镭同位素示踪盐湖地下水排放通量——以大柴旦盐湖为例  

Evaluation of lacustrine groundwater discharge in salt lake using radium isotopes:a case study of Da Qaidam lake

作　　者：杨英魁 何炳毅 孔凡翠[2] 沙占江 马玉军 凌智永[2] 王建萍[2] 李廷伟[2] YANG Yingkui;HE Bingyi;KONG Fancui;SHA Zhanjiang;MA Yujun;LING Zhiyong;WANG Jianping;LI Tingwei(Qinghai University,Xining,Qinghai 810016,China;Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources,Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes,Qinghai Institute of Salt Lakes,Chinese Academy of Sciences,Xining,Qinghai 810008,China;University of Chinese Academy of Science,Beijing 100049,China;Qinghai Province Key Laboratory of Physical Geography and Environmental Process,Qinghai Normal University,Xining,Qinghai 810008,China)

机构地区：[1]青海大学,青海西宁810016 [2]中国科学院青海盐湖研究所,中国科学院盐湖资源综合高效利用重点实验室,青海省盐湖地质与环境重点实验室,青海西宁810008 [3]中国科学院大学,北京100049 [4]青海师范大学地理科学学院,青海省自然地理与环境过程重点实验室,青藏高原地表过程与生态保育教育部重点实验室,青海西宁810008

出　　处：《地质学报》2021年第7期2238-2248,共11页Acta Geologica Sinica

基　　金：中国科学院青年创新促进会项目(编号2018468);国家自然科学基金项目(编号41702268);青海科技厅项目(编号2020-ZJ-974Q、2021-ZJ-755);2019年度“高层次留学人才回国资助联合资助”;中国科学院重点部署项目(编号ZDRW-ZS-2020-3);第二次青藏高原综合科学考察研究项目(编号2019QZKK0805)联合资助的成果。

摘　　要：为了解大柴旦盐湖地下水排放通量,测试了深部热水、浅层地下水、河流水、盐湖表层水中镭同位素((223)^Ra、(224)^Ra、(226)^Ra和(228)^Ra)的活度值。研究结果表明湖水中(223)^Ra、(224)^Ra、(226)^Ra和(228)^Ra的活度值,在盐度较低时随着盐度的增加而升高,当盐度大于168.99‰时,则随着盐度的增加而降低,这是由于在靠近河口区湖中镭同位素先发生解吸,蒸发后期湖中镭同位素发生了共沉淀的原因。(223)^Ra、(224)^Ra和(228)^Ra的活度值在深部地下热水比在自然露头热水中高;而(226)^Ra正好相反,自然露头地下热水中(226)^Ra具有明显的积累现象。丰水期深部地下热水、浅层地下水和河流三个端元对大柴旦湖中镭同位素贡献比例分别为0.01、0.31和0.68。水体平均停留时间是9.13 d。由深部地下热水排放到大柴旦的通量变化范围为1.17×10^(3)±2.021.31×10^(3)±10.17 m^(3)/d,平均为1.24×10^(3)±12.20 m^(3)/d,浅层地下水排放通量变化范围为1.58×10^(6)±4.92×10^(3)2.61×10^(6)±2.71×10^(4)m^(3)/d,平均为2.09×10^(6)±3.20×10^(4)m^(3)/d。本研究将为盐湖中地下水排放示踪提供一种有效的方法。In order to understand Lacustrine Groundwater Discharge(LGD)in the Da Qaidamsalt lake,the radium isotopes activity value of brine,deep hydrothermal groundwater,shallow groundwater water,and river water were measured.The results showed that the activity value of ^(223)Ra,^(224)Ra,^(226)Ra and ^(228)Ra of lake water increase with increasing salinity,followed by a decrease when salinity exceeds 168.99‰,suggesting that radium was desorbed when groundwater or river water met salt lake water at beginning,and radium was co-precipitated at a later stage in salt lake evolution.The activity value of ^(223)Ra,^(224)Ra and ^(228)Ra in deep hydrothermal groundwater are higher than that in the natural outcrop hydrothermal groundwater.However,226Ra activity shows antipodalvalues,and there is an obvious accumulation phenomenon in the surface hydrothermal groundwater.The fraction of deep hydrothermal groundwater,shallow groundwater and river water are 0.01,0.31 and 0.68,respectively.The radium apparent ages ranged from 2.24 to 18.65 d with an average 9.13 d in the lake water.LGD was estimated with radium inventory model,leading to a deep LGD and shallow LGD estimate of 1.24×10^(3)±12.20 m^(3)/d and 2.09×10^(6)±3.20×10^(4) m^(3)/d,respectively.This work provides an effective method for evaluating lacustrine groundwater discharge in a salt lake.

关 键 词：镭同位素 深部热水 浅层地下水 地下水排放通量 大柴旦盐湖 

分 类 号：P641[天文地球—地质矿产勘探]