Background and aims

‘Earth-air’ refers to air in the vadose zone (VZ). Barometric pumping results in the rising and falling of earth-air in the VZ. Earth-air vertical movement (EVM) has an important effect on water transport in the VZ. However, phreatic water is an important source of water in the Loess Plateau, the effect of earth-air on water content is unclear.

Methods

This paper aims to reveal the effect of earth-air on the water content in the VZ of loessal soil by calculating the amount of earth-air and measuring volumetric water content (VWC), temperature, and relative humidity (RH).

Results

Our results showed that the variation of the VWC in the Loess Plateau is directly proportional to the amount of EVM. It is the sum of water vapor gains and losses from earth-air. Also, the amount of water in the earth-air is positively correlated with the frequency of the fluctuations in the atmospheric pressure (AP), thickness of the loess layer, aerated porosity, and gradient of the soil water vapor concentration. The correlation of recorded every 10 min for 3 years between the calculated VWC of the soil and the monitored values is 0.76.

Conclusion

This study reveals a new way in which soil water migrates in the Loess Plateau and furthers our understanding of the spatiotemporal distribution mechanism. It also provides a scientific basis for the utilization of scarce water resources in semi-arid areas such as the Loess Plateau region.

中文翻译：

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黄土高原包气带地气对水运移的影响

 背景和目标

“地球-空气”是指包气带（VZ）中的空气。气压泵送导致 VZ 中地气的上升和下降。地空垂直运动（EVM）对 VZ 中的水输送具有重要影响。然而，潜水是黄土高原的重要水源，地气对含水量的影响尚不清楚。

 方法

本文旨在通过计算地气量并测量体积含水量（VWC）、温度和相对湿度（RH）来揭示地气对黄土VZ中含水量的影响。

 结果

我们的结果表明，黄土高原VWC的变化与EVM的量成正比。它是地球-空气中水蒸气增益和损失的总和。此外，地球-空气中的水量与大气压力（AP）波动的频率、黄土层的厚度、通气孔隙度和土壤水蒸气浓度梯度呈正相关。 3年中每10分钟记录一次的土壤VWC计算值与监测值的相关性为0.76。

 结论

该研究揭示了黄土高原土壤水分迁移的新途径，加深了人们对黄土高原土壤水分时空分布机制的认识。也为黄土高原地区等半干旱地区稀缺水资源的利用提供了科学依据。