应用氢氧稳定同位素对极端干旱区蒸发水分来源的确定  

The use of stable hydrogen and oxygen isotopes to determine the source of evaporation water in extremely arid areas

作　　者：李红寿[1,2] 汪万福[1,2] 詹鸿涛[1,2] 邱飞[1,2] 张正模[1,2] 武发思[1,2] 

机构地区：[1]敦煌研究院保护所,敦煌736200 [2]古代壁画保护国家文物局重点科研基地,敦煌736200

出　　处：《生态学报》2016年第22期7436-7445,共10页Acta Ecologica Sinica

基　　金：国家自然科学基金项目(41363009);国家科技支撑计划项目(2013BAC07B02);甘肃省科技计划项目(1308RJZF290);敦煌研究院院级课题(201306)

摘　　要：长期监测发现敦煌莫高窟窟顶戈壁存在稳定的蒸发水分。为了进一步厘清蒸发水分的来源,利用拱棚-凝结法定期收集蒸发水分,应用水同位素示踪原理监测凝结水分、莫高窟降水和潜水的δD和δ^(18)O值,以揭示戈壁蒸发水分的来源。结果表明,蒸发水分的δD、δ^(18)O平均值分别为-33.06‰和-5.33‰,莫高窟降水为-66.44‰和-8.57‰,潜水为-72.19‰和-9.75‰,说明当地潜水并非来自于莫高窟降水;通过经纬度和海拔,应用在线降水同位素计算的当地降水δD和δ^(18)O值(-60.00‰,-8.50‰)和降水加权平均值(-5.30‰,-0.75‰)同样表明,当地降水不是地下潜水的合理来源,而党河源区(野马山)的降水(-86.00‰,-12.00‰)才是地下潜水的真正来源。土壤水分蒸发实验与土壤垂直剖面水分检测表明,戈壁深厚包气带土壤在潜水水汽向上运移过程中选择了δ值相对较高的潜水水分,因此,戈壁蒸发水分来自地下潜水,存在清晰的来源通道。极干旱区蒸发水分来源的再确定为蒸发潜水的利用奠定了基础,对极干旱区生态恢复有重要意义,并为干旱、半干旱区地下水的利用提供了新视角,为莫高窟洞窟水分来源研究亦提供了重要参考。Extremely arid desert occupies a terminal position in the biological geochemical circulation system. These deserts harbor huge amounts of energy and mineral resources. However,a large number of ancient sites,which are very important to the modern tourism industry,also occur in such areas. Lack of water constitutes the most serious kind of land deterioration in the extremely arid deserts of the world. At present,desert land degradation,global climate warming,and human interference are intensifying the destruction of the natural desert landscape,and hence our historical and cultural heritages are facing unprecedented losses. Consequently, methods for finding available water sources for ecological restoration and protection are urgently required. It has been found that there exists a stable amount of water evaporation in the extremely arid Gobi area of the Dunhuang in China. In order to clarify the source of this evaporation,we used a greenhouse to condense and collect evaporated water and monitored the δD and δ^18O values present on a weekly basis. Atthe same time,we monitored the δD and δ^18O values of the precipitation and phreatic water present. Thus,the source of the evaporation water in the Gobi could be revealed based on the method of isotopic tracing. After monitoring for one year,our results showed that the average values of δD and δ^18O in the evaporation water were- 33. 06‰ and- 5. 33‰,respectively. The equivalent results for the precipitation were found to be- 66. 44‰ and- 8. 57‰,respectively,and for phreatic water they were- 72. 19‰ and- 9. 75‰. This rules out the possibility that precipitation is the source of the phreatic water. Monitoring of the surface water in the soil at a vertical depth of 4. 5 m showed that the δD and δ18O values（the average values were- 22. 68‰ and 8. 58‰,respectively） of the soil water from 2. 5 m increases due to the effect of the dry climate and reach the maximum values at 1. 2 m. Above this level,the values of δD and δ^18O decrease because of t

关 键 词：同位素 极干旱区 蒸发 降水 

分 类 号：P426.2[天文地球—大气科学及气象学]