环境地球化学国家重点实验室知识库

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 (δ¹⁸O_P) are recognized as a promising tool to solve this problem. However, the application of δ¹⁸O_P in freshwater sediment is currently constrained by multiple difficulties. In this study, we presented a novel pretreatment method for δ¹⁸O_P 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 Ag₃PO₄ to eliminate residual oxygen-containing impurities (e.g., NO₃⁻, Ag₂O, and organic matter). Additionally, evidences from microscopy and spectroscopy confirmed that this method ultimately yielded high-purity Ag₃PO₄ with the Ag:P molar ratios of 3.35:1. Importantly, combining direct synthesis Ag₃PO₄ between KH₂PO₄ and AgNO₃ with the Ag₃PO₄ obtained by the method revealed no stark oxygen isotopic fractionation of phosphate during the pretreatment processes. The newly established δ¹⁸O_P 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.