Hydrogen isotopic compositions and their environmental significance for individual n-alkanes in typical plants from land in China |
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Authors: | Yi Duan BaoXiang Wu |
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Institution: | (1) Chinese Academy of Sciences, Institute of Geology and Geophysics, Lanzhou, 730000, China |
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Abstract: | Hydrogen isotopes of n-alkanes in grasses, tree leaves and reeds from six regions with latitudes of 20° to 39°N in China are measured by GC-TC-IRMS
analytical technique in order to understand their hydrogen isotopic compositions and environmental significance. The results
show that a difference in ° D values (from −42.1‰ to −66.6‰) of n-alkanes exists among the same kinds of plants from various regions. Hydrogen isotopic compositions of most even carbon numbered
n-alkanes in every plant are slightly heavier than that of the odd homologues. A trend toward D-enrichment with increasing
chain length of n-alkanes in most plant samples is observed. Mean ° D values of n-alkanes in the studied plants range from −202.6‰ to −130.7‰ and the reed from a salt marsh has the largest value. The mean
° D values of individual n-alkanes among the same kinds of plants from various regions have the characteristics of leaf > reed > grass. The hydrogen
isotopic compositions of n-alkanes are apparently distinct among various kinds of plants from the same region and the mean ° D values exhibit a distribution
of tree leaf > reed > grass. It is observed that the mean ° D values of n-alkanes and ° D values of C27 and C29
n-alkanes in the grasses and tree leaves from these studied regions correlate clearly negatively with latitude and positively
with temperature, indicating that these values can be used as excellent indicators of environment and climate. These results
provide important basic data for understanding the distributional law of hydrogen isotopes of individual n-alkanes and their applied research.
Supported by National Natural Science Foundation of China (Grant Nos. 40642007 and 40772069), National Basic Research Program
of China (Grant No. 2005CB422105) and Special Project for Winners of CAS President Award |
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Keywords: | plant individual n-alkane hydrogen isotopic composition and distribution environmental index |
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