Saturday, 15 July 2006

Characterization of Stable and Labile Soil Organic Matter Using a Novel Multiple Elemental Scanning Thermal Analysis.

Y. Ping Hsieh, Florida A&M Univ, Rm 115, Perry-Paige Building, FAMU, Tallahassee, FL 32307

Soil Organic Matter (SOM) is an important ingredient that maintains productivity and environmental quality of an ecosystem. SOM is also considered a potential sequester of the atmospheric C. We still know little about the chemical nature of solid SOM other than its bulk elemental composition, let alone relating the chemical nature of SOM to its ecological and environmental functions. A few analytical techniques, such as solid-state NMR and pyrolysis-mass spectrometry, do provide additional chemical information about a bulk SOM sample. Application of NMR and pyrolysis-mass spectrometry to SOM study, however, is limited due to the highly specialized and costly instrumentation and operations. Inadequacy of analytical technology is truly a gap existed that limits our understanding of SOM. Here, I report the development of a Multi-Elemental Scanning Thermal Analysis (MESTA) and its application to the study of labile and stable SOM. The MESTA heats up a sample from ambient to 800 oC in a given atmosphere and continually analyzes the C, N and S signal of the volatilized materials over the entire temperature range. The result is the scanning thermograms of C, N and S. The MESTA can differentiate organic and inorganic forms of C, N and S in a sample rapidly and sensitively without any pretreatment. It provides ample chemical signatures for the characterization and identification of SOM. I analyzed the SOM of several long-term agricultural experimental stations in the US that have been studied for fractions of stable and labile SOM. The MESTA C, N and S thermograms show chemical similarity and difference between the labile and stable SOM. The results of MESTA suggest the combination of chemical and physical protection mechanisms involved in the stabilization of SOM. This study also provides evidence to indicate that the stable SOM has much less black carbon content than previously suspected. Included in this report is also a discussion on the potential, limitation and direction of future development of the MESTA technology for SOM research.

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