Acyclic Alkanes in the Soil over Heshang Cave in Qingjiang, Hubei Province

The reports that relate to the biomarker's fate and characteristics of the modern soil in the karst area are very lacking. By using gas chromatography-mass spectrometry (GC-MS), a series of biomarkers were identified from the soils collected over Heshang cave () in Qingjiang (), Hubei () Province. The distribution of n-alkanes is mainly from C25 to C33 in carbon number, with a maximum at C31. They have a strong odd-over-even carbon number predominance. These characteristics represent an input mainly from higher plants. The lipid parameters, including CPIh (carbon preference index), Rh/1 (ratio of lower-to higher-molecular-weight homologues) and ACL (average chain length), show comparable trends with depth, probably reflecting vegetation change and microbial degradation. Series of monomethylalkanes and diploptene are present in the extractable organic matter; they might be derived from soil microbes, cyanobacteria in particular.