长江源区土壤水稳定同位素特征研究

Study on stable isotope characteristics of soil water in the source region of Yangtze River

本文通过采集长江源区土壤样品,对不同深度土壤水分稳定同位素变化特征及其空间分布特征进行分析,使用端元混合径流分割模型对土壤水的来源进行计算,结果表明:土壤温度在0~100 cm范围内呈下降趋势,土壤含水率在0~80 cm范围内呈下降趋势,80~100 cm范围内呈上升趋势;土壤水的δ^(2)H和δ^(18)O值在0~100 cm深度范围内波动变化,且变化趋势相似,土壤水的δ^(18)O及δ^(2)H值变化范围分别为-151.273‰~-63.605‰和-21.052‰~-8.676‰。土壤水的δ^(2)H和δ^(18)O在空间上总体呈西部富集,而东南部贫化的特点;蒸发线(EL)为δ^(2)H=7.23δ^(18)O-5.27(R^(2)=0.88);土壤水稳定同位素受到海拔梯度和土壤含水率的影响;降水对土壤水的贡献高于地下冰融水,且随着海拔梯度的增加,降水对土壤水分的贡献率呈现增加趋势,在4150~4777 m范围内降水对土壤水的贡献率为70%~94%;地下冰融水在海拔4150~4555 m范围内对土壤水的贡献率为8%~30%,在海拔4613~4777 m范围内贡献率下降,为6%~8%。本研究为深入了解长江源区土壤水分运动及稳定同位素研究提供了理论依据。

Through the collection of soil samples,this study analyzed the characteristics of stable isotope variations and their spatial distribution in soil water at different depths in the source region of Yangtze River.The sources of soil water were determined by the study using an end-element mixed runoff partition model.The findings revealed that within the range of 0~100 cm,soil temperature exhibited a decreasing trend,while the region of 0~80 cm and the range of 80~100 cm showed a rising tendency in soil moisture content.Within the depth range of 0~100 cm,the δ^(2)H and δ^(18)O values of soil water varied,and their trends were similar.The range of variation for the soil water’s δ^(2)H and δ^(18)O values was,respectively,-151.273‰ to -63.605‰ and -21.052‰ to -8.676‰.Spatially,soil water’s δ^(2)H and δ^(18)O content was often enhanced in the western and depleted in the southeast.The evaporative line(EL)was represented by δ^(2)H=7.23δ^(18)O-5.27(R^(2)=0.88).The altitude gradients and soil moisture content had an impact on the stable isotope composition of soil water.The contribution of precipitation to soil moisture increased with increasing altitude gradient,and it was greater than the input of meltwater from ice melt water.Precipitation accounted for 70% to 94% of the soil’s water content between 4150~4777 m above sea level.Between 4150~4555 m above sea level,ice melt water contributed 8% to 30% of soil water;between 4613~4777 m above sea level,it reduced to 6%to 8%.In an effort to improve our understanding of soil water circulation and stable isotope research in the source region of Yangtze River,this study provides a theoretical basis.