Flocculation of fine-grained suspended solids in the river continuum

A direct image analysis procedure is used to characterizse the number and size distribution of both primary and flocculated particles suspended in the water column of the Nith River. Sample locations in this southern Ontario river were determined according to the Strahler stream ordering system. Suspended solids concentration, water chemistry and river flow characteristics are examined to elucidate their effect on flocculation. In the Nith River, flocs represent a small proportion of the total number of particles transported but most (>90%) of the total volume of suspended solids. An increase in the floc median diameter (D50) and floc number was observed with decreasing suspended solids concentration. Variables such as DO, pH, SS, DOC and TDS influence floc size (D50) and floc number (floc-primary particle ratio). While floc number was variable, floc size distributions were similar irrespective of stream order. -from Authors