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地下水年龄是重要的水文地质参数,它直接揭示了地下水的循环时间和更新能力。由于不同同位素半衰期不同,导致的测年精度和范围各异,致使华北平原深层地下水年龄存在诸多争议。虽然地下水4He测年方法已经得到应用,但是对地下水中4He多种来源的认识依然不足。通过系统采集和分析华北平原保定—沧州深层地下水中惰性气体含量及其同位素组成,采用大气成因(AIR和ASW)、地壳成因(CRUST)和地幔成因(MORB)三端元混合模型进行初步判断和分离,确定深层地下水中4He是大气成因、地壳成因和地幔成因的混合,有明显的地幔来源的混入。任丘漏斗和沧州漏斗形成的汇流改变了深层地下水4He积累年龄的分布,大城东南部是它们之间的深层地下水分水岭。华北平原深层地下水的年龄可以达到127.6 ka。保定—任丘方向上深层地下水4He积累年龄不超过2 ka,黄骅—沧州方向上深层地下水4He积累年龄不超过20 ka,显示地下水有较强的更新能力;而在大城东南部形成4He积累年龄快速增大区,预示深层地下水几乎没有更新。随着任丘漏斗和沧州漏斗的持续下降,大城周围的深层地下水也将持续下降。
Groundwater age is an important hydrogeological parameter that directly reveals the cycle time and renewal capacity of groundwater. Due to the different half-lives of different isotopes, the dating accuracy and scope are different, resulting in many disputes over the age of deep groundwater in the North China Plain. Although 4He dating of groundwater has been applied, there is still insufficient understanding of the various sources of 4He in groundwater. By systematically collecting and analyzing the inert gas content and its isotopic composition in the deep groundwater of Baoding-Cangzhou in the North China Plain, three-terminal mixed model of atmospheric origin (AIR and ASW), crust formation (CRUST) and mantle origin (MORB) Separation, to determine the depth of groundwater 4He is the cause of the atmosphere, the formation of the crust and mantle cause of the mix, there are obvious mixed source of mantle. The confluence of Renqiu funnel and Cangzhou funnel changed the distribution of accumulated groundwater 4He ages, and the southeastern part of the Great Wall was the deep groundwater watershed between them. Deep groundwater in the North China Plain can reach an age of 127.6 ka. The 4He accumulation age of deep groundwater in Baoding-Renqiu direction does not exceed 2 ka. The 4He accumulation age of groundwater in Huanghua-Cangzhou direction does not exceed 20 ka, indicating a strong renewal ability of groundwater. In the southeastern part of Ayutthaya, 4He accumulation age is rapid Increasing the area indicates that deep groundwater has hardly been updated. As Renqiu funnel and Cangzhou funnel continued to decline, deep groundwater around the city will also continue to decline.