Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Science and Engineering, Nanjing University, Nanjing, Jiangsu 210023, China; Frontiers Science Center for Critical Earth Material Cycling (FSC-CEMaC), Nanjing University, Nanjing, Jiangsu 210023, China.
Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Science and Engineering, Nanjing University, Nanjing, Jiangsu 210023, China; School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, China; Frontiers Science Center for Critical Earth Material Cycling (FSC-CEMaC), Nanjing University, Nanjing, Jiangsu 210023, China.
Sci Total Environ. 2023 Sep 10;890:164444. doi: 10.1016/j.scitotenv.2023.164444. Epub 2023 May 24.
The interaction of phosphate with typical soil minerals is important for understanding P cycling in natural and agricultural systems. We investigated the mechanisms of kinetics of phosphate uptake onto calcite using solid-state NMR spectroscopy. At a low phosphate concentration of 0.5 mM, the P single-pulse solid-state NMR peak revealed the formation of amorphous calcium phosphate (ACP) within the initial 30 min, which transformed to carbonated hydroxyapatite (CHAP) after 12 d. At a high phosphate concentration (5 mM), the results showed transformation from ACP to OCP, later to brushite, and eventually to CHAP. The formation of brushite is further supported by P{H} heteronuclear correlation (HETCOR) spectra via a correlation of δ = 1.7 ppm and the H peak at δ = 6.4 ppm, which denotes the structure water of brushite. Furthermore, C NMR directly revealed both A-type and B-type CHAP. Generally, this work provides a detailed understanding of the aging effect on the phase transition scale of phosphate surface precipitation onto calcite in soil environments.
磷酸盐与典型土壤矿物质的相互作用对于理解自然和农业系统中的磷循环非常重要。我们使用固态 NMR 光谱研究了磷酸盐在方解石上的吸收动力学机制。在低浓度磷酸盐（0.5mM）条件下，P 单脉冲固态 NMR 谱峰显示在最初的 30 分钟内形成了无定形磷酸钙（ACP），12 天后转化为碳酸羟磷灰石（CHAP）。在高浓度磷酸盐（5mM）条件下，结果表明从 ACP 到 OCP，再到鸟粪石，最终到 CHAP 的转化。通过 δ=1.7ppm 和 δ=6.4ppm 处的 H 峰之间的相关性，P{H}异核相关（HETCOR）谱进一步支持了鸟粪石的形成，这表示了鸟粪石的结构水。此外，C NMR 直接揭示了 A 型和 B 型 CHAP。总的来说，这项工作提供了对方解石表面磷沉淀在土壤环境中向磷灰石表面沉淀的相转变尺度的老化效应的详细理解。
