FT-IR spectroscopy analysis of HF-treated mineral soils, a direct approach for deciphering organo-mineral interactions

Soil organic matter (SOM) constitutes roughly 60% organic carbon (OC) and therefore plays a crucial role in regulating global climate. However, our understanding of the long-term dynamics of the soil carbon pool remains constrained by limitations in analytical approaches capable of providing high resolution molecular-level information from arguably the most complex biomaterial on the planet. In this contribution, we combine hydrofluoric acid (HF) treatment with a spectroscopic approach as a strategy to provide refined molecular-level information on the interactions between soil minerals and SOM. Critically, we have not seen the use of this combined approach anywhere in the literature and strongly believe that it could allow us to improve our overall understanding to the mechanisms and pathways that regulate SOM transformation. Results clearly illustrates which organic structures are preferentially adsorbed to soil minerals and are likely to be protected from degradation, as well as spatial co-variations of SOM with specific mineral components such as Al(3+), Si(4+) and dibasic cations such as Mg(2+)as a function of their importance in the interaction process. • Soil samples were collected from different land-use types in rural farming communities of the Upper Rio Grande Valley. • Samples were oven dried, disaggregated, sieved, treated with 10% HF, rinsed and oven dried. • Oven dried samples were subjected to Mid–infrared (4000–400 cm(−1)), XRD and ED-XRF analyses.