多源~4He及其积累年龄揭示的深层地下水更新能力——以保定—沧州剖面为例  

~4He Variety and Its Accumulation Age Reveal the Renewal Ability of Groundwater——A Case Study of Baoding to Cangzhou Profile

作　　者：毛绪美[1] 梁杏[1] 王凤林[1] 韩庆之[1] 

机构地区：[1]中国地质大学(武汉)环境学院,湖北武汉430074

出　　处：《地球科学进展》2011年第4期417-425,共9页Advances in Earth Science

基　　金：国家自然科学基金青年科学基金项目"深层地下水惰性气体法同时定量恢复气温和降雨量研究"(编号:40602031);国家重点基础研究发展计划项目"华北平原地下水演变机制与调控"(编号:2010CB428802);中央高校基本科研业务费专项资金项目"He-Ne同位素体系确定低渗透性含水层古老地下水年龄研究"(编号:CUGL090213)资助

摘　　要：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 hydrogeologic parameter for it reveals the circulation and renewal ability of groundwater.There has been great discrepancy to deep groundwater age of North China Plain dating with different isotopes,as the precision and range are disagreed to different isotopes with different half lives when groundwater is dated.Though 4He is applied in dating groundwater,it still need to recognize the variety of 4He sources.Deep groundwater samples were collected along Baoding to Cangzhou profile in North China Plain,and the concentrations and isotopic composition of noble gas were measured.Judging and separating by three end-members mixing model of atmospheric source（AIR and ASW）,crustal source and mantle source,respectively,4He of deep groundwater were mixture of these three sources with obvious mantle He.The distribution of deep groundwater 4He accumulation age was changed by conflux of Renqiu funnel and Cangzhou funnel,and groundwater watershed occurred in southeast Dacheng between the two funnels where the oldest groundwater age was to 127.6 ka.It showed good renewal ability of deep groundwater to the directions of Baoding-Renqiu and Huanghua Cangzhou with the 4He accumulation age no more than 2ka and 20ka respectively,but there were almost no renewal in southeast Dacheng for where the 4He accumulation age of deep groundwater became much older than that somewhere else abnormally.Therefore,deep groundwater will descend continually near Dacheng when Renqiu funnel and Cangzhou funnel keep extended.

关 键 词：4He来源 4He积累年龄 地下水分水岭 更新能力 深层地下水 

分 类 号：P641.12[天文地球—地质矿产勘探]