated areas in Ferghana Valley (Uzbekistan). Soil samples were collected during the vegetation period. The soil water from these samples was extracted via a cryogenic extraction method and analyzed for the isotopic ratio of the water isotopes (2H and 18O) based on a laser spectroscopy method (DLT 100, Los Gatos USA). Evapotranspiration rates were estimated with Isotope Mass Balance method. The results of evapotranspiration obtained using isotope mass balance method is compared with the results of Catchment Modeling Framework -1D model results which has done in the same area and the same time.

Umirzakov, Gulomjon; Windhorst, David; Forkutsa, Irina; Brauer, Lutz; Frede, Hans-Georg

2013-04-01

198

Geographic variation of stable isotopes in African elephant ivory  

NASA Astrophysics Data System (ADS)

In 1989, the international community listed the African elephant in Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) thus prohibiting commercial ivory trade. Recent surveillance data show that the illegal trade in ivory has been growing worldwide. Long-term preservation of many of the African elephant populations can be supported with a control mechanism that helps with the implementation of remedial conservation action. Therefore, setting up a reference database that predicts the origin of ivory specimens can assist in determining smuggling routes and the provenance of illegal ivory. Our research builds on earlier work to seek an appropriate method for determining the area of origin for individual tusks. Several researchers have shown that the provenance of elephant ivory can be traced by its isotopic composition, but this is the first attempt to produce an integrated isotopic reference database of elephant ivory provenance. We applied a combination of various routine geochemical analyses to measure the stable isotope ratios of hydrogen, carbon, nitrogen, oxygen, and sulphur. Up to now, we analysed 606 ivory samples of known geographical origin from African range states, museums and private collections, comprising 22 African elephant range states. The isotopic measurements were superimposed with data layers from vegetation, geology and climate. A regression function for the isotope composition of the water isotopes in precipitation and collagen in ivory was developed to overcome the problem of imprecise origin of some of the sampled material. Multivariate statistics, such as nearest neighborhood and discriminate analysis were applied to eventually allow a statistical determination of the provenance for ivory of unknown origin. Our results suggest that the combination of isotopic parameters have the potential to provide predictable and complementary markers for estimating the origin of seized elephant ivory.

Ziegler, S.; Merker, S.; Jacob, D.

2012-04-01

199

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

200

Stable isotope ratios in hair and teeth reflect biologic rhythms.  

PubMed

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. PMID:17653263

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

2007-07-25

201

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

202

Raman Spectroscopic Studies of Isotopic Diatomic Molecules and a Technique for Measuring Stable Isotope Ratios Using Raman Scattering.  

National Technical Information Service (NTIS)

A method for measuring stable isotope ratios using Raman scattering has been developed. This method consists of simultaneously counting photons scattered out of a high-intensity laser beam by different isotopically-substituted molecules. A number of studi...

R. C. Harney

1976-01-01

203

Isolation and derivatization of plasma taurine for stable isotope analysis by gas chromatography-mass spectrometry  

SciTech Connect

A method for the isolation and derivatization of plasma taurine is described that allows stable isotope determinations of taurine to be made by gas chromatography-mass spectrometry. The isolation procedure can be applied to 0.1 ml of plasma; the recovery of plasma taurine was 70 to 80%. For gc separation, taurine was converted to its dimethylaminomethylene methyl ester derivative which could not be detected by hydrogen flame ionization, but could be monitored readily by NH/sub 3/ chemical ionization mass spectrometry. The derivatization reaction occurred partially on-column and required optimization of injection conditions. Using stable isotope ratiometry multiple ion detection, (M + 2 + H)/sup +//(M + H)/sup +/ ion ratio of natural abundance taurine was determined with a standard deviation of less than +-0.07% of the ratio. The (1,2-/sup 13/C)taurine/taurine mole ratios of standard mixtures could be accurately determined to 0.001. This stable isotope gc-ms method is suitable for studying the plasma kinetics of (1,2-/sup 13/C)taurine in infants who are at risk with respect to taurine depletion.

Irving, C.S.; Klein, P.D.

1980-09-01

204

High-precision mass spectrometric analysis using stable isotopes in studies of children.  

PubMed

The use of stable isotopes combined with mass spectrometry (MS) provides insight into metabolic processes within the body. Herein, an overview on the relevance of stable isotope methodology in pediatric research is presented. Applications for the use of stable isotopes with MS cover carbohydrate, fat, and amino acid metabolism as well as body composition, energy expenditure, and the synthesis of specific peptides and proteins, such as glutathione and albumin. The main focus of these studies is on the interactions between nutrients and the endogenous metabolism within the body and how these factors affect the health of a growing infant. Considering that the early imprinting of metabolic processes hugely impacts metabolism (and thus functional outcome) later in life, research in this area is important and is advancing rapidly. The major fluxes on a metabolic level are the synthesis and breakdown rates. They can be quantified using kinetic tracer analysis and mathematical modeling. Organic MS and isotope ratio mass spectrometry (IRMS) are the two most mature techniques for the isotopic analysis of compounds. Introduction of the samples is usually done by coupling gas chromatography (GC) to either IRMS or MS because it is the most robust technique for specific isotopic analysis of volatile compounds. In addition, liquid chromatography (LC) is now being used more often as a tool for sample introduction of both volatile and non-volatile compounds into IRMS or MS for (13)C isotopic analyses at natural abundances and for (13)C-labeled enriched compounds. The availability of samples is often limited in pediatric patients. Therefore, sample size restriction is important when developing new methods. Also, the availability of stable isotope-labeled substrates is necessary for measurements of the kinetics and concentrations in metabolic studies, which can be a limiting factor. During the last decade, the availability of these substrates has increased. Furthermore, improvements in the accuracy, precision, and sensitivity of existing techniques (such as GC/IRMS) and the development of new techniques (such as LC/IRMS) have opened up new avenues for tackling these limitations. PMID:21769910

Schierbeek, Henk; van den Akker, Chris H P; Fay, Laurent B; van Goudoever, Johannes B

2011-07-18

205

Magnesium stable isotope composition of Earth's upper mantle  

NASA Astrophysics Data System (ADS)

The mantle is Earth's largest reservoir of Mg containing > 99% of Earth's Mg inventory. However, no consensus exists on the stable Mg isotope composition of the Earth's mantle or how variable it is and, in particular, whether the mantle has the same stable Mg isotope composition as chondrite meteorites. We have determined the Mg isotope composition of olivine from 22 mantle peridotites from eastern Australia, west Antarctica, Jordan, Yemen and southwest Greenland by pseudo-high-resolution MC-ICP-MS on Mg purified to > 99%. The samples include fertile lherzolites, depleted harzburgites and dunites, cryptically metasomatised ('dry') peridotites and modally metasomatised apatite amphibole-bearing harzburgites and wehrlites. Olivine from these samples of early Archaean through to Permian lithospheric mantle have ?25Mg DSM-3 = - 0.22 to - 0.08. These data indicate the bulk upper mantle as represented by peridotite olivine is homogeneous within current analytical uncertainties (external reproducibility ? 0.07 [2 sd]). We find no systematic ?25Mg variations with location, lithospheric age, peridotite fertility, or degree or nature of mantle metasomatism. Although pyroxene may have slightly heavier ?25Mg than coexisting olivine, any fractionation between mantle pyroxene and olivine is also within current analytical uncertainties with a mean ?25Mg pyr-ol = +0.06 0.10 (2 sd; n = 5). Our average mantle olivine ?25Mg DSM-3 = - 0.14 0.07 and ?26Mg DSM-3 = - 0.27 0.14 (2 sd) are indistinguishable from the average of data previously reported for terrestrial basalts, confirming that basalts have stable Mg isotope compositions representative of the mantle. Olivine from five pallasite meteorites have ?25Mg DSM-3 = - 0.16 to - 0.11 that are identical to terrestrial olivine and indistinguishable from the average ?25Mg previously reported for chondrites. These data provide no evidence for measurable heterogeneity in the stable Mg isotope composition of the source material in the proto-planetary disc from which Earth and chondrite and pallasite parent bodies accreted.

Handler, Monica R.; Baker, Joel A.; Schiller, Martin; Bennett, Vickie C.; Yaxley, Gregory M.

2009-05-01

206

Stable isotopes and elasmobranchs: tissue types, methods, applications and assumptions.  

PubMed

Stable-isotope analysis (SIA) can act as a powerful ecological tracer with which to examine diet, trophic position and movement, as well as more complex questions pertaining to community dynamics and feeding strategies or behaviour among aquatic organisms. With major advances in the understanding of the methodological approaches and assumptions of SIA through dedicated experimental work in the broader literature coupled with the inherent difficulty of studying typically large, highly mobile marine predators, SIA is increasingly being used to investigate the ecology of elasmobranchs (sharks, skates and rays). Here, the current state of SIA in elasmobranchs is reviewed, focusing on available tissues for analysis, methodological issues relating to the effects of lipid extraction and urea, the experimental dynamics of isotopic incorporation, diet-tissue discrimination factors, estimating trophic position, diet and mixing models and individual specialization and niche-width analyses. These areas are discussed in terms of assumptions made when applying SIA to the study of elasmobranch ecology and the requirement that investigators standardize analytical approaches. Recommendations are made for future SIA experimental work that would improve understanding of stable-isotope dynamics and advance their application in the study of sharks, skates and rays. PMID:22497393

Hussey, N E; MacNeil, M A; Olin, J A; McMeans, B C; Kinney, M J; Chapman, D D; Fisk, A T

2012-03-19

207

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

208

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

209

Combining sources in stable isotope mixing models: alternative methods.  

PubMed

Stable isotope mixing models are often used to quantify source contributions to a mixture. Examples include pollution source identification; trophic web studies; analysis of water sources for soils, plants; or water bodies, and many others. A common problem is having too many sources to allow a unique solution. We discuss two alternative procedures for addressing this problem. One option is a priori to combine sources with similar signatures so the number of sources is small enough to provide a unique solution. Aggregation should be considered only when isotopic signatures of clustered sources are not significantly different, and sources are related so the combined source group has some functional significance. For example, in a food web analysis, lumping several species within a trophic guild allows more interpretable results than lumping disparate food sources, even if they have similar isotopic signatures. One result of combining mixing model sources is increased uncertainty of the combined end-member isotopic signatures and consequently the source contribution estimates; this effect can be quantified using the IsoError model (http://www.epa.gov/wed/pages/models/isotopes/isoerror1_04.htm). As an alternative to lumping sources before a mixing analysis, the IsoSource mixing model (http://www.epa.gov/wed/pages/models/isosource/isosource.htm) can be used to find all feasible solutions of source contributions consistent with isotopic mass balance. While ranges of feasible contributions for each individual source can often be quite broad, contributions from functionally related groups of sources can be summed a posteriori, producing a range of solutions for the aggregate source that may be considerably narrower. A paleo-human dietary analysis example illustrates this method, which involves a terrestrial meat food source, a combination of three terrestrial plant foods, and a combination of three marine foods. In this case, a posteriori aggregation of sources allowed strong conclusions about temporal shifts in marine versus terrestrial diets that would not have otherwise been discerned. PMID:15711995

Phillips, Donald L; Newsome, Seth D; Gregg, Jillian W

2005-02-16

210

Thermal Neutron Capture onto the Stable Tungsten Isotopes  

NASA Astrophysics Data System (ADS)

Thermal neutron-capture measurements of the stable tungsten isotopes have been carried out using the guided thermal-neutron beam at the Budapest Reactor. Prompt singles spectra were collected and analyzed using the HYPERMET ?-ray analysis software package for the compound tungsten systems 183W, 184W, and 187W, prepared from isotopically-enriched samples of 182W, 183W, and 186W, respectively. These new data provide both confirmation and new insights into the decay schemes and structure of the tungsten isotopes reported in the Evaluated Gamma-ray Activation File based upon previous elemental analysis. The experimental data have also been compared to Monte Carlo simulations of ?-ray emission following the thermal neutron-capture process using the statistical-decay code DICEBOX. Together, the experimental cross sections and modeledfeeding contribution from the quasi continuum, have been used to determine the total radiative thermal neutron-capture cross sections for the tungsten isotopes and provide improved decay-scheme information for the structural- and neutron-data libraries.

Hurst, A. M.; Firestone, R. B.; Sleaford, B. W.; Summers, N. C.; Revay, Zs.; Szentmiklsi, L.; Belgya, T.; Basunia, M. S.; Capote, R.; Choi, H.; Dashdorj, D.; Escher, J.; Krticka, M.; Nichols, A.

2012-02-01

211

Stable isotope profiling of burnt wooden safety matches.  

PubMed

Arson is a significant problem around the world, and is a crime which results in a low number of convictions. The scene of an arson can be varied, commercial, residential or national park, and recently cases have been identified which were initiated by a lit match. Matches can be recovered from a scene, usually in a burnt condition. The benefit of analysing unburnt matches has been researched previously. In most cases, burnt matches are recovered from scenes, and therefore the research was extended to investigate the potential of using IRMS to analyse burnt matches. This includes samples which have been exposed to petrol, and various fire extinguishing chemicals. Matches were sectioned to reveal central unburnt portions of wood and analysed by isotope ratio mass spectrometry (IRMS). The stable isotope profile (SIP) of the wooden matchstick samples was unaffected by the presence of both petrol and a variety of fire extinguisher chemicals. Any changes seen could be attributed to the natural variability of isotopic composition encountered in a natural material such as wood. These findings were confirmed by the isotope analysis of 19 matchstick samples placed in mock fire training scenarios. The data was examined using a paired t-test and Hotellings T2 test for a single sample. PMID:19606589

Farmer, Nicola; Curran, James; Lucy, David; Daeid, Niamh Nic; Meier-Augenstein, Wolfram

2009-06-01

212

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

2013-09-10

213

Stable isotope ratios and uric acid preservation in termites belonging to three feeding habits in Thailand.  

PubMed

Nitrogen and carbon stable isotope ratios and uric acid concentrations in termites sampled from a dry evergreen forest in Thailand, were determined across three kinds of feeding habits. Feeding habits of Microcerotermes crassus, which is an abundant wood-feeder, and Dicuspiditermes makhamensis, a common soil-feeding termite, were confirmed by isotopic signatures. Lichen feeding termites (Hospitalitermes birmanicus, H. bicolor and H. ataramensis) were characterized by low delta15N values, suggesting that they assimilated nitrogen deposited from the atmosphere. There was also a significant difference in uric acid concentrations between termites representing different feeding habits. No significant relationships were found between uric acid concentrations and delta15N or delta13C in Hospitalitermes. However, delta15N values were correlated with C/N ratios in H. birmanicus, except in one colony of H. ataramensis. delta13C values in both species were negatively correlated with C/N ratios. PMID:11501704

Tayasu, I; Hyodo, F; Takematsu, Y; Sugimoto, A; Inoue, T; Kirtibutr, N; Abe, T

2000-01-01

214

Fire effects on stable isotopes in a Sierran forested watershed.  

PubMed

This study tested the hypothesis that stable C and N isotope values in surface soil and litter would be increased by fire due to volatilization of lighter isotopes. The hypothesis was tested by: (1) performing experimental laboratory burns of organic and mineral soil materials from a watershed at combinations of temperature ranging 100 to 600 degrees C and duration ranging from 1 to 60 min; (2) testing field samples of upland soils before, shortly after, and 1 yr following a wildfire in the same watershed; and (3) testing field soil samples from a down-gradient ash/sediment depositional area in a riparian zone following a runoff event after the wildfire. Muffle furnace results indicated the most effective temperature range for using stable isotopes for tracing fire impacts is 200 to 400 degrees C because lower burn temperatures may not produce strong isotopic shifts, and at temperatures>or=600 degrees C, N and C content of residual material is too low. Analyses of field soil samples were inconclusive: there was a slightly significant effect of the wildfire on delta15N values in upland watershed analyses 1 yr postburn, while riparian zone analyses results indicated that delta13C values significantly decreased approximately 0.71 per thousand over a 9 mo post-fire period (p=0.015), and ash/sediment layer delta13C values were approximately 0.65 per thousand higher than those in the A horizon. The lack of field confirmation may have been due to overall wildfire burn temperatures being <200 degrees C and/or microbial recovery and vegetative growth in the field. Thus, the muffle furnace experiment supported the hypothesis, but it is as yet unconfirmed by actual wildfire field data. PMID:17215216

Saito, Laurel; Miller, Wally W; Johnson, Dale W; Qualls, Robert G; Provencher, Louis; Carroll, Erin; Szameitat, Peter

2007-01-09

215

High-precision measurement of chlorine stable isotope ratios  

USGS Publications Warehouse

We present an analysis procedure that allows stable isotopes of chlorine to be analyzed with precision sufficient for geological and hydrological studies. The total analytical precision is ?????0.09%., and the present known range of chloride in the surface and near-surface environment is 3.5???. As Cl- is essentially nonreactive in natural aquatic environments, it is a conservative tracer and its ??37Cl is also conservative. Thus, the ??37Cl parameter is valuable for quantitative evaluation of mixing of different sources of chloride in brines and aquifers. ?? 1993.

Long, A.; Eastoe, c. J.; Kaufmann, R. S.; Martin, J. G.; Wirt, L.; Finley, J. B.

1993-01-01

216

On the volatile inventory of Titan from isotopic abundances in nitrogen and methane  

Microsoft Academic Search

We analyze recently published nitrogen and hydrogen isotopic data to constrain the initial volatile abundances on Saturns giant moon Titan. The nitrogen data are interpreted in terms of a model of non-thermal escape processes that lead to enhancement in the heavier isotope. We show that these data do not, in fact, strongly constrain the abundance of nitrogen present in Titans

Jonathan I. Lunine; Yuk L. Yung; Ralph D. Lorenz

1999-01-01

217

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

218

Applications of stable isotopes to study plant-animal relationships in terrestrial ecosystems  

Microsoft Academic Search

As natural tracers, stable isotopes have been extensively used in plant physiological, ecological and envi- ronmental research. Recently, animal physiological ecologists have also applied stable isotope techniques to study plant- animal relationships. The isotopic compositions of animal body generally reflect and integrate their diets over a time period ranging from hours to years to the lifetime of an indi- vidual.

Jianzhu WANG; Guanghui Lin; Jianhui Huang; Xingguo Han

2004-01-01

219

Chromium Stable Isotope Fractionation During Bacterial Reduction of Hexavalent Chromium  

NASA Astrophysics Data System (ADS)

Chromium is a common contaminant in surface water and ground water. It is redox-active, occurring as Cr(VI), which is soluble and toxic, and Cr(III), which is insoluble and less toxic. Reduction of Cr(VI) to Cr(III) is often the most important reaction controlling attenuation of Cr plumes, and Cr stable isotope (53Cr/52Cr) measurements show great promise as indicators of this reaction. Previous results indicate Cr(VI) reduction involves a kinetic isotope effect; lighter isotopes reduce at greater rates and heavier isotopes become increasingly enriched in the remaining Cr(VI) with increasing extent of reduction. If the size of this effect can be constrained well, then precise estimates of reduction are possible. The few experiments completed to date involved abiotic Cr(VI) reduction and indicated a fractionation factor of 1000ln? = 3.4 0.2. Abiotic reduction by Fe(II), organic compounds, and other agents is possible in natural settings, but some bacteria are known to reduce Cr(VI) as well. This study determined Cr fractionation factors for anaerobic reduction by Shewanella Oneidensis MR-1. Previous studies of kinetic isotope effects during reduction of sulfate, selenate, and nitrate reveal that fractionation factors depend on the metabolic states of the bacteria. Those in rich media usually induce less fractionation than those in leaner conditions. Concentrations of electron donors and other nutrients are usually small in natural settings, so we suspended MR-1 cells in buffer solutions with small concentrations of lactate or formate, and Cr(VI). Reduction occurred slowly, over days or weeks. The calculated value of 1000ln? was 4.1 0.2 for several experiments with a range of donor concentrations between 3.6 and 100 micromolar. This suggests that under the lean conditions found in most aquifers, the kinetic isotope effect induced by bacterial reduction is roughly equal to that induced by abiotic reduction, and that the Cr isotope method will be useful for estimating Cr(VI) reduction regardless of the exact mechanism involved.

Sikora, E. R.; Johnson, T. M.; Bullen, T. D.

2004-05-01

220

Abundance of solar wind magnesium isotopes determined with WIND/MASS  

NASA Astrophysics Data System (ADS)

We present first results of the abundance ratios of Mg isotopes in the solar wind using the high resolution mass spectrometer on the WIND spacecraft. The isotopic composition of Mg in the solar wind is consistent with terrestrial values. Our preliminary result is 24Mg:25Mg:26Mg=(0.792+/-0.006):(0.095+/-0.005):(0.113+/-0.005).

Bochsler, P.; Gonin, M.; Sheldon, R. B.; Zurbuchen, Th.; Gloeckler, G.; Hamilton, D. C.; Collier, M. R.; Hovestadt, D.

1996-07-01

221

Mercury emissions and stable isotopic compositions at Vulcano Island (Italy)  

NASA Astrophysics Data System (ADS)

Sampling and analyses methods for determining the stable isotopic compositions of Hg in an active volcanic system were tested and optimized at the volcanic complex of Vulcano (Aeolian Islands, Italy). Condensed gaseous fumarole Hg (fum)T, plume gaseous elemental Hg (g)0 and plume particulate Hg (p)II were obtained at fumaroles F0, F5, F11, and FA. The average total Hg emissions, based on Hg T/SO 2 in condensed fumarolic gases and plumes, range from 2.5 to 10.1 kg y - 1 , in agreement with published values [Ferrara, R., Mazzolai, B., Lanzillotta, E., Nucaro, E., Pirrone, N., 2000. Volcanoes as emission sources of atmospheric mercury in the Mediterranean Basin. Sci. Total Environ. 259(1-3), 115-121; Aiuppa, A., Bagnato, E., Witt, M.L.I., Mather, T.A., Parello, F., Pyle, D.M., Martin, R.S., 2007. Real-time simultaneous detection of volcanic Hg and SO 2 at La Fossa Crater, Vulcano (Aeolian Islands, Sicily). Geophys. Res. Lett. 34(L21307).]. Plume Hg (p)II increases with distance from the fumarole vent, at the expense of Hg (g)0 and indicates significant in-plume oxidation and condensation of fumarole Hg (fum)T. Relative to the NIST SRM 3133 Hg standard, the stable isotopic compositions of Hg are ? 202Hg (fum)T = - 0.74 0.18 (2SD, n = 4) for condensed gaseous fumarole Hg (fum)T, ? 202Hg (g)0 = - 1.74 0.36 (2SD, n = 1) for plume gaseous elemental Hg (g)0 at the F0 fumarole, and ? 202Hg (p)II = - 0.11 0.18 (2SD, n = 4) for plume particulate Hg (p)II. The enrichment of Hg (p)II in the heavy isotopes and Hg (g)0 in the light isotopes relative to the total condensed fumarolic Hg (fum)T gas complements the speciation data and demonstrates a gas-particle fractionation occurring after the gas expulsion in ambient T atmosphere. A first order Rayleigh equilibrium condensation isotope fractionation model yields a fractionation factor ? cond-gas of 1.00135 0.00058.

