黑龙江与青海冻土甘油二烷基甘油四醚脂类化合物的组成特征

Distribution of glycerol dialkyl glycerol tetraether lipids in frozen soils of Heilongjiang and Qinghai provinces

以黑龙江高纬冻土带与青海高山冻土带土壤样品为研究对象,对其中的甘油二烷基甘油四醚脂(GDGTs)含量进行了测定,并分析了其与环境条件的相关性。研究结果表明,所测样品均含有类异戊二烯GDGTs(iGDGTs)和支链GDGTs(bGDGTs)。不同样品中Ri/b值(iGDGTs含量与bGDGTs含量的比值)差异较大,且和土壤含水率呈负相关,证实了Ri/b指标可以用来反映冻土带土壤的干旱情况。BIT指标与土壤含水率呈正相关,表明其具有指示土壤湿度变化的能力。基于bGDGTs的环化指数(CBT)计算出的pH与土壤实测pH相关性很高,表明该指标可用于重建冻土带古土壤pH。然而,基于bGDGTs的甲基化指标(MBT)与年均气温(MAAT)没有表现出相关性,表明温度不是影响冻土带土壤MBT变化的主要因素。

Glycerol dialkyl glycerol tetraethers （GI）GTs） in the frozen soils of Heilongjiang and Qinghai provinces were investiga- ted, and their correlations with environmental parameters were assessed. The results showed that isoprenoid GI）GTs （iGI）GTs） and branched GDGTs （bGDGTs） were present in the samples. The Ri/u （the abundance ratio of iGEGTs to bGEGTs, aridity in- dex） values varied among different samples and were negatively correlated with soil water content. The BIT values （soil humidity index） were positively correlated with soil water content. The CBT index （cyclization of branched tetraethers）-based pH values were correlated well with the measured soil pH values. These results suggest that the proxies of R~/h, BIT and CBT are applicable in reconstructing paleo-environmental conditions in frozen soils. However, the MBT index （methylation of branched tetraethers, a proxy for mean annual air temperature） shows no correlation with mean annual air temperature, demonstrating that temperature mi~：ht not be a main factor controllin the MBT values in frozen soils.