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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Assessing past temperature and soil pH estimates from bacterial tetraether membrane lipids: Evidence from the recent lake sediments of Lochnagar, Scotland
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Assessing past temperature and soil pH estimates from bacterial tetraether membrane lipids: Evidence from the recent lake sediments of Lochnagar, Scotland

机译：根据细菌四醚膜脂质评估过去的温度和土壤pH值：苏格兰Lochnagar最近的湖泊沉积物的证据

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摘要

Past variation in soil pH and air temperature can potentially be reconstructed from the relative abundance in sediments of branched glycerol dialkyl glycerol tetraethers (GDGTs), synthesized by anaerobic bacteria. Specifically, the cyclization of branched tetraethers (CBT) is believed to be a function of pH, whereas temperature can be estimated from a combination of the extent of both the CBT and methylation of branched tetraethers. Here we explore this potential by comparing a recent sedimentary GDGT profile from Lochnagar, Scotland, with reconstructed air temperature (statistically extrapolated from regional instrumental data sets) and diatom-inferred lake water pH for the past ～200 years. Branched glycerol dialkyl glycerol tetratether and diatom-inferred pH generally agree throughout the core, supporting the use of cyclization of branched tetraethers to reconstruct pH. During the period of rapid industrial acidification (～1860-1970 A.D.), changes in diatom-inferred pH lag behind those inferred using branched tetraethers by between 10 and 50 years, possibly due to differing nonlinear responses to acid deposition within soil and lake water environments. However, branched-GDGT-derived temperatures are bothlower than extrapolated mean annual air temperature estimates (by ～5℃) and exhibit at least double the rate of reconstructed warming (～2.5℃ in 200 years). At Lochnagar, methylation and cyclization of branched tetraethers are closely correlated (r~2 = 0.96) suggesting that in this setting the underlying controls over the two indices may not significantly differ. Therefore the validity of branched-GDGT-derived temperature is uncertain and further research is required to address the environmental controls over branched glycerol dialkyl glycerol tetratether synthesis and thus their value as palaeoclimate proxies.
机译：可以通过厌氧细菌合成的支化甘油二烷基甘油四醚（GDGTs）沉积物中的相对丰度来重建过去土壤pH和气温的变化。具体而言，认为支链四醚（CBT）的环化是pH的函数，而温度可以根据CBT的程度和支链四醚的甲基化的组合来估算。在这里，我们通过比较苏格兰Lochnagar的最新沉积GDGT剖面，重建的气温（从区域仪器数据集统计推断）和硅藻推断的过去200年的湖水pH值，来探索这种潜力。支链甘油二烷基甘油四醚和硅藻推断的pH值在整个核心范围内都一致，从而支持使用支化四醚环化来重建pH。在工业化快速酸化时期（公元1860-1970年），硅藻推断的pH值的变化比支化四醚推断的pH值滞后10至50年，这可能是由于土壤和湖泊水环境中对酸沉降的非线性响应不同。然而，从GDGT支化的温度均低于推算出的年平均气温估计值（降低〜5℃），并且至少表现出重建变暖速率（200年内〜2.5℃）的两倍。在Lochnagar，支化四醚的甲基化和环化密切相关（r〜2 = 0.96），表明在这种情况下，对这两个指数的潜在控制可能没有显着差异。因此，支链-GDGT衍生的温度的有效性尚不确定，因此需要进一步研究以解决支链甘油二烷基甘油四醚合成的环境控制问题，以及其作为古气候代理的价值。

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