Chemical Fractionation

Chemical fractionation methods can be divided into extraction, hydrolysis and oxidation. Furthermore, chemicals are also used to destroy minerals and thereby release organic matter. Extraction is done in water, aqueous solutions of differing ionic strength, organic solvents or bases, such as NaOH or Na4P2O7. Hydrolysis is done with water (hot or cold) or acids such as HCl or HF. Both procedures have the advantage, that they yield purely organic fractions that are free of mineral particles. Hydrolysis is to isolate fractions with distinct chemical properties, which are believed to be important for their behavior in the soil. In contrast, oxidation is conducted to mimic strong exo-enzymatic decay and thus to isolate a fraction that is stabilized against decomposition. NaOCl- or H2O2-Oxidation resistant SOC is typically found to be centuries to millennia older than the bulk SOC, which indicates its high stability. In the SOMfractionation study, only two pure chemical fractionation methods were used. Further references are listed in the review of (von Lützow et al., 2007).

References

von Lützow, M., Kögel-Knabner, I., Ekschmitt, K., Flessa, H., Guggenberger, G., Matzner, E., and Marschner, B., 2007. SOM fractionation methods: Relevance to functional pools and to stabilization mechanisms, Soil Biol. Biochem., 39, 2183–2207. DOI: 10.1016/j.soilbio.2007.03.007