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

Abstract

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/m²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0.036~0.096 μg/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/m² 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 0.036-0.096 μg/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.