In order to study the improvement of water quality by confined growth ofEichhornia crassipesand the fate of nitrogen and phosphorus in Caohai of Dianchi Lake, a pilot project with large-scale cultivation of the macrophyte, which was aimed to remove contaminants and alleviate eutrophication in Caohai, was carried out from 2011 to 2013. The project consisted of 3 procedures as follows. 1) Seedlings ofE. crassipes were cultivated in a man-made fence made of bamboos and nets. 2) After the rapid growth and propagation ofE. crassipes, the macrophyte was harvested utilizing specially designed harvestors. 3) The harvested biomass of macrophyte was crushed and squeezed, the squeeze slag was processed to make organic fertilizer or silage feed, and the squeeze juice was processed to make biogas. During the project, the concentrations of TN (total nitrogen) and TP (total phosphorus) in water at river inlets and Caohai were monitored every month. Plant samples of E. crassipeswere collected in the period of cultivation and in the period of harvest to assay the N and P contents in the plant tissue. The coverage area ofE. crassipes planted in Caohai was determined by satellite remote sensing technology, and the biomass of per unit area was measured by electronic balance in 1 m2 quadrates at 9 different sites of the plant population. Then, the total biomass of the macrophyte was calculated from the average biomass of per unit area multiplied by the coverage area. Based on the above experiment data, the balance of TN and TP loads in the lake was estimated. The results showed that the average concentrations of TN and TP in the water decreased by 51.04% and 40.00%, respectively, from 14.48 and 0.60 mg/L beforeE. crassipes cultivation (from 2006 to 2010) to 7.09 and 0.36 mg/L afterE. crassipes cultivation (from 2011 to 2013). The decreasing trend of TN and TP average concentrations from the lake inlets to the outlet of Caohai was observed, with the reduction of 9.74 mg/L TN and 0.40 mg/L TP. The balance of TN and TP loads in Caohai demonstrated that the assimilation of N and P byE. crassipes was one of important ways to remove N from the lake, and meanwhile most of the TN load into the lake (40.31%-59.04%) was removed through the nitrification/denitrification and sedimentation, and only a small proportion of TN input remained in the water as detected in the outlet water of the lake. However, the loss of TP via various ways was higher than the TP input into the lake, and 40.44%-116.56% of TP load into the lake was assimilated byE. crassipes, which indicated the P in sediment released into the lake water in the year of 2011. These results indicated that the large-scale confined growth ofE. crassipes could play a large role in water quality improvement of Caohai, and the assimilation byE. crassipes was an important way to remove TN and the main way to remove TP from the water. All the above results indicate that the large-scale cultivation ofE. crassipes to remove N and P in eutrophic waters is practicable.%为了研究凤眼莲(Eichhornia crassipes)对滇池草海水体水质改善及湖体氮、磷归趋的影响,于2011-2013年在滇池草海实施了规模化控养凤眼莲生态修复富营养化湖泊水体的试验性工程.生态工程实施期间,监测草海水体总氮(TN)和总磷(TP)浓度及分析湖体TN、TP收支平衡.结果显示,草海水体TN和TP浓度均值分别由工程实施前(2006-2010年)的14.48 mg/L和0.60 mg/L降低至工程实施期间(2011-2013年)的7.09和0.36 mg/L,分别下降了51.04%和40.00%;草海入湖水体TN和TP浓度均值由入湖河口经凤眼莲控养区至出湖口的沿程方向上分别下降了9.74和0.40 mg/L.草海湖体TN、TP收支平衡表明,经出湖口排出和水体库存的TN量占入湖TN量比例较小,凤眼莲的吸收作用是入湖TN量去除的重要途径之一,而大部分入湖TN量(40.31%~59.04%)极可能是通过微生物的硝化反硝化、沉积等作用去除;各种途径支出的TP量高于入湖TP量,其中凤眼莲吸收的TP量为入湖TP量的40.44%~116.56%.因此,规模化控养凤眼莲对草海水质改善发挥了较大作用,凤眼莲的吸收作用既是湖体TN去除的重要途径之一,又是TP去除的主要途径之一.
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