原位覆盖控制沉积物磷释放效果的验证评估

Validation and Evaluation of In-situ Capping for Controlling Phosphorus Release in Sediment

文章通过覆盖材料(方解石、湖沙或方解石+湖沙)对底泥磷释放的阻控实验以及利用梯度扩散薄膜(DGT)的底泥原位测试,验证评估覆盖剂对呼伦湖沉积物磷的生态修复效果。结果发现:(1)方解石、方解石+湖沙或湖沙能有效降低表层沉积物的DGT-P浓度(CDGT(PO_(4)^(3-)-P)),沉积物/水界面扩散通量和上覆水溶解反应性磷;方解石、方解石+湖沙覆盖的表层沉积物的CDGT(PO_(4)^(3-)-P)峰值或平均值明显低于对照样;方解石、方解石+湖沙的上覆水DRP的去除率分别超过78%和81%;方解石+湖沙可以将沉积物/水界面无机磷扩散通量降低至负值;(2)方解石和方解石+湖沙能明显地降低表层沉积物总磷(TP)、活性磷(NH_(4)Cl-P和BD-P)含量及其占TP的百分比,沉积物反应性磷再补给系数r减少而惰性成份(NaOH_(85)-P和Ca-P)及其占TP的百分比增加;(3)方解石+湖沙覆盖的表层沉积物TP变化范围:-45~-30 mg/kg;磷提取相(NH_(4)Cl-P、BD-P、Ca-P和NaOH_(85)-P)含量变化值,磷提取相变化量占对照沉积物对应提取成份的百分比分别为-17~-10 mg/kg (-38.46%~-29.31%);-23~-16 mg/kg (-46.15%~-32.86%);10~15 mg/kg (2.41%~3.63%)和8~14 mg/kg(3.20%~3.99%);r降低范围:0.02~0.19。综上,方解石的吸附或阻隔作用能降低沉积物总磷和活性磷,降低沉积物磷再补给能力;NH_(4)Cl-P和BD-P被转化为情性成份(NaOH_(85)-P和Ca-P),磷迁移性降低。覆盖剂对沉积物磷内源负荷控制效果为方解石+湖沙>方解石>湖沙。方解石+湖沙的磷阻控机制是方解石对磷的吸附,磷和方解石的共沉淀以及湖沙的物理阻隔;方解石+湖沙的多层覆盖是一种应用价值较高的沉积物原位修复技术。

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(PO_(4)^(3-)-P)in top sediments,diffusive fluxes at sediment/water interface and dissolved reactive P in overlying water;CDGT(PO_(4)^(3-)-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(NH_(4)Cl-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(NaOH_(85)-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 NH_(4)Cl-P,BD-P,Ca-P or NaOH_(85)-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.NH_(4)Cl-P and BD-P turned into inert fractions(NaOH_(85)-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.