巴丹吉林沙漠湖泊对浅层沙含水量的影响

Interdune lakes affects the water content of shallow sand layer:a situ observation from the Badain Jaran Sand Sea,China

湖泊与高大沙山共存是巴丹吉林沙漠独特的自然景观,对其形成机制尚未形成共识。已有研究发现沙层含水量偏高的现象可能在高大沙山的形成中发挥了重要作用,但对其水分来源的研究尚不充分。本研究通过对沙漠腹地3个湖盆内气象要素和浅层沙含水量时空分布的对比,结合前人对水同位素和水分运移规律的研究,发现湖泊的存在大大增加了湖盆内空气相对湿度和浅层沙含水量的变化幅度,并影响了浅层沙含水量随高度的分布特征;相关分析表明,控制有湖湖盆浅层沙含水量变化的主导过程是气温升降引起的水分损失与补充,而干湖盆浅层沙水分补给主要来自风的平流输送。尽管沙丘分层含水量的长期定量观测仍有待开展,但现有证据表明巴丹吉林沙漠高大沙山沙层含水量偏高的现象很可能是湖泊蒸发的水汽以土壤吸附水汽或凝结水等形式逐渐运移至沙层内而形成,是湖泊-沙山体系长期共存、形成局地水汽平衡的结果。这为沙层水分来源研究提供了新的视角,也对沙漠腹地水资源开发利用有一定的参考意义。

The coexistence of lakes and mega-dunes is a unique landscape of the Badain Jaran Sand Sea in China,and its formation mechanism has not been widely recognized.Some studies have found that the high content pore water may be important in the formation of mega-dunes,but more efforts are needed to research its recharge source.Based on the comparison of meteorological elements and the temporal and spatial distribution of shallow layer sand water content in three lake basins in the hinterland of the sand sea,combined with previous studies on water isotope and water movement,we found that the existence of lakes greatly increased the variation range of air relative humidity and shallow sand water content in the lake basin,and affected the distribution of water content with height.The correlation analysis shows that the main process controlling the change of water content of shallow sand layer is the water loss and replenishment caused by temperature fluctuation,while the water replenishment of shallow sand layer in the dry lake basin is mainly from advection water transport of wind.Although long-term quantitative observation of the water content of sand layers in different depth is still to be carried out,the existing evidence shows that the high soil water content of mega-dunes in the Badain Jaran Sand Sea is the result of local water vapor balance accompanied by the coexistence of lakes and mega-dunes.Water vapor from the lakes probably migrates into the sand layer gradually in the form of soil adsorption water or condensed water.This provides a new perspective for the research on the source of water in the sand layers,and also has a certain reference significance for the development and utilization of water resources in the hinterland of Badain Jaran Sand Sea.