Using hydrogen and oxygen stable isotopes to estimate soil water evaporation loss under continuous evaporation conditions

Abstract

The use of hydrogen and oxygen stable isotopes in estimating soil water evaporation loss under continuous evaporation conditions is crucial for gaining insight into soil water movement processes under different conditions. In this study, via highfrequency meteorological monitoring and continuous soil water measurements, we investigated the variation of hydrogen and oxygen stable isotopes and soil water fluxes with soil depth and time for soil water at different depths under continuous evaporation conditions. The precipitation isotope δ rain and soil water flux changes were determined using the Craig-Gordon model. It was shown that the isotopic fractionation of soil water in the surface layer 0-30 cm was dominated by a gaseousdominated transport process, and that both the δ 18 O and δD values and evaporative intensity decreased with increasing soil depth. In terms of time dynamics, the evaporation loss of soil water varies continuously with seasons and is the highest during summer. The use of δ 18 O to quantify the soil water evaporation loss provides greater accuracy than that provided by δD. The relative errors in the evaporation loss calculated based on δ 18 O and δD were 13% and 34%, respectively. A sensitivity analysis of each parameter indicated that the relative error calculated by the model is primarily determined by temperature and relative humidity uncertainty. The sensitivity analysis reveals the critical evaporation intensity of soil water at various depths from unsteady to steady state evaporation. When the relative humidity changes by 1%, the evaporation loss fraction changes from 0.001 to 0.034. The results of this study are important for quantifying the soil water resources in arid and semi-arid areas without precipitation using stable isotopes of hydrogen and oxygen.

Effect of Soil Texture on Water and Salt Transport in Freeze—Thaw Soil in the Shallow Groundwater Area

“…The maximum rising height of capillary water in sandy loam, loamy sand, and sandy soil was 187 cm, 77 cm, and 60 cm, respectively, and the capillary water could reach the frozen layer. The water content of sandy loam increased at the depth of 10 to 50 cm, but decreased slightly at the depth of 0 to 10 cm under the effect of soil evaporation [46] in the process of D1 to D2 (Figure 5). On D2, the capillary water gathered at the freezing front under the blocking effect of the frozen layer [47], resulting in the greatest increment of the water content at a depth of 40 cm in the sandy loam.…”

Temperature‐humidity‐density dependent evaporation behaviour of clay and sandy clay

“…Water evaporation in soil is a typical and complex phenomenon in nature, and the evaporation process is affected by internal factors such as particle size distribution, bulk density and organic matter content as well as external factors such as air temperature, humidity and wind speed. (Choudhury et al, 2018;Cui, 2022;Li et al, 2023;Merz et al, 2018;Xiao et al, 2011;Yin et al, 2022). The soil water evaporation process plays a vital role in guiding the evolution mechanism of unsaturated soil strength, geothermal development, thermal enhanced vapour extraction and growth performance of plants (Hussary et al, 2022;Zhang et al, 2019Zhang et al, , 2021.…”