Zinc (Zn) deficiency is a widespread nutritional problem in human populations, especially in sub-Saharan Africa (SSA). The Zn concentration of crops consumed depends in part on the Zn status of the soil. Improved understanding of factors controlling the phyto-availability of Zn in soils can contribute to potential agronomic interventions to tackle Zn deficiency, but many soil types in SSA are poorly studied.Soil samples (n=475) were collected from a large part of the Amhara Region of Ethiopia, where there is widespread Zn deficiency. Zinc status was quantified by measuring several fractions, including the pseudo-total (aqua regia digestion; Zn_Tot), available (DTPA (diethylenetriamine pentaacetate) extractable; Zn_DTPA), soluble (dissolved in 0.01 M Ca(NO₃); Zn_Soln) and isotopically exchangeable Zn, using the enriched stable Zn isotope ⁷⁰Zn (Zn_E). Soil geochemical properties were assessed for their influence on Zn lability and solubility. A parameterized geochemical assemblage model (Windermere Humic Aqueous Model – WHAM) was also employed to predict the solid phase fractionation of Zn in tropical soils rather than using sequential chemical extractions.Zn_Tot ranged from 14.1 to 291 mg kg⁻¹ (median = 100 mg kg⁻¹), whereas Zn_DTPA in the majority of soil samples was less than 0.5 mg kg⁻¹, indicating widespread phyto-available Zn deficiency in these soils. The labile fraction of Zn in soil (Zn_E as % Zn_Tot) was low, with median and mean values of 4.7 % and 8.0 %, respectively. Labile Zn partitioning between the solid and the solution phases of soil was highly pH dependent, where 94 % of the variation in the partitioning coefficient of ⁷⁰Zn was explained by soil pH. Similarly, 86 % of the variation in Zn_Soln was explained by soil pH.Zinc distribution between adsorbed Zn_E and Zn_Soln was controlled by pH. Notably, Zn isotopic exchangeability increased with soil pH. This contrasts with literature on contaminated and urban soils and may arise from covarying factors, such as contrasting soil clay mineralogy across the pH range of the soils used in the current study. These results could be used to improve agronomic interventions to tackle Zn deficiency in SSA.

中文翻译：

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土壤性质对埃塞俄比亚土壤中锌不稳定性和溶解度的影响——同位素稀释研究

锌 (Zn) 缺乏症是人类普遍存在的营养问题，尤其是在撒哈拉以南非洲 (SSA)。消耗的作物的锌浓度部分取决于土壤的锌状况。更好地了解控制土壤中锌的植物有效性的因素有助于潜在的农艺干预来解决锌缺乏症，但对 SSA 中的许多土壤类型的研究很少。土壤样本 ( n = 475 ) 是从阿姆哈拉的大部分地区收集的埃塞俄比亚地区，普遍缺锌。锌状态通过测量几个部分来量化，包括假总量（王水消化；Zn _Tot），可用的（DTPA（二亚乙基三胺五乙酸盐）可提取；Zn _DTPA)，可溶（溶解在 0.01 M Ca( NO ₃ )；Zn _{Soln 中}）和同位素交换 Zn，使用富集的稳定 Zn 同位素⁷⁰ Zn (Zn _E )。评估了土壤地球化学特性对锌不稳定性和溶解度的影响。还采用参数化地球化学组合模型（Windermere Humic Aqueous Model – WHAM）来预测热带土壤中 Zn 的固相分馏，而不是使用连续化学提取_{。Zn Tot}范围为 14.1 至 291 mg kg ^-1（中值 =  100 mg kg ^-1 )，而大多数土壤样品中的Zn _DTPA小于 0.5 mg kg^-1，表明这些土壤中普遍存在植物可利用锌缺乏。土壤中锌的不稳定部分（锌_E占 Zn _{Tot 的}百分比）很低，中值和平均值分别为 4.7% 和 8.0%。土壤固相和溶液相之间不稳定的锌分配高度依赖于 pH 值，其中⁷⁰ Zn分配系数的 94% 的变化是由土壤 pH 值解释的。类似地，在锌的变化值的86％ _SOLN通过土壤pH.Zinc分布吸附锌之间解释_Ë和Zn _SOLN由 pH 值控制。值得注意的是，Zn 同位素交换性随土壤 pH 值而增加。这与有关受污染土壤和城市土壤的文献形成对比，并且可能由共变因素引起，例如在当前研究中使用的土壤的 pH 值范围内对比土壤粘土矿物学。这些结果可用于改进农艺干预措施，以解决 SSA 中锌缺乏的问题。