Individual hydrocarbons identified to be macrocyclic alkanes in a torbanite from the Sydney Basin(Australia)were successfully isolated from its extracts using preparative gas chromatography and analyzed by NMR.Saturat...Individual hydrocarbons identified to be macrocyclic alkanes in a torbanite from the Sydney Basin(Australia)were successfully isolated from its extracts using preparative gas chromatography and analyzed by NMR.Saturated cyclic structures were confirmed by single peaks in the NMR~1H and~(13)C spectra indicating single forms of H and C atoms exist in these biomarker molecules.This is consistent with the methylene unit in a ring system assignment of the macrocyclic alkanes and accounts for a formula of(CH2)n.The unusual molecular structures of these compounds are consistent with those that were identified from previous GC retention index data and co-injection with a standard supports the previous research.The mass spectral fragmentation behaviors of representative cyclic alkanes were further investigated by comparing them with the mass spectra of isolated individual macrocyclic alkanes.The characteristic fragment ions in the macrocyclic alkanes of(M–28)+and base peaks of m/z 97,111,125,etc.,can be assigned as being generated by simple a-/i-cleavage and hydrogen rearrangement.These fragmentation pathways combined with retention indices should assist in differentiating these compounds from monounsaturated alkenes and alkylated monocyclics having similar mass spectral characteristics in other geological samples.展开更多
The long-chain alkenones present in the shallow sediment of Hotong Qagan Nur Lake in China are reported. According to the similarity of compositions and distributions of the alkenones determined commonly in the sedime...The long-chain alkenones present in the shallow sediment of Hotong Qagan Nur Lake in China are reported. According to the similarity of compositions and distributions of the alkenones determined commonly in the sediment section to those of marine sediment, it is reasonably referred that the alkenones might also originate from Prymnesiophyceae. ln addition, the parameter U<sub>37</sub><sup>k</sup>＇of alkenone is in positive correlation to δ<sup>18</sup>O values of authigenic calcium and magnesium minerals. This indicates that the parameter U<sub>37</sub><sup>k</sup>＇of long-chain alkenone is also available to indicate paleoclimate of high-salinity alkaline lake.展开更多
Core 17962 taken from the sea area of the Nansha Islands recorded a sedimentary history of more than 30 000 years. The black carbon data from the core, which can inform us of the history of vegetation fires, show that...Core 17962 taken from the sea area of the Nansha Islands recorded a sedimentary history of more than 30 000 years. The black carbon data from the core, which can inform us of the history of vegetation fires, show that during the last glaciation, especially during the last glacial maximum at about 18 kaBP, the fluctuation of the concentration and accumulation rate of the black carbon was relatively great, whereas it was small during the Holocene. The isotope composition of the black carbon indicates that the precursors of black carbon were mainly grasses from the last glaciation to the Holocene. The sub-alpine and alpine vegetation zones covered mainly with grass and bush on the lands around the southern South China Sea were probably the sources of black carbon. The altitudinal vegetation changes from the last glaciation to the Holocene gave rise to the changes of the sedimentary characteristics of black carbon.展开更多
The late progress of the research on Precambrian organic matter in biomarkers, isotopes and relative analytical techniques is reviewed. The key problems in the research of Precambrian organic matter, such as indigenou...The late progress of the research on Precambrian organic matter in biomarkers, isotopes and relative analytical techniques is reviewed. The key problems in the research of Precambrian organic matter, such as indigenous test of soluble organic matter, are also discussed. At the end, the further work upon Precambrian organic matter is suggested.展开更多
In terms of the individual carbon isotope data of biomarkers present in the typical freshwater lake sediment (Maoming oil shale) and saline lake sediment lake (Jianghan oil shale) of China, this paper discusses their ...In terms of the individual carbon isotope data of biomarkers present in the typical freshwater lake sediment (Maoming oil shale) and saline lake sediment lake (Jianghan oil shale) of China, this paper discusses their precursors and depositional environments of biomarkers in both sediment samples. Our studies showed that phytane and pristane of the Maoming oil shale were derived from the phytol side chain of chlorophyll a. By comparing the isotopic composition of 4-methyl sterane with that of sterane and hopane, it is suggested that 4-methyl sterane which has a higher abundance in the Maoming oil shale come from bacteria. The isotopic composition of biomarkers from the Jianghan rock sample (saline lake sediment) is significantly different from that of the Maoming oil shale (freshwater lake sediment). Gammacerane was derived from haloprotozoan, with δ13C being about -25.8‰, just in consistency with the value reported in previous studies. The isotopic composition of phytane and pristane in the Jianghan展开更多
