Assessment of Flocculation Kinetics of Cohesive Sediments from the Seine and Gironde Estuaries, France, through Laboratory and Field Studies

摘要

Cohesive suspended particles in a river aggregate into microfiocs with average diameters of 10-20 μm, which on their arrival in the estuary aggregate to macroflocs with average diameters of 100-200 μm. We performed a laboratory study on samples from the Seine estuary. The experiments show a more or less systematic behavior of floe size with drivers. Macrofloc size relates to turbulence, η, suspended particulate matter concentration (C), salinity (S), time (t), and mineral and biological composition of primary particles M. Generally, floe size increases with C, S, t, and η. We performed Eulerian field surveys of floe size and the same drivers on various sites in the Gironde estuary. Our field samples show an ambiguous behavior of floe size against salinity and suspended sediment concentration. Floe size does not seem to simply increase with C, S, t, and η, but floes grow and decay with time.