Multi-Phase Contaminant Transport in Sediment Beds

Contaminants can be introduced into water bodies in either dissolved or particulate form. Further reactions with natural suspended and bed sediments often produce considerable sediment contamination even when pollutants are originally emitted in dissolved form. Fine colloidal particulate matter is ubiquitous in streams, and often has a higher affinity for contaminants than larger streambed sediments. As a result, suspended sediments can carry a considerable fraction of the overall contaminant load. To understand the transport and ultimate fate of contaminants in aqueous systems, and particularly fluxes into and out of contaminated sediments, the potential for particulate-phase transport of contaminants must be considered. Contaminant behavior within sediment beds is highly dependent on the degree of association with suspended sediments, and the presence of suspended matter can favor either mobilization or immobilization of contaminants depending on the relative affinities of contaminants for suspended and bed sediments and the potential for suspended sediment deposition. Experimental results and model simulations will be used to illustrate a wide range of contaminant transport behavior and to elucidate the important processes that control multi-phase contaminant transport in sediment beds.