湖泊蓝藻水华形成阶段沉积物磷的释放特征与机制

Lake eutrophication and algae bloom is a major global environmental problem, and phosphorus is the restrictive factor for the formation of cyanobacterial bloom. During the period of cyanobacterial bloom, high-strength release of phosphorus (P) from sediments has been observed and significantly increased the level of total P in the water column in summer, which again has an important impact on the continuing formation of cyanobacterial bloom. Characterization of the release of P from sediments and the mechanisms involved will greatly enhance the understanding of the formation mechanisms of cyanobacteria bloom. In this aspect, it is vitally important to reveal the features of the microenvironment at the sediment-water interface (SWI). . This project takes Lake Chaohu as the research object, which has cyanobacteria bloom disaster seriously. Several self-developed methods, including planar optode (PO), diffusive gradients in thin films (DGT) and 31P nuclear magnetic resonance (31P NMR), will be employed on-site to monitor the migration of P in the vicinity of the SWI during cyanobacteria blooms, based on which the release of P through the SWI will be recognized. The changes of the SWI microenvironment as well as the regeneration of sediment P will be further studied in combination with the enclosure and microcosm experiments. The mechanisms responsible for the release of P from the sediments will be finally clarified. The results of this project will develop the theory of P cycling in eutrophic lakes and deepen the understanding of the occurrence mechanism for cyanobacteria bloom.

湖泊富营养化和蓝藻水华是全球性的重大环境问题，磷是蓝藻水华形成的限制性因子。蓝藻水华形成期间，沉积物磷可发生高强度的释放，造成夏季水体总磷含量的显著升高，继而对蓝藻水华的持续暴发产生重要的影响。系统开展沉积物磷释放规律与机制的研究，将大大加深对蓝藻水华形成机理的认识；聚焦湖区现场沉积物-水界面微环境的变化，则是该研究领域取得突破的关键。.本项目以蓝藻水华灾害严重的巢湖为研究对象，依托自主发展的平面光电极（PO）、薄膜扩散梯度（DGT）和31P核磁共振（31P NMR）等先进的技术手段，现场跟踪监测蓝藻水华形成期间沉积物界面磷的迁移变化，揭示沉积物磷的释放规律，考察沉积物界面微环境的变化和沉积物磷的再生特征，结合围隔和条件因子实验，识别影响界面磷释放的关键因子，阐明沉积物磷的释放机制，为发展富营养湖泊磷循环理论、加深蓝藻水华发生机理的认识提供重要支持。

申请人围绕富营养化湖泊沉积物内源磷释放特征与影响机制这一科学问题，以磷的微尺度界面过程与机理研究为理论创新的突破点，按照“新技术-新现象-新理论”的研究思路，通过自主研发和建立多种高分辨被动获取技术，基本实现了界面磷相关信息的准确实时获取，在微尺度水平上揭示了界面磷的精细变化过程与相关机理。研究结果表明，沉积物-水界面磷释放主要受到铁的氧化还原控制，进一步发现，是微生物驱动铁的氧化还原从而控制沉积物磷的释放。另外，研究发现，沉积物内源磷释放导致蓝藻大量暴发，使得湖泊蓝藻暴发从磷限制转为氮限制，同时，蓝藻暴发也会显著影响沉积物-水界面重金属的迁移转化。上述研究成果部分填补了湖泊微尺度营养盐循环研究方法的空白，加深了对营养化湖泊沉积物内源磷释放特征与影响机制的认识，为多尺度探讨湖泊磷循环规律提供了支持。