铅(Pb)在地表径流和强降雨等洪水事件中可以进入土壤环境。然而,缺氧-氧变化过程中外源铅的关键转化过程仍然知之甚少,特别是磷和有机物如何促进铅的固定/释放。这里,建立了一个动力学模型,以研究在缺氧-氧交替条件下,具有两种水平Pb污染的酸性土壤中Pb的转化。根据七步顺序提取的结果,溶解的有机碳,硫酸盐,铁,磷,和表面网站。结果表明,潜在可用的Pb,包括溶解的,可交换,特别是吸附的馏分,逐渐转移到富里克情结,Fe-Mn氧化物结合,和硫化物结合铅在缺氧条件下培养40天后,而富里络合物Pb在有氧条件下孵育20天后进一步增加。在缺氧条件下,用0.5MHCl或0.03MNH4F在0.025MHCl中提取的磷浓度增加,而在有氧条件下降低。当在动力学建模过程中考虑Pb与磷的结合时,Pb转化的模拟结果表明,在缺氧条件下,磷对Pb的固定比有机质更重要,而磷酸盐,Fe-Mn氧化物,在有氧条件下,在土壤中溶解的有机物重新固定过程中,固定的硫化物Pb缓慢释放,然后与富里酸络合。建立的低Pb水平模型已成功用于描述高Pb水平的Pb转化。本研究通过动力学模型全面了解了磷和有机质在控制土壤中铅转化中的作用。
Lead (Pb) can enter soil environment during flooding events such as surface runoff and intensive rainfall. However, the key transformation processes of exogenous Pb during anoxic-oxic alteration remain poorly understood particularly how phosphorus and organic matter contribute to Pb immobilization/release. Here, a kinetic model was established to investigate the Pb transformation in an acidic soil with two levels of Pb contamination under alternating anoxic-oxic conditions, based on the results of seven-step sequential extraction, dissolved organic carbon, sulfate, iron, phosphorus, and surface sites. Results showed that the potentially available Pb, including dissolved, exchangeable, and specifically adsorbed fractions, was gradually transferred to the fulvic complex, Fe-Mn oxides bound, and sulfides bound Pb after 40-day incubation under anoxic conditions, while the fulvic complex Pb further increased after 20-day incubation under oxic conditions. The concentration of phosphorus that was extracted by 0.5 M HCl or 0.03 M NH4F in 0.025 M HCl increased under anoxic conditions and decreased under oxic conditions. When Pb-binding to phosphorus is considered during kinetic modeling, the simulated results of Pb transformation suggest that phosphorus is more important than organic matter for Pb immobilization under anoxic conditions, while the phosphates, Fe-Mn oxides, and sulfides immobilized Pb is slowly released and then complexed by fulvic acids during the re-immobilization of dissolved organic matter in soil under oxic conditions. The model established with low Pb level has been successfully applied to describe the Pb transformation with high Pb level. This study provides a comprehensive understanding of the roles of phosphorus and organic matter in controlling Pb transformation in soil from kinetic modeling.