Background: Soil represents the largest reservoir of terrestrial organic C. The Kyoto Protocol stresses the need for a fundamental understanding of basic soil biological, chemical, and physical processes that control C stabilization and release from soils. Yet, the underlying biogeochemical mechanisms for long-term stabilization of C are still not well understood, and the potential for C sequestration in soil remains unknown. Current conceptual soil organic C turnover models built on destructive macroscopic analytical approaches are not fully process-orientated and usually fail to provide explicit molecular-level information about micro- and nano-scale spatial features of organomineral assemblages to help bridge the gap between multi-scale processes. Therefore, understanding impacts of human interventions on soil health and quality, and the soils responses to climate change remains largely empirical.

Results: This presentation will attempt to provide an overview some of the efforts made by our group: (i) to identify and fingerprint the functional group composition of organic matter, (ii) to investigate the long-term impact of anthropogenic land-use and land-cover changes and some climatic parameters on the amount and molecular-level composition of SOM and associate elements in various ecosystems across the globe using a variety of specromicroscopic techniques. We will also discuss the potentials of some of the novel non-destructive high resolution micro- (Sr-FTIR) and nano-scale (STXM-NEXAFS) spectromicroscopic approaches to obtain first-hand process-oriented biogeochemical evidence about: (i) the in situ spatial arrangement of minerals, metal-ions, organic C functionalities and other architectural features of organomineral assemblages at microscopic and sub-microscopic level, and (ii) element-specific (both low Z and other metal ions) information about local structural and compositional environments of neighboring atoms and surficial interactions, micro- and nano-scale spatial heterogeneity and other molecular-level features of organomineral assemblages and long-term changes along soil gradients developed during pedogenesis.