白洋淀是雄安新区的重要生态屏障，也是大清河水系的水量调节枢纽，然而其有机污染问题不容忽视。随着入淀河流整治工程的完成，白洋淀外源污染得到有效遏制，但其内源污染，特别是沉积物有机污染问题突显，沉积物有机质释放已成为水体有机污染的主要问题。作为浅水草型湖泊，白洋淀景观类型多样、水陆交错分布、生境破碎化严重，沉积物与上覆水体之间物质交互作用强烈，不同淀区污染差异水平大。目前尚缺乏全淀范围沉积物有机质空间分布及对淀区水质影响的深入研究。因此，探明不同淀区沉积物中有机质分布特征与释放规律，对于白洋淀内源有机污染控制和湖泊水质改善具有重要意义。

本研究将白洋淀划分为八类淀区，通过现场勘测、序批实验、原位柱培养实验、柱状模拟释放实验，结合红外光谱、三维荧光光谱等分析手段，确定不同淀区沉积物和上覆水中的有机质分布特征，评价其污染风险，阐明有机质在沉积物和上覆水之间的分配特征与规律，提出解决不同淀区有机污染问题的工程建议，为白洋淀内源有机污染控制和湖泊水质提升改善提供理论依据。主要研究结论如下：

（1）探明了沉积物有机质分布特征与释放风险。不同淀区沉积物有机质浓度差异大，随深度递增逐渐减小，且主要分布在表层0~20 cm。沉积物中有机质主要表现为重组有机质、非活性有机质、颗粒态有机质。沉积物有机质主要来源于陆源C₄植物和藻类，有机污染指数平均0.755，属于中度污染水平。科学清除烧车淀荷花景观区、淀头围埝区表层0~20 cm沉积物，减少颗粒态有机质再悬浮，可以有效减小有机污染释放风险。

（2）确定了上覆水有机质分布与污染特征。白洋淀上覆水TOC平均浓度12.53 mg/L，COD平均浓度47.59 mg/ L。上覆水中有机质以溶解性有机质（DOM）为主，DOM主要组分是类酪氨酸（占比40.62%）和类色氨酸（占比41.88%），DOM来源以内源为主，自生特性明显。水生生物活性、类蛋白浓度是水体有机污染的主要影响因素。对藻苲淀芦苇生长区的大型维管束植物残体进行清除，限制颗粒态有机质输入上覆水；对南刘庄河道和枣林庄区的生活污水进行控制，减少外源溶解态有机质输入，是水质提升的关键。

（3）阐明了沉积物有机质释放过程及影响因素。沉积物向上覆水释放有机质时，其中含有-OH、-COOH、C-O、-CH₃、=CH₂官能团的物质有所减少；沉积物吸附上覆水有机质时，其中含有=CH₂、-NH₂官能团的物质有所增多。沉积物释放向上覆水释放有机质的过程中，上覆水中的类色氨酸组分显著增多。厌氧条件、高温条件、过酸或过碱环境以及外界风浪扰动，均会增多沉积物有机质释放量。其中，风浪扰动强度增强会使得大量颗粒态有机质再悬浮，相较于其他因素，对于沉积物释放有机质的影响程度最大。

（4）揭示了不同淀区沉积物的“源”“汇”特征。在柱状模拟释放实验中，白洋淀沉积物有机质扩散通量在2.001~5.304 mg/(m²×d)之间，平均值为3.438 mg/(m²×d)。当上覆水COD < 40 mg/L时，整个淀区的沉积物均为污染源；当上覆水COD介于60~80 mg/L时，烧车淀荷花景观区和枣林庄生活区的沉积物为污染源；而随着上覆水COD浓度升高，整个淀区的沉积物逐渐均转变为污染汇。

Baiyangdian Lake is an important ecological barrier in Xiong'an New Region, and it is also the water regulation hub of the Daqing River system. However, its organic pollution problem cannot be ignored. With the completion of the river remediation project into the river, the external pollution of Baiyangdian has been effectively curbed, but the problem of endogenous pollution, especially organic pollution in sediments has become prominent, and the release of organic matter in the sediments has become the main problem of water pollution. As a shallow macrophytic lake, Baiyangdian has diverse landscape types, staggered distribution of water and land, serious habitat fragmentation, strong material interaction between sediments and overlying water, and different levels of pollution in different lake regions. Currently, there is still a lack of exhaustive research on the spatial distribution of sediment organic matter in the whole lake and its impact on water quality in the lake. Therefore, it is of great significance for the control of endogenous organic pollution in Baiyangdian Lake and the improvement of lake water quality to identify the distribution characteristics and release laws of organic matter in sediments of different lake regions.

