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Title: USE OF GC/MS PYROLYSIS FOR ASSESSING CHANGES IN SOIL ORGANIC MATTER

Author
item STUCZYNSKI, TOMAS - INST. SOIL SCI- POLAND
item McCarty, Gregory
item Reeves Iii, James
item Wright, Robert

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: There is considerable interest in concepts of soil quality as they relate to sustainable productivity in agricultural ecosystems. Maintenance of soil quality requires maintenance of both the quantity and quality of soil organic matter because of its importance in establishing the structure, fertility and biological activity of soil. There is discussion in the literature, however, concerning the best method for assessing changes in the quality of soil organic matter. For example, measurements of total organic C and N of soil samples may give information on quantity of soil organic matter, but give little information on organic matter quality. Pyrolysis - gas chromatography - mass spectrometry (Py-GC-MS) techniques hold promise as rapid procedures for detecting changes in the organic matter composition of soils which contrast with the often laborious chemical methods commonly used for analyzing soil organic matter. To evaluate Py-GC-MS for this use, we characterized changes in the organic matter composition of bed-ash-amended soils by both chemical and pyrolytic analyses.

Technical Abstract: There is need for rapid methods of assessing changes in the quality of agricultural soils because of the need to monitor such changes under different land management practices. For example, the increasing interest in use of agricultural lands for application of coal combustion byproducts, such as fluidized bed ash, has led to concern that such use may be detrimental to the quality of soil organic matter. Pyrolysis - gas chromatography - mass spectrometry (Py-GC-MS) techniques hold promise as rapid procedures for detecting changes in the organic composition of soils. To evaluate Py-GC-MS for this use, we characterized changes in the organic matter composition of bed-ash-amended soils by both chemical and pyrolytic analyses. The chemical analysis of the soil samples had shown substantial degradation and loss of organic matter due to the ash amendments, and the pyrolytic analyses reflected these losses of organic matter by decreases in the total peak areas within the total ion chromatogram. Information on the changes in composition of soil organic matter was reflected by changes in peak area for pyrolytic products, and the identity of over 40 pyrolytic products were determined from their mass spectral data. This permitted identification of various pyrolytic signature products for the protein carbohydrate, and humic fractions of soil organic matter. The change in peak areas of these different signature products could be correlated with changes in the content of different constituents in the soil organic matter as measured by chemical analysis. The good agreement between classical chemical analysis and pyrolytic analysis indicates that Py-GC-MS can be used to monitor changes in soil organic matter.