Purpose Phosphorus (P) fixation in the sediments of eutrophic water bodies using passivation agents to control endogenous pollution is an effective strategy for alleviating symptoms of problematic eutrophication like algal blooms. This work aimed to assess the feasibility of employing lanthanum oxycarbonate (LOC) as a solid-phase P deactivation material to curb sediment-P release. Methods Batch experiments were performed to explore the uptake behavior of phosphate by LOC. X-ray photoelectron spectroscopy was adopted to study the mechanism of phosphate binding with LOC. P sequential extraction procedures and a high-resolution peeper technique were applied to investigate the immobilization performance and mechanism of LOC under two application models (mixing and capping) on sediment internal P. High-throughput sequencing was applied to analyze the impact of LOC addition on the bacterial community in sediments. Results Lanthanum oxycarbonate exhibited outstanding performance in phosphate elimination, providing a maximum adsorption capacity of 63.2 mg g−1 at pH 7, outperforming most La-based materials. The adsorbed phosphate by LOC was mainly in the inert P form, occupying 95% of the extractable P. Surface precipitation, electrostatic attraction, ligand exchange, and complexation were determined to be the mechanisms for phosphate sorption by LOC, with the latter two dominating. Both LOC mixing and capping treatments enhanced sedimentary P sequestration, reducing dissolved reactive P (DRP) concentrations in the overlying water by 56.7–99.6% and 74.1–99.8%, and dissolved total P (DTP) by 52.8–95.2% and 81.1–99.8%, respectively. LOC mixing constrained sediment-P mobility by stabilizing mobile P (MOB-P) within the sediment and fixing DRP in the pore water, whereas LOC covering improved water quality through passivating MOB-P and immobilizing pore water DRP within the upper sediment. The maximum La leaching from LOC into the water column was 9.03 μg L−1, below the environmental threshold of 10.1 μg L−1. Compared to the control, LOC mixing and covering enhanced the abundance of genera related to sulfur transformation (Desulfatiglans and Thermodesulfovibrio) and iron dissolution (Pseudomonas), both of which showed negative correlations with P stability. Conclusion Considering security, cost-effectiveness, control efficiency, and implementation convenience, LOC capping represents a hopeful approach for managing sediment P loads in freshwater ecosystems.

Controlling endogenous phosphorus-loading release from sediments using lanthanum oxycarbonate in two application modes

期刊论文
发表日期：

2025年5月31日

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Xiaolong Wu,
Ruzhong Li,
Jianwei Lin

摘要

Purpose

Phosphorus (P) fixation in the sediments of eutrophic water bodies using passivation agents to control endogenous pollution is an effective strategy for alleviating symptoms of problematic eutrophication like algal blooms. This work aimed to assess the feasibility of employing lanthanum oxycarbonate (LOC) as a solid-phase P deactivation material to curb sediment-P release.

Methods

Batch experiments were performed to explore the uptake behavior of phosphate by LOC. X-ray photoelectron spectroscopy was adopted to study the mechanism of phosphate binding with LOC. P sequential extraction procedures and a high-resolution peeper technique were applied to investigate the immobilization performance and mechanism of LOC under two application models (mixing and capping) on sediment internal P. High-throughput sequencing was applied to analyze the impact of LOC addition on the bacterial community in sediments.

Results

Lanthanum oxycarbonate exhibited outstanding performance in phosphate elimination, providing a maximum adsorption capacity of 63.2 mg g⁻¹ at pH 7, outperforming most La-based materials. The adsorbed phosphate by LOC was mainly in the inert P form, occupying 95% of the extractable P. Surface precipitation, electrostatic attraction, ligand exchange, and complexation were determined to be the mechanisms for phosphate sorption by LOC, with the latter two dominating. Both LOC mixing and capping treatments enhanced sedimentary P sequestration, reducing dissolved reactive P (DRP) concentrations in the overlying water by 56.7–99.6% and 74.1–99.8%, and dissolved total P (DTP) by 52.8–95.2% and 81.1–99.8%, respectively. LOC mixing constrained sediment-P mobility by stabilizing mobile P (MOB-P) within the sediment and fixing DRP in the pore water, whereas LOC covering improved water quality through passivating MOB-P and immobilizing pore water DRP within the upper sediment. The maximum La leaching from LOC into the water column was 9.03 μg L⁻¹, below the environmental threshold of 10.1 μg L⁻¹. Compared to the control, LOC mixing and covering enhanced the abundance of genera related to sulfur transformation (Desulfatiglans and Thermodesulfovibrio) and iron dissolution (Pseudomonas), both of which showed negative correlations with P stability.

Conclusion

Considering security, cost-effectiveness, control efficiency, and implementation convenience, LOC capping represents a hopeful approach for managing sediment P loads in freshwater ecosystems.