Distributions of fatty acids in a stalagmite related to paleoclimate change at Qingjiang in Hubei, southern China
Fatty acids extracted from a subtropical stalagmite at Qingjiang in Southern China's Hubei Province were analysed using gas chromatography-mass spectrometry. These n-alkanoic acids range from C14 to C26 in carbon number, maximizing at C16, with a second dominance at C22. In contrast to the stalagmite analysed, the overlying soils are characterized by the dominance of heavy-molecular-weight homologues (＞C20). The n-fatty acids in the stalagmite were proposed to be contributed by both the soil ecosystems and the microbes harboring in the percolating water and the cave. The ratios of unsaturated to saturated n-fatty acids (C16:1/C16:0,C18:1/C18:0) appear to show trends comparable with the oxygen isotope records of the stalagmite carbonate, with enhanced values associated with the cold episode such as Heinrich event 1. This paleoclimate-dependent record of the n-fatty acids might reflect microbial changes in physiology and activity in response to the temperature. This record shows somewhat difference from the previous paleoclimate signal extracted from n-alkanols and n-alkan-2-ones of the same stalagmite. The acid record fails to document the well-known Younger Dryas event which was effectively shown by the latter two biomarkers derived from soil ecosystems. This discrepancy might result from the changing biogeochemical impact on different lipid fractions as well as the varied organism populations in different ecosystems.
作 者： XIE Shucheng HUANG Junhua WANG Hongmei YI Yi HU Chaoyong CAI Yanjun CHENG Hai 作者单位： XIE Shucheng,HUANG Junhua,YI Yi,HU Chaoyong(Faculty of Earth Science, China University of Geosciences, Wuhan 430074, China)WANG Hongmei(School of Environmental Studies, China University of Geosciences, Wuhan 430074, China)
CAI Yanjun(SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710075, China)
CHENG Hai(Department of Geology and Geophysics, University of Minnesota, MN55455, USA)
刊 名： 中国科学D辑(英文版) SCI 英文刊名： SCIENCE IN CHINA (EARTH SCIENCES) 年，卷(期)： 2005 48(9) 分类号： P3 关键词： biomarker ecosystem microbe speleothem paleoclimate Quaternary