Dissertation > Environmental science, safety science > Environmental pollution and its prevention > Water pollution and its control

Impact on Water Eutrophication of Light Rare-earth

Author LiuPei
Tutor ZhaoShiLin
School Sichuan Normal University
Course Environmental Science
Keywords rare earth complex state EDTA the alga increasing eutrophication major river in Sichuan content ranged of rare earth in solution
Type Master's thesis
Year 2008
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With rare earth trace fertilizer in agriculture broad applications, a growing number of rare earth elements into the agriculture and water ecosystems, Ree after entry to the impact of the work has been rare earth agro-technology, and rare earth biological and ecological effects of the environmental impact study in a more active, but how scientific and rational use of rare earth, give full play to their physiological ecological effects on the environment and minimize its negative effects of human systematic study very weak, only little information is vague on a number of studies into the rare earth trace fertilizer soil after crops internal systems and the distribution of agricultural ecosystems.Due to a large number of rare earth elements enter the water environment, in accordance with the theory of speculation that it can promote the growth of crops, so the elements also have the same effect on the growth of the algae ,which should be a catalyst of the eutrophication problem, In the principle of linking theory with reality, in the preparatory work on the basis of this paper, EDTA as an organic ligand ,a water environment was static simulated in laboratory, in which different concentrations of rare earth complex state single and mixed rare earth were added ,and the N, P, DO, COD content and chlorophyll-a levels of algae, algae photosynthetic rate method were analyzed regularly to study the effect of the complex rare earth elements on the growth of algae and duckweed in eutrophic water .The results showed that the addition of low concentrations of rare earth complex state single and mixed rare earth (0.15 mg / L, 0.25mg / L, 0.50mg / L) can significantly promote the growth of red duckweed and the eutrophication of the water , and with the further increase the concentration (1.0 mg / L), there is a slight inhibition to to red duckweed growth and eutrophication of water. At the same time, a comparative analysis between the complex state of rare earth elements and rare earth elements Inorganic ions proved that in low concentration, the complex state rare earth with EDTA has the greater promotion effect on the eutrophication of the water that the rare earth inorganic ions , and in higher concentrations, the inhibition is not obvious.At the same time, with the development of a wide range of rare earth fertilizer application and the improvement of the rare earth industry in Sichuan Province, more and more rare earth enter the major river systems of the Sichuan. Therefore the condition of exogenous rare earth entering the major river systems in Sichuan were studied in this paper. the soluble rare earth content of Sichuan Province of the major river systems was tested and the result showed that soluble rare earth content of rare-earth mining area rivers in Sichuan is higher than that of application of rare earth agricultural fertilizer rivers, the content lies between 10.5-173.6μg/L (summer) and 37.6-287.3μg/L (winter),which was able to promote the growth of algae and the eutrophication of the water. Because of the upper reaches where Sichuan regions is, the eutrophication potential hazards of Three Gorges Reservoir should not be ignored.

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