Rothamsted Research, North Wyke, Okehampton, EX20 2SB, UK.
Queen's School of Engineering, University of Bristol, Senate House, Tyndall Avenue, Bristol, BS8 1TH, UK.
Rapid Commun Mass Spectrom. 2018 May 15;32(9):703-710. doi: 10.1002/rcm.8092.
Phosphorus losses from agriculture pose an environmental threat to watercourses. A new approach using the stable oxygen isotope ratio of oxygen in phosphate (δ O value) may help elucidate some phosphorus sources and cycling. Accurately determined and isotopically distinct source values are essential for this process. The δ O values of animal wastes have, up to now, received little attention.
Phosphate (PO ) was extracted from cattle faeces using anion resins and the contribution of microbial PO was assessed. The δ O value of the extracted PO was measured by precipitating silver phosphate and subsequent analysis on a thermal conversion elemental analyser at 1400°C, with the resultant carbon monoxide being mixed with a helium carrier gas passed through a gas chromatography (GC) column into a mass spectrometer. Faecal water oxygen isotope ratios (δ O values) were determined on a dual-inlet mass spectrometer through a process of headspace carbon dioxide equilibration with water samples.
Microbiological results indicated that much of the extracted PO was not derived directly from the gut fauna lysed during the extraction of PO from the faeces. Assuming that the faecal δ O values represented cattle body water, the predicted pyrophosphatase equilibrium δ O (Eδ O ) values ranged between +17.9 and +19.9‰, while using groundwater δ O values gave a range of +13.1 to +14.0‰. The faecal δ O values ranged between +13.2 and +15.3‰.
The fresh faecal δ O values were equivalent to those reported elsewhere for agricultural animal slurry. However, they were different from the Eδ O value calculated from the faecal δ O value. Our results indicate that slurry PO is, in the main, derived from animal faeces although an explanation for the observed value range could not be determined.
农业中的磷流失对水道构成了环境威胁。一种新的方法利用磷酸盐中氧的稳定氧同位素比值（δ O 值），可以帮助阐明一些磷的来源和循环。准确确定和具有同位素特征的源值对于这一过程至关重要。迄今为止，动物废物的 δ O 值一直受到关注。
使用阴离子树脂从牛粪便中提取磷酸盐（PO ），并评估微生物 PO 的贡献。通过沉淀磷酸银，随后在 1400°C 的热转换元素分析仪上进行分析，测量提取的 PO 的 δ O 值，所得的一氧化碳与氦载气混合，通过气相色谱（GC）柱进入质谱仪。通过粪便水氧同位素比值（δ O 值）在双入口质谱仪上测定，通过与水样的二氧化碳平衡过程进行。
微生物学结果表明，从粪便中提取 PO 时，大部分提取的 PO 并非直接来自肠道动物裂解。假设粪便 δ O 值代表牛体水，则预测焦磷酸酶平衡 δ O（Eδ O）值范围在+17.9 到+19.9‰之间，而使用地下水 δ O 值则给出+13.1 到+14.0‰的范围。粪便 δ O 值范围在+13.2 到+15.3‰之间。
新鲜粪便的 δ O 值与其他地方报道的农业动物粪浆的 δ O 值相当。然而，它们与从粪便 δ O 值计算出的 Eδ O 值不同。我们的结果表明，粪浆 PO 主要来自动物粪便，尽管无法确定观察到的数值范围的解释。