Zambardi, T.; Sonke, J. E.; Toutain, J. P.; Sortino, F.; Shinohara, H.

2009-01-01

222

Stable isotope labeling of Arabidopsis thaliana cells and quantitative proteomics by mass spectrometry.  

PubMed

Quantitative analysis of protein expression is an important tool for the examination of complex biological systems. Albeit its importance, quantitative proteomics is still a challenging task because of the high dynamic range of protein amounts in the cell and the variation in the physical properties of proteins. Stable isotope labeling by amino acids in cell culture (SILAC) has been successfully used in yeast and mammalian cells to measure relative protein abundance by mass spectrometry. Here we show for the first time that proteins from Arabidopsis thaliana cell cultures can be selectively isotope-labeled in vivo by growing cells in the presence of a single stable isotope-labeled amino acid. Among the tested amino acids ([2H3]-leucine, [13C6]arginine, and [2H4]lysine), [13C6]arginine proved to be the most suitable. Incorporation of [13C6]arginine into the proteome was homogeneous and reached efficiencies of about 80%. [13C6]Arginine-labeled A. thaliana suspension cells were used to study the regulation of glutathione S-transferase expression in response to abiotic stress caused by salicylic acid and to identify proteins that bind specifically to phosphorylated 14-3-3 binding motifs on synthesized bait peptides in affinity purification experiments. In conclusion, the combination of stable isotope labeling of plant cells and mass spectrometry is a powerful technology that can be applied to study complex biological processes that involve changes in protein expression such as cellular responses to various kinds of stress or activation of cell signaling. PMID:16088002

Gruhler, Albrecht; Schulze, Waltraud X; Matthiesen, Rune; Mann, Matthias; Jensen, Ole N

2005-08-08

223

Predicting Hydrogen and Oxygen Stable Isotope Ratios of Plants Across Terrestrial Surfaces: Plant IsoScapes  

NASA Astrophysics Data System (ADS)

Human activities at local and regional scales impact the functioning of ecological processes. Integrating these activities requires spatially-explicit models that depend on both accurate input data, as well as a mechanistic understanding of the processes being modeled. Stable isotope ratios of several elements have been used successfully as both recorders of ecological processes, and tracers of the cycling and movement of elements through the biosphere. As such they have the potential to yield useful information across multiple scales. ISOSCAPES is an effort to link ecological and physiological process models with geographic information systems in order to make and test spatially explicit predictions of stable isotope ratios for components of the biosphere. In addition to current ecological processes, we are also applying our understanding of spatial variations in isotope abundances to improve paleoclimatic and modern forensic reconstructions. We present results of our spatial predictions of ?2H and ?18O values for major plant components across the terrestrial surface of the Earth. Predictions for leaf water and cotton-boll cellulose were based on a mechanistic model of leaf water enrichment and biochemical fractionations associated with cellulose formation. The model was driven spatially with globally gridded climate normals obtained from the Climate Research Unit at the University of East Anglia, and globally gridded maps of source water isotope ratios. In addition to leaf water and cellulose, we present spatial predictions for the isotopic ratios of other plant components (e.g., seed lipids). The maps revealed significant latitudinal and continental variation that was consistent with expectations and the relatively limited spatially-explicit available data. Finally, we discuss the implications of these variations and future avenues of spatial-ecology research.

West, J. B.; Bowen, G. J.; Ehleringer, J. R.

2005-12-01

224

Method for cleaning performance evaluation using stable isotopes. Summary report  

SciTech Connect

The Aerospace Guidance and Metrology Center (AGMC) at Newark Air Force Base (NAFB), Ohio, has been using cleaning agents such as 1,1,1-Trichloroethane (TCA) and 1,1,2- Trichloro 1,2,2-trifluoroethane (Freon 113) for repair of inertial guidance equipment. Both of these cleaning agents have been classified as stratospheric ozone layer depleting substance (OLDS). Therefore, AGMC is interested in replacing these with other cleaning agents such as aqueous detergents. In order to assure that reliability and maintainability levels are not degraded when OLDS are phased out, a method is required to validate that the cleaning capability of the suggested alternative is at least as good as that of an existing, proven cleaning agent. The current methods used by AGMC to evaluate cleanliness are not effective when the parts being cleaned are composed of irregular or severe geometrics as is the case for precision gyroscopes and accelerometers repaired at AGMC. Therefore, AGMC funded Battelle to develop and demonstrate a suitable procedure for quantifying cleanliness. This report describes a cleaning performance evaluation procedure (CPEP) based on the use of stable isotopes. The CPEP developed and demonstrated in this project involved two phases. In Phase I, the contaminants which are present in the current cleaning processes were identified to select synthetic inorganic particulate and organic contaminants. In Phase II, unique, stable-isotopes of these contaminants were introduced into the parts followed by cleaning of these parts with various cleaning agents. The amounts of these unique isotopes extracted, as determined by mass spectroscopy (MS) provides a measure of cleaning efficiency.

Chauhan, S.P.; Schumacher, P.; Chuang, J.C.

1992-08-31

225

Developing stable isotopic records from organic material preserved in speleothems  

NASA Astrophysics Data System (ADS)

Speleothems form excellent archives of environmental change as they are easy to date and preserve multiple environmental records. However, although the stable isotopic composition of speleothem calcite is well characterised, the isotopic composition of organic matter in speleothems has not been investigated in-depth. The approach has considerable potential value in providing isotopic records directly linked to the overlying ecosystem. For stable carbon isotopes, this will provide records independent of the calcite signal, and enable identification of the local primary controls (vegetation type, climate, soil conditions). However, the detailed measurement of isotopic records in speleothem organic matter is hindered by methodological constraints, including extraction of sufficient material, and recovery without adding carbon contamination. Here we present results from a number of methodological techniques and discuss which show most potential for future palaeoenvironmental work. Isotopic records in organic matter can be divided into two main types - analyses of the bulk organic fraction, and compound-specific analyses of molecules of interest (e.g. plant waxes, bacterial lipids etc.). From the point of view of sample size, bulk analysis is the most amenable. Our work shows that TOC in stalagmites can be as low as <0.1 mg/g calcite. However, this is still sufficient to produce bulk organic signals at a sample size of between 100 and 500 mg of calcite powder, which provides a workable temporal resolution at a decadal-centennial scale on many samples. The main obstacle is the recovery of bulk organics without carbon contamination, but whilst avoiding excess acid salts which might damage the instrumentation. One method we propose is the use of an iTOC-CDRS analyser, which measures total organic carbon, and also 12C and 13C isotopes. The approach has the advantage of requiring minimal sample preparation, with drilled powders simply being dissolved in acid. The major limitation is the precision on the CDRS, which at +/- 0.15% does not match that of IRMS techniques. However, provided there is good calibration, the small sample size required and the convenient methodology mean that the approach has considerable potential as a screening technique to identify areas of particular interest within a record. Compound specific isotopes will provide greater ecosystem specific detail, but current technology is still severely limited by sample size, as multiple gram samples of calcite are required to produce a sufficient lipid signal. A decadal-centennial resolution can be achieved, but only on particularly organic rich or high growth rate samples. We present a compound specific n-alkane ?13C record from a Scottish stalagmite at a resolution of 100 - 300 years. This produced an analysable signal, but with significant variation in the record between compounds, which may be due to genuine environmental variation such as compound source, or may be analytical variation exacerbated by the small sample size and limited repeats. It is therefore proposed that this approach needs further methodological work on larger samples, and a source-receptor study before being applied to palaeoenvironmental work.

Blyth, A.; Baker, A.

2011-12-01

226

Stable Isotopic Constraints of the Turpan Basin in Northwestern China  

NASA Astrophysics Data System (ADS)

Stable isotopic analysis of sedimentary rocks can be used to reconstruct past geologic changes in the elevation and climate of topographic features such as mountain ranges and plateaus. The Tibetan Plateau is an ideal field laboratory for conducting this type of study because of the Plateaus extreme topographic relief and relatively recent geologic growth. Here we present oxygen and carbon isotope compositions from a suite of sedimentary rock samples taken from the western Turpan Basin in northwestern China. This area of the basin collects sediment from weathering and erosion of the Bogda Shan located to the north. The goal of this study is to analyze changes in the stable isotope composition as a function of stratigraphic position to reconstruct paleoelevations and paleoclimates in this part of the Tibetan Plateau. The sedimentary rock samples analyzed in this study are Late Jurassic to Neogene age and are primarily mudstone, siltstone, fine sandstone along with lesser limestone. Samples were powered and then dissolved with phosphoric acid at 72?C. The liberated CO2 gas was then analyzed using a Finnigan Delta Plus XL mass spectrometer with a gasbench inlet system. Oxygen isotope values range from -13.72 to -1.62 (PDB) and exhibit a large scale trend to more negative values toward the top of the stratigraphic sequence. Superimposed on this large scale trend are systematic variations in isotopic composition as a function of age. The most positive ?18O values occur at approximately 160, 115, 60, and 5 ma. Conversely, ?18O minima are observed at 150, 90, and 40 ma. ?13C values range from -10.69 to 1.40 (PDB). The most positive ?13C values (-4.3 to 1.4) occur from 120-160 ma. Younger samples display small scale variations with age with notable ?13C minima of -10.7, -14.7, and -7.6 at 108, 80, and 17 ma, respectively. The variable ?18O and positive ?13C values from the Jurassic (145-160 ma) are consistent with an arid climate and high atmospheric PCO2 levels during the warm Mesozoic Era. The overall decrease in ?18O values observed during the Cretaceous (145-65 ma) can be explained by the global climatic transition from a warm Mesozoic to a relatively cool Cenozoic Era. We take into account other possible influences on the isotopic record including detrital effects, diagensis, and evaporation, but infer the primary control on the isotopic records to be changes in climate during these time periods. Because the magnitude of oxygen isotope changes is consistent with that expected due to global climate change, we infer that there were not significant changes in the elevation of the Bogda Shan during this time period. This conclusion is also supported by the similar grain size/lithology (siltstone-finer grained sandstones) from bottom to top through the stratigraphic sequence, consistent with dormant topography prior to the Tertiary Period.

Schaen, A. J.

2010-12-01

227

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

228

The quality control of fruit juices by using the stable isotope ratios and trace metal elements concentrations  

NASA Astrophysics Data System (ADS)

In the last years, a growing number of research articles detailing the use of natural abundance light stable isotopes variations and trace metal elements concentration as geographic ``tracers'' to determine the provenance of food have been published. These investigations exploit the systematic global variations of stable hydrogen, oxygen and carbon isotope ratios in (combination) relation with trace metal element concentrations. The trace metal elements content of plants and also their light stable isotopic ratios are mainly related to the geological and pedoclimatic characteristics of the site of growth. The interpretation of such analysis requires an important number of data for authentic natural juices regarding the same seasonal and regional origin, because the isotopic analysis parameters of fruit juices show remarkable variability depending on climatologically factors. In this work was mesured H, C, O stable isotope ratios and the concentrations of 16 elements (P, K, Mg, Na, Ca, Cu, Cr, Ni, Zn, Pb, Co, As, Cd, Mn, Fe and Hg) from 12 single strength juices. The natural variations that appear due to different environmental and climatic conditions are presented and discussed.

Magdas, D. A.; Dehelean, A.; Puscas, R.; Cristea, G.; Tusa, F.; Voica, C.

2012-02-01

229

Sources of organic matter for intertidal consumers on Ascophyllum-shores (SW Iceland): a multi-stable isotope approach  

NASA Astrophysics Data System (ADS)

Stable isotopes were used to examine the origin of organic matter in Icelandic Ascophyllum-based habitats, the role of different organic matters in filling intertidal food webs and the food preferences of the most abundant suspension feeders, grazers and predators. We selected three intertidal sites on the SW coast of Iceland where we sampled in early September 2004, organic matter sources (POM, SOM and most abundant primary producers, A. nodosum and F. vesciculosus) and the most abundant macrofauna species (barnacles, mussels, gastropods, sponge and crabs). Even though the primary production ( Ascophyllum-based) was the same at the three study sites, the isotopic composition of common-among-sites organisms varied due to local differences in the origin of available POM and SOM and in food web structures.

Sar, G.; de Pirro, M.; Romano, C.; Rumolo, P.; Sprovieri, M.; Mazzola, A.

2007-12-01

230

STABLE ISOTOPES IN ECOLOGICAL STUDIES: NEW DEVELOPMENTS IN MIXING MODELS (URUGUAY)  

EPA Science Inventory

Stable isotopes are increasingly being used as tracers in ecological studies. One application uses isotopic ratios to quantify the proportional contributions of multiple sources to a mixture. Examples include pollution sources for air or water bodies, food sources for animals, ...

231

STABLE ISOTOPES IN ECOLOGICAL STUDIES: NEW DEVELOPMENTS IN MIXING MODELS (BRAZIL)  

EPA Science Inventory

Stable isotopes are increasingly being used as tracers in ecological studies. One application uses isotopic ratios to quantify the proportional contributions of multiple sources to a mixture. Examples include pollution sources for air or water bodies, food sources for animals, ...

232

Subcutaneous infusion and capillary "finger stick" sampling of stable isotope tracer in metabolic studies  

Technology Transfer Automated Retrieval System (TEKTRAN)

Metabolic studies utilizing stable isotope tracer in humans have typically used intravenous tracer infusions and venous blood sampling. These studies explore subcutaneous infusion of isotope and "finger stick" capillary blood sampling to measure glucose turnover. Five subjects received simultaneous ...

233

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...

234

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 ...

235

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...

236

Relative isotopic abundances of zirconium in R Cygni and V Cancri  

SciTech Connect

The relative abundances of the isotopes of zirconium, determined from the isotopic splitting of the /sup 1/Pi-/sup 1/..sigma.. (0,1) band head of ZrO, have been found for the two S stars R Cygni and V Cancri to be /sup 90/Zr:/sup 91/Zr:/sup 92/Zr:/sup 93/Zr:/sup 94/Zr:/sup 96/Zr = 0.47:0.10: 0.17:0.06:0.20:0.00. The nonzero abundance of /sup 93/Zr indicates that nucleosynthesis has taken place in these two stars within the recent past. Assuming that all of the above isotopes with the exception of /sup 96/Zr have been synthesized in the s-process, these abundances are consistent with all of the most common scenarios of s-process nucleosynthesis. Subject headings: nucleosynthesis--stars: abundances--stars: individual--stars: S-type

Zook, A.C.

1985-02-01

237

Stable isotopes of carbon and nitrogen in the study of avian and mammalian trophic ecology  

Microsoft Academic Search

Differential fractionation of stable isotopes of carbon during photosynthesis causes C 4 plants and C3 plants to have distinct carbon-isotope signatures. In addition, marine C 3 plants have stable-isotope ratios of carbon that are intermediate between C4 and terrestrial C3 plants. The direct incorporation of the carbon-isotope ratio ( 13C\\/12C) of plants into consumers' tissues makes this ratio useful in

Jeffrey F. Kelly

2000-01-01

238

Interspecific and nutrient-dependent variations in stable isotope fractionation: experimental studies simulating pelagic multitrophic systems  

Microsoft Academic Search

Stable isotope signatures of primary producers display high inter- and intraspecific variation. This is assigned to species-specific\\u000a differences in isotope fractionation and variable abiotic conditions, e.g., temperature, and nutrient and light availability.\\u000a As consumers reflect the isotopic signature of their food source, such variations have direct impacts on the ecological interpretation\\u000a of stable isotope data. To elucidate the variability of

N. Aberle; A. M. Malzahn

2007-01-01

239

Stable nitrogen isotope dynamics of a mesoscale iron enrichment experiment in the NE Subarctic Pacific  

NASA Astrophysics Data System (ADS)

We report the response in the natural abundance of the stable isotopes of nitrogen (?15N) during the Fe-enrichment experiment SERIES (Subarctic Ecosystem Response to Iron Enrichment Study) in the NE Pacific. Samples were collected for isotope analysis of nitrate, particulate material (including size fractionated samples), and particles trapped in the water column from beneath the Fe-enriched patch. In all sample types, ?15N changed in response to increased phytoplankton productivity after the Fe enrichment. The nitrate concentration and ?15N of nitrate were inversely related, the result of the opposing effects of isotope fractionation during nitrate assimilation and the addition of new nitrate by periodic mixing of water from outside the Fe patch. During the growth period a decrease in the difference of the ?15N of particulate nitrogen and nitrate occurred that was attributed to physical mixing, shifts in growth from regenerated nitrogen sources to nitrate, and the change in the community assemblage from<5-?m phytoplankton cells to a larger assemblage dominated by diatoms. The surface-tethered sediment trap ?15N samples indicate that the nitrate isotope fractionation signal in surface waters was not transported below the permanent mixed layer until the end of the phytoplankton growth period, and therefore only the highest values associated with the isotope fractionation process were recorded in the sinking material from the patch. An important conclusion from this study is that mesoscale physical mixing effects and nitrogen remineralization can reduce the expression of isotope fractionation during phytoplankton growth, explaining why the high fractionation values measured in laboratory studies are not commonly observed in the natural environment.

Needoba, Joseph A.; Marchetti, Adrian; Henry, Mike F.; Harrison, Paul J.; Wong, Chi-Shing; Keith Johnson, W.; Pedersen, Tom F.

2006-10-01

240

Stable nitrogen isotope dynamics of a mesoscale iron enrichment experiment in the NE Subarctic Pacific  

NASA Astrophysics Data System (ADS)

We report the response in the natural abundance of the stable isotopes of nitrogen ( ?15N) during the Fe-enrichment experiment SERIES (Subarctic Ecosystem Response to Iron Enrichment Study) in the NE Pacific. Samples were collected for isotope analysis of nitrate, particulate material (including size fractionated samples), and particles trapped in the water column from beneath the Fe-enriched patch. In all sample types, ?15N changed in response to increased phytoplankton productivity after the Fe enrichment. The nitrate concentration and ?15N of nitrate were inversely related, the result of the opposing effects of isotope fractionation during nitrate assimilation and the addition of new nitrate by periodic mixing of water from outside the Fe patch. During the growth period a decrease in the difference of the ?15N of particulate nitrogen and nitrate occurred that was attributed to physical mixing, shifts in growth from regenerated nitrogen sources to nitrate, and the change in the community assemblage from<5-?m phytoplankton cells to a larger assemblage dominated by diatoms. The surface-tethered sediment trap ?15N samples indicate that the nitrate isotope fractionation signal in surface waters was not transported below the permanent mixed layer until the end of the phytoplankton growth period, and therefore only the highest values associated with the isotope fractionation process were recorded in the sinking material from the patch. An important conclusion from this study is that mesoscale physical mixing effects and nitrogen remineralization can reduce the expression of isotope fractionation during phytoplankton growth, explaining why the high fractionation values measured in laboratory studies are not commonly observed in the natural environment.

Needoba, Joseph A.; Marchetti, Adrian; Henry, Mike F.; Harrison, Paul J.; Wong, Chi-Shing; Keith Johnson, W.; Pedersen, Tom F.

2006-10-01

241

Investigation of tubular handling of bicarbonate in man. A new approach utilizing stable carbon isotope fractionation.  

PubMed Central

Two alternative mechanisms have been proposed for tubular reabsorption of bicarbonate: (a) H+ secretion and CO2 reabsorption and (b) direct reabsorption of HCO-3. In an attempt to differentiate between the two mechanisms, the present study utilized the natural abundance of stable carbon isotopes (13C, 12C) in the urinary total CO2. This novel methodology used mass spectrometric analysis of 13C/12C ratios in urinary total CO2 under normal conditions and during acetazolamide treatment. Blood and respiratory CO2 were analyzed to yield reference values. The results demonstrate that alkaline urine is preferentially enriched with 13C relative to the blood. It is suggested that this fractionation results from reaction out of isotopic equilibrium in which HCO-3 converts to CO2 during the reabsorption process in the distal nephron. The presence of carbonic anhydrase in the proximal nephron results in rapid isotopic exchange between CO2 and HCO-3 and keeps them in isotopic equilibrium. The ratio of urinary 13C/12C increases strikingly after acetazolamide administration and consequent inhibition of carbonic anhydrase in the proximal tubule. Although it is possible that in the latter case high HCO-3 generates the CO2 (ampholyte effect), the isotope fractionation indicates that CO2 rather than HCO-3 is reabsorbed. In contrast, at low urinary pH and total CO2 values, the carbon isotope composition approaches that of blood CO2. This indicates rapid CO2 exchange between urine and blood, through luminal membrane highly permeable to CO2. These results could be anticipated by a mathematical model constructed to plot 13C concentration of urinary total CO2. It is concluded that the mechanism of HCO-3 reclamation in man (and, by inference, in other mammals as well) works by conversion of HCO-3 to CO2 and reabsorption of CO2.

Burbea, Z H; Luz, B; Lazar, B; Winaver, J; Better, O S

1983-01-01

242

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

243

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

244

Using Chemical Tracers To Evaluate Feeding Habits in Coastal Marine Ecosystems: Stable Isotopes and Organic Contaminants  

Microsoft Academic Search

The use of chemical tracers to understand ecosystem interactions in the marine environment has gained increasing popularity over the past three decades. Carbon isotope abundances in organic matter sources in the marine system vary significantly making them a useful tracer for discriminating among such sources. Once taken up by primary producers, carbon isotope abundances are conservative throughout the food web.

Rachel Marie Wilson

2010-01-01

245

Stable isotope analysis of carbon and nitrogen in angrites  

NASA Astrophysics Data System (ADS)

Angrites are a small group of ancient basaltic achondrites, notable for their unusual chemistry and extreme volatile depletion. No comprehensive study of indigenous light elements currently exists for the group. Measurement of the abundances and isotopic composition of carbon and nitrogen could provide information pertaining to the evolution of the angrite parent body. Bulk-sample stepped combustion analyses of five angrites and a glass separate from D'Orbigny were combined with earlier data and acid dissolution experiments of carbonates found in D'Orbigny to compile an inventory of indigenous carbon and nitrogen. Indigenous carbon combusted between 700 C and 1200 C, with abundances of 10-140 ppm and a mass-weighted ?13C of -25 to -20 with the exception of D'Orbigny (?13C approximately -5). Nitrogen was released at 850-1200 C, 1-20 ppm with a ?15N -3 to +4; again, D'Orbigny (?15N approximately +20 to +25) was an exception. We interpret these components as largely indigenous and decoupled; the carbon in graphitic or amorphous form, while the nitrogen is present as a dissolved component in the silicates. No relationship with the textural sub-classification of angrites is apparent. We suggest that the angrite parent body contains a reservoir of reduced carbon and thus may have undergone a change in redox conditions, although the timing and mechanism for this remain unclear.

Abernethy, F. A. J.; Verchovsky, A. B.; Starkey, N. A.; Anand, M.; Franchi, I. A.; Grady, Monica M.

