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General comment:

The paper aimed to introduce a novel extraction device (Circulating air extraction method, CAEM) capable of accurately obtaining soil water and analyzing isotopic compositions. This could significantly contribute to research on soil hydrology employing isotope techniques, given the existing techniques' weaknesses in precision. Nonetheless, I harbor two main concerns regarding this newly developed apparatus:

First, the principle of CAEM aligns with the widely-used CVE system, which separates pore water through evaporation and condensation. Its main contribution is enhancing the capability to transport water vapor using dry air. Based on current experimental data, the accuracy of soil water isotopic analysis seems to have been improved. However, the reasoning behind the increased precision is not adequately explained. Why, given the same principle applied, do the two systems (CAEM and CVE) provide vastly differing accuracies in determining soil water isotopes? These questions are not adequately addressed in the paper.

Second, soil water isotope analysis, especially for soil with high clay content and low water content, remains a critical challenge. The present study just tested CAEM's isotopic accuracy on high water content soils (>18.75%), but this alone does not warrant a definitive claim about its superiority in overall reliability and precision. Without adequate validation in low water content soils, any claims about its better performance would be baseless and illogical.

Furthermore, there are some specific comments as shown below:

Specific comments:

1. Line 99: Why choose tap water at 8°C for cooling? At this temperature, water vapor in the pipes does not fully condense, meaning some evaporated soil water remains uncollected. It might potentially affect the accuracy of isotopic analysis.。
2. Line 110: Figure 2 presents the cooling systems. The cooling pipes are connected in series with four distinct evaporation circuits. This configuration would provide better cooling for the first circuit and somewhat less effectiveness for the last one. As a result, the time required for completion of water extraction might vary among the four circuits. Is that a problem in your experiment?
3. Section 2.3：Separation pore water from soil by evaporation and recondensation involves the error of evaporation fractionation. The first thing to ensure is that the soil pore water could be completely evaporated and all water vapor would be condensed and collected. Therefore, the extraction efficiency or collection efficiency are important quantitative indicators to evaluate whether this set of procedures is qualified. Please add how to measure or calculate the extraction efficiency.
4. Line139：Why repeated drying and wetting 4 times?
5. Section 2.4：How is the soil-water mixture evenly mixed in the spiking test? If water does not uniformly moisten the soil particles, the actual soil water content will be higher than the design value.
6. Line 159: Why does it take 5 hours to extract pure water? but soil takes three hours?
7. Line 170：How to determine whether the lost water is left in the pipe wall?
8. Section 3.2：What role does the d-excess value play in your analysis?
9. Section 4.1：A comparison of the amount of water collected with the amount added should be given in order to show the air tightness.

The amount of residual water and its effect on isotope measurements are discussed here, but these statements are mainly based on qualitative descriptions, lacking quantitative evidence. Rayleigh model is proposed to quantify the effect of residual water on the isotope of extracted water. In addition, there is not even one paper cited in this section.

1. Line 237-238：How could CAEM distinguish between pools of water in soil? Its working principle is the same as CVE, but CVE is difficult to achieve such a purpose.
2. Line263：Change CVD to CVE.