湖泊沉积物有机质降解过程磷和碳的释放行为差异与生态环境效应

Hongfeng Lake, located in Guizhou Province, is selected to carry out a comprehensive investigation on the ratios of Corg:Porg of particle organic matter in the water column, and profile variations of organic carbon content, organic phosphorus content and their ratios in the sediments under different redox conditions, with an aim of revealing the difference of regeneration behaviors between phosphorus and carbon during the degradation of sediment organic matter. Sediment trap is used to collect deposited particle organic matter and obtain the deposition rates of organic carbon and organic phosphorus. According to the vertical profile variations of organic carbon content, organic phosphorus content in the sediments and dating results by radionuclides, the burial rates of organic carbon and organic phosphorus are calculated. Furthermore, the burial efficiency (burial rate/deposition rate), recycling percentage of organic carbon and organic phosphorus are studied comparatively. Contributions of organic matter degradation to phosphorus loadings and lake eutrophication are evaluated quantitatively. This study will lay a sound foundation for planning the internal phosphorus control measures and restoration strategy of lake eutrophication.

选取贵州红枫湖为研究对象，率先系统开展不同含氧条件下湖泊水体颗粒态有机质Corg:Porg比值和沉积物柱芯有机碳、有机磷及其Corg:Porg比值剖面变化的对比研究，阐明湖泊水体和沉积物有机质降解过程中磷和碳的释放行为差异。在此基础上，利用沉积物捕获器收集沉降颗粒物质并研究获取有机碳、有机磷沉积速率（deposition rate），根据沉积物有机碳、有机磷剖面变化和放射性核素计年结果，研究确定沉积物有机碳、有机磷埋藏速率（burial rate），揭示不同含氧条件下沉积物有机碳、有机磷的埋藏效率（burial rate/deposition rate）、释放强度与生态环境效应，定量评估沉积物有机质降解释放的磷对湖泊水体磷负荷和富营养化的贡献，为制定合理的湖泊沉积物内源磷控制措施和富营养化防控策略提供科学依据。

选取红枫湖为研究对象，根据红枫湖水体深度和表层沉积物有机质含量，在全湖共布设了6个采样点，分别在夏季和冬季分层收集了湖水、颗粒物和沉积物样品。利用多功能水质参数仪（YSI）测定了水体深度、温度、溶解氧、电导率、pH等环境参数。对水体、颗粒物及沉积物样品进行了不同形态的碳氮磷含量及比值综合对比分析。研究结果表明，悬浮颗粒物的TOC/P比值明显低于表层沉积物，率先发现淡水湖泊体系颗粒物降解过程中P相对于C优先再生。根据水体颗粒物和表层沉积物TOC/P比值的差异，研究确定红枫湖沉降颗粒物和沉积物每年释放约25.1 t P。通过冬夏两季底部水体颗粒物与表层20cm沉积物有机碳和有机磷平均值的对比，发现红枫湖有机磷的埋藏效率（~34%）显著低于有机碳的埋藏效率（~78%）。红枫湖沉积物柱芯的研究结果也显示，有机质在早期矿化过程中磷较碳优先释放，且有机质降解释放的磷是湖泊内源磷最主要的来源。研究提出亚深水湖泊存在“水体缺氧→沉积物内源磷释放增强→初级生产力提高→水体缺氧加剧”的正反馈效应。本项目研究结果为认识湖泊磷的循环提供了新的视野，为制定合理的沉积物内源磷控制措施和富营养化防控策略提供了科学依据。