In this study, the Baiyangdian Lake was divided into eight types of lake regions. Through field surveys, sequencing batch experiments, in-situ columnar sample culture experiments, and columnar simulated release experiments, combined with FTIR, 3D-EEM and other analytical method, the distribution characteristics of organic matter in sediments and overlying water in different lake regions were determined, the pollution risk was evaluated, and the release mechanism of organic matter between sediments and overlying water were clarified. Engineering suggestions to solve the problem of organic pollution in different lake regions were put forward, which provided a theoretical basis for the control of endogenous organic pollution and the improvement of lake water quality in Baiyang Lake. The main conclusions were as follows:

(1) The distribution characteristics and release risk of sediments organic matter were ascertained. The concentration of organic matter in sediments in different lake regions varies greatly, decreases gradually with the increase of depth, and is mainly distributed in the 0-20 cm of surface sediments. The organic matter in sediments is represented by heavy fraction organic matter (HFOM), stable organic matter (SOM) and particulate organic matter (POM). Sediments organic matter mainly comes from terrestrial C₄ plants and algae, with the average organic pollution index is 0.755, belonging to the moderate pollution level. Dredging the 0-20 cm of surface sediments scientifically in the Shaochedian lotus landscape region and Diantou perimeter region, and reduce the resuspension of POM, which can reduce the release risk of organic pollution.

(2) The distribution and pollution characteristics of organic matter in overlying water were determined. The average concentration of TOC is 12.53 mg/L, and the average concentration of COD is 47.59 mg/L. The organic matter in the overlying water is mainly dissolved organic matter (DOM), and the main components of DOM are tyrosine-like (accounting for 40.62%) and tryptophan-like (accounting for 41.88%). The DOM is mainly endogenous and has obvious autogenous characteristics. Aquatic biological activities and protein-like concentration are the main influencing factors of organic pollution in water. The key to improve water quality is to salvage the large vascular plant residues in Zaozhadian reed growing region to limit the input of POM into the overlying water and control the domestic sewage in Nanliuzhuang estuary and Zaolinzhuang living regions, and reduce the input of exogenous DOM.

(3) The release mechanism and influencing factors of sediment organic matter were clarified. When the sediment releases organic matter to the overlying water, the substances containing -OH, -COOH, C-O, -CH₃, =CH₂ functional groups will decrease. When the sediment adsorbs organic matter from the overlying water, the substances containing =CH₂ and -NH₂ functional groups will increase. During the process of sediment releasing organic matter into overlying water, the tryptophan-like components in overlying water increased significantly. The anaerobic conditions, high temperature conditions, over acid or over alkali environment and external wind-wave disturbance will increase the release of organic matter in sediments. Among them, the enhancement of wind-wave disturbance intensity will resuspend a large amount of POM. Compared with other factors, it has the greatest impact on the release of organic matter from sediments.

(4) The characteristics of "source" and "sink" of sediments in different regions. In the process of columnar simulated release experiment, the organic matter diffusion flux of sediments in Baiyang Lake range from 2.001~5.304 mg/(m²×d), with an average value of 3.438 mg/(m²×d). When the COD of the overlying water is less than 40 mg/L, the sediments of the whole lake is the pollution source; when the COD of the overlying water is between 60~80 mg/L, the sediments of the Shaochedian lotus landscape region and Zaolinzhuang living region are the pollution sink. With the increase of COD concentration in the overlying water, the sediments of the whole lake are gradually transformed into pollution sinks.