The noble gas temperature climate proxy is an established tool that has previously been applied to determine the source of groundwater recharge, however, unanswered questions remain. In fractured media (e.g., volcanic islands) recharge can be so rapid that groundwater is significantly depleted in heavy noble gases, indicating that the water has retained noble gas concentrations from higher elevations. Previous studies of rain samples have confirmed a match to patterns seen in fractured-rock groundwater for heavy noble gases along with a significant helium excess. Snow has been shown to be a credible source for both the helium excess and the observed heavy noble gas pattern. Here, liquid cloud water samples were collected at two mountainous sites and analyzed for noble gas concentrations. A pattern like that of rainwater was found. However, an analysis of diffusive uptake of noble gases into cloud water demonstrates that droplets of 1 mm diameter and smaller should be in constant solubility equilibrium with the atmosphere. To explain this, we present a novel hypothesis that relies on the assumption that liquid water consists of two types of water molecule clusters bounded by hydrogen bonds: a low-density ice-like structure and a high-density condensed structure. In this model, the pressure gradient near the surface of a droplet resulting from surface tension could allow for the formation of a surface layer that is rich in ice-like low density clusters. This can explain both the helium excess and the heavy noble gas depletion seen in the samples.

中文翻译：

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液态云水中的异常稀有气体溶解度：对稀有气体温度和云物理的可能影响

惰性气体温度气候代理是一种既定的工具，以前曾用于确定地下水补给的来源，但是，仍然存在未解决的问题。在裂隙介质（例如火山岛）中，补给速度非常快，以至于地下水中重惰性气体显着耗尽，这表明水保留了来自较高海拔的惰性气体浓度。先前对雨水样本的研究已经证实，这与在裂隙岩石地下水中看到的重惰性气体以及大量氦过量的模式相匹配。雪已被证明是氦过量和观察到的重惰性气体模式的可靠来源。在这里，在两个山区收集了液态云水样本，并分析了惰性气体浓度。发现了类似雨水的图案。然而，对惰性气体扩散吸收到云水中的分析表明，直径为 1 毫米或更小的液滴应该与大气保持恒定的溶解度平衡。为了解释这一点，我们提出了一个新假设，该假设依赖于液态水由两种以氢键为边界的水分子簇组成的假设：低密度冰状结构和高密度凝聚结构。在该模型中，由表面张力引起的液滴表面附近的压力梯度可以形成富含冰状低密度簇的表面层。这可以解释样品中看到的氦过量和稀有气体严重耗尽。