Monoterpenes in ambient air were determined in various sites in Guangzhou, and it was revealed that monoterpene concentrations in some special sites, like landfills, were even higher than those in locations with much ...Monoterpenes in ambient air were determined in various sites in Guangzhou, and it was revealed that monoterpene concentrations in some special sites, like landfills, were even higher than those in locations with much more vegetation. On the average, monoterpene contents in samples from streets and highways were 1.9 μg/m3; from gardens, plantations and wooded lands, 2.2 μg/m3; from farmlands, 1.5 μg/m3; but from landfills, 4.1 μg/m3. So other sources like landfills, apart from living plants, might also contribute to the biogenic non-methane hydrocarbons (NMHCs) in the atmospheric environment. On the other hand, the composition pattern of monoterpenes in air samples from landfills were obviously different compared with those from living plants, this might result from the different synthesis pathways of monoterpenes, the oxygen-depleted environment and the microbiogenic process might affect the synthesis in landfills.展开更多
High performance liquid chromatography (HPLC) has the advantages of rapid analysis and high sensitivity. In the present study a suitable analytical condition has been established for HPLC, and the LAS in modern sedime...High performance liquid chromatography (HPLC) has the advantages of rapid analysis and high sensitivity. In the present study a suitable analytical condition has been established for HPLC, and the LAS in modern sediments from core Zhu-9 at the Pearl River mouth has been determined by HPLC. The concentrations of C12-LAS homologues are the highest. The sedimentation flux of C12-LAS was correlated with the average flow of the Xijiang and Beijiang rivers: the higher the flow rate, the larger the C12-LAS sedimentation flux. This shows that the more rapidly the river flows, the shorter the LAS will stay in freshwater, the less the extent of biodegradation, the larger the C12-LAS sedimentation flux in the core Zhu-9.展开更多
Chemical structure of immature sulfur_rich kerogen and composition of immature sulfur_rich crude oil in Jianghan oil field have been studied. In molecular level, crude oil differs from thermolysed and chemolysed produ...Chemical structure of immature sulfur_rich kerogen and composition of immature sulfur_rich crude oil in Jianghan oil field have been studied. In molecular level, crude oil differs from thermolysed and chemolysed products of kerogen but does resemble the bitumen in immature sulfur_rich source rock. Therefore, immature sulfur_rich oil may be derived from the expelling of bitumen rather than from thermal cracking of kerogen.展开更多
基金the financial support from The Strategic Priority Research Program of the Chinese Academy of Sciences(XDA14010102)Chinese National Science Foundation grants(4197306941673045)。
文摘Individual hydrocarbons identified to be macrocyclic alkanes in a torbanite from the Sydney Basin(Australia)were successfully isolated from its extracts using preparative gas chromatography and analyzed by NMR.Saturated cyclic structures were confirmed by single peaks in the NMR~1H and~(13)C spectra indicating single forms of H and C atoms exist in these biomarker molecules.This is consistent with the methylene unit in a ring system assignment of the macrocyclic alkanes and accounts for a formula of(CH2)n.The unusual molecular structures of these compounds are consistent with those that were identified from previous GC retention index data and co-injection with a standard supports the previous research.The mass spectral fragmentation behaviors of representative cyclic alkanes were further investigated by comparing them with the mass spectra of isolated individual macrocyclic alkanes.The characteristic fragment ions in the macrocyclic alkanes of(M–28)+and base peaks of m/z 97,111,125,etc.,can be assigned as being generated by simple a-/i-cleavage and hydrogen rearrangement.These fragmentation pathways combined with retention indices should assist in differentiating these compounds from monounsaturated alkenes and alkylated monocyclics having similar mass spectral characteristics in other geological samples.
