土壤磷酸盐氧同位素在生物地球化学研究领域中具有重要的应用，土壤成分复杂，氧同位素来源多样，可靠的样品富集和纯化技术是磷酸盐氧同位素研究的前提保障。本研究以土壤无机磷酸盐氧同位素为研究对象，采用多步沉淀法对土壤中无机磷酸盐进行提取，并转化成Ag3 PO4沉淀分离，用于磷酸盐氧同位素测试。以氨水重结晶方法对Ag3 PO4进行纯化，通过XRD和元素分析验证了产品纯度。结果表明，通过H2 O2漂洗去除有机质后，辅助氨水重结晶可有效去除Ag3 PO4中夹杂的Ag2 O和Ag单质等无机杂质，未产生同位素分馏，采用标准KH2 PO4对方法全流程安全性进行验证。对3种不同利用类型的土壤中磷酸盐进行分析，结果表明，方法的平行性良好，不同类型土壤磷酸盐氧同位素差异显著，δ18 Op 值在15.2‰~19.5‰之间，可用于土壤磷溯源研究。%Analytical technique on oxygen isotope composition of phosphate in soil has important applications in biogeochemical research. As the composition of the soil is complex with multiple oxygen sources, a liable phosphate enrichment and purification technology is important for phosphate oxygen isotope research. Here we presented a protocol on the analysis of the δ18 Op of inorganic phosphate in soil, and phosphate was purified with multiple mineral precipitations and finally precipitated as silver phosphate. The efficiency of NH4 OH purification method was examined and the purity of the product was verified through XRD and element analysis. The result showed that treatment of the Ag3 PO4 sample by recrystallizing with ammonia could remove the impurity efficiently without significantly modifying oxygen isotope compositions. The validity of sample processing and reliability of isotope analyses were confirmed by processing a KH2 PO4 standard in parallel with soil P sample. The analytical result of three soil types indicated that this method provided good precision of 0. 2‰. The differences of δ18 Op between three soils groups are significant ( From 15. 2‰ to 19. 5‰) and can be used to tracing P sources.
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