阿拉善沙漠湿沙层水分来源同位素示踪

为弄清阿拉善沙漠湿沙层的水分来源，在该地区进行了人工模拟降水入渗的示踪试验。模拟单次降水量为59 mm，观察剖面最大入渗深度仅为46 cm，这一结果表明该地区的降水几乎不能通过沙层入渗到地下水中。对4个沙丘湿沙层剖面中不同深度的含水率、Cl-、δD与δ18O进行了分析，数据显示在蒸发能力极强的阿拉善地区，地下水是以薄膜水的形式，通过蒸发、凝结向地表运动，最终蒸发排泄。泉水、井水、湖水与土壤水中的同位素特征表明具有相同的补给源，均来自于地下水。推断横穿阿拉善地块的杂多-雅布赖断裂带与狼山-日喀则断裂带中可能存在地下水深循环通道，青藏高原河流、湖泊的渗漏水可能是阿拉善地下水的主要补给源。

Isotopes tracer research of wet sand layer water sources in Alxa Desert

Field simulation experiments were conducted to identify the water source of the wet dune in Alxa Desert. We simulated 59 mm of precipitation, and found that the maximum infiltration depth in the dune profiles was only 46 cm, suggesting that the rainfall infiltration through sand to the groundwater is nearly impossible in this area. In the four dune profiles, δD, δ18O, and Cl- concentrations in the soil water, and the moisture contents of the wet dune at different depths, were analyzed. In Alxa Desert with strong evaporation, groundwater in the form of film water evaporates, condensates, transports to the surface, and finally discharges by evaporation. The isotopic compositions of springs, wells, lakes, and soil water show that they all originate from the groundwater, whose source is exogenous. We suggest that deep-circulation water channels may exist in Zaduo-Yabrai and the Langshan-Shigatse basement fault zone, and water leakage from the Qinghai-Tibet Plateau may be the main recharge source of the groundwater in Alxa Desert.