Abstract Phosphorus (P) fertilizers vary considerably in contents of uranium (U), thus raising concerns regarding U accumulation in agricultural soils. We examined U concentrations in soil from three long-term field experiments with different P fertilizer applications: Rengen (P fertilizer from basic slag, grassland, Germany), Thyrow (P fertilizer from igneous phosphate rocks, arable land, Germany) and Askov (P fertilizer from igneous phosphate rocks, arable land, Denmark). Accumulation rates were low for Rengen (1.3 µg U kg−1 yr−1) and Thyrow (0.6 µg U kg−1 yr−1) in P-treated plots compared with plots without P fertilization. These accumulation rates were ten times lower than those previously reported (mean 17 µg U kg−1 yr−1). Intriguingly, concentrations of acid-extractable U in the Askov topsoil increased from 1923 to 2016, regardless of whether P was added (5.1 µg kg−1 yr−1) or not (4.7 µg kg−1 yr−1). This suggests that at least part of the accumulated U originated from other sources than P fertilizers. Total U concentrations were significantly larger in the period 1985–2016 than in the period 1938–1976 in Askov soil treated with NPK but not in soils without P fertilization. Hence, long-term P fertilizer application did increase the soil U concentrations at Askov, although at a low level. The low U accumulation rates in soils from these German and Danish long-term P fertilization experiments indicate that with current management, the soil U concentration could remain at non-critical levels even on a centennial scale. This is attributed to the historic use of P fertilizers derived from sources with low U content (igneous phosphate rocks from Finland and Kola Peninsula for Askov and Thyrow, respectively, and basic slag for Rengen). Hence, U accumulation due to long-term P fertilization in agricultural soils may be alleviated by using phosphate rocks from low U sources in P fertilizer production.

中文翻译：

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德国和丹麦长期施肥试验土壤中非临界铀的积累

摘要 磷 (P) 肥料中铀 (U) 的含量差异很大，因此引起了人们对农业土壤中 U 积累的担忧。我们从三个长期田间试验中使用不同的磷肥检测了土壤中的 U 浓度：Rengen（来自碱性矿渣，草地，德国的磷肥），Thyrow（来自火成磷岩，耕地，德国的磷肥）和 Askov（P来自火成岩磷酸盐岩的肥料，耕地，丹麦）。与未施磷的地块相比，磷处理地块中 Rengen (1.3 µg U kg−1 yr−1) 和 Thyrow (0.6 µg U kg−1 yr−1) 的积累率较低。这些积累率比以前报告的低十倍（平均 17 µg U kg−1 yr−1）。有趣的是，从 1923 年到 2016 年，阿斯科夫表土中可酸提取的 U 浓度增加，无论是否添加 P (5.1 µg kg-1 yr-1) 或不添加 (4.7 µg kg-1 yr-1)。这表明至少部分累积的 U 来自除磷肥之外的其他来源。在用 NPK 处理的 Askov 土壤中，1985-2016 年期间的总 U 浓度显着高于 1938-1976 年期间，但在未施磷肥的土壤中则不然。因此，长期施用磷肥确实增加了 Askov 的土壤 U 浓度，尽管水平较低。这些德国和丹麦的长期施磷试验表明，土壤中的低 U 积累率表明，通过目前的管理，即使在百年规模上，土壤 U 浓度也可以保持在非临界水平。这归因于历史上使用源自低 U 含量来源的 P 肥料（分别来自芬兰和科拉半岛的 Askov 和 Thyrow 的火成岩磷酸盐岩，以及 Rengen 的碱性矿渣）。因此，通过在磷肥生产中使用来自低 U 源的磷矿，可以减轻农业土壤中长期磷肥导致的 U 积累。