Research and Application of Analytical Technique on δ18Op of Inorganic Phosphate in Soil

Analytical technique on oxygen isotope composition of phosphate in soil plays an important role 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 present a protocol on the analysis of the δ18Op of inorganic phosphate in soil, wherein phosphate was purified with multiple mineral precipitations and finally precipitated as Ag3PO4. The efficiency of NH4OH purification method was examined and the purity of the product was verified through XRD and element analysis. The result showed that the treatment of Ag3PO4 sample by recrystallizing with ammonia could remove the impurity efficiently without significantly modify oxygen isotope compositions. The validity of sample processing and the reliability of isotope analyses were confirmed by processing a KH2PO4 stand in parallel with soil samples containing phosphate. The analysis result of three types of soil samples indicated that this method provided good precision of 0.2‰. There were significant differences of δ18Op among three types of soil (from 15.2‰ to 19.5‰), and δ18Op could be used to trace P sources.

A protocol on the research of δ18Op in soil was presented and the efficiency of recrystallization purification method with NH4OH was investigated. The analysis result of three types of soils indicated that this method was quite feasible with satisfactory validity, precision and parallel, and different types of soil had significant difference in δ18Op.Figure optionsDownload as PowerPoint slide