Study On Purification Effect Of Plants On Nirtogen And Phosphorus In Eutrophic Water

In recent years, with the development of economy, China is facing more and more serious environmental pollution problems. Especially, water pollution is most closely related to the lives of the masses. China has numerous lakes and rivers which are widely distributed, including2759natural lakes with an area greater than1km2, which covers a total area of nearly91020km2, accounting for about0.95%of the land area. However, due to human and natural causes, nitrogen, phosphorus and other nutrients discharged into the lake (reservoir) are continuously increasing, leading to severe situation of lake (reservoir) aquatic environment in China and relatively serious eutrophi cation. There is a lack of per capita water resources in China, accounting for only1/4of the world’s average, while the eutrophi cation of the lake and reservoir has aggravated the status quo. Water environmental pollution has seriously affected people’s production and living. At present, principle and technology of eutrophic water remediation have become the hot spot for domestic and international environmental science and ecology. Among various means of eutrophic water remediation, purifying eutrophic water by nutrient element (N, P) absorption of plants in water has attracted great importance to domestic and foreign scientists.In this study, based on indoor culture experiments, purification effect of nine varieties of common plants in Anhui Province on nitrogen and phosphorus elements in eutrophic sewage was investigated, and the variation rules of biomass, chlorophyll content, MDA content and SOD, POD, CAT activities of some plants in water with continues high concentrations of nitrogen and phosphorus were explored, to select several plants for water eutrophi cation treatment in Anhui Province and provide the reference for bioremediation of nitrogen and phosphorus pollution in rivers and lakes of Anhui Province.(1) Nine varieties of plants adopted in this study have different degrees of purification effects on simulated sewage. Within15d, the ammonia removal efficiency of the nine varieties of plants ranged43.33%-85.64%, the removal efficiency of total nitrogen ranged31.67%-63.08%, the removal efficiency of total phosphorus ranged47.36%-89.68%; in addition, the removal efficiency of nitrogen and phosphorus elements in sewage environment with the same concentration enhanced with the extension of hydraulic retention time of plants in the sewage; to be specific, Canna indica and Ipomoea aquatica Forsk. had the best purification effect on simulated sewage.(2) Ammonia, total nitrogen and total phosphorus removal efficiency of plants in simulated sewage with different concentrations varied. Specifically, nitrogen and phosphorus removal efficiency of plants in moderate concentrations of sewage environment is higher that that in low and high concentrations of sewage environment, which might be due to that the low contents of nitrogen and phosphorus in simulated sewage with low concentrations are not conducive to the metabolism of plants, resulting in the reduction in direct absorption and indirect effects, thus affecting the removal efficiency; however, in high concentrations of simulated sewage, the high contents of nitrogen and phosphorus might have stress effect on plants, thereby affecting the purification effect of plants on sewage.(3) In eutrophic water, nitrogen and phosphorus higher than a certain concentration or sustained high nitrogen and phosphorus environment will have stress effect on plants. Specifically, the higher the contents of nitrogen and phosphorus in the environment are, the stronger the inhibition effect on SOD, POD and CAT activities will be. Plants can regulate the SOD, POD and CAT activities in a short period of time to adapt to the damages caused by environmental changes. However, the enzyme activities continued to reduce with the extension of hydraulic retention time of plants in the sewage, resulting in the accumulation of superoxide radicals and injury to plants, such as reduced plant growth rate, decreased chlorophyll content and increased MDA content. Growth and metabolism of plants were affected, which directly led to the reduced purification effect of plants on sewage.