浅水湖泊沉积物的临界平衡磷浓度与其性质的关系研究

Sediment has been identified as the dominant phosphorus (P) reservoir in lake ecosystems. As a result, P exchange across the sediment water interface plays a critical role in governing dissolved phosphate concentrations in the overlying waters. The release of P from the sediments of eutrophic lakes is often associated with factors such as redox potential, iron and aluminum morphology, organic matter and P status in sediment. The successful implementation of management actions aimed at reversing lake eutrophication requires integrated approach, including quantitative assessment of sediment's role in water quality. Because lake trophic status can be substantially influenced by the release of P from the sediments,it is essential to establish the correspondence between the surficial sediments compositon and the water column P concentration. Zero equilibrium phosphorus concentration (EPC0) is pivotal parameter to measure P equilibrium in the interface between sediment and overlying water. The EPC0 measurements also contain information of sediment characteristics. By determining the EPC0, this study will be carried out to quantitatively link sediment properties with interstitial water P level. A wide range of sediment samples will be collected in Taihu Lake to obtain different sediment characteristics. Field and laboratory studies will be conducted to quantify the effect of redox potential on iron froms in sediment.Relationships between EPC0 and sediment properties are to be examined. Besides, we also reveal the interaction of interstitial water P with EPC0. The objectives of this project are to 1) investigate redox conditions of lake, sediment characteristics and the P status in interstitial water; 2) calculate degree of phosphorus saturation (DPS) based on the P, iron, aluminum, and organic matter in sediment as well as redox potential (A DPS integrates intensity factor and quantity factor of the related sediment properties, thus easily to link sediment with EPC0); and 3) estimate the relationship between EPC0 and interstitial water P concentration. This research may help to predict overlying water P behavior in the presence of easily accessible sediment variables.

沉积物对水中磷浓度上升起重要作用。沉积物释放到水中的磷主要受氧化还原电位、铁铝形态、沉积物自身磷负荷和有机质等因素制约。把沉积物的易测性质纳入到湖泊水质管理体系中是湖泊修复的现实需要。研究表明临界平衡磷浓度（EPC0）是描述磷在沉积物-水界面平衡的重要参数。本项目拟通过沉积物主要性质与EPC0的关系及EPC0与间隙水磷浓度的关系研究，达到根据沉积物性质预测沉积物对水体磷浓度影响的目的。该项目拟以典型浅水富营养化湖泊-太湖为对象，通过实地调查与室内实验相结合的方式，探明氧化还原电位对沉积物性质的影响；揭示EPC0与沉积物性质的关系；深入了解沉积物性质与间隙水磷浓度之间的相互关系。具体内容包括：1）广泛调查沉积物性质与沉积物间隙水中磷浓度；2）通过磷吸附饱和度建立EPC0与沉积物性质的关系；3）研究EPC0与间隙水磷浓度之间的关系。这方面的研究将有助于定量评估沉积物对水体磷浓度升高所起的作用。

采集太湖梅梁湾41个底泥样品，以底泥对磷的吸附为核心，同时分析了底泥的酶、重金属的空间分布。主要结果：（1）基于80天吸附和CaCl2和NaHCO3浸提结果，以等温吸附模型为基础，发展了用于预测底泥磷释放的模型，并用发表的文献进行验证，取得良好效果；（2）低浓度磷吸附结果用线性拟合，直线经过x轴求出EPC0点，发现EPC0点变异较大，与底泥的基本性质未建立显著线性关系，可能与样点数少和底泥性质相近有关；（3）比较两种底泥磷吸附对pH和离子强度的响应，离子强度对磷吸附有显著性影响。磷吸附量在梅梁湾沉积物上随离子强度增强而增加，华家池沉积物表现相反的趋势，推测梅梁湾沉积物吸附磷主要发生在双电层内层，华家池的吸附发生在外层；（4）分析底泥3种重金属的含量和空间分布，发现 Cr、Zn的含量主要受自然因素的影响，呈现出较高的相关性，Cd受人为因素的影响作用大于Cr和Zn，虽然呈现出一定的相关性，但是弱于Cr、Zn两种元素之间的相关性,表明Cr、Zn的同源性，Cd受另外因素影响；（5）脲酶、葡萄糖苷酶、碱性磷酸酶和酸性磷酸酶的变化范围大，在梅梁湾呈现东高西低的特点。通过项目资助，探讨了底泥磷固定与释放的规律，研究了影响底泥磷迁移转化的因素，可为湖泊营养化的评价和预测提供了科学依据.