Context: Ferralsols, which cover approximately 6% of the Earth’s continental surface, have unique phosphorus (P) retention properties.

Aims: The research investigates P adsorption properties under non-controlled conditions on lateritic soil samples, combining different methodological approaches.

Methods: Ferralsol samples were analysed using (1) adsorption kinetics and capacities (wet chemical experiment methods), (2) scanning electron microscopy (SEM) and transmission electron microscopy and (3) attenuated transmission reflectance-Fourier transform infrared spectroscopy (ATR-FTIR).

Key results: Wet chemical experiments accord with previous studies on lateritic soils where chemisorption mechanisms govern P adsorption. Further, P adsorption appears to affect soil particles’ structural stability and release of iron (Fe) species in solution. SEM mapping confirmed the location of P compounds in Fe-rich areas. ATR-FTIR identified two inner-sphere complexes: monodentate (FeO)PO₂(OH) and bidentate (FeO)₂PO(OH) at wavenumber positions 958 ± 5, 1042 ± 5 and 1095 ± 8 cm⁻¹; and 930 ± 5, 983 ± 10, 1005 ± 5 and 1122 ± 9 cm⁻¹, respectively. Also, a band centred at 1030 ± 4 cm⁻¹ suggested evidence of ternary complexes for P concentrations above 500 mg P/L. Combined methods suggested the potential involvement of redox mechanisms and other ionic species in the formation and types of phosphate surface complexes.

Conclusions: Our approach builds on previous work in this field by showing evidence of complex ionic interactions governing P retention on lateritic soils. Novel insights are evidence of fluctuations in physical and chemical factors with phosphate adsorption and suggestion of inner-sphere and ternary surface complexation mechanisms.

Implications: Given the wide global distribution of lateritic Ferralsols, our findings have important implications for key emerging challenges relating to P cycling for crop production and environmental impact.

背景：覆盖地球大陆表面约 6% 的 Ferralsols 具有独特的磷 (P) 保留特性。

目的：本研究结合不同的方法学方法，研究了红土土壤样品在非受控条件下的磷吸附特性。

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主要结果：湿化学实验与之前对红土土壤的研究一致，其中化学吸附机制控制 P 吸附。此外，P 吸附似乎会影响土壤颗粒的结构稳定性和溶液中铁 (Fe) 物质的释放。SEM 绘图证实了 P 化合物在富铁区域的位置。ATR-FTIR在波数位置 958 ± 5、1042 ± 5 和 1095 ± 8 cm ^-1处确定了两个内球复合物：单齿 (FeO)PO ₂ (OH) 和双齿 (FeO) ₂ PO(OH) ；和 930 ± 5、983 ± 10、1005 ± 5 和 1122 ± 9 cm ^-1。此外，以 1030 ± 4 cm ^{−1为中心的条带}表明 P 浓度高于 500 mg P/L 时存在三元络合物的证据。组合方法表明氧化还原机制和其他离子物质可能参与磷酸盐表面复合物的形成和类型。

结论：我们的方法建立在该领域先前工作的基础上，展示了控制红土土壤上磷保留的复杂离子相互作用的证据。新的见解证明了物理和化学因素随磷酸盐吸附而波动，并暗示了内球和三元表面络合机制。

影响：鉴于红土 Ferralsols 在全球范围内的广泛分布，我们的研究结果对于与 P 循环对作物生产和环境影响相关的主要新兴挑战具有重要意义。