Study On Purification Effect Of Plant Floating Bed System On Eutrophic Water In Tributary Reservoir Bay Of Three Gorges Reservoir

The Three Gorges Reservoir(TGR)has exerted huge comprehensive benefits in flood prevention,power generation,shipping,water supply,tourism,etc.,and has also caused a huge impact on the ecological environment of the TGR.After the Three Gorges Dam's periodic water storage operation,the tributary water bodies in the entire TGR area are supported by the backwater of the Yangtze River,which slows the tributary water flow velocity,weakens the water body's diffusion and exchange capacity,and causes the self-purification capacity to be greatly reduced.Nutrient substances such as nitrogen,phosphorus,and other pollutants in the water body have caused eutrophication to varying degrees in the backwater section of the tributaries of the TGR area,which provides favorable conditions for algae growth and blooms.In turn,it caused a series of ecological and environmental problems in the water body of the reservoir area.In order to solve the environmental problems caused by eutrophic waters,the control technology has gone through the process from controlling nutrients,removing algae through medicaments,to biological regulation,ecological engineering,and ecological restoration.It is roughly divided into three aspects:physical,chemical and biological measures.Ecological floating bed technology is a breakthrough water body restoration technology that is emerging in the world at present.The use of ecological floating bed technology to prevent and control eutrophication of tributary water bodies in the TGR,and exploring its repair mechanism can provide theoretical reference for large-scale water body eutrophication prevention in the TGR.In this study,a combination of indoor simulation tests and in-situ tests was used.Four economical plants were selected:Ipomoea aquatica,Ludwigia peploides,Oenanthe javanica,and Lolium perenne as the research object.From the perspective of floating-bed carrier comparison,species mix ratio,density allocation,etc.,how to effectively construct a plant-floating-bed system suitable for the tributary water body and climate environment in the reservoir area,with a view to effectively reducing the nitrogen and phosphorus nutrients in the eutrophic water body in the tributary of the reservoir area Provide theoretical and practical evidence.The main findings are as follows:1.The simulation research results show that compared with the traditional floating bed,the net floating bed is more conducive to the growth of floating bed plants,and the constructed plant-floating bed system is more ideal for the purification of eutrophic water.2.The simulation test study of plant-floating bed system construction shows:A.In the spring and summer season,when the Ludwigia peploides and Ipomoea aquatica Forsk are planted in a ratio of 1:2,both plants in the floating bed system grow well,and the total storage of nitrogen and phosphorus reached 2018.19 mg/m~2 and 149.88 mg/m~2;plants The contribution rate of nitrogen and phosphorus storage to the reduction of nitrogen and phosphorus in the water body was 53.72%and 84.01%,respectively,which was significantly higher than that of other combinations(P<0.05).B.In autumn and winter,when the Oenanthe javanica and Lolium perenne are planted in a 1:1 ratio,the total storage of nitrogen and phosphorus in plants is 1118.19 mg/m~2 and 589.88 mg/m~2,respectively.The contribution rate of nitrogen and phosphorus storage to the reduction of nitrogen and phosphorus in water is 32.59%and 83.90%respectively,ranking second and first in each floating bed system.C.When planting at a density of 96 plants/m~2,the floating bed system have the best water purification efficiency.Among them,the storage amounts of nitrogen and phosphorus in he Ludwigia peploides and Ipomoea aquatica Forsk were 8701.22 mg/m~2 and 664.33 mg/m~2,respectively,and the contribution rate of nitrogen and phosphorus absorbed by plants to the removal of nitrogen and phosphorus in water was 94.02%and 70.74%,respectively;And the storage of nitrogen and phosphorus in Oenanthe javanica and Lolium perenne reached 1401.22 mg/m~2 and634.33 mg/m~2,respectively,and the contribution of the amount of nitrogen and phosphorus absorbed by plants to the removal of nitrogen and phosphorus in water was 23.60%and 73.04%,respectively.The contribution rate is the highest.3.The Ludwigia peploides and Ipomoea aquatica Forsk floating bed system and Oenanthe javanica and Lolium perenne floating bed system constructed in the simulation test research were applied to the Huangjin River Basin of the Three Gorges Reservoir.The results of in-situ tests in spring,summer and autumn and winter showed that The system has a better purification effect on eutrophic water in the TGR.The floating bed system can significantly reduce the content of total nitrogen,nitrate nitrogen,total phosphorus,orthophosphate and chlorophyll a in the water body.At the end of the test,the nutrient index of the water body is lower than the eutrophication standard of the water body,and the water quality is improved to achieve the purpose of water purification,the purpose of water purification is achieved.Each floating bed system can significantly reduce the types and density of phytoplankton in the water body,and effectively inhibit the growth and reproduction of algae.The plants in each floating bed system grow well,the net fresh weight of the plants in each floating bed system is more than 2000 g/m~2,and good economic benefits can be obtained after harvest.In summary,the four types of economic plants in this study can better adapt to the water environment and climatic environment of the TGR,and have the purposes of effectively purifying water bodies,inhibiting the growth of algae,beautifying green areas and improving economic benefits.It can be used for the treatment of the eutrophic water body of the tributary bay of the Three Gorges reservoir area.