Lu Hansha, Yang Yang, Huang Kaiyi, Huang Guoyong, Hu Shiwen, Pan Dandan, Liu Tongxu, Li Xiaomin
SCNU Environmental Research Institute, Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety & MOE Key Laboratory of Theoretical Chemistry of Environment, South China Normal University, Guangzhou, 510006, China; National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou, 510650, China; School of Environment, South China Normal University, Guangzhou, 510006, China.
National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou, 510650, China.
Environ Pollut. 2023 Oct 15;335:122271. doi: 10.1016/j.envpol.2023.122271. Epub 2023 Jul 26.
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 NHF 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.
铅（Pb）可在诸如地表径流和强降雨等洪水事件期间进入土壤环境。然而，在外源铅在缺氧-好氧交替变化过程中的关键转化过程仍知之甚少，尤其是磷和有机物如何促进铅的固定/释放。在此，基于七步连续萃取、溶解有机碳、硫酸盐、铁、磷和表面位点的结果，建立了一个动力学模型，以研究在交替缺氧-好氧条件下两种铅污染水平的酸性土壤中铅的转化。结果表明，在缺氧条件下培养40天后，潜在可利用的铅，包括溶解态、可交换态和特异性吸附态部分，逐渐转移到富里酸络合态、铁锰氧化物结合态和硫化物结合态铅中，而在好氧条件下培养20天后，富里酸络合态铅进一步增加。在缺氧条件下，用0.5 M HCl或0.03 M NH₄F在0.025 M HCl中萃取的磷浓度增加，而在好氧条件下降低。在动力学建模中考虑铅与磷的结合时，铅转化的模拟结果表明，在缺氧条件下，磷对铅的固定比有机物更重要，而在好氧条件下土壤中溶解有机物再固定过程中，磷酸盐、铁锰氧化物和硫化物固定的铅会缓慢释放，然后与富里酸络合。用低铅水平建立的模型已成功应用于描述高铅水平下的铅转化。本研究通过动力学建模全面了解了磷和有机物在控制土壤中铅转化中的作用。
