Liu Shuai, Liao Lei, Liu Jing, Wei Xianglong
School of Energy and Power Engineering, Xihua University, Chengdu, 610039, China.
Key Laboratory of Fluid and Power Machinery, Xihua University, Chengdu, 610039, China.
Sci Rep. 2025 May 23;15(1):18011. doi: 10.1038/s41598-025-03255-6.
Mercury (Hg) and methylmercury (MeHg) are highly neurotoxic substances, and reservoirs play a critical role in Hg storage while providing geochemical environments conducive to MeHg production. However, the mechanisms of Hg transport and methylation during reservoir regulation remain poorly understood. This study investigates the spatial distribution of sediment Hg and MeHg in both horizontal and vertical profiles within the Nuozhadu Reservoir, located in the upper Mekong River. Using the diffusive gradients in thin films (DGT) technique, we observed that sediment Hg and MeHg concentrations initially increased and then slightly decreased from the tail to the dam front of the reservoir. This trend is primarily attributed to the transport of fine sediment particles influenced by reservoir interception. MeHg production was observed during sediment transport, but hydraulic conditions driving sediment accumulation emerged as the dominant source of sediment MeHg. Furthermore, vertical fluctuations in DGT-Hg and DGT-MeHg values were noted, likely caused by periodic reservoir operations. Our findings indicate that sediments release Hg into the overlying water, establishing sediments as a significant source of Hg pollution in reservoirs. This study enhances our understanding of Hg transport and methylation processes under the influence of reservoir regulation.
汞（Hg）和甲基汞（MeHg）是高度神经毒性物质，水库在汞储存中起着关键作用，同时提供有利于甲基汞产生的地球化学环境。然而，水库调节过程中汞的迁移和甲基化机制仍知之甚少。本研究调查了位于湄公河上游的糯扎渡水库水平和垂直剖面中沉积物汞和甲基汞的空间分布。使用薄膜扩散梯度（DGT）技术，我们观察到水库沉积物中汞和甲基汞的浓度从库尾到坝前先增加然后略有下降。这种趋势主要归因于受水库拦截影响的细颗粒沉积物的输送。在沉积物输送过程中观察到甲基汞的产生，但驱动沉积物积累的水力条件是沉积物甲基汞的主要来源。此外，还注意到DGT - Hg和DGT - MeHg值的垂直波动，这可能是由水库定期运行引起的。我们的研究结果表明，沉积物将汞释放到上覆水中，使沉积物成为水库汞污染的重要来源。本研究增进了我们对水库调节影响下汞迁移和甲基化过程的理解。
