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

使用天然放射性核素和溶解的惰性气体的环境示踪剂评估地下水在全球水循环中的作用。

• 批准号: 16310009
• 负责人: MAHARA Yasunori
• 金额: $ 9.34万
• 依托单位: Kyoto University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16310009/
• 关键词: Dissolved 4He concentration; ^<36>Cl concentration; Groundwater residence time; Water circulation rate; Radium isotopic ratio; Shallow groundwater; Deep groundwater; Freshwater resources; 地下滞留時間; 地下水年度測定; 溶存希ガス; 宇宙線起源核種; 塩素-36; C-14; 溶存有機物 /

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

通过<36>ANU、ETH和Purdue的竞争分析，评价了使用加速器质谱仪测量深层地下水中极低浓度^ 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。我们提出了一种新的方法，用过量溶解的^4 He浓度（用36 Cl浓度校准）来测定100万年以上非常古老的地下水的年代。利用该方法，揭示了地层中滞留水是否为化石水的判别标准，认为最重要的淡水资源是河流水和浅层地下水，人类活动对这些水的滞留时间从几个月到1000年不等。基本上，河流的基本水是由渗透的地下水组成的，其停留时间很短。精确的^3H+^3He测年方法已经在停留时间不到10年的年轻地下水中得到验证。该环 ...更多信息 没有授权的测年技术来估计停留时间从100年到1000年不等。提出了利用镭同位素比值及其浓度的新方法，并利用已发表的浅层地下水和温泉的数据进行了验证，以天然环境放射性核素和溶解惰性气体为环境示踪剂，估算了各种地下水环境中的停留时间。全球水循环中的地下水可分为两类，一类是近10年的浅淡水，另一类是10^5年或10^6年以上的咸水和滞水。地下水在全球水循环中的贡献主要是新鲜的和年轻的地下水，而含盐滞水在全球水循环中的作用可能不大，但不能简单地从地下水在盆地中的埋深、位置和渗透性来判断地下水的运动，最重要的是地下水盆地的历史形成和结构对地下水循环的影响。少