敦煌莫高窟干旱地区水分凝聚机理分析

通过对敦煌莫高窟戈壁地质结构的调查和洞窟检测,结合气象资料对戈壁土壤水分凝聚机理进行了分析,并根据形成机理在野外进行了水分凝结的覆膜实验.结果表明,在莫高窟戈壁区的上层砾砂中,由于强烈的温度日较差变化,形成了凝结水分;另外源于地下深处的水分通过土壤盐分的吸湿吸附作用在地下10～40cm范围内相对富集,并由于剧烈的波动呈现时空异质性变化.将凝结、吸湿吸附等方式形成的土壤水分统称为凝聚水分.凝聚是水分存储于一定土壤的结构过程,与太阳辐射、温度、湿度等气候因子密切相关.变温层土壤的温度、盐分、湿度、结构、密闭程度、地热等对水分的凝聚有重要影响.水分的凝聚机理对干旱地区的生态建设和文物保护具有重要的现实意义.

Mechanism analysis on water cohesion in arid area of Dunhuang Mogao Grottoes

Based on the investigation in the geologic structure at Dunhuang Mogao Gobi, and the inspection of the physical and chemical condition of the caves, associated with the weather data, the formation mechanism of the water cohesion in Gobi soil had been analyzed, and consequently, we did condensed water experiment by covering film. Results indicate that the rapid change of the wide range of daily temperature at the upper stratum of the gravel contributed to the formation of the condensed water. In addition, the water vapor from underground was adsorbed by salinity and soil particles, resulting in an enrichment of subterranean soil moisture in 10-40cm depth, and showing space-time heterogeneity by tempestuously fluctuation. The water formed by condensation and adsorption are all called by a joint name of the cohesion water in this paper. The cohesion is structure course of the water stored in some soil, closely correlated with the climate factors such as solar radiation, temperature and moisture. The temperature, salinity, moisture, gravel structure, coverage and subterranean heat flux within the layer with variable temperature have important effects on the water cohesion. The understanding of mechanism of the water cohesion has important practical application in environmental reconstruction and cultural relics preservation in arid area.