巢湖流域源头溪流氮磷滞留机制及实验操纵模拟研究

Headwater stream has been considered an important part of river, lake and reservoir systems, and its retention capacity for nitrogen and phosphate is of great significance to regulate and reduce the effect of nitrogen and phosphorus pollution on the downstream water quality. Due to the shortage of current researches on the mechanisms of nutrient retention in headwater streams and the practical necessary of water environment protection and non-point pollution control in China, we attempt to explore the mechanisms of nitrogen and phosphorus retention and to conduct research on experimental manipulations in diverse headwater streams in Chaohu Lake basin. On the basis of field tracer experiments, three main subjects are designed to study in this project. The first is to analyze the solute retention capacity of transient storage and the characteristics of nitrogen and phosphorus retention in headwater streams. The second is to explore the basic principles and mechanisms of nitrogen and phosphorus retention in headwater streams, based on quantifying the percentage of nutrient physical uptake at the main channel and at the transient storage zone, the amount of biological uptake by the denitrification and by the nitrification and biological assimilation, and the bulk of total uptake in physical retention and in biological retention, and quantifying the uptake kinetics from ambient to saturation in successive stream reaches. The last subject is to propose effective technology to increase the practical nutrient retention capacity of headwater streams through different experimental manipulations. To be sure, the study results in this project not only can provide a theoretical basis and technical support for the reduction and regulation of nitrogen and phosphorus loadings in the river systems around Chaohu Lake, but also can be used for reference to other domestic water systems.

源头溪流是河流、湖库水系统的重要组成部分，其具有的氮磷滞留和调节功能对于调控和减轻下游水体氮磷污染具有非常重要的意义。基于国内源头溪流氮磷营养盐滞留机制研究的不足和水环境保护与非点源污染控制的实际需要，以巢湖环湖河流水系为对象，针对多种土地利用类型，筛选代表性源头溪流，开展氮磷滞留特征、滞留机制和滞留能力调控的实验操纵模拟研究。在现场示踪实验基础上，分析源头溪流暂态存储能力和氮磷滞留特征；定量估算主流区流动水体与暂态存储区对于氮磷滞留的相对贡献，硝化、反硝化及生物同化吸收作用的相对贡献，以及物理滞留与生物滞留的相对贡献水平，并通过营养盐吸收动力学模拟，解析源头溪流氮磷滞留的基本机制和原理；借助人工操纵模拟实验，探索恢复和提升源头溪流氮磷滞留能力的技术方法。研究成果不仅可以为巢湖环湖河流水系氮磷入湖负荷的削减和调控提供理论依据和技术支持，对国内外其它河湖水系水环境保护也具有指导和借鉴价值。

源头溪流是河流水系的重要组成部分，各等级小河流携带的氮磷污染物经逐级汇流、传输而进入下游水体，从而影响水体水质和水生态系统。本项目以巢湖流域多条源头溪流为对象，针对多种土地利用类型，筛选代表性源头溪流，开展了氮磷滞留特征、滞留机制和滞留能力调控的实验操纵模拟研究，相关成果可以为巢湖流域氮磷入湖负荷的削减和调控提供理论依据和技术支持，对国内其他河湖水系水环境保护同样具有借鉴价值。. 针对城市郊区、农业区源头溪流，在现场示踪实验基础上，采用暂态存储指标定量刻画溪流暂态存储潜力，解析芦苇占优势溪流沟渠和深潭地貌特征显著沟渠的暂态存储能力、特征及其变化性，并对城郊重污染溪流开展相关问题的研究。结果发现，芦苇占优势溪流沟渠和河床地貌复杂溪流沟渠都具有较大的暂态存储潜力。采用OTIS模型模拟和养分螺旋原理相结合的技术手段，解析农业小溪流及受城市污水厂尾水影响源头溪流的氮磷滞留能力、特征及其变化性，结果发现大型水生植物和河床地貌复杂性有利于氮磷滞留。针对芦苇占优势溪流沟渠的研究发现，主流区流动水体和暂态存储区对于NH4+滞留的平均贡献率分别为43.12%、56.88%；对于SRP滞留的平均贡献率分别50.13%、49.87%。此外，针对芦苇占优势农田溪流，还估算了营养盐滞留的水文和生物贡献。本项目针对城市地区和农业地区的多条溪流沟渠，开展了沉积物硝化反硝化潜力及其时空变化特征分析，定量评估了沉积物磷的生物和非生物吸收潜力，确定了各自所占比例。 . 此外，本项目开展了农业排水沟渠硝态氮吸收动力学特征分析、水文变化条件下农田溪流营养盐滞留效应模拟以及氮磷耦合吸收效应的动力学模拟，结论都表明有必要从溪流形态和河床地貌特征的改造着手，提升溪流水体营养盐滞留能力。针对农田溪流深潭地貌格局营养盐滞留及对人为干扰响应的研究，表明人为干扰对于提高农田溪流深潭地貌格局的营养盐滞留能力是可行和有效的。