文摘The long-chain alkenones present in the shallow sediment of Hotong Qagan Nur Lake in China are reported. According to the similarity of compositions and distributions of the alkenones determined commonly in the sediment section to those of marine sediment, it is reasonably referred that the alkenones might also originate from Prymnesiophyceae. ln addition, the parameter U<sub>37</sub><sup>k</sup>＇of alkenone is in positive correlation to δ<sup>18</sup>O values of authigenic calcium and magnesium minerals. This indicates that the parameter U<sub>37</sub><sup>k</sup>＇of long-chain alkenone is also available to indicate paleoclimate of high-salinity alkaline lake.
文摘Core 17962 taken from the sea area of the Nansha Islands recorded a sedimentary history of more than 30 000 years. The black carbon data from the core, which can inform us of the history of vegetation fires, show that during the last glaciation, especially during the last glacial maximum at about 18 kaBP, the fluctuation of the concentration and accumulation rate of the black carbon was relatively great, whereas it was small during the Holocene. The isotope composition of the black carbon indicates that the precursors of black carbon were mainly grasses from the last glaciation to the Holocene. The sub-alpine and alpine vegetation zones covered mainly with grass and bush on the lands around the southern South China Sea were probably the sources of black carbon. The altitudinal vegetation changes from the last glaciation to the Holocene gave rise to the changes of the sedimentary characteristics of black carbon.
文摘The late progress of the research on Precambrian organic matter in biomarkers, isotopes and relative analytical techniques is reviewed. The key problems in the research of Precambrian organic matter, such as indigenous test of soluble organic matter, are also discussed. At the end, the further work upon Precambrian organic matter is suggested.
文摘In terms of the individual carbon isotope data of biomarkers present in the typical freshwater lake sediment (Maoming oil shale) and saline lake sediment lake (Jianghan oil shale) of China, this paper discusses their precursors and depositional environments of biomarkers in both sediment samples. Our studies showed that phytane and pristane of the Maoming oil shale were derived from the phytol side chain of chlorophyll a. By comparing the isotopic composition of 4-methyl sterane with that of sterane and hopane, it is suggested that 4-methyl sterane which has a higher abundance in the Maoming oil shale come from bacteria. The isotopic composition of biomarkers from the Jianghan rock sample (saline lake sediment) is significantly different from that of the Maoming oil shale (freshwater lake sediment). Gammacerane was derived from haloprotozoan, with δ13C being about -25.8‰, just in consistency with the value reported in previous studies. The isotopic composition of phytane and pristane in the Jianghan
文摘Monoterpenes in ambient air were determined in various sites in Guangzhou, and it was revealed that monoterpene concentrations in some special sites, like landfills, were even higher than those in locations with much more vegetation. On the average, monoterpene contents in samples from streets and highways were 1.9 μg/m3; from gardens, plantations and wooded lands, 2.2 μg/m3; from farmlands, 1.5 μg/m3; but from landfills, 4.1 μg/m3. So other sources like landfills, apart from living plants, might also contribute to the biogenic non-methane hydrocarbons (NMHCs) in the atmospheric environment. On the other hand, the composition pattern of monoterpenes in air samples from landfills were obviously different compared with those from living plants, this might result from the different synthesis pathways of monoterpenes, the oxygen-depleted environment and the microbiogenic process might affect the synthesis in landfills.
文摘High performance liquid chromatography (HPLC) has the advantages of rapid analysis and high sensitivity. In the present study a suitable analytical condition has been established for HPLC, and the LAS in modern sediments from core Zhu-9 at the Pearl River mouth has been determined by HPLC. The concentrations of C12-LAS homologues are the highest. The sedimentation flux of C12-LAS was correlated with the average flow of the Xijiang and Beijiang rivers: the higher the flow rate, the larger the C12-LAS sedimentation flux. This shows that the more rapidly the river flows, the shorter the LAS will stay in freshwater, the less the extent of biodegradation, the larger the C12-LAS sedimentation flux in the core Zhu-9.
文摘Chemical structure of immature sulfur_rich kerogen and composition of immature sulfur_rich crude oil in Jianghan oil field have been studied. In molecular level, crude oil differs from thermolysed and chemolysed products of kerogen but does resemble the bitumen in immature sulfur_rich source rock. Therefore, immature sulfur_rich oil may be derived from the expelling of bitumen rather than from thermal cracking of kerogen.
