中文摘要：

通过对陕西洛南刘湾剖面黄土-古土壤类脂物正构烷烃组分进行超声波和加速溶剂萃取方法比较发现：在增加振荡频率（100 Hz）的条件下,对3个相同质量的同一表土样品分别超声提取1、2、3遍和采用有机溶剂浸泡过夜在较低振荡频率（60 Hz）条件下超声抽提3遍获取的正构烷烃组分分布相同,相对丰度差异较小;刘湾剖面7个古土壤样品超声波溶剂萃取获得的正构烷烃组分相对丰度较低,且随深度增加,呈现逐渐降低的趋势;超声波溶剂萃取的两个样品碳优势指数（CPI）分别为5.4和4.6,碳同位素值分别为-31.80‰和-30.52‰;加速溶剂萃取的相同样品CPI值分别为5.3和4.3,碳同位素值分别为-31.46‰和-30.56‰。两种方法萃取的土壤正构烷烃组分分布相同;但加速溶剂萃取的正构烷烃相对丰度是超声波溶剂萃取的0.9~1.5倍。结果表明超声波溶剂萃取的次数和强度不会对其抽提效率产生明显影响;对于年代较老、有机质含量较低的刘湾剖面古土壤样品,超声波溶剂萃取的效率较低;两种处理方法获得的类脂物正构烷烃组分分布和碳同位素值没有差别,但是超声波溶剂萃取的效率明显低于加速溶剂萃取的效率。因此,对于年代较老、含量较低的地质样品,采用加速溶剂萃取方法更有助于获得充分的样品量并进行可靠的气相色谱-燃烧-同位素比值分析;对于现代样品和含量较高的地质样品,采用设备相对便宜、操作简单、易于实现的超声波溶剂萃取方法即可。

英文摘要：

Two extraction methods,ultrasonic-assisted solvent extraction（UASE） and accelerated solvent extraction（ASE）,were used to study the distribution characteristics of n-alkanes in loess-paleosol lipids.A suite of loess-paleosol lipid samples were collected from Liuwan profile located in Luonan county,Shaanxi province.The results showed that no significant differences for the distribution pattern and relative abundance of n-alkanes were observed when using UASE either increasing the ultrasonic frequency to 100 Hz or tripling the extraction times under ultrasonic frequency of 60 Hz.The n-alkane abundance in 7 paleosol samples from Liuwan profile is rather low when UASE is used and increasing with depth of the profile.The carbon preference index（CPI） of n-alkanes for 2 paleosol samples extracted with UASE were 5.4 and 4.6 with isotopic composition（average value） of-31.80‰ and-30.52‰.CPI of n-alkanes from the same samples extracted with ASE was 5.3 and 4.3 with isotopic composition of-31.46‰ and-30.56‰.The results showed that there is no significant difference in selectivity between UASE and ASE,but ASE is more efficient in extracting n-alkanes from paleosols than UASE.For geologically older loess-paleosol samples with lower content of n-alkanes,ASE is obviously a preferable extraction method with better recovery of n-alkanes for further compositional and isotopic analysis.While for geologically younger samples with higher organic content,UASE seems a preferable extraction method with advantages of less expensive and easier-to-operation.