Isolation and characterization of naturally occurring organo-mineral complexes in some volcanic ash soils

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Abstract
Naturally occurring organo-mineral complex particles were separated from seven samples of volcanic ash soils after Satoh et al. (1972a,b). They were then divided into three kinds of complex particles (blackish silt-sized, brownish silt-sized, and clay-sized particles). The organic matter in the bfackish complex fractions showed a higher exothermic reaction at about 390-460°C, the clay complex fractions, a lower exothermic reaction at about 300°C, and the brownish complex fractions, both reactions. These exothermic reactions resembled in thermal nature of humic substances combined with inorganic materials such as Al- and Fe-ions. The soil samples from A horizons showed both the lower and higher exothermic reactions but those from B horizons showed only the lower one.