Contrasting metal concentrations in selectively extracted suspended versus deposited sediments of the Fraser River Estuary

In order to assess the relative importance of Suspended Particulate Material (SPM) and deposited sediment as potential sources of trace metals to estuarine organisms, both SPM and deposited sediment were collected from three sites in the midestuarine region of the Fraser River Estuary over the course of one year. Selective chemical extractions were employed to assess differences in metal geochemical association between SPM and deposited sediment. Results indicate that SPM is an important metal-bearing vector in the estuary. SPM has significantly higher organic content (1--8 times) and metal levels (2--10 times) than deposited sediment and is also made up of smaller material (and therefore has a larger surface area to volume). The geochemical phase with which the metal associates also differs among the two sources and is metal specific. Such differences can have important implications in regards to metal exposure and uptake in suspension and deposit feeding organisms of the estuary.