黄土区典型小流域包气带土壤水同位素特征

通过野外调查与室内试验相结合的方法,对王茂沟流域降水及5种土地利用类型土壤剖面稳定氢氧同位素特征进行对比分析,为黄土区土壤水分运移机制、模型参数识别及生态保护与重建提供科学依据。结果表明:(1)降水与5种土地利用方式下土壤水中δD和δ~(18) O的变化范围分别为(-118.08‰)~(-14.37‰),(-16.13‰)~(1.41‰)和(-92.36‰)~(-34.98‰),(-12.48‰)~(-5.01‰),平均值分别为-37.36‰,-5.65‰和-60.18‰,-7.81‰。(2)不同土地利用类型的土壤水氢氧同位素变化存在显著性差异,土壤通透性草地梯田林地坝地坡耕地,表层土壤水分的蒸发分馏程度梯田草地坝地坡耕地林地。(3)林地和草地"优先流"现象明显,草地"优先流"程度最大,林地能显著延伸"优先流"发生路径。(4)草地、林地和梯田分别在160,200,200cm土层及以下氢氧同位素值相对稳定,坝地和坡耕地可能对地下水水质与补给造成较大影响。

Soil Water Isotope Characteristics of the Vadose in a Typical Small Watershed on the Loess Plateau of China

In this study,stable isotope compositions of the precipitation and soil water of five different kinds of land use patterns in Wangmao ditch small watershed on the Loess Plateau were analyzed,the aim was to understand the characteristics of stable isotopes along the soil profile,and provide a scientific basis for understanding the mechanisms of soil water movement,the identification of model parameters and the ecological protection and reconstruction.The results showed that:(1) The variation ranges of δD (or δ18O) in the precipitation was from-118.08％ (or-16.13％) to-14.37％ (or 1.41％),with a mean value of-37.36％ (or -5.65％).The variation range of δD (or δ18O) in soil water of five kinds of land use was from-92.36％ (or -12.48％) to-34.98％ (or-5.01％),with a mean value of-60.18％ (or-7.81％).(2) There were significant differences in the changes of hydrogen and oxygen isotope.Soil permeability of the five kinds of land use was as follows:grassland ＞ terraced fields ＞ forest land ＞ dam land ＞ slope cropland.Soil water evaporation fractionation in different land use patterns was as follows:terraced fields ＞ grassland ＞ dam land ＞ slope cropland ＞ forest land.(3) The woodland and grassland "preferential flow" phenomenon was obvious;the grassland "preferential flow" was the maximal,and the woodland could extend the "preferential flow" path obviously.(4) Hydrogen and oxygen isotopic values in the 160,200 and ＞200 cm soil layers of the grassland,woodland,and terrace were relatively stable.The dam land and sloping farmland might affect the quality and recharge of groundwater significantly.