Purpose

Internal phosphorus (P) input has been proven to be an important cause of eutrophication. The purpose of this study is to explore the process and mechanism of P release from sediments in seasonal hypoxic reservoirs.

Material and methods

Six sediment cores were collected from Hongfeng Reservoir, one of the largest reservoirs in southwestern China. Incubation experiments were conducted using the sediment cores under aerobic and anaerobic conditions. The diffusion gradients in thin films (DGT) technique was employed to determine the concentration profiles and release characteristics of labile-P and labile-Fe at the sediment–water interface. The microbial community structure in surface sediments was determined by 16S rRNA sequencing.

Results and discussion

Compared with the aerobic condition, the P release flux was ~3.75 times under anaerobic condition, which mainly came from BD-P and NaOH-P. In addition, DGT-P and DGT-Fe were significantly positively correlated (R² > 0.66, p < 0.001). From 16S rRNA sequencing, SRB and PSB were shown to promote P release through sulfate reduction and P dissolution in sediments. Moreover, the control measures of internal P release are discussed due to the potential risk of it in deep-water reservoirs.

Conclusion

Dissolved oxygen is the key control factor of P release; thus, anaerobic conditions promoted the release of P from sediments. Fe-P reduction and dissolution are the main processes. SRB and PSB played an important role in the P cycle of sediments. It is necessary to increase oxygen in seasonal hypoxic reservoirs to reduce the risk of internal P release.

中文翻译：

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季节性缺氧水库沉积物中磷释放的通量及其释放机理：基于模拟的实验研究

目的

内部磷（P）输入已被证明是富营养化的重要原因。这项研究的目的是探讨季节性缺氧储层中磷从沉积物中释放的过程和机理。

材料与方法

从西南地区最大的水库之一的洪峰水库收集了六个沉积物岩心。使用好氧和厌氧条件下的沉积物核心进行孵化实验。薄膜中的扩散梯度（DGT）技术用于确定沉积物-水界面处的不稳定P和不稳定Fe的浓度分布和释放特征。通过16S rRNA测序确定表面沉积物中的微生物群落结构。

结果和讨论

与好氧条件相比，厌氧条件下P释放通量约为3.75倍，主要来自BD-P和NaOH-P。此外，DGT-P和DGT-Fe呈显着正相关（R ² > 0.66，p <0.001）。通过16S rRNA测序，显示SRB和PSB通过硫酸盐还原和P在沉积物中的溶解来促进P的释放。此外，由于在深水水库中存在内部P释放的潜在风险，因此讨论了内部P释放的控制措施。

结论

溶解氧是磷释放的关键控制因素。因此，厌氧条件促进了磷从沉积物中的释放。Fe-P的还原和溶解是主要过程。SRB和PSB在沉积物的P循环中起着重要作用。有必要增加季节性缺氧水库中的氧气，以减少内部P释放的风险。