用隔绝法对极干旱区土壤水分来源的分析

 通常认为极干旱区土壤水分来源于降水、大气或凝结水，深埋区不存在潜水蒸发。然而通过使用拱棚法初步证明在极干旱深埋区存在潜水蒸发，而潜水是土壤水分的重要来源。为了进一步求证土壤水分来源，开挖200 cm×200 cm×200 cm的土坑，完全隔绝与下层土壤及四周的水分联系，回填后监测土壤10、30、50、100、150 cm的空气温湿度；同时设置与四周隔绝但底面联通的对照坑。27 d后都模拟25 mm降雨。监测发现模拟降雨前联通土壤的水分含量、空气相对湿度、绝对湿度都明显高于隔绝土壤。1 a后远离降雨时土壤水分的检测发现隔绝土壤水分含量低于联通对照，但因隔绝土壤处于潜水蒸发漫溢的相同气象环境，其湿度不会无限下降。隔绝对比实验反演证明深埋极干旱区存在潜水蒸发。

Applying isolation method on study of soil water source in an extremely dry area

Usually considered that in extremely arid area the soil moisture comes from rainfall, atmosphere or condensed water, deep phreatic water evaporation does not exist. But the greenhouse method test shows that there exists phreatic water evaporation, and phreatic water is an important source of soil moisture in the extremely arid area. To further verify sources of soil water, two soil pits, were excavated with a scale of 200 cm×200 cm×200 cm, one pit’s connections were completely cutout with its bottom soil and surrounding soil(called as isolated pit), another pit’s connections was cutout with its surrounding soil, but was kept in with bottom soil(called as connected pit), two sets of HOBO-U23-1000 instrument were inserted into the two pits’ backfilling soil to monitor their temperature and humidity at the depths of 10, 30, 50 and 100 cm. After 27d, a 25mm rainfall simulation test was carried out for the two backfilled pits. Before the rainfall simulation test mentioned above, the connected pit’s soil relative humidity, absolute humidity, soil water content are significantly higher than that of the isolated pit. After a year during which the rainfall was without for long time, the test results found that the soil water content of the connected pit was higher than that of the isolated pit; however, under the condition of same meteorological environment, because the phreatic water evaporation spills over, the isolated pit’s soil humidity does not infinitely dropped down. The comparison experiment proves inversely that the deeply buried phreatic water’s evaporation exists in the extremely arid area’s.deeply buried soil.