Tolerance And Removal Performance Of Three Submerged Plants To Nitrogen And Phosphorus In Polluted Water Bodies

This paper is aimed at the current status of water pollution(inferior V water quality)and water ecological degradation in Shale Reservoir,Beijing.Three common submerged plants,Ceratophyllum demersum,Myriophyllum spicatum and Rhododendron chinensis,were screened and tested for water tolerance.The tolerance of three submerged plants to different forms of nitrogen and phosphorus in water was investigated.At the same time,the removal efficiency of submerged plants to the COD,nitrogen and phosphorus in the Shahe reservoir was studied to verify the possibility of using three submerged plants as water quality improvement for Shahe Reservoir.The main research results are as follows:First,the tolerance of three submerged plants to different forms of nitrogen in water distribution can be expressed as Hydrilla verticillata>Myriophyllum sp.>Ceratophyllum.The tolerance range is mainly that when the concentration of NH4+-N was less than 3 mg/L,all three submerged plants grew well.When the concentration of NH4+-N was between 3 and 5 mg/L,the genus Ceratophyllum and Myriophyllum sp.began to be stressed,and the Hydrilla verticillata still grew normally.As the NH4+-N concentration rose to 8 mg/L,the growth of the three submerged plants was stressed.NO3--N has little effect on the growth of three submerged plants.When the concentration of NO3--N was 8 mg/L,the growth of C.elegans and Myriophyllum sp.was only under stress,and the growth of Hydrilla verticillata was not affected.From the monitoring of the water quality of the Shahe Reservoir,it is found that the different forms of nitrogen in the water body rarely exceed the concentration range of the above-mentioned plants,Therefore,different forms of nitrogen in the reservoir will not cause stress on the growth of three submeiged plants.Secondly,TP also has an effect on the growth of three submerged plants.The tolerance of three submerged plants to TP in tee reservoir was Hydrilla verticillata? Ceratophyllum sp>Myriophyllum spicatum.The tolerance range is mainly as follows:when the IP concentration in the water was less than 0.2 mg/L,the three submerged plants had better growth effects.When the concentration of TP was nore than 0.4 mg/L,the Hydrilla verticillata was stressed to a certain extent,and the growth of Myriophyllum spicatum was the most stressful,followed by goldfish algae.When the concentration of TP was 0.6 mg/L,the stress on the growth of three submerged plants increased.Since the TP concentration in the Shahe Reservoir is in range of 0.2-0.6 mg/L throughout the year,the TP in the reservoir will have a certain degree of influence on the growth of submerged plants.Finally,the removal efficiency of carbon,nitrogen and phosphorus in the actual water of Shahe Reservoir by three submerged plants was investigated.The results showed that the removal of TN by three submerced plants was mainly to remove NH4+-N,and the removal rate of NH4+-N could reach more than 95%.However,the removal effect of NO3--N is very low.At the same time,the removal performance of TP is also obvious,and the removal rate is nearly 90%.After adding submerged plants,the removal of COD in water can reach about 45%.The removal rate of COD after adding submerged plants is 10%higher than that of submerged plants.In summary,it can be seen that the three submerged plants have a certain degree of improvement on the water quality of the Shahe Reservoir.