用镭同位素评价胶州湾水体表观年龄及地下水入海通量

为评价胶州湾水体表观年龄和地下水入海通量,2011年9—10月在胶州湾地区分别采集地下水、河水和海水样品,对水样的224Ra和226Ra活度进行测量。基于224Ra和226Ra半衰期的差异,运用224Ra与226Ra的活度比值计算了胶州湾水体表观年龄;采用三端元混合模型计算了胶州湾海水中地下水、河水与湾外海水的混合比例;在水体表观年龄和混合比例的基础上,计算了地下水入海通量。结果表明:研究期间胶州湾水体表观年龄分布范围为3.2—39.4d,平均值为14.7d,呈现从湾顶到湾口年龄逐渐增大的趋势,地下水的平均混合比例是11.0%,地下水的入海通量为7.29×106m3/d,海底地下水排泄速率为3.8cm/d。

WATER APPARENT AGES AND SUBMARINE GROUNDWATER DISCHARGE OF JIAOZHOU BAY INDICATED BY RADIUM ISOTOPE TRACERS

In order to estimate water apparent ages and submarine groundwater discharge of Jiaozhou Bay, water samples were collected from groundwater, river water and seawater around Jiaozhou Bay in September to October, 2011. Meanwhile, the activities of 224Ra and 226Ra in the water samples were measured in laboratory via emanation methods. According to the different half-time of 224Ra and 226Ra, the water apparent ages in Jiaozhou Bay were calculated using the activity ratio of 224Ra and 226Ra. A three end-member mixing model was used to estimate the relative contributions of groundwater, river water and open ocean seawater to Jiaozhou Bay. Based on the water apparent ages and the contributions of each sources, the groundwater input to the bay was calculated. The results show that the water apparent ages range from 3.2 to 39.4 d, average is 14.7 d, and the ages in the bay head are relatively younger than those in the bay mouth. The average mixing ratio of groundwater is about 11.0%, and groundwater input to the Jiaozhou Bay is 7.29×106 m3/d, SGD flow rate is 3.8cm/d.