Removal Mechanism And Application Of Suspended Sediment And Pollutant By Macrophytes Of Constructed Flood Beaches Wetland

Ecological restoration is hotspot of study nowadays inside and outside our country.Study and ways of restoration of degenerated ecosystem and improve environment are applied widely.In allusion to degeneration and environmental characteristic of flood beaches wetland study for influence of main environmental factors to ecological restoration and wetland restoration environmental function et al can provide basis for restoration of flood beaches wetland and environmental improvement.The main points of this doctoral dissertation are listed as follows.1.The influence of soil,water level,sediment deposition and sediment-attaching to growth is studied under simulate condition in laboratory.â‘ There is remarkable relativity between germination and soil water level.The germination ratio is only 32.56%under sustaining drought condition and the ratio is 1/3 of normal condition. The average stature is 19.0cm under sustaining drought condition and the ratio is 1/3 of normal condition.Soil pollute has some influence to highness and chlorophyll content of submerged plants.Middle level pollution of soil is favorable to submerged plants.Water level has some degree influcncc to bourgcon of Acorus calamus Linn.Thc ratio of germination of Acorus calamus Linn.is only 35%under 120cmwater level.â‘¡Sedimcnt deposition can delay the germination of bud of Potamogeton crispus.Sediment deposition has no influence to bud of Potamogeton crispus,but has evident influence to biomass of single Potamogeton crispus.The biomass of single Potamogeton crispus(sediment deposition is 0.0cm) is 2.7 times(the biomass is 2.23g/single) of that sediment deposition is 5.0cm.â‘¢Sediment-attaching debase the photosynthesis and increase the MDA of Vallisneria spiralis.The structure and function of membrane may be shatter.However sediment-attaching facilitate the producc of superoxide dismutaes(SOD) and Peroxidase(POD) that clear away overfull O^2-.â‘£Feculent water has no influence to bud growth of Potamogeton crispus,but delay the germination of bud of Potamogeton crispus.Photosynthesis have remarkable difference because of feculent and this lead to distinction of growth.Potamogeton crispus has high growth speed in low level feculent water.There are many factors which influence the restoration and construction of ecosystem.Such as DO,T,depth,soil,polluted load,attachment (alga,secretion etc.) and illumination.Pilot study is applied in this dissertation in order to explain how the diaphaneity influence the restoration and construction of submerged plants.2.Decontamination of community composed by hydrophytes(emerging plants, floating-leaved plants and submerged plants) to suspended sediment and TN,TP is studied in the condition of manmade.It indicates that the result is so evident.The mechanism of decontamination is from federal action of several different hydrophytes (emerging plants,floating-leaved plants and submerged plants).The decontamination ability of hydrophytes to suspended sediment is emerging plants(36.74%)＞floating-leaved(18.38%)＞submerged plants(13.16%) and Hydrilla verticillata (14.38%)＞Vallisneria spiralis(12.80%)＞Ceratophyllum demersum(12.33%) among those submerged plants.Emerging plants have evident impact to sediment of big particle size(such as 25μm-50μm and beyond 10μm) and submerged plants more have evident impact to sediment of little particle size(such as below 2.5μm,7μm and 10μm ).In winter Potamogeton crispus can improve the diaphaneity of water by reducing concentration of sediment.Potamogeton crispus has important impact on sediment of average particle size and 10μm-25μm.In the same time,decontamination of community composed by hydrophytes(emerging plants,floating-leaved plants and submerged plants) to TN and TP is also studied.Manmade everglade can also reduce TN and TP in the course of reducing sediment.The cleaning presses to TN and TP include three aspects.Manmade everglade can reduce 34.8%of TP in 12 hours HRT and this is higher 6.61 ratio than 28.19%of the CK.To TN the number is 11.9%and this is higher 6.6 ratio than 5.3%of the CK.In winter however the Potamogeton crispus can reduce 10.83%of TP.3.Coupling or adsorption of Yangtze River sediment and different kinds of N and P as well as COD is studied in laboratory.Sediment diameter,pH, concentration of sediment,pollute degree,temperature and surge time may all influence the adsorption.The adsorption became strong when concentration of sediment or contamination increases.At the same time the minute of sediment diameter the more evident for adsorption.The adsorption capacity of sediment which the diameter is 44-55μm is two times of that for the sediment of 125-150μm.The adsorption is more evident under acid condition.The adsorption capacity is 0.85mg/g at pH=1 and the desorption capacity is 0.147mg/g at pH=13 however.The adsorption capacity for two hour is 53.14%under 25℃.4.In order to validate the conclusion of laboratory demonstration research is performed for the removal of sediment and contamination by macrophytes of constructed flood beaches wetland.Under the condition of precontract emerging plants can remove 75%sediment for the Yangtze river water(the concentrate of sediment is 130.87mg/L),and the sedimentation is 402 g/m² in 100 hours.However, the removal and sedimentation by floating-leaved is 37.8%and 271g/m².The demonstration research is high up in the pictures in some degree and this must has important guidance for ecology restore engineering.5.Hydraulic burthen or HRT is one of the very important factors in the course of reducing to sediment and TN,TP.In order to achieve more evident effect Hydraulic burthen and HRT must be controlled properly.