Validation and Evaluation of In-situ Capping for Controlling Phosphorus Release in Sediment
By way of the experiment regarding the obstruct/control of P release in bottom sediments by use of calcite,lake sand and calcite+lake-sand,and the in-situ sediment test by diffusive gradients in thin films(DGT),the ecological resto-ration of P-containing sediments in Lake Hulun using the covering materials was validated and evaluated.Consequently,the results obtained presented that calcite,lake-sand and calcite+lake-sand could effectively depleted DGT concentrations of P(CDGT(PO43--P)in top sediments,diffusive fluxes at sediment/water interface and dissolved reactive P in overlying water;CDGT(PO43--P)peak value in top sediment covered by calcite and calcite+lake-sand were distinctly lower than that of the con-trol sediment sample,and removal efficiencies of DRP(dissolved reactive phosphorus)in overlying water exceeded 78％and 81％,respectively;the diffusive fluxes of inorganic P in sediment/water interface would be reduced to negative value as calcite+lake-sand was used.Calcite and calcite+lake-sand could remarkably reduced the contents of TP(total P)and reactive P(NH4Cl-P and BD-P),and the percentage of reactive P/TP and the re-supply constant of reactive P in surface sediment(r)were declined,while the(NaOH85-P or Ca-P)was increased,as well as the percentage of inert P fraction in TP;and for the top sediments that were covered by calcite+lake sand,the variation range of TP was between-45 and-30 mg/kg;the variation amounts of NH4C1-P,BD-P,Ca-P or NaOH85-P,and the percentage of the variation of P fraction of covered sediments in the corresponded fraction in the control sediment were in the ranges of-17 to-10 mg/kg(-38.46％to-29.31％),-23 to-16 mg/kg(-46.15％～-32.86％),10 to15 mg/kg(2.41％to 3.63％)or 8～14 mg/kg(3.20％to 3.99％),respectively and the reduction range of r was between 0.02 and 0.19.In summary,the effects of adsorption and obstruction of covering ma-terials could reduce TP and reactive P contents and thus depleted the re-supply ability of sediment P.NH4Cl-P and BD-P turned into inert fractions(NaOH85-P)and Ca-P,and thus sediment P mobility declined.The capping efficiencies of internal P-loading in the sediments with three different covering materials were arranged in order of decreasing magnitude:calcite+lake-sand＞calcite＞lake-sand,As to their mechanism of obstructing P-release from sediments could be described as:calcite+lake-sand hinged on P adsorption,calcite co-precipitated with P,and lake-sand played a role of physical barrier.In addition,using calcite+lake-sand multilayer capping could be an in-situ restoration technique worthy of high application value.
in-situ cappingcalcitediffusive gradients in thin filmssediment/water interfaceinternal loading
万方数据
维普
