Abstract Phosphate rocks (PRs) used in fertilizer production contain uranium (U), which enters agricultural soils through phosphorus fertilization. However, our knowledge is still limited and cannot explain the different levels of U contamination found in agricultural systems. The paper reviewed the spatial and temporal U variations in PRs to obtain a comprehensive overview of U levels in various PRs worldwide and to investigate why U concentrations in igneous PRs are significantly lower compared to sedimentary PRs, and why less U is present in old sedimentary PRs (Precambrian-Cambrian) than in younger PRs (Ordovician-Neogene). In addition, the natural oxygen isotope compositions of phosphate (δ18Op) in various PRs were determined to identify their origins in relation to their U concentration. The δ18Op values differed among igneous PRs, old sedimentary PRs, and younger sedimentary PRs. Generally, the PRs with low δ18Op values had low U concentrations. In igneous PRs, low U concentrations were due to the lack of secondary U enrichment processes after rock formation, with low δ18Op values resulting from limited isotope fractionation at high temperature. Conversely, in sedimentary PRs, both U concentrations and δ18Op values were influenced by paleoclimate and paleogeographic features. Overall, there is a time-dependent coincidence of processes altering U concentration and δ18Op signatures of sedimentary PRs in a similar direction.

中文翻译：

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磷矿中铀浓度和氧稳定同位素的“共同演化”

摘要 用于肥料生产的磷矿 (PRs) 含有铀 (U)，它通过施磷肥进入农业土壤。然而，我们的知识仍然有限，无法解释农业系统中发现的不同水平的 U 污染。该论文回顾了 PR 的空间和时间 U 变化，以全面了解全球各种 PR 中的 U 水平，并研究为什么火成岩 PR 中的 U 浓度与沉积 PR 相比显着较低，以及为什么旧沉积 PR 中的 U 较少（前寒武纪-寒武纪）比年轻的 PR（奥陶纪-新近纪）。此外，还确定了各种 PR 中磷酸盐 (δ18Op) 的天然氧同位素组成，以确定它们与 U 浓度相关的来源。δ18Op 值在火成岩 PR 之间不同，老沉积 PR 和年轻沉积 PR。通常，具有低 δ18Op 值的 PR 具有低 U 浓度。在火成岩 PR 中，低 U 浓度是由于在岩石形成后缺乏二次 U 富集过程，低 δ18Op 值是由于高温下有限的同位素分馏造成的。相反，在沉积 PRs 中，U 浓度和 δ18Op 值都受古气候和古地理特征的影响。总体而言，在类似方向上改变沉积 PR 的 U 浓度和 δ18Op 特征的过程存在时间依赖的巧合。δ18Op 值低，这是由于高温下有限的同位素分馏造成的。相反，在沉积 PRs 中，U 浓度和 δ18Op 值都受古气候和古地理特征的影响。总体而言，在类似方向上改变沉积 PR 的 U 浓度和 δ18Op 特征的过程存在时间相关的巧合。δ18Op 值低，这是由于高温下有限的同位素分馏造成的。相反，在沉积 PRs 中，U 浓度和 δ18Op 值都受古气候和古地理特征的影响。总体而言，在类似方向上改变沉积 PR 的 U 浓度和 δ18Op 特征的过程存在时间依赖的巧合。