Formation and properties of mineral-organic soil interfaces as revealed by X-ray photoelectron spectroscopy

Mineral-organic interfaces represent organic matter-enriched transition zones between mineral surfaces and pore spaces. Many soil processes, including adsorption and desorption reactions, occur at these interfaces and are controlled by their physicochemical properties. A decade ago, Kleber et al. (2007) proposed the so-called ‘multilayer’ model, which assumes the presence of chemically distinct zones within natural organic matter coatings on mineral surfaces. The model assumes that organic coatings are composed of an inner contact zone followed by a zone of hydrophobic interactions and an outer kinetic zone, each zone containing distinct organic matter components (‘chemical zonation’). Although the model is currently considered as ˈstate of knowledgeˈ in terms of the composition of soil mineral-organic associations, it has never been validated experimentally. Our proposed research will therefore address the chemical composition of organic coatings as a function of environmental conditions. We analyze the morphology of organic coatings on mineral surfaces and their chemical structure using atomic force microscopy and X-ray photoelectron spectroscopy. Additionally, we explore the effect of specific environmental parameters such as pH and solution composition on the formation and composition of organic multilayers