McDuffee, Kelsey E. and Eglinton, Timothy I. and Sessions, Alex L. and Sylva, Sean and Wagner, Thomas and Hayes, John M. (2004) Rapid analysis of 13C in plant-wax n-alkanes for reconstruction of terrestrial vegetation signals from aquatic sediments. Geochemistry, Geophysics, Geosystems, 5 (10). 2004GC000772. ISSN 1525-2027 http://resolver.caltech.edu/CaltechAUTHORS:MCDggg04
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Long-chain, odd-carbon-numbered C25 to C35 n-alkanes are characteristic components of epicuticular waxes produced by terrestrial higher plants. They are delivered to aquatic systems via eolian and fluvial transport and are preserved in underlying sediments. The isotopic compositions of these products can serve as records of past vegetation. We have developed a rapid method for stable carbon isotopic analyses of total plant-wax n-alkanes using a novel, moving-wire system coupled to an isotope-ratio mass spectrometer (MW-irMS). The n-alkane fractions are prepared from sediment samples by (1) saponification and extraction with organic solvents, (2) chromatographic separation using silica gel, (3) isolation of straight-chain carbon skeletons using a zeolite molecular sieve, and (4) oxidation and removal of unsaturated hydrocarbons with RuO4. Short-chain n-alkanes of nonvascular plant origin (<C25) are removed by evaporation on the moving wire. Test samples processed using this procedure yielded n-alkane fractions essentially free of interfering components. The δ13C values obtained by MW-irMS did not differ significantly from weighted averages of individual n-alkane δ13C values obtained by irmGC-MS. Isotopic variations in compound-class n-alkane fractions from a latitudinal transect of core-top sediments from the Southwest African margin (3°N–28°S) were congruent with those measured by compound-specific isotopic analyses of plant-wax n-alkanes. The amplitude of the variations was smaller, indicating contributions from non-plant-wax hydrocarbons, but the measurements revealed variations in carbon isotopic composition that are consistent with vegetation zones on the adjacent continent.
|Additional Information:||Copyright 2004 by the American Geophysical Union. Received: 10 June 2004; Revised: 11 August 2004; Accepted: 16 August 2004; Published: 15 October 2004. We thank Daniel Montluçon for technical support, Carl Johnson for the irmGC-MS analyses, Guillemette Ménot-Combes for help with MW-irMS measurements, and the WHOI Summer Student Fellow program and NSF (BCS-0218511) for funding.|
|Subject Keywords:||moving wire; plant-wax n-alkanes; stable carbon isotopes; 4850 Oceanography: Biological and Chemical: Organic marine chemistry; 4894 Oceanography: Biological and Chemical: Instruments and techniques|
|Official Citation:||McDuffee, K. E., T. I. Eglinton, A. L. Sessions, S. Sylva, T. Wagner, and J. M. Hayes (2004), Rapid analysis of 13C in plant-wax n-alkanes for reconstruction of terrestrial vegetation signals from aquatic sediments, Geochem. Geophys. Geosyst., 5, Q10004, doi:10.1029/2004GC000772.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Archive Administrator|
|Deposited On:||19 Dec 2005|
|Last Modified:||26 Dec 2012 08:42|
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