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

Glycerol dialkyl glycerol tetraethers (GDGTs) in the frozen soils of Heilongjiang and Qinghai Provinces were determined, and their correlations with environmental parameters were assessed. The results showed that isoprenoid GDGTs (iGDGTs) and branched GDGTs (bGDGTs) were present in the samples. The Ri/b (the abundance ratio of iGDGTs to bGDGTs, aridity index) 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 contents. The CBT index (cyclization of branched tetraethers)-based pH values are in good correlation with the measured soil pH values. These results suggest that the proxies of Ri/b, 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 may not be a main factor controlling the MBT values in frozen soils.