基于组合提取方式的土壤水混合滞后效应

Lag effect of soil water mixing based on the combination extraction method

为量化研究土壤水分库之间的混合滞后效应,采集天涝池流域祁连圆柏样地0~60 cm处的土壤作为研究对象,选择氢氧同位素组成差异显著的两种矿泉水作为实验用水.先用轻水浸湿烘干土样,再添加重水使其饱和,静置一定时间(0、8、24、72、120、168 h)后,利用离心分离与真空蒸馏法分别提取不同张力下的土壤水并测定其氢氧同位素值.利用多因素方差分析及时变混合模型确定各土层土壤水的混合平衡时间.结果表明,同一土壤样品在不同张力下的土壤水同位素组成差异显著,离心分离提取的低张力(<0.01 MPa)、中张力(0.01~0.10 MPa)下的土壤水氢氧同位素值要比真空蒸馏提取的高张力(>1.00 MPa)下的土壤水更富集.由数学统计分析与模型拟合结果可知,各土层土壤水氢氧同位素组成达到混合平衡的时间不同,自表层土壤向下分别为4.04 (0~15 cm)、4.75 (15~30 cm)、5.71 (30~45 cm)、6.46 d (45~60 cm).相关性分析表明,土壤砂粒与黏粒含量、饱和含水率、土壤容重等物理参数与混合平衡时间显著相关,土壤的物理特性是影响土壤水混合过程的主要因素.

In order to quantify the hysteretic effect of isotope mixing between soil moisture reservoirs, we collected the soil at 0-60 cm of a Sabina przewalskii sample plot in the Tianlaochi watershed as the research object, and selected two kinds of mineral water with significant differences in isotopic composition as the experimental water. In processing the experimental soil sample, the dried soil sample was first soaked with light water, and then heavy water was added to saturate it. After leaving the test soil sample for a certain period of time(0, 8, 24, 72, 120, 168 h), we used centrifugal separation and vacuum distillation to extract soil water under different tensions and determined its hydrogen and oxygen isotope values.We used the multi-factor analysis of variance and a time-varying mixing model to determine the mixing equilibrium time of the soil water in each soil layer. The results showed that the isotope composition of soil water under different tensions of the same soil sample was significantly different, and the hydrogen and oxygen isotope values of soil water under low tension(<0.01 MPa) and medium tension(0.01-0.10MPa) extracted by centrifugal separation were higher than those under high tension(>1.00 MPa) extracted by vacuum distillation. According to the results of a mathematical statistical analysis and model fitting, the time for the hydrogen and oxygen isotopic composition of the soil water in each soil layer to reach the mixing equilibrium was different, and they were respectively 4.04(0-15 cm), 4.75(15-30 cm),5.71(30-45 cm) and 6.46 d(45-60 cm). A correlation analysis showed that physical parameters such as soil sand and clay content, saturated water content and soil bulk density were significantly related to the mixing equilibrium time. Soil physical properties were the main factors affecting the process of soil water mixing.