碱式水解法提取红土分子化石:以安徽宣城更新世网纹红土为例

An Optimized Alkaline Hydrolysis Method to Extract Lipid Biomarkers from Pleistocene Vermicular Red Paleosols:An Example from Xuancheng,Anhui Province

红土中种类丰富的分子化石为红土古生态研究提供了直接证据,但较低含量的分子化石限制了传统索氏抽提方法的推广应用.本次研究尝试性地运用碱式水解法提取安徽宣城更新世红土中的分子化石,在25g样品中检测到了含量明显、种类丰富的有机物,且该方法可以显著地降低空白污染,这说明碱式水解法在分子化石含量低的地质体(如红土)研究中具有一定的应用潜力.本次研究检测出除了传统索式抽提得到的正构烷烃、脂肪酸、脂肪醇等以外,还提取到了二元羧酸这一重要化合物,它的存在为网纹红土可能形成于多水环境提供了新的证据.测试样品中各类分子化石组合信息显示出红土有机物以微生物为主的来源特征,表明网纹红土形成过程受到了微生物活动的影响,同时伴有大量低等菌、藻来源有机质的输入,初步结果为红土形成环境研究提供了新的证据.

Variety of molecular fossils in red paleosols can provide direct evidence for paleoecological origin of red paleosols, but the popularization and application of the traditional Soxhlet extraction are limited by low content of molecular fossils in vermicular red paleosols. The alkaline hydrolytic method is tentatively employed to extract lipids from Pleistocene vermicular red paleosols in Xuancheng, Anhui Province. Relatively high content and variety of organics have been detected in two samples with weight of 25 g, respectively. The effect of pollution reducing is also obvious in contrast to Soxhlet extraction, which will be potential for the research on some geological sediment with low content of organic matter （such as red paleosols）. A new kind of lipid biomarker named as dicarboxyl acids is firstly found in red paleosols due to alkaline hydrolytic method. In addition, other compounds extracted by traditional Soxhlet extraction such as n-alkanes, fatty acids, n-alkanols are also detected. The occur- rence of dicarboxyl acids has put new insight into understanding that red paleosols is possibly developed under excessively humid condition. Distribution pattern of molecular fossils in testing samples demonstrates that the organics of red paleosols mainly originate from microbe and shows that the formation of red paleosols is affected by microbial activities with lots of oganic matter from lower bacteria and algae. The results of our preliminary studying have provided new evidence for the research on the formation environment of red paleosols.