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在潜水埋深超过200m的敦煌莫高窟极干旱沙漠区,用拱棚法和微型空气湿度监测仪对流沙水分的时空分布格局进行监测,并对水分的来源进行分析。拱棚膜面凝结水分的持续抽取表明,在典型干旱气候条件下,有源源不断的沙地水分蒸发,其中1.25g.m-2.d-1的水分在膜面凝结。沙地水分的时空动态分布格局表明,存在水分向上运移的温湿度条件。由此判定,除降水之外地下潜水蒸发是沙地水分最基础的来源。实验表明,干沙层虽然对沙地水分蒸发具有极强的抑制作用,但在升温过程中仍存在水分蒸发;在降温过程不但可从下层流沙吸收大量的水分,而且可吸收大气水分。沙地的蒸发量大于来自大气的吸湿量,总有少量的水分流失。沙地水分潜水来源的确定,不但对沙漠化的治理提供了新思路,而且对莫高窟文物的保护具有十分重要的意义。
In the extremely arid desert area of Dunhuang Mogao Grottoes more than 200m in depth, the spatiotemporal distribution pattern of sediment moisture was monitored by arch method and micro-air humidity monitor, and the source of water was analyzed. The continuous extraction of water content in the arch membrane surface shows that in the typical arid climatic conditions, there is a steady stream of water evaporation, of which 1.25g.m-2.d-1 moisture condensation in the membrane surface. The spatial and temporal dynamic distribution pattern of water in sandy land shows that there is temperature and humidity conditions for upward migration of water. It is thus determined that, in addition to precipitation, submerged evaporation is the most basic source of water in the sand. Experiments show that although the dry sand layer has a very strong inhibitory effect on water evaporation in the sandy land, there is still water evaporation during the warming process. In cooling process, not only can a large amount of water be absorbed from the lower quicksand, but also the atmospheric moisture can be absorbed. Sand evaporation is greater than the amount of moisture from the atmosphere, there is always a small amount of water loss. The determination of the source of water submersion in sandy land not only provides new ideas for the treatment of desertification, but also has great significance for the protection of Mogao Grottoes.