Abstract
AbstractThree pedons of Spodosols or Spodosol‐like soils from Quebec and Ontario containing a considerable amount of acid‐oxalate extractable Al, Fe, and Si were examined in detail by additional selective chemical dissolution, x‐ray diffraction, infrared absorption, and Mössbauer methods to characterize noncrystalline and/or short‐range ordered soil mineral components. The ratio of Fe extracted by acid oxalate to Fe extracted by dithionite‐citrate was nearly unity for most of the clay samples from B and C horizons, indicating that almost all free Fe existed in noncrystalline forms. Amounts of Fe and Al extracted by acid‐oxalate were comparable to those by alkaline Tiron. However, Tiron (1,2‐dihydroxybenzene,3,5‐disulfonic acid disodium salt, C6H4Na2O8S2) generally extracted more Si than acid‐oxalate and Si was mostly concentrated in surface horizons. The difference in the amounts of Si extracted was related to the difference in solubilities of opaline silica in the acid‐oxalate and alkaline Tiron solutions. The presence of opaline silica was further supported by differential x‐ray diffraction and infrared absorption data. Noncrystalline Fe and Al were concentrated in lower horizons and in one case more Al than Fe appeared to be accumulated in slightly lower B subhorizons. Differential XRD patterns of samples from B horizons showed broad maxima at 0.33, 0.25, 0.22, 0.17, and 0.15 nm, indicating the presence of allophane and ferrihydrite. The presence of ferrihydrite was also supported by Mössbauer data.
Published Version
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