The in situ analysis of organic matter in soils

Abstract

0C6.Schnitzer, M. 2001. The in situ analysis of organic matter in soils. Can. J. Soil Sci. 81: 249-254. Traditionally, studies on soil organic matter (SOM) begin with the extraction of SOM from soils, its fractionation into humic acid, fulvic acid, and humin, followed by de-ashing of each fraction. These are tedious, laborious and inefficient procedures that do not provide any chemical information on these materials. Instead, recently developed methods such as solid-state 13 C NMR and pyrolysis -field ionization mass spectrometry (Py-FIMS) can now be used for the in situ analysis of SOM in soils. These methods identify the major chemical components of SOM without extractions and fractionations, and yield valuable information on the main chemical structures in these materials. A better knowledge of the structural chemistry of SOM will help SOM chemists and other soil scientists to better understand the complex chemical and biochemical reactions that occur in soils, and will enable them to develop practices that will improve soil management and soil productivity.

Soil carbon: A measure of ecosystem response in a changing world?

“…Some soil C is freely accessible to soil microbes; other C is locked away inside aggregates or attached to minerals (Christensen 2001;Schnitzer 2001;Six et al 2002). For any given soil, therefore, the "quality" of organic matter may be as important as the amount of organic matter in influencing ecosystem function (Gregorich et al 1994;Monreal et al 1997).…”

Pyrolysis-molecular beam mass spectrometry to characterize soil organic matter composition in chemically isolated fractions from differing land uses

“…Two techniques increasingly used for SOM characterization are 13 C-NMR and analytical pyrolysis. These techniques are sometimes used in combination (e.g., Mao et al 2007), because 13 C-NMR provides information on diVerent functional groups of C in SOM while analytical pyrolysis yields data at the molecular scale (Schnitzer 2001). Pyrolysis gas chromatography mass spectrometry (py-GC/ MS, Saiz-Jimenez 1994) involves the separation of pyrolysis products into single components in the chromatographic column, with mass spectral data obtained for each component.…”

The Need of Analytical Techniques for In-Situ Study of Soil Organic Matter

“…These are tedious, laborious, time consuming and inefficient procedures that are not suitable for the analysis of large number of soil samples. Also, aside from the separation of organic from inorganic soil components, extractions do not provide any chemical information on the organic materials that have been removed [6]. The question invariably associated with soil organic matter (SOM) studies is whether to work with intact soil or to fractionate and if so, how.…”

“…Py-FIMS is more sensitive than 13 C NMR and gives reliable identification (e.g. purity) due to chromatography [6]. FTIR spectroscopic technique found to be suitable for the investigation of SOM chemical composition [12] and the possible molecular change induced by organic amendment [13].…”

“…FTIR spectroscopic technique found to be suitable for the investigation of SOM chemical composition [12] and the possible molecular change induced by organic amendment [13]. More precise information on how pesticides interact with SOM will provide a rational basis for their effective use and for minimizing undesirable side effects [6]. Modern spectroscopic methods are complementary and where possible effort should be made to utilize combinations of these methods to confirm and enhance data pertaining to the chemical structure of soil organic materials.…”