Study On Pollution Character And Release Regularity Of The Nutrient From Urban River Sediment

In certain condition, internal N and P can be released into water,which can sharpen eutrophication. Therefore internal N and P would play a key role in the river restoration after external N and P load reduction. Taking Qinhuai River sediment as the object, the paper studied the forms of internal N and P,the rule of release and the control measures in simulated laboratory conditions,which supported by State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University. Uses the modelling to study the existence shape of endogene nitrogen and phosphorus, the release rule and the control method, providing rests for the Qinhuai River ecology repair and the city inland river dredging sciencely.(1) The stratified interstitial water in sediment was monitored. The result indicated that each research target content in the body interstitial water is much higher than that of the rehydrate body, in particular ammonia nitrogen content. It indicated that there has the very strong release tendency for the very great concentration gradient between the water and soil contact surface. There was evident relativity between the total dissolved P and dissolved P in the porewater and between ferrous iron and the dissolved P. The higher degree of correlation indicates that the vary of the total dissolved P in porewater was mainly impacted on dissolved P and the release of P in sediment has intimate correlation with the condition of oxidation -reduction of sediment.(2) Different nitrogen and phosphorus forms in sediments were analyzed. The result indicated that the amount of TN and TP decreased with sediment depth,and the weight ratio between TN and TP is 0.98 to 3.13,so N is the control factor of alga in Qinhuai River. The proportion of inorganic P to TP in sediment is 87%～97%, and active P to TP is 38%～43%. There has good correlation between total nitrogen and organic phosphorus,which shows that they has some concordance of the source.(3) Statistical analysis of different dredging depth to nutrient release was measured .The result shows that it has some control to P release at the dredging beginning, but various cross sections appear scour the depth which the release speed remarkable drop corresponds to have differently. There is little difference of NH₄⁺-N release speed from different dredging depth. In a very long period of time,the control effect of dredging to PO₄^3--P release is obvious and the release speed obviously reduces.(4) Study on the release effects of environmental factors on N and P from urban channel sediments. The result indicated that the release ratio when the overlying water is distilled water is much higher than that of river water. Illumination is disadvantageous to the endogene N and the P release. Disturburance is advantageous to the endogene N and P release at the beginning,but the release intensity is smaller even has some declining when they reach maximal release. The release of N and P will be accelerated with higher temperature, and along with release carrying on, various cross sections NH₄⁺-N and TN release speed elevate along with the temperature obviously drops. Under the weak acid and weak basicity condition ,the bottom putty releases P quantity to be higher than the neutral condition, NH₄⁺-N release speed is upper under acid condition,and along with pH increase of the overling water, NH₄⁺-N release speed drops in the sediments. N and P release quantity obviously in anaerobic condition is higher than that of oxygen condition.