青藏高原东部现代泥炭GDGTs分布特征及环境意义

运用HPLC-APCI-MS详细分析了青藏高原东部红原现代泥炭(32°46'N,02°31'E)和越西现代泥炭(28°46'N,102°34'E)中甘油二烷基甘油四醚类脂物(glycerol dialkyl glycerol tetraethers,简称GDGTs)的组成及分布特征,检测出了丰富的GDGTs化合物,显示研究区分布着产甲烷菌、氨氧化古菌、细菌等多种微生物。其中,细菌支链GDGTs(branched GDGTs,简称bGDGTs)丰度明显高于古菌类异戊二烯GDGTs(isoprenoid GDGTs,简称iGDGTs)。无环的GDGT-0和archaeol是古菌iGDGTs的主要组分,说明古菌以产甲烷菌为主。bGDGTs中Ia与Ⅱa丰度最高,由CBT(环化指数)参数得到的pH值与泥炭实测pH值相近,但基于MBT'(甲基化指数)-CBT指标得到的年平均大气温度(MAT)与两研究区现代年平均温度有一定差别。通过该项工作发现今后进行区域细菌bGDGTs相关环境参数的校正是十分必要的。

DISTRIBUTIONS AND ENVIRONMENTAL SIGNIFICANCE OF GDGTs IN MODERN PEAT SAMPLES FROM EASTERN TIBETAN PLATEAU

In our study, the samples were collected from 2 modern peat sediments, namely Hongyuan region(32°46'N,102°31'E; 3508m a.s.l.) and Yuexi region(28°46'N,102°34'E; 1981m a.s.l.) in the eastern Tibetan Plateau.The glycerol dialkyl glycerol tetraethers(GDGTs) in all samples were analyzed by high performance liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry(HPLC-APCI-MS).Our results have shown that microbial assemblages are abundant in the Tibetan peats, including methanogens, ammonia-oxidising Thaumarchaeota and likely anaerobic bacteria based on distributions of branched and isoprenoidal GDGTs.Branched GDGTs(bGDGTs) are much more abundant than the isoprenoid GDGTs(iGDGTs).GDGT-0 and archaeol are predominant in all peat samples, indicating that methanogens are the major archaea.The branched GDGTs are dominated by bGDGT Ia and Ⅱa.The cyclization of bGDGTs(CBT)-derived pH values are closed to the measured peat pH in the study regions.However, the mean annual air temperature(MAT) estimates derived from the methylation of bGDGTs and cyclization of bGDGTs(MBT'-CBT) are different from the present mean annual temperature of the study regions.MBT'-CBT-derived MAT values are higher than present mean annual temperature in Hongyuan region and lower than that in Yuexi region.Taken together, the global soil calibration of(Peterse et al., 2012) [31] appears not to be applicable to MAT estimates in Tibetan peats.Therefore, we suggest that it is necessary to calibrate the MBT'-CBT index of bGDGTs in peat settings.