Abstract— Uranium (U) (or U/Ca ratio) in speleothems has been suggested to be an indicator of soil humidity and effective rainfall in the Asian summer monsoon region. However, this argument has not yet been confirmed in modern cave monitoring studies. A 3-year (July 2011–August 2014) cave monitoring study was conducted to explore the seasonal variations of U in karstic waters (including cave water and river water) from Northeastern Sichuan, Central China and to gain a better understanding of the processes influencing the U variations in these waters. With the exception of some pool waters, U concentrations and U/Ca ratios of cave and river waters exhibit seasonal variations with relatively higher values occurring in the winter half year and lower values in the summer half year, anti-correlated with the seasonal variations of local rainfall amount. Soil redox conditions, which are controlled by soil moisture and hence effective precipitation, may have a significant influence on the seasonal variations of U in waters. We demonstrate that speleothem U concentrations and/or U/Ca ratios could serve as a potential proxy, at least at the study site, for the regional effective rainfall.

中文翻译：

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川东北、华中地区喀斯特水域铀的季节变化及控制机制

摘要：洞穴中的铀（U）（或 U/Ca 比）已被认为是亚洲夏季风区土壤湿度和有效降雨量的指标。然而，这一论点尚未在现代洞穴监测研究中得到证实。一项为期 3 年（2011 年 7 月至 2014 年 8 月）的洞穴监测研究旨在探索川东北、华中地区岩溶水（包括洞穴水和河水）中 U 的季节性变化，并更好地了解影响 U 的过程。这些水域中的 U 变化。除部分池水外，洞穴水和河水的 U 浓度和 U/Ca 比值呈现季节性变化，冬半年值相对较高，夏半年值较低，与季节变化反相关。当地降雨量。受土壤水分和有效降水控制的土壤氧化还原条件可能对水中 U 的季节性变化有显着影响。我们证明了洞穴中的 U 浓度和/或 U/Ca 比率可以作为区域有效降雨的潜在代理，至少在研究地点是这样。