New insights into organic carbon stabilization in soil macroaggregates: An in situ study by optical microscopy and SEM-EDS technique

• Published in: Geoderma 2021-09, Vol.397, p.115101, Article 115101
• Main Authors: Guidi, Patrizia, Falsone, Gloria, Wilson, Clare, Cavani, Luciano, Ciavatta, Claudio, Marzadori, Claudio
• Format: Article
• Language: English
• Subjects: Aggregate thin sections; Macroaggregate size; Optical microscopy; Organo-mineral interactions; Physical occlusion; SEM-EDS
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2021.115101

•Soil macroaggregates (4–1 and 1–0.25 mm) thin sections have been investigated.•Optical microscopy and SEM-EDS allowed the in situ analysis of OM in macroggregates.•Both physical occlusion and mineral interactions stabilized OM in macroaggregates.•The highest OM stabilization by both mechanisms was in fine macroaggregates.•In fine macroaggregate, both OM accumulation and functionality maintenance occurred. The purpose of this study was to investigate the in situ characterization of organic matter (OM) within soil macroaggregates, and to assess the relationships between OM characteristics and macroaggregate size indicating different OM stabilization mechanisms. Optical micro-morphological investigations, coupled to SEM-EDS (scanning electron microscopy and energy X-ray spectroscopy) technique, were carried out on thin sections of 1–4 and 0.25–1 mm soil aggregates (coarse and fine macroaggregates, respectively) from 0 to 20 cm soil layer corresponding to A horizon of four different sites in which soil structure were not disturbed by tillage. The intraggregate porosity, measured by image analysis of four different size classes (200 µm), showed that fine macroaggregates were significantly less porous (3.70–6.71% of total porosity) and had higher presence of the finest pore class (