Influence of soil porous microstructure on the distribution and transport of soil organic matter: a comparison of different soil types

A cultivated and a wild soil from an agricultural research site from the state of Washington site as well as at least one soil from a forest-to-wetland transition zone from Maryland were characterized for pore structure and soil organic matter (SOM) content, distribution, and transport at the Environmental Molecular Sciences Laboratory (EMSL). From x-ray computed tomography (XCT) imaging the soil porosity and pore network connectivity information was obtained. Hydraulic experiments were used to determine the mobility and desorption parameters of SOM. From effluent as well as extracted samples collected before, during, and after "stop-flow" experiments, total organic carbon and total nitrogen content were analyzed as well as Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR/MS) based analyses were carried out for SOM composition (organic groups). We present results on the comparison of soil porous structure and its influence on the stabilization and transport of SOM. We also show how our pore network geometry data and resulting probability distribution functions along with SOM distribution and chemistry information will be used to predict diffusion-limited soil respiration in different soils in a reactive transport model.