Glycerol dialkyl glycerol tetraethers(GDGTs), specific membrane lipids synthesized mainly by bacteria and archaea, can be divided into isoprenoids and methyl branched alkyl GDGTs(i GDGTs and brGDGTs, respectively). Th...Glycerol dialkyl glycerol tetraethers(GDGTs), specific membrane lipids synthesized mainly by bacteria and archaea, can be divided into isoprenoids and methyl branched alkyl GDGTs(i GDGTs and brGDGTs, respectively). Three GDGTs groups(i GDGTs, brGDGTs, and other membrane lipids) in a peat sample were separated and collected in this study using semi-preparative high-performance liquid chromatography(HPLC) and silica gel column chromatography. The obtained recoveries for the whole analytical procedure were 85% – 55% using semi-preparative HPLC and 70% – 20% using gel column chromatography. In addition, in each method, the recoveries of brGDGTs and iGDGTs were similar, regardless of the huge difference in their contents. High purity was found in the fractionated groups, determined based on ether cleavage and reduction. Moreover, the semi-preparative HPLC method could realize a better separation efficiency than the silica gel method, but it was time-consuming and required expensive equipment, while the silica gel chromatography method featured merits of time saving and convenient operation at the cost of a slight reduction in separation efficiency. The advantages of the silica gel method make it an operational laboratory method for batch experiments and isotopic studies.展开更多
We present a quantitative mean annual air temperature(MAAT)record spanning the past 4700 years based on the analysis of branched glycerol dialkyl glycerol tetraethers(brGDGTs)from a sediment core from Xiada Co,an alpi...We present a quantitative mean annual air temperature(MAAT)record spanning the past 4700 years based on the analysis of branched glycerol dialkyl glycerol tetraethers(brGDGTs)from a sediment core from Xiada Co,an alpine lake on the western Tibetan Plateau(TP).The record indicates a relatively stable and warm MAAT until 2200 cal yr BP;subsequently,the MAAT decreased by~4.4℃ at~2100 cal yr BP and maintained a cooling trend until the present day,with centennial-scale oscillations centered at~800 cal yr BP,~600 cal yr BP,and~190-170 cal yr BP.MAAT decreased abruptly at~500-300 cal yr BP and reached its minimum for the past 4700 years.We assessed the representativeness of our record by comparing it with 15 published paleotemperature records from the TP spanning the past~5000 years.The results show divergent temperature variations,including a gradual cooling trend,a warming trend,and no clear trend.We suggest that these discrepancies could be caused by factors such as the seasonality of the temperature proxies,the length of the freezing season of the lakes,the choice of proxy-temperature calibrations,and chronological errors.Our results highlight the need for more high-quality paleotemperature reconstructions with unambiguous climatic significance,clear seasonality,site-specific calibration,and robust dating,to better understand the processes,trends,and mechanisms of Holocene temperature changes on the TP.展开更多
青海湖晚第四纪的古环境演化和湖面变化是学术界长期关注的热点问题，争议也较多。我们对青海湖地区种羊场（ZYC）剖面（120 cm厚）全新世风尘堆积的GDGTs （甘油二烷基甘油四醚）化合物相关指标的古环境意义进行了初步研究，以期从一...青海湖晚第四纪的古环境演化和湖面变化是学术界长期关注的热点问题，争议也较多。我们对青海湖地区种羊场（ZYC）剖面（120 cm厚）全新世风尘堆积的GDGTs （甘油二烷基甘油四醚）化合物相关指标的古环境意义进行了初步研究，以期从一个新的角度对上述问题进行探讨。研究结果表明：1） ZYC剖面的TEX86（由86个碳原子组成的四醚指标）与磁化率正相关，而Ri/b比值（类异戊二烯GDGTs与支链GDGTs丰度的比值）与磁化率负相关。2） ZYC剖面的TEX86指标与湖泊岩芯胖真星介（Eucypris inflata）壳体δ18O指示的7月古水温及长链烯酮（U37K）指示的夏季古水温变化具有相似的变化特征，显示TEX86指标较可靠地指示了青海湖地区的大气温度变化。然而，ZYC剖面的MBT （甲基化指数）和CBT （环化指数）指标在重建古气温方面具有一定的局限性，可能与青海湖地区全新世出现的干旱环境有关。3） ZYC剖面的Ri/b比值与湖泊岩芯E.inflata壳体Sr/Ca比值指示的青海湖湖水的古盐度具有较一致的变化特征，表明Ri/b比值较有效地指示了青海湖地区环境的干湿状况。4） TEX86和Ri/b指标揭示青海湖区在9.5~7.5 ka B.P.为冷干时期；7.5~5.5 ka B.P.为独特的温干阶段，温度在6.2 ka B.P.左右达到最高值；5.5~1.7 ka B.P.为温湿时期；1.7~0 ka B.P.为冷干时期。5）风尘堆积的GDGTs记录表明：7.5~5.5 ka B.P.由于环境干旱，青海湖不太可能出现高湖面；5.5~1.7 ka B.P.由于环境湿润，青海湖很可能出现全新世高湖面；1.7 ka B.P.以来，青海湖地区的气候快速变干。展开更多
基金supported by the National Natural Science Foundation of China (Nos. 41673042,41876042,and 41776049)。
文摘Glycerol dialkyl glycerol tetraethers(GDGTs), specific membrane lipids synthesized mainly by bacteria and archaea, can be divided into isoprenoids and methyl branched alkyl GDGTs(i GDGTs and brGDGTs, respectively). Three GDGTs groups(i GDGTs, brGDGTs, and other membrane lipids) in a peat sample were separated and collected in this study using semi-preparative high-performance liquid chromatography(HPLC) and silica gel column chromatography. The obtained recoveries for the whole analytical procedure were 85% – 55% using semi-preparative HPLC and 70% – 20% using gel column chromatography. In addition, in each method, the recoveries of brGDGTs and iGDGTs were similar, regardless of the huge difference in their contents. High purity was found in the fractionated groups, determined based on ether cleavage and reduction. Moreover, the semi-preparative HPLC method could realize a better separation efficiency than the silica gel method, but it was time-consuming and required expensive equipment, while the silica gel chromatography method featured merits of time saving and convenient operation at the cost of a slight reduction in separation efficiency. The advantages of the silica gel method make it an operational laboratory method for batch experiments and isotopic studies.