2013-09-01

246

Measurement of glucose turnover and oxidation using radioactive and stable isotopes  

SciTech Connect

Isotopes have become the best means for investigating glucose kinetics in vivo. With the recent greater availability of stable isotopes there has developed a need to understand how data may be obtained from the use of both radioactive and stable glucose tracers. Described for the nonexpert is the calculation of glucose appearance and disappearance, clearance and oxidation using both stable and radioactive glucose isotopes, administered both by bolus and primed constant infusion and under both steady and nonsteady state conditions. Other substrates may be studied using similar methodology. The use of stable substrate isotopes will be an expanding field of metabolic research in man.

Royle, G.T.; Wolfe, R.R.; Burke, J.F.

1983-02-01

247

Insights from Stable Isotopes on the Role of Terrestrial Ecosystems in the Global Carbon Cycle  

Microsoft Academic Search

The use of isotopic tracers in organic matter, water, and atmospheric gases has become an important component of the study of ecology and global change. Physiological and physical processes discriminate against heavy isotopes in predictable ways, so that measurements of isotopes at natural abundance, i.e., naturally occurring concentrations as opposed to artificial labeling experiments, can provide useful information about biological

Diane E. Pataki; Chun-Ta Lai; Charles D. Keeling; James R. Ehleringer

248

Stalagmite stable isotope record of recent tropical cyclone events  

NASA Astrophysics Data System (ADS)

We present a 23 yr stalagmite record (1977 2000) of oxygen isotope variation, associated with 11 tropical cyclones (TCs), from Actun Tunichil Muknal cave in central Belize. High-resolution microsampling yielded a record of monthly to weekly temporal resolution that contains abrupt decreases (negative excursions) in calcite ?18O values that correspond with recent TC rain events nearby. A logistic discriminant model reliably identified TC proxy signals using the measurable parameters ?18O and ?13C values, and single point changes in ?18O value. The logistic model correctly identified 80% of excursions as TC events and incorrectly classified only 1 of nearly 1200 nonstorm sampling points. In addition to enabling high-resolution TC frequency reconstruction, this geologic proxy also provides information about the intensity of individual TCs. A multiple regression predicted TC intensity (R2 = 0.465, p = 0.034) using sampling frequency and excursion amplitude. Consistent with previous low-resolution studies, we found that the decadal average ?18O value was lower during the 1990s when several TCs produced rainfall in the area, but higher during the 1980s when only one TC struck. Longer, accurately dated, high-resolution speleothem stable isotope records may be a useful new tool for paleotempestology, to clarify associations between highly variable TC activity and the dynamic range of Quaternary climate.

Benoit Frappier, Amy; Sahagian, Dork; Carpenter, Scott J.; Gonzlez, Luis A.; Frappier, Brian R.

2007-02-01

249

Assessing mineral metabolism in children using stable isotopes.  

PubMed

Mineral metabolism may be altered in children with acute or chronic illnesses. The effects may be short term, such as hypomagnesemia associated with chemotherapy, or long-term, such as loss of bone mineral mass after steroid use. Understanding the causes, consequences, and potential therapies for mineral disorders is enhanced by understanding the absorption, body utilization, and turnover of these minerals. These assessments can now be done safely and readily using non-radioactive, stable isotopes which are available for calcium, zinc, magnesium, and iron. The methods for measurement of mineral absorption and kinetics (turnover) are well established, especially for calcium, and have been tested in every age group. Few studies, however, have been performed in children with acute or chronic illnesses such as cancer. Isotope dosing and infusion protocols are minimally invasive and protocols require small blood or urine volumes. Mineral absorption can be assessed without collecting fecal samples. Kinetics are assessed with blood and urine collections, usually over 5-10 days. Increased use of these techniques may be important in medical and nutritional assessment as well as in the management of pediatric oncology patients. PMID:18064657

Abrams, Steven A

2008-02-01

250

Investigating the contribution of mussel N regeneration to coastal primary production using stable isotope tracers  

NASA Astrophysics Data System (ADS)

Determining the sources, pathways and sinks of inorganic nitrogen is integral to our understanding of one of the main determinants of primary productivity in the marine environment. The current view of rocky shore productivity is that it is largely fuelled by new inorganic nitrogen brought to surface waters by the physical process of upwelling. However, along the rocky shores of the Washington State outer coast, the high densities of mussels (Mytilus californianus) colonizing these shores produce significant quantities of regenerated inorganic nitrogen in the form of ammonium, a preferred nitrogen source for primary production. In this study, we seek to determine to what extent regenerated nitrogen is responsible for fueling primary production in these environments. To this end, we employed stable isotope tracers (15NH4 and 15NO3) to track the pathway of inorganic nitrogen in several rocky shore tidepools over the course of half a tidal cycle. Half of all the pools contained mussels in their natural abundance, while half were mussel control pools in which most of the mussels had been physically removed. Discrete water and algal tissue samples were taken at several time points within the study period for mass spectrometric stable isotope analysis. Preliminary results show isotope dilution of tidepool ammonium in pools containing mussels over half a tidal cycle, due to continued ammonium production by mussels. Combined concentration data, regeneration rates as well as removal rates due to autotrophic uptake and/or microbially-mediated ammonium oxidation (nitrification) will be calculated. Isotopic analysis of algal tissue samples and of the other nitrogen pools will shed further light on the contribution of regenerated ammonium to tidepool biogeochemical cycling and ultimately to coastal primary production.

Pather, S.; Altabet, M. A.; Pfister, C. A.; Post, D. M.

2010-12-01

251

Characterizing the Hydrologic Impacts of Mountaintop Mining Using Stable Isotopes  

NASA Astrophysics Data System (ADS)

Despite mountaintop removal mining (MTM) accounting for the largest land-use change in the Appalachian region of the eastern US, its impact on runoff processes is poorly understood. Several devastating floods have been attributed to MTM activities upstream but there is little quantifiable evidence on how MTM impacts mechanisms of streamflow generation and flooding downstream. MTM involves removing the forest, topsoil, and overlying bedrock to gain access to deeper coal seams. Excess rock is pushed into adjacent valley to create valley fills that completely bury headwater streams that permanently alter ecosystem organization and processes. Isotope hydrology can provide process-based information about the temporal and geographic sources of runoff and rainfall-runoff relationships, but these approaches have not been applied in systems undergoing rapid change and typically not at larger landscape scales. In this study we examine runoff generation using stable isotopes of water from Sycamore Creek (27 km2), an undisturbed forested catchment, and White Oak Creek (11 km2), a MTM-impacted catchment, to quantify for the first time how landscape-scale disturbances impact rainfall-runoff relationship and the processes that govern runoff generation. Both catchments are headwaters of the Clear Fork River watershed (163 km2), an extensively mined and recurrent flood-prone watershed in southern West Virginia, USA. Mountaintop mining in White Oak Creek has disturbed 3 km2 (27% of catchment area) to include 10 valley fills comprising ~0.8 km2 (7%). Stream and rainfall were continuously measured at the outlet of each catchment and water samples were collected using Isco automated water samplers to incrementally characterize isotopic variations in 18O and 2H. Streamflow was separated into event and pre-event water using a two-component hydrograph separation model. The total fraction of event/pre-event water for each event was estimated by linear interpolation between incremental samples of stream and precipitation from the onset of precipitation until stream isotope values returned to pre-event levels. Incremental sampling allows us to estimate the total, peak, and temporal variations of event water contribution during storm events. Our results show that streamflow in White Oak Creek is primarily dominated by event water, whereas pre-event, older water dominates stormflow in the undisturbed Sycamore Creek catchment. We hypothesize that streamflow generation in White Oak Creek is dominated by infiltration-excess overland flow that rapidly delivers event water to the stream, compared to predominantly subsurface flow paths in Sycamore Creek. On-going research using geochemical characterization, end-member mixing analysis, and transit time modeling is aimed at quantifying how MTM impacts the stores, flow paths, and transit times of catchment water.

Zegre, N.; McGuire, K. J.

2011-12-01

252

Harvesting isotopes. Using stable isotope to understand rainfall - runoff processes in an agricultural catchment in Switzerland  

NASA Astrophysics Data System (ADS)

In agricultural catchments, rainfall-runoff processes have big influence on water availability, geomorphology and transport of nutrients and pesticides. A method to gain knowledge of catchments storm flow respond is hydrograph separation using stable isotopes 18O and 2H. This method has been successfully applied in many natural catchments around the world, but the applications in agricultural catchments are limited. This study presents the hydrograph separation in a small scale agricultural catchment (1 km2) near the village of Ossingen in Switzerland. Summer rainfall events were investigated, spatially and temporally, by making use of hydrograph separation using stable isotopes 18O and 2H in rainfall and discharge. For this purpose, the precipitation amount and its isotopic composition was measured. The discharge was observed at the catchment outlet and in four additional sub catchments. During events the runoff was sampled automatically with a frequency of 15 minutes. Here we present the first results of this study, which show that hydrograph separation improves process understanding also in agricultural catchments.

Fischer, Benjamin; Doppler, Tobias; Stamm, Christian; Seibert, Jan

2010-05-01

253

Early pleistocene habitat in member 1 Olorgesailie based on paleosol stable isotopes.  

PubMed

Stable carbon and oxygen isotope values from soil carbonates were used to determine the vegetation context of archaeological sites and local climatic conditions represented in a approximately 0.99 Ma paleosol that is exposed laterally in the Olorgesailie basin, southern Kenya rift valley. As part of this landscape-scale project, samples of an upper Member 1 paleosol were analyzed along nearly 4 km of outcrop in three adjacent parts of the basin. Modern East African soil and plant community analogs are used to interpret the isotope ratios. The carbon isotopic composition of the paleosol carbonates indicates that the area supported a local biomass of about 75-100% C(4)plants during the period of soil formation. After averaging the data for each trench, an open C(4)grassland is represented by half of the carbon values, with wooded grassland more abundant across the paleolandscape than it is in the area now. This vegetational reconstruction is supported by the mammalian faunal assemblage, which has a high percentage of grazers. Although the relatively small sample size outside the main excavation area precludes firm characterization of vegetational diversity across the basin in upper Member 1 times, eastern and western localities in the study area may have had more woody C(3)plants than the widely sampled zone in between. Oxygen isotopes indicate that the lowland basin was slightly cooler and moister than today's semi-arid climate, with greater annual rainfall. Archaeological traces have a virtually continuous distribution across the paleolandscape, but vary in density of occurrence. With the strong evidence for C(4)grassland as the primary vegetation context across most of the study area, no habitat preference by the Acheulean toolmakers at Olorgesailie is shown in our initial comparison between carbon isotope values and stone/bone densities. PMID:10536089

Sikes, N E; Potts, R; Behrensmeyer, A K

1999-11-01

254

Stable Isotope Dilution Multidimensional Liquid Chromatography-Tandem Mass Spectrometry for Pancreatic Cancer Serum Biomarker Discovery  

PubMed Central

A novel approach to pancreatic cancer biomarker discovery has been developed, which employs a stable isotope labeled proteome (SILAP) standard coupled with extensive multidimensional separation coupled with tandem mass spectrometry (MS/MS). Secreted proteins from CAPAN-2 human pancreatic cancer derived cells were collected after conducting stable isotope labeling by amino acids in cell culture (SILAC). The resulting SILAP standard contained <0.5% of individual unlabeled proteins. Pooled sera from patients with early stage pancreatic cancer or controls were prepared, and an equal amount of the SILAP standard was added to each sample. Proteins were separated by isoelectric focusing (IEF) prior to two-dimensional liquid chromatography (2D-LC)MS/MS analysis. A total of 1065 proteins were identified of which 121 proteins were present at 1.5-fold or greater concentrations in the sera of patients with pancreatic cancer. ELISA validation of these findings was successfully performed for two proteins, ICAM-1 and BCAM. Results of these studies have provided proof of principle that a SILAP standard derived from the CAPAN-2 secreted proteome can be used in combination with extensive multidimensional LC-MS/MS for the identification and relative quantitation of potential biomarkers of pancreatic cancer. This technique allows for the detection of low-abundance proteins, and focuses only on biologically relevant proteins derived from pancreatic cancer cells.

2009-01-01

255

Stable Isotope Labeling with Amino Acids in Drosophila for Quantifying Proteins and Modifications  

PubMed Central

SUMMARY Drosophila melanogaster is a common animal model for genetics studies, and quantitative proteomics studies of the fly are emerging. Here we present in detail the development of a procedure to incorporate stable isotope labeled amino acids into the fly proteome. In the method of Stable Isotope Labeling with Amino acids in Drosophila melanogaster (SILAC fly), flies were fed with SILAC labeled yeast grown with modified media, enabling near complete labeling in a single generation. Biological variation in proteome among individual flies was evaluated in a series of null experiments. We further applied the SILAC fly method to profile proteins from a model of fragile X syndrome, the most common cause of inherited mental retardation in human. The analysis identified a number of altered proteins in the disease model, including actin-binding protein profilin and microtubulin-associated protein futsch. The change of both proteins was validated by immunoblotting analysis. Moreover, we extended the SILAC fly strategy to study the dynamics of protein ubiquitination during the fly life span (from day 1 to day 30), by measuring the level of ubiquitin along with two major polyubiquitin chains (K48 and K63 linkages). The results show that the abundance of protein ubiquitination and the two major linkages do not change significantly within the measured age range. Together, the data demonstrate the application of the SILAC principle in Drosophila melanogaster, facilitating the integration of powerful fly genomics with emerging proteomics.

Xu, Ping; Tan, Huiping; Duong, Duc M.; Yang, Yanling; Kupsco, Jeremy; Moberg, Kenneth H.; Li, He; Jin, Peng; Peng, Junmin

2012-01-01

256

Discovery and validation of colonic tumor-associated proteins via metabolic labeling and stable isotopic dilution  

PubMed Central

The unique biology of a neoplasm is reflected by its distinct molecular profile compared with normal tissue. To understand tumor development better, we have undertaken a quantitative proteomic search for abnormally expressed proteins in colonic tumors from ApcMin/+ (Min) mice. By raising pairs of Min and wild-type mice on diets derived from natural-abundance or 15N-labeled algae, we used metabolic labeling to compare protein levels in colonic tumor versus normal tissue. Because metabolic labeling allows internal control throughout sample preparation and analysis, technical error is minimized as compared with in vitro labeling. Several proteins displayed altered expression, and a subset was validated via stable isotopic dilution using synthetic peptide standards. We also compared gene and protein expression among tumor and nontumor tissue, revealing limited correlation. This divergence was especially pronounced for species showing biological change, highlighting the complementary perspectives provided by transcriptomics and proteomics. Our work demonstrates the power of metabolic labeling combined with stable isotopic dilution as an integrated strategy for the identification and validation of differentially expressed proteins using rodent models of human disease.

Huttlin, Edward L.; Chen, Xiaodi; Barrett-Wilt, Gregory A.; Hegeman, Adrian D.; Halberg, Richard B.; Harms, Amy C.; Newton, Michael A.; Dove, William F.; Sussman, Michael R.

2009-01-01

257

Investigating the Formation of Pedogenic Carbonate Using Stable Isotopes  

NASA Astrophysics Data System (ADS)

The stable isotope composition of pedogenic carbonate has been used as a paleoenvironmental proxy because it is thought to form in isotopic equilibrium with soil CO2 and soil water, which are influenced by vegetation type and atmospheric circulation patterns, respectively. However, the isotopic composition of soil CO2 and soil water change seasonally and it is not known what portion of this variability is recorded by the isotopic composition of pedogenic carbonate. It is generally believed that carbonate precipitation in soils is driven by evaporative concentration of Ca ions and/or decreasing soil pCO2. We seek to improve the proxy by determining the seasonality of pedogenic carbonate formation, in particular whether pedogenic carbonate forms during the wet season after individual rainstorms or during seasonal drying following the wet season. This was done by comparing the variations in carbon and oxygen isotope composition of soil CO2 with the isotopic composition of proximally located, newly-formed carbonates. Soil CO2 and incipient pedogenic carbonate coatings were collected in a very young (< 500yrs) soil developing in an inset terrace on the piedmont of the Sandia Mountains, central New Mexico. We also measure soil temperatures at the same site. In May 2006, at the end of the driest 6-month period on record in central New Mexico, soil CO2 profiles displayed a 2 decrease in ?13C values with depth from 9 to 100 cm. In August 2006, the shapes of the profiles were similar, but the ?13C values were 3-4 lower at each depth than in May. These results can be explained by an increase in respiration rate during the latter half of the summer (the wettest on record) when monsoon rainfall maintained high moisture contents in soils across New Mexico. Calculated ?13C values of calcite in equilibrium with May (but not August) soil CO2 agree with measured carbonate ?13C values below 20 cm depth. Very shallow carbonate has anomalously high ?13C values. Measurements of the ?18O values of soil CO2 collected in May span a 16 range with the highest values and steepest gradient just below the surface. In August, the lowest ?18O values measured were just below the surface and there was little change with depth below 35 cm. These results can also be explained by August rainfall which likely lowers the ?18O value of near surface soil water and also near surface soil CO2 via oxygen exchange. Neither the May nor August CO2 values are in equilibrium with the pedogenic carbonate at measured temperatures, but the shape of the ?18O CO2 profiles from May more closely approximate the carbonate ?18O profile. Our results to date suggest that the majority of pedogenic carbonate in this soil forms when the soil is relatively dry. It is possible that the magnitude of soil water evaporation during the period between daily thunderstorms is insufficient to drive carbonate precipitation. Sufficient evaporation may primarily occur during seasonal drying in the autumn. We will test this hypothesis by continuing to sample soil CO2 at this site.

Breecker, D. O.; Sharp, Z. D.; McFadden, L.

2006-12-01

258

Zinc stable isotopes in seafloor hydrothermal vent fluids and chimneys  

Microsoft Academic Search

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

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

2008-01-01

259

Relative isotopic abundances of zirconium in R Cygni and V CANCRI  

Microsoft Academic Search

The relative abundances of the isotopes of Zr in the S stars R Cyg and V Cnc are calculated by determining isotopic splitting at the head of the 1Pi - 1Sigma (0, 1) band of ZrO in spectra obtained at resolution 30 pm on hypersensitized 127-O4 plates with a Varo tube on the 51-cm camera at the Coude focus of

A. C. Zook

1985-01-01

260

Measurement of plutonium and uranium isotopic abundances by gamma-ray spectrometry  

SciTech Connect

The isotopic composition of plutonium and uranium is needed for purposes of sample confirmation, or for interpreting results from calorimeters or neutron-coincidence measurement instruments to determine nuclear material mass. The authors have developed measurement methods and computer codes utilizing high-resolution gamma-ray spectrometry to measure the relative isotopic abundances of plutonium and uranium in various forms nondestructively. The computer codes, known as MGA and MGAU, have unique analysis methodologies that the authors briefly describe in this paper.

Ruhter, W.D. [Lawrence Livermore National Lab., CA (United States); Gunnink, R. [Gunnink (Ray), Fremont, CA (United States)

1996-02-01

261

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...

262

Dietary variation in arctic foxes ( Alopex lagopus )-an analysis of stable carbon isotopes  

Microsoft Academic Search

We used stable carbon isotopes to analyse individual variation in arctic fox diet. We extracted collagen from bones (the lower jaw), and measured stable carbon isotopes. The foxes came from three different localities: Iceland, where both microtines and reindeer are rare; west Greenland, where microtines are absent; and Sweden, where scat analyses showed the primary food to be microtine rodents

Anders Angerbjrn; Pall Hersteinsson; Kerstin Lidn; Erle Nelson

1994-01-01

263

Strangers in a Strange Land: Stable Isotope Evidence for Human Migration in the Dakhleh Oasis, Egypt  

Microsoft Academic Search

This study utilizes a combination of both stable oxygen and nitrogen isotope ratios to determine migration patterns for a large sample of human remains from the Kellis 2 cemetery (c. ad250) in the Dakhleh Oasis, Egypt. Stable oxygen isotopic analysis has been used to identify potential migrants in several different populations. In this study, the data resultant from the combination

Tosha L. Dupras; Henry P. Schwarcz

2001-01-01

264

STABLE ISOTOPE ANALYSIS OF HUMAN REMAINS: A TOOL FOR CAVE ARCHAEOLOGY  

Microsoft Academic Search

Stable isotope analysis of human remains is a research tool that can provide paleodiet infor- mation for archaeological sites, such as caves, where traditional evidence may be missing or out of context. Unlike other lines of evidence, the stable isotopes of carbon and nitrogen in human bone reflect the chemistry of the diet and therefore provide a direct measure of

CARMEN C. TRIMBLE; STEPHEN A. MACKO

265

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

266

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

267

Lipid correction for carbon stable isotope analysis of deep-sea fishes  

Microsoft Academic Search

Stable isotope analysis of fish tissue can aid studies of deep-sea food webs because sampling difficulties severely limit sample sizes of fish for traditional diet studies. The carbon stable isotope ratio (?13C) is widely used in food web studies, but it must be corrected to remove variability associated with varying lipid content in the tissue. A lipid correction has not

Joel C. Hoffman; Tracey T. Sutton

2010-01-01

268

Intercomparison of surface and column measurements of the stable isotope composition of atmospheric water vapour  

Microsoft Academic Search

The stable isotope composition of water vapour is determined by evapotranspiration, condensation and mixing processes in the atmosphere. Continuous monitoring of stable isotopes in water vapour can therefore provide valuable insights into the atmospheric hydrological cycle at any point in time. With the introduction of new optical techniques, it has recently become possible to routinely collect records at the surface

Stephen Parkes; Nicholas Deutscher; Christian Frankenberg; Nicholas Jones; David Griffith; Alastair Williams

2010-01-01

269

Relation of pathways and transit times of recharge water to nitrate concentrations using stable isotopes  

Microsoft Academic Search

Oxygen and hydrogen stable isotope values of precipitation, irrigation water, soil water, and ground water were used with soil-moisture contents and water levels to estimate transit times and pathways of recharge water in the unsaturated zone of a sand and gravel aquifer. Nitrate-nitrogen (nitrate) concentrations in ground water were also measured to assess their relation to seasonal recharge. Stable isotope

Matthew K. Landon; Geoffrey N. Delin; Stephen C. Komor; Charles P. Regan

2000-01-01

270

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. δ13C and δ15N i...

271

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

272

The Role of Naturally Occurring Stable Isotopes in Mass Spectrometry, Part II: The Instrumentation  

PubMed Central

In the second instalment of this tutorial, the authors explain the instrumentation for measuring naturally occurring stable isotopes, specifically the magnetic sector mass spectrometer. This type of instrument remains unrivalled in its performance for isotope ratio mass spectrometry (IRMS) and the reader is reminded of its operation and its technical advantages for isotope measurements.

Bluck, Les; Volmer, Dietrich A.

2013-01-01

273

Precise determination of stable chlorine isotopic ratios in low-concentration natural samples  

Microsoft Academic Search

Investigation of stable chlorine isotopes in geological materials has been hindered by large sample requirements and\\/or lack of analytical precision. Here we describe precise methods for the extraction, isolation, and isotopic analysis of low levels of chlorine in both silicate and aerosol samples. Our standard procedure uses 2 g of Cl for each isotopic analysis. External reproducibility (1 ) is

A. J. Magenheim; A. J. Spivack; C. Volpe; B. Ransom

1994-01-01

274

Stable isotope tracing of trout hatchery carbon to sediments and foodwebs of limestone spring creeks.  

