Hydrophobicity of an Entisol under loblolly pine (Pinus taeda) plantation

Abstract

The understanding of soil carbon stabilization processes can be very useful in the development of mitigation techniques for CO2 emissions and global warming. The greater the hydrophobicity of soil organic matter the more stabilized soil organic carbon. Therefore,  hydrophobicity can be a sensitive index to characterize the "˜quality´ of soil organic matter. In this context, the present work aimed to characterize the chemical  structures of humic acids collected at three different depths in a hydrophobic Entisol (Neossolo) under  loblolly plantation. The results of spectroscopic and chemical analyses (UV-Vis, fluorescence, EPR and X-ray diffractometry) indicated that, as soil depth increased, so did the content of conjugated organic structures, aromatic groups, and free organic radicals, leading to higher humification indices. Aliphatic groups in these fractions were more concentrated in the surface layer than in deeper ones, which can be explained by the constant input of litter. The greater hydrophobicity of the surface soil sample was due to these non-humic components of the organic matter, as suberin and cutin.