氢氧化镁对水体内源磷释放的控制作用

Efficiency of Magnesium Hydroxide Capping and Amendment to Control Phosphorus Release from Sediments

本研究首先通过批量实验考察了氢氧化镁对水中磷酸盐的吸附性能,再通过底泥模拟释放实验考察了氢氧化镁覆盖和添加控制底泥中磷向上覆水体释放的效果及机制.结果表明,氢氧化镁对水中磷酸盐具有良好的吸附能力,其投加量的增加有利于水中磷酸盐被其所吸附去除,与Langmuir模型相比,其对水中磷酸盐的等温吸附行为更适合采用Freundlich和Dubinin-Radushkevitch(D-R)模型加以描述.氢氧化镁覆盖可以有效地控制底泥中磷向上覆水体的释放,使得上覆水中SRP浓度处于较低的水平,即使覆盖层的结构完整性受到扰动破坏而导致覆盖材料与表层底泥的混合,氢氧化镁仍然可以有效地控制底泥中磷向上覆水体的释放.氢氧化镁覆盖和添加均可以有效地降低最上层(0~10 mm)底泥间隙水中SRP的浓度,这对于其覆盖和添加有效控制底泥中磷向上覆水体的释放是至关重要的.人工合成的氢氧化镁对水中磷酸盐的吸附性能优于商业购买的氢氧化镁,前者控制水体内源磷向上覆水体释放的效果也优于后者.以上结果显示,氢氧化镁是一种有希望用于控制水体底泥内源磷释放的活性覆盖和改良材料.

Eutrophication of freshwater bodies has become a global environmental problem,and phosphorus(P)has been identified as one of the key limiting factors responsible for this eutrophication problem.Reducing internal P release is crucial to the control of the eutrophication of freshwater bodies besides reducing the input of external P.To control sedimentary P release,magnesium hydroxide[Mg(OH)2]was applied as a capping and amendment material in this study.The adsorption performance of phosphate on Mg(OH)2 was investigated in batch mode,and the effect of Mg(OH)2 capping and amendment on the mobilization of P in sediments was studied using sediment incubation experiments.Results showed that Mg(OH)2 exhibited good adsorption performance toward phosphate.The phosphate removal efficiency of Mg(OH)2 increased with increasing adsorbent dosage.The adsorption equilibrium data of phosphate on Mg(OH)2 could be better described by the Freundlich and Dubinin-Radushkevich isotherm models compared to the Langmuir isotherm model.Mg(OH)2 capping and addition both could effectively control the release of reactive soluble P(SRP)from sediments into the overlying water,resulting in a low concentration of SRP in the overlying water under Mg(OH)2 capping and amendment conditions.Mg(OH)2 capping and amendment both could reduce pore water SRP in the uppermost sediment(0-10 mm),which played a key role in the control of the release of SRP from sediments into the overlying water.The as-prepared Mg(OH)2 possessed a much higher phosphate adsorption ability than commercial Mg(OH)2,and the former also had a higher controlling efficiency of sedimentary P release than the latter.In summary,Mg(OH)2 is a promising capping and amendment material for the control of internal phosphorus release in freshwater bodies.