Evaluation of the role of groundwater in the global water circulation using environmental tracers of natural radionuclide and dissolved noble gases.

我们通过对ANU、ETH和普渡的竞争分析，评估了使用加速器质谱仪测量深层地下水中极低浓度的^&lt；36&gt；Cl的技术。每三个实验室测得的数据对于深层非常古老的地下水测年是可以接受的。我们提出了用~(36)Cl浓度校准的超额溶解~4He浓度来测定百万年来非常古老的地下水的新方法。在此基础上，给出了利用该方法判断地层积水为化石水的标准。人类活动最重要的淡水资源是河水和浅层地下水，停留时间较短，从几个月到1000年不等。河水的基本成分是滞留时间短的渗漏地下水。已对滞留时间小于十年的年轻地下水进行了精确的~3H+~3He测年。Re是…此外，没有授权的测年技术来估计居留时间从100年到1000年。提出了一种利用Rb同位素比值及其浓度的新方法，并用已发表的浅层地下水和温泉数据进行了验证。以天然环境放射性核素和溶解惰性气体为环境示踪剂，估算了不同地下水环境中的滞留时间。我们可以将全球水循环中的地下水分为两类，一类是近十年以下的浅层淡水，另一类是非常古老的超过10^5或10^6年的咸水和死水。淡水和年轻的地下水对全球水循环的贡献很大，但咸水死水可能在其中起不到作用。然而，我们不能简单地从盆地的深度、位置和渗透率来判断地下水的运动，对于地下水循环来说，最重要的是地下水盆地的历史形成和结构。较少

We evaluated the measurement technique for ^<36>Cl with very low concentration in deep groundwater using an accelerator mass spectrometer through competitive analyses among ANU, ETH and Purdue. The data measured at every three laboratories are acceptable for very old groundwater dating in deep strata. We proposed the new method of dating for very old groundwater over one million years using excess dissolved ^4He concentration calibrated with 36Cl concentration. Furthermore, we reveal the criteria to judge stagnant water stored in strata as the fossil water using the method.The most important freshwater resources are river water and shallow groundwater with short residence time ranging from a few months to 1000 years for the human activities. Basically, the basic river water is consisted of the seepage groundwater with a short residence time. The precise ^3H+^3He dating method has already been demonstrated for young groundwater with residence time of less than some ten years. The re is … More no authorized dating technique to estimate residence time ranging from 100 years to 1000 years. We proposed the new method using the radium isotope ratio and its concentration and verified the method with the published data of shallow groundwater and hot springs collected in the past studies.We estimated the residence time in various groundwater environments using natural environmental radionuclide and dissolved noble gases as the environmental tracers. We can categorize groundwater in the global water circulation into two groups, which one is almost fresh and shallow groundwater with less than some ten years and the other is saline and stagnant water with very old over 10^5 or 10^6 years. The fresh and young groundwater is greatly contributed to the global water circulation, but saline stagnant water probably plays out of role in it. However, we can not simply judge groundwater movement from only depth, location and permeability in the basin The most important thing is the historical formation and structure of the groundwater basin for the groundwater circulation. Less