PubMed

Limestone springs support productive ecosystems and fisheries, yet aquaculture may modify or impair these ecosystems. We determined trout hatchery organic contribution to spring creek sediments and foodwebs with natural abundance stable isotope methods. Hatchery feed, waste, and trout were significantly enriched in delta(13)C relative to autotrophs and wild fish. Spring creek sediments were enriched in delta(13)C toward the hatchery endmember relative to reference streams without hatcheries and relative to a larger larger-order, spring-influenced stream. Contribution of hatchery C to spring creek sediments was greatest during March and associated with greatest sediment %C. Contribution of hatchery C to pollution-tolerant isopod diet was 39-51% in a stream receiving limestone spring water via hatchery effluent. Isopods of one spring creek also relied on hatchery-derived C within one month of hatchery closure. Four years later, less pollution pollution-tolerant amphipods dominated and consumed non-vascular over vascular autotrophs (86%). Isopods of a second spring creek with an active hatchery did not appear to be using hatchery matter directly, but were enriched in delta(34)S relative to a spring creek tributary with no hatchery influence. Isopods in both of these streams were relatively enriched in delta(15)N, indicating general nutrient enrichment from surrounding agricultural land use. The contribution of hatchery vs. wild fish in diet of herons and egrets was traced with delta(13)C of guano. These birds were strongly dependent on stocked trout in a spring creek with a recently closed state trout hatchery, and also near another large, state-run hatchery. Heron dependence on hatchery fish in the spring creek decreased with time since hatchery closure. Use of stable isotope natural abundance techniques in karst spring creeks can reveal stream impairment due to aquaculture, specific C sources to bio-indicating consumers, losses of farmed fish to predation, and potential exposure of higher order consumers to contaminants associated with aquaculture. PMID:18674799

Hurd, Todd M; Jesic, Slaven; Jerin, Jessica L; Fuller, Nathan W; Miller, David

2008-07-31

275

[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

276

Prospects and problems of using the methods of geochemistry of stable carbon isotopes in soil studies  

Microsoft Academic Search

A review of world investigations into the geochemistry of stable isotopesa new area for soil scienceis presented. Studies\\u000a of the behavior of stable isotopes in soils are being developed in two major directions: reconstruction of the environmental\\u000a conditions and indication of the soil processes. Investigations into the reconstruction of the environmental conditions are\\u000a based on the assumption that the isotopic

E. G. Morgun; I. V. Kovda; Ya. G. Ryskov; S. A. Oleinik

2008-01-01

277

Applications of stable isotopes to study plant-animal relationships in terrestrial ecosystems  

Microsoft Academic Search

As natural tracers, stable isotopes have been extensively used in plant physiological, ecological and environmental research.\\u000a Recently, animal physiological ecologists have also applied stable isotope techniques to study plantanimal relationships.\\u000a The isotopic compositions of animal body generally reflect and integrate their diets over a time period ranging from hours\\u000a to years to the lifetime of an individual. When animal living

Jianzhu Wang; Guanghui Lin; Jianhui Huang; Xingguo Han

2004-01-01

278

Controlling for anthropogenically induced atmospheric variation in stable carbon isotope studies  

Microsoft Academic Search

Increased use of stable isotope analysis to examine food-web dynamics, migration, transfer of nutrients, and behavior will likely result in expansion of stable isotope studies investigating human-induced global changes. Recent elevation of atmospheric CO2 concentration, related primarily to fossil fuel combustion, has reduced atmospheric CO2 ?13C (13C\\/12C), and this change in isotopic baseline has, in turn, reduced plant and animal

Eric S. Long; Richard A. Sweitzer; Duane R. Diefenbach; Merav Ben-David

2005-01-01

279

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

SciTech Connect

The Oak Ridge National Laboratory (ORNL) has been supplying enriched stable and radioactive isotopes to the research, medical, and industrial communities for over 50 years. 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 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; SIO 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 capabilities 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.

Aaron, W.S.; Tracy, J.G.; Collins, E.D.

1996-10-01

280

2H stable isotope analysis of human tooth enamel: a new tool for forensic human provenancing?  

PubMed

Stable isotope analysis of biogenic tissues such as tooth enamel and bone mineral has become a well-recognised and increasingly important method for determining the provenance of human remains, and it has been used successfully in bio-archaeological studies as well as forensic investigations. In particular, (18)O and (2)H stable isotope signatures of bone and hair, respectively, are well-established proxies of climate (temperature) and source water and are therefore considered as indicators of geographic life trajectories of animals and humans. While the methodology for (2)H analysis of human hair, fingernails, and bone collagen is currently used to determine human provenance, i.e. geographic origin and identify possible migration patterns, studies involving the analysis of (2)H in tooth enamel appear to be nonexistent in the scientific literature. Ground tooth enamel was analysed by continuous-flow isotope ratio mass spectrometry (IRMS) coupled on-line to a high-temperature conversion elemental analyser (TC/EA). An array of tooth enamel samples from archaeological and modern teeth has been analysed under different experimental conditions, and the results of this proof-of-concept study are presented. While no significant differences in (2)H abundance were noted as a result of H exchange studies or different sample preparation protocols, no significant differences or trends in measured ?(2)H-values were observed either with regard to known differences in geographical provenance. We concluded that the ?(2)H-values obtained from tooth enamel could not be used as proxy for a person's geographical origin during adolescence. PMID:21416527

Holobinko, A; Meier-Augenstein, W; Kemp, H F; Prowse, T; Ford, S M

2011-03-14

281

Using stable isotopes to assess carbon and nitrogen turnover in the Arctic sympagic amphipod Onisimus litoralis  

Microsoft Academic Search

Food web studies based on stable C and N isotope ratios usually assume isotopic equilibrium between a consumer and its diet.\\u000a In the Arctic, strong seasonality in food availability often leads to diet switching, resulting in a consumers isotopic composition\\u000a to be in flux between different food sources. Experimental work investigating the time course and dynamics of isotopic change\\u000a in

Mette R. Kaufman; Rolf R. Gradinger; Bodil A. Bluhm; Diane M. OBrien

2008-01-01

282

NMR-based stable isotope resolved metabolomics in systems biochemistry  

PubMed Central

An important goal of metabolomics is to characterize the changes in metabolic networks in cells or various tissues of an organism in response to external perturbations or pathologies. The profiling of metabolites and their steady state concentrations does not directly provide information regarding the architecture and fluxes through metabolic networks. This requires tracer approaches. NMR is especially powerful as it can be used not only to identify and quantify metabolites in an unfractionated mixture such as biofluids or crude cell/tissue extracts, but also determine the positional isotopomer distributions of metabolites derived from a precursor enriched in stable isotopes such as 13C and 15N via metabolic transformations. In this article we demonstrate the application of a variety of 2-D NMR editing experiments to define the positional isotopomers of compounds present in polar and non-polar extracts of human lung cancer cells grown in either [U13C]-glucose or [U13C,15N]-glutamine as source tracers. The information provided by such experiments enabled unambiguous reconstruction of metabolic pathways, which is the foundation for further metabolic flux modeling.

Fan, Teresa W-M.

2011-01-01

283

Stable isotope-based diet reconstructions of Turkana Basin hominins.  

PubMed

Hominin fossil evidence in the Turkana Basin in Kenya from ca. 4.1 to 1.4 Ma samples two archaic early hominin genera and records some of the early evolutionary history of Paranthropus and Homo. Stable carbon isotopes in fossil tooth enamel are used to estimate the fraction of diet derived from C3 or C4 resources in these hominin taxa. The earliest hominin species in the Turkana Basin, Australopithecus anamensis, derived nearly all of its diet from C3 resources. Subsequently, by ca. 3.3 Ma, the later Kenyanthropus platyops had a very wide dietary range--from virtually a purely C3 resource-based diet to one dominated by C4 resources. By ca. 2 Ma, hominins in the Turkana Basin had split into two distinct groups: specimens attributable to the genus Homo provide evidence for a diet with a ca. 65/35 ratio of C3- to C4-based resources, whereas P. boisei had a higher fraction of C4-based diet (ca. 25/75 ratio). Homo sp. increased the fraction of C4-based resources in the diet through ca. 1.5 Ma, whereas P. boisei maintained its high dependency on C4-derived resources. PMID:23733966

Cerling, Thure E; Manthi, Fredrick Kyalo; Mbua, Emma N; Leakey, Louise N; Leakey, Meave G; Leakey, Richard E; Brown, Francis H; Grine, Frederick E; Hart, John A; Kaleme, Prince; Roche, Hlne; Uno, Kevin T; Wood, Bernard A

2013-06-03

284

Evaluation of stable isotope tracing for ZnO nanomaterials--new constraints from high precision isotope analyses and modeling.  

PubMed

This contribution evaluates two possible routes of stable isotope tracing for ZnO nanomaterials. For this we carried out the first high precision Zn isotope analyses of commercially available ZnO nanomaterials, to investigate whether such materials exhibit isotope fractionations that can be exploited for tracing purposes. These measurements revealed Zn isotopic compositions (of ?(66/64)Zn = +0.28 to -0.31 relative to JMC Lyon Zn) that are indistinguishable from "normal" natural and anthropogenic Zn in environmental samples. Stable isotope tracing therefore requires the application of purpose-made isotopically enriched ZnO nanoparticles. A detailed evaluation identified the most suitable and cost-effective labeling isotopes for different analytical requirements and techniques. It is shown that, using relatively inexpensive (68)Zn for labeling, ZnO nanoparticles can be reliably detected in natural samples with a Zn background of 100 ?g/g at concentrations as low as about 5 ng/g, if the isotopic tracing analyses are carried out by high precision mass spectrometry. Stable isotope tracing may also be able to differentiate between the uptake by organisms of particulate ZnO and Zn(2+) ions from the dissolution of nanoparticles. PMID:22394426

Larner, Fiona; Rehkmper, Mark

2012-03-19

285

Studies of Isotopic Abundances through Gamma-Ray Lines  

SciTech Connect

Cosmic gamma-ray lines convey isotopic information from sites of nucleosynthesis and from their surrounding interstellar medium. With recent space-borne gamma-ray spectrometers of high resolution (INTEGRAL, RHESSI), new results have been obtained for 44Ti from the Cas A core-collapse supernova, from long-lived radioactive 26Al and 60Fe, and from positron annihilation in our Galaxy: 44Ti ejection from Cas A may be on the low side of previously-reported values, and/or at velocities >7000 km s-1. 26Al sources apparently share the Galactic rotation in the inner Galaxy, and thus allow to estimate a total mass of 26Al in the Galaxy of 2.8 M{center_dot} from the measured flux. The 60Fe production in massive stars appears lower than predicted by standard models, as constrained by the recent, though marginal, 60Fe detections. Positron annihilation in the Galaxy shows a remarkable bulge component, which is difficult to understand in terms of nucleosynthetic production of the positrons.

Diehl, Roland [Max Planck Institut fuer extraterrestrische Physik, D-85748 Garching (Germany)

2006-07-12

286

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

287

Estimation of nitrogen stable isotope turnover rate of Oncorhynchus nerka  

Microsoft Academic Search

Estimation of the isotopic turnover rate in the tissues of organisms allows us to estimate the temporal relationship between the isotope ratio of an organism and its prey, and to analyze seasonal variations of food webs and migratory patterns of animals. We analyzed the isotopic turnover rate in the tissue of lacustrine sockeye salmon, Oncorhynchus nerka, of three age classes

Hiroyuki Sakano; Eiji Fujiwara; Seiichi Nohara; Hiroshi Ueda

2005-01-01

288

The link between assimilation and below-ground processes - stable isotopes as tools to assess carbon transfer  

NASA Astrophysics Data System (ADS)

At present, there is lack of 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 ecosystem-scale processes. On the background of global climate change, we need to mechanistically link plant physiology, CO2 net exchange between ecosystems and the atmosphere and plant biomass accumulation. This is the basis for predicting productivity of forests as well as their carbon sequestration potential in future. This paper will give an overview on how stable isotope studies can give insights into the fate of newly assimilated carbon transported within trees and transferred to the soil and atmosphere. The paper includes assessments characterizing temporal and spatial variation in the natural abundance of carbon and oxygen isotopes or applying isotopically enriched tracers. In addition, it highlights the fact that the stable isotope composition of assimilates transported within the plant contains important time integrated information on environmental conditions, leaf physiology, and post-photosynthetic metabolism. The paper on the one hand focuses on the fast turn over carbon pools, which fuel plant respiration and soil microbial activity and on the other hand explores the transfer of the isotope information to long-lived compounds in plant archives such as tree rings.

Gessler, A.; Wingate, L.; Oge, J.; Offermann, C.; Kodama, N.

2011-12-01

289

Investigating microbial carbon cycling using natural abundance isotope analysis of PLFA  

Microsoft Academic Search

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

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

2008-01-01

290

Abundances of light isotopes in galactic cosmic rays and the interstellar gas density  

Microsoft Academic Search

The fluxes of the light isotopes in the galactic cosmic rays are calculated in the energy range from 10 MeV to 5 GeV. The mean amount of matter traversed is taken to increase with decreasing energy, and various forms of the source spectrum are assumed. It is shown that it is possible to reconcile all observed abundance ratios including the

N. J. Westergaard

1979-01-01

291

Stable oxygen and hydrogen isotopes of brines - comparing isotope ratio mass spectrometry and isotope ratio infrared spectroscopy  

NASA Astrophysics Data System (ADS)

Today's standard analytical methods for high precision stable isotope analysis of fluids are gas-water equilibration and high temperature pyrolysis coupled to isotope ratio mass spectrometers (IRMS). In recent years, relatively new laser-based analytical instruments entered the market that are said to allow high isotope precision data on nearly every media. This optical technique is referred to as isotope ratio infrared spectroscopy (IRIS). The objective of this study is to evaluate the capability of this new instrument type for highly saline solutions and a comparison of the analytical results with traditional IRMS analysis. It has been shown for the equilibration method that the presence of salts influences the measured isotope values depending on the salt concentration (see Lcuyer et al, 2009; Martineau, 2012). This so-called 'isotope salt effect' depends on the salt type and salt concentration. These factors change the activity in the fluid and therefore shift the isotope ratios measured by the equilibration method. Consequently, correction factors have to be applied to these analytical data. Direct conversion techniques like pyrolysis or the new laser instruments allow the measurement of the water molecule from the sample directly and should therefore not suffer from the salt effect, i.e. no corrections of raw values are necessary. However, due to high salt concentrations this might cause technical problems with the analytical hardware and may require labor-intensive sample preparation (e.g. vacuum distillation). This study evaluates the salt isotope effect for the IRMS equilibration technique (Thermo Gasbench II coupled to Delta Plus XP) and the laser-based IRIS instruments with liquid injection (Picarro L2120-i). Synthetic salt solutions (NaCl, KCl, CaCl2, MgCl2, MgSO4, CaSO4) and natural brines collected from the Stassfurt Salt Anticline (Germany; Stadler et al., 2012) were analysed with both techniques. Salt concentrations ranged from seawater salinity up to full saturation. References Lcuyer, C. et al. (2009). Chem. Geol., 264, 122-126. [doi:10.1016/j.chemgeo.2009.02.017] Martineau, F. et al. (2012). Chem. Geol., 291, 236-240. [doi:10.1016/j.chemgeo.2011.10.017] Stadler, S. et al. (2012). Chem. Geol., 294-295, 226-242. [doi:10.1016/j.chemgeo.2011.12.006

Ahrens, Christian; Koeniger, Paul; van Geldern, Robert; Stadler, Susanne

2013-04-01

292

The Isotopic Constitution of Lanthanum and Cerium  

Microsoft Academic Search

The isotopic abundances of lanthanum and cerium have been determined by means of a mass spectrometer. In addition to the known lanthanum isotope of mass 139, a new isotope of mass 138 and abundance 0.089 percent has been discovered. Since this isotope is isobaric with two neighboring stable isotopes it should be radioactive. No activity was observed. Upper limits for

Mark G. Inghram; Richard J. Hayden; David C. Hess

1947-01-01

293

Relative isotopic abundances of zirconium in R Cygni and V CANCRI  

NASA Astrophysics Data System (ADS)

The relative abundances of the isotopes of Zr in the S stars R Cyg and V Cnc are calculated by determining isotopic splitting at the head of the 1Pi - 1Sigma (0, 1) band of ZrO in spectra obtained at resolution 30 pm on hypersensitized 127-O4 plates with a Varo tube on the 51-cm camera at the Coude focus of the 3-m telescope at Lick Observatory. The data reduction techniques and the fit to the model synthetic spectra of Kurucz (1970) are described, and the ratio (Zr-90):(Zr-91):(Zr-92):(Zr-93):(Zr-94):(Zr-96) is given as 47:10:17:6:20:00 percent. The presence of the long-lived unstable isotope Zr-93 is interpreted as evidence for recent nucleosynthesis, and the abundances found are shown to be consistent with s-process nucleosynthesis.

Zook, A. C.

1985-02-01

294

Stable isotope methods: The effect of gut contents on isotopic ratios of zooplankton  

NASA Astrophysics Data System (ADS)

In the past decade there has been an increased awareness of the potential for methodological bias resulting from multiple pre-analytical procedures in foodweb interpretations based on stable isotope techniques. In the case of small organisms, this includes the effect of gut contents on whole body signatures. Although gut contents may not reflect actual assimilation, their carbon and nitrogen values will be isotopically lighter than after the same material has been assimilated. The potential skewing of isotopic ratios in whole organism samples is especially important for aquatic environments as many studies involve trophic relationships among small zooplankton. This is particularly important in pelagic waters, where herbivorous zooplankton comprise small taxa. Hence this study investigated the effect of gut contents on the ?13C and ?15N ratios of three size classes of zooplankton (1.0-2.0, 2.0-4.0 and >4.0 mm) collected using bongo net tows in the tropical waters of the south-west Indian Ocean. Animals were collected at night, when they were likely to be feeding, sieved into size classes and separated into genera. We focused on Euphausia spp which dominated zooplankton biomass. Three treatment types were processed: bulk animals, bulk animals without guts and tail muscle from each size class at 10 bongo stations. The ?15N ratios were influenced by zooplankton size class, presumably reflecting ontogenetic changes in diet. ANOVA post hoc results and correlations in ?15N signatures among treatments suggest that gut contents may not affect overall nitrogen signatures of Euphausia spp., but that ?13C signatures may be significantly altered by their presence. Carbon interpretations however, were complicated by potential effects of variation in chitin, lipids and metabolism among tissues and the possibility of opportunistic omnivory. Consequently we advocate gut evacuation before sacrifice in euphausiids if specific tissue dissection is impractical and recommend caution when using isotopic ratios of whole body zooplankton for trophic interpretations.

Hill, J. M.; McQuaid, C. D.

2011-05-01

295

Considerations in the Development of the Utility of Stable Isotopes in Science, Medicine, and Agriculture, and Environmental Studies.  

National Technical Information Service (NTIS)

The prospects for the broad scale development of the utility of stable isotopes in science, medicine, agriculture, and environmental studies are considered with emphasis on the current status of isotope production, synthesis of isotopically labelled compo...

N. A. Matwiyoff

1976-01-01

296

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

297

Isotopes and atomic absorption spectrometry. Computer simulations, Part I: Evaluation of the simulation model using the flame atomic absorption determination of lithium isotope abundances  

Microsoft Academic Search

An evaluation of a computer model developed to calculate absorbances involving multi-isotopic elements is presented. With the use of the model, an independently peformed flame aotmic absorption experiment to determine isotope abundances of lithium is simulated. The necessity of having accurate values of the critical model parameters (damping constant, isotope shift, fine structure separation, and collisional shift) is demonstrated. The

K. A. S. Pathiratne; R. J. Lovett

1987-01-01

298

Stable carbon isotope depth profiles and soil organic carbon dynamics in the lower Mississippi Basin  

USGS Publications Warehouse

Analysis of depth trends of 13C abundance in soil organic matter and of 13C abundance from soil-respired CO2 provides useful indications of the dynamics of the terrestrial carbon cycle and of paleoecological change. We measured depth trends of 13C abundance from cropland and control pairs of soils in the lower Mississippi Basin, as well as the 13C abundance of soil-respired CO2 produced during approximately 1-year soil incubation, to determine the role of several candidate processes on the 13C depth profile of soil organic matter. Depth profiles of 13C from uncultivated control soils show a strong relationship between the natural logarithm of soil organic carbon concentration and its isotopic composition, consistent with a model Rayleigh distillation of 13C in decomposing soil due to kinetic fractionation during decomposition. Laboratory incubations showed that initially respired CO 2 had a relatively constant 13C content, despite large differences in the 13C content of bulk soil organic matter. Initially respired CO2 was consistently 13C-depleted with respect to bulk soil and became increasingly 13C-depleted during 1-year, consistent with the hypothesis of accumulation of 13C in the products of microbial decomposition, but showing increasing decomposition of 13C-depleted stable organic components during decomposition without input of fresh biomass. We use the difference between 13C / 12C ratios (calculated as ??-values) between respired CO 2 and bulk soil organic carbon as an index of the degree of decomposition of soil, showing trends which are consistent with trends of 14C activity, and with results of a two-pooled kinetic decomposition rate model describing CO2 production data recorded during 1 year of incubation. We also observed inconsistencies with the Rayleigh distillation model in paired cropland soils and reasons for these inconsistencies are discussed. ?? 2005 Elsevier B.V. All rights reserved.

Wynn, J. G.; Harden, J. W.; Fries, T. L.

2006-01-01

299

Stable isotope ratios of rain and vapor in 1995 hurricanes  

NASA Astrophysics Data System (ADS)

Isotope ratios of rain and vapor samples collected at the surface from four tropical cyclones during the active 1995 Atlantic hurricane season were determined. A two-dimensional bulk microphysics isotope model was applied to steady symmetric tropical cyclones to explain the observed low mean values and inward decrease of isotope ratios of the rain and vapor. The low mean value is caused by the tropical cyclone's relatively large size, longevity, and deep clouds. The inward decrease is due to diffusive isotope exchange between falling rain and converging vapor in the atmospheric boundary layer. Dean, a minimal tropical storm, produced relatively high isotope ratios because of its small size and youth. Rains from the extreme outer edge of Felix, a category 3 hurricane, exhibited high isotope ratios similar to normal summer rain. Isotope ratios of rains and vapors from Hurricane Luis in Puerto Rico decreased as the storm approached. Isotope ratios of rain exhibited an abrupt jump from low values in the eastern half of Puerto Rico to high values farther west which is linked to the storm's rainbands. Isotope ratios of Hurricane Opal's rains reflected the storm's asymmetric structure, with lowest values west of the point of landfall. Record low isotope ratios from a squall line that struck eastern Texas two days before landfall are linked to low-level outflow from Opal and demonstrate that hurricanes can vent enormous quantities of vapor to the surroundings.

