干旱区咸水灌溉土壤水中氢氧稳定同位素组成的动态特征  

Dynamic Variation Characteristics of Hydrogen and Oxygen Stable Isotope Composition in Soil Water after Salt Water Irrigation in Arid Area

作　　者：丁洁 刘延锋[1] 刘倩[1] 王建军[1] DING Jie;LIU Yanfeng;LIU Qian;WANG Jianjun(School of Environmental Sciences,China University of Geosciences (Wuhan),Wuhan 430074,China)

机构地区：[1]中国地质大学(武汉)环境学院,湖北武汉430074

出　　处：《安全与环境工程》2020年第3期32-39,共8页Safety and Environmental Engineering

基　　金：国家自然科学基金项目(41572224,51709232)。

摘　　要：土壤水蒸发是水文循环的重要环节,利用氢氧稳定同位素来确定土壤水蒸发量的研究中很少考虑矿化度(即盐分)对土壤水同位素蒸发分馏作用的影响。在新疆炮台试验站开展了不同浓度NaCl溶液入渗和蒸发试验,研究强蒸发作用下不同矿化度土壤水中氢氧稳定同位素的动态变化特征以及盐分对土壤水同位素蒸发分馏作用的影响。结果表明:强烈的蒸发作用导致土壤水中重同位素富集,土壤水的δD-δ18O曲线斜率显著低于当地大气降水线,且随着深度的增加,土壤水的蒸发程度减弱,土壤水中氢氧稳定同位素组成趋近于当地大气降水线;盐分对土壤水分的蒸发分馏起到了明显的抑制作用,盐水灌注剖面土壤水中氢氧稳定同位素分布与天然情况存在明显差异,且随着盐分浓度的增加,土壤水中氢氧稳定同位素组成和氘盈余d值的变化幅度变小,其变化幅度亦呈现随深度增加而降低的趋势;0~30 cm深度的土壤水受蒸发分馏作用的影响大,其蒸发线方程为δD=3.5999×δ18O-54.31(R2=0.7445),对盐分较为敏感;50~120 cm深度的土壤水受蒸发分馏作用的影响较弱,其蒸发线方程为δD=7.5779×δ18O-2.6539(R2=0.8294),盐分对其影响较小。Soil water evaporation is an important part of the hydrological cycle.The effect of salinity on soil water evaporation fractionation is rarely considered in the studies of using hydrogen and oxygen stable isotopes to determine the amount of soil water evaporation.To study the dynamic variation of hydrogen and oxygen stable isotopes in soil water with different concentrations of salinity under strong evaporation and the effect of salinity on stable isotope evaporation fractionation of soil water,this paper carries out infiltration and evaporation experiments of different concentrations of NaCl solution at Paotai Experimental Station in Xinjiang.The results show that the strong evaporation leads to the enrichment of heavy isotopes in soil water,and the slope of theδD~δ18O curve is significantly lower than that of Local Meteoric Water Line(LMWL).With the increasing depth,the evaporation of soil water is decreasing and the isotope composition approaches LMWL.Salt has a significant inhibitory effect on the evaporation fractionation of soil water.The distribution of isotopes in the saline infiltrated profile is significantly different from that in the natural profile.As the salt concentration increases,the variation in the isotopic composition and the deuterium excess(d value)become smaller,and the variation also shows a decreasing tendency with increasing depth.The soil water at the depth of 0~30 cm is greatly affected by evaporation fractionation,and its evaporation line equation isδD=3.5999×δ18O-54.31(R2=0.7445),which is more sensitive to the salinity.The soil water at the depth of 50~120 cm is affected less by evaporation fractionation,and its evaporation line equation isδD=7.5779×δ18O-2.6539(R2=0.8294),and the influence of salinity is lower.

关 键 词：咸水灌溉 土壤水 氢氧稳定同位素 氘盈余 蒸发分馏作用 干旱区 

分 类 号：X143[环境科学与工程—环境科学]