水深梯度对湖滨带芦苇根际有机磷的组成与转化规律的影响

Water depth is essential for plant growth and development, and the responses to water table depth gradient inversely influence environmental function and rhizosphere unique biogeochemical cycles with many chemical transformations and transport processes. Phosphorus is the key factors leading to the eutrophication of water bodies, and changes of redox heterogeneous environment in the rhizosphere of emergent macrophytes have been supposed to be vital to occurrence and transformation on various inorganic phosphorus and organic phosphorus fractionations for quite a long time. High resolution two-dimensional technology was established in phragmites australis rhizosphere by O2, Eh and pH microelectrode (10 μm distiguishability). Levels of O2, Eh, pH, phosphate and low weight molecule organic acids in rhizosphere were determined in controlled experiments, and organic phosphorus fractionations space-time distribution characteristics were also analyzed by 31P-nuclear magnetic resonance. Dissolved reactive phosphorus release rate resulted from organic phosphorus mineralization and transformation between inorganic phosphorus and organic phosphorus fractionations as well as including in between different organic phosphorus fractionation would be discussed in the present study. Rhizosphere effect and organic phosphorus transformation mechanism were argued, and it is important to enrich and improve our understanding of conventional FeOOH-PO4 physico-chemical control module, which strongly depended on pH and Eh in phosphorus cycle across overlying water-sediment interface.

水深对湖滨带湿地植物生长发育具有重要影响，其对水深梯度的响应影响其环境功能的发挥及根际微环境的生物地球化学过程。磷是水体富营养化的关键限制因子，挺水植物根-沉积物界面氧化还原异质环境变化是根际沉积物各形态的无机磷、有机磷组分赋存及其转化的重要驱动因子。利用高分辨率微电极建立芦苇根际微观尺度（10 μm）上的二维测试技术，分析受控实验中水深梯度影响下芦苇根-沉积物微界面O2、Eh、pH、磷酸酶及小分子有机酸等指标，并通过液相31P核磁共振技术探索淹水条件驱动下芦苇根际沉积物有机磷组成的时空分布特征，探明湖滨带水深梯度驱动下芦苇根际有机磷矿化释放溶解活性磷潜力以及沉积物有机磷组分之间、有机磷与无机磷之间转化一般规律，揭示淹水梯度下根际的微界面效应及其对有机磷转化的调控机理，从而丰富和完善传统沉积物-水界面磷循环主要依赖pH和Eh的非生物过程的FeOOH-PO4控制模式。

水深对湖滨带湿地植物生长发育具有重要影响，其对水深梯度的响应影响其环境功能的发挥及根际微环境的生物地球化学过程。本项目基于室内培养实验，通过利用高分辨率微电极建立芦苇根际微观尺度上的二维测试技术，分析受控实验中水深梯度影响下芦苇根-沉积物微界面 O2、 Eh、 pH等根际微环境动态特征，并通过改良的沉积物有机磷三步提取方法结合液相 31P 核磁共振技术，探索淹水条件驱动下芦苇根际沉积物有机磷组成与转化规律，结果表明：巢湖芦苇根际表层沉积物有机磷组成主要为胆碱磷酸、正磷酸单酯、正磷酸二酯中的磷脂和DNA、焦磷酸盐。与非根际沉积物相比根际中含量更高，但随水深的增加，其焦磷酸盐含量显著下降。NaOH提取液中正磷酸单酯、 胆碱磷酸、正磷酸二酯相对稳定，短时间内对水体磷没有直接的贡献。但焦磷酸盐活性较高可水解后释放进入根际溶液或上覆水体，积极参与根际磷的生物地球化学循环过程。根际沉积物中微生物在根系分泌物的诱导下，主要以磷细菌数量增加，但根际微生物多样性指数下降。 而适度水深可增加根际微生物Shannon –Wiener指数和Simpson指数，水深超过120cm则两者指数均明显下降。根际水深梯度主导根际微环境氧化还原进程，芦苇根际溶液中PO43-主要来源于沉积物中BD-P和焦磷酸盐，而非LP。PO43-的释放强度在芦苇根际沉积物较高，随水位增加的PO43-的释放通量最多可增幅40~47%。植物叶绿素光合作用受到了限制。适度的水深条件促进芦苇的生长，加强光合作用，提高根际有机磷的总体份额，提升植物抗逆性能。本研究的相关成果为进一步掌握芦苇湿地有机磷的矿化过程提供理论支撑。