Lawrence, James Robert; Gedzelman, Stanley David; Zhang, Xiaoping; Arnold, Robert

1998-05-01

300

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

301

Stable isotopic studies of earthworm feeding ecology in tropical ecosystems of Puerto Rico.  

PubMed

Feeding strategies of earthworms and their influence on soil processes are often inferred from morphological, behavioral and physiological traits. We used (13)C and (15)N natural abundance in earthworms, soils and plants to explore patterns of resource utilization by different species of earthworms in three tropical ecosystems in Puerto Rico. In a high altitude dwarf forest, native earthworms Trigaster longissimus and Estherella sp. showed less (15)N enrichment ((15)N = 3-6 per thousand) than exotic Pontoscolex corethrurus ((15)N =7-9 per thousand) indicating different food sources or stronger isotopic discrimination by the latter. Conversely, in a lower altitude tabonuco forest, Estherella sp. and P. corethrurus overlapped completely in (15)N enrichment ((15)N = 6-9 per thousand), suggesting the potential for interspecific competition for N resources. A tabonuco forest converted to pasture contained only P. corethrurus which were less enriched in (15)N than those in the forest sites, but more highly enriched in (13)C suggesting assimilation of C from the predominant C(4) grass. These results support the utility of stable isotopes to delineate resource partitioning and potential competitive interactions among earthworm species. Copyright 1999 John Wiley & Sons, Ltd. PMID:10407313

Hendrix; Lachnicht; Callaham; Zou

1999-07-01

302

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

303

Available versus digestible amino acids - new stable isotope methods.  

PubMed

The nutritive value of food protein sources is dependent on the amino acid composition and the bioavailability of the nutritionally indispensable amino acids. Traditionally the methods developed to determine amino acid bioavailability have focused on intestinal absorption or digestibility, which is calculated as the percent of amino acid intake that does not appear in digesta or faeces. Traditional digestibility based methods do not always account for gut endogenous amino acid losses or absorbed amino acids which are unavailable due to the effect of heat processing and the presence of anti-nutritional factors, though methods have been developed to address these issues. Furthermore, digestibility based methods require the use of animal models, thus there is a need to develop in vivo methods that can be applied directly in human subjects to identify the proportion of dietary amino acids which is bioavailable, or metabolically available to the body for protein synthesis following digestion and absorption. The indicator amino acid oxidation (IAAO) method developed in our laboratory for humans has been systematically applied to determine almost all indispensable amino acid requirements in adult humans. Oxidation of the indicator amino acid is inversely proportional to whole body protein synthesis and responds rapidly to changes in the bioavailability of amino acids for metabolic processes. Using the IAAO concept, we developed a new in vivo method in growing pigs, pregnant sows and adult humans to identify the metabolic availability of amino acids in foods. The stable isotope based metabolic availability method is suitable for rapid and routine analysis in humans, and can be used to integrate amino acid requirement data with dietary amino acid availability of foods. PMID:23107543

Elango, Rajavel; Levesque, Crystal; Ball, Ronald O; Pencharz, Paul B

2012-08-01

304

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

305

Tracking Nursery Habitat Use in the York River Estuary, Virginia, by Young American Shad Using Stable Isotopes  

Microsoft Academic Search

We developed and applied a stable isotope turnover model to estimate how long age-0 American shad Alosa sapidissima reside within tidal freshwater and brackish-water habitats in the York River estuary, Virginia. The residence time was estimated by modeling the changing stable isotope ratio (either the carbon [?C] or sulfur [?S] stable isotope ratio) of an age-0 American shad as it

J. C. Hoffman; D. A. Bronk; J. E. Olney

2007-01-01

306

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

2013-07-22

307

Palaeoclimate signal recorded by stable isotopes in cave ice: a modeling approach  

NASA Astrophysics Data System (ADS)

Ice accumulations in caves preserve a large variety of geochemical information as candidate proxies for both past climate and environmental changes, one of the most significant being the stable isotopic composition of the ice. A series of recent studies have targeted oxygen and hydrogen stable isotopes in cave ice as proxies for past air temperatures, but the results are far from being as straightforward as they are in high latitude and altitude glaciers and ice caps. The main problems emerging from these studies are related to the mechanisms of cave ice formation (i.e., freezing of water) and post-formation processes (melting and refreezing), which both alter the original isotopic signal in water. Different methods have been put forward to solve these issues and a fair understanding of the present-day link between stable isotopes in precipitation and cave ice exists now. However, the main issues still lays unsolved: 1) is it possible to extend this link to older ice and thus reconstruct past changes in air temperature?; 2) to what extent are ice dynamics processes modifying the original climatic signal and 3) what is the best method to be used in extracting a climatic signal from stable isotopes in cave ice? To respond to these questions, we have conducted a modeling experiment, in which a theoretical cave ice stable isotope record was constructed using present-day observations on stable isotope behavior in cave ice and ice dynamics, and different methods (presently used for both polar and cave glaciers), were used to reconstruct the original, known, isotopic values. Our results show that it is possible to remove the effects of ice melting and refreezing on stable isotope composition of cave ice, and thus reconstruct the original isotopic signal, and further the climatic one.

Per?oiu, A.; Bojar, A.-V.

2012-04-01

308

Uptake of Dissolved Sulfide by Spartina alterniflora: Evidence from Natural Sulfur Isotope Abundance Ratios  

Microsoft Academic Search

The difference in the stable sulfur isotope ratios of sulfate and sulfide in marsh pore water was used to verify the uptake of hydrogen sulfide by the salt marsh cordgrass Spartina alterniflora in a North Carolina salt marsh. Most of the plant sulfur derived from pore-water sulfide was recovered as sulfate, an indication that the sulfide had been oxidized within

Paul R. Carlson; Joseph Forrest

1982-01-01

309

Stable Isotopes in Ecological Sceinces: Bird and Fish Diet and Migration in Virginia  

NASA Astrophysics Data System (ADS)

The preservation of ecologically sensitive habitats for birds and fishes in Virginia requires a detailed understanding of the important changes in diet and migration over the life span of the animal. Stable isotope analysis offers the potential to assess migration and trophic level variability in birds and fishes from southeastern Virginia and the greater Chesapeake Bay. Fish of various species and ages from different locations throughout the Chesapeake Bay were analyzed for carbon-13 and nitrogen-15 bulk natural abundance. Of particular note, blue fish were found to have significantly higher d15N values than striped bass which are believed to be trophic competitors. Observations are discussed relative to the maturity of the different fish, variation in water-mass chemistry (N-inputs), local environmental habitats, trophic relationships and migratory habits. In conjunction with banding studies being conducted by Virginia Department of Game and Inland Fisheries in the Great Dismal Swamp (VA), breast feathers from Carolina Wren, Common Yellowthroat, Northern Cardinal, Ovenbird, and Prothonotary Warbler were analyzed for carbon-13 and nitrogen-15 bulk natural abundance. Given the preliminary nature of this work our ability to identify trends between species was less than satisfying, thus highlighting the need for larger sample populations over more than one breeding season. However, within a given species (most notably the Prothonotary Warbler) we are able to discern a change in diet. The hatching year Prothonotary warbler were more enriched in both carbon-13 and nitrogen-15 than the after-hatching-year (AHY) birds, indicating a change in food sources between the two age groups. By sampling over time and at various sample sites, isotopic analyses allow a more detailed investigation of the spatial and temporal variation in the diets and migratory habits of fishes and birds in Virginia and the Chesapeake Bay.

Schmidt, S.; Dias, R. F.; Ake, R.; Jones, C. M.

2002-12-01

310

Effects of formalin preservation on stable carbon and nitrogen isotope signatures in Calanoid copepods: implications for the use of Continuous Plankton Recorder Survey samples in stable isotope analyses.  

PubMed

Preserved and archived organic material offers huge potential for the conduct of retrospective and long-term historical ecosystem reconstructions using stable isotope analyses, but because of isotopic exchange with preservatives the obtained values require validation. The Continuous Plankton Recorder (CPR) Survey is the most extensive long-term monitoring program for plankton communities worldwide and has utilised ships of opportunity to collect samples since 1931. To keep the samples intact for subsequent analysis, they are collected and preserved in formalin; however, previous studies have found that this may alter stable carbon and nitrogen isotope ratios in zooplankton. A maximum ~0.9 increase of ?(15) N and a time dependent maximum ~1.0 decrease of ?(13) C were observed when the copepod, Calanus helgolandicus, was experimentally exposed to two formalin preservatives for 12 months. Applying specific correction factors to ?(15) N and ?(13) C values for similarly preserved Calanoid species collected by the CPR Survey within 12 months of analysis may be appropriate to enable their use in stable isotope studies. The isotope values of samples stored frozen did not differ significantly from those of controls. Although the impact of formalin preservation was relatively small in this and other studies of marine zooplankton, changes in isotope signatures are not consistent across taxa, especially for ?(15) N, indicating that species-specific studies may be required. PMID:21638354

Bicknell, Anthony W J; Campbell, Maria; Knight, Mairi E; Bilton, David T; Newton, Jason; Votier, Stephen C

2011-07-15

311

Partitioning Ecosystem Respiration Using Stable Carbon Isotopes in a Mixed C3 Annual Grassland  

NASA Astrophysics Data System (ADS)

The stable carbon isotope ratio (? 13C) of respired CO2 has been used to partition soil respiration into root and microbial components by exploiting the different ? 13C signals from C3 plants growing in a previously C4 dominated system (Rouchette, Angers and Flanagan 1999). We extend this approach and present data that attempts to partition ecosystem respiration using ? 13C analyses of all of the ecosystem compartments in a mixed C3 annual grassland that has not experienced recent C4 inputs. From December 2000 to February 2001 we measured ? 13C-CO2 respired from leaves, roots and sieved soil collected from a winter-active grassland near Ione, California. Two-source mixing models were used to calculate the contribution of each source to total system respiration by comparing their isotope signals to those from whole ecosystem respiration and soil surface efflux. Isotope ratios were measured on 10mL air samples in septum-capped vials using a Finnigan MAT Delta PlusXL IRMS/Gas Bench II interfaced to an autosampler (after Tu et al. 2001). The vials were filled with sample air in the field using a double-holed needle connected in a closed loop to a LI-6200 IRGA and a bottle containing the isolated samples (leaf, root, sieved soil, etc.). Leaves were clipped at ground level and roots and soil were separated by sieving soil cores. Sample ? 13CO2 signatures were determined by plotting the change in ? 13C against the inverse of CO2 concentration. On average, CO2 respired from sieved soil (-27.4o/oo+/-1.4) was slightly more depleted than that from leaves (-27.2o/oo+/-0.5), but much more depleted than the whole ecosystem (-24.9o/oo+/-0.6), the soil surface efflux (-23.8o/oo+/-0.9), and plant roots (-20.5o/oo+/-0.8). Based on these isotope values, leaf respiration comprised 33% of ecosystem respiration with 36% from roots and 31% from soil microbial respiration. Thus, over two-thirds of ecosystem respiration was autotrophic (plant-based) in origin with roughly one-third being heterotrophic. Belowground respiration, comprised of both autotrophic (root) and heterotrophic (microbial) components, accounted for nearly two-thirds of total ecosystem respiration. Root and microbial respiration each contributed to nearly half of total belowground respiration (53% and 47%, respectively). Similarly, plant respiration was divided nearly equally between that from roots (52%) and leaves (48%). Partitioning using natural abundance stable carbon isotope ratios was made possible because of the relatively large differences in ? 13C values among the various sources in this entirely C3 system. To our knowledge, such large isotopic differences in respired CO2 among different plant tissues and belowground components have not been documented before. Further research is needed to determine how such differences may arise and to establish if similar differences exist in other ecosystems or at different times of the growing season. Our results also imply that interpretation of above-canopy Keeling plot intercepts may be complicated by both multiple (and isotopically distinct) sources and by isotopic fractionation that occurs either during the respiration process itself or during the transfer of carbon compounds prior to respiration.

Tu, K. P.

2001-12-01

312

Isotopic Abundances of Eu, Ba, and Sm in Metal-Poor Stars  

NASA Astrophysics Data System (ADS)

We have examined the isotopic mix of the heavy neutron (n)-capture elements Eu, Ba, and Sm in three metal-poor stars with different enrichment histories. Isotopic abundances are more fundamental than elemental abundances as probes of the contributions from the rapid (r) and slow (s) nucleosynthesis reactions. We use our isotopic abundances in conjunction with elemental abundances of many heavy n-capture elements to constrain the nucleosynthetic history of these metal-poor stars. HD 122563 is a very metal-poor giant that has a clear underabundance of n-capture elements ([Fe/H]=-2.7, [Eu/Fe]=-0.5, [Ba/Fe]=-1.0). HD 175305 is a metal-poor giant that is enriched in r-process material ([Fe/H]=-1.5, [Eu/Fe]=+0.5). HD 196944 is a very metal-poor giant star that is enriched in s-process material ([Fe/H]=-2.3, [Ba/Fe]=+1.1). We have acquired new high-resolution (R 130,000) and high-S/N (S/N 160-1000) observations of these three stars with the 2.7m Harlan J. Smith Telescope at McDonald Observatory using the 2dcoude spectrograph. We present our measurements of the isotopic abundances of Eu, Ba, and Sm in these three stars. This research has been supported by U.S. National Science Foundation grants AST 03-07495 and AST 06-07708.

Roederer, Ian U.; Sneden, C.; Lawler, J. E.; Sobeck, J. S.; Pilachowski, C. A.; Cowan, J. J.

2006-12-01

313

The changing trophic status of shallow Minnesota lakes: evidence from stable isotopic and biological proxies  

NASA Astrophysics Data System (ADS)

Shallow lakes can exist in two alternative stable regimes: a clear-water regime dominated by macrophytes with little phytoplankton abundance, or a turbid-water regime where conditions are the opposite. There is a need for more historical studies of shallow lakes as these systems constitute a critical habitat for waterfowl across a large region of the upper Midwestern U.S. and Canada and evidence suggests that the clear regime is preferable for healthy communities of the waterfowl and desired fish populations. Recent work also suggests that the clear regime favors the enhanced burial of organic carbon and thus might constitute an important natural sink for greenhouse gases. Here, we report on our study of C and N elemental and stable isotopic values of organic matter and biological proxies from the sediment core records of numerous shallow lakes in west-central MN and in other areas of the state. These records span the last few centuries including the time of settlement of the region and they have been age dated using 210Pb and ambrosia pollen counts. Results of our work suggest that in the past 50-60 years the majority of the lakes have shifted towards a generally more turbid, eutrophic, and algal-dominated condition that is less favorable to both carbon burial and desired animal habitat.

Theissen, K. M.; Zimmer, K.; Cotner, J. B.; Sugita, S.; Hobbs, W.; Ramstack, J. M.

2010-12-01

314

Stable Isotopes of Platinum: A New Tracer for Terrestrial Planet Accretion and Evolution?  

NASA Astrophysics Data System (ADS)

We present methods for the separation of platinum from geological materials and measurement of stable isotopes of platinum by MC-ICPMS. These are applied to a range of meteorites and terrestrial samples to investigate Earth's differentiation.

Creech, J. B.; Handler, M. R.; Baker, J. A.; Schiller, M.; Bizzarro, M.

2012-09-01

315

SEASONAL VARIATIONS OF STABLE HYDROGEN AND CARBON ISOTOPE RATIOS OF METHANE IN SUBTROPICAL FRESHWATER SEDIMENTS  

EPA Science Inventory

Stable hydrogen (D) and carbon (13C) isotope ratios of sedimentary methane from five subtropical Florida freshwater sites exhibited smaller, less distinct seasonal variations than previously observed in temperate sediments, apparently due to the smaller range of temperatures forc...

316

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

317

INCORPORATING CONCENTRATION DEPENDENCE IN STABLE ISOTOPE MIXING MODELS: A REPLY TO ROBBINS, HILDERBRAND AND FARLEY (2002)  

EPA Science Inventory

Phillips & Koch (2002) outlined a new stable isotope mixing model which incorporates differences in elemental concentrations in the determinations of source proportions in a mixture. They illustrated their method with sensitivity analyses and two examples from the wildlife ecolog...

318

USING CONTINUOUS STABLE ISOTOPE MEASUREMENTS TO PARTITION NET ECOSYSTEM CO2 EXCHANGE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Field-scale estimation of ecosystem photosynthesis and respiration using micrometeorological techniques remains an important yet difficult challenge. In this study, we combined micrometeorological and stable isotope methods to partition net ecosystem CO2 exchange (NEE) into photosynthesis and respir...

319

Quantitative determination of oxidative base damage in DNA by stable isotope-dilution mass spectrometry.  

PubMed

For understanding of the role of oxidative DNA damage in biological processes such as mutagenesis and carcinogenesis, it is essential to identify and quantify this type of DNA damage in cells. This can be achieved by gas chromatography/mass spectrometry. The present study describes the quantification of modified bases in DNA by isotope-dilution mass spectrometry with the use of stable isotope-labeled analogues as internal standards. A number of isotopically labeled DNA bases were synthesized. The mass spectra of their trimethylsilyl derivatives were recorded. Calibration plots were obtained for known quantities of modified bases and their isotope-labeled analogues. Quantification of various modified DNA bases by isotope-dilution mass spectrometry was demonstrated in isolated chromatin exposed to ionizing radiation. The results indicate that gas chromatography/stable isotope-dilution mass spectrometry is an ideally suited technique for selective and sensitive quantification of modified bases in DNA. PMID:8416801

Dizdaroglu, M

1993-01-01

320

Isotopic and elemental abundances of neon nuclei accelerated in solar flares  

Microsoft Academic Search

The relative isotopic abundances of ²°Ne and ²²Ne in seven solar flares were determined from measurements on the satellite IMP 8, yielding the ratio ²°Ne\\/²²Ne=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 +- 0.01 also has been

W. F. Dietrich; J. A. Simpson

1979-01-01

321

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

322

Late Quaternary Precipitation Seasonality of SW North America Reconstructed from Stable Isotopes in Fossil Packrat Pellets  

NASA Astrophysics Data System (ADS)

Stable isotopic values of Carbon 13, Nitrogen 15, Oxygen 18, and Deuterium were measured from modern and fossil packrat pellets from throughout the southwestern United States using a gas isotope ratio mass spectrometer. Late Twentieth Century climate observations were extrapolated to the locations of 41 modern pellet reference samples ranging across Arizona, Utah, Nevada, and California, U.S.A. The reference samples demonstrated correlations between the amount and percent of annual precipitation falling in the winter to early spring (December through April) for ?15N, and percent monsoon precipitation (July through September) for ?D. Isotope values were not well correlated with temperature variables. Isotopes of Carbon and Oxygen were poorly correlated with the climate variables investigated, although previous studies have indicated that ?13C often reflects the abundance of CAM species within the middens as packrats usually feed upon either succulent CAM or C3 conifer species. The modern isotopic values were next compared to series of fossil values from the Grand Canyon, AZ, Glen Canyon, UT, Wupatki National Monument, AZ, and Picacho Peak, CA. Fifty to 100 fossil pellets were ground to dust and homogenized to create a sample from each midden deposit. This sample should represent an average from local plants consumed by the packrat over at least several years. The two most complete series of ?D values, from upper and lower elevations within the Grand Canyon, suggested extremely low monsoon percentages from 23.5 to 18.0 ka (full-glacial Wisconsinan), but higher than current values from 13.7 to 13.0 ka (Allerd Period) and from 11.7 to 7.6 ka (early Holocene). The increased monsoon amounts during the Allerd and early Holocene reinforce earlier conclusions based upon plant fossils from these midden series. Fossil series of ?15N values showed fewer clear trends through time. Our results suggest that ?D values from fossil packrat pellets can serve as a valuable complement to plant fossils in reconstructing past precipitation seasonality in the monsoonal deserts of southwestern North America.

Cole, K. L.; Ironside, K.; Cole, E. A.; Fisher, J.

2011-12-01

323

RNA Stable Isotope Probing, a Novel Means of Linking Microbial Community Function to Phylogeny  

Microsoft Academic Search

accountable for it. In this study stable-isotope-labeled (13C)phenol was fed into a phenol-degrading community from an aerobic industrial bioreactor, and the 13C-labeled RNA produced was used to identify the bacteria responsible for the process. Stable-isotope-labeled RNA was analyzed by equilibrium density centrifugation in concert with reverse transcription-PCR and denaturing gradient gel electrophoresis. In contradiction with findings from conventional methodologies, this

Mike Manefield; Andrew S. Whiteley; Robert I. Griffiths; Mark J. Bailey

2002-01-01

324

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

325

Stable Isotope Fractionation Caused by Glycyl Radical Enzymes during Bacterial Degradation of Aromatic Compounds  

Microsoft Academic Search

Stable isotope fractionation was studied during the degradation of m-xylene, o-xylene, m-cresol, and p-cresol with two pure cultures of sulfate-reducing bacteria. Degradation of all four compounds is initiated by a fumarate addition reaction by a glycyl radical enzyme, analogous to the well-studied benzylsuccinate synthase reaction in toluene degradation. The extent of stable carbon isotope fractionation caused by these radical-type reactions

Barbara Morasch; Hans H. Richnow; Andrea Vieth; Bernhard Schink; Rainer U. Meckenstock

2004-01-01

326

Stable oxygen and carbon isotope characteristics in speleothems from Southern Africa - how good are they?  

NASA Astrophysics Data System (ADS)

Much remains to be understood about the interaction between the African climate system, its surrounding ocean-atmosphere climate variability and the global climate system. A better understanding of the regional climate evolution is crucial for understanding global climate dynamics and issues surrounding environmental change throughout Africa and a prerequisite for increasing climate forecasting capabilities for the region. As part of developing this understanding, a longer term perspective that reaches beyond the information available from instrumental records is required. Speleothems are frequently abundant in southern Africa. Quite a few records are now available, reporting significant changes in climate and environmental conditions over longer and shorter time scales. Conclusions are mainly based on the stable isotopic composition of the speleothems. The interpretation of the stable isotope data is, however, not always straight-forward, since many processes contribute to the observed signal in the speleothem and these processes may influence the signal differently at different spatial and temporal scales. For example was the Makapansgat speleothem oxygen isotope record, originally interpreted as being generally determined by shifts in atmospheric circulation pattern (Lee-Thorp et al. 2001, Holmgren et al. 2003), recently challenged and re-interpreted by Partin et al. (2008) to reflect annual rainfall amounts. Historically, less attention has been paid to the stable carbon isotope composition in speleothems. Today, an increasing number of studies demonstrate the potential of stable carbon variations as providing additional information on climate and environment. Measured variations can be a function of the amount of C3 versus C4 vegetation, vegetation cover and soil biological activity, bedrock proportion, rainfall amount and the drip rate. Clearly the multitudes of plausible processes behind the isotopic composition of speleothems in southern Africa (as well as elsewhere) are a challenge to firm conclusions. However, the need for more globally well dispersed terrestrial palaeoclimatic records; the strong advantages of speleothems to provide precise ages and the empirical experience of successful solutions in previous speleothem research, encourage us to continue research on speleothems from southern Africa. If the understanding of the forcing mechanisms behind measured variables in speleothems can be increased, then there is a great potential for retrieving good climate records from the sub-continent, since the availability of caves containing speleothems is fairly frequent. Available speleothem research from southern Africa will be summarised and potentials and constraints will be discussed. References: Holmgren, K., Lee-Thorp, J.A., Cooper, G.J., Lundblad, K., Partridge, T.C., Scott, L., Sithaldeen, R., Talma, A.S. and Tyson, P.D. 2003: Persistent Millennial-Scale Climatic Variability over the Past 25 thousand Years in Southern Africa. Quaternary Science Reviews, 22, 2311-2326. Lee-Thorp, J.A., Holmgren, K., S.E. Lauritzen, Linge, H., Moberg, A., Partridge, T.C., Stevenson, C. and Tyson P., 2001: Rapid climate shifts in the southern African interior throughout the mid to late Holocene. Geophysical Research Letters 28, 4507-4510. Partin, J.W., Cobb, K.M. and Banner, J.L. 2008: Climate variability recorded in tropical and sub-tropical speleothems. PAGES news, 16, 3, p. 9-10.

