ROLE OF SOLUBLE ORGANICS IN THE SOIL PROCESSES OF A PODZOL, CENTRAL CASCADES, WASHINGTON

The mobile organic compounds present in the soil solutions of a subalpine Podzol were studied. The molecular weight of the major fraction of the soluble organic compounds, designated as the mobile fulvic acid fraction, was determined to be in the range of 837–845 by gel filtration. Infrared analysis of these organic compounds indicated the presence of aromatic hydroxy carboxylic acids. There was a sharp decrease in the mobile fulvic acid fraction as the soil solutions passed through the IIB2hir and IIB2ir horizons. Those organics remaining in solution showed the presence of strongly chelated acid groups. Laboratory studies indicated that the IIB2ir horizon was highly effective in adsorption of the soluble organic compounds present in the soil solutions, while the IIB2hir was not. The removal of the organic compounds from the soil solution was due to the presence of reactive sesquioxides within the IIB2ir horizon. This suggests that the IIB2hir horizon is growing downward into the IIB2ir horizon. The results confirm earlier work on the importance of the B2hir horizon in delineating two distinct chemical compartments of a Podzol.