广西典型岩溶水系统环境中222Rn的分布及指示意义  

Characteristic of radon in typical karst water systems and its indicating significance in Guangxi,China

作　　者：郭芳[1] 韦丽琼 姜光辉[1] GUO Fang;WEI Li-qiong;JIANG Guang-hui(Key Laboratory of Karst Dynamics,Ministry of Natural Resources/Guangxi Zhuang Autonomous Region,Institute of Karst Geology,Chinese Academy of Geological Sciences,Guilin,541004,China)

机构地区：[1]中国地质科学院岩溶地质研究所,自然资源部、广西岩溶动力学重点实验室,广西桂林541004

出　　处：《中国环境科学》2021年第9期4294-4299,共6页China Environmental Science

基　　金：国家重点研发计划专题(2019YFC0507502-05);国家自然科学基金(41977168,41772269);广西创新驱动发展专项课题(桂科AA20161004-1)。

摘　　要：放射性同位素氡222是来源于地层中铀衰变生成的惰性元素.由于其半衰期只有3.82d,且其活度在地下水和地表水中差异显著,近年来氡在水文学中的应用日渐兴起.但^(222)Rn在岩溶环境中的分布和行为特征少有研究.以广西三个典型岩溶水系统为例,研究^(222)Rn在包气带、非饱和带和饱水带中的浓度分布和指示意义.发现^(222)Rn在上部包气带中的活度不足500Bq/m^(3),但在非饱和带中有局部异常高区,与局部小地质构造的分布有关.在饱水带中,地下水的滞留时间、不同地下水组分的混合和氡运移的距离等是导致^(222)Rn活度差异的原因.管道介质的^(222)Rn活度比裂隙介质的高;含水介质土壤覆盖层大的比土壤浅薄的普遍高.在大型岩溶水系统的排泄区,地下水补给河流,河流也可能短暂反补地下水,由于地下水和河流^(222)Rn的差异显著,^(222)Rn可能成为地下水-地表水相互作用研究的理想示踪剂.The radioactive isotope radon originates from decay of uranium in the stratum.^(222)Rn has a half-life of 3.82 days,and the activity of ^(222)Rn has significant difference in groundwater and surface water.The application of ^(222)Rn in understanding hydrological process grows quickly in recent years,while it has less study in karst environment.Three karst water systems in Guangxi were taken as examples to study the characteristic of ^(222)Rn in karst environment and its indicating meaning.It was found that the activity of ^(222)Rn was less than 500Bq/m^(3) in the upper aeration zone,while it had local anomaly high in unsaturated zone,which is related to local geological structure.In saturation zone,the residence time of groundwater,the mixing proportion of different groundwater components,and the length of the radon transport along the flow paths causes the different of ^(222)Rn activity.In general,^(222)Rn in karst conduit media is higher than that in fissure media,and ^(222)Rn in thick soil covering layer is higher than that in thin soil covering.In the discharge zone of big karst water systems,groundwater usually flows to river,and sometimes river can flow back into the spring outlet.Because the significant difference between ^(222)Rn in groundwater and surface water,^(222)Rn might be an ideal tracer of quantifying groundwater-surface water interaction.

关 键 词：岩溶环境 ^(222)Rn 地下水 水文过程 地下水-地表水的相互作用 

分 类 号：X523[环境科学与工程—环境工程]