How do colloid separation and sediment storage methods affect water-mobilizable colloids and phosphorus? An insight into dam reservoir sediment

Abstract Despite the significant role played by colloids in determining the fate of contaminants in aquatic systems, obtaining knowledge about the mobilizable colloids from bottom sediments of dam reservoirs has not yet received sufficient consideration. A major obstacle to understanding the role of colloids in aquatic systems is the limited comparability of results with the literature due to the vast number of methods practiced for colloid extraction/separation and the various sample storage conditions used for colloid extraction purposes. This work presents the effects of five colloid separation methods (namely direct filtration, successive filtrations, low-speed centrifugation and filtration, high-speed centrifugation and filtration, and successive centrifugations), combined with four sediment storage modes (wet, air-dried at 20 °C, oven-dried at 40 °C, freeze-dried), on the characteristics (mass, size distribution, composition) of water-mobilizable colloids from the bottom sediment of an eutrophic reservoir (Champsanglard, France). Special attention has been paid to phosphorus (P), an element that occupies a predominant place in the study of eutrophication process. Results showed that Champsanglard sediment contained a relatively high stock of water-mobilizable colloids (over 5.4 g/kgDW-Sed), along with the associated colloidal P constituted of approximately 4 % total sedimentary P and 81 %–93 % total water-mobilizable P (fraction