用镭同位素评价海水滞留时间及海底地下水排泄  

Utility of Radium Isotopes for Evaluating Residence Time and Submarine Groundwater Discharge

作　　者：刘花台[1] 郭占荣[1] 袁晓婕[1] 李开培[1] 章斌[1] 

机构地区：[1]厦门大学环境与生态学院,福建厦门361005

出　　处：《地球科学（中国地质大学学报）》2013年第3期599-606,共8页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金项目(Nos.40672166;41072174)

摘　　要：海底地下水排泄(submarine groundwater discharge,SGD)难以直接测量,镭同位素和氡-222等天然示踪剂使得间接评价SGD通量成为可能.为了评价五缘湾的水体滞留时间和SGD通量,实测了湾内海水、湾外海水和地下水中224Ra和226Ra的活度,利用224Ra和226Ra半衰期的差异,采用224Ra与226Ra的活度比值计算湾内水团的年龄和平均滞留时间,利用224Ra和226Ra的质量平衡模型计算SGD通量.五缘湾13个站位的水团年龄在0.6～2.4d之间,湾顶水团年龄相对较大,平均海水滞留时间1.4d.地下水输入五缘湾的224Ra和226Ra通量分别为5.17×106Bq/d和5.28×106Bq/d,将该通量用地下水端元的活度转换成为SGD通量分别是0.21m3/m2/d(224Ra平衡模型)和0.23m3/m2/d(226Ra平衡模型),两种模型的结果较接近,其平均值0.22m3/m2/d可作为五缘湾的海底地下水排泄通量.It＇s very difficult to measure submarine groundwater discharge （SGD） directly, but naturallyoccurring radium iso- topes and radon tracers make it possible to estimate SGD fluxes indirectly. In order to evaluate the residence time of seawater and SGD fluxes in Wuyuan Bay, Xiamen, China, we measured the 224 Ra and 226 Ra activities in the bay water, open ocean sea- water and groundwater, calculated the water parcel ages and average residence time in the Bay based on the differences in half- life between 224Ra and 226Ra, and estimated the SGD fluxes via the mass balance on 224Ra and 226Ra. The water parcel ages range from 0. 6 to 2.4 d among thirteen sampling stations, with an average residence time of 1.4 d. The water parcel ages in the bay head relatively get older than those in the bay mouth. The calculated 224Ra and 226Ra fluxes driven by SGD are 5. 17 × 106 Bq/d and 5.28 × 106 Bq/d, respectively. Both radium fluxes are further converted into SGD fluxes by dividing the activities of groundwater end-member to be 0. 21 m3/mz/d （zz4 Ra mass balance model） and 0. 23 m3/mZ/d （226 Ra mass balance model）, respectively. The calculated results from two models are so close that their average of 0. 22 m3/mz/d can be considered as SGD fluxes in Wuyuan Bay.

关 键 词：海底地下水排泄 海水 镭同位素 滞留时间 五缘湾 水文地质 

分 类 号：P641[天文地球—地质矿产勘探]