基于氢氧稳定同位素特征的潜水蒸发影响程度研究

Study on influence degree of phreatic evaporation based on hydrogen and oxygen isotope characteristics

干旱绿洲区在新疆发挥着重要的生态保护与水源涵养功能,区内的地下水不仅提供了宝贵的淡水资源,更是植物水分的主要来源。开展潜水蒸发影响程度研究,对分析干旱绿洲区土壤水分运移,土壤水与地下水转化关系、植物水分利用等方面都具有十分重要的意义。本文采用环境同位素、土壤物理和化学分析方法研究了新疆塔里木河下游干旱绿洲区胡杨(Populus euphratica)、柽柳(Tamarix ramosissima)等典型植被生长区的土壤剖面特征。结果表明:塔里木河下游干旱绿洲区具有强烈的潜水蒸发和毛细作用,对土壤水氢氧稳定同位素的分馏、土壤含水率、土壤含盐量的分布具有较大影响;自潜水面向上,随着高度增加,土壤水的氢氧稳定同位素值逐渐减小,并在1~1.5 m处达到最小值后又逐渐增大;土壤含水率逐渐减小,至1~1.5 m处土壤含水率减小的速率减缓;土壤含盐量在潜水面附近总体保持稳定,至1~1.5 m处含盐量逐渐开始增大;综合不同植被生长区土壤剖面数据,反映出该区秋季潜水蒸发影响深度为1~1.5 m。利用氢氧稳定同位素的分馏特征来研究干旱绿洲区潜水毛细高度及蒸发深度,可以获得传统水文地质和潜水蒸发实验无法得到的信息。

The arid oasis area plays an important role in ecological protection and water conservation in Xinjiang.The groundwater in the area provides precious freshwater resources and is the main source of water for plants.It is important to study soil water transport,the relationship between soil water and groundwater transformation,and plant water in arid oasis areas,by studying the influencing degree of phreatic evaporation.To study the soil profile characteristics of typical vegetation growing areas,such as Populus euphratica and Tamarix ramosissima,in arid oasis area of the lower reaches of the Tarim River,environmental isotope,soil physical,and chemical analysis methods were used in this paper.The results showed that there are strong phreatic evapotranspiration and capillarity in the lower reaches of the Tarim River.It greatly influences the fractionation of hydrogen and oxygen isotopes,soil moisture content,and soil salinity.From the diving face up,as height increases,the stable isotope values of hydrogen and oxygen in soil water decreased gradually and reached a minimum value at 1-1.5 m and then gradually increased.Gradually,the soil moisture content decreases,and the rate of decrease slows down at 1-1.5 m.The soil salinity generally remains stable near the water table,and the salt content gradually increases at 1-1.5 m.Integrate soil profile data of different vegetation growing areas,the influence depth of phreatic evapotranspiration is 1-1.5 m in autumn.Using the fractionation characteristics of hydrogen and oxygen isotopes to study the phreatic capillary height and evaporation depth in arid oasis areas,it is possible to get the information that traditional hydrogeology and phreatic evaporation experiments cannot get.In the next step,it is necessary to summarize the water-salt transport law and its movement model under different evapotranspiration conditions.