Molecular-level Investigation of Dissolved and Stabilized Organic Carbon in Soil
EMSL Project ID
40129
Abstract
Soils contain large amounts of organic carbon (OC) and serve as both sources and sinks for atmospheric C. However, little is known about the structural chemistry of stabilized soil OC or the mechanisms by which it is stabilized. As a result global C-cycle models treat soil OC in a rudimentary fashion, at best, if it is treated at all. We propose work to help develop a molecular-level understanding of soil OC dynamics at the solid-solution interface. Our work will focus on the chemical aspects of two OC stabilization mechanisms, soil aggregate formation and sorption to fresh mineral surfaces. For the first of these, we propose to characterize the functional group chemistry associated with a series of soil aggregates of different sizes isolated from a prairie chronosequence. Our approach involves analysis of 'as received' or 'demineralized specimens using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy, photoacoustic Fourier-transform infrared spectroscopy (FTIR-PAS), and Fourier-transform Raman spectroscopy. 'Decarbonized' specimens will be used to obtain background spectra. In addition, the intact microstructures of these soil aggregates will be examined using focused-ion-beam scanning-electron microscopy (FIB-SEM). For the second soil OC stabilization mechanism, we will explore sorption of a series of model organic compounds by a Mollisol, an Ultisol, an Alfisol, and four representative high-specific-surface soil minerals. Our work at EMSL will involve analysis of the solid phase before and after treatment using FIB-SEM to explore the structure of the OC/mineral interface, FTIR-PAS and FT-Raman spectroscopies to identify the functional group chemistry of the OC in the various soils, and NMR spectroscopy to explore the binding properties of specific sorbed organic compounds. Because of the ability to use multiple spectroscopic and microscopic techniques to examine these two OC stabilization mechanisms we expect great progress to be made in understanding the roles of specific minerals and functional groups in the overall stability of soil OC. This information will then provide a mechanistic basis for informing models of C cycle dynamics, something which is currently lacking.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2010-10-01
End Date
2012-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members