草型生态系统构建技术在南湖富营养化防治中的应用

Application of Macrophytic Ecosystem Construction Technology for Eutrophication Prevention and Control in Nanhu Lake

水体富营养化是一个全球性的问题,生态修复是富营养化治理的主要途径之一。为了探索南宁市青秀区南湖富营养化水体治理的方法及途径,观测生态系统演变过程中水质的变化情况,利用帆布及脚手架等材料在上湖区域搭建约670 m^2、水深1.6～2.0 m的围隔试验区。清除实验区内鱼类以减少对水体的搅动,投放EM菌种增加透明度,然后种植苦草(Vallisneria natans),待沉水植物生长良好后再投放鲮(Cirrhinus molitorella)、环棱螺(Bellamya aeruginosa)、河蚌(Anodonta)等水生动物,建立新的生态系统;苦草种植密度为1.4 kg/m^2,鲮、环棱螺、河蚌的投放密度分别为6 g/m^2、10 g/m^2、1 g/m^2。结果显示,新的生态系统经过5个月构建完成并趋于稳定,试验水体水质从原来的地表Ⅴ类水提高至Ⅳ类(GB 3838-2002);透明度从0.25 m上升并稳定在1.8 m,透明度增加了6.2倍;高锰酸盐指数(COD_(Mn))从8.8 mg/L下降至2.6 mg/L,整体下降了70%;总磷(TP)从0.10 mg/L下降至0.04 mg/L,减少了60%;总氮(TN)从1.37 mg/L下降至1.17 mg/L,下降了14.5%;叶绿素a(Chl-a)从51 mg/m^3下降至4.6 mg/m^3,下降了91.1%。与整个湖区相比,试验区透明度提高了3倍以上,高锰酸盐指数降了3.7%,总磷降低了63.6%,总氮减少了4%;叶绿素a减少了89.4%。试验表明,生态修复技术能够有效控制总磷,抑制藻类生长,显著提高透明度,对富营养化水体具有很好的改善作用,可以在南湖大面积推广和实施。

Eutrophication is a global problem and ecological restoration is a primary means for managing eutrophication.Nanhu Lake is located in the core area of Nanning City,Guangxi Province.From August 2013 to February 2014,our research team conducted an ecological restoration experiment in Nanhu Lake to explore methods for treating eutrophication and the feasibility of ecological restoration in Nanhu Lake.An enclosed experimental area was set up using canvas and scaffolding in the upper lake with the area of 670 m2 and water depth of 1.6-2.0 m.Herbivorous and omnivorous fish in the enclosure were removed to reduce mixing and EM strains were used to increase transparency.The macrophyte,Vallisneria natans,was then planted at a density of 1.4 kg/m2.After vegetation coverage reached 90%,aquatic organisms,such as Cirrhinus molitorella,Bellamya aeruginosa and Anodonta were added at densities of 6 g/m2,10 g/m2 and 1 g/m2,respectively.Water quality was monitored during the experiment;water depth and temperature,air temperature and transparency of the test area and open area of Nanhu Lake were measured daily and TP,TN,CODMn and Chl-a were measured monthly in the test area and open area of Nanhu Lake.After 5 months,the newly constructed ecosystem was completed and stabilized and water quality in the test area increased from GradeⅤto GradeⅣ(GB 3838-2002).Transparency increased from 0.25 m to 1.8 m;CODMn decreased by 70%,from 8.8 mg/L to 2.6 mg/L;TP decreased by 60%,from 0.10 mg/L to 0.04 mg/L;TN decreased by 14.5%,from 1.37 mg/L to 1.17 mg/L and Chl-a decreased by 91.1%,from 51 mg/m3 to 4.6 mg/m3.Compared to the whole lake,transparency in the test area was>3 times higher,CODMn decreased by 3.7%,TP by 63.6%,TN by 4%,and Chl-a by 89.4%.Results indicate that ecological restoration effectively controlled TP,inhibited algal growth,significantly improved water transparency and effectively treated eutrophication.The process can be expanded and implemented throughout Nanhu Lake.