Lipids source and degradation as revealed by molecular biomarkers in soils after acid-pretreatment: A case of a plantain soil under long-term cultivation

The extractable lipids are important components in soil organic matter (SOM) which were used to trace the sources and degradation of SOM. The protection of lipids by soil mineral have been suggested through organic solvents. But, the extraction efficiency of some lipid compounds was low. This study applied a mild acid treatment to firstly remove most of the reactive mineral particles, and without altering SOM chemical structures in 10% HF/1M HCl (1:4 w: v). Based on the obtained lipid biomarker information, we observed that the lipid extraction efficiency significantly increased by organic solvents on after removal of active minerals. The acid treatment increased the scientific to quantitative the amount of lipids. The minerals showed significant differences in the selective protection to different components of lipids. In this study, the amount range of protected n-alkanoic acids is 73~85%, n-alkanol 41~62% and n-alkanes 26~46%. After the vegetation was replaced, the increased alkenoate and alkane in soil input by the plant tissues of plantain directly, and the alkanols probably input by the hydrolysis of wax esters. Under the interference of man-made tillage activities, the C content in 0-20 cm decreased, suggesting that cultivated activities may enhance SOM degradation and accelerate SOM turnover. Understanding SOM behaviour in this area will provide important information for soil management and to evaluate carbon cycling in human-affected ecological systems.