The influence of weathering processes on labile and stable organic matter in Mediterranean volcanic soils |
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| Authors: | Vito Barbera Salvatore Raimondi Markus Egli Michael Plötze |
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| Institution: | 1. Division of Natural Resource Management, ICAR- Research Complex for NEH Region, Umiam, Shillong, Meghalaya, India;2. Global Centre for Environmental Remediation (GCER), Advanced Technology Centre, Faculty of Science, The University of Newcastle, Callaghan, Newcastle, NSW, Australia;3. Department of Agronomy, 2004 Throckmorton Plant Sciences Center, Kansas State University, Manhattan, KS, United States;4. Division of Soil Science and Agricultural Chemistry, ICAR-Indian Agricultural Research Institute (IARI), New Delhi, India;5. ICAR-National Academy of Agriculture Research Management, Hyderabad, Telangana, India;6. Department of Soil Science, Kerala Forest Research Institute, Thrissur, Kerala, India;7. Laboratory of Soil- and Groundwater-Management, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water- and Waste-Management, University of Wuppertal, Wuppertal, Germany;8. Department of Environment, Energy and Geoinformatics, Sejong University, Seoul, Republic of Korea;9. Divison of Environmental Science and Ecological Engineering, Korea Biochar Research Center, Korea University, Seoul, South Korea;10. Biochar Engineering Technology Research Center of Guangdong Province, School of Environment and Chemical Engineering, Foshan University, Foshan, China;11. Key Laboratory of Soil Contamination Bioremediation of Zhejiang Province, Zhejiang A & F University, Hangzhou, China;12. Department of Animal, Plant and Soil Sciences, Centre for AgriBioscience, La Trobe University (Melbourne Campus), Melbourne, VIC, Australia;13. Institute of Surface-Earth System Science, Tianjin University, Tianjin, China;14. Cooperative Extension Service, Central State University, Wilberforce, OH, United States;1. Dipartimento di Biologia, Ecologia e Scienze della Terra (DiBEST), Università della Calabria, Via P. Bucci, Cubo 15B, 87036 Arcavacata di Rende (CS), Italy;2. Istituto di Ricerca per la Protezione Idrogeologica (IRPI), Consiglio Nazionale delle Ricerche (CNR), Via Cavour 6, 87036 Rende (CS), Italy;3. Ente Parco Nazionale della Sila, Via Nazionale, 87055 Lorica, San Giovanni in Fiore (CS), Italy |
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| Abstract: | The relationship and mechanisms among weathering processes, cation fluxes, clay mineralogy, organic matter composition and stability were studied in soils developing on basaltic material in southern Italy (Sicily). The soils were transitions between Phaeozems and Vertisols. Intense losses of the elements Na, Ca and Mg were measured indicating that weathering has occurred over a long period of time. The main weathering processes followed 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 soils suggests that (macro)aggregates have formed due to physical or electrostatic interactions between the 1:1 clay minerals and oxides. The stability of organic matter was investigated with a H2O2-treatment that assumes that chemical oxidation mimics the natural oxidative processes. The ratio of C after 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 poorly crystalline Fe or Al phases. A part of this fraction (most probably proteins) was bound to crystalline Fe-oxides. In contrast, the oxidisable fraction showed a strong relationship with poorly crystalline oxyhydroxides and kaolinite. Surprisingly, smectite did not contribute to the stabilisation of any 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 oxyhydroxides and kaolinite and 2) the formation of a refractory fraction enriched in aliphatic compounds. |
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