Variation in Solvent-Extractable Lipids and n-Alkane Compound-Specific Carbon Isotopic Compositions with Depth in a Southern China Karst Area Soil

• Published in: Journal of earth science (Wuhan, China) China), 2010 (4), p.382-391
• Main Author: Cui Jingwei Huang Junhua Philip A Meyers Huang Xianyu Li Jingjing Liu Wengui
• Format: Article
• Language: Chinese
• Subjects: 中国南方; 喀斯特地区; 正构烷烃; 溶剂萃取; 烃化合物; 现代土壤; 碳同位素组成; 血脂
• ISSN: 1674-487X; 1867-111X

Because literatures about the lipid compositions of modern soils in karst areas are scarce, we have studied the soil horizons overlying the Heshang （和尚） Cave that has provided paleoclimate records from speleothem lipid contents. Our analysis reveals a series of n-alkanes, free fatty acids, n-alkanols and n-alkan-2-ones distribution and relative abundance changing with the depth, and in which the ratios of the lower molecular weight to higher molecular weight n-alkanes, free fatty acids, n-alkanols and n-alkan-2-ones have a peak at a subsurface depth of 5 to 10 cm. An accompanying peakin 17β（H）, 21β（H）-hop-22（29）-ene （diploptene） and a shift to less negative n-alkane carbon isotopic values also identify this layer in the karst soil. This pattern indicates the existence of a subsurface soil layer in which the microorgan- isms that produce these compounds are espe- cially abundant. The carbon isotopic values of individual plant wax n-alkanes are about 3%0 greater at the base of the 30- to 40-cm soil profile than