Holmgren, K.

2009-04-01

327

Food web analysis of southern California coastal wetlands using multiple stable isotopes  

Microsoft Academic Search

Carbon, nitrogen, and sulfur stable isotopes were used to characterize the food webs (i.e., sources of carbon and trophic\\u000a status of consumers) in Tijuana Estuary and San Dieguito Lagoon. Producer groups were most clearly differentiated by carbon,\\u000a then by sulfur, and least clearly by nitrogen isotope measurements. Consumer 15N isotopic enrichment suggested that there are four trophic levels in the

Thomas J. Kwak; Joy B. Zedler

1997-01-01

328

Tunable diode laser absorption spectroscopy for stable isotope studies of ecosystematmosphere CO 2 exchange  

Microsoft Academic Search

The stable isotope content of atmospheric CO2 provides information about ecosystem carbonwater relations and biosphereatmosphere carbon exchange. Virtually every isotope study within these fields has required air sample collection at remote locations followed by isotope analysis at a laboratory. This requirement severely limits sampling frequency and experiment duration. In this paper, we evaluate a tunable diode laser absorption spectrometer (TDL)

David R. Bowling; Steve D. Sargent; Bert D. Tanner; James R. Ehleringer

2003-01-01

329

An introduction to stable water isotopes in climate models: benefits of forward proxy modelling for paleoclimatology  

Microsoft Academic Search

Stable water isotopes have been measured in a wide range of climate archives, with the purpose of reconstructing regional climate variations. Yet the common assumption that the isotopic signal is a direct indicator of temperature proves to be misleading under certain circumstances, since its relationship with temperature also depends on e.g. atmospheric circulation and precipitation seasonality. Here we introduce the

C. Sturm; Q. Zhang; D. Noone

2010-01-01

330

Stable carbon isotope fractionation between substrates and products of Methanosarcina barkeri  

Microsoft Academic Search

Stable carbon isotope ratios are an important tool for understanding methanogenesis in the environment. When applied to biological methanogenesis, interpretation of carbon isotope ratios requires a thorough understanding of how the availability of different substrates affects the eventual ?13C of methane, biomass and lipids. Methanosarcina barkeri was grown on four substrates: methanol, trimethylamine (TMA), acetate, and H2\\/CO2, under variable conditions

Kathleen L. Londry; Kathleen G. Dawson; Heather D. Grover; Roger E. Summons; Alexander S. Bradley

2008-01-01

331

Oxygen and carbon stable isotopes in otoliths record spatial isolation of Patagonian toothfish ( Dissostichus eleginoides)  

Microsoft Academic Search

Strong contrasts in ambient isotope ratios and in diet suggest stable isotopes in the otoliths of oceanic fish can resolve water masses and geographic areas, promising a powerful multivariate approach for examining population structure and provenance. To test this, whole otoliths were taken from Patagonian toothfish (Dissostichus eleginoides) sampled off the Patagonian Shelf and South Georgia, on either side of

Julian Ashford; Cynthia Jones

2007-01-01

332

Stable isotope analysis of termite food habits in East African grasslands  

Microsoft Academic Search

Stable carbon isotope techniques were employed to study the food habits of the termite Macrotermes michaelseni (Isoptera: Termitidae) in a semiarid savanna habitat in Kenya. At Kajiado this species utilized approximately 70% herbaceous vegetation (mostly grass) and 30% woody vegetation, while at Ruiru approximately 64% of the vegetation utilized was woody and 36% herbaceous. Stabel carbon isotope ratios varied between

T. W. Boutton; M. A. Arshad; L. L. Tieszen

1983-01-01

333

Stable Isotope Biogeochemistry of Seabird Guano Fertilization: Results from Growth Chamber Studies with Maize (Zea Mays)  

Microsoft Academic Search

BackgroundStable isotope analysis is being utilized with increasing regularity to examine a wide range of issues (diet, habitat use, migration) in ecology, geology, archaeology, and related disciplines. A crucial component to these studies is a thorough understanding of the range and causes of baseline isotopic variation, which is relatively poorly understood for nitrogen (?15N). Animal excrement is known to impact

Paul Szpak; Fred J. Longstaffe; Jean-Franois Millaire; Christine D. White

2012-01-01

334

In vivo Research with Stable Isotopes in Biochemistry, Nutrition and Clinical Medicine: An Overview  

Microsoft Academic Search

Tracers and kinetic modelling provide the opportunity to follow the movement and to quantify the metabolic fates of biological compounds in vivo. For studies in children and for repeated studies in adults, the use of stable isotopically labelled substrates are preferable and safe. Measurement of isotopic enrichment in biological molecules is highly specific and can be extremely precise. This allows

K. de Meer; M. J. Roef; W. Kulik; C. Jakobs

1999-01-01

335

Bioaccumulation of newly deposited mercury by fish and invertebrates: an enclosure study using stable mercury isotopes  

Microsoft Academic Search

Enriched stable mercury (Hg) isotopes were added to four 10 m diameter enclosures in Lake 239 at the Experimental Lakes Area to increase inorganic Hg loading. Our main objectives were to (i) follow low-level additions (spikes) of isotope-enriched Hg through the biogeochemical cycle and into the food web and (ii) determine the relative contribution of newly deposited Hg to methyl

Michael J. Paterson; Paul J. Blanchfield; Cheryl Podemski; Holger H. Hintelmann; Cynthia C. Gilmour; Reed Harris; Nives Ogrinc; John W. M. Rudd; Ken A. Sandilands

2006-01-01

336

Use of enriched stable isotopes to determine zinc and iron absorption in elderly men13  

Microsoft Academic Search

The absorption of zinc and iron was determined in seven elderly men using the enriched stable isotopes 7Zn and rFe. Analyses of isotopic ratios were done using thermal ionization magnetic sector mass spectrometny on chloride solutions of zinc and of iron after separation of zinc from fecal samples by ion exchange and of iron by solvent extraction. Mean apparent zinc

Judith R. Turniund; M. C. Michel; William R. Keyes; Janet C. King; Sheldon Margen

337

ENRICHED STABLE ISOTOPE TARGET PREPARATION AT THE OAK RIDGE NATIONAL LABORATORY  

SciTech Connect

Since the 1960s the Department of Energy (DOE) Isotope Program, through the Isotope Development Group at the Oak Ridge National Laboratory, has been developing and supplying, among other things, enriched stable isotope targets for nuclear research around the world. This group also maintains and distributes the DOE inventory of enriched stable isotopes. Chemical and pyrochemical techniques are used to prepare enriched stable isotopes from this inventory in the desired chemical form. Metallurgical, ceramic, or vacuum processing methods are then used to prepare the isotopes in a wide range of physical forms from thin films, foils, and coatings to large fabricated shapes to meet the needs of experimenters. Significant characterization capabilities are also available to assist in the preparation and evaluation of these custom materials. This work is part of the DOE Isotope Program, which recently transferred to the Office of Nuclear Physics, DOE Office of Science, resulting in a stronger emphasis on enabling R&D. This presentation will focus on the custom preparation of enriched stable isotope targets and other research materials.

Aaron, W Scott [ORNL; Zevenbergen, Lee [ORNL

2013-01-01

338

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...

339

Contribution to chlorine cycle: a Cl stable isotope approach on Mantle-Ocean exchanges  

Microsoft Academic Search

The stable isotope composition of chlorine (37Cl\\/35Cl) can be used to trace its geochemical cycle and is a powerfull tool to constrain the origin of high chlorine contents found for some fresh MORB glasses. Despite the fact that chlorine is a volatile element of primary importance, its cycle and isotopic fractionation factors during exchange processes between Earth's reservoirs or phases

M. Bonifacie; N. Jendrzejewski; F. Pineau; P. Agrinier

2003-01-01

340

A Simple Single Serum Method to Measure Fractional Calcium Absorption using Dual Stable Isotopes  

Microsoft Academic Search

The dual stable isotope method with a timed 24- h urine collection is the gold standard approach to measure fractional calcium absorption. How- ever, the need to collect urine for 24 h makes this technique time-consuming and laborious. Our study sought to determine whether a dual isotope method using a single serum sample obtained 4 h after administration of the

L. Ceglia; S. A. Abrams; S. S. Harris; H. M. Rasmussen; G. E. Dallal; B. Dawson-Hughes

2009-01-01

341

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

Microsoft Academic Search

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

Xiangyu. Jiang; David L. Smith

1987-01-01

342

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

343

Historical Variations in Zinc Stable Isotope Composition of Smelter Polluted Sediments  

Microsoft Academic Search

The stable isotopic composition of zinc was measured by multi-collector ICPMS in two organic sediment cores obtained downwind from the former pyrometallurgical zinc smelter in Lommel, Belgium. Previous down core heavy metal concentration trends indicated a close resemblance between Belgian Zn production and reconstructed atmospheric Zn deposition rates. Radiogenic lead isotopes agree with sphalerite (ZnS) ore imports from Australia and

J. E. Sonke; Y. Sivry; L. Dejonghe; L. Andre; R. Freydier; J. Viers; B. Dupre

2006-01-01

344

Stable isotope models to predict geographic origin and cultivation conditions of marijuana  

Microsoft Academic Search

Here we describe stable isotope based models using hydrogen and carbon isotope ratios to predict geographic region-of-origin and growth environment for marijuana, with the intent of applying these models to analyses of marijuana trafficking in the USA. The models were developed on the basis of eradication specimens and border specimens seized throughout the USA. We tested reliability of the geographic

Janet M. Hurley; Jason B. West; James R. Ehleringer

2010-01-01

345

Highly enriched multiply-labeled stable isotopic compounds as atmospheric tracers  

DOEpatents

Compounds multiply-labeled with stable isotopes and highly enriched in these isotopes are readily capable of detection in tracer experiments involving high dilutions. Thus, for example, /sup 13/C/sup 18/O/sub 2/ provides a useful tracer for following atmospheric pol lution produced as a result of fossil fuel burning. (Official Gazette)

Goldblatt, M.; McInteer, B.B.

1974-01-29

346

Paleodietary implications from stable carbon isotope analysis of experimental cooking residues  

Microsoft Academic Search

The regional timing of maize introduction in eastern North America is a long-standing topic of archaeological interest. Most recently, Morton and Schwarcz [2004. Paleodietary implications from stable isotopic analysis of residues on prehistoric Ontario ceramics. Journal of Archaeological Science 31, 503517] investigated the timing of maize introduction in Ontario through isotope analysis of charred cooking residues adhering to the interior

John P. Hart; William A. Lovis; Janet K. Schulenberg; Gerald R. Urquhart

2007-01-01

347

Endogenous Surfactant Turnover in Preterm Infants with Respiratory Distress Syndrome Studied with Stable Isotope Lipids  

Microsoft Academic Search

We studied surfactant kinetics on Day 1 of life in 11 preterm in- fants on mechanical ventilation by infusing stable isotope labeled palmitic (PA) and linoleic acid (LLA). Six infants received exoge- nous surfactant for the treatment of respiratory distress syndrome (RDS) and five did not meet treatment criteria because of minimal or no disease. The isotopic enrichment of plasma

PAOLA CAVICCHIOLI; LUC J. I. ZIMMERMANN; PAOLA E. COGO; TAMARA BADON; GIUSEPPE GIORDANO; MIRKA TORRESIN; FRANCO ZACCHELLO; VIRGILIO P. CARNIELLI

2001-01-01

348

Stable isotope separation in calutrons: Forty years of production and distribution  

SciTech Connect

The stable isotope separation program, established in 1945, has operated continually to provide enriched stable isotopes and selected radioactive isotopes, including the actinides, for use in research, medicine, and industrial applications. This report summarizes the first forty years of effort in the production and distribution of stable isotopes. Evolution of the program along with the research and development, chemical processing, and production efforts are highlighted. A total of 3.86 million separator hours has been utilized to separate 235 isotopes of 56 elements. Relative effort expended toward processing each of these elements is shown. Collection rates (mg/separator h), which vary by a factor of 20,000 from the highest to the lowest (/sup 205/Tl to /sup 46/Ca), and the attainable isotopic purity for each isotope are presented. Policies related to isotope pricing, isotope distribution, and support for the enrichment program are discussed. Changes in government funding, coupled with large variations in sales revenue, have resulted in 7-fold perturbations in production levels.

Bell, W.A.; Tracy, J.G.

1987-11-01

349

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.

350

Multiple Group Analysis (MGA): A gamma-ray spectrum analysis code for determining plutonium isotopic abundances  

SciTech Connect

MGA calculates relative isotopic abundances of plutonium and other actinides in a sample. The code performs its analysis using data from a gamma-ray spectrum of the sample taken with a germanium detector. This volume describes the structure of the program and the procedures used for measuring samples and analyzing the spectra. It is assumed that the user is familiar with standard practices and equipment used in gamma-ray spectrometry.

Gunnink, R.; Ruhter, W.D.

1990-09-01

351

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

352

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

353

Improve accuracy and sensibility in glycan structure prediction by matching glycan isotope abundance.  

PubMed

Mass Spectrometry (MS) is a powerful technique for the determination of glycan structures and is capable of providing qualitative and quantitative information. Recent development in computational method offers an opportunity to use glycan structure databases and de novo algorithms for extracting valuable information from MS or MS/MS data. However, detecting low-intensity peaks that are buried in noisy data sets is still a challenge and an algorithm for accurate prediction and annotation of glycan structures from MS data is highly desirable. The present study describes a novel algorithm for glycan structure prediction by matching glycan isotope abundance (mGIA), which takes isotope masses, abundances, and spacing into account. We constructed a comprehensive database containing 808 glycan compositions and their corresponding isotope abundance. Unlike most previously reported methods, not only did we take into count the m/z values of the peaks but also their corresponding logarithmic Euclidean distance of the calculated and detected isotope vectors. Evaluation against a linear classifier, obtained by training mGIA algorithm with datasets of three different human tissue samples from Consortium for Functional Glycomics (CFG) in association with Support Vector Machine (SVM), was proposed to improve the accuracy of automatic glycan structure annotation. In addition, an effective data preprocessing procedure, including baseline subtraction, smoothing, peak centroiding and composition matching for extracting correct isotope profiles from MS data was incorporated. The algorithm was validated by analyzing the mouse kidney MS data from CFG, resulting in the identification of 6 more glycan compositions than the previous annotation and significant improvement of detection of weaker peaks compared with the algorithm previously reported. PMID:22882827

Xu, Guang; Liu, Xin; Liu, Qing Yan; Zhou, Yanhong; Li, Jianjun

2012-07-16

354

Enhanced Carbon Enrichment in Parasitoids (Hymenoptera): A Stable Isotope Study  

Microsoft Academic Search

By considering the magnitude of isotope enrichment associated with trophic transfers in biologically important elements such as carbon (13C\\/12C) and nitrogen (15N\\/14N), it is possible to infer trophic interactions in systems where direct observations are logistically difcult. Several recent reviews have estimated that consumers become enriched in the heavy nitrogen isotope on the order of 2.3 to 3.4 with each

Gail A. Langellotto; Jay A. Rosenheim; Megan R. Williams

2005-01-01

355

Estimating the Origin of Water Using Stable Isotopes over Indochina  

Microsoft Academic Search

The daily precipitation and isotopic compositions from August to November in 2001 were observed at ChiangMai, Bangkok, and Phuket in Thailand. The ? 18 O variability was well reproduced by the Rayleigh-type Isotope Circulation Model (ICM), which correlation coefficients between observed and simulated values were 0.54, 0.70, and 0.70 for ChiangMai, Bangkok, and Phuket, respectively. The origin of water was

KIMPEI ICHIYANAGI; KEI YOSHIMURA; MANABU D. YAMANAKA

356

Regression analysis for comparing protein samples with 16O\\/18O stable-isotope labeled mass spectrometry  

Microsoft Academic Search

Motivation: Using stable isotopes in global proteome scans, labeled molecules from one sample are pooled with unlabeled molecules from anothersampleandsubsequentlysubjectedtomass-spectralanalysis. Stable-isotope methodologies make use of the fact that identical molecules of different stable-isotope compositions are differentiated in a mass spectrometer and are represented in a mass spectrum as distinct isotopic clusters with a known mass shift. We describe two multivariable

J. E. Ecker-passow; Ann L. Oberg; Terry M. Therneau; C. J. Mason; Douglas W. Mahoney; K. L. Johnson; J. E. Olson; H. R. Bergen III

2006-01-01

357

Stable Isotope Ratiometer-Multiple Ion Detector (Sirmid) Unit for Quantitative and Qualitative Stable Isotope Studies by Gas Chromatography-Mass Spectrometry.  

National Technical Information Service (NTIS)

A stable isotope ratiometer-multiple ion detector (SIRMID) unit which can drive existing gas chromatograph-quadrupole or magnetic sector mass spectrometers to monitor up to six ions in turn is described. Each of the three pairs of ions can be selected for...

P. D. Klein J. R. Haumann D. L. Hachey

1975-01-01

358

Origin and fate of organic compounds in water: characterization by compound-specific stable isotope analysis.  

PubMed

Within the past 15 years, compound-specific stable isotope analysis has continued to increase in popularity in the area of contaminant hydrology of organic molecules. In particular, in cases where concentration data alone are insufficient to elucidate environmental processes unequivocally, the isotope signature can provide additional unique information. Specifically, it can help answer questions about contaminant source apportionment, quantification of biotic and abiotic processes, and identification of transformation reactions on a mechanistic level. We review advances in laboratory and field investigations and exemplary applications in contaminant hydrology via stable isotope analysis. We also highlight future directions in the field. PMID:22482787

Schmidt, Torsten C; Jochmann, Maik A

2012-04-09

359

Stable isotopic analysis of pyrogenic organic matter in soils by liquid chromatography-isotope-ratio mass spectrometry of benzene polycarboxylic acids.  

PubMed

Pyrogenic organic matter (PyOM), the incomplete combustion product of organic materials, is considered stable in soils and represents a potentially important terrestrial sink for atmospheric carbon dioxide. One well-established method of measuring PyOM in the environment is as benzene polycarboxylic acids (BPCAs), a compound-specific method, which allows both qualitative and quantitative estimation of PyOM. Until now, stable isotope measurement of PyOM carbon involved measurement of the trimethylsilyl (TMS) or methyl (Me) polycarboxylic acid derivatives by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). However, BPCA derivatives can contain as much as 150% derivative carbon, necessitating post-analysis correction for the accurate measurement of ?C values, leading to increased measurement error. Here, we describe a method for ?C isotope ratio measurement and quantification of BPCAs from soil-derived PyOM, based on ion-exchange chromatography (IEC-IRMS). The reproducibility of the ?C measurement of individual BPCAs by IEC-IRMS was better than 0.35 (1?). The ?C-BPCA analysis of PyOM in soils, including at natural and artificially enriched C-abundance, produced accurate and precise ?C measurements. Analysis of samples that differed in ?C by as much as 900 revealed carryover of <1 between samples. The weighted sum of individual ?C-BPCA measurements was correlated with previous isotopic measurements of whole PyOM, providing complementary information for bulk isotopic measurements. We discuss potential applications of ?C-BPCA measurements, including the study of turnover rates of PyOM in soils and the partitioning of PyOM sources based on photosynthetic pathways. PMID:22468329

Yarnes, Christopher; Santos, Fernanda; Singh, Nimisha; Abiven, Samuel; Schmidt, Michael W I; Bird, Jeffrey A

2011-12-30

360

Lipid Biomarkers and Stable Isotope Signatures of Microbial Mats in Hot Springs of Kamchatka, Russia  

NASA Astrophysics Data System (ADS)

Various hot springs of the Uzon Caldera, Kamchatka, were analyzed for their chemical and stable isotope composition to better understand the relationship(s) between thermophilic microorganisms and the environments in which they live. The springs had water temperatures ranging from 40-90\\deg C and pH ranging from 5.6-5.9. Gases that emanated from the springs were composed predominantly of CO2 (20 to 90%), with lesser amounts of CH4, (< 20%), H2, NH3 and SO2. Because the springs were acidic, they contained little dissolved inorganic carbon (DIC: millimol L-1) and sulfide (< 200 ppb), yet in some cases where microbial activity was relatively high, these constituents reached the millimol L-1 and ppm range, respectively. Total biomass displayed a relatively large range of carbon isotope compositions that ranged from -5.7 to -22.4 per mil, which may reflect the large range of carbon sources, varied CO2 fixation pathways, or other unknown mechanisms. Microbial mats were freeze-dried and extracted for lipid biomarker analysis. The lipids were separated into hydrocarbon, sterol, ether lipid, free fatty acid, and phospholipid fatty acid (PLFA) fractions. Among these fractions, PLFA indicated the community structure and abundance for Bacteria while the ether lipid fraction provided analogous information for Archaea. Results of PLFA showed 16:0 as the most abundant fatty acid (33-44%), which is universal in all living organisms. Other significant biomarkers included 18:1? (19 to 24%), 18:2? (5 to 13%), 16:1? (3 to 12%), and 18:0 (2 to 7%). These biomarkers are characteristic of cyanobacteria, green-sulfur bacteria, and green non-sulfur bacteria, respectively, which are common autotrophic organisms in terrestrial hot springs. On the other hand, biomarkers of heterotrophic bacteria, such as iso- and anteiso-15:0 were low (2-8%), indicating that the bacterial carbon cycle was dominated by autotrophic organisms. Analogous archaeal constituents were present in significant abundance in the ether lipids fraction.

Romanek, C. S.; Mills, G. L.; Jones, M. E.; Paddock, L.; Li, Y.; Zhang, C. L.; Wiegel, J.

2004-12-01

361

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

362

Stable isotopes as a tool to apportion atmospheric iron.  

