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土壤中碳酸氢钠提取的无机磷(Olsen-P)是可被植物吸收利用的有效磷.利用磷酸盐中~(18)O和~(16)O组成(δ~(18)O-P)开展土壤磷来源示踪和磷循环转化,具有重要意义.选择0.5 mol·L~(-1)Na HCO_3(pH 8.5)溶液并加入无磷活性炭提取土壤磷,通过Mg(OH)_2-PO_4共沉淀、磷酸铈沉淀等过程分离纯化其中磷酸盐,获得磷酸银沉淀,利用元素分析仪-稳定性同位素比例质谱仪测定氧同位素组成δ~(18)O-P值.结果表明:分离纯化沉淀3个关键过程中磷酸盐的回收率均能达到93%以上,损失较少,未出现氧同位素分馏.X射线衍射仪和氧含量测定表明,实验获取的磷酸银样品纯度较高.加入无磷活性炭可有效去除有机质对δ~(18)O-P测定影响.供试黑土和潮土中碳酸氢钠提取态土壤无机磷酸盐δ~(18)O-P值分别为17.64‰±1.03‰和18.20‰±0.83‰,差异不明显.本文建立土壤碳酸氢钠提取态无机磷酸盐中氧同位素分析测定方法,为农田土壤中磷的循环转化及其溯源研究提供技术支撑.
The inorganic phosphorus (Olsen-P) extracted by sodium bicarbonate in the soil is a kind of available phosphorus which can be absorbed and used by plants. Soil (~ 18) O and ~ (16) O Phosphorus source tracing and phosphorus cycle transformation are of great significance.Phosphorus was extracted from soil by adding 0.5 mol·L -1 Na HCO_3 (pH 8.5) solution and adding phosphorus-free activated carbon, and then was precipitated by Mg (OH) 2 -PO_4, Phosphate precipitation and other processes were used to separate and purify the phosphate, silver phosphate precipitate was obtained, and the δ ~ (18) OP value of oxygen isotope composition was determined by elemental analysis and isotope ratio mass spectrometry.The results showed that during the three key processes of separation and purification, Phosphate recovery rate can reach more than 93%, less loss, no oxygen isotope fractionation.X-ray diffraction and oxygen content determination showed that the experiment obtained high purity silver phosphate samples.Adding phosphorus-free activated carbon can effectively remove organic matter (18) OP in the black soil and the alluvial soil, the OP value of soil inorganic phosphate in the black soil and the alluvial soil were 17.64 ‰ ± 1.03 ‰ and 18.20 ‰ ± 0.83 ‰, respectively, with no significant difference In this paper, the determination of oxygen isotope in inorganic sodium bicarbonate extracted soil was established Method, providing technical support for the research on the cycle transformation and traceability of phosphorus in farmland soils.