Submarine groundwater discharge is recognized as a major source of chemicals to the global ocean, exerting large control over coastal water composition. Radon and ²²⁶Ra are used to evaluate, for the first time, the occurrence and magnitude of submarine groundwater discharge in the Ría de Vigo, a large, highly productive embayment affected by seasonal, wind-driven upwelling. The system is naturally enriched in ²²²Rn due to the regional granitic basement geology: high ²²²Rn activities (up to 10⁶ Bq m⁻³) are detected in wells and boreholes in the drainage basin of the embayment. High ²²²Rn activities (>400 Bq m⁻³) are also measured in certain areas of the embayment. Comparatively lower ²²⁶Ra activities (<4 10³ Bq m⁻³) were measured in the freshwater sources to the bay. Mass balances obtained with a box model are used to perform a volumetric estimate of fresh and saline submarine groundwater discharge in the Ría de Vigo under contrasting circulation patterns. Fresh groundwater is shown to be a relevant hydrological component of the Ria de Vigo water balance, equivalent to 9% ± 4% and 23% ± 9% of the volume discharged by tributary rivers during winter and summer, respectively. On the other hand, recirculation of seawater through permeable sediments is capable of filtering the entire upper volume of the Ria de Vigo through its seafloor in <100 days and might thus be a previously overlooked major source of regenerated solutes to the system.

中文翻译：

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受季节性上升流影响的大型沿海入口的淡水和咸水海底地下水排放

海底地下水排放被认为是全球海洋化学物质的主要来源，对沿海水的成分施加了很大的控制。氡和²²⁶ Ra 首次用于评估 Ría de Vigo 海底地下水排放的发生和大小，这是一个受季节性风驱动上升流影响的大型高产海湾。由于区域性花岗岩基底地质，该系统自然富含²²² Rn：在海湾流域盆地的井和钻孔中检测到高²²² Rn 活动（高达 10 ⁶  Bq m ^-3）。高²²² Rn 活性（>400 Bq m ^-3) 也在海湾的某些区域进行测量。相对较低的²²⁶ Ra 活性 (<4 10 ³  Bq m ^-3) 是在海湾的淡水源中测量的。使用箱式模型获得的质量平衡用于在对比循环模式下对 Ría de Vigo 的淡水和咸水海底地下水排放进行体积估计。新鲜地下水被证明是 Ria de Vigo 水平衡的相关水文组成部分，分别相当于冬季和夏季支流河流排放量的 9% ± 4% 和 23% ± 9%。另一方面，海水通过可渗透沉积物的再循环能够在 <100 天内通过其海底过滤整个 Ria de Vigo 的上部体积，因此可能是以前被忽视的系统再生溶质的主要来源。