Bridging concepts on humic substances to improve our understanding of soil carbon functionality - A molecular approach

 The interactions of soil organic matter (OM) with minerals play a key role in environmental biogeochemical processes, including the bioavailability of nutrients, transport of contaminants, and OM stability in relation to the global carbon cycle. The heterogeneity and variability of soil OM make its analysis intricate. Therefore, it has traditionally been separated into several operationally defined fractions, including humic and fulvic acid. These fractions have been proven to show generic binding properties that enabled adequate predictions of metal-binding in solution and to mineral surfaces. The emerging understanding that soil OM is composed of identifiable molecules that can be ascribed to plant and microbial sources, has highlighted a scientific debate on the use of these fractions to study OM functioning in the environment. By systematically studying the molecular composition of soil OM and the fractions therein we aim to bridge the current scientific debate between biogeochemists and geochemical modellers, and thereby improve our understanding of soil OM functions in the environment. We will identify generic molecular properties of soil OM fractions, and link the results to the field-scale by interpreting the molecular composition to its source and transformations in the environment. This field-scale research provides a novel approach to explore relations between soil OM molecular- and binding properties, by considering natural processes influenced by time and space.