Soil organic carbon mobility in equatorial podzols: soil column experiments


  • Merdy Patrica
  • Lucas Yves
  • Coulomb Bruno
  • Melfi Adolpho
  • Montes Célia

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Abstract. Transfer of organic carbon from topsoil horizons to deeper horizons and to water table is still little documented, in particular in equatorial environments despite the high primary productivity of the evergreen forest. Due to its complexing capacity, organic carbon also plays a key role in the transfer of metals in the soil profile and therefore in pedogenesis and for metal mobility. We were interested in equatorial podzols, which are known to play a significant role in carbon cycling. We carried out soil column experiments using soil material and percolating solution sampled in an Amazonian podzol area. The dissolved organic matter (DOM) produced in the topsoil was not able to percolate through the clayey, kaolinitic material from the deep horizons and was retained in it. When it previously percolated through the Bh material, there was production of fulvic-like, protein-like compounds and small carboxylic acids able to percolate through the clayey material and increasing the mobility of Al, Fe and Si. Podzolic processes in the Bh can therefore produce a DOM likely to be transferred to the deep water table, playing a role in the carbon balances at the profile scale, and owing to its complexing capacity, playing a role in deep horizon pedogenesis and weathering. The order of magnitude of carbon concentration in the solution percolating in depth was around 1.5–2.5 mg L−1.

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