Open Collections

Behaviour of some trace metals in sediments of the Fraser River delta-front, southwestern British Columbia

University of British Columbia

Co, Cu, Fe, Mn, Ni, Pb and Zn contents, both in total and partial extractions, have been determined for inter-tidal and foreslope surficial sediments of the Fraser River active delta-front. In conjunction with analysis of subsurface sediments and water and suspended sediment from the main channel, these data suggest controls on metal contents and distribution. An inverse relation between total metal contents and sand content of sediment is demonstrated in geographic distributions and correlation analysis of metal data. Relatively greater concentrations of metals in hydrous oxide phases and detrital minerals of the silt-plus-clay fraction account for this relationship. Trace metals in heavy minerals of the sand fraction partially negate the grain-size effect. Adsorbed metals are an insignificant quantity (excepting Mn) except in two samples from an area receiving effluent from the Iona Island sewage treatment plant. Variation of trace metal contents in short cores is generally related to transitions in sediment texture. Some metal may be mobilized and lost subsequent to burial, although this conclusion is contingent on the assumption that trace metal input to delta-front sediments is constant over time. One core collected near Iona Island, however, contains evidence that this assumption is not totally valid. Scavenging of Zn, and probably other trace metals, by newly-formed hydrous Fe (and possibly Mn) oxides takes place in brackish conditions within the main channel. In conjunction with physical processes which increase residence times of sediments in the estuarine portions of the river, this process accounts for removal of a sizeable fraction of dissolved metal. Desorption of trace metals occurs in the channel and in Georgia Strait, although probably to a somewhat lesser extent than the sorption process. In terms of metal contents and mechanisms of metal deposition, the Fraser delta-front is typical of nearshore sediments of low clay content. Trace metal sorption by various mechanisms, including that described here, accounts for retention of river-borne and waste metals in nearshore sediments.

Text

2010-02-16

For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.

http://hdl.handle.net/2429/20314

Geological Sciences

University of British Columbia

Graduate