Improving our knowledge of soil formation is critical so that we can better understand the first-order controls on soil thickness and more effectively inform land-management decisions. Cosmogenic radionuclide analysis has allowed soil scientists to more accurately constrain the rates at which soils form from bedrock. In such analysis, the concentration of an isotope, such as Beryllium-10, is measured from a sample of bedrock. Because this concentration is partly governed by the lowering of the bedrock-soil interface, a cosmogenic depth-profile model can be fitted to infer the bedrock and surface lowering rates compatible with the measured concentrations. Given that the bedrock-soil interface is shielded by soil, the cosmic rays responsible for the in-situ production of the radionuclide are attenuated, with attenuation rates dependent on the density profile of this soil. Many studies have assumed that soil bulk density is either equal to that of the bedrock or constant with depth. The failure to acknowledge the variations in soil bulk density means that cosmogenically derived soil formation rates previously published may be under- or overestimates. Here, we deploy a new model called "CoSOILcal" to a global compilation of cosmogenic analyses of soil formation and, by making use of estimated bulk density profiles, recalculate rates of soil formation to assess the sensitivity to this important parameter. We found that where a soil mantle >0.25 m overlies the soil-bedrock interface, accounting for the soil bulk density profile brings about a significantly slower rate of soil formation than that previously published. Moreover, the impact of using bulk density profiles on cosmogenically derived soil formation rates increases as soil thickens. These findings call into question the accuracy of our existing soil formation knowledge and we suggest that future cosmogenic radionuclide analysis must consider the bulk density profile of the overlying soil. Highlights The effect of heterogeneities in soil bulk density on cosmogenically derived soil formation rates is unknown. Soil formation rates are recalculated using a new model to analyse the effect of density variations. Accounting for density in soils >0.25 m thickness brings about significantly slower soil formation rates. Measuring soil bulk density is essential when cosmogenically deriving soil formation rates.

中文翻译：

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宇宙成因放射性核素分析对土壤体积密度的敏感性：对土壤形成速率的影响

提高我们对土壤形成的了解至关重要，这样我们才能更好地了解对土壤厚度的一级控制，并更有效地为土地管理决策提供信息。宇宙成因放射性核素分析使土壤科学家能够更准确地限制土壤从基岩形成的速率。在这种分析中，同位素（例如铍 10）的浓度是从基岩样本中测量的。由于该浓度部分受基岩 - 土壤界面降低的影响，因此可以拟合宇宙成因深度剖面模型来推断与测量浓度兼容的基岩和地表降低速率。鉴于基岩-土壤界面被土壤屏蔽，负责原位产生放射性核素的宇宙射线衰减，衰减率取决于该土壤的密度分布。许多研究假设土壤容重要么等于基岩的容重，要么随深度恒定。未能承认土壤容重的变化意味着先前公布的宇宙起源土壤形成率可能被低估或高估。在这里，我们将一个名为“CoSOILcal”的新模型部署到土壤形成的宇宙成因分析的全球汇编中，并通过利用估计的体积密度剖面，重新计算土壤形成的速率以评估对这一重要参数的敏感性。我们发现，在大于 0.25 m 的土壤地幔覆盖在土壤-基岩界面上时，考虑到土壤容重剖面，土壤形成速度比以前发表的要慢得多。而且，随着土壤变厚，使用容重剖面对宇宙源土壤形成率的影响会增加。这些发现对我们现有土壤形成知识的准确性提出了质疑，我们建议未来的宇宙放射性核素分析必须考虑上覆土壤的容重分布。亮点 土壤容重的异质性对宇宙源土壤形成率的影响是未知的。使用新模型重新计算土壤形成率，以分析密度变化的影响。考虑到大于 0.25 m 厚度的土壤中的密度会导致土壤形成速率显着降低。在宇宙起源地推导土壤形成率时，测量土壤容重是必不可少的。这些发现对我们现有土壤形成知识的准确性提出了质疑，我们建议未来的宇宙放射性核素分析必须考虑上覆土壤的容重分布。亮点 土壤容重的异质性对宇宙源土壤形成率的影响是未知的。使用新模型重新计算土壤形成率，以分析密度变化的影响。考虑到大于 0.25 m 厚度的土壤的密度会导致土壤形成速率显着降低。在宇宙起源地推导土壤形成率时，测量土壤容重是必不可少的。这些发现对我们现有土壤形成知识的准确性提出了质疑，我们建议未来的宇宙放射性核素分析必须考虑上覆土壤的容重分布。亮点 土壤容重的异质性对宇宙源土壤形成率的影响是未知的。使用新模型重新计算土壤形成率，以分析密度变化的影响。考虑到大于 0.25 m 厚度的土壤的密度会导致土壤形成速率显着降低。在宇宙起源地推导土壤形成率时，测量土壤容重是必不可少的。亮点 土壤容重的异质性对宇宙源土壤形成率的影响是未知的。使用新模型重新计算土壤形成率，以分析密度变化的影响。考虑到大于 0.25 m 厚度的土壤的密度会导致土壤形成速率显着降低。在宇宙起源地推导土壤形成率时，测量土壤容重是必不可少的。亮点 土壤容重的异质性对宇宙源土壤形成率的影响是未知的。使用新模型重新计算土壤形成率，以分析密度变化的影响。考虑到大于 0.25 m 厚度的土壤的密度会导致土壤形成速率显着降低。在宇宙起源地推导土壤形成率时，测量土壤容重是必不可少的。