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Although mineral colloids are known to play a significant role in tmnsfon•ng organic matter in soils and sediments, there still are many gaps in our undemtanding of the mechanisms of organic-mineral interactions. In this study, we investigated the role of a major oxidemineral bimessite (a form of Mn(IV) oxide) in catalyzing the condensation reaction between sugars and amino acids, the Maillard reaction, for forming humic substances. The Maillard reaction is perceived to be a major pathway in natural humificafion. Using a suite of spectroscopic methods (including ESR, XANES, EXAFS and t3C NMR), our resultsshow that Mn(IV) oxide markedly accelerates the Maillard reaction between glucose and glycine at ranges of temperatures and pH typical of natural environments. These results demonstrate the importance of manganese oxide catalysis in the Maillard reaction, and its significance in the natural abiotic formation ofhumic substances.

[1] The global nitrogen cycle is of prime importance in natural ecosystems. However, the origin and nature of up to one-half of total soil N remains obscure despite all attempts at elucidation. Our data provide, for the first time, unequivocal evidence that the promoting action of Mn (IV) oxide on the Maillard reaction (sugar-amino acid condensation) under ambient conditions results in the abiotic formation of heterocyclic N compounds, which are often referred to as unknown nitrogen, and of amides which are apparently the dominant N moieties in nature. The information presented is of fundamental significance in understanding the role of mineral colloids in abiotic transformations of organic N moieties, the incorporation of N in the organic matrix of fossil fuels, and the global N cycle.

in whole soils using N-XANES spectroscopy. Can. J. Soil Sci. 84: 291-293. The nitrogen (N) cycle is second in importance only to the carbon (C) cycle in natural ecosystems. However, the origin and nature of approximately one-third of total soil N remains poorly understood. We used N-XANES (X-ray absorption near edge structure) spectroscopy, a sensitive, non-destructive synchrotron-based analytical technique, to determine the organic N structures in selected Gleysolic soils of Saskatchewan. Initial results indicate the presence of amide structures and heterocyclic N compounds, which are significant in understanding the transformation of organic N moieties in the soil, both in terms of sources of bio-available N and long-term storage.