Can floes and water stable soil aggregates be differentiated within fluvial systems?

This paper uses a number of particle structural characterizations and behavioral assessments in an attempt to differentiate flocs formed in the water column from water stable soil aggregates formed in the terrestrial environment but transported to a river by overland flow. Using discrete populations of flocs and soil aggregates, the study successfully illustrated differences in floc structure (as defined by fractal dimension, sphericity measures, density, and porosity) and behavior (as defined by settling velocity). Flocs were generally found to be porous and irregular in shape: with high water content, low density, and low settling velocity, whereas, soil aggregates were found to be rounder, more compact (dense) with lower porosity and a higher settling velocity. The techniques were, however, inappropriate for differentiating the two particle forms from river storm sample; which are collected at the time when both particle forms are believed to be in suspension. Results suggest that aggregates, once within the river system, undergo a quick transformation into hybrid particles (aggregate-floc combinations) due to flocculation processes occurring on the river bed following quick settling or during suspended sediment transport. It is also possible that the aggregates undergo flocculation processes during overland flow (forming hybrid particles), prior to entering the river system. or never reach the river altogether ending up in long-term depositional areas in the terrestrial environment. Crown Copyright (C) 2004 Published by Elsevier B.V. All rights reserved.