海水网箱养殖区有机质降解对沉积物中磷迁移转化的影响研究

The excessive import of phosphate into water has become one of the most important reason for eutrophication. In the marine cage culture, the decomposition of organic matter, such as feed and fish manure will promote the release of phosphate in the sediment and lead to eutrophication over a long period of time. The aim of the research is to study the effect of the organic matter decomposition on the transformation of phosphorus in the sediments of the mariculture areas. The combination of stable isotope, fluorescence spectroscopy, fourier transform infrared spectroscopy and chemical analysis are used to investigate the characteristic and the distribution of organic matter, humic substance and phosphorus in the field sampling in marine cage culture area and to find the relationship between organic matter and speciation of phosphorus. Laboratory simulation is carried out to investigate the organic matter degradation kinetics and the phosphate release kinetics in the sediment, and the relationship between organic matter degradation and changes of the speciation of phosphorus. The results will be helpful to the understanding of the transformation of phosphorus in the sediment and the phosphorus pollution control in the marine cage culture area.

富营养化已成为目前我国面临的最为严重的水环境问题之一，其本质在于磷等营养盐的过量输入导致生态系统发生一系列剧变。海水网箱养殖中以残饵和鱼类粪便为重要组成部分的有机质大量富集、降解会使海水水质在较长时期内处于富营养化状态。针对该现象，本项目通过野外采样调查分析和室内模拟实验相结合的研究方法，利用稳定碳氮同位素、荧光光谱、红外光谱和化学分析等技术手段，系统研究网箱养殖有机质降解对沉积物磷迁移转化的影响，明确网箱养殖区沉积物磷的赋存形态特征及与有机质的耦合关系，阐明网箱养殖区有机质降解及磷素释放动力学特征，有机质降解过程中磷的沉积特征，探讨有机质降解对沉积物磷迁移转化的驱动作用，揭示海水网箱养殖区沉积物中磷的累积、释放机理，为养殖环境的评估和修复提供重要的科学依据。

海水网箱养殖大量的有机质输入及降解势必会对沉积物磷的迁移转化产生重要影响。然而，目前对海水网箱养殖区沉积物有机质降解动力学过程及其对磷迁移转化的驱动作用与机制认识还较为有限。本项目通过野外调查和室内模拟研究相结合，分析了不同养殖区有机质和磷形态的分布特征与空间分异，研究结果显示，与非养殖区沉积物各磷形态含量相比，鲈鱼养殖和牡蛎养殖均显著提高了各磷形态含量。随着离网箱养殖距离的增加，各形态磷含量明显降低，当达到500m时，各形态磷浓度已接近非养殖区。沉积物中的磷主要以钙镁结合态为主，其次为残渣态，然后为铁铝结合态、不稳定无机磷等。室内模拟实验研究结果显示，静态反应前后，沉积物中不稳态无机磷、不稳态有机磷、铁铝结合态磷以及腐殖质磷含量将有不同程度减少。这些磷除部分释放进入上覆水外，大部分转化为较为稳定的磷形态（钙镁结合态、较稳定的有机态）存储在沉积物中。这个过程主要集中发生在前30天。而海水盐度的增加一定程度的减缓了静态反应过程中各磷形态之间的转化。本研究揭示了网箱养殖区沉积物磷的赋存形态特征及其与有机质的耦合关系，阐明了有机质降解过程中沉积物磷的释放规律和沉积特征以及动态变化过程，对深入认识海水网箱养殖所带来的富营养化问题的过程与机制具有重要意义。