人工模拟不同种植密度下四种水生植物的生长状况及对氮、磷的去除

Growth of Four Aquatic Plants and Their Removal of Total Nitrogen and Total Phosphorus in Eutrophication Water Under Different Plant Density:A Laboratory Experiment

水产养殖中后期(每年9—11月)是水体污染排放最严重的阶段。通过构建池塘循环水养殖湿地,利用水生植物对养殖污水进行净化,是目前国内养殖污水处理广泛应用的一种技术。选取四种水生植物(聚草、菹草、金鱼藻和浮萍),在9—11月进行为期7周的人工模拟实验,比较了不同种植密度下各种植物对氮、磷的去除效果。结果发现,在整个实验阶段,浮萍和聚草的生物量与种植时间、种植密度均呈现明显的正相关关系,并表现出对总氮和总磷良好的去除效果;金鱼藻和菹草在实验前期也表现出上述现象,但是在实验最后一周,可能由于气温下降较大,开始死亡、破败,由于生物量下降,其对总氮和总磷的去除作用也停滞。多因子分析认为,时间对生物量和对总氮、总磷的去除贡献较种植密度和种类两个因子的影响大。研究表明,温度降低造成水生植物死亡势必会影响养殖末期污水处理的能力,聚草因其高净化能力、耐低温,优于其他3种水生植物;过高的种植密度并不会带来明显的净化效果。在人工湿地中选取合适的种植品种,保持合理的种植密度,以及对过量水生植物的及时收割显得非常重要。

Aquatic plants,used to purify the waste water during fish farming period, play an important role in constructed wetlands of water circulating aquaculture pond systems. A simulated experiment was conducted from September to November for seven weeks to compare the growth of four aquatic plants, Myriophyllum spicatum, Potamogeton crispus, Lemna minor L., and Ceratophyllum demersum L., and their removal of total nitrogen and total phosphorus in eutrophication water under different plant density. Biomass of M. spicatum and L. minor L. had a significant positive correlationship with planting time and density, and showed good removals of total nitrogen and total phosphorus from water. Potamogeton crispus and C. demersum L. showed similar trends during the six weeks, but began to die and ceased removals of nitrogen and phosphorus at the 7thweek due to sharp decline in air temperature. Multifactor analysis showed that growth time contributed most to biomass and nitrogen and phosphorus removals, compared with plant density and type. These findings indicate that M. spicatum has high purifying capacity and low temperature-tolerance and is the best aquatic plant in aquaculture constructed wetlands. Maintaining appropriate plant density is also critical for purification of eutrophication water.