Effects Of Photosynthesis By Submerged Plants On Water Purification In River And Lake

Submerged plants are an essential part of a healthy water ecosystem and an important participant in the process of self-purification of contaminated water bodies.Driven by photosynthesis,submerged plants can provide dissolved oxygen to the water and absorb and remove nutrients such as nitrogen and phosphorus from the water.How to optimize submerged plants with high environmental adaptability and strong photosynthetic capacity is a key issue for researchers concerned with water ecological pollution restoration.In this paper,the common submerged plants in the Beijing area?Vallisneria natans,Potamogeton crispus,Najas marina L,and Potamogeton pectinatus L?were used as the objects.Using chlorophyll fluorescence technology,the photosynthetic fluorescence characteristics of submerged plants and the factors such as flow rate and light intensity were comparatively studied.Analysis of the potential link between the three,preferably the environment adaptability and photosynthesis ability of the submerged plant,The influence of water quality purification characteristics provides a basis for condition control and selection of submerged plants when submerged plants are used in the restoration of aquatic ecological pollution.The thesis research has obtained the following main results:?1?From the flow rate,light strength on the water plant photosynthesis fluorescence parameters:1)the increase of the appropriate flow rate is beneficial to the photosynthesis of the submerged plants,the flow rate is too large will cause coercion on the submerged plants.The flow rate is suitable for photosynthesis of submerged plants at 0.05m/s.2)1200lx and 600lx light intensity submerged plants are more suitable for photosynthesis and absorption purification,when the light intensity is too low?300lx?will cause weak light stress on the plant.3)From the correlation point of view,light strength has a greater effect on the photosynthesis fluorescence parameters of the submerged plant,the flow rate has no significant correlation with the photosynthesis parameters of the water plant,but the effect on the body water part of the physical and chemical factors(TP,TN,p H,COD_Mn,water temperature)is significant.?2?From the water quality change and the correlation of the photosynthesis parameters of the sedimentary plants:1)The concentration of TN decreased by 65%,TP concentration decreased by 95.5%,and COD_Mnconcentration increased continuously.2)The removal effect of Vallisneria natans on phosphorus in Illumination experiment,the effect of Najas marina L removal of nitrogen and phosphorus,and the removal effect of the Potamogeton pectinatus L on nitrogen were all shown as 1200lx lighting group and300lx lighting group.From the change of COD_Mnin water,the removal effect of the Potamogeton pectinatus L on COD_Mnis 300lx light group,600lx lighting group,1200lx lighting group.The removal effect of COD_Mnon Najas marina L and Vallisneria natans was not obvious.3)From the correlation point of view:the photosynthesis activity of the submerged plants in the flow rate experiment was not obviously related to the water quality parameters(TP,TN,COD_Mn),and the Potamogeton pectinatus L,Najas marina L photosynthesis fluorescence parameters in the light experiment were negatively related to the TP concentration,and there was no obvious correlation with TN and COD_Mn.?3?From the mutual influence of water physical and chemical factors:the flow rate experiment and the photometry factors(TN,TP,p H,COD_Mn,water temperature,DO)have a significant correlation,and the water quality changes are significantly affected by the action of microorganisms to remove nitrogen and phosphorus and the release of sediment.?4?From the perspective of the adaptability of the four submerged plants to the environment:the photosynthesis capacity of Najas marina L in the flow rate experiment is higher than that of Potamogeton crispus and Vallisneria natans,but the light protection capacity is weak;The adaptability to convective velocity change is strong,weak light resistance is strong,high phosphorus environment is highly resistant,high phosphorus,low temperature water environment is bad for the photosynthesis of Najas marina L,and Potamogeton pectinatus L,alkaline water environment is not conducive to the growth of Potamogeton pectinatus L and Vallisneria natans.