The influence of weathering processes on labile and stable organic matter in Mediterranean volcanic soils.

Salvatore Raimondi, Markus Egli, Michael Plötze, Vito Barbera

Risultato della ricerca: Articlepeer review

18 Citazioni (Scopus)

Abstract

The relationship and mechanisms among weathering processes, cation fluxes, clay mineralogy, organic matter composition and stability werestudied in soils developing on basaltic material in southern Italy (Sicily). The soils were transitions between Phaeozems and Vertisols. Intense lossesof the elements Na, Ca and Mg were measured indicating that weathering has occurred over a long period of time. The main weathering processesfollowed the sequence: amphibole, mica, volcanic glass or if ash was the primary source→smectite→interstratified smectite–kaolinite→kaolinite.Kaolinite formation was strongly related to high Al, Mg and Na losses. The good correlation between oxyhydroxides and kaolinite in the soilssuggests that (macro)aggregates have formed due to physical or electrostatic interactions between the 1:1 clay minerals and oxides. The stability oforganic matter was investigated with a H2O2-treatment that assumes that chemical oxidation mimics the natural oxidative processes. The ratio of Cafter the H2O2 treatment to the total organic C ranged from 1–28%. No correlation between clay content and organic matter (labile or stable fraction)was found. The refractory organic fraction was enriched in aliphatic compounds and did not greatly interact with the kaolinite, smectite or poorlycrystalline Fe or Al phases. A part of this fraction (most probably proteins) was bound to crystalline Fe-oxides. In contrast, the oxidisable fractionshowed a strong relationship with poorly crystalline oxyhydroxides and kaolinite. Surprisingly, smectite did not contribute to the stabilisation ofany of the organic C fractions. The stabilisation of organic matter in the soils has, therefore, two main mechanisms: 1) the protection of labile(oxidisable with H2O2) organic matter, including also aromatic-rich compounds such as charcoal, by the formation of aggregates with oxyhydroxidesand kaolinite and 2) the formation of a refractory fraction enriched in aliphatic compounds.© 2007 Elsevier B.V. All rights reserved.Keywords: Weathering; Mass balance; Clay mineralogy; Organic matter stability; Mediterranean soils; FT-IR spectroscopy
Lingua originaleEnglish
pagine (da-a)191-205
RivistaGeoderma
Volume143
Stato di pubblicazionePublished - 2008

All Science Journal Classification (ASJC) codes

  • Soil Science

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