PubMed

Identification of atmospheric iron is a key parameter to understanding the source of iron in urban and remote areas. Atmospheric deposition of desert dust, which also can include an anthropogenic component, is a primary nutrient source for most of the open ocean. To better assess particulate matter (PM) sources specific to iron, we measured the iron isotopic composition of aerosols in two size fractions: PM with aerodynamic diameters less than 2.5 microm and less than 10 microm (PM2.5 and PM10, respectively). Using colocated samplers, atmospheric aerosol samples were collected in the U.S. desert Southwest at a mixed suburban/agricultural site near Phoenix, AZ. The measurements are presented as delta56Fe relative to the IRMM-014 (Institute for Reference Materials and Measurements) standard. Using multiple collector inductively coupled plasma mass spectrometry, we found differences in iron isotopic composition within the PM10 aerosol. Half of the PM10 samples had an iron isotopic signature similar to crustal material (+0.03 per thousand), which implicates wind-blown soil-dust as the primary source. The other PM10 samples showed a lighter iron isotopic composition, centered at -0.18 per thousand. Further analysis showed thatthe lighter iron was associated with winds originating from the southwest. This strongly suggests that there is a different PM10 source in this direction, with a distinct iron isotopic composition. The iron in the PM2.5 samples was usually substantially lighter than the corresponding PM10 samples, which is consistent with coarse and fine particles having different sources, again with distinctively different isotopic compositions. The magnitude of the iron isotopic difference between the PM10 and the PM2.5 size fractions (delta56Fe(PM10) - delta56Fe(PM2.5)) correlated with the PM2.5 concentrations of elements known to be emitted from industrial sources (Pb, Cd, As, V, and Cr). This observation implies that the isotopically light iron is created or emitted alongside industrial processes. Our data demonstrate that iron isotope composition can be a valuable tool in the source-apportionment of iron in atmospheric particles. PMID:19603642

Majestic, Brian J; Anbar, Ariel D; Herckes, Pierre

2009-06-15

363

Absolute and Relative Isotope Abundances Measured by Tunable Diode Laser Spectroscopy  

NASA Astrophysics Data System (ADS)

The potential for measuring absolute and relative isotope abundances by high resolution spectroscopy with tunable diode lasers as sources was studied. In order to achieve the sensitivity necessary to determine the absolute abundances of molecules containing long-lived radionuclides such as ('14)C an ('129)I, a resonant spectrophone based on the photoacoustic effect was used for detection. For safety, NH(,3) was used as a sample with air as a buffer gas when characterizing the performance of the TDL-spectrophone system. Frequency modulation of the TDL was employed. The optimum operating pressure was found to be 6.6 kPa(50 Torr). Substitution of Kr as a buffer gas yielded a fourfold increase in signal. It is estimated that with currently available TDLs a photoacoustic spectrometer should be capable of detecting ('14)CO(,2) and CH('129)I at the levels present in nuclear reactor containment gases. An isotope shift of CH(,3)('129) I relative to CH(,3)('127)I in the (nu)(,6) band of (0.0135 (+OR-) 0.0006) cm('-1) was measured by TDL linear absorption spectroscopy. To perform relative isotope abundance measurements a TDL was tuned over two adjacent, but well-resolved, rotation -vibration absorption lines, one of each isotopic species, while the transmitted radiation was monitored with a HgCdTe detector. The P(26) line of the (nu)(,1) band of N(,2)('18)O at 1225.3671 cm('-1) and the P(63) line of the (nu)(,1) band of N(,2)('16)O at 1225.4879 cm('-1) were chosen, for their line strength ratio is inversely proportional to the ratio of their natural abundances, and thereby yielded approximately equal absorbance for each isotopic species. A double-beam, single-detector spectrometer with wavelength modulation to minimize the effects of laser power and cell temperature fluctuations, has been adapted for use with a TDL. After samples of known ('18)O enrichment were used to calibrate the spectrometer, the (delta)('18)O of tropospheric N(,2)O was measured to be (8.05 (+OR-) 0.17)('o)/oo relative to a laboratory standard, or approximately 42('o)/oo relative to standard mean ocean water. After 190 days at 24(DEGREES)C no oxygen isotope exchange was observed between N(,2)('16)O and H(,2)('18)O.

Tucker, George Franklin

364

Reconstruction of Middle Eocene - Late Oligocene Southern Ocean paleoclimate through calcareous nannofossils and stable isotopes  

NASA Astrophysics Data System (ADS)

The transition from the ice free early Paleogene world to the glaciated conditions of the early Oligocene has been matter of discussion in the last years. This transition has not been monotonic but punctuated by numerous transient cooling and warming events. Here we present a summary of recent studies based on Nannofossil response to climatic changes during the Eocene and Oligocene. Collected data issue from high latitudes ODP Sites 748, 738, 744, 689 and 690. Based on a detailed revision of the biostratigraphy carried out through quantitative analysis, we conducted paleoecological studies on calcareous nannofossils through the late middle Eocene to the - late Oligocene interval to identify abundance variations of selected taxa in response to changes in sea surface temperature (SST) and trophic conditions. The nannofossil-based interpretation has been compared with detailed oxygen and carbon stable isotope stratigraphy confirming the climate variability in the Southern Ocean for this time interval. We identify the Middle Eocene Climatic optimum (MECO) event, related with the regional exclusion of Paleogenic warm-water taxa from the Southern Ocean, followed by the progressive cooling trend particularly emphasized during the cooling events at about 39 Ma, 37 Ma and 35.5 Ma. In the earliest Oligocene, marked changes in calcareous nannofossil assemblages are strikingly associated with the Oi-1 event recorded in perfect accordance with the oxygen isotope records. For most of the Oligocene we recorded a cold phase, while a warming trend is detected in the late Oligocene. In addiction, a marked increase of taxa thriving in eutrophic conditions coupled with a decrease in oligotrophic taxa, suggests the presence of a time interval (from about 36 Ma to about 26 Ma) with prevailing eutrophic conditions that correspond to an increase of the carbon stable isotope curve. This interval well corresponds with the clay mineral concentration that shows at Site 738 a higher concentration in illite (Ehrmann and Mackensen, 1992). This result can be interpreted as a major influx of weathering in the basin, bringing more nutrients to the surface water. Our data confirm a strong climate variability in the Southern Ocean during the middle Eocene - late Oligocene and nannofossils demonstrate to be useful tools for paleoclimatic and paleoceanographic reconstructions.

Villa, Giuliana; Fioroni, Chiara; Persico, Davide; Pea, Laura; Bohaty, Steve

2010-05-01

365

Stable isotope methodology in the pharmacokinetic studies of androgenic steroids in humans  

SciTech Connect

The use of stable isotopically labeled steroids combined with gas chromatography/mass spectrometry (GC/MS) has found a broad application in pharmacologic studies. Initially, stable isotopically labeled steroids served as the ideal analytic internal standard for GC/MS analysis; however, their in vivo use has expanded and has proven to be a powerful pharmacokinetic tool. We have successfully used stable isotope methodology to study the pharmacokinetic/bioavailability of androgens. The primary advantage of the technique is that endogenous and exogenous steroids with the same basic structure can be differentiated by using stable isotopically labeled analogs. The method was used to examine the pharmacokinetics of testosterone and testosterone propionate, and to clarify the influence of endogenous testosterone. Another advantage of the isotope methods is that steroidal drugs can be administered concomitantly in two formulations (e.g., solution and solid dosage). A single set of blood samples serves to describe the time course of the formulations being compared. This stable isotope coadministration technique was used to estimate the relative bioavailability of 17 alpha-methyltestosterone. 35 references.

Shinohara, Y.; Baba, S. (Tokyo College of Pharmacy (Japan))

1990-04-01

366

Inherent variation in stable isotope values and discrimination factors in two life stages of green turtles.  

PubMed

We examine inherent variation in carbon and nitrogen stable isotope values of multiple soft tissues from a population of captive green turtles Chelonia mydas to determine the extent of isotopic variation due to individual differences in physiology. We compare the measured inherent variation in the captive population with the isotopic variation observed in a wild population of juvenile green turtles. Additionally, we measure diet-tissue discrimination factors to determine the offset that occurs between isotope values of the food source and four green turtle tissues. Tissue samples (epidermis, dermis, serum, and red blood cells) were collected from captive green turtles in two life stages (40 large juveniles and 30 adults) at the Cayman Turtle Farm, Grand Cayman, and analyzed for carbon and nitrogen stable isotopes. Multivariate normal models were fit to the isotope data, and the Bayesian Information Criterion was used for model selection. Inherent variation and discrimination factors differed among tissues and life stages. Inherent variation was found to make up a small portion of the isotopic variation measured in a wild population. Discrimination factors not only are tissue and life stage dependent but also appear to vary with diet and sea turtle species, thus highlighting the need for appropriate discrimination factors in dietary reconstructions and trophic-level estimations. Our measures of inherent variation will also be informative in field studies employing stable isotope analysis so that differences in diet or habitat are more accurately identified. PMID:22902371

Vander Zanden, Hannah B; Bjorndal, Karen A; Mustin, Walter; Ponciano, Jos Miguel; Bolten, Alan B

2012-08-03

367

Stable carbon and nitrogen isotope ratios of sodium and potassium cyanide as a forensic signature.  

PubMed

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 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. Upon analysis, a few of the cyanide samples displayed nonhomogeneous isotopic content associated with degradation to a carbonate salt and loss of hydrogen cyanide. Most samples had highly reproducible isotope content. Of the 65 cyanide samples, >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. PMID:22040310

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

2011-10-31

368

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

369

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

370

Stable Carbon Isotope Fractionation by Sulfate-Reducing Bacteria  

PubMed Central

Biogeochemical transformations occurring in the anoxic zones of stratified sedimentary microbial communities can profoundly influence the isotopic and organic signatures preserved in the fossil record. Accordingly, we have determined carbon isotope discrimination that is associated with both heterotrophic and lithotrophic growth of pure cultures of sulfate-reducing bacteria (SRB). For heterotrophic-growth experiments, substrate consumption was monitored to completion. Sealed vessels containing SRB cultures were harvested at different time intervals, and ?13C values were determined for gaseous CO2, organic substrates, and products such as biomass. For three of the four SRB, carbon isotope effects between the substrates, acetate or lactate and CO2, and the cell biomass were small, ranging from 0 to 2. However, for Desulfotomaculum acetoxidans, the carbon incorporated into biomass was isotopically heavier than the available substrates by 8 to 9. SRB grown lithoautotrophically consumed less than 3% of the available CO2 and exhibited substantial discrimination (calculated as isotope fractionation factors [?]), as follows: for Desulfobacterium autotrophicum, ? values ranged from 1.0100 to 1.0123; for Desulfobacter hydrogenophilus, the ? value was 0.0138, and for Desulfotomaculum acetoxidans, the ? value was 1.0310. Mixotrophic growth of Desulfovibrio desulfuricans on acetate and CO2 resulted in biomass with a ?13C composition intermediate to that of the substrates. The extent of fractionation depended on which enzymatic pathways were used, the direction in which the pathways operated, and the growth rate, but fractionation was not dependent on the growth phase. To the extent that environmental conditions affect the availability of organic substrates (e.g., acetate) and reducing power (e.g., H2), ecological forces can also influence carbon isotope discrimination by SRB.

Londry, Kathleen L.; Des Marais, David J.

2003-01-01

371

Stable-isotope analyses of dinosaur eggshells: Paleoenvironmental implications  

NASA Astrophysics Data System (ADS)

Well-preserved clutches of dinosaur (sauropod) eggshells and skeletal remains have been discovered in the Upper Cretaceous Lameta limestones of the Kheda district, Gujarat, India, indicating a dinosaur nesting site. Oxygen-isotope analyses of the eggs show that the dinosaurs drank from a variety of freshwater bodies such as rivers and small evaporative pools, whereas the carbon-isotope values indicate that the reptiles were consuming plants that utilize the C3 photosynthetic pathway, e.g., small palms, shrubs, conifers, etc. Similar analyses of the host limestones suggest that they were deposited in a freshwater environment that provided the niche for large-scale breeding and nesting of the dinosaurs.

Sarkar, A.; Bhattacharya, S. K.; Mohabey, D. M.

1991-11-01

372

Stable water isotope characterization of human and natural impacts on land-atmosphere exchanges in the Amazon Basin  

Microsoft Academic Search

Stable water isotopes have been employed as a means of challenging, validating, and improving numerical models of the Amazon Basin since the 1980s. This paper serves as an exemplar of how characterization of human and natural impacts on surface-atmosphere water exchanges could beneficially exploit stable water isotope data and simulations. Interpretations of Amazonian isotopic data and model simulations are found

K. McGuffie; A. Henderson-Sellers

2004-01-01

373

Using Noble Gases to Identify Temperature and Amount Effects in Stable Isotope Records  

NASA Astrophysics Data System (ADS)

The interpretation of stable isotope records from many climate archives suffers from the difficulty of separating the various effects that influence the isotopic signature. This contribution evaluates the potential of dissolved noble gases in water as a complementary proxy for temperature (and in some cases precipitation), which is accessible in climate archives containing liquid water. The noble gas thermometer is based on the temperature dependence of noble gas solubilities in water and has primarily been applied to groundwater. Aquifers are no ideal paleoclimate archives in terms of resolution and age control, but provide the unique opportunity to relate stable isotope data to absolute noble gas temperatures (NGTs). In addition, the so-called excess air component in groundwater is increasingly being used as a proxy for precipitation and can be related to the amount effect in stable isotope data. In recent groundwater paleoclimate studies from regions affected by the Asian monsoon, noble gas data enabled a separation of temperature and amount effects in the stable isotope records. Although in principle this approach is rather straightforward, difficulties arise due to additional effects influencing both the stable isotopes and noble gases in groundwater, such as changes in vegetation cover and continentality of the sites and the global ice volume effect. In recent groundwater of East China affected by heavy exploitation, non-climatic effects on the stable isotope signature have also been detected. In Holocene groundwater from Northwest India, a covariation of the climate proxies stable isotopes and excess air has been found. A group of early to mid Holocene samples depleted in stable isotopes and enriched in excess air indicates a phase of strong monsoon during the Holocene climate optimum. Both tracers indicate a drying trend in the second half of the Holocene, followed by more humid conditions in the youngest part of the record. A temporary rise of NGT in the dry late Holocene phase may reflect a change in the soil temperature - air temperature relationship. Recent developments aim at expanding the use of NGTs to other archives than groundwater, such as fluid inclusions in speleothems and sediment pore waters. Although presently no complete data sets from such archives exist, the potential of noble gases in these new archives is promising, in particular with regard to complementing stable isotope data.

Aeschbach-Hertig, W.; Wieser, M.

2011-12-01

374

Abundant and stable char residues in soils: implications for soil fertility and carbon sequestration.  

PubMed

Large-scale soil application of biochar may enhance soil fertility, increasing crop production for the growing human population, while also sequestering atmospheric carbon. But reaching these beneficial outcomes requires an understanding of the relationships among biochar's structure, stability, and contribution to soil fertility. Using quantitative (13)C nuclear magnetic resonance (NMR) spectroscopy, we show that Terra Preta soils (fertile anthropogenic dark earths in Amazonia that were enriched with char >800 years ago) consist predominantly of char residues composed of ~6 fused aromatic rings substituted by COO(-) groups that significantly increase the soils' cation-exchange capacity and thus the retention of plant nutrients. We also show that highly productive, grassland-derived soils in the U.S. (Mollisols) contain char (generated by presettlement fires) that is structurally comparable to char in the Terra Preta soils and much more abundant than previously thought (~40-50% of organic C). Our findings indicate that these oxidized char residues represent a particularly stable, abundant, and fertility-enhancing form of soil organic matter. PMID:22834642

Mao, J-D; Johnson, R L; Lehmann, J; Olk, D C; Neves, E G; Thompson, M L; Schmidt-Rohr, K

2012-08-20

375

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

376

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

377

Late Glacial and Holocene paleoceanography of the central and northern Greenland Sea based on foraminifera, stable isotopes and sediments  

NASA Astrophysics Data System (ADS)

Micropaleontological, sedimentological and stable isotope studies of four sediment cores from the central and northern Greenland Sea are used to reconstruct the Late Glacial and Holocene paleoceanography. The chronology and correlation of the sediments were based on the absolute radiocarbon ages. The data show a typical transition from the glacial towards the interglacial, with a distinct Holocene Thermal Maximum (HTM), expressed by maximum abundances of total and subpolar foraminifera. In the southernmost record, from the southern slope of the Vesterisbanken Seamount, the HTM is interrupted by two events of significantly lower foraminiferal abundance. The cooling trend after the HTM with >95% polar specimens in the planktic foraminifer associations is reversed in the Late Holocene part of that record, which is unusual, compared to other records from the northern Nordic Seas. Both total and subpolar foraminifer abundances return rapidly to the values comparable with the HTM, which indicates a strong influence of Atlantic Water (AW). This is not observed in the northernmost record from the Greenland Fracture Zone and therefore the AW must have come from a different direction. The Greenland Fracture Zone records reveal a planktic isotope pattern similar to that found on the Western Svalbard Slope indicating a connection between the two sites. The area was strongly influenced by the AW since the Early Holocene. However, around 3 cal. ka BP the inflow of AW was reduced, resulting in a cooling and a stronger stratification of the water column due to the thickening of the cold, low-salinity surface layer.

Telesi?ski, M. M.; Spielhagen, R. F.

2012-04-01

378

The Role of Stable Isotopes in Geochemistries of All Kinds  

Microsoft Academic Search

Although I was surprised by the invitation to write a prefatory chapter for the Annual Review of Earth and Planetary Sciences , I decided to accept this oppor- tunity to write about my experiences as a participant in the isotope geochemistry revolution that occurred 40-50 years ago. My own experiences during the early stages of my life were uniquely intertwined

S. Epstein

1997-01-01

379

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

380

Source Evaluation of Diazinon Using Stable Carbon Isotope Ratio  

Microsoft Academic Search

Soil samples were collected between May 27 and October 28, 2005, at sites in Yurihonjo City, Akita Prefecture, Japan. Diazinon, an extensively used organophosphate insecticide, was detected in high concentrations. Recent advances in analytical techniques enabled identification of the source of the high levels of diazinon by measuring the 13C isotope ratio of diazinon. Eight diazinon products primarily used in

Hiroto Kawashima; Yasuhiro Katayama

2010-01-01

381

Stable Isotope Ratio Measurement by NAA for Environmental Source Identification  

Microsoft Academic Search

The purpose of applying neutron activation analysis to the study of isotopic ratios is to examine whether ratios could be measured that are difficult to determine by other means and that could be used to distinguish between materials from different types of sources. The NAA is a sensitive analytical method for many elements that are typically present in levels too

Jeckong Gone; Ilhan Olmez; Michael R. Ames

1999-01-01

382

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

383

Isotopic tracing of clear water sources in an urban sewer: A combined water and dissolved sulfate stable isotope approach.  

PubMed

This paper investigates the potential of stable isotopes of both water (deltaD and deltaOH(2)O18) and dissolved sulfate (delta(34)S and deltaOSO(4)18) for determining the origin and the amount of clear waters entering an urban sewer. The dynamics of various hydrological processes that commonly occur within the sewer system such as groundwater infiltration, rainwater percolation, or stormwater release from retention basins, can be readily described using water isotope ratios. In particular, stable water isotopes indicate that the relative volumes of infiltrated groundwater and sewage remain approximately constant and independent of wastewater flow rate during the day, thus demonstrating that the usual quantification of parasitic discharge from minimal nocturnal flow measurements can lead to completely erroneous results. The isotopic signature of dissolved sulfate can also provide valuable information about the nature of water inputs to the sewage flow, but could not be used in our case to quantify the infiltrating water. Indeed, even though the microbial activity had a limited effect on the isotopic composition of dissolved sulfate at the sampling sites investigated, the dissolved sulfate concentration in sewage was regulated by the formation of barite and calcium-phosphate mineral species. Sulfate originating from urine was also detected as a source using the oxygen isotopic composition of sulfate, which suggests that deltaOSO(4)18 might find use as a urine tracer. PMID:19822346

Houhou, J; Lartiges, B S; France-Lanord, C; Guilmette, C; Poix, S; Mustin, C

2009-09-12

384

Zinc isotope ratio imaging of rat brain thin sections from stable isotope tracer studies by LA-MC-ICP-MS.  

PubMed

Zinc stable isotope tracers (??Zn and ??Zn) were injected into rats at two different time points to investigate the feasibility of using tracers to study zinc kinetics at the microscale within distinct tissue features. Laser ablation coupled to multi-collector ICP-MS was used to analyse average isotope ratios in liver thin sections and to generate bio-images showing zinc isotope ratio distribution in brain thin sections. Average isotope ratios of all samples from treated animals were found to be statistically different (P < 0.05) from samples from untreated control animals. Furthermore, differing isotope ratios in physiological features of the brain, namely hippocampus, amygdala, cortex and hypothalamus, were identified. This indicates that these regions differ in their zinc metabolism kinetics. While cortex and hypothalamus contain more tracer two days after injection than 14 days after injection, the opposite is true for hippocampus and amygdala. This study showed that stable isotope tracer experiments can be combined with laser ablation MC-ICP-MS to measure trace element kinetics in tissues at a microscale level. PMID:22907676

Urgast, Dagmar S; Hill, Sarah; Kwun, In-Sook; Beattie, John H; Goenaga-Infante, Heidi; Feldmann, Jrg

2012-08-20

385

Stable Nitrogen and Carbon Isotope Ratios Indicate Traditional and Market Food Intake in an Indigenous Circumpolar Population123  

PubMed Central

The transition of a society from traditional to market-based diets (termed the nutrition transition) has been associated with profound changes in culture and health. We are developing biomarkers to track the nutrition transition in the Yupik Eskimo population of Southwest Alaska based on naturally occurring variations in the relative abundances of carbon and nitrogen stable isotopes (?15N and ?13C values). Here, we provide three pieces of evidence toward the validation of these biomarkers. First, we analyzed the ?15N and ?13C values of a comprehensive sample of Yupik foods. We found that ?15N values were elevated in fish and marine mammals and that ?13C values were elevated in market foods containing corn or sugar cane carbon. Second, we evaluated the associations between RBC ?15N and ?13C values and self-reported measures of traditional and market food intake (n = 230). RBC ?15N values were correlated with intake of fish and marine mammals (r = 0.52; P < 0.0001). RBC ?13C values were correlated with intake of market foods made from corn and sugar cane (r = 0.46; P < 0.0001) and total market food intake (r = 0.46; P < 0.0001). Finally, we assessed whether stable isotope ratios captured population-level patterns of traditional and market intake (n = 1003). Isotopic biomarkers of traditional and market intake were associated with age, community location, sex, and cultural identity. Self-report methods showed variations by age and cultural identity only. Thus, stable isotopes show potential as biomarkers for monitoring dietary change in indigenous circumpolar populations.

Nash, Sarah H.; Bersamin, Andrea; Kristal, Alan R.; Hopkins, Scarlett E.; Church, Rebecca S.; Pasker, Renee L.; Luick, Bret R.; Mohatt, Gerald V.; Boyer, Bert B.; O'Brien, Diane M.

