Compound specific delta D values of long chain n-alkanes derived from terrestrial higher plants are indicative of the delta D of meteoric waters: Evidence from surface soils in eastern China

摘要

The stable carbon and hydrogen isotope composition of higher plant-derived long chain n-alkanes delta C-13(n-alkanes) and delta Dn-alkanes) from 45 surface soil samples (within well characterized vegetation zones) from eastern China (18 degrees N-50 degrees N) are reported. The weighted average delta Dn-alkanes value for n-C-27, n-C-29 and n-C-31 in the samples and the annual average delta D of meteoric water recorded at 12 weather stations proximal to the sampling sites show similar spatial variations. The delta D of n-alkanes shows a gradual depletion in value with increasing latitude. The results demonstrate that, on a large spatial scale, the delta D values of long chain n-alkanes derived from higher plants have the potential to record the delta D of meteoric water, although many other factors can also influence the isotope Values. There appears to be no apparent relationship between the delta D of the n-alkanes extracted from the surface soil and the overlying vegetation type (i.e. forest/grassland or C-3/C-4 composition). Therefore, palaeoenvironmental studies utilizing delta Dn-alkanes from higher plant-derived material in geological samples have the potential to provide additional information with regard to the past hydrological cycle.