生态坝对湖泊养殖污染控制与生态修复的协同作用机制研究

Aquaculture is the fastest growing food industry in China. However, it brings serious environmental pollution, which is considered as one of the main reason resulting in the eutrophication of shallow lakes. In resent years, aquaculture has be limited greatly by the government. So it needs to develop the technologies with dual function of the resources utilzation and ecological environment protection. For this purpose, the pricinple of ecological dam is proposed for in situ pollution control and remediation of the polluted water. Ecological dam consists of ecological floating bed and immobilized biological media. The polluted aquaculture area is surrounded by series of ecological dam devices which are connected each other. The diversity of population can be formed in ecological dam, including bacteria, fungi, protozoa, metazoan, planktonic animal. The pollutants will be degraded by microorganisms attached on the immobilized biological media. Nitrogen and phosphorus can also be absorbed by the aqua plants in ecological floating bed. The most important characteristcs of ecological dam is that it can realise the recycle and reuse of pollutants through the food chain in the ecosystem. So the unused bait which is normally considered as pollutants can be furtherly utilzed as the food of the aquatic animal. In addition, ecological dam has the advantages of alleviating the disturbance for the sediment caused by wind and wave, and of preventing the algae bloom from entering into the area of ecological dam. However the mechanisms of ecological dam for the pollution control and ecological remediation is not very clear, including the hydrodynamic characteristic caused by ecological dams, the change of environmental factors, the migration and diffusion mechanism of pollutants in ecological dam, the degradation mechanisms of the pollutants, the mechanisms of synergistic effects of ecosystem for the recycle and reuse of pollutants, the optimization of the physical model, as well as the evaluation of ecological dam. For these purposes, four models including hydrodynamic model, diffusion and degradation model of pollutants, ecological model and physical model, will be established to describe the mechanisms of ecological dam for the pollution control and remediation of lake aquqculture water. These theoretical basis will be also useful if the ecological dam is used in other aquaculture water such as pond aquaculture, reservoir aquaculture and mariculture.

湖泊养殖是重要的经济产业，也是造成水体富营养化的主要原因，因此，实现资源利用和环境保护双重目标具有重要意义。为此，本研究提出生态坝技术原理，包括污染控制模式和生态修复模式。生态坝是由生态浮床和高效固定化生物填料组成的透水围坝，其最大特点在于，运用生态学原理，实现对污染的综合生物修复，以及利用食物链实现对物质的循环利用。当污染物经过生态坝时，部分得到分解，部分随着生态系统食物链迁移，最终进入养殖生态系统，被再次利用，同时达到污染控制的目的。在污染养殖水体构建生态坝，可以实现生态修复目的，恢复坝区水体的生态功能。然而，关于生态坝生态系统的协同作用机制，还需要深入的机理研究。因此，本研究针对湖泊养殖的污染控制和生态修复，分别设计构建生态坝模型，研究其水动力特性及环境因子的变化机制，污染物的扩散与降解动力学机制，生态系统对物质循环利用的协同机制，以及生态坝的物理模型与生态功能评价机制。

湖泊养殖是重要的经济产业，也是造成水体富营养化的主要原因，因此，实现资源利用和环境保护双重目标具有重要意义。本研究基于生态学原理，提出生态坝技术，对湖泊养殖污染进行原位生物修复。生态坝是由填料浮床和植物浮床组成的透水围坝，当污染物经过生态坝时得到分解，并随生态系统食物链实现循环利用。在阳澄湖大闸蟹养殖区构建生态坝模型装置，研究其环境因子和水质变化，填料浮床生物膜微生物对污染物的转化机制，植物浮床水生植物对氮磷营养盐的去除机制，底泥污染特征和养殖污染负荷研究，以及生态坝的优化设计和评价。结果表明：（1）养殖周期内（3-10月份），pH值平均维持在8-9之间，溶解氧水平较高（底部也多在5-7mg/L以上），水温多数时间均可维持在20℃以上；（2）生态坝对养殖水体有明显的净化作用，但受到湖泊水力交换的影响，装置内外水质差异小，无法反映生态坝的净化能力；（3）填料浮床的微生物VSS/SS平均为0.337，和传统生物处理相比呈现较低的水平，但各功能菌的生物活性良好，好氧异养菌(ODB)、氨氧化菌（AOB）, 亚硝化氧化菌（NOB）和反硝化菌（DNB）去除活性分别为 0.609 kg COD/(m2.d)、0.512 kg NH4 -N/(m2.d)、0.482 kg NO2 -N/(m2.d)和0.112 kg NO3 -N/(m2.d)；（4）16S rRNA高通量测序表明：生态坝填料生物膜具有复杂而稳定的细菌群落结构，含有各种类型的功能菌；（5）水生植物TN、TP去除能力分别为0.006 g /m2•d和0.67 mg /m2•d，硝铵比是重要影响因素；（6）养殖底泥TC、TN和TP的含量分别为36.91 g.kg-1，3.61 g.kg-1和1.50 g.kg-1，水化硅酸钙能有效固定底泥磷，并有利于沉水植物吸收磷；（7）养殖区由饵料输入产生的氮磷污染释放分别为45.53μg.(L.d )-1，4.70 μg.(L.d )-1，其中饵料残留的贡献最大，分别79.90%和83.83%，大闸蟹排泄为15.47%和14.47%，底泥释放为4.63%和1.70%；得出一个大闸蟹养殖周期产生内氮、磷污染负荷分别为68.29 mg.(m2.d)-1、7.05 mg.(m2.d)-1；（8）针对养殖区面积6667m2，计算得到生态坝面积1904 m2，占养殖区面积的28.5%。