2012-01-01

386

Stable isotopes reveal individual variation in migration strategies and habitat preferences in a suite of seabirds during the nonbreeding period.  

PubMed

Information on predator and prey distributions is integral to our understanding of migratory connectivity, food web dynamics and ecosystem structure. In marine systems, although large animals that return to land can be fitted with tracking devices, minimum instrument sizes preclude deployments on small seabirds that may nevertheless be highly abundant and hence major consumers. An increasingly popular approach is to use N and C stable isotope analysis of feathers sampled at colonies to provide information on distribution and trophic level for the preceding, and generally little-known, nonbreeding period. Despite the burgeoning of this research, there have been few attempts to verify such relationships. In this study, we demonstrate a clear correspondence between isotope ratios of feathers and nonbreeding distributions of seven species from South Georgia tracked using loggers. This generated a rudimentary isoscape that was used to infer the habitat preferences of eight other species ranging in size from storm petrels to albatrosses, and which could be applied, with caveats, in other studies. Differences in inferred distribution within and between species had major implications for relative exposure to anthropogenic threats, including climate change and fisheries. Although there were no differences in isotope values between sexes in any of the smaller petrels, mean stable C (delta(13)C), but not stable N isotope ratios (delta(15)N), tended to be greater in females than males of the larger, and more sexually size-dimorphic species. This indicates a difference in C source (distribution), rather than trophic level, and a correspondence between the degree of sexual size dimorphism in Procellariiformes and the level of between-sex niche segregation. PMID:19377898

Phillips, Richard A; Bearhop, Stuart; McGill, Rona A R; Dawson, Deborah A

2009-04-18

387

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

388

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

2012-03-20

389

High-sensitivity stable-isotope probing by a quantitative terminal restriction fragment length polymorphism protocol.  

PubMed

Stable-isotope probing (SIP) has proved a valuable cultivation-independent tool for linking specific microbial populations to selected functions in various natural and engineered systems. However, application of SIP to microbial populations with relatively minor buoyant density increases, such as populations that utilize compounds as a nitrogen source, results in reduced resolution of labeled populations. We therefore developed a tandem quantitative PCR (qPCR)-TRFLP (terminal restriction fragment length polymorphism) protocol that improves resolution of detection by quantifying specific taxonomic groups in gradient fractions. This method combines well-controlled amplification with TRFLP analysis to quantify relative taxon abundance in amplicon pools of FAM-labeled PCR products, using the intercalating dye EvaGreen to monitor amplification. Method accuracy was evaluated using mixtures of cloned 16S rRNA genes, DNA extracted from low- and high-G+C bacterial isolates (Escherichia coli, Rhodococcus, Variovorax, and Microbacterium), and DNA from soil microcosms amended with known amounts of genomic DNA from bacterial isolates. Improved resolution of minor shifts in buoyant density relative to TRFLP analysis alone was confirmed using well-controlled SIP analyses. PMID:22038597

Andeer, Peter; Strand, Stuart E; Stahl, David A

2011-10-28

390

Isotopic Analysis of Fingernails as a USGS Open House Demonstration of the Use of Stable Isotopes in Foodweb Studies  

NASA Astrophysics Data System (ADS)

The USGS Isotope Tracers Project uses stable isotopes and tritium to add a unique dimension of chemical information to a wide range of environmental investigations. The use and application of isotopes is usually an unfamiliar and even esoteric topic to the general public. Therefore during three USGS open house events, as a public outreach effort, we demonstrated the use of stable isotopes by analyzing nitrogen and carbon isotopes from very small fragments of fingernail from willing participants. We titled the exhibit "You Are What You Eat". The results from all participants were plotted on a graph indicating the general influence of different food groups on the composition of body tissues as represented by fingernails. All participants were assigned a number and no personal-identification information was collected. A subset of participants provided us with an estimate of the number of days a week various foods were eaten and if they were vegetarians, vegans or non-vegetarians. Volunteers from our research group were on hand to explain and discuss fundamental concepts such as how foods attain their isotopic composition, the difference between C3 and C4 plants, the effects of assimilation, trophic enrichment, and the various uses of stable isotopes in environmental studies. The results of the fingernail analyses showed the variation of the range of isotopic compositions among about 400 people at each event, the distinct influence of C4 plants (mainly corn and cane sugar) on our carbon isotopic composition, and the isotopic differences between vegetarians and non vegetarians among other details (http://wwwrcamnl.wr.usgs.gov/isoig/projects/fingernails/). A poll of visitors attending the open house event in 2006 indicated that "You Are What You Eat" was among the most popular exhibits. Following the first two open house events we were contacted by a group of researchers from Brazil who had completed a very similar study. Our collaboration resulted in a publication in the American Journal of Physical Anthropology (Nardoto et al., 2006). This study found that despite global trends toward dietary homogenization, regional differences in food resources and dietary preferences were recorded in the carbon and nitrogen isotopic compositions of fingernails.

Silva, S. R.; Kendall, C.; Young, M. B.; Choy, D.

2011-12-01

391

Characterizing Atmospheric Teleconnections in the Pliocene Epoch Using Stable Isotopes  

NASA Astrophysics Data System (ADS)

As atmospheric concentrations of CO2 continue to increase due to human activities, it becomes increasingly vital to understand how the hydrologic cycle has responded to warmer global temperatures in the past. The Pliocene climate offers an ideal window into a climate system in equilibrium with current atmospheric pCO2. During the Pliocene, the Southern United States was wetter than modern, an observation in contrast to our current understanding of future warming scenarios, which involve the expansion and poleward migration of the subtropical dry zone. Two distinct hypotheses exist to explain these anomalously wet conditions. The first is that they were a product of Pliocene boundary conditions including lower topography in the Western US. The second is that these conditions were caused by a south-shifted subtropical jet due to a weak zonal temperature gradient in the tropical Pacific, a state characteristic of modern El Nio years. To resolve this question, we seek to characterize atmospheric circulation over the Western US through the Plio-Pleistocene. In order to do this, we analyzed regional isotopic shifts from 4.0 - 1.0 Ma at 5 localities across the Western US measured in pedogenic carbonates. In addition, we compare these isotope profiles to modern observations of seasonal isotopic shifts in precipitation between phases of the El Nio Southern Oscillation (ENSO) at 77 stations across the country measured as part of the United States Network of Isotopes in Precipitation (USNIP). We find that when accounting for seasonality of carbonate precipitation, isotopic shifts across the late Pliocene in all but one locality match modern shifts between El Nio and Neutral phases of ENSO. In addition, isotopic shifts at all localities spanning 4.0 - 1.0 Ma change direction at the Plio-Pleistocene boundary to return to mid-Pliocene values by the mid-Pleistocene. Pleistocene atmospheric circulation is much better constrained over the Western US and, similar to El Nio circulation, involves a deeper Aleutian low and south-shifted subtropical jet. These two independent results support the idea that wet conditions in the Pliocene Southern US can be attributed to a south-shifted subtropical jet controlled by the temperature structure of the Equatorial Pacific. This also suggests that teleconnections between the tropics and mid-latitudes were similar to modern despite a weaker meridional temperature gradient.

Winnick, M. J.; Welker, J. M.; Chamberlain, C. P.

2011-12-01

392

Stable isotope data of selected gastropod genera as proxies for seawater chemistry of the Central Paratethys  

NASA Astrophysics Data System (ADS)

Geodynamic processes influenced the complex evolution of the Paratethys, an extended marginal sea, which is characterised by intermittently open and closed marine seaways with its surrounding oceans. Especially in the Miocene, this led to substantial changes in marine environments and ecosystems by changing basin geometries, water circulation, water depth, water chemistry, climate etc. Investigations of stable isotopes of fossil carbonate shells provide information about paleoenvironmental parameters of the ancient seawater. Oxygen and carbon isotope data of selected gastropod genera, mainly Turritellidae, are used to reconstruct paleoenvironmental parameters of different time slices of the Miocene of Austrian Neogene basins. Recent Turritellidae live in a wide range of environments, mainly shallow infaunal or epifaunal, but prefer fully marine conditions. Stable isotope investigations of recent specimens support their usefulness as isotopic indicators for environmental parameters. For detecting diagenetic alterations of the aragonitic gastropod shells, samples were analysed for their shell mineralogy and microstructures with X-ray diffraction analyses and scanning electron microscopy prior to stable isotope analyses. Several microsamples for isotope analyses of each shell were taken to test the intrashell variability. Oxygen and carbon isotopes for Karpatian and Badenian turritellids from the Vienna Basin and the Korneuburg Basin show slightly lighter oxygen and carbon isotope values for the Karpatian. In addition to turritellids, two other gastropod genera (Ocenebra and Granulolabium), both preferring an intertidal habitat and tolerating some salinity fluctuations, were investigated, yielding information about mixing of seawater with freshwater. So parameters for different environments can be obtained, and also comparisons of different gastropod genera are possible. The study was supported by the Austrian Science Foundation (FWF), project "Stable isotopes and changing Miocene palaeoenvironments in the East Alpine region" (P-14366 BIO), and project "Evolution Versus Migration: Changes in Austrian Marine Miocene Molluscan Paleocommunities" (P-13745 BIO).

Latal, C.; Piller, W. E.; Harzhauser, M.

2003-04-01

393

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

394

Heavy Element Abundances and Isotope Anomalies in HR7775 and Chi LUPI  

NASA Astrophysics Data System (ADS)

Over the past few years a GTO team project hasobtained extensive GHRS echelle data of UV transitionsof heavy elements in the Hg-Mn stars chi Lupi andKappa Cancri. Isotopic anomalies, in which only theheaviest isotope of Hg, Pt and Tl is present, havebeen observed in chi Lupi, but are apparently absentin Kappa Cancri. Kappa Cancri is distinguished fromchi Lupi by both its higher effective temperature andits larger Mn abundance. To help constraintheoretical interpretations of the abundance andisotope anomalies, this program will observe the Hg-Mnstar HR7775, which has the same effective temperatureas chi-Lupi, but also has substantially higher Mn andBi abundances. Observations of HR 7775 will includelines of B III, S I, Au II and III, Pt I, II, and III,Hg II and III, Ru II, Zr III, Ge I, As I, Cd II, Gd III,Ta II, Sb II and N I. Additional observations ofchi Lupi will also be obtained including observationsof Bi III, Tl III, Cu II and Ir II.

Brandt, John

1995-07-01

395

Strontium stable isotope behaviour in foraminiferal calcite and the retrieval of marine records  

NASA Astrophysics Data System (ADS)

The stable strontium (88Sr/86Sr) isotope composition of seawater recorded in sedimentary foraminifera potentially provides key information on variations in the composition of material delivered by continental weathering to the oceans and on changes in carbonate productivity over time. However, recent studies suggest a significant temperature dependent fractionation of Sr stable isotopes during the precipitation of calcium carbonate, which must be quantified before seawater records can be accurately retrieved [1, 2]. This study presents high-precision stable Sr isotope data (10 ppm 2 s.d.) for core-top planktonic foraminifera from sites in the South Atlantic with a range of annual sea surface temperatures of 18 - 28C, and preliminary data for quaternary marine foraminiferal records from the SE Indian Ocean. These results indicate that there is no signficiant variation in the stable isotope composition of an individual species across the temperature range studied here, but there are resolvable differences in the offset from seawater between species. In this case, seawater stable Sr isotope records can be reconstructed without the necessity of a temperature correction. The preliminary results for a glacial-interglacial planktonic foraminifera record indicate that there are no resolvable variations in the stable isotope ratios over this time interval, indicating that there are no significant variations in the Sr isotope composition of continental runoff or carbonate productivity in the oceans over this time interval. [1] Fietzke, J., Eisenhauer, A. (2006), Geochem. Geophys. Geosyst., 7, (8), 1-6 . [2] Ruggerburg, A., Fietzke, J., Liebetrau, V. Eisenhauer, A., Dullo, W-C., Freiwald, A. (2008). Earth Plan. Sci. Lett. 269, 570-575

Stevenson, E.; Burton, K.; Rickaby, R.; Parkinson, I. J.; Anand, P.; Hathorne, E.

2009-12-01

396

Absolute isotopic composition of molybdenum and the solar abundances of the p-process nuclides Mo92,94  

Microsoft Academic Search

The isotopic composition of molybdenum has been measured with high precision using a thermal ionization mass spectrometer, the linearity of which has been verified by measuring the isotopically-certified reference material for strontium (NIST 987). The abundance sensitivity of the mass spectrometer in the vicinity of the molybdenum ion beams has been carefully examined to ensure the absence of tailing effects.

M. E. Wieser; J. R. de Laeter

2007-01-01

397

Sr and Nd isotope ratios and REE abundances of moraines in the mountain areas surrounding the Taklimakan Desert, NW China  

Microsoft Academic Search

The first systematic data of Sr and Nd isotopic ratios, REE abundances, major element and mineral compositions are reported for the Chinese moraines from the western Kunlun Mts. and southern and north- ern flanks of the Tianshan Mts. and soils from the Tibet Plateau. This study was conducted in order to characterize the isotopic and geochemical features of these moraines

QING CHANG; TAKASHI MISHIMA; SADAYO YABUKI; YOSHIO TAKAHASHI; HIROSHI SHIMIZU

398

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

399

Neutrino scattering off the stable even-even Mo isotopes  

NASA Astrophysics Data System (ADS)

Inelastic neutrino-nucleus reaction cross sections are studied focusing on the neutral current processes. Particularly, we investigate the angular and initial neutrino-energy dependence of the differential and integrated cross sections for low and intermediate energies of the incoming neutrino. The nuclear wave functions for the initial and final nuclear states are constructed in the context of the quasi-particle random phase approximation (QRPA) tested on the reproducibility of the low-lying energy spectrum. The results presented here refer to the isotopes Mo92, Mo94, Mo96, Mo98 and Mo100. These isotopes could play a significant role in supernova neutrino detection in addition to their use in double-beta and neutrinoless double-beta decay experiments (e.g. MOON, NEMO III).

Balasi, K. G.; Kosmas, T. S.; Divari, P. C.

2009-11-01

400

Preliminary mineralogic, fluid inclusion, and stable isotope study of the Mahd adh Dhahab gold mine, Kingdom of Saudi Arabia  

USGS Publications Warehouse

The Mahd adh Dhahab mine, located about 280 km northeast of Jiddah, Kingdom of Saudi Arabia, has yielded more than 2 million ounces of gold from periodic production during the past 3,000 years. A new orebody on the southern side of the ancient workings, known as the South orebody, is being developed by Gold Fields-Mahd adh Dhahab Limited. A suite of samples was collected from the newly exposed orebody for preliminary mineralogic, stable isotope, fluid inclusion, and geochemical studies. The Mahd adh Dhahab deposit is in the carapace of a Proterozoic epizonal rhyolite stock that domed pyroclastic and metasedimentary rocks of the Proterozoic Halaban group. Ore of gold, silver, copper, zinc, tellurium, and lead is associated with north-trending, steeply dipping quartz veins in a zone 1,000 m long and 400 m wide. The veins include an assemblage of quartz-chlorite-pyrite-hematite-chalcopyrite-sphalerite-precious metals, which is similar to the mineral assemblage at the epithermal deposit at Creede, Colorado. The primary ore contains abundant chalcopyrite, sphalerite, and pyrite in addition to a complex precious metal assemblage. Gold and silver occur principally as minute grains of telluride minerals disseminated in quartz-chlorite-hematite and as inclusions in chalcopyrite and sphalerite. Telluride minerals include petzite, hessite, and sylvanite. Free gold is present but not abundant. All of the vein-quartz samples contained abundant, minute inclusions of both low-density, vapor-rich fluids and liquid-rich fluids. Primary fluid inclusions yielded homogenization temperatures of from 110? to 238? C. Preliminary light-stable isotope studies of the sulfide minerals and quartz showed that all of the d34S values are between 1.2 and 6.3 per mil, which is a typical range for hydrothermal sulfide minerals that derive their sulfur from an igneous source. The data-suggest that the sulfide sulfur isotope geochemistry was controlled by exchange with la large sulfur isotope reservoir at depth. The d18O values of all stages of vein quartz in the South orebody range between 8.5 and 11.1 per mil. This range is similar to that for quartz from the North orebody and indicates that the hydrothermal system consisted of dominantly exchanged meteoric water, which was uniform in temperature and d18O content throughout the area during the entire period of mineralization. Lead isotope analyses of two galena samples indicate that the lead in the South orebody is less radiogenic than that from the North orebody and confirm that the lead was derived from oceanic crust approximately 700 Ma ago.

Rye, Robert O.; Hall, W. E.; Cunningham, C. G.; Czamanske, G. K.; Afifi, A. M.; Stacey, J. S.

1983-01-01

401

Turnover of Stable Isotopes Due to Growth and Metabolism in Zebrafish, Danio Rerio  

NASA Astrophysics Data System (ADS)

Stable isotope ratios of carbon (13C/12C), nitrogen (15 N/14N) and sulfur (34S/32S) in animal tissues can be used as tracers of the nutrient sources of organisms' diets and determining trophic interactions in ecosystems. The isotopic turnover of these elements in a predator's tissues reflects the isotopic signature of the predator's diet (the prey). The rate at which an organism takes up the isotopic signature of its food is correlated with its growth rate and/or metabolism. Hence unless baseline isotopic turnover rates are known, the isotopic signature of a consumer may lead to misinterpretation of predator-prey relationships. Laboratory studies provide isotopic turnover rates of organisms under controlled conditions, which serve as models for understanding the rates at which organisms in the field isotopically incorporate new diets. This study examines the isotopic turnover rates of carbon, nitrogen and sulfur in response to a dietary switch in young zebrafish, Danio rerio. Zebrafish, raised on commercial fish food (8.2 0.5%, d34S; were fed a new, isotopically distinct diet (2.9 0.5%, d34S) and the rate at which zebra fish muscle tissues changed towards the isotopic signature of their new food was monitored. Preliminary results show a change in the fish sulfur isotope composition of roughly 0.03% per day towards the sulfur isotope ratio of the new food. At the observed turnover rate, approximately 180 days would be required for the zebrafish muscle tissue to resemble a new food. The study is also investigating the importance of growth versus metabolism as a predictor of isotope turnover rate in zebra fish tissues.

Tarboush, R.; MacAvoy, S.; Macko, S.; Connaughton, V.

2002-05-01

402

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

403

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

404

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

405

Using chromium stable isotope ratios to quantify Cr(VI) reduction: Lack of sorption effects  

USGS Publications Warehouse

Chromium stable isotope values can be effectively used to monitor reduction of Cr(VI) in natural waters. We investigate effects of sorption during transport of Cr(VI) which may also shift Cr isotopes values, complicating efforts to quantify reduction. This study shows that Cr stable isotope fractionation caused by sorption is negligible. Equilibrium fractionation of Cr stable isotopes between dissolved Cr-(VI) and Cr(VI) adsorbed onto ??-Al2O3 and goethite is less than 0.04???. (53Cr/52Cr) under environmentally relevant pH conditions. Batch experiments at pH 4.0 and pH 6.0 were conducted in series to sequentially magnify small isotope fractionations. A simple transport model suggests that adsorption may cause amplification of a small isotope fractionation along extreme fringes of a plume, leading to shifts in 53Cr/52Cr values. We therefore suggest that isotope values at extreme fringes of Cr plumes be critically evaluated for sorption effects. A kinetic effect was observed in experiments with goethite at pH 4 where apparently lighter isotopes diffuse into goethite clumps at a faster rate before eventually reaching equilibrium. This observed kinetic effect may be important in a natural system that has not attained equilibrium and is in need of further study. Cr isotope fractionation caused by speciation of Cr(VI) between HCrO4- and CrO42- was also examined, and we conclude that it is not measurable. In the absence of isotope fractionation caused by equilibrium speciation and sorption, most of the variation in ??53 Cr values may be attributed to reduction, and reliable estimates of Cr reduction can be made.

Ellis, A. S.; Johnson, T. M.; Bullen, T. D.

2004-01-01

406

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

407

Stable carbon and nitrogen isotope enrichment in primate tissues  

PubMed Central

Isotopic studies of wild primates have used a wide range of tissues to infer diet and model the foraging ecologies of extinct species. The use of mismatched tissues for such comparisons can be problematic because differences in amino acid compositions can lead to small isotopic differences between tissues. Additionally, physiological and dietary differences among primate species could lead to variable offsets between apatite carbonate and collagen. To improve our understanding of the isotopic chemistry of primates, we explored the apparent enrichment (?*) between bone collagen and muscle, collagen and fur or hair keratin, muscle and keratin, and collagen and bone carbonate across the primate order. We found that the mean ?* values of proteinaceous tissues were small (?1), and uncorrelated with body size or phylogenetic relatedness. Additionally, ?* values did not vary by habitat, sex, age, or manner of death. The mean ?* value between bone carbonate and collagen (5.61.2) was consistent with values reported for omnivorous mammals consuming monoisotopic diets. These primate-specific apparent enrichment values will be a valuable tool for cross-species comparisons. Additionally, they will facilitate dietary comparisons between living and fossil primates. Electronic supplementary material The online version of this article (doi:10.1007/s00442-010-1701-6) contains supplementary material, which is available to authorized users.

Carter, Melinda L.; Karpanty, Sarah M.; Zihlman, Adrienne L.; Koch, Paul L.; Dominy, Nathaniel J.

2010-01-01

408

Determination of Trophic Transfer at a Created Intertidal Oyster ( Crassostrea ariakensis ) Reef in the Yangtze River Estuary Using Stable Isotope Analyses  

Microsoft Academic Search

Oysters can create reefs that provide habitat for associated species resulting in elevated resident abundances, lower mortality\\u000a rates, and increased growth and survivorship compared to other estuarine habitats. However, there is a need to quantify trophic\\u000a relationships and transfer at created oyster reefs to provide a better understanding of their potential in creating suitable\\u000a nekton habitat. Stable isotope analyses (?13C

Wei-min Quan; Austin T. Humphries; Li-yan Shi; Ya-qu Chen

409

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

410

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

411

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

412

Stable isotope determination of ester and ether methyl moieties in plant methoxyl groups.  

PubMed

Plant methoxyl groups of lignin and pectin have both distinct stable hydrogen isotope (?(2)H) and carbon isotope (?(13)C) values that can be used for studying environmental processes and for investigating the origin and authenticity of biomaterials. Up to now, the reported methods have been applied only to determine isotope values of the bulk plant methoxyl pool. In this work, we have applied several methods to distinguish between stable isotope ratios of methoxyl groups of pectin and the bulk plant methoxyl pool. Our results demonstrate that by applying alkaline hydrolysis to specifically cleave off the ester methyl moiety (pectin-like), we can distinguish ?(2)H and ?(13)C values of the pectin methoxyl pool from the bulk methoxyl pool. No measureable isotope discrimination was observed either during sample preparation or during analytical measurement. Furthermore, using this method, no major isotope difference in either the hydrogen or carbon isotope signature of the methoxyl groups of plant pectin a