Recent weathering promotes C storage inside large phyllosilicate particles in forest soil

Mineral weathering in soils is expected to promote chemical and physical interactions between soil organic matter mineral phases, which are known enhance the protection of from decomposition. The investigation mineral-organic associations (MOAs) formation during therefore crucial understanding carbon storage processes soils. Until now studies have been mainly conducted by building inferences characteristics, through short-term laboratory experiments simplified conditions, or over very long-term time scales using chronosequences. Weathering can significantly alter matrix at annual timescale, but knowledge regarding MOA occurring situ, short first stage lacking. To fill this gap, we performed a mesh bag incubation containing large Na-saturated carbon-free vermiculite particles (200–400 µm size) acidic Douglas-fir forest, Beaujolais area (France). bags were deposited interface forest floor soil, where intense occurs. After 20 years incubation, weathered collected characterized macroscale (X ray diffraction physicochemical analyses), microscale (scanning electron microscopy-SEM imaging element mapping) nanoscale (transmission microscopy-TEM imaging, mapping speciation energy loss spectroscopy-EELS) on focus ion beam (FIB) section exposing inside particles. Cation exchange capacity, exchangeable cations elemental analysis showed important changes after incubation. initial Na pool was completely depleted. cation capacity strongly decreased 178.1 cmolc kg−1 49.2 due interlayer hydroxylation vermiculite. budget indicated 10% dissolution an (C) enrichment 5 mg g−1. Microscope images control (nonincubated) flat, smooth surface morphology with no detected C. In contrast, 20-year irregular outer- inner-surfaces marked multiple cracks dissolution. Some nano- exfoliation spaces filled C observed association Ca occurred spaces. also entrapped nanocrystalline Mn oxides (hausmannite) K-rich aluminosilicates, precipitated micro-sized These observations that altered both mediated binding entrapment. functional groups revealed EELS spectroscopy differed This study method provides evidence new driving phyllosilicate their recent weathering, could contribute stabilization.