THE PREVALENCE OF FRESH-WATER FLOCCULATION IN COLD REGIONS - A CASE-STUDY FROM THE MACKENZIE RIVER DELTA, NORTHWEST-TERRITORIES, CANADA

The Mackenzie River Delta (MRD) is used as a case study for evaluating the extent to which flocculation may play an important role in the tr ansport of sediment and associated contaminants in arctic regions. Sam ples were collected for nondestructive analysis of particle/floc size, major ions, particulate organic carbon (POC), dissolved organic carbo n (DOC), bacterial counts, and suspended solid (SS) concentrations. On -site measurements were made for pH, conductivity, and temperature. Re sults indicate that the dominant form of sediment transport to and wit hin the MRD is flocs, and not traditionally sized primary particles. I t is shown that the flocs of the Mackenzie Delta are at times larger i n size than those in southern Ontario rivers that have been studied. T he sediment distributions were bimodal in nature; the particle-deficie nt zone potentially represented a preferential particle size for flocc ulation. Spatial and temporal trends in the grain-size distributions s uggest site-specific controlling factors of flocculation, such as sour ce area and sediment characteristics. It is hypothesized that water te mperature, suspended solid concentration, and bacteria are the importa nt factors in controlling flocculation within the Delta.