用D、^(18)O同位素确定黑河中游戈壁地区植物水分来源

Determination of Water Sources of Gobi Plants by D and ^(18)O Stable Isotopes in Middle Reaches of the Heihe River

于2008年7月在黑河中游临泽县平川镇戈壁地区采集降雨、地下水、土壤和植物茎干样品并进行水分的D、18 O同位素测试,分析戈壁地区不同深度土壤水分的来源,确定泡泡刺(Nitraria sphaerocarpa)、红砂(Reau-muria soongorica)等荒漠植物的吸水层位及其对降雨和地下水的依赖程度。研究发现:①土壤剖面0～130cm深度范围内的土壤水主要接受降雨的补给;130cm以下,可能接受潜水蒸发补给,或者是前期较大降雨入渗与潜水蒸发补给的叠加;②土壤水的δD、δ18 O值与深度呈指数关系;降雨入渗补给会打乱剖面的稳态,土壤水的δD、δ18 O同位素组成是现存土壤水和降雨的混合;③泡泡刺和红砂都是利用深度大于185cm的土壤水,泡泡刺吸水层位比红砂更深,表明荒漠植物的生长主要依赖更为稳定的潜水水源。

The 3D and δ^18O values of rainfall, groundwater, soil water and water extracted from two Gobi plants were measured to analyze the sources of soil water at different depths in the Gobi area in Linze in the middle reaches of Heihe River, and to determine the soil layer in which two Gobi plants extract water and their dependence on rainfall and groundwater. Results show that： （1） Soil water at the layer above 130 cm in depth are mainly recharged by rainfall, and that below 130 cm are recharged by evaporation of phreatic water or the infiltration of earlier heavy rainfall; （2） δD and δ^18O values of soil water decline with soil depth, and there is a typical exponential relation, and δD and δ^18O values of soil water are influenced by both current soil water and infiltration of rainfall; and （3） Nitraria sphaerocarpa and Reaurnuria soon- gorica extract soil water below the depth of 185 cm, but Nitraria sphaerocarpa extracts deeper soil water than Reaumuria soongorica does, which indicate that the growth of desert plants mainly rely on phreatic water which is more stably available.