State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, PR China; Guizhou Province Field Scientific Observation and Research Station of Hongfeng Lake Reservoir Ecosystem, Guiyang, 551499, PR China.
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, PR China; University of Chinese Academy of Sciences, Beijing, 100049, PR China; Guizhou Province Field Scientific Observation and Research Station of Hongfeng Lake Reservoir Ecosystem, Guiyang, 551499, PR China.
Water Res. 2024 Sep 15;262:122123. doi: 10.1016/j.watres.2024.122123. Epub 2024 Jul 22.
Identifying the sources and cycling of phosphorus (P) is particularly important for formulating effective P management strategies in inland water. The oxygen isotopic compositions of phosphate (δO) are recognized as a promising tool to solve this problem. However, the application of δO in freshwater sediment is currently constrained by multiple difficulties. In this study, we presented a novel pretreatment method for δO analysis of sediment inorganic P pools. Our results showed that the new method has advantages of simple operation, less time-consuming, and high P recovery rates. Specifically, we replaced the traditional Mg-induced co-precipitation (MAGIC) method by introducing Zr-Oxides gels with high selective adsorption function for phosphate. This made subsequent processing simpler and reduced the time consumption to ∼10 days, and the range of P recovery rates were from 88 % to 104 %. Furthermore, we emphasized the necessity of vacuum roasting following lyophilized AgPO to eliminate residual oxygen-containing impurities (e.g., NO, AgO, and organic matter). Additionally, evidences from microscopy and spectroscopy confirmed that this method ultimately yielded high-purity AgPO with the Ag:P molar ratios of 3.35:1. Importantly, combining direct synthesis AgPO between KHPO and AgNO with the AgPO obtained by the method revealed no stark oxygen isotopic fractionation of phosphate during the pretreatment processes. The newly established δO pretreatment methods here can also be extended to broader studies of the biogeochemical cycling of P in aquatic ecosystems, potentially advancing the understanding of the global P cycle.
确定磷（P）的来源和循环对于制定内陆水域有效 P 管理策略尤为重要。磷酸盐的氧同位素组成（δO）被认为是解决这一问题的有前途的工具。然而，δO 在淡水沉积物中的应用目前受到多种困难的限制。在这项研究中，我们提出了一种新的沉积物无机磷库δO 分析预处理方法。我们的结果表明，该新方法具有操作简单、耗时少、磷回收率高的优点。具体来说，我们用对磷酸盐具有高选择性吸附功能的 Zr-Oxides 凝胶取代了传统的 Mg 诱导共沉淀（MAGIC）法。这使得后续处理更简单，时间消耗减少到约 10 天，磷回收率范围为 88%至 104%。此外，我们强调了在冻干 AgPO 后进行真空煅烧以消除残留含氧杂质（如 NO、AgO 和有机物）的必要性。此外，显微镜和光谱学的证据证实，该方法最终得到了高纯 AgPO，Ag:P 摩尔比为 3.35:1。重要的是，通过 KHPO 和 AgNO 之间的直接合成 AgPO 与通过该方法获得的 AgPO 相结合，表明在预处理过程中磷酸盐没有明显的氧同位素分馏。这里建立的新的δO 预处理方法也可以扩展到水生生态系统中 P 的生物地球化学循环的更广泛研究，可能有助于深入了解全球 P 循环。
