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Haberler, A.* ; Lei, K.* ; Buegger, F. ; Bucka, F.B.* ; Just, C.*

Sodium hexametaphosphate and ultrasonication − Comparing chemical and physical dispersion methods for soil organic matter fractionation.

Geoderma 474:118028 (2026)
Verlagsversion Forschungsdaten DOI
Open Access Hybrid
Creative Commons Lizenzvertrag
Soil organic matter (SOM) fractionation into particulate organic matter (POM) and mineral-associated organic matter (MAOM) is widely applied to investigate soil organic carbon (SOC) stabilization and turnover, yet the choice of dispersion method strongly influences fractionation outcomes. This study tested a chemical dispersion approach using sodium hexametaphosphate (Na-HMP) and compared it with mechanical ultrasonication at 450 J mL−1 (US450), previously shown to be effective. Method performance was assessed based on mass and organic carbon (OC) recovery, reproducibility, and the quality of fraction separation, the latter assessed using natural 13C abundance in soils transitioning from C3 to C4 vegetation. Both methods achieved high mass and OC recoveries (>90 %) with low variability between replicates (median coefficient of variation (CV) < 5 %), indicating that either dispersion approach can be applied reproducibly. However, significant differences in fraction allocation were observed: Na-HMP yielded higher mass and OC contributions in the POM fraction at several sites, whereas US450 consistently promoted a more MAOM-dominated distribution. The proportion of C4-derived carbon (C) differed strongly between POM and MAOM for both methods; however, the capacity to resolve C pools based on δ13C signatures was significantly higher under Na-HMP, attributed to Na-HMP weakening organo-mineral associations and mobilizing mineral-bound OC. While this reflects chemical redistribution of organic matter (OM) between fractions rather than a strictly physical size-based separation, it nonetheless sharpened the isotopic contrast between POM and MAOM. Overall, US450 is recommended for size-based separation and aggregate disruption, whereas Na-HMP is preferred for maximizing isotopic contrast and isolating pools with distinct turnover rates. The chemical mobilization of OM observed under Na-HMP suggests that mineral-associated OC may be sensitive to ionic disturbances, a pattern that warrants further investigation in the context of salt-affected or sodic soils.
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Publikationstyp Artikel: Journalartikel
Dokumenttyp Wissenschaftlicher Artikel
Schlagwörter Fractionation ; Organic Matter ; Dispersion (optics) ; Soil Organic Matter ; Total Organic Carbon ; Fraction (chemistry) ; Sonication ; Soil Water ; Sodium Hexametaphosphate; Carbon Fractions; Temperate Soils; Stabilization; Mechanisms; Relevance; Turnover; Pools; Associations; Respiration; Abundance
ISSN (print) / ISBN 0016-7061
e-ISSN 1872-6259
Zeitschrift Geoderma
Quellenangaben Band: 474, Heft: , Seiten: , Artikelnummer: 118028 Supplement: ,
Verlag Elsevier
Verlagsort Radarweg 29, 1043 Nx Amsterdam, Netherlands
Begutachtungsstatus Peer reviewed
Institut(e) Research Unit Environmental Simulation (EUS)