A Mechanistic Model for Mud Flocculation in Freshwater Rivers

The transport and deposition of mud in rivers are key processes fluvial geomorphology biogeochemical cycles. Recent work indicates that flocculation might regulate by increasing settling velocities, but we lack a calibrated mechanistic model for freshwater rivers. Here, developed semi-empirical floc diameter velocity We compiled global dataset river suspended sediment concentration-depth profiles inverted them situ using the Rouse-Vanoni equation. On average, clay silt (diameters < 39 μm) flocculated with 1.8 mm s-1 130 μm. Among variables, Kolmogorov microscale has strongest positive correlation diameter, supporting idea turbulent shear limits size. Sediment Al/Si (a mineralogy proxy) negative velocity, indicating importance abundance composition flocculation. Floc increases greater organic matter concentrations, consistent driven particle collisions binding which is often concentrated mud. Relative charge density salinity correlates smaller finding reflect primary size distribution physical hosting matter. explains data within factor about two. Results highlight can impact fate particulate carbon, holding implications