锆改性沸石添加对重污染河道底泥磷释放和钝化的影响

通过模拟实验并结合磷形态分级提取和生物有效磷提取,考察了锆改性沸石添加对重污染河道底泥磷释放和钝化的影响.结果发现,锆改性沸石添加不仅会降低间隙水中磷的浓度,而且也会降低底泥-水界面磷扩散通量,从而降低了底泥中磷向覆水体的释放风险.锆改性沸石添加会促使底泥中弱吸附态磷(NH_4Cl-P)、氧化还原敏感态磷(BD-P)和盐酸提取态磷(HCl-P)向金属氧化物结合态磷(NaOH-r P)和残渣态磷(Res-P)转变,而底泥中NH_4Cl-P和BD-P这2种容易释放态磷的降低有助于减少底泥中磷释放的风险.此外,锆改性沸石添加降低了底泥中了WSP(水溶性磷)、RDP(易解吸磷)、FeO-P(铁氧化物-滤纸提取磷)和Resin-P(阴离子交换树脂提取磷)这4种生物有效磷含量.锆改性沸石添加控制底泥磷释放的机制为:锆改性沸石添加,一方面可以钝化底泥中潜在可移动态磷和生物有效磷,达到减少底泥中磷向间隙水中释放的目的,另一方面可以通过锆改性沸石的吸附作用直接去除间隙水中的磷;而间隙水中磷浓度的降低,会降低间隙水和上覆水之间磷的浓度梯度,进而降低了底泥-水界面磷扩散通量.以上的结果显示,锆改性沸石是一种有希望的可以钝化河道底泥中磷并控制其向上覆水体释放的改良剂.

Effect of Zirconium-modified Zeolite Addition on Phosphorus Release and Immobilization in Heavily Polluted River Sediment

The effect of zirconium-modified zeolite (ZrMZ) addition on the release and immobilization of phosphorus in heavily polluted river sediment was investigated using microcosm incubation experiments. Results showed that addition of ZrMZ to sediment greatly reduced concentrations of P in pore water and overlying water, also reducing the release flux of P across the interface between overlying water and sediment. The addition of ZrMZ to sediment resulted in the transformation of NH₄Cl extractable P (NH₄Cl-P), Na₂S₂O₄/NaHCO₃ extractable P (BD-P), and HCl extractable P (HCl-P) into NaOH extractable P (NaOH-rP) and residual P (Res-P) in sediment, thereby leading to the reduction of mobile P (sum of NH₄Cl-P and BD-P) in sediment. Content of bioavailable P (BAP) including water soluble P (WSP), readily desorbable P (RDP), iron oxide paper strip extractable P (FeO-P), and anion resin extractable P (Resin-P) in sediment also declined following addition of ZrMZ. Control of P release from sediment by ZrMZ could be due to reduction of P in pore water and immobilization of P in sediment. Results of this work indicate that ZrMZ is very promising for controlling P release from sediments in heavily polluted rivers.