Contamination And Adsorption-Desorption Characteristic Simulation For Nitrogen And Phosphorus In Sediments From Different Hydraulic Property Zones In Steam

On the study of the typical stream of Hefei Shiwuli river, this paper, based onanalysis of nitrogen and phosphorus content of the sediments and interstitial watercontaining different hydraulic properties respectively, simulates and fits the verticaldistribution of sediments and interstitial water and explores the nitrogen andphosphorus adsorption/desorption characteristics of superficial sediments, as wellas nitrogen and phosphorus nutrient salt concentrations of interstitial water section.then simulates the nitrogen and phosphorus moving and transforming laws betweenoverlying water and sediments while plants growing in laboratory.The main content and the results are as follows:（1） By means of the analysis and test which aimed at the physicochemicalproperty of sediments and interstitial water in different hydraulic properties areas,we tried to analyze that the different hydraulic properties affect the nitrogen andphosphorus nutrient of sediments and interstitial water. The results shows that thereare obvious differences at nutrient content in different hydraulic properties areas.Specifically, the TN、TP content of sediment in straight river area is evidently lowerthan other hydraulic properties areas, meanwhile, the sediment concentration ofNH₄⁺-N、 NO₃^--N and PO₄^3--P in curve scour area and bank collapse area isrelatively low, and the change of vertical section is relatively weak. While ingrowth area of aquatic plants, each index is conspicuous in the change of verticalsection but unconspicuous in regularity. The nitrogen and phosphorus concentrationin the different hydraulic properties sediments has a certain degree of correlativitywith the nitrogen and phosphorus concentration of interstitial water, and theNH₄⁺-N、NO₃^--N source-sink relationship mainly shows a high consistency, but thePO₄^3--P is short of regularity. Except the plant growth area, the NH₄⁺-N、NO₃^--Nand PO₄^3--P concentration of other hydraulic properties interstitial water cansimulate by the exponential function y=exp（a+bx+cx2）on the vertical section.（2） The experiment for sediment to nitrogen and phosphorus dynamicadsorption shows that: adsorption can be divided into fast adsorption and slowadsorption. The fast adsorption of ammonia nitrogen maintains in first10min and itwill reach equilibrium in next2hours. While the phosphate adsorption is much slower, in that the fast adsorption concentrates in first5hours, and reachesequilibrium in72hours, furthermore, the change of adsorption quantity with timeaccords with Lagergren equation. The experiment for sediment to nitrogen andphosphorus dynamic adsorption also shows that: The sediments with differenthydraulic properties to the ammonia nitrogen dynamic adsorption accords withlinear regression equation, which can all reach0.93of the fitting correlationcoefficient; similarly, the sediments to phosphate adsorption also accords withlinear regression equation in the condition of low concentration, while in thecondition of high concentration, the adsorption can fit with chiasmatypy Langmuirequation evidently, which can reach0.9of correlation coefficient.（3） The plants in the growth process can dramatically affect of the physicalparameters of overlying water-sediment system, as well as the nitrogen andphosphorus transformation. In this process, the overlying water and sediment ORPchanges from reducibility to oxidability, and the conductivity keeps reducing too,moreover, the pH of sediments changes from weak alkaline to weak acidic in thegrowth process, obviously from the cattail experimental group. The nutrient sourcefor plant growth mainly supplied by organic nitrogen and organic phosphorus in thesediments, and the nitrogen source of overlying water is mainly ammonia nitrogen.Organic matter has a obvious positive correlation with the plant growth rate.