Dynamics of soil aggregate size in turbulent flow: Respective effect of soil type and suspended concentration

- Experiments on size evolution of soil aggregates within a turbulent flow are analyzed
- Soil aggregates are subject to abrasion within the controlled turbulent flow
- Increasing suspended concentration enhances abrasion resulting in smaller particles
- Badland aggregates reduce to smaller particles than those resulting from a brown soil

The fate of eroded soil particles impacts soil loss, river engineering and aquatic ecosystems. However, little is known about soil aggregate dynamics within the flow just after their detachment from the soil matrix. The relationship between particle size and turbulence has already been studied but few studies analysed the associated effect of particle concentration. The disaggregation/flocculation of three soils, two badland materials and a well developed calcareous brown soil, was studied by using a grid-stirred tank. An isotropic and homogeneous turbulence was generated to focus on the effects of suspended concentration on particle sizes. Increasing the suspended concentration in the range 1 − 10 g L− 1 leads to a decrease of the proportion of the medium size particles and of an increase of the proportion of the smallest particles, as a consequence to enhanced abrasion. The soil aggregates with the largest organic content had the highest strength but were still subject to disaggregation within the turbulent flow, the resulting particle size depending on the suspended concentration. This study demonstrates that soil aggregate characteristics are influenced by concentration, this behaviour being dependent upon the soil type.