Effects Of Environmental Factors And Lanthanum-Modified Bentonite On Phosphorus In Changdang Lake Sediment Study On Release Mechanism

At present,the problem of phosphorus pollution in lake water is relatively serious.Under the background of effective control of exogenous phosphorus pollution in lakes,the release of endogenous phosphorus in sediments has become the biggest risk source of phosphorus pollution in lakes.It is of great practical significance to explore the release law of endogenous phosphorus and determine the effective strategy of endogenous phosphorus inhibition.In this study,the Changdang Lake sediment was taken as the object,and the effects of environmental factors on phosphorus release from sediment and phosphorus inhibition by lanthanum-modified bentonite were investigated by laboratory simulation experiments.The change of phosphorus form and content was studied,and the inhibitory effect and mechanism of lanthanum modified bentonite on sediment phosphorus were studied.The main conclusions of the study are as follows:(1)The temperature is proportional to the release intensity of phosphorus in the sediment.The higher the temperature,the greater the intensity of phosphorus release in the sediment,and the increase in the phosphorus concentration in the overlying water;increase,indicating that a strong acid-base environment is conducive to the release of phosphorus from the sediment;dissolved oxygen is inversely proportional to the release intensity of phosphorus from the sediment,and the low-oxygen environment is more conducive to the release of phosphorus.Finally,the phosphorus flux was calculated,and the optimal curve fitting was performed on the relationship between environmental factors and phosphorus flux.The fate change of sediment phosphorus release was clarified,which was more conducive to the conditional control of sediment phosphorus release.(2)The temperature change had no effect on the phosphorus inhibition effect of lanthanummodified bentonite;compared with p H 6.0～8.0,the phosphorus concentration of the overlying water with p H=9.0 and p H=5.0 showed a higher level,indicating a stronger acid-base environment It will weaken the phosphorus inhibition effect of lanthanum modified bentonite;under different dissolved oxygen conditions,the concentration of phosphorus in the overlying water is low,indicating that lanthanum modified bentonite is not sensitive to redox potential(ORP).Therefore,it is determined that the lanthanum-modified bentonite has a better inhibitory effect in a neutral environment.(3)After adding lanthanum modified bentonite for 60 days,the contents of total phosphorus(TP),granular phosphorus(PP),dissolved total phosphorus(DTP)and soluble active phosphorus(SRP)in overlying water decreased by 52 ～ 56%,30 ～ 48%,48 ～ 64% and 55 ～ 68% respectively.Lanthanum modified bentonite precipitated with SRP during sedimentation,reducing the phosphorus content.The form and content of phosphorus in sediments also changed greatly.The average content of TP in the surface increased by 8%,the average content of inorganic phosphorus(IP)increased by 15%,and the content of organic phosphorus(OP)changed little.Among them,in terms of inorganic phosphorus forms,the content of exchangeable phosphorus(EX-P)decreased by 48%,the content of iron aluminum bound phosphorus(Fe / Al-P)decreased by 59% and the content of calcium bound phosphorus(Ca-P)increased by 100%,indicating that lanthanum modified bentonite transformed active phosphorus into stable phosphorus and restrained the release of phosphorus from sediment.This study takes Changdang Lake as the object,and the relevant results provide some reference and reference for the control of endogenous phosphorus pollution in Changdang Lake and other shallow water and overflow lakes.