毛乌素沙地包气带土壤水稳定同位素分布特征及其来源判别

Distribution characteristics and source discrimination of soil water stable isotope in shallow aerated zone of Mu Us Sandy Land

研究探讨土壤水循环过程,阐明不同深度包气带液态水、水汽的补给来源,对毛乌素沙地生态恢复具有重要意义。文中利用在毛乌素砂土剖面不同季节不同层位液态水和水汽中δ^(2)H、δ^(18)O值,拟合蒸发线定性分析各层水分来源。依据δ^(18)O值在土壤剖面垂向分布特征建立多元线性混合模型定量分析总水势最低层位地下6-7m处水汽、液态水分别受上层水和下层水的补给比例。结果表明:自然状态下液态水主要受上层降水活塞流入渗补给,旱季补给比例(82%-92%)大于湿季(68%-73%)。水汽在受温度梯度驱动下研究期内湿季(7、9月)主要由上层水汽补给(86%-92%),下层水汽补给比例少且均衡(8%-14%),旱季则相反。该结论有助于今后为当地生态恢复和水资源合理开发利用提供科学依据。

It is of great significance for the ecological restoration of Mu Us Sandy Land to study the process of soil water circulation and clarify the replenishment source of liquid water and water vapor in the unsaturated zone at different depths.In this paper,theδ^(2)H andδ^(18)O values of liquid water and water vapor in different seasons and layers in the Mu Us sandy soil profile were used to qualitatively analyze the water source of each layer by fitting evaporation lines.According to the vertical distribution characteristics ofδ^(18)O values in soil profile,a multivariate linear mixture model was established to quantitatively analyze the proportion of water vapor and liquid water supplied by upper and lower water at underground layer of 6-7 m where the total water potential is lowest.The results show that the liquid water is mainly replenished by upper precipitation piston inflow and infiltration in natural state,and replenishment proportion in dry season(82%-92%)is greater than in wet season(68%-73%).In the wet season(July and September)driven by the temperature gradient,the water vapor(86%-92%)mainly comes from the upper water,while the supply from lower layer is in a small and balanced proportion(8%-14%);the supply law in dry season is opposite.This conclusion will provide scientific basis for local ecological restoration and rational development and utilization of water reasons in the future.