基于梯度扩散薄膜技术(DGT)的氨基生物炭覆盖沉积物-水界面铜、铅释放研究

Release of copper and lead from the sediment-water interface under in-situ coverage of amino biochar via Diffusive Gradients in Thin-films( DGT)

湖泊沉积物的重金属污染防治一直是环境领域的热点问题.本研究采用氨基生物炭作为覆盖材料,利用梯度扩散薄膜技术(DGT),研究了上覆水不同pH及水流扰动条件下Cu(Ⅱ)、Pb(Ⅱ)在沉积物水界面间的原位释放特征,以及氨基生物炭对湖泊沉积物重金属污染的原位修复效果.研究结果表明,在0 r/min或100 r/min水动力条件下,可移动态重金属离子有不断由沉积物向其他介质扩散的趋势,1.81 kg/m 2的氨基生物炭覆盖强度可降低Cu(Ⅱ)、Pb(Ⅱ)释放通量达89%以上,有效减小了水环境中重金属的潜在生态风险.在pH=5的酸性及pH=9的碱性水环境中原位修复效果较差,水体中大量的H+或络合物均会削弱氨基生物炭对重金属离子的吸附,当上覆水在pH=7的中性条件时原位修复效果最佳.100 r/min水流扰动下的上覆水Cu(Ⅱ)、Pb(Ⅱ)含量在释放平衡时较0 r/min条件下高出0.036~0.096μg/mL,说明高强度的水流扰动易造成覆盖材料的扬起和浮动,导致覆盖材料与重金属发生解吸.

The prevention and control of heavy metal pollution in lake sediments has always been a hot issue in the environmental field.In this study,amino modified biochar was used as the covering material and Diffusive Gradients in Thin-films(DGT)was used to monitor the characteristics of in-situ release of Cu(Ⅱ)and Pb(Ⅱ)at the sediment-water interface with different pH and water flow disturbance conditions.The in-situ remediation effect of amino modified biochar on heavy metal pollution was also analyzed.The results show that the mobile heavy metal ions have a tendency to diffuse from the sediment to other media at 0 r/min or 100 r/min hydrodynamic conditions.The cover strength of 1.86 kg/m 2 for amino modified biochar can reduce the release flux of Cu(Ⅱ)and Pb(Ⅱ)over 89%,which effectively reduces the potential ecological risk of heavy metals in the water environment.A large amount of H+or complex in the water will weaken the adsorption of heavy metal ions by amino biochar.When the overlying water is in neutral condition with pH=7,the in-situ remediation effect is the best.The content of Cu(Ⅱ)and Pb(Ⅱ)in the overlying water under the disturbance of 100 r/min water flow is 0.036-0.096μg/mL higher than that at 0 r/min when the equilibrium is released.The high-intensity water flow disturbance easily caused the lifting and floating of the covering material,resulting in desorption of heavy metals escaping from the covering material.