Carbon isotopic characteristics and their genetic relationships for individual lipids in plants and sediments from a marsh sedimentary environment

Abstract

The carbon isotopes of individual lipids in herbaceous plants and tree leaves in Ruoergai marsh were measured by the GC-IRMS analytical technique in order to understand the inherent relationships of carbon isotopes between sedimentary and plant lipids from typical marsh environment. The analytical results show that the carbon isotopic compositions of n-alkanes in different kinds of plants differ significantly. Mean d 13C values of n -alkanes in herbaceous plants (-32.2‰― −36.9‰) are 3.3‰ lower than those in woody plant ( −27.2‰― −35.0‰). The carbon isotopic compositions of fatty acids in organisms ( −30.3‰― −36.2‰) are very similar to those of n -alkanes and the δ 13 C values for unsaturated fatty acids are within the range of those for satu-rated fatty acids. The differences in δ 13 C values between plant lipids are obvious and range from 2.4‰ to 7.8‰. It is observed that the carbon isotopic compositions of sedimentary lipids are closely related to those of plant lipids. The carbon isotopic compositions ( −27.0‰― −36.9‰) of n-alkanes, ≥C 16 fatty acids, n -alkanols, sterols and n-alkanones in the sediments are similar to those of plant lipids and the carbon isotopic compositions of short-chain sedimentary lipids are similar to those of long-chain sedimentary homologues. These indicate that the sedimentary lipids are derived from high plants. However, the δ 13 C values of C 14:0 and C 15:0 fatty acids in the sediments are lighter than those of the same carbon number saturated homologues in plants, reflecting the genetic features partially derived from bacteria. These data provide scientific evidence for carbon isotope-applied research of individual lipids.