硝酸钙添加和锆改性膨润土覆盖联用控制底泥中磷释放的效果及机制

通过底泥培养实验，研究了硝酸钙添加和锆改性膨润土覆盖联用控制底泥中磷释放的效果及机制.结果发现，在缺氧条件下，底泥中磷会先释放出来进入间隙水中，而后穿越底泥-水界面扩散进入上覆水中，导致上覆水中溶解态活性磷（SRP）和薄膜扩散梯度（DGT）有效态磷浓度较高.但是，联合使用硝酸钙添加和锆改性膨润土覆盖可有效控制底泥中磷释放出来进入上覆水中，导致上覆水中SRP和DGT有效态磷浓度处于很低的水平.此外，该组合技术还可有效降低底泥中间隙水SRP和DGT有效态磷浓度以及最上层底泥中氧化还原敏感态磷（BD-P）含量，这对于其控制水体内源磷释放会起到至关重要的作用.与单一的硝酸钙添加技术相比，组合技术对上覆水中SRP的去除效果较优，对底泥间隙水中SRP及底泥-水界面SRP扩散速率的削减效果较佳，对最上层底泥中BD-P的削减率也较高.与单一的锆改性膨润土覆盖相比，组合技术在底泥修复后期对上覆水中SRP的削减效果较佳.另外，组合技术对底泥中间隙水SRP和DGT有效态磷的削减率要高于单一的锆改性膨润土覆盖技术，前者对底泥-水界面SRP扩散速率以及表观磷扩散速率的削减效果也好于后者.硝酸钙添加/锆改性膨润土覆盖组合是一种很有希望的水体内源磷释放控制技术.

Combined Use of Zirconium-Modified Bentonite Capping and Calcium Nitrate Addition to Control the Release of Phosphorus from Sediments

In this study, sediment incubation experiments were carried out to investigate the efficiency and mechanism of the control of phosphorus (P) release from sediments. The results showed that under anoxic conditions, P could be released from the sediment into the pore water first and then the dissolved P in the pore water could be transported into the overlying water, leading to high concentrations of soluble reactive P (SRP) and diffusive gradient in thin-films (DGT)-labile P in the overlying water. However, the combined use of calcium nitrate (CN) addition and zirconium-modified bentonite (ZB) capping could effectively control the release of P from sediment, resulting in the low concentrations of SRP and DGT-labile P in the overlying water. Furthermore, the combined use of CN addition and ZB capping could significantly decrease the concentrations of SRP and DGT-labile P in the sediment. In addition, the combined utilization of CN addition and ZB capping also could result in a reduction of redox sensitive P (BD-P) in the uppermost sediment layer. The reduction of pore water SRP, DGT-labile P, and BD-P in sediment solids is of great importance to the control of sediment-P liberation by the combined use of CN addition and ZB capping. The reduction efficiency of overlying water SRP by combined CN addition/ZB capping technology was higher than that of single CN addition technology. Compared to that of single CN addition technology, the reduction efficiencies of pore water SRP, SRP diffusion flux across the sediment/overlying water interface (SWI), and BD-P in the sediment by the combined use of CN addition and ZB capping were also higher. The combined technology based on CN addition and ZB capping had a higher reduction efficiency of overlying water SRP during the late stage of sediment remediation than the single technology based on ZB capping, and the former had higher reduction efficiencies of pore water SRP, DGT-labile P, and SRP diffusion flux across the SWI and apparent P diffusion flux through the SWI than the latter. The results of this work indicate that the combined use of CN addition and ZB capping is a very promising method for the control of P release from sediments.