Study On Nitrogen And Phosphorus Purification Efficiency And Quality Changes In Eutrophic Water Of Two Kinds Of Vegetables

Water eutrophication has become a global environmental problem.One effective and eco-friendly solution is to use the phytoremediation.However,at present,plants used for phytoextraction show many defects including inedible and poor economic performance,etc.Therefore,searching for edible and high economically beneficial vegetables has become a hotspot.In this study,Amaranthus tricolor L.and Spinacia oleracea L.were used as the experimental materials,a floating bed cultivation was conducted to investigate the purification capacity and mechanism to N and P by two kinds of vegetables in three kinds of eutrophic water.Furthermore,we researched their physiological response and quality in eutrophic water,aiming to explore the ability to repair eutrophic water by vegetables.The main results showed that:（1）After planting amaranth and spinach,NH₄⁺-N,NO₃^--N,and PO₄^3--P concentrations decreased rapidly in eutrophic water with the increase of N and P concentration in eutrophic water.At the end of the experiment,the removal rates of NH₄⁺-N,NO₃^--N,and PO₄^3--P with amaranth and spinach were 98.20%-98.60%,72.95%-84.42%,89.63%-90.66%,and 100%,72.88%-88.71%,82.85%-91.82%respectively.NH₄⁺-N,NO₃^--N and PO₄^3--P concentrations in the control were also decreased,but the reduction was significantly lower than that of planting vegetables.The results showed that amaranth and spinach had better removal effect to N and P.（2）TN contribution rate by amaranth showed a trend of increasing at first and then decline with the increase of N and P concentration in eutrophic water,while TP contribution rate by amaranth decreased gradually,which was 38.17%-43.99%and43.15%-58.02%,respectively.TN and TP contribution rate by spinach increased gradually with the increase of N and P concentrations in eutrophic waters,and they were48.12%-89.90%and 58.80%-69.73%respectively.It indicated that the removal proportion of N and P in eutrophic water by assimilation pathway of amaranth and spinach was high.（3）Amaranth grew in eutrophic water for 30 days,TN was reduced from moderate eutrophication to V water standard,TP was reduced from severe eutrophication to type IV water standard in T1 treatment.In other treatments,TN and TP were all reduced from severe eutrophication to moderate eutrophication level.After spinach grew 30 days in eutrophic water,TN was reduced from moderate eutrophication to III water standard,TP was reduced from severe eutrophication to moderate eutrophication level in T1 treatment.TN and TP in T2 treatment were dropped to IV water standard,and TN and TP in T3treatment were dropped to moderate eutrophication.The water quality has been greatly improved.（4）The biomass of amaranth and spinach increased significantly in eutrophic water.At the end of the experiment,the fresh weight of amaranth was 1.76-2.10 times higher to initial fresh weight,and spinach was 6.20,6.29 and 7.87 times respectively,indicated that two kinds of vegetables could grow normally in eutrophic water.（5）The root activity of amaranth was not significantly different from that of control,and the root activity of spinach was significantly lower than that of control,which indicated that the amaranth’s root was not affected,but spinach’s root was affected.The activities of SOD,POD and CAT in amaranth was higher,and the activities of SOD,POD,CAT and APX in spinach was higher in eutrophic water,and MDA content in two kinds of vegetables were remain at a lower level,indicated that the physiological metabolism of amaranth and spinach was exuberant.（6）The carotenoids content of amaranth,and the chlorophyll content of spinach were not significantly different from that of control,and the leaves of amaranth were red and the leaves of spinach were bright green,indicated that the appearance quality of the two kinds of vegetables have not been affected.The synthesis of soluble protein in amaranth and spinach was affected in eutrophic water,but the soluble sugar content was significantly higher than that of control,and VC content was not significantly different from control,indicated that the nutritional quality of the two kinds of vegetables was less affected.The content of nitrite and heavy metal in amaranth and spinach were did not exceed the national sanitary standard,and the hygienic quality of the two kinds of vegetables was qualified.In summary,amaranth and spinach had a certain purification effect on N and P in eutrophic water.The assimilation and absorption pathway by amaranth and spinach can effectively remove N and P in water.The two kinds of vegetables can grow normally in eutrophic water and had strong physiological metabolism,and their appearance quality,nutritional quality and hygienic quality were all good.They were suitable for restoration of eutrophic water.