生态塘-潜表流复合人工湿地对抚仙湖入湖河流水质净化效应及途径

Effect and Process of Ecological Pond-Submerged Surface Flow Composite Constructed Wetland on Water Quality Purification of Rivers Entering Fuxian Lake

为探明人工湿地在流域面源污染治理和高原湖泊及临湖流域水生态环境保护中的效用,本研究以尖山河流域生态塘-潜表流复合人工湿地11级功能区和4种植物为研究对象,通过测定2021年雨季6场典型降雨后各功能区污染物负荷、一个刈割周期内植物各器官及其对应土壤的氮磷含量,分析其氮磷积累量、富集系数和迁移系数的变化特点,深入探讨系统对不同面源污染物的去除效应及途径.结果表明:①生物沉砂塘对悬移质的沉积率范围为27.75%~55.00%,且逐级递减,系统对面源污染物的去除率在44.40%~78.87%之间,末端分区效果更为显著.②植物根区土壤作用(贡献率为59%~74%)是人工湿地氮去除的主要途径,植物吸收转化(贡献率为32%~42%)是磷去除的主要途径,在高污染负荷输入条件下悬移质削减率及污染物净化效应更优.③人工湿地植物营养元素的富集和株内迁移能力具有阶段性,氮、磷元素富集系数(分别为2.29~3.53、1.07~2.92)均大于1且向上迁移活跃,有利于修复环境污染.④单位面积氮磷去除速率均表现为表流湿地>潜流带状湿地,最优植物配置分别为再力花+旱伞草和香蒲+旱伞草.研究显示,合理调配土壤与植物比例及组合,高效利用不同植物配置路线对元素的敏感差异性,对入湿水体进行预处理和采用多功能、多塘系结合的人工湿地设计可稳定发挥水质净化效用.

In order to explore the effectiveness of constructed wetlands in controlling non-point source pollution in watersheds and protecting aquatic ecological environments of plateau lakes and surrounding areas,this study focuses on the ecological ponds and subsurface flow composite constructed wetlands with 11 functional zones and four plant species in the Jianshan River watershed.By measuring the pollutant loads in each functional zone after six typical rainfall events in 2021 rainy season,and the nitrogen(N)and phosphorus(P)contents in different plant organs and corresponding soils in a mowing cycle,the changes in N and P accumulation,enrichment factors and migration coefficients were analyzed.The removal effects and pathways of different non-point source pollutants by the system were thoroughly explored.The results showed that:(1)The removal rate of suspended solids by sedimentation pond gradually decreased,with an overall range of 27.75%to 55.00%.The pollutant removal rate of this system was 44.40%to 78.87%,and the effect was more significant in the terminal zones.(2)Plant-soil interaction(contributing 59%to 74%)was the main way to remove nitrogen in the constructed wetland,and plant absorption and transformation(contributing 32%to 42%)was the main way to remove phosphorus.Under high pollution load conditions,the removal rate of suspended solids and the purification effect of pollutants were more favorable.(3)The enrichment and intra-plant migration capacity of nutrient elements of the constructed wetland plants were stage-dependent.The enrichment factors of N and P(2.29 to 3.53,1.07 to 2.92)were both greater than 1,and had a tendency to migrate upward,which was beneficial for environmental restoration.(4)The removal rates of N and P per unit area of surface flow wetlands were higher than those of subsurface flow strip wetlands.The optimal plant configurations were Thalia dealbata+Cyperus alternifolius and Typha orientalis+Cyperus alternifolius,respectively.The research has shown that the water purification efficiency can be steadily improved by rationally allocating the proportion and combination of soil and plants,effectively utilizing the allocation ways of different plants(considering their sensitivity to elements),pre-treating the inflowing water,and designing multi-functional and multi-pond combination of artificial wetland systems.