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To investigate characteristics of H isotope variation in long-chain n-alkanes (δDn-alkanes) from higher plants in surface soils under a single ecosystem, 12 samples from a basalt regolith were randomly collected from Damaping in Wanquan County of Zhangjiakou in North China. Molecular distribution and C (δ13Cn-alkanes) and H isotopes of long-chain n-alkanes, as well as C isotopes of TOC (δ13CTOC), were analyzed. Both δ13CTOC and δ13Cn-alkanes values from four representative dominant long-chain n-alkanes (n-C27, n-C29, n-C31, n-C33) derived from terrestrial higher plants show minor variations among the 12 samples, indicating the major contributor is from local grasses with a uniform C3 photosynthetic pathway. In contrast, variations in δDn-alkanes values of the four long-chain n-alkanes are relatively large, with the more abundant homologs generally showing more negative δDn-alkanes values and less variation. However, variation of <30‰ among weighted averaged δDn-alkanes values of the four long-chain n-alkanes is not only less than that among δDn-alkanes values for different modern terrestrial C3 grasses from the specific locations, but also less than the literature values of δDn-alkanes of long-chain n-alkanes for single species over different seasons. Thus, because the sources of long-chain n-alkanes in surface soils and sediments are similarly from multiple individual plants, our results are significant in confirming that paleoclimatic, paleoenvironmental and paleohydrological information can be interpreted more accurately from δDn-alkanes values of long-chain n-alkanes from sediments, particularly terrestrial sediments with organic matter derived from in-situ plants.
To investigate characteristics of H isotope variation in long-chain n-alkanes (δDn-alkanes) from higher plants in surface soils under a single ecosystem, 12 samples from a basalt regolith were optionally collected from Damaping in Wanquan County of Zhangjiakou in North China. Both δ13CTOC and δ13Cn-alkanes values from four representative dominant long-chain n-alkanes, both δ13Cn-alkanes and H isotopes of long-chain n-alkanes, were analyzed as both C isotopes of TOC (δ13CTOC) alkanes (n-C27, n-C29, n-C31, n-C33) derived from terrestrial higher plants show minor variations among the 12 samples, indicating the major contributor is from local grasses with a uniform C3 photosynthetic pathway. In contrast, variations In δDn-alkanes values of the four long-chain n-alkanes are more large, with the more abundant homologs generally showing more negative δDn-alkanes values and less variation. However, the variation of <30 ‰ among weighted averaged δDn-alkanes values of the four long-chain n-alkanes is not only less than that among δDn-alkanes values for different modern terrestrial C3 grasses from the specific locations, but also less than the literature values of δDn-alkanes of long-chain n-alkanes for single species over different seasons. Thus, because the sources of long-chain n-alkanes in surface soils and sediments are similarly from multiple individual plants, our results are significant in confirming that paleoclimatic, paleoenvironmental and paleohydrological information can be more accurately from δDn -alkanes values of long-chain n-alkanes from sediments, particularly terrestrial sediments with organic matter derived from in-situ plants.