富营养化湖泊内源DOM降解行为与积累机制研究

Dissolved organic matter (DOM) is a dominating contributor for organic pollution and is an important index for evaluation of water quality in lakes. It becomes an increasingly accepted fact that widespread increases of DOM levels occur in lakes in the northern hemisphere during the last two decades. The causes of the unexpected increases are poorly understood. Both allochthonous input from terrestrial ecosystem and autochthonous production insides lakes can lead to the increases of DOM levels. At present, the influences of allochthonous input on DOM levels have been worldwide investigated and fully clarified. However, biogeochemical processes concerning autochthonous DOM are still obscure. The present project aims to investigate the degradation behaviors and accumulation mechanisms of DOM with various autochthonous origins. This project will be performed in three typical eutrophic lakes in China, including Lake Taihu, Lake Chaohu and Lake Dianchi. Based on the modern equipment techniques, such as C/H NMR, FT-IR and D/L-animo acids, the dynamic changes of chemical composition and characteristics of DOM degradation products will be investigated. The differences in degradation behaviors among DOM with various autochthonous origins will be compared. The contributions from aquatic plants, phytoplankton, bacteria and sediment release will also be quantitatively estimated. Finally, according to the historical data of water quality parameters, the internal cycling processes and accumulation mechanisms for DOM will be clarified among different lakes. In summary, the results of our project are beneficial to improve the theory concerning biogeochemical cycling of DOM and forecast the evolution of DOM in eutrophic lakes. Importantly, our project can provide theory bases for water quality evaluation and pollution control of lake eutrophication.

溶解性有机质（DOM）是湖泊有机污染的主要组成，是水环境质量评价的重要指标。已有研究发现近二十年来北半球湖泊水体DOM浓度普遍增加，增加原因至今未有一致解释。外源输入对DOM含量影响机理与调控机制已开展大量研究，而内源DOM的生物地球化学转化过程和贡献仍认识不清。项目以我国三大国控湖泊（太湖、巢湖和滇池）为研究对象，综合运用二维碳氢核磁共振、傅里叶变换红外光谱和D/L氨基酸等有机质组成和来源研究的新技术，揭示浮游植物、水生植物、细菌和沉积物释放等不同内源DOM光降解与微生物降解机理，阐述DOM降解产物的化学结构及其动态变化规律，阐明不同来源DOM降解行为差异性并估算相对贡献份额。结合对各湖泊水质历史变化数据的综合分析，深入探讨富营养化湖泊DOM的累积规律与内部循环机制。成果有助于完善湖泊DOM生物地球化学循环理论，预测富营养化湖泊DOM 演变趋势，为湖泊富营养化评价与污染控制提供理论基础。

溶解有机质（DOM）在湖泊生态系统中发挥重要作用，外源输入对DOM含量影响机理已开展大量研究，而内源DOM的生物地球化学转化过程和贡献仍认识不清。本研究运用三维荧光光谱、核磁共振光谱、傅里叶变换红外光谱等多种技术手段综合表征不同内源来源DOM（浮游植物、水生植物等）组成与结构特征，室内模拟研究开展了不同内源DOM降解行为研究，利用多种技术对DOM降解产物的物理化学结构特征和组成的动态变化过程进行表征，并开展环境影响因素（pH值、DOC浓度、黑暗与光照条件）对DOM降解特征的影响，综合对比研究不同来源DOM 降解作用的差异性及其主要环境影响因素，多角度探讨富营养化湖泊不同内源DOM的转化行为。研究发现：环境因素（pH值、DOC浓度）对内源DOM降解产物的化学组成与光谱结构产生重要影响，因此建议对比不同来源DOM（自然水体、水生植物、藻类等）紫外光谱、三维荧光光谱和平行因子分析结果时，应监测并报告介质的pH值和DOC浓度，尽量保持一致，以保证结果的可比性。水生植物和藻类来源的DOM组分中，类蛋白质物质最易降解，受光降解和生物降解作用都较为明显，极易降解转化成芳香性较强的类富里酸物质，多糖类物质以生物降解为主，芳香类物质以及类富里酸物质受光降解影响较大，而酚类物质兼具光降解和生物降解过程。沉积物降解过程中向上覆水体释放大量类蛋白物质，而部分类蛋白转化为难降解的类富里酸物质。细菌生命活动对湖泊DOM具有重要的重塑和改造作用，导致难降解DOM被长期保存。水生植物死亡腐解、藻类生长繁殖、沉积物释放作用及细菌利用均对水体难降解DOM（类富里酸物质）的产生具有重要贡献，导致内源有机质再循环并对湖泊内源有机污染产生重要贡献。因此在湖泊富营养化治理中，应重视內源有机质的环境效应，重视沉积物以及水生植物和藻类死亡残体营养物的释放作用对富营养化的贡献。