Soil wet chemical extractions are used to determine plant available potassium (K); yet problems with K bioavailability still persist in soils. Bioavailability is directly related to how elements are bonded and coordinated to the solid phases of soil. However, there is a critical knowledge gap with respect to identifying the in situ, solid-phase K coordination environments in soils treated with wet chemical extractions. Synchrotron-based X-ray absorption spectroscopy (XAS) measures the molecular coordination environment of elements and has been used here to study K chemistry in two agricultural field soils. The objective of this work is to pair XAS with wet chemical K extractions and analyze changes in the coordination environment of K throughout the soil profile. Soil profiles collected down to 1.2 m of a loamy sand and a sandy clay loam were treated with six different extraction methods: (1) Mehlich III, (2) ammonium acetate, (3 & 4) Haney, Haney, Hossner, and Arnold 1 and 2, (5) citrate dithionite, and (6) water extractable potassium. The residual solid was analyzed using XAS and X-ray diffraction (XRD). Citrate dithionite extracted the largest amount of K (1860 mg kg⁻¹), and the water extraction removed the least (30 mg kg⁻¹). XAS and XRD indicate K sources in these soils are illite, illite–smectite, smectite, and potassium feldspar. A Linear Combination Fit (LCF) approach indicated changes of interest in the post-edge region of the K, K-edge XANES spectra due to the Mehlich extraction. XANES data indicate that the Mehlich extraction can remove loosely bound K and dislodge a portion of K from interlayer space of illite and illite–smectite. This is significant because the Mehlich extraction is effectively decreasing the number of coordinating O atoms surrounding K and causing a dampening in the oscillations of the XANES spectra in the post-edge region (3,620–3,650 eV). The dislodgement of K due to the Mehlich III extraction indicates that the inner-sphere bonds that K forms to the siloxane surfaces in the interlayer space can be broken, and K can become more hydrated with water molecules also present in the interlayer space. This dampening was dependent on soil texture, was more significant in the coarser textured soil, and would indicate an increased accommodation of K by montmorillonite or an increase in K hydration in illite–smectite. The dampening resulted in an average increase in K intercalated in montmorillonite interlayer spaces by 25% in Mehlich treated samples according to the LCF results. Future studies involving K sorption to silicon and aluminum oxides will further clarify behavior of K on mineral surfaces, particularly during surface precipitation.

土壤湿化学提取物用于测定植物有效钾（K）；然而，钾的生物有效性问题仍然存在于土壤中。生物利用度与元素如何与土壤的固相结合和协调直接相关。然而，在确定用湿法化学萃取处理的土壤中的原位固相 K 配位环境方面存在着严重的知识空白。基于同步加速器的 X 射线吸收光谱 (XAS) 测量元素的分子配位环境，并已用于研究两种农田土壤中的 K 化学。这项工作的目的是将 XAS 与湿化学 K 提取配对，并分析整个土壤剖面中 K 的协调环境的变化。土壤剖面收集到 1。用六种不同的提取方法处理 2 m 的壤质砂和砂质粘土壤土：(1) Mehlich III，(2) 乙酸铵，(3 & 4) Haney、Haney、Hossner 和 Arnold 1 和 2，(5 ) 柠檬酸连二亚硫酸盐，和 (6) 水萃取钾。使用 XAS 和 X 射线衍射 (XRD) 分析残余固体。柠檬酸连二亚硫酸钾提取量最大（1860 mg kg^-1 )，水萃取去除的最少 (30 mg kg ^-1）。XAS 和 XRD 表明这些土壤中的钾源是伊利石、伊利石-绿土、绿土和钾长石。线性组合拟合 (LCF) 方法表明，由于 Mehlich 提取，在 K、K 边 XANES 光谱的后边区域中感兴趣的变化。XANES 数据表明，Mehlich 提取可以去除松散结合的 K 并将一部分 K 从伊利石和伊利石-蒙脱石的层间空间中移出。这很重要，因为 Mehlich 提取有效地减少了 K 周围的配位 O 原子的数量，并导致后边缘区域 (3,620–3,650 eV) 中 XANES 光谱的振荡衰减。由于 Mehlich III 萃取导致 K 的移位表明 K 在层间空间中与硅氧烷表面形成的内球键可以被破坏，和 K 可以变得更加水合，水分子也存在于层间空间中。这种抑制取决于土壤质地，在质地较粗的土壤中更为显着，这表明蒙脱石对钾的吸收增加或伊利石-蒙脱石中钾水合的增加。根据 LCF 结果，在 Mehlich 处理的样品中，阻尼导致嵌入蒙脱石层间空间的 K 平均增加 25%。未来涉及 K 吸附到硅和氧化铝的研究将进一步阐明 K 在矿物表面上的行为，特别是在表面沉淀期间。并且表明蒙脱石对K的吸收增加或伊利石 - 蒙脱石中K水合的增加。根据 LCF 结果，在 Mehlich 处理的样品中，阻尼导致嵌入蒙脱石层间空间的 K 平均增加 25%。未来涉及 K 吸附到硅和氧化铝的研究将进一步阐明 K 在矿物表面上的行为，特别是在表面沉淀期间。并且表明蒙脱石对K的吸收增加或伊利石 - 蒙脱石中K水合的增加。根据 LCF 结果，在 Mehlich 处理的样品中，阻尼导致嵌入蒙脱石层间空间的 K 平均增加 25%。未来涉及 K 吸附到硅和氧化铝的研究将进一步阐明 K 在矿物表面上的行为，特别是在表面沉淀期间。