نتایج جستجو برای: isotopic composition

تعداد نتایج: 273380  

Journal: :Global Biogeochemical Cycles 2011

2010
Camille Risi Sandrine Bony Françoise Vimeux Christian Frankenberg David Noone John Worden

[1] The goal of this paper is to investigate the added value of water isotopic measurements to estimate the relative influence of large‐scale dynamics, convection, and land surface recycling on the Sahelian water budget. To this aim, we use isotope data in the lower tropospheric water vapor measured by the SCIAMACHY and TES satellite instruments and in situ precipitation data from the Global Ne...

2016
Susan H. Little Derek Vance Silke Severmann

Zinc is an essential micronutrient and its concentration and isotopic composition in marine sediments represent promising tracers of the ocean carbon cycle. However, gaps remain in our understanding of the modern marine cycle of Zn, including an explanation of the heavy Zn isotopic composition of seawater relative to the known inputs, and the identity of a required missing sink for light Zn iso...

2010
Anne Lorrain Yves-Marie Paulet Laurent Chauvaud Nicolas Savoye Anne Donval Christelle Saout

There have been several studies where the isotopic composition of organisms has been determined seasonally, but fewer have examined separate organs. In this context, separate organs (e.g. gonad, digestive gland and muscle), of a suspension-feeder, the scallop Pecten maximus, were used to assess seasonal changes of both stable isotopes and biochemical components. Our study used multiple indicato...

2006
Thomas M. McCollom Jeffrey S. Seewald

Although it is widely believed that production of organic compounds by Fischer-Tropsch synthesis and related processes occurs in many geologic environments, unambiguous identification of compounds with an abiotic origin in natural samples has been hampered by a lack of means to discriminate between abiotic compounds and organic matter from biological sources. While isotopic compositions might p...

2015
François L.H. Tissot Nicolas Dauphas

The U/U isotopic composition of uranium in seawater can provide important insights into the modern U budget of the oceans. Using the double spike technique and a new data reduction method, we analyzed an array of seawater samples and 41 geostandards covering a broad range of geological settings relevant to low and high temperature geochemistry. Analyses of 18 seawater samples from geographicall...

2010
S. Gromov A. M. Brenninkmeijer

Isotope composition, in many cases, holds unique information on the sources, chemical modification and sinks of atmospheric trace gases. Vital to the interpretation and use of an increasing number of isotope analyses is appropriate modelling. However, the exact implementation of isotopic information in chemistry-climate models is a challenge, and often studies use simplifications which limit th...

2009
R. A. MEWALDT

We present new observations of the isotopic composition of low-energy He, C, N, 0, and Ne nuclei. The observations cover the energy interval from ,...., 5 to 30 MeV per nucleon, the energy range where the "anomalous cosmic ray" fluxes of He, N, 0, and Ne have been observed. We compare the isotopic composition of the anomalous cosmic rays with that of higher-energy galactic cosmic rays in an eff...

2018
Magali Ader Pierre Cartigny Jean-Paul Boudou Jae-Ho Oh Eddy Petit Marc Javoy

Nitrogen content and isotopic composition of carbonaceous-rich metasediments were determined by online and sealed-tube combustion using ultra-high vacuum line and static mass spectrometer adapted to analyse nitrogen nanomoles. Accurate measurements showed that nitrogen amount released by on-line combustion technique was underestimated to various extents. As a result, the nitrogen isotopic compo...

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