| Water is one of the most precious resources on earth, and is the basic form of life. However, for nearly a century, with the dramatically growth of population, the rapid development of industrial and agricultural production, contaminated water containing phosphorus from agriculture, industry and life continually increasing, the backward water quality management and sewage treatment, a large number of untreated sewage is drained away directly. These have already caused serious pollution to the environment of surface water. Our country is facing more serious phosphorus pollution of fresh water resources and eutrophication of lake. Therefore, an easy-operate and low-cost method characterized with high reduction rate of phosphorus for sewage treatment and bioremediation of surface water is urgently needed. The application of aquatic macrophytes in sewage decontamination can purify polluted water and move the pollutant out of water; in addition, they assimilate nutrients into a high-quality biomass that may be processed to fertilizer, feedstuff or new energy. Because it will be a processing technology that is economical, effective and easily extended, it grabs intensive attention of the scholars everywhere.Duckweed is a small-sized floating plant. It is chosen for its rapid growth speed, its high speed of assimilation and transformation of nitrogen and phosphorus, its good endurance to various pollution, easily-gained feature and its wide application of later period exploration. This thesis elaborates on the experiments of the observation of the growth of phosphorus, the absorption rate of duckweed to phosphorus and the physical signs of duckweed. A comparison of the absorption ability toward phosphous has been made among Lemna perpusilla, Spirodela oligorrhiza and Spirodela polyrrhiza. Based on this, Spirodela polyrrhiza, which is the most effective for phosphorus absorption, is picked out as the research object to study the change of its physiology by static experiments indoors, in order to get some useful information for further application of duckweed in decontamination of nutrient elements from sewage and eutrophicated water body. The following are the results:1. All the three kinds of duckweed can grow well when the P-concentration of the nutrient solution is0.1,1.55,3.1,15.5,46.3ml/L. And they will grow better when the P-concentration of the nutrient solution is1.55,3.1,15.5mg/L. Lemna perpusilla grows best in all of the nutrient solution than Spirodela polyrrhiza and Spirodela oligorrhiza, but it has a lower efficiency in the removal rate of phosphorus than Spirodela polyrrhiza. Spirodela oligorrhiza has the lowest efficiency in the removal rate of phosphorus.2. On the whole, all the three kinds of duckweed have a higher absorption rate of phosphorus when the P-concentration of the nutrient solution is higher. When the P-concentration of the nutrient solution is93mg/L, Lemna perpusilla and Spirodela polyrrhiza’s absorption rate of phosphorus will be a little lower. When the P-concentration of the nutrient solution is15.5mg/L and46.6mg/L, Spirodela polyrrhiza has a higher absorption rate of phosphorus than Lemna perpusilla.3. Lemna perpusilla contains more protein than Spirodela polyrrhiza and Spirodela oligorrhiza. The vitality of enzyme to ACP and ATP in Spirodela polyrrhiza is higher than that in Lemna perpusilla and Spirodela oligorrhiza. When the P-concentration of the nutrient solution is higher, the vitality of enzyme to ATP in the duckweed is higher too.4. Spirodela polyrrhiza contains the most protein when the P-concentration of the nutrient solution is3.1mg/L, and it will contain less protein when the P-concentration of the nutrient solution is higher. When the P-concentration of the nutrient solution is higher, the vitality of enzyme to ATP in Spirodela polyrrhiza is higher too. The vitality of enzyme to ATP in Spirodela polyrrhiza is the highest when the P-concentration of the nutrient solution is46.5mg/L... |
PDF Full Text Request