Abstract. 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 soil. Improved understanding of factors controlling the phyto-availability of Zn in soils can contribute to potential agronomic interventions to tackle Zn deficiency, although there are major knowledge gaps for many soil types in SSA. 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: pseudo-total (Aqua-Regia digestion; Zn_Tot), available (DTPA-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. 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 phytoavailable 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 pH controlled. 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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埃塞俄比亚土壤中锌的易溶解性-同位素稀释研究

摘要。锌（Zn）缺乏症是人类人群中普遍存在的营养问题，尤其是在撒哈拉以南非洲（SSA）中。消耗的农作物的锌浓度部分取决于土壤的锌状况。尽管对SSA中许多土壤类型存在重大知识空白，但对控制土壤中Zn的植物有效性的因素的深入理解仍有助于解决锌缺乏的潜在农学干预措施。土壤样品（n = 475）是从埃塞俄比亚阿姆哈拉地区的大部分锌缺乏地区采集的。锌的状态通过测量以下几个部分来量化：假总（Aqua-Regia消化； Zn _Tot），可用（DTPA可萃取； Zn _DTPA），可溶性（溶于0.01 M Ca（NO ₃）； Zn_SOLN）和同位素可交换使用的Zn富集稳定同位素的Zn ⁷⁰的Zn（锌_ë）。评估土壤地球化学性质对锌不稳定性和溶解度的影响。Zn _Tot介于14.1至291 mg kg ^-1（中位数= 100 mg kg ^-1），而大多数土壤样品中的_DTPA小于0.5 mg kg ^-1，表明这些土壤中普遍存在植物可用的锌缺乏症。锌在土壤中的不稳定部分（Zn _E以％Zn _Tot表示））较低，中位数和平均值分别为4.7％和8.0％。土壤中固相和溶液相之间不稳定的Zn分配高度依赖于pH值，其中⁷⁰ Zn分配系数的94％变化由土壤pH值解释。同样，土壤pH值解释了Zn _Soln中86％的变化。吸附的Zn _E和Zn _Soln之间的锌分布已控制pH。值得注意的是，锌同位素交换能力随土壤pH值的增加而增加。这与关于污染土壤和城市土壤的文献形成对比，这可能是由多种因素引起的，例如在当前研究中使用的土壤pH范围内对比土壤粘土矿物学。这些结果可用于改善农艺干预措施，以解决SSA中的锌缺乏症。