The Effects Of Organic Matter On Phosphorus Distribution Characteristic In Sediment-Water-Plant System

Lake eutrophication is one of the most important environmental problems in our country. When the input of contamination was cut off, nutrient release from sediments would cause the lake eutrophication. So sediment is the keystone in the treatment of lake eutrophication. And phosphorus is one of the important effect factors inducing the lake eutrophication, therefore, researches about distribution and transform of phosphorus among shallow lakes, adsorption and release between the sediment, the overlying water and hydrophytes, and the main effect factors are of most significance. What has been done in this paper is one part of a key project financed by the government of our country, and the serial number of this project is 2002CB412304. Distribution characteristic of OM and the effect mechanism of OM on phosphorus adsorption/release of sediment in shallow lakes were investigated, especially discussed the effect of OM on phosphorus distribution character in sediment-water-plant system. The main findings are as following:(1) Distribution of total organic matters (OM), Labile organic matter (LOM), dissolved organic matter (DOM), Light fraction organic matter(LFOM), Heavy fraction organic matter(HFOM), Humic(HA), Fulvic(FA),and Humin(HM) on the sediments from shallow lakes in the middle and lower reaches of the Yangtze River were investigated by using physical chemistry methods .The result showed: Contents of OM of 11lake sediment samples of the studied region were 9.80-110.04 g/kg, In the present study that city lake sediments>natural lake sediments of the composition and total content of organic matter in the sediments of shallow lakes and lower reaches of Yangtze River; The DOM UV-Vis absorbance, Showing the humification level of DOM is relatively low; LOM, DOM, LFOM, HFOM, HA, FA and HM have remarkable positive correlation between them, respectively. There is remarkable positive correlation with the contents of TP, CEC and silt of the studied samples, respectively, but have remarkable negative correlation with the contents of their sand,SiO2. The contents of three combined status are increasing with the polluted level, but the city lake sediments < natural lake sediments of the loosly and firmly ratio.(2) The content of OM and its different components had important effects on P adsorption and release, so the effect mechanism of OM on P adsorption and release was investigated.The result showed: LF of the different trophic sediments from the Yuehu Lake, Wuli Lake and Gonghu Lake were removed by physical density (NaI) separation;The removal of LF shows a little effect on the P release kinetics from lake sediments;The data of P release rates fitted to the parabolic diffusion equation; The removal of LF increases the amount of the P released and its release rate, The removing of LF from the sediments accelerated the P release mainly relate to the two reasons. One is to replace phosphate ion existing in a form of Fe/Al-bounded phosphorus in the sediment with OH- through enhance pH, and the other is to destroyed colloid of LF with sediment of H-bounds on carbonyl. So the processes of P release from lake sediment relates to its amido, carboxyl, and hydroxide of organic matter;The removal of LF shows a little effect on the P sorption kinetics from lake sediments;Reduced the efficiency of phosphate sorption on the lake sediment, improved the content of EPC0, accelerated the release of phosphate. ,and the data of P release rates fitted to the Freundlich equation; The phosphate release kinetic did not change within the sediment samples of different OM contents, but the amount of phosphate release varied. With OM decreasing in the sediments, SRP and DTP release capacity become increasing, DOP release capacity become decreasing,. At the same time, phosphate adsorption kinetic and thermodynamics trends both did no change with the pretreatment, the phosphate adsorption thermodynamics trends fitted to the Freundlich and Langmuir equation, the adsorption capacities were decreasing with the content of OM decreasing.(3) Inducted hydrophytes to the traditional double-phase structure model, the effect of glucose on phosphorus distribution character was researched in the three-phase structure model, especially the effect of physiological and its organizations on phosphorus and nitrogen adsorption. The result showed:Addition of glucose, the release capacity of phosphorus from sediments were improved, and increase the contents of TP, DTP, SRP and SRP in overlying water; With the training, the accumulation content of total N and P in the leaves gradually reduced, and in the roots and stems the distribution of gradually increased.This study conditions, glucose restrain the growth of submerged plants at the beginning of experiment, but promot the the growth in the latter time.(4) The physiological effects of different macrophyte litter content on the decomposition were inverstigated in a laboratory experiment.The addition of macrophyte litter to the sediment resulted in a higher nutrient content(especially enhance the content of NaOH-P and organic phosphorus), aggravated the pullution of sediment, and the absorption and accumulation content of Myriophyllum spicatum L was affected; The changeof water quality in the process of macrophyte litter decomposing, especially the decreases of Do and pH to the normal growth of Myriophyllum spicatum L. The results indicated that the moderate concentration of macrophyte litter couls accelerate the normal growth of Myriophyllum spicatum L, but the rasied concentrations of litter could be a stress to plants and influenced the normal growth of Myriophyllum spicatum L.