The carbon isotopic composition of alkenes from loess-paleosol sequences in China Loess was measured by pyrolysis/gas chromatography/isotopic ratio mass spectrometry.Thermochemolysis products of the insoluble residues...The carbon isotopic composition of alkenes from loess-paleosol sequences in China Loess was measured by pyrolysis/gas chromatography/isotopic ratio mass spectrometry.Thermochemolysis products of the insoluble residues were characterized using GC/MS,and they are derived mainly from aliphatic hydrocarbons.The dominant aliphatic compounds are n-alkenes that range from C9 to C17 for the loess samples.Fluctuations in the carbon isotopic composition of the Xifeng loess-paleosol profile,range from-27‰to-18.5‰for the past 40 ka.δ^13C values in colder climates(last glacial)are characterized by depleting inδ^13C by approximately 3‰relative to those in warmer climates(deglacial and Holocene).This suggests that the temporal variations ofδ^13C values for alkenes from plants cutin exhibit a close relationship with glacial-interglacial cycles.The result is also closely consistent with that from total organic carbon in the same loess-paleosol profile.展开更多
文摘The carbon isotopic composition of alkenes from loess-paleosol sequences in China Loess was measured by pyrolysis/gas chromatography/isotopic ratio mass spectrometry.Thermochemolysis products of the insoluble residues were characterized using GC/MS,and they are derived mainly from aliphatic hydrocarbons.The dominant aliphatic compounds are n-alkenes that range from C9 to C17 for the loess samples.Fluctuations in the carbon isotopic composition of the Xifeng loess-paleosol profile,range from-27‰to-18.5‰for the past 40 ka.δ^13C values in colder climates(last glacial)are characterized by depleting inδ^13C by approximately 3‰relative to those in warmer climates(deglacial and Holocene).This suggests that the temporal variations ofδ^13C values for alkenes from plants cutin exhibit a close relationship with glacial-interglacial cycles.The result is also closely consistent with that from total organic carbon in the same loess-paleosol profile.
