摘要
利用GC-MS对红原泥炭样品中的分子化石进行了系统检测,获得了一系列正构烯烃,碳数分布范围为C18—C28,主峰碳为C27,次主峰为C23或C25,与同一深度处的正构烷烃分布模式完全不同。泥炭中正构烯烃的轻重组分∑C21-/∑C2+1、正构烯烃与相应碳数的正构烷烃比值呈有意义的阶段性变化。其中∑C21-/∑C21+与正构烷烃L/H的变化趋势大体一致;而C24:1/C24:0和C23:1/C23:0比值却与之相反。这可能与正构烯烃,特别是这些中碳数化合物因气候如温度的变化在厌氧条件下发生微生物的氢化作用有关,很可能记录了青藏高原东北部地区全新世以来的温度信号。(C26+C27+C28)/(C23+C24+C25)正构烯烃比值,与该区植被分布具有一定的对应关系,说明这些正构烯烃可能除了与植被有关外,也与不同植被类型的组织具有不同抗微生物降解能力相关。这些指标记录的气候信息与前期报道的分子化石记录的气候演化基本一致,说明正构烯烃可以作为古气候的替代性指标。
This peat sedimentary sequence was systematically investigated with lipid molecular stratigraphy by gas chromatography-mass spectrometer （GC-MS）. A variety of molecular fossils are found in this peat profile, including n-alkanes, n-alkanols and n-fatty acids and so on. The n-alkenes are from C18to C28, hav- ing a maximum at C27, with s second dominance at C23 or C2s. In contrast to the n-alkenes analysed, the n- alkanes are characterized by the dominance of heavy-molecular-weight homologues （〉 C22） at the same depth. According to the analysis, we found the high carbon number n-alkenes possibly are mainly derived from higher plants, while algae and microorganisms are secondly. The ratios of low molecular number to high molecular number n-alkenes（∑C21-/∑C21 ＋） and the ratios of n-alkenes to the corresponding carbon number n-alkanes such as C24,1/C24,0 and C23,1/C23,0 show the regular variations. ∑ C21-/∑ C21 ＋ has the same trend as the ratios of low molecular number to high molecular number n-alkanes （L/H-ALK） on the whole; on the contrary, C24,1/C24,0 and C23,1/C23,0 have an opposite trend. These results indicate n-alkenes especially these middle carbon number n-alkenes give microbial hydrogenation under the reductive condition resulting from the climatic change such as temperature. The results show n-alkenes proxies seem to bear significant climate information and possibly indicate temperature changes in the northeastern Qinghai-Tibet Plateau during the Holocene. In addition, （C26 ＋C27 ＋C28）/（C23＋C24 ＋C25） n-alkene ratios display a defi- nite corresponding relationship with the vegetation in the region, possibly suggesting these n-alkenes not only have a relationship with the vegetation, but also are capable of microbial degradation of different vege- tation species . Climatic information from these n-alkens proxies is consistent with previous paleoclimate signals extracted from n-alkanes, n-alkanols and n-fatty acids of the same peat profile. These indicate n-al- kenes proxies can be an important proxy for studying the paleoelimate and global change.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
2008年第5期123-128,共6页
Marine Geology & Quaternary Geology
基金
国家自然科学基金项目(440602004)
国家重点基础研究规划项目(2004CB720200)
关键词
泥炭
正构烯烃
古气候意义
全新世
peat
n-alkenes
paleoclimatic implication
the Holocene
