漂浮植物截留效应对悬浮颗粒物及污水氮转化的影响及机理研究

A large number of suspended particles in water not only have a major negative impact on the aquatic ecosystem, but also have important influence on nitrogen biogeochemical cycle process with their input process. The interception and absorption of suspended particulate matter by large floating macrophytes Eichhonia crassipes is an efficient approach to improve the transparency of polluted water bodies. However, whether and how this kind of approach affects the particulate matter itself and the nitrogen transformation remains unclear. In this project using water hyacinth as main test plant, both field study and laboratory simulation experiments will be performed. Several key techniques (e.g. Electron microscope scanning，15N natural abundance, 15N tracer method, and the analysis of microbial community structure on the surface of root-particles) will be adopted to study the changes in rhizosphere environment after using E. crassipes to intercept and adsorb water suspended particulate matter. Then we will focus on the manipulating mechanisms of the changes in rhizosphere environment on nitrogen transformation in both suspended particulate matter and water. The results would be helpful in applying E. crassipes for controlling the exogenous pollution and reducing the risk of endogenous pollution, which would provide both scientific and practical basis for the wide-spread application of E. crassipes ecological restoration technology.

水体中大量悬浮颗粒不仅对生态系统产生重大负面影响，其输入过程也对水体氮的生物地球化学循环过程产生重要影响。应用大型漂浮植物截留和吸附水体悬浮颗粒物是提高污水透明度的有效手段，但漂浮植物在截留悬浮颗粒物之后对颗粒物本身及水体中氮素转化的影响和机制并不清楚。本申请拟以漂浮植物凤眼莲为试验材料，通过野外试验和实验室模拟试验，首先，采用电镜扫描及根系-颗粒物表面微生物群落结构分析等技术，研究凤眼莲截留和吸附水体悬浮颗粒物后其根际环境特变化规律，在此基础上，采用15N自然丰度法及外源添加15N示踪法，重点研究这种根际环境变化对悬浮颗粒物本身及水体氮转化的影响及机制等。通过研究期望在阐明凤眼莲根系-悬浮颗粒形成的特殊根际特征对水体氮转化影响机理的基础上，为提高凤眼莲高效控制水体外源、內源污染风险的能力，优化凤眼莲生态修复技术提供理论参考与实践依据。

水体中大量悬浮颗粒不仅对生态系统产生重大负面影响，其输入过程也对水体氮的生物地球化学循环过程产生重要影响。应用大型漂浮植物截留和吸附水体悬浮颗粒物是提高污水透明度的有效手段，本项目通过模拟试验和原位试验研究发现，在持续进水的条件小，污水的水力负荷越小，凤眼莲对污水中的氮磷去除效果越好。凤眼莲和水浮莲两种漂浮植物对水体中的悬浮颗粒物具有较好的拦截效果，能有效降低水体中的颗粒物，提高水体透明度。凤眼莲对藻类总量的平均拦截率约为80.74%；其中对粒径>6μm的藻类拦截效果最佳，平均拦截率为87.16%；对粒径在3-6μm的藻类拦截效果次之，平均拦截率为74.7%；对粒径1-3μm的藻类的拦截效果最差，平均拦截率为68.3%。不同粒径的藻类拦截率的差别不仅跟凤眼莲根系拦截能力有关，同时也跟藻细胞的繁殖速度有关。漂浮植物利用其庞大的根系将水体中的悬浮颗粒物截留，形成了特有的根际环境，既能通过植物吸收和富集颗粒物及水体中的氮相关微生物来去除氮元素，也能截留水体中的微藻有机颗粒物，微藻死亡分解释放氮元素又会被进一步吸收，因此，漂浮植物截留悬浮颗粒物后在污水净化过程中氮元素的转化过程是一个氮的微循环过程。本研究阐明了水生植物尤其是漂浮植物拦截水体悬浮颗粒物的部分规律和机制，为漂浮植物生态修复技术的推广应用提供理论参考与实践依据。