Submarine groundwater discharge (SGD) is an important component of the marine ⁸⁷Sr/⁸⁶Sr budget, which is currently in an imbalance with a missing source. In this contribution, dissolved Sr concentrations and ⁸⁷Sr/⁸⁶Sr of the Chilika lagoon (India), the largest brackish-water lagoon in Asia, have been investigated for three different seasons (pre-monsoon (May 2017), monsoon (Aug., 2017) and post-monsoon (Jan., 2018)) to infer coastal behavior of Sr and estimate the SGD fluxes to the coastal ocean. Major source waters (groundwater, river and seawater) and suspended sediments from the lagoon system have also been analyzed for source characterization. Salinity and Sr concentrations of the Chilika samples show wide variations during pre-monsoon (0.2–35.8; 1–93 μmol/kg), monsoon (0.1–20.1; 0.8–55 μmol/kg) and post-monsoon (0.3–7.7; 1–20 μmol/kg) seasons. Despite of these variations, salinity and Sr concentrations of the lagoon co-vary linearly as expected for conservative mixing between river and seawater. In contrast, the mixing plot between 1/Sr and ⁸⁷Sr/⁸⁶Sr during the monsoon and pre-monsoon seasons deviate from the river-seawater mixing trend, indicating an additional source/sink of ⁸⁷Sr to this lagoon. The non-conservative behavior of ⁸⁷Sr/⁸⁶Sr during monsoon has largely been restricted to low salinity (< ~2) regime, which could be attributed to subsurface ion-exchange process. During the pre-monsoon, the SGD can explain the non-conservative isotopic behavior that requires additional water supply with higher ⁸⁷Sr/⁸⁶Sr ratios. The SGD fluxes have been estimated using two separate approaches, (i) using an inverse model with fixed SGD composition and (ii) using a source-mixing computation using variable SGD compositions within the lagoon. These computations estimate that the SGD contributes ~20% of total water supplied to the Chilika lagoon during the pre-monsoon season. This SGD contribution corresponds to a flux of 1.51 × 10⁶ m³/d to the lagoon. Data from this and earlier studies indicate that the ⁸⁷Sr/⁸⁶Sr ratios of the SGD to the western Bay of Bengal, which receives water from several large rivers from the Himalaya and Peninsular Indian regions, are relatively higher (~0.715) than the seawater value (0.7092). The SGD flux to the east coast of India, therefore, would not contribute in reducing the oceanic imbalance, which requires a less-radiogenic source.

海底地下水排放（SGD）是海洋⁸⁷ Sr / ⁸⁶ Sr预算的重要组成部分，目前预算不平衡，缺少水源。在此贡献中，溶解的Sr浓度和⁸⁷ Sr / ⁸⁶已对亚洲最大的微咸水泻湖奇里卡泻湖（印度）的Sr进行了三个不同季节的调查（季风前（2017年5月），季风（2017年8月）和季风后（2018年1月）。 ））推断Sr的沿海行为并估算SGD流入沿海海洋的通量。还对主要的源水（地下水，河流和海水）和泻湖系统中的悬浮沉积物进行了分析，以进行源表征。Chilika样品的盐度和Sr浓度在季风前（0.2–35.8; 1–93μmol/ kg），季风（0.1–20.1; 0.8–55μmol/ kg）和季风后（0.3–7.7; 1–20μmol/ kg）季节。尽管存在这些变化，但咸水和海水中的Sr浓度却线性变化，这是河流与海水之间保守混合所期望的。相反，1 / Sr和季风和季风前季节的⁸⁷ Sr / ⁸⁶ Sr偏离了河水与海水的混合趋势，表明该泻湖增加了⁸⁷ Sr的水源/汇。季风期间⁸⁷ Sr / ⁸⁶ Sr的非保守行为在很大程度上受制于低盐度（<〜2）体制，这可能归因于地下离子交换过程。在季风前，SGD可以解释非保守的同位素行为，即需要额外的水供应更高的⁸⁷ Sr / ⁸⁶锶比。已经使用两种单独的方法估算了SGD通量，（i）使用具有固定SGD组成的逆模型，以及（ii）使用泻湖内使用可变SGD组成的源混合计算。这些计算估计，SGD贡献了季风前季节供应给Chilika泻湖的总水量的20％。SGD的贡献相当于通向泻湖的流量为1.51×10 ⁶  m ³ / d。这项研究和早期研究的数据表明⁸⁷ Sr / ⁸⁶SGD与孟加拉湾西湾的Sr比率相对高于海水值（0.7092），后者来自喜马拉雅山和印度半岛地区的几条大河。因此，SGD流入印度东海岸将无助于减少海洋失衡，而海洋失衡需要放射源较少。