The Sr isotopic composition of rivers and groundwaters in the Bengal Plain is a major contributor to the global oceanic Sr inventory. The stable strontium isotope ratios (δ⁸⁸Sr) provide a new tool to identify chemical weathering reactions in terrestrial water. In this study, we investigated the spatiotemporal variations of δ⁸⁸Sr in samples of river water, bedload sediment, and groundwater collected from the Ganges–Brahmaputra–Meghna drainage basin in Bangladesh, which is known to strongly influence the ⁸⁷Sr/⁸⁶Sr ratio in seawater. The average δ⁸⁸Sr values of waters of the Ganges, Brahmaputra, and Meghna rivers were 0.269, 0.316, and 0.278‰, respectively. Our data showed little difference between seasons of high and low discharge. The δ⁸⁸Sr values measured in sequential leaching fractions of sediments varied from –0.258 to 0.516‰ and were highest in the silicate fraction, followed in turn by the carbonate fraction and the exchangeable fraction. Both ⁸⁷Sr/⁸⁶Sr and δ⁸⁸Sr of these waters are primarily controlled by the inputs of Sr in weathering products from the Bengal Plain and Sr from the Himalayan rivers (Ganges and Brahmaputra). Values of δ⁸⁸Sr and Sr/Ca were higher in the Brahmaputra River than in the Ganges River, a difference we attribute to greater input from silicate weathering. The variations of δ⁸⁸Sr and ⁸⁷Sr/⁸⁶Sr were greater in groundwater than in river waters. Mineral sorting effects and dissolution kinetics can account for the large scatter in ⁸⁷Sr/⁸⁶Sr and δ⁸⁸Sr values. The depth profile of δ⁸⁸Sr showed wide variation at shallow depths and convergence to a narrow range of about 0.31‰ at depths greater than 70 m, which reflects more complete equilibration of chemical interactions between groundwater and ambient sediments owing to the longer residence time of deeper groundwater. We found that δ⁸⁸Sr values in the groundwater of Bangladesh were almost identical to those of river water from the lower Meghna River downstream of its confluence with the Ganges–Brahmaputra river system, thus confirming that the δ⁸⁸Sr composition of the groundwater discharge to the Bay of Bengal is very similar to that of the river discharge.

孟加拉平原河流和地下水的Sr同位素组成是全球海洋Sr清单的主要贡献者。稳定锶同位素比率（δ ⁸⁸ SR）提供一种新的工具，以确定在地面的水化学风化反应。在这项研究中，我们调查δ的时空变化⁸⁸在河水，泥沙沉积物和地下水从孟加拉恒河-雅鲁藏布江-梅克纳流域，这是众所周知的收集的样品的Sr强烈影响⁸⁷ SR / ⁸⁶ Sr比值在海水中。平均δ ⁸⁸恒河，雅鲁藏布江和梅格纳河的水的Sr值分别为0.269、0.316和0.278‰。我们的数据显示高流量和低流量的季节之间差异不大。的δ ^88个在改变从-0.258到0.516‰和沉积物的连续浸出级分测定的Sr值在硅酸盐分数分别最高，其次又由碳酸酯馏分和可交换分数。两个⁸⁷ SR / ⁸⁶ Sr和δ ⁸⁸锶这些水域的主要由Sr的输入在风化从孟加拉平原产品和Sr从喜马拉雅河流（恒河和雅鲁藏布江）控制。δ值⁸⁸布拉马普特拉河中的Sr和Sr / Ca比恒河中的Sr和Sr / Ca高，这归因于硅酸盐风化作用的增加。δ的变化⁸⁸ Sr和⁸⁷ SR / ⁸⁶锶比在河水更大地下水。矿物分选效果和溶解动力学能占到在大分散⁸⁷ SR / ⁸⁶ Sr和δ ^88倍的Sr的值。深δ轮廓⁸⁸Sr在浅层深度表现出较大的变化，而在大于70 m的深度处收敛至约0.31‰的狭窄范围，这反映了由于深层地下水的停留时间较长，地下水与周围沉积物之间化学相互作用的更加完全的平衡。我们发现，δ ^88个在孟加拉国地下水锶值是几乎相同从其与恒河-雅鲁藏布江系统合流的下部梅克纳河下游河水，从而确认δ ⁸⁸地下水放电Sr的组合物孟加拉湾与河流排放非常相似。