The Influence Of Rare Earth On The Growth Of Eichhornia Crassipes And The Eutrophication

The eutrophication Often leads to disorder of aquatic ecosystem, reduce thespecies of aquatic organisms,and diversity is damaged in rivers, lakes, reservoirs, pondsand other waters. The harm is very serious.Many scholars study suggests that the mostdirect cause of the eutrophication is generated by the explosive growth of water plants,leading to deterioration of water quality, and ecosystem has been destroyed.Eutrophication is a very complex process, the excess nitrogen and phosphorus nutritionelements are not only factors to induce eutrophication.In appropriate synergy otherxenobiotics regulation’s synergistic effect also may cause the eutrophication.Existingstudies shows that, rare earth ions in a certain range of concentration have highly effectto promote plant growth, also have similar biological effects for the aquatic plants,suchas algae,thus the rare earth in the water may induce or accelerate the eutrophication.Sichuan is rich in rare earths. Because of mining, smelting and application, making alarge number of rare earth from the ore zone gradually transferred to other regionalenvironment, studies show that rare earth content in the catchment of the Yangtse Riverhas far beyond the average level of the world’s fresh water, rare earth concentrationclose to100ug/L in some parts of river in the dry season.The mainly rare earths in theserivers are light rare earths (La, Ce, Nd, Pr).Eichhornia crassipes is a kind of floatingaquatic plants which have a short growth cycle and breeding fast. Eichhornia crassipescan rapidly proliferatingin and covering the surface of the water in nutrient rich andslow flowing water, and then cause the eutrophication. This paper selects Eichhorniacrassipes as research object to explore the effect of rare earth on promoting the growthof Eichhornia crassipesof, and the relevant mechanism of eutrophication which maycaused by Eichhornia crassipesof, in order to provide a theoretical basis for prevent theeutrophication in the south river by study on the influence of rare earths on growth ofEichhornia crassipesof and correlative photosynthesis of calcium in Eichhornia crassipes, and the change of water quality in the static and dynamic water.The conclusions of the research in this thesis:(1) There cultured the Eichhornia crassipes by using a single rare earth (Ce3+) andmixed rare earth (Ce3+, La3+, Nd3+)in static water, to study its effect on the growthand Photosynthesis of Eichhornia crassipes.The results show that the single and mixedrare earth in optimum concentration range (0~1.2mg/L) can effectively promoteEichhornia crassipes to absorb N, P, and increase their fresh weight, the content ofchlorophyll and protein, and the activity of carbonic anhydrase, energy utilization andconversion efficiency, conducive PS Ⅱ shift to PSⅠ，enhance photosynthesis, andpromote the growth of Eichhornia crassipes; By data fitting，the concentration of therare earth is in the1.1mg/L～1.2mg/L which has the best role in promoting the growthof Eichhornia crassipes.(2) By adding rare earth Ce3+with the best promoting concentration (1.2mg/) into thenutrition liquid group without calcium, studies the influence of rare earth on correlativephotosynthesis of calcium in Eichhornia crassipesthe. The results show that rare earthions can replace or compensate for Ca2+,weaken the negative effect on calcium relatedphysiological function caused by calcium deficiency.(3) There culture Eichhornia crassipes in the static water with single and mixed rareearth elements, studies of the absorption of rare earth elements in different organs ofEichhornia crassipes. The results show that the distribution of the same rare earth in thevivo of Eichhornia crassipes is root> stem> leaf; the distribution of different rare earth(Ce3+, La3+,Nd3+) in the vivo of Eichhornia crassipes is La3+>Ce3+>Nd3+,the distributioncharacteristics in stems is Ce3+>La3+>Nd3+, the distribution in leaf is basically the same.This shows that the light rare earth ions (Ce3+, La3+, Nd3+)in Southern waters can enterinto the vivo of Eichhornia crassipes, and participate the physiological processes ofEichhornia crassipes, promote photosynthesis, growth and reproduction ofEichhornia crassipes, and thus accelerate the process of the eutrophication.(4) There culture Eichhornia crassipes in the static and dynamic water, study onchanges of water quality with different concentration of rare earth in the static anddynamic water.The results show that the rare earth can promote the Eichhornia crassipes to uptake ofN, P elements,then make its growth well, and then reduce the content of DO in water,increase the COD value of water, worsen the water quality, and then increase the degree of eutrophication.