Thursday, August 6, 2009 - 4:00 PM

OOS 44-8: Basic solid state NMR techniques in the biogeosciences

Caroline A. Masiello1, William C. Hockaday2, Morgan E. Gallagher2, Jeff A. Baldock3, Claire McSwiney4, G. Philip Robertson4, and Richard Norby5. (1) Rice University, Houston, TX, (2) Rice University, (3) CSIRO Land and Water, (4) Michigan State University, (5) Oak Ridge National Laboratory


Nuclear magnetic resonance has emerged as a powerful tool in the biogeosciences and is seeing increasing application in the ecological sciences. The major strength of NMR is the capability to characterize the chemistry of an entire carbon pool, in some cases without any chemical pretreatment.  New spectral deconvolution techniques make possible the reporting of concentrations of carbohydrate, lipid, lignin, amino acid, and charcoal, values which can be scaled up to ecosystem inventories of these biomolecules.  NMR spectra can also be used to calculate proxies important to understanding ecosystem processes, including a number of indices of decomposition.  Most universities in the U.S. have NMR facilities sufficient for environmental sample analyses, opening up the possibility that many ecologists and biogeochemists could benefit from this technique.
We will introduce both NMR applications and basic techniques, covering NMR terminology, the advantages and disadvantages of common NMR experiments (e.g. cross-polarization vs direct polarization), error in ecosystem-scale NMR experiments, and the importance of running the NMR-equivalent of standards (spin-counting experiments).

To demonstrate the use of basic NMR techniques, we will present analyses based on NMR spectra from two disturbed ecosystems:  an elevated CO2 field site and a crop system exposed to a gradient of N fertilization. The application of NMR to both these sites allows us to examine the impacts of ecosystem disturbance at a biochemical level.