基于稳定氢氧同位素的高寒草甸坡地壤中流产流研究

以青海湖流域高寒草甸坡地为例, 通过收集2013年4—9月大气降水、土壤水和壤中流样品, 测定其稳定氢氧同位素值(δD和δ18O)并分析不同水体同位素特征, 同时使用二源线性混合模型辨析壤中流的产流来源.结果显示:大气降水的氢氧同位素值更加接近浅层(0~40 cm)土壤水的氢氧同位素值, 说明大气降水对浅层土壤水的补给作用要高于深层(40~80 cm)土壤水, 而壤中流的氢氧同位素值更加接近深层土壤水的氢氧同位素值, 说明该部分壤中流主要来源于降水前储存在土壤中的水分; 在非降水期间, 土壤水对坡上和坡中位置壤中流的平均贡献率分别为88.54%和78.43%;当降水事件发生时, 壤中流的水分来源由土壤水逐渐转变为大气降水, 而降水停止后土壤水重新成为壤中流的主要来源, 说明土壤水是高寒草甸壤中流产流的重要来源.

Revealing the Processes of Subsurface Flow in an Alpine Meadow Slope Using Deuterium and Oxygen-18 Isotopes

The water source of subsurface flow on a slope of alpine meadow in the Qinghai Lake watershed, China, was identified with the Deuterium and Oxygen-18 isotope values of precipitation, soil water and subsurface flow during April to September in 2013 based on a two-source model. Results showed that the contribution of precipitation to soil water was higher in surface soil than that in deeper soil. The isotope values of subsurface flow were closer to those of deeper soil water, which meant that subsurface flow was mostly derived from the deeper soil water. In addition, the average contribution ratios of soil water to subsurface flow on the upper slope and the middle slope in non-rain periods were 88.54% and 78.43% respectively. But during the rainfall events, the main water source of subsurface flow changed from soil water to rainfall and changed back to soil water after rainfall. It was concluded that soil water played a critical role in water source of subsurface flow.