封闭式精养池塘N、P营养盐的自净作用研究

Research on the Self-cleaning Mechanisms for Nitrogen and Phosphorus Nutrients in Farming Ponds

以珠江三角洲的精养池塘为例，通过对一个养殖周期的水质和生产情况调查，计算了N、P营养盐的平衡收支情况，获得了养殖池塘N、P营养盐的净沉积速率，在此基础上分析了浮游植物对N、P吸收、底泥的吸附沉淀和底泥一水界面营养盐的扩散在池塘自净作用中的贡献。结果表明：养殖池塘N营养盐的自净作用主要来自浮游植物的吸收，强度达到0．35g／（m^2·d），扩散作用也是N营养盐的重要的自净机制，其强度与水体-底泥间隙水中的N营养盐浓度梯度相关，在优质鱼养殖池塘，扩散作用强度达到0．42—0．49g／（m^2·d），而在家鱼养殖池塘，呈现出反向的扩散，强度为0．02～0．10g／（m^2·d）。养殖池塘P营养盐的自净作用来自浮游植物的吸收、底泥的吸附沉淀，二者的强度分别达到0．049g／（m^2·d）、0．04～0．12g／（m^2·d），二者之和一般大于养殖鱼类无机P排泄速度0．079g／（m^2·d），底泥的P释放是维持水质稳定的重要过程，在观测的池塘中，P释放强度达到0．019～0．068g／（m^2·d）。

Nitrogen and phosphorus budgets were made in fanning ponds in Pearl River Delta. According to the budgets the net deposited rate of nitrogen and phosphorus was calculated and the contributions made by phytoplankton assimilation, sedimentation of clay and nutrients diffusion between the interface of water and bottom were analyzed. Results showed that ： phytoplankton assimilation was the main self-cleaning mechanism for nitrogenous compounds, which was 0. 35 g/（ m^2 · d） ; nitrogen diffusion between the interface of water and bottom was also an important process for self-cleaning, which was related to the gradient of nutrients concentrations in water and in the bottom. In high quality fish pond, the rate was 0. 42 0.49 g/（ m^2 · d） , and in common fish pond, the rate was 0. 02 ～0. 10 g/（ m^2 · d）. Phytoplankton assimilation and clay sedimentation were two important self-cleaning mechanisms for phosphate, which were 0. 049 g/（ m^2 · d）and 0.04 0. 12 g/（m^2 · d） respectively. Rate of phosphate release was 0. 019 -0. 068 g/（ m^2 · d）, which helped to maintain the self-cleaning process.