SEDIMENT PATHWAYS IN A BRITISH-COLUMBIA FJORD AND THEIR RELATIONSHIP WITH PARTICLE-ASSOCIATED CONTAMINANTS

About 820 bottom grab samples were collected at regular intervals over Howe Sound, a British Columbia fjord. These were analyzed for their c omplete grain-size distributions in order to perform a sediment trend analysis. This is a technique whereby net sediment transport patterns are determined by assessing statistically the relative changes in grai n-size distributions along selected sample sequences. The analysis als o provides an understanding of the behaviour of the sedimentary enviro nment with respect to erosion, deposition or dynamic equilibrium. This information may be used to predict the build-up and/or dispersal of p article-associated contaminants. In Howe Sound, there are two pulp and paper mills which have been sources of dioxins and furans which have led to fisheries closures. In environments where total deposition is o ccurring (i.e., once deposited, a particle undergoes no further transp ort) contaminants are concentrated at locations relative to their sour ce. Where sediment in transport becomes so fine (i.e., fine silt and c lay) that size-sorting no longer occurs, contaminants have no preferre d location for their deposition; rather, contaminated particles have a n equal probability of deposition over the whole transport environment . In this study, the spatial distribution of existing contaminant data correlated extremely well with each of the transport environments as determined by the sediment trend analysis.