Plants Screening Of Artificial Floating Bed And Its Removal Efficiency For Nitrogen And Phosphorus In Northern China

In recent years,the problem of water eutrophication caused by nutrition such as nitrogen and phosphorus was becoming more and more serious in Northern China.Consequently,how to remove nitrogen and phosphorus from eutrophic water effectively was the key problem to be solved at present.However,artificial floating beds used for water purification were intended to remove the excess nutrients such as nitrogen and phosphorus from water bodies.And it has been widely used in Southern China.Therefore,in order to provide reference for the application of artificial floating beds in the water environmental and ecological restoration in Northern China,the simulation and in-situ experiments were conducted to screen the appropriate plants for constructing artificial floating beds.The nitrogen and phosphorus endurance capabilities,the capacities to adsorb nitrogen and phosphorus and the removal efficiencies for nitrogen and phosphorus of the Iris pseudacorus L.,Typha orientalis Presl and Lythrum salicaria L.were compared through the simulation experiments.Meanwhile,the growth conditions and the capacities to adsorb nitrogen and phosphorus of the L.salicaria,I.pseudacorus and Iris tectorum Maxim were compared through the in-situ experiment.Additionally,the water purification effect of artificial floating beds was evaluated.Firstly,the optimum concentrations of nitrate for growth of the 1.pseudacorus,T.orientalis and L.salicaria were 23.9-63.3 mg/L,42.2-63.3 mg/L and 63.3 mg/L,respectively.And the optimum concentrations of total phosphorus for growth of the I.pseudacorus,T.orientalis and L.salicaria were 12.3-20.8 mg/L,12.3 mg/L and 12.3-16.4 mg/L,respectively.Relatively,the nitrogen and phosphorus endurance capabilities of the I.Pseudacorus were stronger than that of the other two kinds of plants.In addition,the capacity to adsorb nitrogen and phosphorus of the T.orientalis was better than that of the I.pseudacorus and that of the L.salicaria.But there was no significant difference between the capacities to adsorb nitrogen and phosphorus of the I.pseudacorus and L.salicaria.Secondly,the nitrate removal rates by the I.Pseudacorus,T.orientalis and L.salicaria were 94.9-99.3%,64.4-96.7%and 95.4-99.4%,respectively.Also,the total phosphorus removal rates by the I.Pseudacorus,T.orientalis and L.salicaria were 85.1-97.8%,75.2-97.4%and 84.4-97.8%,respectively.Overall,there was no significant difference between the removal efficiencies for nitrogen and phosphorus of the I.pseudacorus and L.salicaria.However,the removal efficiency for nitrogen and phosphorus of the T.orientalis was poorer than that of the I.pseudacorus and that of the L.salicaria.Addtionally,the chroma of the experimental water planted with the T.orientalis was poor than that of experimental water planted with the I.pseudacorus or the L.salicaria.Thirdly,the L.salicaria,I.pseudacorus and I.tectorum all grew well and could over wintering safely.The nitrogen and phosphorus uptaken by the three kinds of plants were 8695.2 g and 820.9 g,respectively,within a year.Especially,the biomass of the L.salicaria was the highest among the three kinds of plants,and it had significantly(P<0.001)greater capacity to adsorb nitrogen and phosphorus than the I.pseudacorus and I.tectorum.Meanwhile,during the months of 4-9,the removal rates of total nitrogen and total phosphorus by the artificial floating beds were 65.0-89.7%and 35.0-68.9%,respectively.Moreover,the improvement of water turbidity was persistent.To summarize,the artificial floating beds constituted by the L.salicaria,I.pseudacorus,and I.tectorum played very well in both building landscape effects and purifying water quality.In the three kinds of tested plants,L.salicaria performed the best and should be adopted preferentially in constructing artificial floating beds in Northern China.In summary,L.salicaria should be adopted preferentially in constructing artificial floating beds in Northern China.Moreover,I.pseudacorus and I.tectorum also could be planted with L.salicaria together to control the eutrophication of water bodies in Northern China.