Interpretation of Ca-associated Organic Matter X-ray Spectra via Electronic Structure Simulation

Abstract:

An accurate picture of the structural features of soil organic matter (SOM) and dissolved organic matter (DOM) such as Ca²⁺ bridging and Ca-mineral-OM interactions is crucial to understanding carbon stabilization processes and carbon and nutrient cycling. Moreover, accurate models of S(D)OM at the electronic and atomistic level are needed to inform modeling efforts that include larger spatial and temporal scales in a multiscale infrastructure. Spectroscopic methods especially x-ray spectroscopies are of increasing importance in the structural characterization and speciation of S(D)OM, OM-mineral interactions, and mineralogy. Of burgeoning utility in the interpretation of the complex x-ray spectra is the use of electronic structure theories such as time-dependent density functional theory (TD-DFT). Here we present our efforts simulating the XANES spectra and spectral assignments of Ca-associated OM in calcareous sediments.