This study reports analyses of Ra isotopes in a Mediterranean stream, the Vidourle river, whose upper course drains the granitic and metamorphic basement of the SE part of the French Massif Central (Cévennes) and then flows through the karstified carbonates of Jurassic and Cretaceous ages. In these low-Ra waters (²²⁶Ra activities range from 1.5 to 4.9 mBq/L), all four Ra isotopes were successfully analyzed through gamma spectrometry during a single analysis. ²²⁶Ra activities and (²²⁸Ra/²²⁶Ra) ratios are distinctly higher in waters draining the Variscan basement than in waters affected by dissolution of Mesozoic carbonates, in agreement with U contents and Th/U ratios of both rock types. This results in a general N-S decrease, which parallels the evolution of the ⁸⁷Sr/⁸⁶Sr ratios. (²²⁸Ra/²²⁶Ra) ratios reported vs 1/(²²⁶Ra) display linear relationships suggesting mixing of several water components related to the lithology. Ra might thus have a more conservative behavior than usually assumed, possibly because of the high water/rock ratio and flow rate in karst environment. Short-lived Ra isotopes (²²⁴Ra and ²²³Ra) are often in excess compared to their equilibrium values, due to their supply through alpha-recoil processes. ²²³Ra activities in a Vidourle tributary can be explained by mixing of two water components, with a negligible radioactive decay of ²²³Ra during underground water flow. The calculated minimum flow rates (40–60 m/h) are in agreement with those deduced from artificial tracer experiments.

中文翻译：

---

镭同位素作为维杜尔河中水和混合的示踪剂（法国南部）

这项研究报告分析了地中海河流维多尔河中的Ra同位素，其上游流失了法国地块中部（塞文山脉）东南部的花岗岩和变质基底，然后流经侏罗纪和白垩纪的岩溶碳酸盐岩。在这些低Ra水域（²²⁶ Ra活度范围为1.5至4.9 mBq / L）中，在一次分析中，所有4个Ra同位素均通过伽马能谱法成功地进行了分析。²²⁶ Ra活动和（²²⁸ Ra / ²²⁶与受中生碳酸盐溶解影响的水相比，排入Variscan地下室的水的Ra）比明显更高，这与两种岩石的U含量和Th / U比一致。这导致总的NS下降，这与⁸⁷ Sr / ⁸⁶ Sr比值的变化平行。报告的（²²⁸ Ra / ²²⁶ Ra）比与（1 /（²²⁶ Ra））呈线性关系，表明几种与岩性有关的水组分混合。因此，由于岩溶环境中的高水/岩石比和高流速，Ra可能比通常的假设更为保守。短命的Ra同位素（²²⁴ Ra和²²³Ra）相对于其平衡值通常过剩，因为它们是通过α-反冲过程供应的。^223个在维杜尔河支流太阳神活动可以由两个水组分的混合，具有可忽略的放射性衰变进行说明²²³地下水流动期间镭。计算出的最小流速（40-60 m / h）与从人工示踪剂实验推导出的最小流速一致。