基金financially supported by the National Natural Science Foundation of China(Grant No.41901105)the Research and Practice Project of Teaching Reform in universities of Henan Province(No.2022SYJXLX062)+2 种基金the Key Scientific and Technological Research Project of Henan Province(No.222102320128)the Training Plan of young backbone teachers in Henan Colleges and universities(Nos.2020GGJS158,2023GGJS096)the Nanhu Scholars Program for Young Scholars of XYNU.
文摘We present a quantitative mean annual air temperature(MAAT)record spanning the past 4700 years based on the analysis of branched glycerol dialkyl glycerol tetraethers(brGDGTs)from a sediment core from Xiada Co,an alpine lake on the western Tibetan Plateau(TP).The record indicates a relatively stable and warm MAAT until 2200 cal yr BP;subsequently,the MAAT decreased by~4.4℃ at~2100 cal yr BP and maintained a cooling trend until the present day,with centennial-scale oscillations centered at~800 cal yr BP,~600 cal yr BP,and~190-170 cal yr BP.MAAT decreased abruptly at~500-300 cal yr BP and reached its minimum for the past 4700 years.We assessed the representativeness of our record by comparing it with 15 published paleotemperature records from the TP spanning the past~5000 years.The results show divergent temperature variations,including a gradual cooling trend,a warming trend,and no clear trend.We suggest that these discrepancies could be caused by factors such as the seasonality of the temperature proxies,the length of the freezing season of the lakes,the choice of proxy-temperature calibrations,and chronological errors.Our results highlight the need for more high-quality paleotemperature reconstructions with unambiguous climatic significance,clear seasonality,site-specific calibration,and robust dating,to better understand the processes,trends,and mechanisms of Holocene temperature changes on the TP.
文摘青海湖晚第四纪的古环境演化和湖面变化是学术界长期关注的热点问题，争议也较多。我们对青海湖地区种羊场（ZYC）剖面（120 cm厚）全新世风尘堆积的GDGTs （甘油二烷基甘油四醚）化合物相关指标的古环境意义进行了初步研究，以期从一个新的角度对上述问题进行探讨。研究结果表明：1） ZYC剖面的TEX86（由86个碳原子组成的四醚指标）与磁化率正相关，而Ri/b比值（类异戊二烯GDGTs与支链GDGTs丰度的比值）与磁化率负相关。2） ZYC剖面的TEX86指标与湖泊岩芯胖真星介（Eucypris inflata）壳体δ18O指示的7月古水温及长链烯酮（U37K）指示的夏季古水温变化具有相似的变化特征，显示TEX86指标较可靠地指示了青海湖地区的大气温度变化。然而，ZYC剖面的MBT （甲基化指数）和CBT （环化指数）指标在重建古气温方面具有一定的局限性，可能与青海湖地区全新世出现的干旱环境有关。3） ZYC剖面的Ri/b比值与湖泊岩芯E.inflata壳体Sr/Ca比值指示的青海湖湖水的古盐度具有较一致的变化特征，表明Ri/b比值较有效地指示了青海湖地区环境的干湿状况。4） TEX86和Ri/b指标揭示青海湖区在9.5~7.5 ka B.P.为冷干时期；7.5~5.5 ka B.P.为独特的温干阶段，温度在6.2 ka B.P.左右达到最高值；5.5~1.7 ka B.P.为温湿时期；1.7~0 ka B.P.为冷干时期。5）风尘堆积的GDGTs记录表明：7.5~5.5 ka B.P.由于环境干旱，青海湖不太可能出现高湖面；5.5~1.7 ka B.P.由于环境湿润，青海湖很可能出现全新世高湖面；1.7 ka B.P.以来，青海湖地区的气候快速变干。
